“It seems more than ever likely that blood-derived stem cells will replace marrow for many indications ... ”

J. Goldman, Bone Marrow Transplant 14:1, 1994

RECENT DATA from the International Bone Marrow Transplant Registry (IBMTR) showed that since 1990 the number of autologous transplants has exceeded that of allogeneic transplant. Furthermore, blood cells have been used more often than bone marrow (BM) in autologous transplants since 1993 (IBMTR newsletter July 1995). This trend mirrors that reported by the Europe Blood and Marrow Transplant Group (EBMT)1 and the Australian Bone Marrow Transplant Registry (ACCORD September 1995, The Newsletter from the Australian Coordinating Committee on Organ Registries and Donation). According to EBMT data, the number of autologous transplants in lymphoma and breast cancer in Europe has increased fivefold between 1990 and 1994. In this period the percentage of autologous transplants using blood cells increased from 15% to 75%.

The regular use of blood cells for transplant started only in the mid 1980s,2-6 although there were a few earlier sporadic case reports.7-10 This lagged behind the use of BM, the more intuitive source, for 15 years, and yet it is now the predominant cell source for hemopoietic rescue. For the early history of autologous blood cell transplant, readers are referred to an excellent chapter by two pioneers in this field, Korbling and Fliedner.11 

Blood progenitor cell mobilization in humans was initially noted during recovery after myelosuppressive chemotherapy.12-17 The ability of recombinant hematopoietic growth factors to mobilize blood cells, either alone18-20 or by enhancing chemotherapy mobilization,21-26 increased the use of mobilized blood cell for transplantation. Malignant contamination of mobilized blood cells received scant attention initially,9,27 but it has recently received more notice.28-32 The abundance of CD34+ cells in mobilized blood cells also lends itselves to gene therapy33,34 and ex vivo processing.35-38 However, little is known about the mechanism of mobilization of normal and malignant cells39,40 and the design of mobilization protocols remains empirical. Different approaches to study the quantitation of hematopoietic reconstitutive capacity in mobilized blood cells have been proposed,41-46 but little is known about the immune reconstitutive capacity.47-49 In the allogeneic setting, mobilized blood cells have also been used instead of BM.50 Umbilical cord or placental blood cells are another source of hematopoietic cells for transplantation51 but are outside the scope of this review. The emerging biology of mobilized blood cells and its increasing clinical use for hematopoietic rescue prompt this review.

The questions to be addressed in this review include the following: what are the molecular and humoral events leading to the mobilization of hematopoietic progenitors cells, how should the nature and quantity of the mobilized cells be measured, which are the effective blood cell mobilizers, when is the optimal time to obtain blood cells, how many blood progenitor cells are required for rapid reconstitution, what are the clinical and economical benefits of blood cell transplants, are allogeneic blood cells a feasible alternative to BM, and is there a place for mobilized blood cells in the treatment of nonmalignant diseases?

HISTORICAL PERSPECTIVE

Blood cell transplant is one of the few recently introduced treatment modalities where a reverse of the usual progression from animal studies to clinical trials occurs. Apart from a few initial animal studies,52-57 the major systematic developments in blood progenitor cell mobilization and transplantation occurred in the clinical arena.

Early experimental hematopoietic transplantation studies were mostly performed with murine BM rather than blood cells because of the inherent limitations to adequate and repeated sampling of blood from a small mammal-like mouse. In addition, steady-state blood cells were shown to be inferior to BM as a source of marrow repopulating cells.54 In humans progenitor cells are present in low quantities in blood during steady-state hematopoiesis postnatally,58-61 except for myeloproliferative states.62 The failure of engraftment in early reports of steady-state blood cell transplants in humans7,8 and clinical results of autologous transplantation using steady-state blood cells where hematopoietic reconstitution was no better than BM63,64 reinforced the emphasis on BM as the source of cells for hematopoietic rescue. These data overshadowed the more encouraging reports in larger animal models such as dogs53,57,65,66 and primates.55 Early hematopoietic recovery after chemotherapy was reported in a patient who received peripheral blood (PB) collected by leukaphereses from an identical twin.67 Another report of successful use of syngeneic blood cells for immune reconstitution appeared in 1972.68 Despite these studies the use of mobilized blood cells for transplantation was initially viewed with a healthy scepticism because mobilized blood cells were considered no different from steady-state blood cells.

Several developments contributed to a shift from steady-state to mobilized blood cells.

The increase of circulating progenitor cells following the administration of dextran sulfate to dogs and of endotoxin and adrenocorticotrophin to normal subjects, and after strenuous physical exercise was described as early as the 1970s.69,70 There was only a twofold to fourfold increase and the levels returned to normal within hours, so such transient mobilizations did not offer much scope for blood progenitor cell harvesting. Nonetheless, these observations indicated that progenitor cells could be mobilized to blood.

An improved colony-forming unit granulocyte-macrophage (CFU-GM) assay provided more accurate information on progenitor cell mobilization. A plating concentration of 1 to 2 × 105 PB mononuclear cells/mL was more optimal for the growth of PB progenitors than the 5 to 10 × 105/mL previously used because it takes into account the effect of monocytes in vitro.71 

The feasibility of progenitor cell harvesting by leukapheresis was first demonstrated in normal subjects in 1980.72 Then successive reports of clinical studies showing the phenomenon of blood progenitor cell mobilization and the hematopoietic reconstitution advantage of mobilized blood cells2,4,6,15,17,20-26,73-76 followed. Systematic experimental animal studies with mobilized blood cells have since confirmed findings of clinical studies.77-79 Currently almost all blood cell transplants other than cord blood transplants are performed with mobilized blood cells.

THE PHENOMENON OF HEMATOPOIETIC PROGENITOR CELL MOBILIZATION

Hematopoietic chimerism after liver transplantation suggests that extramedullary transplantable progenitor cells exist,80 but whether they contribute to the mobilizable pool is not known. The general belief is that mobilized blood progenitor cells originate from BM. This postulate predicts a sequence of critical events during progenitor cell mobilization: firstly, modulation of the progenitor cell:BM stroma interaction, then the directed migration toward marrow sinuses and eventually egress through the basement membrane and the endothelial layer.

The localization of hematopoiesis to the BM involves developmentally regulated adhesive interactions between primitive hematopoietic cells and the stromal-cell–mediated hematopoietic microenvironment.81-88 This and the broad range of agents that can result in transient increases in blood progenitor cells89 led many investigators to propose that mobilization involves a perturbation of the adhesive interactions with stromal elements which, under steady-state conditions, are responsible for the physiologic retention of primitive hematopoietic progenitor cells in the BM.40,90-92 Primitive hematopoietic progenitor cells exhibit a wide range of cell adhesion molecules (CAMs) including members of the integrin, selectin, immunoglobulin superfamily and CD44 families of adhesion molecules. Ligands for many of these CAMs are expressed by BM stromal cells.82,85,86 

The role and relative contribution of the many individual CAM-ligand pairs in the homing, lodgement, and retention of primitive hematopoietic progenitor cells within the BM remain largely unknown. However, recent studies have suggested an important contribution is made by the β-1-integrin VLA-4 whose two ligands, fibronectin and VCAM-1, are constitutively expressed by the marrow stroma.87,88,93-96 Notably, perturbation of VLA-4 function after administration of function-blocking anti–VLA-4 antibody to nonhuman primates was found to induce mobilization of hematopoietic progenitor cells.90 In the same study the investigators showed that antibody to β-2-integrin (CD18), which is also expressed by hematopoietic progenitor cells, failed to induce mobilization (at least over the time course measured), further emphasising the importance of the role of VLA-4 in restricting hematopoietic progenitor cells to the BM under steady-state conditions.

Evidence is now emerging that CAM may be involved in the process of mobilization. Several studies have shown that, relative to their counterparts in steady-state BM, CD34+ cells mobilized by a variety of regimens and cytokines consistently demonstrate reduced expression of certain CAMs, in particular VLA-4, LFA-1, and LFA-3, whereas others such as CD31, CD44, and CD62L remain unchanged.40,91,97 It is also important to note that functional changes in CAMs may occur without changes in surface expression. In common with mature leukocytes, CD34+ cells in steady-state BM express the β-1 integrins VLA-4 and VLA-5 in an inactive or low-affinity state.98,99 After treatment with a range of cytokines including interleukin-3 (IL-3), GM colony-stimulating factor (GM-CSF ), and stem cell factor (SCF ), CD34+ cells exhibit transient (within 10 to 15 minutes) dose-dependent increases in VLA-4 and VLA-5 ligand binding properties followed by a return to basal activation states.99-101 Whether such functional changes occur with other CAMs such as CD44,102 which do not exhibit significant changes in expression on mobilized progenitor cells, remains to be determined. Nonetheless, these data suggest that mobilization of hematopoietic progenitor cells may, at least in part, result from cytokine-induced changes in integrin function on CD34+ cells that facilitate their egress from the BM. However, it should be noted that the rapidity and transience of the change in adhesive properties observed in vitro after treatment of hematopoietic progenitor cells with cytokines are not in accord with the kinetic of hematopoietic progenitor cell release in vivo following administration of cytokines, which in the case of G-CSF, for example, occurs after several days.20 

One of the most intriguing observations to emerge from the flow cytometric analysis of CD34+ cells in mobilized PB is the markedly reduced expression of c-kit on these cells compared with the levels on steady-state BM and PB CD34+ cells.39,40,91 Importantly, this occurred in all six mobilization protocols studied40 and the reduced expression is inversely correlated with progenitor cell yield (Fig 1). The mechanism responsible for this reduction in c-kit expression remains unknown, although the change in c-kit antigen density occurs in the BM before the egress of hematopoietic progenitor cells into the circulation.40 However, the interaction between c-kit and its ligand SCF, which exists both as a soluble form and as a membrane-bound form found on stroma cells, may be a paradigm of how cytokines, CAM, and marrow stroma influence the progenitor cell function. Cynshi et al103 have previously shown that in mice with Steel or WW mutations (that lack the ability to produce soluble SCF or have a defective c-kit receptor, respectively), G-CSF is far less efficient at mobilizing blood progenitor cells than in wild-type mice. Thus, mobilization of blood progenitor cells in response to G-CSF may in fact be a G-CSF + (endogenous) SCF response.

Fig. 1.

The correlation between c-kit downregulation on mobilized CD34+ cells and CD34+ cell yield (×106/kg BW) of a 10-L apheresis performed on the same day in the authors' institution. Forty-two specimens from six mobilization protocols were analyzed. (□), Patients who received cyclophosphamide 4 to 7 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. (✙), Patients who received IL-3 and GM-CSF at 5 μg/kg/d subcutaneously and had blood cells harvested during GM-CSF administration. (⊞), Chemotherapy naive patients who received G-CSF at 12 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7. (○, ▵), Patients who received myelosuppressive chemotherapy and G-CSF or GM-CSF and had blood cells harvested during recovery from myelosuppression. (⊕), Chemotherapy naive patient who received G-CSF at 12 μg/kg subcutaneously daily and SCF at 5 to 15 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7 of G-CSF administration. The correlation between c-kit downregulation and CD34+ cell yield per apheresis is significant at P << .005.

Fig. 1.

The correlation between c-kit downregulation on mobilized CD34+ cells and CD34+ cell yield (×106/kg BW) of a 10-L apheresis performed on the same day in the authors' institution. Forty-two specimens from six mobilization protocols were analyzed. (□), Patients who received cyclophosphamide 4 to 7 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. (✙), Patients who received IL-3 and GM-CSF at 5 μg/kg/d subcutaneously and had blood cells harvested during GM-CSF administration. (⊞), Chemotherapy naive patients who received G-CSF at 12 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7. (○, ▵), Patients who received myelosuppressive chemotherapy and G-CSF or GM-CSF and had blood cells harvested during recovery from myelosuppression. (⊕), Chemotherapy naive patient who received G-CSF at 12 μg/kg subcutaneously daily and SCF at 5 to 15 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7 of G-CSF administration. The correlation between c-kit downregulation and CD34+ cell yield per apheresis is significant at P << .005.

Primitive progenitor cells were capable of shape change and motility in vitro.104 However, factors modulating directed migration have not been defined. Furthermore, proteolytic activity possibly involving metalloproteases is presumably required for egress through the basement membrane. Although neutrophil motility and tissue migration have been well studied,105 no data are available on whether the same biochemical pathways and cytoskeleton are present or used in mobilized progenitor cells.

Although most studies investigating mechanisms of mobilization of hematopoietic progenitor cells have focused on changes in the properties of these cells, little work has been done to investigate the potential contributions of the marrow stroma to this phenomenon. Damage to the stroma from previous exposure to chemotherapy may, in part, explain the quantitatively poor mobilization frequently seen in some patients17,106 and also in murine models.78 Similarly, the increased stromal cell proliferation seen in patients receiving IL-3 may result in enhanced retention of hematopoietic progenitor cells106,107 and may therefore explain the relatively poor efficacy of such protocols.

Understanding the mechanism of mobilization may contribute to the development of more predictable and efficacious mobilization protocols. In particular, elucidation of the immediate molecular and biochemical events leading to dehesion and migration may allow us to mobilize progenitor cells more directly. Changes in integrin and selectin function have also been described in association with tumor cell trafficking108; hence, it may be possible to develop protocols that favor normal hematopoietic cell mobilization and reduce the risk of malignant contamination.

MOBILIZATION PROTOCOLS

Myelosuppressive Chemotherapy

Myelosuppressive chemotherapy was the first clinically useful blood progenitor cell mobilization protocol.3,4,15 During the recovery phase after myelosuppressive chemotherapy, 50-fold or more increases in PB CFU-GM occur. The extent of this increase seems to be proportional to the severity and duration of the cytopenia.3,16,25 High-dose cyclophosphamide is the most commonly reported protocol4,17,109,110 because it is active against most tumors and can be given justifiably even in diseases when conventional treatment is not sufficiently myelosuppressive.

The main limitations of chemotherapy mobilization are neutropenic sepsis, bleeding diathesis, and the unpredictability of the timing of apheresis. In a series of 60 patients receiving high-dose cyclophosphamide, hospitalization because of sepsis occurred in 44% to 100%, platelet transfusion in 18%, and death in 3% of the patients.109 Similar toxicity was reported by Kotasek et al110 and Jagannath et al.111 With the advent of hematopoietic growth factors it is no longer necessary to use myelosuppressive chemotherapy alone for mobilization.

Myelosuppressive Chemotherapy + Hematopoietic Growth Factors

Numerous phase II studies have suggested most strongly that the addition of hematopoietic growth factors such as G-CSF and GM-CSF to myelosuppressive chemotherapy enhances mobilization while reducing myelotoxicity.22,24,25,112-114 

G-CSF.Schwartzberg26 described the effect of G-CSF in enhancing chemotherapy mobilization in a study involving 382 patients with various malignancies. They received either 4 g/m2 cyclophosphamide (HDC), HDC and 600 mg/m2 etoposide (HDCE), HDCE with G-CSF (6 μg/kg/d), or HDCE and 105 mg/m2 cisplatin (HDCEP) with G-CSF. Both dose escalation and addition of G-CSF were associated with higher CD34+ cell yield. The addition of G-CSF led to a doubling of mononuclear cell yield, but a fourfold to sixfold increase in CD34+ cell yield from 1.4 × 106/kg in HDCE to 6.6 × 106/kg in HDCE + G-CSF and 8.6 × 106/kg in HDCEP + G-CSF. Over half of patients in the last group achieved 20 × 104 CFU-GM/kg after one leukapheresis whereas only 40% of the HDC group reached this target after six leukaphereses. In an earlier study Schwartzberg et al25 reported a mean of 3 days shortening of neutropenia and a reduction of hospitalization from 33% in the chemotherapy-alone group to 8% to 20% in the chemotherapy + G-CSF group.

The dose of G-CSF used with chemotherapy is in the range of 3 to 6 μg/kg/d,24,25 usually started on the day after chemotherapy and continued until the completion of leukapheresis. It has become an increasingly common practice to use a 300-μg ampoule of G-CSF per day instead of adhering to a strict per-kilogram formula.24,115 The daily G-CSF dose is lower than the 10 to 24 μg/kg/d when used alone,20,116 but the duration required is longer at 8 to 12 days compared with 4 to 6 days, so there is no cost saving. However, a recent report described 42 patients who received 3 to 4 g/m2-cyclophosphamide and 300 μg G-CSF from day +5.115 Thirty-eight patients proceeded to transplant receiving a median 4.3 × 106 CD34+ cells/kg and achieved the expected rapid neutrophil and platelet reconstitution. Hence, a delayed start of G-CSF may reduce cost without loss of efficacy, as described with GM-CSF.

GM-CSF and IL-3.GM-CSF was the first cytokine shown to enhance blood progenitor cell mobilization by chemotherapy.112 Although its efficacy seems comparable with G-CSF, it is now less commonly used than G-CSF, probably because of its side effects such as fever, hypoxemia, and first-dose effect. The dose is usually 5 μg/kg/d or 250 μg/m2/d subcutaneously. Because higher doses are associated with more side effects they are rarely used. Starting GM-CSF 5 days after chemotherapy is just as effective as starting on day 1, but starting on 7 or 10 days after chemotherapy may be less effective.

A protocol of sequential IL-3 and GM-CSF after chemotherapy gave a higher yield of progenitor cells compared with GM-CSF following chemotherapy or chemotherapy alone.113 Both IL-3 (days 1 to 5) and GM-CSF (days 6 to 14) were used at 250 μg/m2/d.

PIXY321.Preliminary data suggest that PIXY321 (GM-CSF/IL-3 fusion protein) at 500 to 1,000 μg/m2 after chemotherapy also enhances mobilization. An ongoing randomized study comparing PIXY321 (750 μg/m2) with G-CSF (5 μg/kg/d), GM-CSF (5 μg/kg/d), or G- + GM-CSF (2.5 μg/kg/d) administered after cyclophosphamide 3 g/m2 suggests that more CFU-GM and megakaryocytic progenitors are mobilized by PIXY321 than by other cytokines,117 although the differences are no more than onefold to twofold. Another study suggests that PIXY321 enhancement of cyclophosphamide mobilization is similar to GM-CSF.118 

Many different myelosuppressive chemotherapy protocols have been used in conjunction with cytokines for mobilization. None stand out, so it is more important that mobilization be incorporated as part of therapy. Another emerging impression is that adequate mobilization may occur even with chemotherapy regimens that are only mildly myelotoxic, such as cyclophosphamide at 1-2 g/m2.114 

Hematopoietic Growth Factors Alone

G-CSF.G-CSF stimulates neutrophil granulopoiesis in a dose-dependent manner and increases the level of PB progenitor cells in cancer patients.18 Dose escalation beyond 10 to 16 μg/kg/d does not appear to further enhance mobilization. The minimum dose is yet to be defined. The level of PB progenitor cells increases 40- to 80-fold after 4 to 5 days of treatment.20,119 On cessation of G-CSF progenitor cell levels return to baseline values within 4 to 6 days.120 Syngeneic transplants in mice showed that G-CSF mobilized blood cells have substantial numbers of primitive stem cells capable of long-term hematopoietic reconstitution and repopulating the thymus.77 In humans, PB CD34+ cells mobilized with G-CSF contain subsets of CD38, HLA-DR, and CD33 cells and are capable of generating CFU-GM in liquid culture for 3 weeks or more.39 

Sheridan et al20 were the first to report the hematopoietic reconstitutive capacity of G-CSF–mobilized blood cells. Seventeen patients with poor-prognosis nonmyeloid malignancy received G-CSF at 12 μg/kg/d subcutaneously for 6 days and had leukapheresis performed on days 5, 6, and 7. The CFU-GM levels shared a median increase of 58-fold. CFU-GM yield was highest on day 5, with a mean total yield of 33 ± 6 × 104/kg body weight (BW), range 0.8 to 90 × 104/kg BW. Fourteen patients were given both the cryopreserved blood cells and autologous BM cryopreserved before mobilization. Compared to two historical groups transplanted with autologous BM with and without posttransplant G-CSF, the most significant finding was a more rapid platelet reconstitution with a reduction in platelet transfusion requirement.

Bensinger et al121 described 12 patients administered G-CSF at 16 μg/kg/d subcutaneously. The number of PB CD34+ cells increased 10-fold over baseline values, peaking at about day 5 of G-CSF therapy. Neutrophil and platelet reconstitution were both more rapid than with historical control patients who received autologous BM with or without posttransplant cytokines.

Eighty-five patients with relapsed Hodgkin's disease received autologous hematopoietic rescue with steady-state or G-CSF–mobilized blood cells, with or without BM.122 They were assigned to ‘no growth factor during mobilization or following infusion’ (group 1, n = 32), ‘GM-CSF following infusion’ (group 2, n = 21), ‘G-CSF following infusion’ (group 3, n = 7), or ‘G-CSF for mobilization and following infusion’ (group 4, n = 20). The CFU-GM yield and the rate of platelet and neutrophil reconstitution were highest in group 4. This study shows clearly the advantage of G-CSF–mobilized blood cells over steady-state blood cells and BM.

Basser et al123 described G-CSF mobilization in patients who had not received previous chemotherapy. Three leukaphereses yielded 115 × 104 CFU-GM/kg BW, range 23 to 274 × 104/kg BW, much higher than that in patients who had previous chemotherapy.20 Notably the progenitor cell yield, though higher, still showed a 10-fold variation.123 

In allogeneic blood cell transplantation G-CSF was used for mobilization in almost all reported cases and the apheresis target is generally set at ≥3 × 106 CD34+ cells/kg BW. The most common dose of G-CSF used is 10 μg/kg BW/d subcutaneously and most centers perform leukapheresis after 4 to 5 days of G-CSF.124-128 A dose-dependent CD34+ cell mobilization by G-CSF between 3 and 10 μg/kg BW/d has been observed,129 but further data suggest that higher doses of G-CSF, such as 10 to 12 μg/kg twice daily, give a higher yield than once daily.130 One leukapheresis is often sufficient, but there were donors from whom low numbers of CD34+ cells were collected.

The side effects of G-CSF are few. Bone pain and asymptomatic elevation of serum alkaline phosphatase and GGT are the most common side effects. The latter does not require treatment while analgesia is usually adequate for the former. Two forms of G-CSF are currently available. Filgrastim is the nonglycosylated form from Escherichia coli, while lenograstim is the glycosylated form from Chinese hamster ovary (CHO) cells. Lenograstim was shown to be more active than filgrastim on a weight-by-weight basis in BM assay in vitro, although they were equivalent by immunologic assays.131 In postchemotherapy neutropenia, lenograstim at 150 μg/m2 was claimed to be as effective as filgrastim at 5 μg/kg.132 Very few comparisons in mobilization are available, although a recent abstract suggested that lenograstim at 10 μg/kg/d gives a better mobilization of CD34+ cells and CFU-GM than filgrastim.133 This is based on a cross-over study in 32 healthy male volunteers with a minimum 4 weeks' wash-out period. The PB progenitor cell levels were 30% higher during lenograstim administration. Whether the formulation of G-CSF influences its mobilization capacity remains an open question. Nonetheless, the hematopoietic reconstitutive capacity of G-CSF–mobilized blood cells is beyond doubt.

G-CSF/SCF.SCF, ligand to c-kit, has only a modest effect on hematopoietic progenitor cell proliferation in vitro but exerts potent synergistic effects with direct-acting hematopoietic growth factors. In baboons a 10- to 100-fold increase in CD34+ cells, CFU-GM, and burst-forming units-erythroid (BFU-E) as well as detectable levels of multilineage progenitor cells (CFU-Mix) and high proliferative potential progenitor cells (HPP-CFC) occurred in blood after 200 μg/kg/d of SCF administered either subcutaneously or intravenously.134 These SCF-mobilized blood cells rescued lethally irradiated baboons.135 Its mobilization effect on humans when used alone has not been published, although it has been reported in meetings that patients rescued with SCF-mobilized blood cells showed delayed engraftment and required back-up BM.

The clinical use of SCF + G-CSF for mobilization followed the demonstration of synergy of such a combination in experimental animals. Administration of low-dose SCF + G-CSF to mice and baboons mobilized greater numbers of progenitor cells compared with G-CSF alone.136,137 Genetic marking showed that a higher proportion of mice transplanted with SCF + G-CSF mobilized blood cells remain stably reconstituted by donor cells, compared with mice transplanted with blood cells mobilized by G-CSF alone.79 

In patients with poor-prognosis stage II/III breast cancer with no previous chemotherapy, concomitant SCF enhanced mobilization by G-CSF.138 In eight patients who received SCF 10 μg/kg/d concomitantly with G-CSF, both the mean PB CFU-GM level on day 6 and the leukapheresis yield were 70% higher than the cohort receiving G-CSF alone.

The same group suggested that mobilization with SCF/G-CSF is schedule dependent. In patients receiving G-CSF alone, the level of PB CFU-GM returned to normal within days of G-CSF cessation. In patients receiving SCF + G-CSF, PB CFU-GM remained elevated 5 days later at 8,816/mL. In eight patients receiving 3 days of SCF before 7 days of combined SCF + G-CSF the levels 5 days after cessation of study drugs were even higher, at 22,338/mL.139 Hence, further studies on the scheduling of the SCF/G-CSF may have a great potential for harvesting extremely high numbers of progenitor cells.

The synergism between SCF and G-CSF was also seen in patients who had previous chemotherapy.140 One hundred eleven women with stage II-IV breast cancer received either G-CSF 10 μg/kg/d alone or with SCF at 10-25 μg/kg/d administered concomitantly. The CD34+ cell yield showed a significant SCF dose response. Patients receiving 20 or 25 μg SCF/kg/d showed a 2.5- and 4-fold higher yield (8.1 and 13.6 × 106/kg BW) than those receiving G-CSF alone or with 10 μg SCF/kg/d (3.2 and 2.6 × 106/kg BW).

SCF administration has produced an anaphylactic type reaction in occasional subjects, so current protocols are usually administered under H-1 and H-2 blockade and α and β adrenergic cover. This may result from mast cell activation and may limit its use in atopic subjects.

GM-CSF.In the same year that Duhrsen et al reported G-CSF's blood progenitor cell mobilization effect, Socinski et al19 described an 18-fold increase in PB CFU-GM after 3 to 7 days of GM-CSF at 4 to 64 μg/kg/d as a continuous intravenous infusion. Later reports described a more modest fourfold to ninefold increase in PB CFU-GM.141-143 Haas et al141 transplanted 6 patients with GM-CSF–mobilized blood cells. Of the 5 evaluable patients, the median time to reach 0.5 × 109 neutrophils/L and 20 × 109 platelets/L were 28.5 and 39 days, respectively. This engraftment rate was similar to that following BM rescue, not surprising in view of the low CFU-GM dose of <1 × 104/kg BW.141 Peters et al144 also suggested that GM-CSF is less efficacious than G-CSF in mobilization. Although GM-CSF has been approved for mobilization in the United States, G-CSF is used more frequently.

IL-3.IL-3 has a proliferative effect on primitive hematopoietic cells in vitro145 and gives rise to a moderate increase in leukocyte and platelet counts on in vivo administration,146 but has little activity in mobilization.147 In rhesus monkeys IL-3 (33 μg/kg/d subcutaneously for 11 to 14 days) followed by GM-CSF (5.5 μg/kg/d for 5 to 14 days) was compared with either GM-CSF or IL-3 alone.148 There was a 63-fold increase in PB CFU-GM over steady-state levels in the sequential protocol compared with 12- and 14-fold increases, respectively, in the other protocols. Unfortunately, side effects limit the dose of IL-3 in humans to 5 to 10 μg/kg/d. In humans a phase I/II study of blood progenitor cell mobilization with IL-3/GM-CSF (at 5 μg/kg/d each) showed only a modest yield of CFU-GM 28 ± 8 × 104/kg BW and 1.8 ± 0.6 × 106 CD34+ cells/kg BW.106 IL-3 has also been combined with G-CSF but it is not clear how much it improves mobilization with the latter. There is no evidence that cytokines active on primitive cells such as IL-3 and SCF can mobilize more progenitor cells in patients with a limited hematopoietic reserve or that they can mobilize a different spectrum of hematopoietic progenitors.

PIXY321.Ghielmini et al149 reported a phase I/II study of PIXY321 administered daily at doses of 500 to 1,000 μg/m2/d subcutaneously over 14 days to nine patients before chemotherapy. A modest biphasic increase in neutrophil counts occurred, accompanied by an increased BM cellularity. There was a modest 3- to 10-fold increase in the number of myeloid and erythroid colony-forming cells in blood. The mobilized cells were not able to sustain hematopoiesis in long-term liquid culture to the same degree as BM.

Flt3 ligand alone or with G-CSF/GM-CSF.Flt3 ligand has been shown to be a costimulatory factor for the proliferation of primitive lymphohematopoietic progenitors in vitro and is able to protect mice from lethal irradiation. Brasel et al150 reported preliminary data from a murine study comparing the progenitor cell mobilization effect of Flt3 ligand at 10 μg/d, G-CSF at 2 μg/d, and GM-CSF at 1 μg/d, administered intraperitoneally for 9 days. Flt3 ligand produced an 83-fold increase of PB CFU-GM after 9 days but Flt3 ligand + G-CSF gave a 2,193-fold increase. Synergism with GM-CSF was present but minimal. BFU-E and CFU-Mix were also mobilized. The length of administration required and the synergistic effect with G-CSF both suggest that other intermediary cytokines are involved.

Macrophage inflammatory protein-1α (MIP-1α).MIP-1α inhibits primitive stem cell proliferation and has been investigated as a myeloprotective agent during chemotherapy. Murine studies with BB10010, a genetically engineered variant of human MIP-1α showed that a single subcutaneous injection caused a twofold increase in circulating CFU-S and cells with marrow repopulating ability (MRA). Although G-CSF increased the circulating levels of CFU-S and MRA 20- to 30-fold, a single injection of BB10010 after 2 days of G-CSF increased the levels 30- and 100-fold, respectively.151 No published data on human subjects are available.

Other Agents

Human erythropoietin and IL-6 have both been shown to have very modest effect in progenitor cell mobilization.152,153 IL-1 at 1 μg produced a 30-fold increase in CFU-GM and a 10-fold increase in CFU-S12 in PB after 4 to 8 hours, and these murine PB cells have long-term hematopoietic reconstitutive capacity.154 Unfortunately IL-1 is unlikely to be used in humans because of its toxicity even at very low doses. The same group also demonstrated that 30 μg of IL-8 injected intraperitoneally in Balb/C mice produced a 17-fold increase in CFU-GM after 15 minutes, but the level of CFU-GM returned to normal after 60 minutes. Transplant studies showed that IL-8–mobilized cells had lymphohematopoietic repopulating ability.155 The immediate time course of mobilization is of major interest because it suggests that IL-8 may modulate the immediate molecular and biochemical events leading to mobilization. A 20-fold increase in PB CFU-GM was described 5 days after cessation of 5 days of IL-2 at 3 × 106 μg/m2/d, but whether that is a result of BM recovery is not known.156 The mobilization potential of thrombopoietin has not been reported.

FACTORS AFFECTING YIELD

In progenitor cell mobilization after myelosuppressive chemotherapy, the dose of chemotherapy, the severity of myelosuppression, and the rate of recovery of leukocyte count all correlate positively with progenitor cell yield.16,17,26,109,110 The addition of G-CSF or GM-CSF to myelosuppressive chemotherapy appears to enhance progenitor cell yield,26,157,158 although no phase III studies have been reported.

In all categories of mobilization protocols described above the amount of previous chemoradiotherapy and the degree of BM involvement are significant determinants of progenitor cell yield. This may be measured as the number of cycles of chemotherapy,24,158,159 the duration of previous chemotherapy,17,160 previous wide-field radiotherapy,113,161 the interval between previous chemotherapy and mobilisation,162 exposure to stem cell toxic drugs such as BCNU and melphalan,161 and the higher yields in allogeneic donors.

These variables are probably all indicators of hematopoietic reserve. Therefore, it is noteworthy that Fruehauf et al163 reported that PB CD34+ cells and colony-forming cells during steady-state hematopoiesis are measures of a patient's mobilizable pool after G-CSF and chemotherapy. Their analysis of 15 patients showed that a level of ≥0.4 × 106 PB CD34+ cells/L at steady-state predicts with 95% probability that 2.5 × 106 CD34+ cells/kg would be collected with six leukaphereses. The correlation between BM CD34+ is much less significant and the investigators suggested that there are mature CD34low cells in BM that do not circulate. However, several major technical problems limit the use of BM progenitor cell levels as an indicator of hematopoietic reserve.

The level of BM progenitor cells can only be expressed as a percentage of total cells in the aspirate, but the degree of blood dilution in the aspirate varies significantly according to the technique used and the volume aspirated.164 Hence, the levels of BM progenitor cells in a BM aspirate which includes PB as well as BM cells may not be a real estimate of the true incidence of progenitor cells in BM. The cellularity of BM is also different in different parts of the body; eg, sternal aspirates are usually more cellular than iliac spine aspirates,165,166 and the volume of total body BM remains an estimate.167 Furthermore, these problems are aggravated in disease states.164,167 These variables make it very difficult to correlate the incidence of progenitor cells in a BM aspirate with the number of progenitor cells in the body.165 In contrast, if there is an equilibrium between the progenitor pools in PB and BM then the level of steady-state PB progenitor cells may be a more accurate indicator of hematopoietic reserve than the incidence of progenitor cells in a BM aspirate. Nothdurft et al65 found that the number of CFU-GM infused correlated significantly with hematopoietic reconstitutive capacity in beagle dogs transplanted with steady-state syngeneic or autologous PB. Hence, steady-state PB progenitor levels may be a reliable, albeit indirect, indicator of pluripotent stem cells. However, the stringency required to measure low levels of progenitor cells in steady-state hematopoiesis by flow cytometry or clonogenic assays mean that only laboratories with well-standardized assays could use this index.

Sequential progenitor cell mobilization in the same patient provides a unique setting for analyzing the efficacy of mobilization uncomplicated by patient, disease, and prior treatment variables. In a study of patients undergoing two mobilizations within 3 months the progenitor cell yields were the same when the same dose of chemotherapy was used twice, higher when 7 g/m2 cyclophosphamide was used compared with 4 g/m2, and also higher when chemotherapy + GM-CSF was used instead of a IL-3 + GM-CSF combination.168 

Experimental data suggest that chemoradiotherapy damages stem cells169,170 and progressive delay in recovery after successive chemotherapy cycles is an experience common to most hemato-oncologists. The importance of hematopoietic injury may be indicated by the rate of posttransplant recovery, which is significantly affected by the amount of chemotherapy received before transplant conditioning.171 The importance of hematopoietic reserve in progenitor cell mobilization underscores how critical it is to incorporate mobilization as part of planned treatment rather than as part of salvage for resistant disease.172,173 This is particularly relevant given that hematopoietic growth factors are used increasingly as an adjunct to chemotherapy treatment because this may result in earlier and more severe stem cell exhaustion.173 

Figure 2 shows the progenitor cell yields from different mobilization protocols observed in the authors' institution over the last 10 years. Stringent in-house quality control measures assured the reliability of CFU-GM and CD34+ cell measurements throughout the period. Patient recruitment into these groups was not randomized so the groups were not strictly comparable. However, the data indicate strongly that the dose of mobilizing chemotherapy, the synergism between chemotherapy and G-CSF/GM-CSF, the synergism between G-CSF and SCF, and a healthy BM are all predictors of a high progenitor cell yield.

Fig. 2.

The CFU-GM yield of different mobilization protocols used in the authors' institution. ‘3-4gm Cy’ denotes patients who received cyclophosphamide 3 to 4 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. ‘7gm Cy’ denotes patients who received cyclophosphamide 7 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. ‘G-CSF, pretreated’ denotes patients who received G-CSF at 12 μg/kg subcutaneously and had blood cells harvested on days 5, 6, and 7. ‘Chemo + G-CSF’ and ‘Chemo + GM-CSF’ denote patients who received myelosuppressive chemotherapy and G-CSF or GM-CSF and had blood cells harvested during recovery from myelosuppression. ‘G-CSF, de novo’ denotes chemotherapy naive patients who received G-CSF at 12 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7. ‘G-CSF + SCF’ denotes chemotherapy naive patient who received G-CSF at 12 μg/kg subcutaneously daily and SCF at 5 to 15 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7 of G-CSF administration. For each group of patients the horizontal bar denotes the median value, the box plot denotes the 5th and the 95th percentiles, and the whiskers denote the maximum and minimum values.

Fig. 2.

The CFU-GM yield of different mobilization protocols used in the authors' institution. ‘3-4gm Cy’ denotes patients who received cyclophosphamide 3 to 4 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. ‘7gm Cy’ denotes patients who received cyclophosphamide 7 g/m2 intravenously and had blood cells harvested during recovery from myelosuppression. ‘G-CSF, pretreated’ denotes patients who received G-CSF at 12 μg/kg subcutaneously and had blood cells harvested on days 5, 6, and 7. ‘Chemo + G-CSF’ and ‘Chemo + GM-CSF’ denote patients who received myelosuppressive chemotherapy and G-CSF or GM-CSF and had blood cells harvested during recovery from myelosuppression. ‘G-CSF, de novo’ denotes chemotherapy naive patients who received G-CSF at 12 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7. ‘G-CSF + SCF’ denotes chemotherapy naive patient who received G-CSF at 12 μg/kg subcutaneously daily and SCF at 5 to 15 μg/kg subcutaneously daily and had blood cells harvested on days 5, 6, and 7 of G-CSF administration. For each group of patients the horizontal bar denotes the median value, the box plot denotes the 5th and the 95th percentiles, and the whiskers denote the maximum and minimum values.

TECHNIQUES OF COLLECTION

Timing of Collection

Chemotherapy mobilization.Apheresis usually commences when the leukocyte count rises above 1 × 109/L and continues until an arbitrary target such as 3 × 108 mononuclear cells/kg BW is reached.17 Other groups have used increasing platelet counts or monocytosis as the starting criteria although they usually occur simultaneously. These days CD34+ cell measurement is preferrable because it is a more direct measure of progenitor cells. Most groups use 20 to 40 × 106 CD34+ cells/L as the threshold for starting apheresis.

G-CSF.Apheresis is usually performed on days 5, 6, and 7 of G-CSF administration. Progenitor cell levels start to decrease after day 8 even with continued G-CSF administration, so there is little advantage of continuing apheresis.

Chemotherapy + hematopoietic growth factor.Most groups start apheresis when the leukocyte count is 2 to 5 × 109/L and one report recommends not starting until the leukocyte count is >10 × 109/L.23 CD34+ cell levels should be measured to confirm progenitor cell mobilization.

Single Apheresis

There has been considerable interest in collecting sufficient progenitor cells for rescue from a single apheresis. In our experience, approximately half of previously treated patients undergoing G-CSF or chemotherapy + hematopoietic growth factor (HGF) mobilization achieved >1 × 106 CD34+ cells/kg in a single 2-blood–volume apheresis. However, such a yield can be achieved with a single apheresis in most patients with no previous chemotherapy who received G-CSF or G-CSF + SCF. Several groups are now using large-volume apheresis to maximise progenitor cell yield,174,175 although patient tolerance can be a limitation.

TYPES OF CELLS MOBILIZED

Hematopoietic Progenitor Cells

The number of CD34+ cells transplanted was first proposed by Siena et al42,176 as an indicator of the hematopoietic reconstitutive capacity of blood cells. Following these reports, flow cytometry was widely adopted for enumerating CD34+ cells, although there is no clear consensus as to the most accurate and easily transferable method for this.177 The coexpression of lineage or activation antigens useful for describing progenitor cells within BM178-181 has been used to determine the nature of mobilized CD34+ cells.182,183 Bender et al183 examined chemotherapy-mobilized CD34+ cells to determine the expression of myeloid (CD33) and lymphoid (CD19, CD7) antigens and the transferrin receptor (CD71). They reported that cyclophosphamide-mobilized CD34+ cells were different to BM CD34+ cells in two main respects. Firstly, there were very few pre-B lymphocytes in mobilized blood as determined by the low number of CD34+ cells expressing CD19. Secondly, mobilized CD34+ cells had low levels of CD71 expression, suggesting that they were not actively proliferating. Despite the small number of patient samples analyzed it was clear that variations existed in the incidence of different CD34+ subpopulations in different patients. Another study of chemotherapy + G-CSF mobilized CD34+ cells from 10 patients also showed marked heterogeneity in different patients in the coexpression of CD33 and CD71 antigens.184 The variable, but often high, level of CD71 expression was different than that described by Bender. However, both groups agreed that CD38 and HLA-DR antigens were present on more than 95% of mobilized CD34+ cells. A subsequent study of blood cells elicited by four different protocols indicated that G-CSF administration induced the highest level of CD34+CD38 cells, suggesting that G-CSF–mobilized blood contained a greater proportion of more primitive hematopoietic progenitors than those from other mobilization protocols.39 

More recently the presence of putative hematopoietic stem cells, CD34+ Thy-1+ cells in fetal liver, cord blood, and BM has been described.185 In the blood from 35 patients the proportion of CD34+Thy-1+ cells was highest on the first day of apheresis and progressively decreased on each subsequent day of collection.186 A further study examined the proportion of Thy-1+ cells within the CD34+lineage(Lin) negative population and also found that the proportion of CD34+LinThy-1+ cells was dependent on the day of leukapheresis.187 Notably, this study indicated that high levels of CD34+Thy-1+Lin cells may be present only transiently during mobilisation, despite the continued presence of CD34+ cells. This finding was confirmed by Stewart et al,188 who analyzed the blood and apheresis collections from 25 myeloma patients following cyclophosphamide and GM-CSF–induced mobilization. Although the frequency of CD34+ cells in blood cell collections coexpressing Thy-1 was heterogeneous (ranging from 6.2% to 50% of CD34+ cells), the highest levels were present on the first day of blood cell collection, although the difference in absolute numbers may be less. In a later study, Haas et al189 did not investigate the kinetics of mobilization of CD34+Thy-1+Lin cells but showed that after G-CSF, the proportion of CD34+Thy-1+ cells in apheresis collections was 1.4-fold more than that in BM obtained on the same day.

These findings indicate that the timing of apheresis may be critical for allogeneic transplantation where the number of CD34+Thy-1+Lin cells infused may determine long-term hematopoiesis. However, a more recent study by Humeau et al190 highlights the discrepancy in the number of CD34+ cells coexpressing Thy-1 with the number of CD34+CD38 cells, a subpopulation also considered to contain the long-term repopulating cells. They suggested that blood CD34+Thy-1+ cells are not homogenous and contain not only primitive progenitor cells. Although there is now considerable evidence of the importance of the CD34+ cell dose, the value of knowing the dose of CD34+Thy-1+ cells remains uncertain. Moreover, whether the Thy-1+ subset or the CD38 subset provides more accurate information on the long-term hematopoietic reconstitutive capacity of mobilized blood cells still remains to be shown.

Other studies of mobilized blood CD34+ cells have included assessment of CAM expression and proliferative potential.39,40,91,191 To et al39 reported lower CD71 expression and decreased rhodamine 123 retention in mobilized CD34+ cells compared with BM CD34+ cells, suggesting that circulating CD34+ cells are neither actively proliferating nor metabolically active. This characteristic of circulating progenitor cells was also observed in mice mobilized with G-CSF.192 The changes in CAM have been described in an earlier section.

It is important to consider that an immunophenotypically defined subpopulation of mobilized blood cells may not necessarily have the same functional properties as its BM counterpart. To assess the hematopoietic potential of different populations of hematopoietic progenitor cells a number of investigators have performed an extensive range of in vitro assays to document their functional capacity. The CFU-GM assay has long been used to enumerate hematopoietic progenitor cells and to assess the viability of cryopreserved blood cells. However, it does not provide direct information on primitive progenitor cells or progenitor cells committed to other lineages.

There are considerably fewer reports of mobilization of megakaryocytic progenitor cells (CFU-MK and BFU-MK) than of CFU-GM. Increased megakaryocytic progenitors were described in G-CSF–mobilized blood18 and in chemotherapy + hematopoietic growth factor–mobilized blood.193 In a recent study we found an average 75-fold increase in the number of megakaryocytic precursor cells in mobilized blood compared with steady-state blood in 53 patients mobilized by one of six protocols.194 Most of these precursor cells were CFU-megakaryocyte (CFU-Mk), which are likely to represent the progenitor cells responsible for early platelet recovery. There was a high correlation between the number of megakaryocyte progenitor cells and CD34+ cells that confirmed an earlier report showing that the megakaryocytic progenitor cell dose was no better than CFU-GM in predicting platelet recovery posttransplant.195 Hence, it seems that in most situations the number of blood CD34+ cells or CFU-GM infused will provide a guide to platelet reconstitution, at least during the first 2 to 4 weeks posttransplant. However, enumeration of precursor to megakaryocytic progenitor cells may be a better guide to long-term megakaryocytopoiesis.

One significant feature of autologous transplantation with mobilized peripheral blood is rapid lymphocyte reconstitution.48 Such a rapid recovery of T lymphopoiesis could be caused by the very large number of mature T cells or T-lymphoid progenitor cells in mobilized blood cells. The presence of the latter is supported by the demonstration of T-lymphocyte generation in a severe combined immunodeficient-human (SCID-hu) thymus assay by transplanting CD34+Lin cells isolated from mobilized blood.196 

The most primitive hematopoietic progenitor cells assayable in vitro is the long-term culture-initiating cells (LTC-IC). They are present at low levels in steady-state PB197,198 and a fivefold to sixfold higher incidence in mobilized blood.114,199,200 In Sutherland's studies there was more than a 2-log variation in the incidence of LTC-IC between patients and the number of LTC-IC in blood did not correlate with the numbers of CFU-GM, CD34+ cells, or the rate of engraftment. The lack of correlation between LTC-IC and the rate of engraftment is not surprising because the latter probably correlates better with the number of mature progenitor cells infused. The correlation between LTC-IC and long-term hematopoietic reconstitution may be more relevant but remains to be established. The same investigators also claim that LTC-IC in mobilized blood have significantly lower proliferative potential than BM LTC-IC. However, data from another candidate primitive hematopoietic progenitor cells, the precursor to CFU-GM (pre-CFU) as measured in stroma-free cytokine-dependent liquid cultures, suggest that CD34+ cells in mobilized blood have the same proliferative capacity as BM CD34+ cells.36 Nonetheless, both the LTC-IC and the pre-CFU assays are technically demanding and not yet fully quantitative, so are not likely to be used as routine assays in clinical laboratories. Advances in establishing a reproducible and quantitative assay for primitive progenitor cells would provide a much better measure of long-term reconstitutive capacity. Notwithstanding this proviso, the durability of long-term engraftment201 and the presence of primitive hematopoietic progenitor cells in mobilized blood seems beyond doubt. Unequivocal evidence will come from allogeneic transplantation or gene-marking studies.

Accessory Cells

The number of T lymphocytes, monocytes, and natural killer (NK) cells are much higher in PB transplants than BM transplants.48,49,202 These mature accessory cells are probably not critical for hematopoietic reconstitution as evidenced by the satisfactory reconstitution seen in patients rescued with cells positively selected for CD34+ cells. However, autotransplants using combined BM and mobilized blood cells containing only a low number of CFU-GM suggested that hematopoietic reconstitution occurred earlier than if BM alone or BM plus unmobilized blood cells were used.6,203 Furthermore, mononuclear cells obtained during hematopoietic recovery secrete more cytokines than those harvested during steady-state hemopoiesis.204 A study of cytokine levels posttransplantation also suggests that IL-6, G-CSF, and IL-8 levels are related to neutrophil recovery after stem cell transplantation. It is particularly noteworthy that the levels of IL-6, G-CSF, and IL-8 are higher following blood cell transplants than BM transplants.205 Because mononuclear cells are a known source of such cytokines it seems reasonable to attribute a complimentary role of accessory cells to hematopoietic reconstitution.

The immune reactivity of donor blood leukocytes in the control of leukemia after allogeneic BM transplants has been well documented.206 In autologous transplantation the high levels of NK cell numbers and activity in mobilized blood cells raise the possibility of using blood cells as a cell source for immunotherapy as well as hematopoietic reconstitution. In GM-CSF–mobilized blood cells the frequency of cytotoxic effector cells including lymphokine-activated killer (LAK) cells and lymphocytes was elevated, especially in the early harvests, whereas the later harvests contained more progenitor cells49; however, the difference in absolute numbers may be less. In cyclophosphamide + G-CSF–mobilized blood cells functionally active NK cells were present at 42 to 212 × 106/kg in the grafts and their percentage and cytotoxic activity increased from the beginning to the end of the harvesting procedure. CD3CD56+ and CD34+ cell numbers peaked at the same time. A 6 to 8 days' incubation with 100 U/mL, IL-2 expanded the NK population threefold to fivefold without adversely affecting CD34+ cells.202 Hence, the immunomodulatory potential of mobilized blood cells is worthy of further investigation.

Standardization of Progenitor Cell Measurement

CFU-GM and CD34+ cell measurements are the two most commonly used indices of the hematopoietic reconstitutive capacity of transplanted cells, but the standardization of these measurements remains elusive. Firstly, methodology in different laboratories varies greatly. Personal preferences and established practices all contribute but the large number of biological reagents involved and the lack of a ‘standard’ pose significant hurdles. Secondly, even in a single laboratory, the type of colony stimulatory factor, the batch of fetal calf serum, and the training of staff influence CFU-GM results significantly.207 For instance, a four-factor combination of G-CSF, GM-CSF, IL-6, and SCF stimulates 80% more CFU-GM than human placental conditioned medium although costing 20 times more. New staff members also show more variance in their colony counting than experienced members.

Fig. 3.

The threshold effect of progenitor cell dose on hematopoietic reconstitution after mobilized blood cell autotransplants in the authors' institution. In (A) and (B), patients were categorized into those receiving <15, 15 to 49.9, and ≥50 × 104 CFU-GM/kg BW. In (A) the probability of reaching 0.5 × 109 neutrophils/L (N500) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in the three categories were 47, 142, and 88, respectively. The differences between the three categories were significant (P < .0001, log-rank test). In (B) the probability of reaching 50 × 109 platelets/L (P50) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in the three categories were 45, 131, and 86, respectively. The differences between the three categories were significant (P < .0001, log-rank test).

In (C) and (D) patients were categorized into those receiving <1.5, 1.5 to 4.9, and ≥5 × 106 CD34+ cells/kg BW. The number of patients in these three categories were 39, 53, and 31, respectively. In (C) the probability of reaching 0.5 × 109 neutrophils/L (N500) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The differences between the three categories were not significant (P = .29, log-rank test). In (D) the probability of reaching 50 × 109 platelets/L (P50) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in these three categories were 35, 49, and 27, respectively. The differences between the three categories were significant (P = .0052, log-rank test).

Fig. 3.

The threshold effect of progenitor cell dose on hematopoietic reconstitution after mobilized blood cell autotransplants in the authors' institution. In (A) and (B), patients were categorized into those receiving <15, 15 to 49.9, and ≥50 × 104 CFU-GM/kg BW. In (A) the probability of reaching 0.5 × 109 neutrophils/L (N500) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in the three categories were 47, 142, and 88, respectively. The differences between the three categories were significant (P < .0001, log-rank test). In (B) the probability of reaching 50 × 109 platelets/L (P50) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in the three categories were 45, 131, and 86, respectively. The differences between the three categories were significant (P < .0001, log-rank test).

In (C) and (D) patients were categorized into those receiving <1.5, 1.5 to 4.9, and ≥5 × 106 CD34+ cells/kg BW. The number of patients in these three categories were 39, 53, and 31, respectively. In (C) the probability of reaching 0.5 × 109 neutrophils/L (N500) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The differences between the three categories were not significant (P = .29, log-rank test). In (D) the probability of reaching 50 × 109 platelets/L (P50) for each of these three categories was denoted by the lines - - -, — , ⋅⋅⋅, respectively. The number of patients in these three categories were 35, 49, and 27, respectively. The differences between the three categories were significant (P = .0052, log-rank test).

There was initial optimism that CD34+ cell enumeration may be preferable to clonogeneic assays as a measure of hematopoietic progenitor cells because fewer biologicals are required and electronic counting of large number of events should have a lower coefficient of variance. However, CD34+ cell enumeration protocols need to achieve the level of stringency to accurately measure rare events at the level of 0.1% to 3%. While a reliable, accurate, and transferable method for CD34+ cell enumeration is the aim of multiple intergroup collaborations, there is no agreement on a method of enumeration by multiparametric flow cytometry.42,182,208-212 

Several issues are critical in achieving standardization in CD34+ cell enumeration. Firstly, the method of sample processing influences the degree of cell debris and red blood cell contamination. Secondly, the CD34 antibody and the fluorochrome label used influence the specificity and sensitivity of immunolabeling. Thirdly, the gating strategy, including the denominator for the number of CD34+ cells, is critical in establishing the incidence of CD34+ cells relative to other leukocytes. It is essential that individual laboratories have well-documented methods, an appreciation of the statistical variance of their method and systems for internal and external comparisons with other laboratories. Laboratories should also consider adopting one of the standardized methods being developed by agencies such as the International Society for Hematotherapy and Graft Engineering.213 For a comprehensive review of this topic readers should consult the June 1996 issue of the Journal of Hematotherapy.213-216 

The reporting of a reference range based on healthy individuals would provide a means of establishing comparability of data between different laboratories using different methods for enumerating CFU-GM or CD34+ cells. Such a practice is mandatory in most laboratory measurements and it is surprising that it has gained little support among transplantation laboratories.

TARGET AND THRESHOLDS

A target progenitor cell yield from leukaphereis is important because the number of progenitor cells infused correlates with the rate of hematopoietic reconstitution which affects the safety and costs of transplants. The target yield then determines when and how many leukaphereses are required. Unlike BM transplants, nucleated cell dose does not appear to be as effective as progenitor cell dose in predicting hematopoietic reconstitution. Furthermore, the progenitor cell dose:hematopoietic reconstitution relationship in blood cell transplants can be described in terms of a minimum and an optimum threshold for rapid reconstitution, a threshold for sustained reconstitution, and a threshold of rapid reconstitution which cannot be lowered even with very high progenitor cell dose and cytokine administration.41,42,44,45,76,116,160,217-219 A highly significant correlation between CFU-GM and CD34+ cells as indices of hematopoietic reconstitutive capacity has been confirmed by numerous reports so a threshold based on either assay is equally valid.

A CFU-GM cell dose effect was first suggested in 198641 when analysis of the limited data available then suggested a minimum of 30 to 50 × 104/kg BW for rapid hematopoietic reconstitution. In G-CSF–mobilized blood cell transplants Sheridan et al220 reported that patients receiving >30 × 104 CFU-GM/kg BW recovered faster than those receiving less. In another report patients receiving <20 × 104 CFU-GM/kg had a significantly lower probability recovering to 0.5 × 109 neutrophils/L by day 13 and 50 × 109 platelets/L by day 15 compared with those patients receiving the above-mentioned threshold progenitor cell dose.45 Currently 15 to 20 × 104 CFU-GM/kg or 1 to 2 × 106 CD34+ cells/kg is generally agreed as the minimum threshold below which rapid hematopoietic reconstitution may not occur.44,76 

A progenitor cell dose above the minimum threshold is associated with increasingly rapid hematopoietic reconstitution.76,221 However, there seems to be an upper threshold effect at 50 × 104 CFU-GM/kg or 5 to 8 × 106 CD34+ cells/kg, above which further increase in cell dose does not further hasten recovery.42,44,46,116 Bender et al44 also suggested that there may be a minimum threshold of 5 to 20 × 104 CFU-GM/kg or 0.5 to 2 × 106 CD34+ cells/kg for long-term reconstitution.

Figure 3 shows the different probabilities of neutrophil and platelet reconstitution in patients receiving different numbers of progenitor cells in our institution. Those receiving less than the minimum threshold numbers have a significantly higher probability of slow reconstitution while those receiving above the optimum threshold number have a 90% or higher probability of rapid reconstitution. However, patients receiving >8 × 106 CD34+ cells/kg BW do not recover more rapidly than those receiving 5 to 8 × 106/kg BW. The same trend of minimum and optimum threshold is seen across the spectrum in patients with different diseases, mobilization protocols, and high-dose therapy.

In patients with acute myeloid leukemia (AML) transplanted with mobilized blood cells a secondary decrease in platelet counts often occurred during the second month posttransplant after initial rapid reconstitution. Even in patients administered ≥100 × 104 CFU-GM/kg the platelet count decreased to below 20 × 109/L although eventual recovery usually occurred.218 Such a pattern is not seen in non-AML patients and there is no lack of megakaryocytic progenitors in the mobilized blood cells of these patients.222 Hence, a minimum threshold for sustained platelet reconstitution has not been identified in AML patients.

Previous chemotherapy is another variable considered important in determining progenitor cell threshold for rapid engraftment. Tricot et al160 analyzed 225 patients receiving autologous mobilized PB transplants for multiple myeloma and found that the minimum CD34+ cell threshold was ≥2 × 106/kg for patients with ≤24 months of chemotherapy but ≥5 × 106/kg for patients with longer chemotherapy exposures. Whether this reflects a poorer quality of CD34+ cells after prolonged chemotherapy or concomitant stromal damage interfering with engraftment remains to be determined.

Ex Vivo Expansion of Progenitor and Postprogenitor Cells

An obligatory delay of 7 to 10 days before clinically significant engraftment persisted even when large numbers of progenitor cells, eg, 400 × 104 CFU-GM/kg, were re-infused. Even in patients who received mobilized blood cells as well as G-CSF posttransplant the median time to neutrophil and platelet engraftment is little better than mobilized blood cells alone.20,223 This time delay is similar to the time for colony formation in vitro and thus probably reflects the time required for infused progenitor cells to home to BM and then to divide and mature to provide detectable engraftment.36,45 

This observation leads to studies of ex vivo expansion of progenitor and postprogenitor cells with the aim of abrogating cytopenia posttransplant. Cell proliferation and orderly differentiation stimulated by myeloid growth factors and/or hematopoietic stroma have been shown both in small- and large-scale cultures36,224-227 with the hematopoietic growth factor combination and the culture system used identified as important variables. The hypothesis is that infusion of promyelocytes and myelocytes produced ex vivo from mobilized CD34+ cells may produce earlier engraftment.36 In theory, appropriate culture systems may also expand erythroid and megakaryocytic cells.

The lack of toxicity of such ex vivo–expanded cells has been demonstrated with up to 157 × 106 cells/kg infused,228 although no reduction in cytopenia was evident. However, PIXY321 was the only hematopoietic growth factor used in this study so cells expanded using more active combinations such as G-CSF, GM-CSF, IL-3, or IL-6 may be more effective.36,225 

Ex vivo expansion has also been applied to expanding a small aliquot of mobilized cells to provide sufficient progenitor cells for hematopoietic rescue.229 This will reduce the need for leukapheresis and possibly the number of contaminating malignant cells infused. Another important potential application of ex vivo expansion is in expanding an apheresis product with a low number of progenitor cells to provide sufficient cells for rescue. The feasibility of such an approach is not known.

Difficult to Mobilize Patients

In most reports there is a subset of patients, most of them heavily pretreated, who did not achieve satisfactory progenitor cell mobilization. Inherent biologic factors do exist as demonstrated by poor mobilization in SCF– or c-kit–deficient mice compared with wild-type mice103 and the considerable heterogeneity in progenitor cell yield even in patients with no previous chemotherapy receiving G-CSF.123 No generally agreed strategy exists for patients who failed to mobilize with G-CSF or chemotherapy + hematopoietic growth factors. The IL-3–GM-CSF combination was not particularly effective, although combinations of G-CSF and SCF, G-CSF, and Flt3 ligand hold promise. Direct mobilizers such as IL-8 alone or in combination with other cytokines may be more effective. Better understanding of the mechanism of mobilization may also contribute to the development of better mobilization protocols for difficult-to-mobilize patients.

CLINICAL RESULTS

Hematopoietic and Immune Reconstitution

There is now overwhelming evidence that trilineage recovery occurs within 2 weeks of transplant using mobilized blood cells provided the above threshold numbers of progenitor cells are given. Initial studies were mostly phase I/II studies based on comparison with historical or concurrent but nonrandomized BM transplant patients. However, reports of randomized studies are now appearing. A randomized comparison of 46 patients with relapsed or refractory germ cell tumors randomized to either BM or G-CSF + chemotherapy mobilized blood cell rescue showed that mobilized blood cells result in quicker hematopoietic reconstitution, leading to fewer days on intravenous antibiotics and a shorter time to transfusion independence.230 

On first principles, subsets of CD34+ cells may provide more specific information on lineage recovery. However, neutrophil progenitors as measured by CD33+CD34+ cells have not been shown to be more informative than CD34+ cells. This may be due to the difficulty in defining CD33 positivity because CD33 expression in CD34+ cells tends to be more like a continuous population than distinct positive/negative populations.39 The measurement of megakaryocytic progenitor cell in PB based on CD41 or CD61 expression has been bedevilled by high false-positivity secondary to platelet binding to monocytes.231 In contrast, Derskson et al97 reported that the CD34+L-selectin+ cell dose predicts rapid platelet recovery after blood cell transplants using chemotherapy + G-CSF mobilization. How the expression of an adhesion molecule influences platelet reconstitution is not yet known, although the investigators suggested that enhanced homing may be responsible.

In allogeneic and autologous BM transplants the predominant change in immune status is suppression. However, the transplant of circulating, long-living, immune competent cells was first described in 1972 for the treatment of chronic mucocutaneous candidiasis with leukocytes from HLA-compatible siblings.68 In 1979 lymphoid reconstitution after blood cell transplant was shown to be more rapid than that following BM transplants in animal studies.232 In humans rapid T-lymphocyte recovery after autologous blood cell transplant was first described in 198747 and confirmed by several other studies.48,233,234 In a comparative study of 49 blood cell transplants and 18 BM transplants, Roberts et al48 reported that recovery of lymphocyte count, CD3, CD4, and CD8 cells was significantly faster after blood cell transplants than allogeneic BM transplants. CD8+ cells recovered within 2 weeks posttransplant whereas CD4+ cells lagged behind with an inversion of the CD4/CD8 ratio. Although such a pattern is similar to that in BM transplants, CD4 recovery to 0.2 × 109 cells/L occurred faster in blood cell transplants than in BM transplants. This CD4 threshold has been identified as a level below which significant infective risk occurs in human immunodeficiency virus (HIV) patients.235 Donor T-cell clones have shown ability to transfer cellular immunity against cytomegalovirus in allogeneic BM transplants,236 so it is possible that infused T cells in blood cell transplants contribute to reconstitution of immunity and therefore lower antibiotic usage.

Roberts et al48 reported that CD20 cells were significantly higher after blood cell transplants than allogeneic BM transplants, but recovery of NK cells showed no difference between transplant types. Functional NK cell recovery paralleled numerical recovery with rapid reconstitution 10 to 14 days after transplantation237 and full recovery after 4 to 5 weeks.202 IL-2 after autologous BM transplants in acute leukemia has been suggested as a means of reducing relapse. The rapid NK recovery in blood cell transplants may provide an even better setting to test this hypothesis.

Before We All Say Blood, ...

Since the change from using BM to mobilized blood cells requires re-equipping (blood cell separator, flow cytometry), retraining (apheresis staff ), and sometimes rescheduling (optimally timed blood cell harvesting requires rapid deployment of apheresis and laboratory staff ), it was often asked whether one can obtain sufficient cells from BM. A Danish group has studied whether cytokine priming of BM before harvest would lead to a more rapid hematopoietic reconstitution without the need for leukapheresis.238 In their latest report Johnsen et al239 described patients receiving either IL-3 10 μg/kg/d for 10 days, GM-CSF 10 μg/kg/d for 5 days, or G-CSF 10 μg/kg/d for 5 days. Cytokine priming led to a twofold to fourfold increase in mean light-density cell and CFU-GM yield in a standard 1-L BM harvest. However, in the 17 patients who received primed BM (4 receiving IL-3, 5 receiving GM-CSF, and 8 receiving G-CSF ), the rate of hematopoietic reconstitution was no faster than historical controls receiving unprimed BM but 10 to 20 days slower than a parallel cohort of patients receiving G-CSF–mobilized blood cells.239 

Another recent report described no difference in neutrophil and platelet recovery between G-CSF–mobilized blood cell and G-CSF–primed BM autotransplants.240 Because G-CSF was used posttransplant, any difference in neutrophil reconstitution due to the type of cells used had been minimized.17,223 Why platelet reconstitution was no different between the two groups is intriguing, although this may be partly explained by the presence of activated accessory cells and G-CSF–primed blood cells in the BM used.

Nonetheless, this issue of BM or PB should be re-examined whenever new cytokines or improved scheduling or combinations of cytokines become available. It is conceivable that a combination of G-CSF, thrombopoietin, and early acting factors such as SCF or Flt3 ligand may stimulate BM sufficiently to provide high numbers of progenitor cells for rapid engraftment and multiple rescues.241 

Tumor Control

Since the benefit of mobilized blood cell transplant is shorter hospitalization, lower blood products and antibiotic usage, and lower procedure-related mortality, such transplants should not by themselves lead to a different tumor control outcome than BM transplants.242 However, the increased safety and high number of progenitor cells harvested open up additional options.

Older patients and more diseases are now treated with blood cell transplants compared with BM transplants. It is now commonplace to perform transplants in patients above 60 and most transplants in breast cancer are performed with mobilized blood cells.

An even more important development is the use of multiple cycles of high-dose chemotherapy and blood cell transplants to deliver a higher total dose and dose rate.123,243-245 In many instances, myelosuppressive rather than supralethal doses were administered, but the emphasis is rightly that of tumor cell kill rather than myeloablation. This applies particularly to the more slowly growing tumors because multiple submaximal high-dose therapy may achieve a higher cumulative cell kill than a single intensive assault.

Bezwoda et al246 described a randomized study comparing double high-dose therapy (cyclophosphamide 2.4 g/m2, mitoxantrone 35 to 45 mg/m2, and etoposide 2.5 g/m2 6 weeks apart) and mobilized blood cell rescue with 6 to 8 cycles of conventional-dose cyclophosphamide 0.6 g/m2, mitoxantrone 12 mg/m2, and vincristine 1.4 mg/m2 as first-line therapy for metastatic breast cancer in 90 patients. The high-dose therapy group had a significantly higher response rate (95% compared with [c.f.] 53%) and complete remission rate (51% c.f. 4%), and longer median duration of response (80 weeks c.f. 34 weeks) and survival (90 weeks c.f. 45 weeks). The prolongation of response and survival times was almost entirely due to the relative proportion of patients who achieved complete remission, which was most probably caused by the dose escalation. Such improvements are clinically noteworthy irrespective of whether eventual cure occurs.

Other issues that may impact on tumor control include CD34+ cell selection, tumor purging, and the effect of accessory cells. A 3 to 5-log reduction in malignant contamination in the transfused cells is achievable by CD34+ cell selection.38,247 However, the presence of the clonotypic BCL2-IgH rearrangement in CD34+CD19+ progenitor cells in patients with follicular lymphoma raises the question that selection based on CD34+ expression alone may be insufficient.248 Tumor-directed purging may be more specific but its application is limited to AML, neuroblastoma, and lymphoma because a specific tumor marker is required. The large number of accessory cells may be targeted for immunomodulation to enhance ‘graft-versus-tumor’ effect, although no data are available.

A number of such innovations was incorporated in a report of 21 patients with non-Hodgkin's lymphoma who received hematopoietic rescue using mobilized blood cells collected in a single apheresis product which was enriched for CD34+ cells by a discontinuous Percoll gradient (Pharmacia, Uppsala, Sweden) and then purged with a panel of anti-B cell or anti-T cell monoclonal antibodies and complement.249 In the authors' institution a current study in myeloma patients involves 2 cycles of high-dose therapy rescued with immunomagnetically selected CD34+ cells from mobilized blood but the second selection is performed on cells harvested during recovery from the first high-dose therapy. Such an approach combines multiple-cycle chemotherapy with in vitro and in vivo purging. With the large number of CD34+ cells and accessory cells available in mobilized blood, multiple modality approaches can be tested.

Malignant Contamination

The improvement in the mobilization of blood progenitor cells and the increasing ability to deliver dose-intensified therapy has not been matched by an advance in our understanding of the mobilization of malignant cells. Recent advances in the detection of low levels of tumor cells/markers have provided much-needed information on malignant contamination in autografts.

Acute leukemia.Small numbers of leukemic cells among normal hematopoietic progenitors can be distinguished using morphologic and cytochemical examinations, but they are both laborious and insensitive. Better techniques are based on the identification of karyotype abnormalities by in situ hybridization, immunophenotypic abnormality by flow cytometry, genetic abnormalities and antigen-receptor gene rearrangements by polymerase chain reaction (PCR), and abnormal cell growth by clonogenic assays.250 

We have recently performed serial trisomy 8 studies using a centromeric probe for fluorescent in situ hybridisation (FISH) in an AML patient whose leukemic cells bear a trisomy 8 abnormality (White D, et al, submitted). Although all remission (postinduction and posttransplant) BM and PB metaphases showed a normal karyotype, FISH studies consistently detected a level of 3% to 12% trisomy 8 in interphase cells. The level in chemotherapy-mobilized blood cells was similar to steady-state BM and PB. Combined flow cytometric sorting and FISH analysis showed that the trisomy was not present in lymphoid cells so the persistent trisomy postinduction and transplant was not caused by long-living lymphocytes. The patient relapsed 3 months after an autologous transplantation using remission BM and blood cells in first remission. Hence, leukemic cells appear to be present even during clinical and cytogenetic remission. Together with the genetic marking studies251 it seems that leukemic cells are present in BM and mobilized and steady-state blood cells in some cases of AML and they may contribute to relapse. This is consistent with reports showing the advantage of purging in autologous transplantation in AML.252 Nonetheless, not all patients receiving autologous transplants relapse,253 so whether leukemic contamination occurs in all patients is not yet known.

In acute lymphoid leukemia (ALL) persistence of the leukemia-associated molecular marker indicates a higher risk of relapse,254,255 although not all PCR-positive patients had relapsed. Seriu et al255 reported that 8 of 13 mobilized leukapheresis products from 5 children were PCR-positive, although the levels were generally lower in PB than in BM. One patient transplanted with PCR-negative blood cells relapsed first in the central nervous system and then in BM. Three of four children transplanted with PCR-positive blood cells relapsed within 6 months, and yet one remained in remission 17 months posttransplant. Hence, mobilization of leukemic cells seems to occur in ALL and transplant with leukemic marker–positive blood cells in ALL appears to be associated with a high risk of relapse.

Lymphoma and multiple myeloma.Sharp et al256 studied BM and blood cell harvest specimens and reported the proliferation of cells carrying the same Ig gene rearrangement as the original lymphoma. Other groups have also demonstrated lymphoma-associated molecular marker in mobilized blood cells although no quantitative comparison with BM or steady-state blood was made.30,257 

Ig gene fingerprinting has also enabled the detection of myeloma cells in mobilized blood cells. A monoclonal population was detected in 44% of 22 patients and their presence was correlated with serum β-2-microglobulin levels. It was suggested that blood cell contamination defines poor-risk patients.258 Henry et al259 described PCR-positive harvests in 7 of 8 multiple myeloma patients but estimated that the number of myeloma cells infused would be lower with blood cell than with BM transplants.

Breast and ovarian cancer.Sharp et al256 also described the identification of morphologic malignant breast cancer cells in BM from breast cancer patients. They further reported that those with positive culture did worse after autologous transplantation than those without. The detection of breast cancer cells in BM and mobilized blood cells has since been reported by several groups.30,260 Brugger et al30 showed that cytokeratin (CK)- or epithelial antigen (HEA)-positive cells measured immunocytochemically were present in PB of 29% of patients with stage IV breast cancer. After chemotherapy + G-CSF, 21% of those without demonstrable circulating CK/HEA+ cells during steady state became positive. All stage IV breast cancer patients tested positive. Interestingly the timing of CK/HEA+ cell mobilization seems to depend on BM involvement. In patients without BM involvement, CK/HEA+ cell mobilization occurred in the first week after chemotherapy. In patients with BM involvement CK/HEA+ cell mobilization occurred in the second week, at the same time as CD34+ cell mobilization. These findings, if confirmed, may have major impact on progenitor cell mobilization in patients with stage IV breast cancer. However, the specificity of the HEA antibodies has been questioned and the tumorigenicity of these cells is yet to be determined.

A soft-agar culture stimulated by GM-CSF, epidermal growth factor, and insulinlike growth factor to detect viable breast cancer cells was pioneered by Ross et al28 and has the potential advantage of demonstrating viability. Tumor cell detection by this method correlated with the immunocytochemical method. Malignant contamination in mobilized blood cells appeared to be less frequent than BM and may even be absent.28,29,261 No data on the time course of mobilization were reported.

In an immunocytochemical study of epithelial contamination in mobilized blood cells and BM from 22 patients with ovarian cancer, mobilized blood cells had a lower tumor contamination than BM.29 

The presence of ‘tumor’ cells by morphologic examination, the demonstration of CK+ cells, or the detection of a clonal genetic mutation by molecular or cytogenetic techniques are all important findings because they suggest strongly that cells of the neoplastic lineage are present. The growth of clonogenic tumor cells provides an even stronger evidence. Hence, malignant contamination of mobilized blood cells does occur, although probably less than with BM.

The crucial question of whether cells or molecular markers indicative of the target neoplasm represent tumor stem cells or effete and cells is less easy to answer. Their association with relapse may indicate a persistent though subclinical residual tumor rather than causative effect. The notable exception is in AML and neuroblastoma where gene-marking studies have shown that the autologous cells infused contributed to relapse.251 Even there the conclusion still falls short of proving that they cause relapse. Moreover, several salient clinical observations remind us that not all neoplastic cells cause relapse.

Neiderwieser et al262 described how a female patient with chronic myeloid leukemia achieved complete remission after receiving BM from her brother donor, who unfortunately developed acute leukemia himself. Even though the transplanted BM contained 27% myeloblast, engraftment occurred with normal but not leukemic male cells. She relapsed with her brother's leukemic cells 6 months later. The initial engraftment with normal donor cells instead of donor leukemic cells suggests that most leukemic cells do not cause relapse and that only the leukemic stem cells can.

Goldman et al10 reported 20 patients with Philadelphia chromosome (Ph′ )-positive chronic myeloid leukemia (CML) who received autologous chronic phase blood cell transplant. Although a chronic phase was restored in most patients, 2 patients achieved Ph′-negative hematopoiesis after a period of cytopenia.10,263 Hence, the infused chronic phase Ph′-positive blood cells failed to engraft even though there was no reason why they should be rejected.

These observations compel us to examine the question of malignant contamination more critically. Whether the tumor stem cell exhibits the same phenotype as the majority of tumor cells is unknown. Furthermore, whether all viable cells that bear the same immunophenotype and molecular phenotype are capable of metastasis is yet to be determined. The SCID mouse/leukemic cell xenograft model is already providing insights into the different immunophenotype of leukemic stem cells and their progeny,264 and may provide a more relevant assay of the significance of such cells. At a more basic level it would also be important to identify whether tumor cells are mobilized by the same mechanism(s) as CD34+ cells and to explore whether differential mobilization of normal cells can be achieved.

SPECIAL AREAS

Cost Effectiveness Analysis

Chao et al122 compared the short-term medical costs between patients with relapsed Hodgkin's disease transplanted with steady-state blood and patients transplanted with G-CSF–mobilized blood cells, both groups receiving G-CSF posttransplant. There was an average 45% net decrease in costs associated with the use of G-CSF–mobilised blood cells, mainly due to earlier platelet recovery and shorter hospitalization. Another retrospective comparison between the costs of mobilized blood cell and BM transplants in France showed that blood cell transplants, at a mean of $29,000, cost $7,800 less.265 

A recent report compared the survival, quality of life, therapy costs, and cost-effectiveness in three groups of myeloma patients: Durie-Salmon classification grade III receiving high-dose therapy and melphalan-mobilized blood cell rescue (group I); grade III receiving conventional polychemotherapy (group II); and grade II receiving conventional chemotherapy (group III).266 The median survival and quality of life index (based on a 10-step scale) were significantly lower in group II than in group I. The quality of life index of group III was also lower than group I although survival was not. The total global cost based on the mean duration of and degree of dependency during hospitalization, mean numbers of laboratory analysis, radiologic investigations, and operative procedures and outpatient care costs were higher in group I than the other two groups (US $56,700, $46,555, and $37,430, respectively). However, for absolute cost-effectiveness (corrected for survival) the costs per week of life gained of group I (US $350) compared extremely well with those of group II (US $1,862). Furthermore, qualitative cost-effectiveness (weeks of survival gained, corrected for quality of life) was only +US $74/wk comparing groups I and II.

Although the quality-of-life scale is relatively crude and the therapy cost models are retrospective estimates, these reports nonetheless represent a praiseworthy effort in addressing the cost-benefit issues of blood cell transplantation. There is a cost saving associated with the change over from BM to blood cell transplants due to lower resource utilization. Blood cell transplants may be more expensive than conventional chemotherapy in the short term but would most probably lead to an improved cost-effectiveness when there is a significant difference in response and progression-free survival. The critical question of what is the cut-off point for medical costs versus quality and quantity of life gained will be different for different treatment protocols and diseases. To insist on such measurements to evaluate all new treatment modalities will become a more urgent and unavoidable call.

Special Issues in Allogeneic Blood Cell Transplantation

Allogeneic hematopoietic progenitor cells provide a tumor-free graft with proven or potential graft-versus-tumor activity. In aplastic anemia, acute leukemias, CML, myelodysplasia, and genetic diseases, allogeneic cells have been the cell of choice. In the first report of allogeneic blood cell transplantation, the patient received nonmobilized blood cells but died too soon posttransplant to be evaluable.267 More recently, numerous reports of successful transplants using G-CSF–mobilized blood cells from allogeneic donors have appeared.124-128 Rapid hematopoietic reconstitution, no increased graft-versus-host disease (GVHD), and donor preference encourage the use of mobilized blood cells instead of BM in the allogeneic setting as in the autologous setting.

There was initial caution about allogeneic blood cell transplantation because of the potential of severe GVHD from the high number of T cells infused and the uncertainty about the safety of administering recombinant growth factor for mobilization. The accumulated experience has dispelled the fear of severe GVHD and demonstrated the short-term safety of administering G-CSF to donors even though the long-term effect is still unknown. Many donors and investigators consider that the avoidance of general anesthesia, soft tissue, and bone trauma more than compensates for the potential risk of G-CSF administration. These issues have been addressed in a recent annotation.50 

Most transplants were performed using unmodified blood cells so the number of T cells infused ranges from 1 to 5 × 108/kg BW compared with <0.5 × 108/kg BW in BM transplants. The lack of severe GVHD suggests strongly that its occurrence relates more to genetic incompatibility than to the number of T cells infused. An alternative hypothesis is that T cells in mobilized blood cells are different from those in BM. Further studies are required to elucidate this observation. Whether CD34+ selected blood cells offer any advantage is not known, but the lower number of T cells infused may enable less intensive GVHD prophylaxis.

Hematopoietic reconstitution in the initial reports was not as fast as that in autologous mobilized blood cell transplants. This is probably due to the use of methotrexate in GVHD prophylaxis because the rapidity of reconstitution in patients receiving cyclosporin and prednisolone is more comparable.268 Sustained long-term engraftment beyond 2 years has been shown124,128 with no report of late graft failure. Naive and memory helper T-cell and B-cell recovery is more rapid after mobilized blood cell transplants than BM transplants.269 Proliferative responses to phytohemagglutinin, pokeweed mitogen, tetanus toxoid, and candida were also higher.269 In a patient with mucopolysaccharidase deficiency type VI transplanted with G-CSF–mobilized allogeneic blood cells, serum galactosamine-4-sulfatase level increased from 0% to 100% day 9 posttransplant at the same time when hematopoietic reconstitution occurred (Toogood I., unpublished data). Hence, functional reconstitution of enzyme activity seems equally rapid.

The large number of progenitor cells in mobilized blood cells may also provide additional leverage to overcome rejection associated with hematopoietic cell transplantation across major HLA barriers.270 This was borne out in patients transplanted with T-cell–depleted BM and mobilized blood cells from haplo-identical family members.271 They showed rapid and sustained hematopoietic reconstitution without significant GVHD. The potential impact of using a high progenitor cell dose to force engraftment even in mismatched or unrelated transplants is enormous.

The EBMT consensus statement on allogeneic blood cell transplantation provides a set of state-of-the-art recommendations.50 They include G-CSF at 10 μg/kg/d, starting leukapheresis on the day after the fourth dose with a continuous flow blood cell separator using peripheral veins, processing up to 15 L of blood per day, CD34+ cell target of 2 to 3 × 106/kg, and standard GVHD prophylaxis. The critical question of whether allogeneic blood cells may replace BM may be answered in the next few years.

CML and Myelodysplasia

The predominance of the Ph′-positive, BCR-ABL rearranged clone in CML is well established. However, the presence of ‘normal’ stem cells in chronic phase has also been shown.272,273 While allogeneic and matched unrelated transplantation have been the preferred treatment, autologous transplants have been explored in patients without a histocompatible donor. A most intriguing observation was the establishment of a Ph′-negative remission after autologous transplant with chronic-phase blood cells.10,263 Furthermore Korbling et al9 showed that Ph′-negative CFU-GM could be detected during the recovery phase following chemotherapy similar to that used for AML. This phenomenon was exploited by Carella et al274 using a combination of G-CSF and intensive induction chemotherapy. Ph′-negative remission has been achieved after autologous transplantation using mobilized blood cells. Ex vivo selection based on CD34 and HLA-DR expression,275 functional isolation of primitive stem cells,276 long-term culture,277 ribozymes,278 and anti-sense oliginucleotides279 are strategies that may deplete the Ph′-positive clone in mobilized blood cells. Hence, autologous transplant is a therapeutic option to be considered in patients not eligible for allogeneic transplants.

Autologous transplant is usually not recommended for myelodysplasia because of doubts about how frequent residual normal cells are in this condition. However, the mobilization of polyclonal primitive hematopoietic progenitor cells in patients with high-risk myelodysplasia after induction chemotherapy has been reported recently.280 This is analogous to CML and may provide a new option for patients without a histocompatible donor.

Pediatric Patients

The most comprehensive series of reports of pediatric blood cell harvesting and transplants comes from Takaue et al.281 The main distinctives in this pediatric population are special requirements for vascular access and leukapheresis, high progenitor yields, and risks of ‘stem cell exhaustion.’ Sustained cytopenia after blood progenitor cell collection occurred in two 3-year-old children with cancer, although adequate hematopoietic reconstitution was re-established after high-dose therapy and stem cell rescue.282 The investigators suggested that the mobilizable pool is a major component of the total body pool in small children during hematopoietic recovery.

Applications in Nonmalignant Diseases

Paroxysmal nocturnal hemoglobinuria (PNH) is associated with a deficiency of decay accelerating factor (DAF ) and membrane inhibitor of reactive lysis (CD59) on hematopoietic cells. Prince et al283 recently reported that CD34+CD38 cells in G-CSF– or GM-CSF–mobilised blood are relatively enriched for DAF+CD59+ cells compared with those in steady-state blood and suggested that apheresis sample can serve as a source of unaffected stem cells for autologous transplantation of PNH patients.

High-dose immunosuppressive therapy such as total nodal irradiation, antilymphocyte globulin, and high-dose cyclophosphamide have been suggested for the treatment of multiple sclerosis.284 However, experimental studies suggest that total lymphoid and myeloid ablation and subsequent recapitulation of lymphocyte ontogeny by hematopoietic rescue may stop the auto-immune destruction of myelin. Although radical at first sight, this type of approach has already been applied to aplastic anemia, a probable auto-immune disease. There are also anecdotal clinical observations that patients with a coincidental auto-immune disease such as psoriasis, ulcerative colitis, and rheumatoid arthritis who undergo BM transplants for other reasons have durable remissions of their autoimmune disease. Hence, autologous transplant has been proposed for the treatment of severe autoimmune disease and multiple sclerosis.

Mobilized blood cells have been proposed as the source of CD34+ cells for gene therapy.33,34 Although a high transduction efficiency has been demonstrated in vitro,33 continued expression posttransplant remains low.34 There are still many technical hurdles associated with gene therapy,285 but mobilized blood cells do provide a larger number of progenitor cells than BM harvest could. Specific diseases or therapeutic indications that have been targeted include severe combined immune deficiency,286 P-glycoprotein expression,287 methotrexate resistance,288 chronic granulomatous disease,289 and Gaucher disease.290 

SUMMARY

Mobilized blood cells produce faster hematopoietic and immune reconstitution than BM, making high-dose therapy safer and more cost effective. They are becoming the main cell source for autologous rescue and may provide an alternative in CML and myelodysplasia. Mobilized allogeneic blood cells have been used without severe GVHD while reproducing the rapid reconstitution seen in the autologous setting. The potential of using a high cell dose to transplant from mismatched or unrelated donors is exciting. Mobilized blood cells may yet replace BM in allogeneic transplants.

G-CSF alone (autologous and allogeneic) or a combination of chemotherapy and hematopoietic growth factors such as G-CSF and GM-CSF (autologous only) are the most commonly used mobilization protocols. They appear to be able to achieve adequate progenitor cell yields for single transplants in most patients except those who have been heavily pretreated. Indeed, a single apheresis may provide sufficient progenitor cells, especially in allogeneic donors. The design of mobilization and high-dose therapy protocols should incorporate mobilization early in the treatment process before BM exhaustion occurs. Adequate standardization of progenitor and stem cell measurement is necessary for reliable quantitation of hematopoietic reconstitutive capacity. Current data suggest the presence of minimum and optimum thresholds.

Blood cell transplants may have additional impact on tumor control. The large number of progenitor cells allows for multiple high-dose therapy and rescues. Tumor-directed purging and CD34+ cell (or its subset) selection are similarly facilitated. Lower tumor contamination of blood cells compared with BM has been suggested. The large number of accessory cells also allows for immunomodulatory approaches to enhance graft-versus-tumor response. None of these have been proven in phase III studies but are important research areas.

Major future advances may occur through better understanding of the mechanism of mobilization. This may provide a means of direct and therefore more predictable and higher-yield mobilization and also differential mobilization of normal and tumor cells. Technologic advances in ex vivo processing may also lead to more cost-effective high-dose therapy such as ambulatory transplants using expanded cells, tumor-free grafts, and genetically modified grafts. It is likely that mobilized blood will be used to treat nonmalignant diseases and as a vehicle for gene therapy. Lymphoid reconstitution may also provide an alternative means of treating autoimmune diseases.

ACKNOWLEDGMENT

The authors thank Ann Haylock for her tireless stenographic assistance, and Che To and Val and Garry Bickley for their review of manuscript.

Address reprint requests to L.B. To, MD, Division of Haematology, Hanson Centre, IMVS, Frome Rd, Adelaide SA 5000, Australia.

REFERENCES

REFERENCES
1
Gratwohl
A
Baldomero
H
Hermans
J
Hematopoietic precursor cell transplants in Europe: Activity in 1994. Report from the European Group for Blood and Marrow Transplantation (EBMT).
Bone Marrow Transplant
17
1996
137
2
Juttner
CA
To
LB
Haylock
DN
Branford
A
Kimber
RJ
Circulating autologous stem cells collected in very early remission from acute non-lymphoblastic leukaemia produce prompt but incomplete hemopoietic reconstitution after high dose melphalan or supralethal chemoradiotherapy.
Br J Haematol
61
1985
739
3
Reiffers
J
Bernard
P
David
B
Vezon
G
Sarrat
A
Marit
G
Moulinier
J
Broustet
A
Successful autologous transplantation with peripheral blood hemopoietic cells in a patient with acute leukaemia.
Exp Hematol
14
1986
312
4
Korbling
M
Dorken
B
Ho
AD
Pezzuto
A
Hunstein
W
Fliedner
TM
Autologous transplantation of blood derived hemopoietic stem cells after myeloablative therapy in a patient with Burkett's lymphoma.
Blood
67
1986
629
5
Kessinger
A
Armitage
JO
Landmark
JD
Weisenberger
DD
Reconstitution of hematopoietic function with autologous cryopreserved circulating stem cells.
Exp Hematol
14
1986
192
6
Bell
AJ
Oscier
DG
Figes
A
Hamblin
TJ
Use of circulating stem cells to accelerate myeloid recovery after autologous bone marrow transplantation.
Br J Haematol
67
1987
252
7
Hershko
C
Ho
WG
Gale
RP
Cline
MJ
Cure of aplastic anaemia in paroxysmal nocturnal hemoglobulinuria by marrow transfusion from identical twin: Failure of peripheral leucocyte transfusion to correct marrow aplasia.
Lancet
1
1979
945
8
Abrams
RA
Glaubiger
D
Appelbaum
FR
Deisseroth
AB
Result of attempted hematopoietic reconstitution using isologous, peripheral blood mononuclear cells: A Case Report.
Blood
56
1980
516
9
Korbling
M
Burke
P
Braine
H
Elfenbein
G
Santos
GW
Kaizer
H
Successful engraftment of blood derived normal hemopoietic stem cells in chronic myelogenous leukemia.
Exp Hematol
9
1981
684
10
Goldman
JM
Th'ing
KH
Park
DS
Spiers
ASD
Lowenthal
RM
Ruutu
T
Collection, cryopreservation and subsequent viability of haemopoietic stem cells intended for treatment of chronic granulocytic leukaemia in transformation.
Br J Haematol
40
1978
185
11
Korbling M, Fliedner TM: History of blood stem cell transplants. Blood stem cell transplants, in Gale RP, Juttner CA, Henon P (eds): Peripheral Blood Stem Cell Autografts. New York, NY, Cambridge University Press, 1994, p 9
12
Richman
CM
Weiner
RS
Yankee
RA
Increase in circulating stem cells following chemotherapy in man.
Blood
47
1976
1031
13
Lohrmann
HP
Schreml
W
Fliedner
TM
Heimpel
H
Reaction of human granulopoiesis to high does cyclophosphamide therapy.
Blut
38
1979
9
14
Stiff
PJ
Murgo
AJ
Wittes
MF
DeRisi
MF
Clarkson
BD
Quantification of the peripheral blood colony forming unit-culture rise following chemotherapy — Could leukocytaphereses replace bone marrow for autologous transplantation?
Transfusion
23
1983
500
15
To
LB
Haylock
DN
Kimber
RJ
Juttner
CA
High Levels of circulating hemopoietic stem cells in very early remission from acute non-lymphoblastic leukaemia and their collection; and cryopreservation.
Br J Haematol
58
1984
399
16
Reiffers J, Bernard PH, Marit G, Sarrat A, Froideval JL, Broustet A, Vezon G: Collection of blood-derived haemopoietic stem cells and applications for autologous transplantation. Bone Marrow Transplant 1:371, 1986 (suppl 1)
17
To
LB
Sheppard
KM
Haylock
DN
Dyson
PG
Charles
P
Thorpe
DL
Dale
BM
Dart
GW
Roberts
MM
Sage
RE
Juttner
CA
Single high doses of cyclophosphamide enable the collection of high numbers of hemopoietic stem cells from the peripheral blood.
Exp Hematol
18
1989
442
18
Duhrsen
U
Villeval
J-L
Boyd
J
Kannourakis
G
Morstyn
G
Metcalf
D
Effects of recombinant human granulocyte colony-stimulating factor on hematopoietic progenitor cells in cancer patients.
Blood
72
1988
2074
19
Socinski
MA
Cannistra
SA
Elias
A
Antman
KH
Schnipper
L
Griffin
JD
Granulocyte-macrophage colony-stimulating factor expands the circulating haemopoietic progenitor cell compartment in man.
Lancet
1
1988
1194
20
Sheridan
WP
Begley
CG
Juttner
CA
Szer
J
To
LB
Maher
D
McGrath
KM
Morstyn
G
Fox
RM
Effect of peripheral blood progenitor cells mobilized by filgrastim (G-CSF ) on platelet recovery after high does chemotherapy.
Lancet
339
1992
640
21
Gianni
AM
Siena
S
Bregni
M
Tarella
C
Stern
AC
Piler
A
Bonadonna
G
Granulocyte-macrophage colony-stimulating factor to harvest circulating hemopoietic stem cells for autotransplantation.
Lancet
2
1989
580
22
Elias
AD
Ayash
L
Anderson
KC
Hunt
M
Wheeler
C
Schwartz
G
Tepler
I
Mazanet
R
Lynch
C
Pap
S
Mobilization of peripheral blood progenitor cells by chemtherapy and granulocyte macrophage colony stimulating factor for hematologic support after high dose intensification for breast cancer.
Blood
79
1992
3036
23
Fukuda
M
Kojima
S
Matsumoto
K
Matsuyama
T
Autotransplantation of peripheral blood stem cells mobilized by chemotherapy and recombinant human granulocyte colony-stimulating factor in childhood neuroblastoma and non-Hodgkin's lymphoma.
Br J Haematol
80
1992
327
24
Haas
R
Mohle
R
Fruhauf
S
Goldschmidt
H
Witt
B
Flentje
M
Wannenmacher
M
Hunstein
W
Patient characteristics associated with successful mobilizing and autografting of peripheral blood progenitor cells in malignant lymphoma.
Blood
83
1994
3787
25
Schwartzberg
LS
Birch
R
Hazelton
B
Tauer
KW
Lee
P
Altemose
MD
George
C
Blanco
R
Wittlin
F
Cohen
J
Muscato
J
West
WH
Peripheral blood stem cell mobilization by chemotherapy with and without recombinant human granulocyte colony-stimulating factor.
J Hematother
1
1992
317
26
Schwartzberg LS: Peripheral blood stem cell mobilization in the out-patient setting, in Wunder EW, Henon PR (eds): Peripheral Blood Stem Cell Autografts. Heidelberg, Germany, Springer-Verlag, 1993, p 177
27
To
LB
Russell
J
Moore
S
Juttner
CA
Residual Leukaemia cannot be detected in very early remission peripheral blood stem cell collections in acute non-lymphoblastic leukaemia.
Leuk Res
11
1987
327
28
Ross
AA
Cooper
BW
Lazarus
HM
Mackay
W
Moss
TJ
Ciobanu
N
Tallman
MS
Kennedy
J
Davidson
NE
Sweet
D
Winter
C
Akhard
L
Jansen
J
Copelan
E
Meagher
RC
Herzig
RH
Klumpp
TR
Kahn
DG
Warner
NE
Detection and viability of tumour cells in peripheral blood stem cell collections from breast cancer patients using immunocytochemical and clonogenic assay techniques.
Blood
82
1993
2605
29
Ross
AA
Miller
GW
Moss
TJ
Kahn
DG
Warner
NE
Sweet
DL
Louie
KG
Schneidermann
E
Pecora
AL
Meagher
RC
Herzig
RH
Collins
RH
Fay
JW
Immunocytochemical detection of tumour cells in bone marrow and peripheral blood stem cell collections from patients with ovarian cancer.
Bone Marrow Transplant
15
1995
929
30
Brugger
W
Bross
KJ
Glatt
M
Weber
F
Mertelsmann
R
Kanz
L
Mobilization of tumour cells and hematopoietic progenitor cells into peripheral blood of patients with solid tumors.
Blood
83
1994
636
31
Moss
TJ
Cairo
M
Santana
VM
Weinthal
J
Hurvitz
C
Bostrom
B
Clonogenicity of circulating neuroblastoma cells: Implications regarding peripheral blood stem cell transplantation.
Blood
83
1994
3085
32
Moss
TJ
To
LB
Pantel
K
Evaluation of grafts for occult tumor cells.
J Hematother
3
1994
163
33
Bregni
M
Magni
M
Siena
S
Di Nicola
M
Bonadonna
G
Gianni
AM
Human peripheral blood hematopoietic progenitors are optimal targets of retroviral mediated gene transfer.
Blood
80
1992
1418
34
Dunbar
CD
Cottler-Fox
M
O'Shaughnessy
JA
Doren
S
Carter
C
Berenson
R
Brown
S
Moen
RC
Greenblatt
J
Marc
Stewart F
Leitman
SF
Wilson
WH
Cowan
K
Young
NS
Nienhuis
AW
Retrovirally marked CD34-enriched peripheral blood and bone marrow cells contribute to long-term engraftment after autologous transplantation.
Blood
85
1995
3048
35
Berenson
RJ
Bensinger
WI
Hill
RS
Hill
RS
Andrews
RG
Garcia-Lopez
J
Kalamasz
Still BJ
Spitzer
G
Buckner
CD
Bernstein
ID
Thomas
ED
Engraftment after infusion of CD34+ marrow cells in patients with breast cancer or neuroblastoma.
Blood
77
1991
1717
36
Haylock
DN
To
LB
Dowse
TL
Juttner
CA
Simmons
PJ
Ex vivo expansion and maturation of peripheral blood CD34+ cells into the myeloid lineage.
Blood
89
1992
1405
37
Shpall EJ, Jones RB, Bast RC Jr, Johnston CS, Ross M, Anderson I, Peters WP: Immunopharmacologic purging of breast cancer from bone marrow, in Dicke KA, Armitage JO, Decke Evinger MJ (eds): Autologous Bone Marrow Transplantation. Proceedings of the Fifth International Symposium on Autologous Bone Marrow Transplantation. Omaha, NE, The University of Nebraska Medical Center, 1991, p 379
38
Shpall
EJ
Jones
RB
Bearman
SI
Franklin
WA
Archer
PG
Curiel
T
Bitter
M
Claman
HN
Stemmer
SM
Purdy
M
Myers
SE
Hami
L
Taffs
S
Heimfeld
S
Hallagan
J
Berenson
RJ
Transplantation of enriched CD34-positive autologous marrow into breast cancer patients following high-dose chemtherapy: Influence of CD34-positive peripheral-blood progenitors and growth factors on engraftment.
J Clin Oncol
12
1994
28
39
To
LB
Haylock
DN
Dowse
T
Simmons
PJ
Trimboli
S
Ashman
LK
Juttner
CA
A comparative study of the phenotype and proliferative capacity of peripheral blood(PB) CD34+ cells mobilized by four different protocols and those of steady-phase PB and bone marrow CD34+ cells.
Blood
84
1994
2930
40
Simmons PJ, Leavesley DI, Levesque J-P, Swart BW, Haylock DN, To LB, Ashman LK, Juttner CA: The mobilization of primitive hemopoietic progenitors into the peripheral blood. Polyfunctionality of hemopoietic regulators: The Metaclf Forum. Stem Cells 12:187, 1994 (suppl 1)
41
To
LB
Dyson
PG
Juttner
CA
Cell-dose effect in circulating stem cell autografting.
Lancet
2
1986
404
42
Siena
S
Bregni
M
Brando
B
Belli
N
Ravagnani
F
Gandola
L
Stern
AC
Lansdorp
PM
Bonadonna
G
Gianni
AM
Flow cytometry for clinical estimation of circulating hematopoietic progenitors for autologous transplantation in cancer patients.
Blood
77
1991
400
43
To
LB
Roberts
MM
Haylock
DN
Dyson
PG
Branford
AL
Thorp
D
Ho
JQKH
Dart
GW
Davy
MLJ
Olweny
CLM
Abdi
E
Juttner
CA
Comparison of haematological recovery times and supportive care requirements of autologous recovery phase peripheral blood stem cell transplants, autologous bone marrow transplants and allogeneic bone marrow transplants.
Bone Marrow Transplant
9
1992
277
44
Bender
JG
To
LB
Williams
S
Schwartzberg
LS
Defining a therapeutic dose of peripheral blood stem cells.
J Hematother
1
1992
329
45
To LB, Roberts MM, Rawling CM, Dyson PG, Rawling TP, Haylock DN, Juttner CA: Establishment of a clinical threshold cell dose: Correlation between CFU-GM and duration of aplasia, in Wunder E, Sovalat H, Henon PR, Serke S (eds): Hematopoietic Stem Cells: The Mulhouse Manual. Dayton, OH, AlphaMed, 1994, p 15
46
Sutherland
DR
Keating
A
Nayar
R
Anania
S
Stewart
AK
Sensitive detection and enumeration of CD34+ cells in peripheral and cord blood by flow cytometry.
Exp Hematol
22
1994
1003
47
To
LB
Juttner
CA
Stomski
F
Vadas
MA
Kimber
RJ
Immune reconstitution following peripheral blood stem cell autografting (letter).
Bone Marrow Transplant
2
1987
111
48
Roberts
MM
To
LB
Gillis
D
Mundy
J
Rawling
C
Ng
K
Juttner
CA
Immune reconstitution following peripheral blood stem cell transplantation, autologous bone marrow transplantation and allogeneic bone marrow transplantation.
Bone Marrow Transplant
12
1993
469
49
Verbik
DJ
Jackson
JD
Pirruccello
SJ
Patil
KD
Kessinger
A
Joshi
SS
Functional and phenotypic characterization of human peripheral blood stem cell harvests.
Blood
85
1995
1964
50
Russell
N
Gratwohl
A
Schmitz
N
The place of blood stem cells in allogeneic transplantation.
Br J Haematol
93
1996
747
51
Wagner JE: Umbilical cord blood transplantation. Transfusion 35:619,694, 1995
52
Goodman
J
Hodgson
G
Evidence for stem cells in the peripheral blood of mice.
Blood
19
1962
702
53
Cavins
JA
Stuart
CS
Scheer
E
Ferrebee
T
Ferrebee
JW
The recovery of lethally irradiated dogs given infusions of autologous leukocytes preserved at −80 C.
Blood
23
1964
38
54
Micklem
HS
Anderson
N
Ross
R
Limited potential of circulating hemopoietic stem cells.
Nature
256
1975
41
55
Storb
R
Graham
TC
Epstein
RB
Sale
GE
Thomas
ED
Demonstration of hemopoietic stem cells in the peripheral blood of baboons by cross-circulation.
Blood
50
1977
537
56
Cherktov
JL
Gurevitch
OA
Udalov
GA
Self maintenance ability of circulating hemopoietic stem cells.
Exp Hematol
10
1982
90
57
Abrams
RA
McCormack
K
Bowles
C
Deisseroth
AB
Cycolphosphamide treatment expands the circulating hematopoietic stem cell pool in dogs.
J Clin Invest
67
1981
1392
58
McCredie
KB
Hersh
EM
Freireich
EJ
Cells capable of colony formation in the peripheral blood of man.
Science
171
1971
293
59
Lohrmann
HP
Schreml
W
Lang
W
Betzier
M
Fliedner
TM
Heimpel
H
Changes of granulopoiesis during and after adjuvant chemotherapy of breast cancer.
Br J Haematol
40
1978
369
60
Verma
DS
Fisher
R
Spitzer
G
Zander
AR
McCredie
KL
Dicke
KA
Diurnal changes in circulating myeloid progenitor cells in man.
Am J Haematol
9
1980
185
61
Jehn
U
Kern
K
Wachholz
K
Holzel
D
Prognostic value of in vitro growth pattern of colony forming cells in adult acute leukaemia.
Br J Cancer
47
1983
423
62
Hibben
JA
Njoku
OS
Matutes
F
Lewis
SM
Goldman
JM
Myeloid progenitor cells in the circulation of patients with myelofibrosis and other myeloproliferative disorders.
Br J Haematol
57
1984
495
63
Kessinger
A
Armitage
JO
Landmark
JD
Smith
DM
Weisenburger
DD
Reconstitution of human hematopoietic function with autologous cryopreserved circulating stem cells.
Exp Haematol
14
1986
192
64
Kessinger
A
Armitage
JO
Landmark
JD
Smith
DM
Weisenburger
DD
Autologous peripheral hematopoietic stem cell transplantation restores hematopoietic function following marrow ablative therapy.
Blood
71
1988
723
65
Nothdurft
W
Bruch
C
Fliedner
TM
Ruber
E
Studies on the regeneration of the CFUc-population in blood and bone marrow of lethally irradiated dogs after autologous transfusion of cryopreserved mononuclear blood cells.
Scand J Haematol
19
1977
470
66
Carbonell F, Calvo W, Fliedner M, Kratt E, Gerhartz H, Korbling M, Nothdurft W, Ross WM: Cytogenetic studies in dogs after total body irradiation and allogeneic transfusion with cryopreserved blood mononuclear cells: Observations in long-term chimeras: Intern J Cell Cloning 2:81, 1984
67
McCredie B, Freireich EJ, Hersh EM, Curtis JE, Kaizer H, Anderson K: Early bone marrow recovery after chemotherapy following the transfusion of peripheral blood leukocytes in identical twins. Proc Am Assoc Cancer Res 2:11, 1970 (abstr)
68
Valdimarsson
H
Holt
PJL
Moss
PD
Hobbs
JR
Treatment of chronic mucocutaneous candidiasis with leucocytes from HL-A compatible sibling.
Lancet
1
1972
469
69
Cline
MJ
Golde
DW
Mobilization of hematopoietic stem cells (CFU-C) into the peripheral blood of man by endotoxin.
Exp Hematol
5
1977
186
70
Barrett
AJ
Longhurst
P
Sneath
P
Watson
JG
Mobilization of CFU-C by exercise and ACTH induced stress in man.
Exp Hematol
6
1978
590
71
To
LB
Haylock
DN
Juttner
CA
Kimber
RJ
The effect of monocytes on the peripheral blood CFU-c assay system.
Blood
62
1983
112
72
Korbling
M
Fliedner
TM
Pflieger
H
Collection of large quantaties of granulocyte macrophage progenitor cells (CFUc) in man by means of continuous-flow leukapheresis.
Scand J Haematol
24
1980
22
73
To
LB
Dyson
PG
Branford
AL
Russell
JA
Haylock
DN
Ho
JQK
Kimber
RJ
Juttner
CA
Peripheral blood stem cells collected in very early remission produce rapid and sustained autologous haemopoietic reconstitution in acute non-lymphoblastic leukaemia.
Bone Marrow Transplant
2
1987
103
74
Juttner
CA
To
LB
Ho
JQK
Bardy
PG
Dyson
PG
Haylock
DN
Kimber
RJ
Early lympho-haemopoietic recovery after autografting using peripheral blood stem cells in acute non-lymphoblastic leukaemia.
Transplant Proc
20
1988
40
75
Juttner
CA
To
LB
Haylock
DN
Dyson
PG
Thorp
D
Dart
GW
Ho
JQK
Horvath
N
Bardy
P
Autologous blood stem cell transplantation.
Transplant Proc
21
1989
2929
76
Reiffers L, Leverger G, Marit G, Castaigne S, Tilly H, Lepage E, Henon E, Douay L, Troussard X: Hematopoietic reconstitution after autologous blood stem cell transplantation, in Gale RP, Champlin RE (eds): Bone Marrow Transplantation: Current Controversies. Proceedings of Sandoz-UCLA Symposium. New York, NY, Liss, 1988, p 313
77
Molineux
G
Pojda
Z
Hampson
IN
Lord
BI
Dexter
TM
Transplantation potential of peripheral blood stem cells induced by granulocyte colony-stimulating factor.
Blood
76
1990
2153
78
Neben
S
Marous
K
Minch
P
Mobilization of hematopoietic stem and progenitor cell populations from marrow to the blood of mice following cyclophosphamide and/or granulocyte colony-stimulating factor.
Blood
81
1993
1960
79
Yan
X-Q
Hartley
C
McElroy
P
Chang
A
McCrea
McNiece I
Peripheral blood progenitor cells mobilized by recombinant human granulocyte colony-stimulating factor plus recombinant rat stem cell factor contain long-term engrafting cells capable of cellular proliferation for more than two years as shown by serial transplantation in mice.
Blood
85
1995
2303
80
Starzl
TE
Demetris
AJ
Trucco
M
Ricordi
C
Ildstad
S
Terasaki
PI
Murase
N
Kendall
RS
Kocova
M
Rudert
WA
Zeevi
A
Thiel
DV
Chimerism after liver transplantation for type IV glycogen storage disease and type I Gaucher's disease.
N Engl J Med
328
1993
745
81
Dexter TM, Allen TD, Simmons PJ: Marrow biology and stem cells, in Dexter TM, Garland JM, Testa NG (eds): Colony Stimulating Factors: Molecular & Cellular Biology. New York, NY, Dekker, 1990, p 1
82
Tavassoli
M
Hardy
CL
Molecular basis of homing of intravenously transplanted stem cells.
Blood
76
1990
1059
83
Gordon
MY
Haemopoietic progenitor cell binding to the stromal environment in vitro.
Exp Hematol
18
1990
837
84
Verfaillie
C
Blakolmer
K
McGlave
P
Purified primitive human haemopoietic progenitors with long-term in vitro repopulating ability selectively adhere to irradiated bone marrow stroma.
J Exp Med
172
1990
509
85
Long
MW
Blood cell cytoadhesion molecules.
Exp Hematol
20
1992
288
86
Simmons
PJ
Zannettino
A
Gronthos
S
Leavesley
D
Potential adhesion mechanisms for localisation of haemopoietic progenitors to bone marrow stroma.
Leuk Lymphoma
12
1994
353
87
Tsai
S
Differential binding of erythroid and myeloid progenitors to fibroblasts and fibronectin.
Blood
69
1987
1587
88
Simmons
PJ
Masinovsky
B
Longenecker
BM
Berenson
R
Torok-Storb
B
Gallatin
WM
Vascular cell adhesion molecule-1 expressed by bone marrow stromal cells mediates the binding of hematopoietic progenitors.
Blood
80
1992
388
89
To LB: Mobilizing and collecting blood stem cells, in Gale RP, Juttner CA, Henon P (eds): Peripheral Blood Stem Cell Autografts. New York, NY, Cambridge University Press, 1994, p 56
90
Papayannopoulou
T
Nakamoto
B
Peripheralisation of hemopoietic progenitors in primates treated with anti-VLA-4 integrin.
Proc Natl Acad Sci USA
90
1993
9374
91
Mohle
R
Haas
R
Hunstein
W
Expression of adhesion molecules and c-kit on CD34+ hematopoietic progenitor cells: Comparison of cytokine mobilised blood stem cells with normal bone marrow and peripheral blood.
J Hematother
2
1993
483
92
Turner
ML
Regulation of hematopoietic progenitor cell migration, mobilization and homing.
Stem Cells
12
1994
227
93
Liesveld
JL
Winslow
JM
Kempski
MC
Ryan
DH
Brennan
JK
Abboud
CN
Adhesive interactions of normal and leukaemic human CD34+ myeloid progenitors: Role of marrow stromal, fibroblast and cytomatrix components.
Exp Hematol
19
1991
63
94
Teixido
J
Hemler
ME
Greenberger
JS
Anklesaria
P
Role of β1 and β2 integrins in the adhesion of human CD34H1 cells to bone marrow stroma.
J Clin Invest
90
1992
358
95
Williams DA, Rios M, Stephens C, Patel VP: Fibronectin and VLA-4 in haemopoietic stem cell-microenvironment. Nature 352, 1991
96
Jacobson
K
Kravitz
J
Kincade
PW
Osmond
DG
Adhesion receptors on bone marrow stromal cells: In vivo expression of vascular cell adhesion molecule-1 by reticular cells and sinusoidal endothelium in normal and γ-irridiated mice.
Blood
87
1996
73
97
Derskson
MW
Gerritsen
WR
Rodenhuis
S
Dirkson
MKA
Slaper-Contenbach
CM
Schaasberg
W
Pinedo
HM
von dem Borne
AEGK
van der Schoot
CE
Expression of adhesion molecules on CD34+ cells: CD34+ L-selectin+ cells predict a rapid platelet recovery after peripheral blood stem cell transplantation.
Blood
85
1995
3313
98
Kerst
JM
Sanders
JB
Slaper-Cortenbach
ICM
Doorakkers
MC
Hooibrink
B
van Oers
RHJ
von dem Borne
AEGKr
van der Schoot
E
α4β1 and α5β1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way.
Blood
81
1993
344
99
Kovach
NL
Lin
N
Yednock
T
Harlan
JM
Broudy
VC
Stem cell factor modulates activity of α4β1 and α5β1 integrins expressed on hematopoietic cell lines.
Blood
85
1995
59
100
Levesque J-P, Leavesley DI, Niutta S, Vadas M, Simmons PJ: Cytokines increase human hemopoietic cell adhesiveness by activation of very late antigen (VLA)-4 and VLA-5 integrins. J Exp Med 1805, 1995
101
Levesque
J-P
Haylock
DN
Simmons
PJ
Cytokine regulation of proliferation and cell adhesion are correlated events in human CD34+ hemopoietic progenitors.
Blood
88
1996
1168
102
Lesley
J
Hyman
R
CD44 can be activated to function as a hyaluronic acid receptor in normal murine T-cells.
Eur J Immunol
22
1992
2719
103
Cynshi
O
Satoh
K
Shimonaka
Y
Hattori
K
Nomura
H
Imai
N
Hirashima
K
Reduced response to granulocyte colony-stimulating factor in W/WV and SL/SLd mice.
Leukaemia
5
1991
75
104
Leary
AG
Ogawa
M
Blast cell colony assay for umbilical cord blood and adult bone marrow progenitors.
Blood
69
1987
953
105
Coates
TD
Behavioural aspects of neutrophil motility.
Curr Opin Hematol
3
1996
41
106
To LB, Rawling C, Andary C, Rawling T, Haylock A, Thorp D, Dyson P, Juttner CA: The efficacy of sequential/combined IL-3/GM-CSF administration in peripheral blood (PB) progenitor mobilization, Blood 82:319a, 1993 (abstr, suppl 1)
107
Orazi
A
Cattoretli
G
Schiro
R
Siena
S
Bregni
M
Di-Nicola
M
Gianni
AM
Recombinant human interleukin-3 and recombinant human granulocyte-macrophage colony-stimulating factor administered in vivo after high dose cyclophosphamide cancer chemotherapy: Effect on hematopoiesis and microenvironment of bone marrow.
Blood
79
1992
2610
108
Dorudi
S
Hart
IR
Mechanisms underlying invasion and metastasis.
Curr Opin Oncol
5
1993
130
109
Rowlings
PA
Rawling
CA
To
LB
Bayly
JL
Juttner
CA
A comparison of peripheral blood stem cell mobilization after chemotherapy with cyclophosphamide as a single agent in doses of 4 g/m2 in patients with advanced cancer.
Aust NZ J Med
22
1992
600
110
Kotasek
DD
Shepherd
KM
Sage
RE
Dale
BM
Norman
JE
Charles
P
Gregg
CA
Pillow
A
Bolton
A
Factors affecting blood stem cell collections following high dose cyclophosphamide mobilization in lymphoma, myeloma and solid tumors.
Bone Marrow Transplant
9
1992
11
111
Jagannath
S
Vesole
DH
Glenn
L
Crowley
J
Barlogie
B
Low risk intensive therapy for-multiple myeloma with combined autologous bone marrow and blood stem cell support.
Blood
80
1992
1666
112
Gianni
AM
Bregni
M
Siena
S
Orazi
A
Stern
C
Gondola
L
Bonadonna
G
Recombinant human granulocyte-macrophage colony-stimulating factor reduces hematologic toxicity and widens clinical applicability of high-dose cyclophosphamide treatment in breast cancer and non-Hodgkin's lymphoma.
J Clin Oncol
8
1990
768
113
Brugger
W
Bross
K
Frisch
J
Dern
P
Weber
B
Mertelsmann
R
Kanz
L
Mobilization of peripheral blood progenitor cells by sequential administration of interleukin-3 and granulocyte-macrophage colony-stimulating factor following polychemo-therapy with etoposide, ifosfamide and cisplatin.
Blood
70
1992
1193
114
Pettengell
R
Morgenstern
GR
Woll
PJ
Chang
J
Rowlands
M
Young
R
Radford
JA
Scarffe
JH
Testa
NG
Crowther
D
Peripheral blood progenitor cell transplantation in lymphoma and leukaemia using a single leukapheresis.
Blood
82
1993
3770
115
Haynes
A
Hunter
A
McQuaker
G
Anderson
S
Bienz
N
Russell
NH
Engraftment characteristics of peripheral blood stem cells mobilised with cyclophosphamide and the delayed addition of G-CSF.
Bone Marrow Transplant
16
1995
359
116
Weaver
CH
Hazelton
B
Birch
R
Palmer
P
Allen
C
Schwartzberg
West W
An analysis of engraftment kinetics as a function of the CD34 content of peripheral blood progenitor cell collections in 692 patients after the administration of myeloablative chemotherapy.
Blood
86
1995
3961
117
Abboud CN, Reykdal S, Liesveld JL, Belanger TJ, Haug JS, Rosell KE, Kempski MC, Flesher WR, DiPersio JF: Prospective randomized trial (NCI/92-0010), comparing the efficacy of hematopoietic growth factors for mobilizing peripheral blood stem cells (PBSC) in autologous bone marrow transplantation: II. Progenitor mobilization kinetics. Blood 86:463a, 1995 (abstr, suppl 1)
118
Winter JN, Lazarus HM, Rademaker AF, Bauman A, Cooper B, Thomas R, Gordon LI, Tallman MS, Rubin H, Gerson S, Miller LL: Comparison of PIXY321 and GM-CSF for mobilization of peripheral blood progenitor cells (PBPC) in advanced breast cancer. Blood 86:578a, 1995 (abstr, suppl 1)
119
DeLuca
E
Sheridan
WP
Watson
D
Szer
J
Begley
CG
Prior chemotherapy does not prevent effective mobilisation by G-CSF of peripheral blood progenitor cells.
Br J Cancer
66
1992
893
120
Demuynck
H
Pettengell
R
deCampos
E
Dexter
TM
Testa
NG
The capacity of peripheral blood stem cells mobilised with chemotherapy plus G-CSF to repopulate irradiated marrow stroma in vitro is similar to that of bone marrow.
Eur J Cancer
28
1992
381
121
Bensinger
W
Singer
J
Appelbauf
F
Lilleby
K
Longin
K
Rowley
S
Clarke
ER
Clift
R
Hansen
J
Shields
T
Storb
R
Weaver
C
Weiden
P
Buckner
CD
Autologous transplantation with peripheral blood mononuclear cells collected after administration of recombinant granulocyte colony stimulating factor.
Blood
81
1993
3158
122
Chao
NJ
Schriber
JR
Grimes
K
Long
GD
Negrin
RS
Raimondi
CM
Horning
SJ
Brown
SL
Miller
L
Blume
KG
Granulocyte colony-stimulating factor “mobilized” peripheral blood progenitor cells accelerate granulocyte and platelet recovery after high-dose chemotherapy.
Blood
81
1993
2031
123
Basser
RL
To
LB
Begley
CG
Juttner
CA
Maher
DW
Szer
J
Cebon
J
Collins
J
Russell
I
Fox
RM
Sheridan
WP
Green
MD
Adjuvant treatment of women with high risk breast cancer using multiple cycles of high-dose chemotherapy supported by filgrastim (G-CSF )-mobilised peripheral blood progenitor cells.
Clin Cancer Res
1
1995
715
124
Schmitz
N
Dreger
P
Suttorp
M
Rohwedder
EB
Haferlach
T
Loffler
H
Hunter
A
Russell
NH
Primary transplantation of allogeneic peripheral blood progenitor cells mobilized by filgrastim (granulocyte colony-stimulating factor).
Blood
85
1995
1666
125
Korbling
M
Huh
YO
Durett
A
Mirza
N
Miller
P
Engel
H
Anderlini
P
van Besien
K
Andreeff
M
Przepiorka
D
Deisseroth
AB
Champlin
RE
Allogeneic Schmitz N, Dreger P, Suttorp M, Rohwedder EB, Haferlach T, Loffler H, Hunter blood stem cell transplantation: Peripheralization and yield of donor-derived primitive hematopoietic progenitor cells (CD34+ dim) and lymphoid subsets, and possible predictors of engraftment and graft-versus-host disease.
Blood
86
1995
2842
126
Grigg
AP
Roberts
AW
Raunow
H
Houghton
S
Layton
JE
Boyd
AW
McGrath
KM
Maher
D
Optimizing dose and scheduling of filgratism (granulocyte colony-stimulating factor) for mobilization and collection of peripheral blood progenitor cells in normal volunteers.
Blood
86
1995
4437
127
Harada
M
Nagafuji
K
Fujisaki
T
Kubota
A
Mizuno
S-I
Takenaka
K
Miyamoto
T
Ohno
T
Gondo
H
Kuroiwa
M
Okamura
T
Inaba
S
Niho
Y
G-CSF–induced mobilization of perpheral blood stem cells from healthy adults for allogeneic transplantation.
J Hematother
5
1996
63
128
Bensinger
W
Weaver
FR
Appelbaum
FR
Rowley
S
Demirer
J
Sanders
R
Storb
R
Buckner
CD
Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony-stimulating factor.
Blood
85
1995
1655
129
Hoglund
M
Smedmyr
B
Simonsson
B
Totterman
T
Bengtsson
M
Dose-dependent mobilisation of haematopoietic progenitor cells in healthy volunteers receiving glycosylated rHuG-CSF.
Bone Marrow Transplant
18
1996
19
130
Waller
CF
Bertz
H
Wenger
MK
Fetscher
S
Hardung
M
Engelhardt
M
Behringer
D
Lange
W
Mertelsmann
R
Finke
J
Mobilization of peripheral blood progenitor cells for allogeneic transplantation: Efficacy and toxicity of a high-dose rhG-CSF regimen.
Bone Marrow Transplant
18
1996
279
131
Mire-Sluis
AR
Das
RG
Thorpe
R
The international standard for granulocyte colony stimulating factor (G-CSF ). Evaluation in an international collaborative study.
J Immunol Methods
179
1995
117
132
Gisselbrecht
C
Prentice
G
Bacigalupo
A
Biron
P
Milpied
N
Rubie
H
Cunningham
D
Legros
M
Pico
JL
Linch
DC
Burnett
AK
Scarffe
JH
Siegert
W
Yver
A
A phase III randomised placebo-controlled study of lenograstim (glycosylated rHuG-CSF ) in 315 paediatric and adult autologous or allogeneic bone marrow transplant patients.
Lancet
343
1994
696
133
Hoglund M, Bengesson M, Cour-Chabernaud Y, Dabouz-Harrouche F, Simonsson B, Smedmyr B, Torrerman T: Glycosylated rHuG-CSF is more potent than non-glycosylated rHuG-CSF in mobilisation of peripheral blood progenitor cells (PBPC) in healthy volunteers. Blood 86:464a, 1995 (abstr, suppl 1)
134
Andrews
G
Knitter
GH
Bartelmex
SH
Langley
KE
Farrar
D
Hendren
RW
Appelbaum
FR
Bernstein
ID
Zsebo
KM
Recombinant human stem cell factor, a c-kit ligand, stimulates hematopoiesis in primates.
Blood
78
1991
1975
135
Andrews
RG
Bensinger
WI
Knitter
GH
Bartelmez
SH
Longin
K
Bornstein
ID
Appelbaum
FR
Zsebo
KR
The ligand for c-kit, stem cell factor, stimulates the circulation of cells that engraft lethally irradiated baboons.
Blood
80
1992
2715
136
Briddell
RA
Hartley
CA
Smith
KA
McNiece
IK
Recombinant rat stem cell factor synergizes with recombinant human granulocyte colony-stimulating factor in vivo in mice to mobilize peripheral blood progenitor cells that have enhanced repopulating potential.
Blood
82
1993
1720
137
Andrews
RG
Briddell
RA
Knitter
GH
Opie
T
Bronsden
M
Myerson
D
Appelbaum
FR
McNiece
IK
In vivo synergy between recombinant human stem cell factor and recombinant human granulocyte colony-stimulating factor in baboons: Enhanced circulation of progenitor cells.
Blood
84
1994
800
138
Basser R, Begley CG, Mansfield R, To LB, Juttner C, Maher D, Fox R, Cebon J, Szer J, Grigg A, Clark K, Marty J, Menchaca D, Thompson B, Russell I, Collins J, Green M: Mobilization of PBPC by priming with stem cell factor (SCF ) before filgratim compared to concurrent administration. Blood 86:687a, 1995 (abstr, suppl 1)
139
Begley CG, Basser R, Mansfield R, Maher B, To LB, Juttner CA, Fox R, Cebon J, Grigg A, Szer J, McGrath K, Thomson B, Sheridan W, Menchaca D, Collins J, Russell I, Green M: Randomized prospective study demonstrating a prolonged effect of SCF with G-CSF (Filgrastim) on PBPC in untreated patients: Early results. Blood 84:25a, 1994 (abstr, suppl 1)
140
Glaspy J, LeMaistre CF, Lill M, Jones R, Moore R, Briddell, Menchaca D, Turner S, Shpall EJ: Dose-response of 7 day administration of recombinant methionyl human stem cell factor (SCF ) in combination with filgrastim (G-CSF ) for progenitor cell mobilization in patients with stage II-IV breast cancer. Blood 86:463a, 1995 (abstr, suppl 1)
141
Haas
R
Ho
AD
Bredthauer
U
Cayeux
Egerer G
Knauf
W
Hunstein
W
Successful autologous transplantation of blood stem cells mobilized with recombinant human granulocyte-macrophage colony-stimulating factors.
Exp Hematol
18
1990
94
142
Aglietta
M
Piacibello
W
Sanavio
F
Stacchini
A
Apra
F
Schena
M
Mossetti
C
Carnino
F
Caligaris-Cappio
F
Gavosto
F
Kinetics of human hemopoietic cells after in vivo administration of granulocyte-macrophage colony-stimulating factor.
J Clin Invest
83
1995
551
143
Villeval
J-L
Dührsen
U
Morstyn
G
Metcalf
D
Effect of recombinant human granulocyte-macrophage colony stimulating factor on progenitor cells in patients with advance malignancies.
Br J Haematol
74
1990
36
144
Peters
WP
Rosner
G
Ross
M
Vredenburgh
J
Meisenberg
B
Gilbert
C
Kurtzberg
J
Comparative effects of granulocyte-macrophage colony-stimulating factor (GM-CSF ) and granulocyte colony-stimulating factor (G-CSF ) on priming peripheral blood progenitor cells for use with autologous bone marrow after high-dose chemotherapy.
Blood
81
1993
1709
145
Lopez
AF
To
LB
Yang
YC
Gamble
JR
Shannon
MF
Burns
GF
Dyson
PG
Juttner
CA
Clark
S
Vadas
MA
Stimulation of proliferation, differentiation and function of human cells by primate interleukin-3.
Proc Natl Acad Sci USA
84
1987
2761
146
Ottmann
OG
Ganser
A
Seipelt
G
Elder
M
Schulz
G
Hoelzer
D
Effects of recombinant human Interleukin-3 on human hematopoietic progenitor and precursor cells in vivo.
Blood
76
1990
1494
147
Vose JM, Kessinger A, Bierman PJ, Sharp G, Garrison L, Armitage JO (Omaha, NE, USA/Seattle, WA, USA): The use of rhIL-3 for mobilization of peripheral blood stem cells in previously treated patients with lymphoid malignancies. Int J of Cell Cloning 10:62, 1992 (suppl 1)
148
Geissler
K
Valent
P
Mayer
P
Liehl
E
Hinterberger
W
Lechner
K
Bettelheim
P
Recombinant human interleukin-3 expands the pool of circulating hematopoietic progenitor cells in primates and synergism with recombinant granulocyte/macrophage colony-stimulating factor.
Blood
75
1990
2305
149
Ghielmini
M
Pettengell
R
Coutinho
LH
Testa
N
Crowther
D
The effect of the GM-CSF/IL-3 fusion protein PIXY 321 on bone marrow and circulating haemopoietic cells of previously untreated patients with cancer.
Br J Haematol
93
1996
6
150
Brasel K, McKenna HJ, Charrier K, Morrissey P, Williams DE, Lyman SD: Synergistic effects in vivo of flt3 ligand with GM-CSF of G-CSF in mobilization of colony forming cells in mice. Blood 86:499a, 1995 (abstr, suppl 1)
151
Lord
BI
Woolford
LB
Wood
LM
Czaplewski
LG
McCourt
M
Hunter
MG
Edwards
RM
Mobilization of early hematopoietic progenitor cells with BB-10010: A genetically engineered variant of human macrophage inflammatory protein-1α.
Blood
85
1995
3412
152
Ganser
A
Bergmenn
M
Völkers
B
Grützmacher
P
Scigalla
P
Hoelzer
D
In vivo effects of recombinant human erythropoietin on circulating human hematopoietic progenitor cells.
Exp Hematol
17
1989
433
153
Pettengell
R
Woll
PJ
Chang
J
Coutinho
L
Crowther
D
Testa
NG
Effects of erythropoietin on mobilisation of haemopoietic progenitor cells.
Bone Marrow Transplant
14
1994
125
154
Fibbe
WE
Hamilton
MS
Laterveer
LL
Kibbelaar
RE
Falkenburg
JH
Visser
JW
Willemze
R
Sustained engraftment of mice transplanted with IL-1 primed blood-derived stem cells.
J Immunol
148
1992
417
155
Laterveer
L
Lindley
IJD
Heemskerk
DPM
Camps
JAJ
Pauwels
EKJ
Willemze
R
Fibbe
WE
Rapid mobilization of hematopoietic progenitor cells in rhesus monkeys by a single intravenous injection of interleukin-8.
Blood
87
1996
781
156
Schaafsma
MR
Fibbe
WE
Van Der Harst
D
Duinkerken
N
Brand
A
Osanto
S
Franks
CR
Willemze
R
Falkenburg
JHF
Increased numbers of circulating haematopoietic progenitor cells after treatment with high-dose interleukin-2 in cancer patients.
Br J Haematol
76
1990
180
157
To LB, Haylock DN, Dyson P, Simmons P, Juttner C: Chemotherapy-based approaches to mobilization of progenitor cells, in Morstyn G, Sheridan W (eds): Cell Therapy Stem Cell Transplantation, Gene Therapy, and Cellular Immunotherapy 9. Cambridge, Cambridge University Press, 1996, p 130
158
Tarella
C
Boccardoro
M
Omede
P
Bondesan
P
Caracciolo
D
Frierei
R
Bregni
M
Siena
S
Gianni
AM
Pileri
A
Role of chemotherapy and GM-CSF on hemopoietic progenitor cell mobilization in multiple myeloma.
Bone Marrow Transplant
11
1993
271
159
Chabannon
C
Le Coroller
A-G
Faucher
C
Novakovitch
G
Blaise
D
Moatti
JP
Maraninchi
D
Mannoni
P
Patient condition affects the collection of peripheral blood progenitors after priming with recombinant granulocyte colony-stimulating factor.
J Hematother
4
1995
171
160
Tricot
G
Jagannath
S
Vesole
D
Nelson
J
Tindle
S
Miller
L
Cheson
B
Crowley
J
Barlogie
B
Peripheral blood stem cell transplants for multiple myeloma: Identification of favorable variables for rapid engraftment in 225 patients.
Blood
85
1995
588
161
Dreger
P
Klöss
M
Petersen
B
Haferlach
T
Löffler
H
Loeffler
M
Schmitz
N
Autologous progenitor cell transplantation: Prior exposure to stem cell-toxic drugs determines yield and engraftment of peripheral blood progenitor cell but not of bone marrow grafts.
Blood
86
1995
3970
162
Tarella
C
Caracciolo
D
Gavarotti
P
Bondesan
P
Cherasco
C
Omedè
P
Bregni
M
Siena
S
Gianni
AM
Pileri
A
Circulating progenitors following high-dose sequential (HDS) chemotherapy with G-CSF: Short intervals between drug courses severely impair progenitor mobilization.
Bone Marrow Transplant
16
1995
223
163
Fruehauf
S
Haas
R
Conradt
C
Murea
S
Witt
B
Mohle
R
Hunstein
W
Peripheral blood progenitor cell (PBPC) counts during steady-state hematopoiesis allow to estimate the yield of mobilized PBPC after filgrastim (R-metHuG-CSF )-supported cytotoxic chemotherapy.
Blood
85
1995
2619
164
Holdrinet
RSG
Egmond
JV
Wessels
JMC
Haaanen
C
A method for quantification of peripheral blood mixture in bone marrow aspirates.
Exp Hematol
8
1980
103
165
Parmentier
C
Droz
P
Tubiana
M
Ways of expressing results of human bone marrow progenitor cell culture.
Br J Haematol
40
1978
105
166
Gordon
MY
Douglas
IDC
Clink
HM
Pickering
BM
Distribution of granulopoietic activity in the human skeleton, studied by colony growth in agar diffusion chambers.
Br J Haematol
32
1976
537
167
Kospe
WH
Rayudu
VMS
Cardello
M
Friedman
AM
Fordham
EW
Bone marrow scanning with 52iron: Regeneration and extension of marrow after ablative doses of radiotherapy.
Cancer
37
1976
1432
168
Lie
AKW
Rawling
TP
Bayly
JL
To
LB
Progenitor cell yield in sequential blood stem cell mobilization in the same patients: Insights into chemotherapy dose escalation and combination of haemopoietic growth factor and chemotherapy.
Br J Haematol
95
1996
39
169
Morley
A
Blake
J
An animal model of chronic aplastic marrow failure. I. Late marrow failure after busulfan.
Blood
44
1974
49
170
Botnick
LE
Hannon
EC
Hellman
S
Multisystem stem cell failure after apparent recovery from alkylating agents.
Cancer Res
38
1978
1942
171
Bradwein
JM
Callum
J
Sutcliffe
SBV
Scott
JG
Keating
A
Analysis of factors affecting hematopoietic recovery after autologous bone marrow transplantation for lymphoma.
Bone Marrow Transplant
6
1990
291
172
To
LB
Is our current strategy in manipulating hemopoiesis in autologous transplantation correct?
Stem Cells
11
1993
283
173
Moore
MAS
Does stem cell exhaustion result from combining hematopoietic growth factors with chemotherapy? If so, how do we prevent it?
Blood
80
1992
3
174
Hillyer
CD
Large volume leukapheresis to maximize peripheral blood stem cell collection.
J Hematother
2
1993
529
175
Jones
HM
Jones
SA
Watts
MJ
Khwaja
A
Mills
W
Fielding
A
Goldstone
AH
Linch
DC
Development of a simplified single leukapheresis approach for peripheral blood progenitor cell transplantation in previously treated patients with lymphoma.
J Clin Oncol
12
1994
1693
176
Siena
S
Bregni
M
Brando
B
Ravagnani
F
Bonadonna
G
Gianni
AM
Circulation of CD34+ hematopoietic stem cells in the peripheral blood of high-dose cyclophosphamide-treated patients: Enhancement by intravenous recombinant human granulocyte-macrophage colony-stimulating factor.
Blood
74
1989
1905
177
Wunder
E
Solovot
H
Fritsch
G
Silvestri
F
Henon
P
Serke
S
Report of the European workshop on peripheral blood blood stem cell determination and standardization-Mulhouse, France.
J Hematother
1
1992
131
178
Andrews
RG
Singer
JW
Bernstein
ID
Precursors of colony-forming cells in human can be distinguished from colony-forming cells by expression of the CD33 and CD34 antigens and light scatter properties.
J Exp Med
169
1992
1721
179
Srour
EF
Brandt
JE
Leemhuis
T
Van Besien
K
Hoffman
R
Simulaneous use of CD34, Cd15, anti-HLA-DR and rhodamine 123 for the isolation of precursors of human hematopoietic progenitor cells.
Exp Hematol
18
1990
549
180
Lansdorp
PM
Sutherland
HJ
Eaves
CJ
Selsctive expression of CD45 isoforms on functional subpopulations of CD34+ hematopoietic cells from human bone marrow.
J Exp Med
172
1990
363
181
Terstappen
LWM
Huang
S
Safford
M
Lansdorp
PM
Loken
MR
Sequential generations of hematopoietic colonies derived from single nonlineage-committed CD34+ CD38− progenitor cells.
Blood
77
1991
1218
182
Bender
JG
Unverzagt
KL
Walker
DE
Lee
W
Lum
L
Van Epps
DE
Stewart
CC
To
LB
Identification and comparison of CD34+ cells and their subpopulations from normal peripheral blood and bone marrow using multicolor flow cytometry.
Blood
77
1991
2591
183
Bender
JG
Williams
SF
Myers
S
Nottleman
D
Lee
WJ
Unverzagt
KL
Walker
D
To
LB
Van Epps
DE
Characterization of chemotherapy mobilized peripheral blood progenitor cells for use in autologous stem cell transplantation.
Bone Marrow Transplant
10
1992
281
184
Hohaus
S
Goldschmidt
H
Ehrhardt
R
Haas
R
Successful autografting following myeloablative conditioning therapy with blood stem cells mobilsed by chemotherapy plus rhG-CSF.
Exp Hematol
21
1993
508
185
Craig
W
Kay
R
Cutler
RL
Lansdorp
PM
Expression of Thy-1 on human hematopoietic progenitor cells.
J Exp Med
177
1993
1331
186
Haas
R
Mohle
R
Murea
S
Goldsmidt
H
Pforsich
M
Witt
M
Hunstein
W
Characterisation of peripheral blood progenitor cells mobilised by cytotoxic chemotherapy and recombinant granulocyte colony-stimulating factor.
J Hematother
3
1994
323
187
Murray
L
Chen
B
Galy
A
Chen
S
Tushinski
R
Uchida
N
Negrin
R
Tricot
G
Jagannath
S
Vesole
D
Barlogie
B
Hoffman
R
Tsukomoto
A
Enrichment of human hematopoietic stem cell activity in the CD34+Thy-1+ Lin− subpopulation from mobilised peripheral blood.
Blood
85
1995
368
188
Stewart
AK
Keating
IA
Anania
S
Nayar
R
Sutherland
R
Optimising the CD34+ and CD34+Thy-1+ stem cell content of peripheral blood collections.
Exp Hematol
23
1995
1619
189
Haas
R
Mohle
R
Pforsich
M
Fruehauf
S
Witt
B
Goldsmidt
H
Huntsein
W
Blood derived autografts collected during granulocyte colony-stimulating factor-enhanced recovery are enriched with early Thy-1+ hematopoietic progenitor cells.
Blood
85
1995
1936
190
Humeau
L
Bardin
F
Maroc
C
Alario
T
Galindo
R
Mannoni
P
Chabannon
C
Phenotypic, molecular and functional characterisation of human peripheral blood CD34+/Thy1+ cells.
Blood
87
1996
949
191
Tong
J
Hoffman
R
Siena
S
Srour
S
Bregni
EF
Bregni
M
Gianni
AM
Characterization and quantitation of primitive hematopoietic progenitor cells present in peripheral blood autografts.
Exp Hematol
22
1994
1016
192
Roberts
AW
Metcalf
D
Noncycling state of peripheral blood progenitor cells mobilized by granulocyte colony-stimulating factor and other cytokines.
Blood
86
1995
1600
193
Siena
S
Bregni
M
Bonsi
L
Sklenar
I
Bagnara
GP
Bonadonna
G
Gianni
AM
Increase in peripheral blood megakaryocyte progenitors following cancer therapy with high-dose cyclophosphamide and hematopoietic growth factors.
Exp Hematol
21
1993
1583
194
Dyson
PG
Jackson
KA
McClure
BJ
Rawling
TP
To
LB
Increased leels of megakaryocyte progenitors in peripheral blood mobilised by chemotherapy and/or haemopoietic growth factors protocols.
Bone Marrow Transplant
18
1996
705
195
Takamatsu
Y
Harada
M
Teshima
T
Makino
S
Inaba
S
Akashi
K
Shibuya
T
Niho
Y
Relationship of infused CFU-GM and CFU-Mk mobilised by chemotherapy with or without G-CSF to platelet recovery after autologous blood stem cell transplantation.
Exp Hematol
23
1995
8
196
Galy
AHM
Webb
S
Cen
D
Murray
LJ
Condino
J
Negrin
RS
Chen
BP
Generation of T cells from cytokine-mobilised peripheral blood and adult bone marrow CD34+ cells.
Blood
84
1994
104
197
Dooley
DC
Law
P
Detection and quantitation of long-term culture initiating cells in normal human peripheral blood.
Exp Hematol
20
1992
156
198
Udomsaki
C
Lansdorp
PM
Hogge
DE
Eaves
AC
Eaves
CJ
Characterisation of primitive hematopoietic cells in normal human peripheral blood.
Blood
80
1992
2513
199
Sutherland
HJ
Eaves
CJ
Lansdorp
PM
Phillips
GL
Hogge
DE
Kinetics of committed and primitive blood progenitor mobilisation after chemotherapy and growth factor treatment and their use in autotransplants.
Blood
83
1994
3808
200
Tong
J
Gianni
AM
Siena
S
Srour
EF
Bregni
M
Hoffman
R
Primitive hematopoietic progenitor cells are present in peripheral blood autografts.
Blood Cells
20
1994
351
201
Siena
S
Bregni
M
Di Nicoa
M
Ravagani
F
Peccatori
F
Gandola
L
Lombardi
F
Tarella
C
Bonadonna
G
Gianni
AM
Durability of hematopoiesis following autografting with peripheral blood hematopoietic progenitors.
Ann Oncol
5
1994
935
202
Silva
MRG
Parreira
A
Ascensão
JL
Natural killer cell numbers and activity in mobilized peripheral blood stem cell grafts: Conditions for in vitro expansion.
Exp Hematol
23
1995
1676
203
Lopez
M
Mortel
O
Pouillart
P
Zucker
JM
Fechtenbaum
J
Douay
L
Palangie
T
Michon
J
Salmon
D
Gorin
NC
Acceleration of hemopoietic recovery after autologous bone marrow transplantation by low doses of peripheral blood stem cells.
Bone Marrow Transplant
7
1991
173
204
Takamatsu
Y
Akashi
K
Harada
M
Teshima
T
Inaba
S
Shimoda
K
Eto
T
Shibuya
T
Okamura
S
Niho
Y
Cytokine production by peripheral blood monocytes and T cells during haemopoietic recovery after intensive chemotherapy.
Br J Haematol
83
1993
21
205
Testa
U
Martucci
R
Rutella
S
Scambia
G
Sica
S
Panici
B
Pierelli
L
Menichella
G
Leone
G
Mancuso
S
Peschle
C
Autologous stem cell transplantation: Release of early and late acting growth factors relates with hematopoietic ablation and recovery.
Blood
84
1994
3532
206
Kolb
H-J
Schattenberg
A
Goldman
JM
Hertenstein
B
Jacobsen
N
Arcese
W
Ljungman
P
Ferrant
A
Verdonck
L
Niederwieser
D
Van Rhee
F
Mittermueller
J
deWitte
T
Holler
E
Ansari
H
for the European Group for Blood and Marrow Transplantation Working Party Chronic Leukaemia
Graft-versus-leukaemia effect of donor lymphocyte transfusions in marrow grafted patients.
Blood
86
1995
2041
207
Lewis
ID
Rawling
T
Dyson
PG
Haylock
DN
Juttner
CA
To
LB
Standardisation of the CFU-GM Assay Using Hemopoietic Growth Factors.
J Hematother
5
1996
625
208
Siena
S
Bregni
M
Brando
B
Belli
N
Landsdorp
PM
Bonnadonna
G
Gianni
M
Flow cytometry to estimate circulating hematopoietic progenitors for autologous transplantation: Comparative analysis of different CD34 monoclonal antibodies.
Haematologica
76
1991
330
209
Bender
JG
Unverzagt
K
Flow cytometric analysis of peripheral blood stem cells.
J Hematother
2
1993
421
210
Serke
S
Huhn
D
Quantification of blood CD34-positive cells (letter to the editor).
Blood
80
1992
1628
211
Kressig
C
Kirsch
A
Serke
S
Characterisation and measurement of CD34-expressing hematopoietic cells.
J Hematother
3
1994
263
212
Chen
CH
Lin
W
Shye
S
Kibler
R
Grenier
K
Recktenwald
D
Terstappen
LWMM
Automated enumeration of CD34+ cells in peripheral blood and bone marrow.
J Hematother
3
1994
3
213
Sutherland
DR
Anderson
L
Keeney
M
Nayar
Chin-Yee I
The ISHAGE guidelines for CD34+ cell determination by flow cytometry.
J Hematother
5
1996
213
214
Sutherland
DR
Assessment of peripheral blood stem cell grafts by CD34+ cell enumeration: Toward a standardized flow cytometric approach.
J Hematother
5
1996
209
215
Brecher
ME
Sims
L
Schmitz
J
Shea
T
Bentley
SA
North American Multicentre study on flow cytometric enumeration of CD34+ hematopoietic stem cells.
J Hematother
5
1996
227
216
Johnsen
HE
Knudsen
LM
Nordic flow cytometry standards for CD34+ cell enumeration in blood and leukapheresis products: report from the second Nordic workshop.
J Hematother
5
1996
237
217
Juttner
CA
To
LB
Ho
JQK
Thorp
DL
Kimber
RJ
Successful peripheral blood stem-cell autograft with a near critical dose of myeloid progenitor cells in acute non-lymphoblastic leukaemia in relapse.
Med J Aust
147
1987
292
218
To
LB
Haylock
DN
Dyson
PG
Thorp
D
Roberts
MM
Juttner
CA
An unusual pattern of haemopoietic reconstitution in patients with acute myeloid leukaemia transplanted with autologous recovery phase peripheral blood.
Bone Marrow Transplant
6
1990
109
219
To LB, Haylock DN, Dyson PG, Rawling C, Simmons PJ, Juttner CA: Progenitor threshold effects in haemopoietic reconstitution. Autologous Marrow and Blood Transplantation. 1995 The Cancer Treatment Research and Educational Institute, Arlington, TX, IX:511, 1994
220
Sheridan
WP
Begley
CG
To
LB
Grigg
A
Szer
J
Maher
D
Green
MD
Rowlings
PA
McGrath
KM
Cebon
J
Dyson
P
Watson
D
Bayly
J
deLuca
E
Tomita
D
Hoffman
E
Morstyn
Juttner CA
Phase II study of autologous filgrastim (G-CSF )-mobilized peripheral blood progenitor cells to restore hemopoiesis after high-dose chemotherapy for lymphoid malignancies.
Bone Marrow Transplant
14
1994
105
221
Kawana
Y
Takaue
Y
Watanabe
T
Saito
S
Hirao
A
Abe
T
Sato
J
Ninomiya
T
Shimokawa
T
Yokobayashi
A
Asana
S
Masaoka
T
Takaku
F
Kuroda
Y
Effects of progenitor cell dose and preleukapheresis use of human recombinant granulocyte colony-stimulating factor on the recovery of hematopoiesis after blood stem cell autografting in children.
Exp Hematol
21
1993
103
222
Roberts
MM
Dyson
PG
Willson
K
Juttner
CA
To
LB
Peripheral blood stem cells mobilized from patients with acute myeloid leukaemia have different platelet roepopulating ability to those mobilised from patients with other diseases.
Bone Marrow Transplant
18
1996
41
223
Schimazaki
C
Oku
N
Uchiyama
H
Yamagata
N
Tatsumi
T
Hirata
T
Ashihara
E
Okawa
K
Goto
H
Inaba
T
Fujita
N
Haruyama
H
Nakagawa
M
Effect of granulocyte colony-stimulating factor on haematopoietic recovery after peripheral blood progenitor cell transplantation.
Bone Marrow Transplant
13
1994
271
224
Smith
SL
Bender
JG
Maples
PB
Unverzagt
K
Schilling
M
Lum
L
Williams
S
Van Epps
DE
Expansion of neutrophil precursors and progenitors in suspension cultures of CD34+ cells enriched from human bone marrow.
Exp Haematol
21
1993
870
225
Haylock
DN
Makino
S
Dowse
TL
Trimboli
S
Niutta
S
To
LB
Juttner
CA
Simmons
PJ
Ex vivo hematopoietic progenitor cell expansion.
Immunomethods
5
1994
217
226
Schwartz
RM
Palsson
BO
Emerson
SG
Rapid medium perfusion rate significantly increases the productivity and longevity of human bone marrow cultures.
Proc Natl Acad Sci USA
88
1991
6760
227
Shapiro
F
Yao
T-J
Raptis
G
Reich
L
Norton
L
Moore
MAS
Optimization of conditions for ex-vivo expansion of CD34+ cells from patients with stage IV breast cancer.
Blood
84
1994
3567
228
Williams
SF
Lee
WJ
Bender
JG
Zimmerman
T
Swinney
P
Blake
M
Carreon
J
Schilling
M
Smith
S
Williams
DE
Oldham
F
Van Epps
D
Selection and expansion of peripheral blood CD34+ cells in autologous stem cell transplantation for breast cancer.
Blood
87
1996
1687
229
Brugger
W
Heimfeld
S
Berenson
RJ
Mertelsmann
R
Kanz
L
Reconstitution of hematopoiesis after high-dose chemotherapy by autologous progenitor cells generated ex-vivo.
N Engl J Med
333
1995
283
230
Beyer
J
Schwella
N
Zingsem
J
Strohscheer
I
Schwaner
I
Oettle
H
Serke
S
Huhn
D
Siegert
W
Hematopoietic rescue after high-dose chemotherapy using autologous peripheral-blood progenitor cells or bone marrow: A randomized comparison.
J Clin Oncol
13
1995
1328
231
Qiao
X
Loudovaris
M
Unverzagt
K
Walker
DE
Smith
SL
Martinson
J
Schilling
M
Lee
W
Williams
SF
Van Epps
DE
Cohen
I
Bender
JG
Immunocytochemistry and flow cytometry evaluation of human megakaryocytes in fresh samples and cultures of CD34+ cells.
Cytometry
23
1996
250
232
Appelbaum FR: Haemopoietic reconstitution following autologous bone marrow and peripheral blood mononuclear cell infusion. Exp Haematol 7:7, 1979 (suppl 5)
233
Henon
PR
Liang
H
Beck-Wirth
G
Eisenmann
JC
Lepers
M
Wunder
E
Kandel
G
Comparison of haemopoietic and immune recovery after autologous bone marrow or blood stem cell transplants.
Bone Marrow Transplant
9
1992
285
234
Takaue
Y
Okamoto
Y
Kawano
Y
Suzue
T
Abe
T
Saito
SI
Sato
J
Hirao
A
Makimoto
A
Kawahito
M
Regeneration of immunity and varicella-zoster virus infection after high-dose chemotherapy and peripheral blood stem cell autografts in children.
Bone Marrow Transplant
14
1994
219
235
Stein
DS
Korvic
JA
Vermund
SH
CD−1 lymphocyte cell enumberation for prediction of clinical course of human immunodeficiency virus disease.
J Infect Dis
165
1992
352
236
Walter
EA
Greenberg
PD
Gilbert
MJ
Finch
RJ
Kathe
S
Watanabe
M
Thomas
ED
Riddell
SR
Reconstitution of cellular immunity against cytomegalovirus in recipients of allogeneic bone marrow by transfer of T-cell clones from the donor.
N Engl J Med
333
1995
1038
237
Scheid
C
Pettengell
R
Ghielmini
M
Radford
JA
Morgensteren
GR
Stern
PL
Crowther
D
Time-course of the recovery of cellular immune function after high-dose chemotherapy and peripheral blood progenitor cell transplantation for high-grade non-Hodgkin's lymphoma.
Bone Marrow Transplant
15
1995
901
238
Johnsen
HE
Hansen
PB
Plesner
T
Ralfkiaer
E
Hansen
NE
Increased yield of myeloid progenitor cells in bone marrow harvested for autologous transplantation by pretreatment with recombinant human granulocyte-colony stimulating factor.
Bone Marrow Transplant
10
1992
229
239
Johnsen HE, Hansen PB, Plesner T, Ralfkiaer E, Hansen NE: Cytokine priming of bone marrow and blood progenitors before harvest for autologous stem-cell transplantation, in Levitt D, Mertelsmann R (eds): Hematopoietic Stem Cells. New York, NY, Dekker, 1995, p 455
240
Janssen
WE
Smilee
RC
Elfenbein
GJ
A prospective randomized trial comparing blood- and marrow-derived stem cells for hematopoietic replacement following high-dose chemotherapy.
J Hematother
4
1995
139
241
Fibbe
WE
Heemskerk
DPM
Laterveer
L
Pruijt
JDM
Foster
D
Kaushansky
K
Willemze
R
Accelerated reconstitution of platelets and erythrocytes after syngeneic transplantation of bone marrow cells derived from thrombopoietin pretreated donor mice.
Blood
86
1995
3308
242
Harousseau
JL
Attal
M
Divine
M
Milpied
N
Marit
G
Leblond
V
Stoppa
AM
Bourhis
JH
Caillot
D
Boasson
M
Abgrall
JF
Facon
T
Colombat
P
Cahn
JY
Lamy
T
Troussard
X
Gratecos
N
Pignon
B
Auzanneau
G
Comparision of autologous bone marrow transplantation and peripheral blood stem cell transplantation after first remission induction treatment in multiple myeloma.
Bone Marrow Transplant
15
1995
963
243
Peters
WP
Ross
M
Vredburgh
B
Meisenberg
B
Marks
L
Winer
E
Kurtzberg
J
Bast
RC
Jones
R
Shpall
E
Wu
K
Rosner
G
Gilbert
C
Mathias
B
Coniglio
D
Petros
W
Henderson
IC
Norton
L
Weiss
RB
Budman
D
Hurd
D
High-dose chemotherapy and autologous bone marrow support as consolidation after standard-dose adjuvant therapy for high-risk primary breast cancer.
J Clin Oncol
11
1993
1132
244
Tepler
I
Cannistra
SA
Frei
E
Use of peripheral blood progenitor cells abrogates the myelotoxicity of repetitive outpatient high dose carboplatin and cyclophosphamide chemotherapy.
J Clin Oncol
11
1993
1583
245
Ayash
LJ
Elias
A
Wheeler
C
Reich
E
Schwartz
G
Mazanet
R
Tepler
I
Warren
D
Lynch
C
Gonin
R
Schnipper
L
Frei
E
Antman
K
Double dose-intensive chemotherapy with autologous marrow and peripheral-blood progenitor-cell support for metastatic breast cancer. A feasibility study.
J Clin Oncol
12
1994
37
246
Bezwoda
WR
Seymour
L
Dansey
RD
High-dose chemotherapy with hematopoietic rescue as primary treatment for metastatic breast cancer: A randomized trial.
J Clin Oncol
13
1995
2483
247
Schiller
G
Vescio
R
Freytes
C
Spitzer
G
Sahebi
F
Lee
M
Wu
CH
Cao
J
Lee
JC
Hong
CH
Lichtenstein
A
Lill
M
Hall
J
Berenson
R
Berenson
J
Transplantation of CD34+ peripheral blood progenitor cells after high-dose chemotherapy for patients with advanced multiple myeloma.
Blood
86
1995
390
248
Negrin
RS
Kusnierz-Glaz
Still BJ
Schriber
JR
Nelson
JC
Long
GD
Hoyle
C
Hu
WW
Horning
SJ
Brown
BW
Blume
KG
Strober
S
Transplantation of enriched and purged peripheral blood progenitor cells from a single apheresis product in patients with non-hodgkin's lymphoma.
Blood
85
1995
3334
249
Macintyre
EA
Belanger
C
Debert
C
Canioni
D
Turhan
AG
Azagury
M
Hermine
O
Varet
B
Flandrin
G
Schmitt
C
Detection of clonal CD34+19+ progenitors in bone marrow of BCL2-IgH-positive follicular lymphoma patients.
Blood
86
1995
4691
250
Campana
D
Pui
C-H
Detection of minimal residual disease in acute leukemia: Metholdologic advances and clinical significance.
Blood
85
1995
1416
251
Brenner
MK
Rill
DR
Moen
RC
Krance
RA
Mirro
J
Anderson
WF
Ihle
JN
Gene-marking to trace origin of relapse after autologous bone marrow transplantation.
Lancet
341
1993
85
252
Gorin
NC
Marrow purging: Present status and future perspectives — Efficacy in AML.
Prog Clin Biol Res
377
1992
251
253
Szer
J
Juttner
CA
To
LB
Bradstock
KF
Sage
RE
Enno
A
Toogood
IRG
Post-remission therapy for acute myeloid leukaemia with blood-derived stem cell transplantation. Results of a collaborative phase II trial.
Int J Cell Cloning
10
1992
114
254
Brisco MJ, Condon J, Hughes E, Neoh SH, Sykes PJ, Seshadri R, Toogood I, Waters K, Tauro G, Ekert H: Outcome prediction in childhood acute lymphoblastic leukaemia by molecular quantification of residual disease at the end of induction. Lancet 22:343,196, 1994
255
Seriu
T
Yokota
S
Nakao
M
Misawa
S
Takaue
Y
Koizumi
S
Kawai
S
Fujimoto
T
Prospective monitoring of minimal residual disease during the course of chemotherapy in patients with acute lymphoblastic leukemia, and detection of contaminating tumor cells in peripheral blood stem cells for autotransplantation.
Leukemia
9
1995
615
256
Sharp
JG
Mann
SL
Murphy
B
Weekes
C
Culture methods for the detection of minimal tumour contamination of hematopoietic harvests: A review.
J Hematother
4
1995
1418
257
Craig
JL
Langlands
K
Parker
AC
Anthony
RS
Molecular detection of tumor contamination in peripheral blood stem cell harvests.
Exp Hematol
22
1994
898
258
Dreyfus
F
Ribrag
V
Leblond
V
Ravaud
P
Melle
J
Quarre
MC
Pillier
C
Boccaccio
C
Varet
B
Detection of malignant B cells in peripheral blood stem cell collections after chemotherapy in patients with multiple myeloma.
Bone Marrow Transplant
15
1995
707
259
Henry
JM
Sykes
PJ
Brisco
MH
To
LB
Juttner
CA
Morley
AA
Comparison of myeloma cell contamination of bone marrow and peripheral blood stem cell harvests.
Br J Haematol
92
1996
614
260
Simpson
SJ
Vachula
M
Kennedy
MJ
Kaizer
H
Coon
JS
Williams
S
Van Epps
D
Detection of tumor cells in the bone marrow, peripheral blood, and apheresis products of breast cancer patients using flow cytometry.
Exp Hematol
23
1995
1062
261
Passos-Coelho
JL
Ross
AA
Moss
TJ
Davis
JM
Huelskamp
A-M
Noga
SJ
Davidson
NE
Kennedy
MJ
Absence of breast cancer cells in a single-day peripheral blood progenitor cell collection after priming with cyclophosphamide and granulocyte-macrophage colony-stimulating factor.
Blood
85
1995
1138
262
Neiderwieser
DW
Appelbaum
FR
Gastl
G
Gersdorf
E
Meister
B
Geissler
D
Tratkiewicz
JA
Thaler
J
Huber
C
Inadvertent trasmission of a donor's acute myeloid leukemia in bone marrow transplantation for chronic myelocytic leukemia.
N Engl J Med
322
1990
1794
263
Brito-Babapulle
F
Apperley
JF
Rassool
F
Guo
A-P
Dowding
C
Goldman
JM
Complete remission after autografting for chronic myeloid leukemia.
Leuk Res
11
1987
1115
264
Lapidot T, Sirard C, Vormoor J, Murdoch B, Hoang T, Caceres-Cortes J, Minden M, Paterson B, Caligiuri MA, Dick JE: A cell initiating human acute myeloid leukaemia after transplantation into SCID mice. Nature 17:367, 645, 1994
265
Henon PR: Autologous blood stem-cell versus bone marrow transplantation: Comparison of cast-effectiveness and of clinical benefits, in Levitt D, Mertelsmann R (eds): Hematopoietic Stem Cells. New York, NY, Dekker, 1995, p 421
266
Henon
P
Donatini
B
Eisenmann
JC
Becker
M
Beck-Wirth
G
Comparative survival, quality of life and cost-effectiveness of intensive therapy with autologous blood cell transplantationor conventional chemotherapy in multiple myeloma.
Bone Marrow Transplant
16
1995
19
267
Kessinger
A
Smith
DM
Strandjord
SE
Landmark
JD
Dooley
DC
Law
P
Coccia
PF
Warkentin
PI
Weisenburger
DD
Armitage
JO
Allogeneic transplantation of blood-derived, T cell-depleted hemopoietic stem cells after myeloablative treatment in a patient with acute lymphoblastic leukemia.
Bone Marrow Transplant Nov
4
1989
643
268
Korbling
M
Przepiorka
D
Huh
Y
Engel
H
Van Besien
K
Giralt
S
Anderson
B
Kleine
HD
Seong
D
Deisseroth
AB
Andreef
M
Champlin
R
Allogeneic blood stem cell transplantation for refractory leukemia and lymphoma: Potential advantages of blood over marrow allografts.
Blood
86
1995
1659
269
Ottinger
HD
Beelen
DW
Scheulen
B
Schaefer
UW
Grosse-Wilde
H
Improved immune reconstitution after allotransplantation of peripheral blood stem cells instead of bone marrow.
Blood
88
1996
2775
270
Reisner
Y
Martelli
M
Bone marrow transplantation across HLA barriers by increasing the number of transplanted cells.
Immunol Today
16
1995
437
271
Aversa
F
Tabilio
A
Terenzi
A
Velardi
A
Falzeth
F
Giannoni
C
Iacucci
R
Zei
T
Martelli
MP
Gambelunghe
C
Rossetti
M
Caputo
P
Latini
P
Aristei
C
Raymond
C
Reisner
Y
Martelli
M
Successful engraftment of T-cell depleted haploidentical ‘tree loci’ incompatible transplantation in leukemia patients by addition of recombinant granulocyte colony-stimulating factor-mobilised peripheral blood progenitor cells to marrow inoculum.
Blood
84
1994
3948
272
Coulombel
L
Kalousek
DK
Eaves
CJ
Gupta
CM
Eaves
AC
Long term marrow culture reveals chromosomally normal hematopoietic progenitor cells in patients with Philadelphia chromosome positive chronic myelogenous leukemia.
N Engl J Med
306
1983
1493
273
Gronthos
S
To
LB
Moore
S
Suttle
JM
Juttner
CA
The detection of philadelphia chromosome negative metaphases in long term bone marrow cultures of the peripheral blood from patients with chronic myeloid leukemia predicts response to interferon-alpha 2a.
Leukemia
6
1992
1246
274
Carella AM, Pollicardo N, Raffo MR, Podesta M, Carlier P, Valbonesi M, Lercari G, Vitale V, Gallamini A: Intensive conventional chemotherapy can lead to a precocious overshoot of cytogenetically normal blood stem cells (BSC) in chronic myeloid leukemia and acute lymphoblastic leukemia. Leukemia 6:120, 1992 (suppl 4)
275
Verfaillie
CM
Miller
WJ
Boylan
K
McGlave
PB
Selection of benign primitive hematopoietic progenitors in chronic myelogenous leukemia on the basis of HLA-DR antigen expression.
Blood
79
1992
1003
276
Berardi
AC
Wang
A
Levine
JD
Lopez
P
Scadden
DT
Functinal isolation and characterization of human hematopoietic stem cells.
Science
267
1995
104
277
Dunbar
CE
Stewart
FM
Separating the wheat from the chaff: Selection of benign hematopoietic cells in chronic myeloid leukemia.
Blood
79
1992
1107
278
Leopold
LH
Shore
SK
Newkirk
TA
Reddy
RMV
Reddy
EP
Multi-unit ribozyme-mediated cleavage of bcr-abl mRNA in myeloid leukemias.
Blood
85
1995
2162
279
de Fabritis
P
Amadori
S
Petti
MC
Mancini
M
Montefusco
E
Picardi
A
Geiser
T
Campbell
K
Calabretta
B
Mandelli
F
In vitro purging with BCR-ABL antisense oligodeoxynucleotides does not prevent haematologic reconstitution after autologous bone marrow transplantation.
Leukemia
9
1995
662
280
Delforge
M
Demuynck
H
Vandenber; ghe P
Verhoef
G
Zachee
P
Van Duppen
V
Marijnen
P
Van den Berghe
H
Boogaerts
MA
Polyclonal primitive hematopoietic progenitors can be detected in mobilized peripheral blood from patients with high-risk myelodysplastic syndromes.
Blood
86
1995
3660
281
Takaue
Y
Kawano
Y
Abe
T
Okamoto
Y
Suzue
T
Shimizu
T
Saito
S
Sato
J
Makimoto
A
Nakagawa
R
Collection and transplantation of peripheral blood stem cells in very small children weighing 20 kg or less.
Blood
86
1995
372
282
Takaue
Y
Watanabe
T
Kawano
Y
Koyama
T
Huq
AHM
Ninomiya
T
Kuroda
Y
Sustained cytopenia in small children after leukapheresis for collection of peripheral blood stem cells.
Vox Sang
57
1989
168
283
Prince
GM
Nguyen
M
Lazarus
HM
Brodsky
RA
Terstappen
LWMM
Medof
ME
Peripheral blood harvest of unaffected CD34+ CD38− hematopoietic precursors in paroxysmal nocturnal hemoglobinuria.
Blood
86
1995
3381
284
Burt
RK
Burns
W
Hess
A
Bone marrow transplantation for multiple sclerosis.
Bone Marrow Transplant
16
1995
1
285
Dunbar CE: Clinical gene therapy, in Morstyn G, Sheridan W (eds): Cell Therapy Stem Cell Transplantation, Gene Therapy, and Cellular Immunotherapy (vol 21). New York, NY, Cambridge University Press, 1996, p 369
286
Kohn
DB
Weinberg
KI
Nolta
JA
Heiss
LN
Lenarsky
C
Crooks
GM
Hanley
ME
Annett
G
Brooks
JS
el-Khoureiy
A
Engraftment of gene-modified umbilical cord blood cells in neonates with adenosine deaminase deficiency.
Nat Med
1
1995
1017
287
Hanania
EG
Kavanagh
J
Hortobagyi
G
Giles
RE
Champlin
R
Deisseroth
AB
Recent advances in the application of gene therapy to human disease.
Am J Med
99
1995
537
288
Flasshove
M
Banerjee
D
Mineishi
S
Li
M-X
Bertino
JR
Moore
MAS
Ex vivo expansion and selection of human CD34+ peripheral blood progenitor cells I of a mutated dihydrofolate reductase cDNA via retroviral gene transfer.
Blood
85
1995
556
289
Malech HL, Sekhsaria S, Whiting-Theobald, Linton GF, Vowells LF, Miller JA, Holland SM, Leitman SF, Carter CS, Read EJ, Butz R, Wannebo C, Fleisher TA, Deans RJ, Spratt SK, Maack CA, Rokovich JA, Cohen LK, Maples Gallin JI: Development of a phase I clinical trial of gene therapy for chronic granulomatous disease. Blood 85:295a, 1995 (abstr, suppl 1)
290
Nimgaonkar
M
Mierski
J
Beeler
M
Kemp
A
Lancia
J
Mannion-Henderson
J
Mohney
T
Bahnson
A
Rice
E
Ball
ED
Barranger
JA
Cytokine mobilization of peripheral blood stem cells in patients with gaucher disease with a view to gene therapy.
Exp Hematol
23
1995
1633