Abstract

Cytotoxic chemotherapies used to treat acute leukemia and high-grade lymphoma target rapidly-dividing cells including the malignant cells but also normal HSC needed to replenish the blood and immune system, as well as mucosal cells lining the respiratory and gastrointestinal tracts. Consequences include therapy-induced mucositis (providing a portal of entry for bacteria) and neutropenia leading to increased morbidity and potentially life-threatening infections. In acute myeloid leukemia and high-grade lymphoma patients, treatment-related mortality can reach 20% (Elmaagacli, BMT, 2007).

We now report a novel therapy (therapeutic blockade of E-selectin) that may enhance survival after repeated rounds of high-dose chemotherapy. In mice we find the mechanism contributing to this enhanced survival to be a combination of accelerated neutrophil recovery and a dramatic reduction in therapy-related weight loss and intestinal mucositis when E-selectin is therapeutically blocked or genetically-deleted.

Our studies were performed using two treatment regimens (chemotherapy or radiation). For chemotherapy, cohorts of mice received repeated rounds of the anti-metabolite, 5-fluorouracil (5-FU) at a dose of 150mg/kg every 10 days without prophylactic antibiotic support. Using this regime, 80% of E-selectin gene-deleted mice (E-/-) survived >6 weeks. In sharp contrast all wild-type mice died (p<0.05). To determine whether febrile neutropenia was potentially involved, blood was collected for analysis on the 10th day following each round of treatment, just prior to the administration of the next round of 5-FU. After 4 rounds of chemotherapy E-/- mice had recovered acceptable neutrophil counts (n=10). In contrast, only 5 of 10 wild-type mice had recovered from therapy-induced neutropenia. Most of those that could not subsequently died.

Deletion of the E-selectin gene also prevented therapy-induced weight loss (from 16% average weight loss in wild-type mice, to only 2% in E-/- mice after 2 rounds 5-FU, p<0.05) which was completely unanticipated. To investigate this further, cohorts of mice were administered 5-FU as described above for histological scoring of intestinal mucositis. To our surprise, we found that deletion of the E-selectin gene almost completely alleviated chemotherapy-induced mucositis. In sharp contrast, intestines of wild-type mice showed extensive ulceration and villous loss with inflammatory infiltrates occurring at the same time as neutropenia – very likely contributing to their death. Moreover we found E-selectin was up-regulated 10-fold in the intestines following chemotherapy or radiation damage, which we hypothesis is critical for recruitment of inflammatory cells to the mucosa. Indeed by immunohistology and flow cytometry, migration of F4/80+ macrophages to 5-FU damaged intestines was increased 7-10-fold in wild-type mice but completely absent in E-/- mice. Similar results were also observed following 8.0 Gy total body irradiation.

Therapy-induced mucositis is greatly exacerbated by a wave of secondary inflammation following initial direct damage. We found administration of the selective E-selectin antagonist GMI-1271 (20 mg/kg bi-daily) for 5 days following each round of chemotherapy enhanced neutrophil recovery and similarly protected mice from weight loss and mucositis following chemotherapy. Importantly the administration of GMI-1271 effectively blocked secondary migration of inflammatory F4/80+ Ly-6C+ macrophages to intestines of mice following chemotherapy or irradiation.

In conclusion, our results suggest that inflammatory macrophages play a major role in chemotherapy-induced mucositis and are recruited to damaged intestine following E-selectin up-regulation. Importantly there is no current highly-effective treatment to prevent mucositis. Therapeutic blockade of E-selectin by administration of GMI-1271 at the same time as chemotherapy represents a potential effective and novel therapy to block recruitment of inflammatory macrophages to damaged mucosa whilst also enhancing neutrophil recovery, thus protecting patients from two chemotherapy-induced side-effects. Therapeutic blockade of E-selectin should provide an opportunity for improved completion rates of toxic chemotherapy or radiotherapy regimes and reduce therapy-related morbidity and mortality.

Disclosures:

Magnani:GlycoMimetics, Inc.: Employment, Equity Ownership.

Author notes

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Asterisk with author names denotes non-ASH members.