Background. Mantle cell lymphoma (MCL) is incurable for many patients. Arsenic trioxide (As2O3) has activity in vitro against lymphoid malignancies. The effects of As2O3 on MCL in vitro and in patients with refractory disease were investigated.

Materials and methods. Mantle cell lymphoma (MCL) lines (Jeko-1, Granta-519) were treated with As2O3, in combination with mitoxantrone (MTZ) and ascorbic acid (AA). Consenting patients with refractory MCL were treated with oral-As2O3 (10 mg/day), AA (1 g/day) and chlorambucil (4 mg/day) as outpatients until maximum response or the disease judged refractory. Responses were defined by standard NCI criteria. In patients showing an initial response, vincristine (2 mg intravenously) and prednisolone (30 mg/day) might also be added. After achievement of maximum response, patients were maintained with As2O3 (10 mg/day) and AA (1 g/day) for two weeks every month, for a planned two years.

Results. As2O3 and MTZ but not AA induced a dose dependent apoptosis in the MCL lines, as shown by flow cytometry and MTT assays. As2O3, MTZ and AA were tested in various combinations in MTT assays. Synergistic interactions were observed only in the combinations As2O3 (1 uM) + MTZ (0.2 mg/L), and As2O3 (1 uM) + MTZ (0.2 mg/L) + AA (100 uM). Western blotting showed that As2O3-induced apoptosis was associated with a dose and time dependent down-regulation of cyclin D1. However, quantitative polymerase chain reaction showed no change in cyclin D1 gene transcription during As2O3-induced apoptosis. Eleven patients (10 men, 1 women) at a median age of 69 (51–70) years with refractory MCL were studied, at a median of 33 (8–85) months from diagnosis. At the time of As2O3 treatment, they had already had a median of 2 (1 – 4) relapses managed with a median of 2 (1 – 6) previous chemotherapeutic regimens. Eight of eleven patients were evaluable (for the other three, one died after 4 days of treatment, and the two were still receiving therapy). At a median follow up of 9 (4 – 20) months, 4 patients had reached complete remission (CR) or probable CR (CRu), two were in good partial remission, and two had died with progressive disease.

Conclusion. As2O3 induced apoptosis of MCL cells by post-transcription down-regulation of cyclin D1. Synergistic interactions were observed with AA and cytotoxics. Oral-As2O3, AA and chlorambucil were an active regimen for relapsed and therapy-refractory MCL, and treatment results compared favorably with other salvage regimens. This entirely oral regimen has several attractions, including outpatient treatment, low toxicity and cost.

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