Lenalidomide Displays Anti-Proliferative Activity and Combination Effects with Chemotherapeutic Agents Against a Burkitt’s Lymphoma Cell Line.

Background: Lenalidomide (Revlimid®) is approved for the treatment of del 5q myelodysplastic syndrome (MDS) and in combination with dexamethasone for previously treated multiple myeloma. It is currently being evaluated as treatment for other hematology and oncology conditions, including NHL as a single agent and in combination with other therapeutics.

Aims: The present study evaluates the effect of lenalidomide on the proliferation of the Burkitt’s Lymphoma tumor cell line Namalwa CSN.70, as a single agent and in combination with various chemotherapeutic agents: dexamethasone, doxorubicin, vincristine, methotrexate, cytarabine, ifosfamide, cyclophosphamide, carmustine, prednisone, etoposide, rituximab, bortezomib, rapamycin, and the mixed kinase inhibitor UCN-01.

Methods: Namalwa CSN.70 cells were incubated in 96-well cell culture plates with compounds for 72 hours and cell proliferation was assayed by ³H-thymidine incorporation. IC₅₀s were calculated by nonlinear regression analyses with GraphPad Prism.

Results: Namalwa cell proliferation was inhibited by lenalidomide and the chemotherapeutic agents dexamethasone, doxorubicin, vincristine, methotrexate, cytarabine, carmustine, prednisone and etoposide. Cyclophosphamide and ifosfamide had no effect, since these agents require metabolic activation by cytochrome P450 enzymes. Lenalidomide combined with dexamethasone displayed synergistic anti-proliferative effects. Lenalidomide combined with prednisone displayed partially additive anti-proliferative effects at prednisone concentrations within the range of 0.5 and 50 mM, although this was non-additive at lower concentrations of both drugs. Lenalidomide combined with etoposide displayed partially additive anti-proliferative effects at etoposide concentrations within the concentration range of 0.05 and 0.5 mM, although at lower concentrations the response became non-additive and comparable to the effect of lenalidomide alone. In contrast, lenalidomide combined with carmustine displayed antagonistic effects at low concentrations, although partially additive anti-proliferative effects were observed at higher concentrations. Lenalidomide combined with methotrexate was also antagonistic. Lenalidomide in combination with cytarabine, doxorubicin, or vincristine generated anti-proliferative responses that were equivalent to the inhibition produced by these respective chemotherapeutic agents alone. Finally, rituximab was unable to add to the anti-proliferative effect of lenalidomide, consistent with the rituximab mechanism of action being primarily antibody-dependent cell-mediated cytotoxicity (ADCC), rather than direct apoptotic signaling since there is data showing the benefit of this combination in a mouse model of disseminated NHL (Hernandez-Ilizaliturri et al. 2005 Clin Cancer Res. 11:5984).

Conclusions: These results support the potential for a synergistic effect of lenalidomide in combination with dexamethasone in NHL. Furthermore, partially additive effects of lenalidomide with prednisone and etoposide suggest these may be useful combinations. Results with bortezomib, rapamycin and UCN-01 will also be discussed.