Effect of lenalidomide on the response of bladder cancer to BCG immunotherapy in an in vivo murine model.

Abstract

288 Background: Intravesical BCG is the gold standard for non-muscle-invasive bladder cancer (NMIBC). However, many patients do not respond to therapy while others relapse and/or progress. As a result, there remains a need for therapies that can enhance the efficacy of BCG. We explore the efficacy of lenalidomide, an immunomodulatory agent used in multiple myeloma and myelodysplastic syndrome, in combination with BCG in vitro and in an in vivo bladder cancer model. Methods: We studied the effects of lenalidomide in combination with BCG induced cytokines in MBT-2 cells using PI-FACS. For in vitro studies, we used 10 and 100 nM of lenalidomide in combination with TNF-a and FasL. We then performed Western blotting for cell cycle and apoptosis regulatory proteins. Subsequently, we tested the efficacy of this combination in an immunocompetent murine model of bladder cancer with MBT-2 cells in C3H mice using the flank injection method. Drug dosages were 30 mg/kg for lenalidomide and 105 CFU of BCG. Tumor growth curves were created for the control, lenalidomide, BCG and combination treatment mice groups. Immunohistochemistry (IHC) was then performed using antibodies against proteins related to cell cycle, apoptosis, angiogenesis and immune response. Results: PI-FACS identified increased DNA fragmentation in the combinations of lenalidomide and TNF-a and FasL compared to control and each agent alone. Using Western blotting, we demonstrated that the combination resulted in apoptosis via caspase-3 activation. In the murine model, combination therapy resulted in a statistically significant decreased tumor size compared to the control group. While the BCG alone and lenalidomide alone groups did show a trend toward smaller tumor, they did not reach statistical significance. Furthermore, the TUNEL assay showed a substantial increase in apoptosis only in the combination group. Immunohistochemistry demonstrated decreased angiogenesis in all treatment groups compared to control, as well as, decreased T-cell infiltration. Conclusions: Our study demonstrates a potential role for the immunomodulatory agent, lenalidomide, in combination with BCG for NMIBC. This in vivo model serves as a template for future clinical trials.