Abstract 2078: Synergistic effects of c-Met and BRAF inhibitors and role of c-Met as a therapeutic target in human melanoma.

Abstract

Abstract Inhibitors of c-Met and mutated BRAF kinases show limited efficacy due to the development of kinase inhibitor (KI) resistance hence it is important to target a combination of kinases. To study the efficacy of a c-Met and BRAF inhibitor combination, two cell lines were selected: MU, which is positive for the BRAF activating V600E mutation, and MM-RU, which is negative for this mutation. c-Met inhibitor SU11274 resistant cell lines were generated by exposing these parental lines to increasing concentrations of SU11274, until the final IC50 concentrations of resistant cells were 6-8 fold higher than those of parental lines. When c-Met and BRAF kinase inhibitors SU11274 (0.075μM) and vemurafenib (0.15μM) were administered individually and in combination, both drugs were able to significantly (p<0.01) synergize their inhibitory effects in MU parental and SU11274 resistant cells (60% and 58%, respectively) compared to their individual treatments (MUP 41%/5% and MUR 46%/0% vemurafenib/SU11274, respectively). When cells from the RU line were treated with varying concentrations of tivantinib, a c-Met inhibitor currently in clinical trials (0.05μM - 0.3μM) and Vemurafenib (0.025μM - 0.15μM), both parental and resistant cells did not show any synergism in combination. Conversely, MU parental and SU11274 resistant cells again showed synergism (27% and 22% respectively as determined by ANOVA analysis, p<0.01) when treated with 0.15μM vemurafenib and 0.075μM tivantinib in combination. However, minimal inhibition (MUP 9%/4% and MUR 0%/4% vemurafenib/tivantinib) was seen in MU cell lines in response to vemurafenib and tivantinib when given individually. This data suggests that using a vemurafenib and c-Met inhibitor combination therapy on BRAF mutant and c-Met expressing tumors would greatly benefit melanoma patients, even those exhibiting c-Met TKI resistance. To study the effects of an oral/bioavailable c-Met TKI, JNJ, and to determine if c-Met inhibitors could be delivered systemically and targeted to the tumor, the therapeutic effects of JNJ were tested in vivo on MM-RU melanoma cells which produce HGF. Five million MM-RU melanoma cells were injected subcutaneously into the hind flanks of nude mice. When tumors were palpable, they were treated with 20mg/kg JNJ or vehicle (20% Captisol, 0.25% PVP in 0.1N HCL) for 3 weeks. We found that JNJ significantly reduced tumor size by 6 fold (123.77 +/- 56.66mm2 and 16.67 +/-11.19mm2 p<0.03) compared to vehicle. Treatment with JNJ also resulted in 80% +/- 2.35% reduction in blood vessels as seen by CD31 staining and decreased VEGF expression and increased TSP1 expression as seen by immunohistochemistry in MM-RU indicating that inhibition of vessel formation may be one of the mechanisms by which JNJ inhibits tumor growth. Our data indicates that JNJ could be a promising therapeutic option for treating HGF producing melanoma. Citation Format: Deven Etnyre, Manohar Reddy Shambannagari, Neelu Puri. Synergistic effects of c-Met and BRAF inhibitors and role of c-Met as a therapeutic target in human melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2078. doi:10.1158/1538-7445.AM2013-2078