Abstract 3510: Fluvastatin enhances sorafenib cytotoxicity in melanoma cells via modulation of AKT and JNK signaling pathways

Background: Most metastatic melanomas are refractory to current available therapy, underscoring the need to identify new effective treatments. Sorafenib, a multikinase inhibitor of the RAF/RAS/MEK pathway, showed promise in earlier stages of clinical development, but ultimately failed to demonstrate efficacy as a single agent in the treatment of melanoma. In order to enhance the efficacy of sorafenib in the treatment of melanoma, we tested over 2,000 naturally occurring compounds and marketed drugs in the presence of a sorafenib in two chemoresistant human melanoma cell lines (M14 and SKM-173) resistant to sorafenib-induced apoptosis. Of the 9 compounds identified as sorafenib sensitizers, we prioritized the cholesterol lowering agent fluvastatin based on its favorable pharmacokinetics and safety profile. Methodology: Growth inhibition was examined by MTT assay in a panel of 6 human melanoma cell lines. Drug interaction was analyzed by Calcusyn software which determines the effects of two drugs (i.e., synergy, antagonism, or additivity) through calculations of the combination index (CI). The effect of combination therapy on cellular signaling and induction of apoptotic pathways was evaluated by immunoblotting techniques. Results: Our results demonstrate that fluvastatin at 1µM, a level which is safely achieved through oral administration, dramatically enhances the growth inhibitory activity of clinically achievable concentrations of sorafenib in M14 and SKM-173 melanoma cells with a 3.2 and 3.6-fold reduction in the sorafenib GI50, respectively, with similar effects observed in other melanoma cell lines. Combination indices analysis revealed a synergistic relationship between the two agents. Fluvastatin enhances sorafenib-mediated apoptosis as revealed through enhanced cleavage of PARP. In combination with sorafenib, fluvastatin treatment results in reduced levels of activated AKT along with enhanced levels of activated JNK. Sensitization to sorafenib is unique to fluvastatin as other statins (ie. pravastatin and simvastatin) do not enhance sorafenib-mediated growth inhibition. Conclusions: These promising results warrant further investigation into the clinical applicability of fluvastatin as an agent for enhancing the efficacy of sorafenib in the treatment of melanoma. Fluvastatin sensitization to sorafenib will be further addressed through follow-up studies in mouse melanoma xenograft models. Citation Format: {Authors}. {Abstract title} [abstract]. In: P