(3S-5S-6E)-7-[3-(4-fluorophenyl)-1-(propan-2-yl)-1H-indol-2-yl]-3-5-dihydroxyhept-6-enoic-acid and Melanoma

Although vemurafenib has been shown to improve the overall survival of patients with metastatic melanoma harboring the BRAF V600E mutation, its efficacy is often hampered by drug resistance acquired within a relatively short period through several distinct mechanisms. In the present study, we investigated the effect of fluvastatin as a possible strategy to overcome such acquired resistance using a cultured cell line model. We established vemurafenib-resistant (VR) cells from three BRAF (V600E)-mutated melanoma lines (C32, HMY-1, and SK-MEL-28) and evaluated the mechanism of acquired resistance of VR cells by water-soluble tetrazolium salts assay, western blot, real-time quantitative PCR, and immunofluorescent microscopy. The efficacy of the combination of growth inhibitory effect of vemurafenib and fluvastatin on respective parental and VR cells were assessed by calculating combination index and western blot. IC50 values of three VR cells were ~5-100-fold higher than those for the respective parental cells. The VR cells derived from HMY-1 and SK-MEL-28 showed constitutive activation of AKT kinase, and the specific AKT inhibitor MK-2208 or the PI3K inhibitor wortmannin increased the cellular sensitivity to vemurafenib. Intriguingly, application of a statin-related drug, fluvastatin, also resulted in a synergistic increase of sensitivity to vemurafenib in the VR cells (combination index: 0.73-0.86) probably by alleviating constitutive AKT activation, whereas the same treatment did not notably alter the vemurafenib sensitivity of the parental cells. Our results suggest the possible usefulness of statin-related drugs for overcoming vemurafenib resistance acquired through constitutive activation of the PI3K-AKT axis.

Topics: Acyltransferases; Adaptor Proteins, Signal Transducing; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Biomarkers, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Fluvastatin; Gene Expression Regulation, Neoplastic; Humans; Melanoma; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; TOR Serine-Threonine Kinases; Transcription Factors; Tumor Cells, Cultured; Vemurafenib; YAP-Signaling Proteins

Most metastatic melanomas are refractory to current available therapy, underscoring the need to identify new effective treatments. Sorafenib, a multikinase inhibitor of the mitogen-activated protein kinase signaling 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 sorafenib in chemoresistant human melanoma cell lines also 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. Our results demonstrate that fluvastatin at 1 μM, a level 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 sorafenib 50% growth inhibition (GI50), respectively. Similar effects were observed for 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 poly (ADP-ribose) polymerase. In combination with sorafenib, fluvastatin treatment results in reduced levels of activated murine thymoma viral oncogene homolog along with enhanced levels of activated c-Jun N-terminal kinase. Sensitization to sorafenib is unique to fluvastatin, as other statins (pravastatin and simvastatin) do not enhance sorafenib-mediated growth inhibition. 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.

Topics: Anthracenes; Benzenesulfonates; Cell Death; Cell Line, Tumor; Cell Proliferation; Chromones; Drug Screening Assays, Antitumor; Drug Synergism; Enzyme Activation; Fatty Acids, Monounsaturated; Fluvastatin; Humans; Indoles; JNK Mitogen-Activated Protein Kinases; Melanoma; Morpholines; Niacinamide; Phenylurea Compounds; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-akt; Pyridines; Signal Transduction; Sorafenib