Abstract 16: Evaluation of the efficacy of clotrimazole treatment in human melanoma cell lines that overexpress the multidrug resistance-associated protein (MRP) and the lung resistance-related protein (LRP)

Abstract

Abstract Drug resistance to chemotherapy, mediated in part by overexpression of P-glycoprotein (MDR-1), multidrug resistance-associated protein (MRP), or lung resistance-realted protein (LRP), continues to be a major problem in the treatment of melanoma. Because we previously demonstrated the ability of clotrimazole to enhance cytotoxicity in human metastatic melanoma cells, here we evaluated the ability of clotrimazole to treat drug-resistant human melanoma cells that overexpress MRP and/or LRP. We utilized human melanoma cell lines that overexpress either MDR or LRP, and human melanoma cell lines that overexpress both. Cell growth and cell death were analyzed by flow cytometry, proliferation assays, and immunoblotting after drug treatments and RNA interference. Clotrimazole caused significant decreases in proliferation and increases in cell death in both drug-sensitive melanoma lines and those overexpressing MRP and LRP. No extensive cell death was induced by clotrimazole treatment in noncancerous human skin cell lines. These results indicate that clotrimazole selectively induces cytotoxicity in both drug-sensitive and drug-resistant melanoma lines. As clotrimazole is known to inhibit various transient receptor potential (TRP) ion channels, we pretreated these melanoma lines with TRP inhibitors or RNAi. Inhibitors of the TRP melastatin-8 channel (TRPM8) or TRP vanilloid-1 (TRPV1) failed to produce comparable levels of cell death caused by clotrimazole. However, RNAi silencing of the TRPM2 cation channel caused significant levels of cell death in both drug-sensitive and drug-resistant melanoma lines. These results indicated that inhibition of TRPM2 channels may have a primary role in the ability of clotrimazole to treat drug-sensitive and drug-resistant melanoma lines. In conclusion, this study demonstrated that clotrimazole selectively increases cell death in drug-resistant melanoma lines, with minimal deleterious effects in normal skin cells. Taken together, we conclude that clotrimazole has in vitro efficacy toward the treatment of drug-resistant human melanoma cells. Thus, these preliminary studies indicate that clotrimazole has the potential to successfully treat drug resistant melanoma in the future. Citation Format: Steven D. Blake, Shelby G. McKamey, Christopher M. Tweed, David W. Koh. Evaluation of the efficacy of clotrimazole treatment in human melanoma cell lines that overexpress the multidrug resistance-associated protein (MRP) and the lung resistance-related protein (LRP) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 16. doi:10.1158/1538-7445.AM2017-16