Characterization of Drug Resistance Protein Expression Levels in Human Melanoma Cells and Subsequent Treatment with Antifungal Agents

Abstract

The multidrug resistance (MDR) phenotype allows cancer cells to display decreased sensitivity to chemotherapy. A well‐characterized drug resistance gene in cancer is MDR1, which encodes for the p‐glycoprotein/ATP‐binding cassette (ABC) transporter. Lesser known are the roles of the multidrug resistance‐associated protein 1 (MRP1) and lung resistance‐related protein (LRP) in melanoma. Because of the previously demonstrated presence of MRP1 and LRP in human melanoma cells and the continued difficulty of overcoming MDR in melanoma treatment, here we characterized the expression levels of drug resistance genes in melanoma cell lines derived from human patients and determined their susceptibility to novel antifungal treatment. Expression levels were determined by real‐time PCR (qPCR) and immunoblot analyses. Susceptibility of cell lines to antifungal agents was analyzed by flow cytometry, cell proliferation assays, and immunoblotting after drug treatments.Several lines of human melanoma and normal skin cells were analyzed. MDR1 expression was observed in multiple melanoma lines, while increased levels of MRP1 were observed in normal skin cells and one melanoma line. Interestingly, LRP expression was highest in normal skin cells and several melanoma lines. Novel treatment with clotrimazole, an agent previously shown to eradicate melanoma cells, caused significant decreases in proliferation and increases in cell death in all MDR melanoma lines. No extensive cell death was induced by clotrimazole treatment in noncancerous human skin cells. These results indicated that clotrimazole selectively induces cytotoxicity in drug‐resistant melanoma lines. However, decreased efficacy was observed in melanoma lines that overexpressed LRP, as compared to all other melanoma lines that overexpressed MDR1 and/or MRP1. These results indicated that LRP, mostly known for facilitating drug resistance in lung and breast cancer, may also have a significant role in the ability of melanoma cells to resist the effects of conventional melanoma treatments.In conclusion, this study demonstrated the existence and differential expression levels of MDR1, MRP1, and LRP in melanoma and normal skin cell lines. Although all melanoma lines were susceptible to treatment with clotrimazole, decreased efficacy was observed in melanoma lines that overexpressed LRP. Taken together, we conclude that clotrimazole has in vitro efficacy toward the treatment of drug‐resistant human melanoma cells. However, these preliminary studies also indicated that LRP is potentially a significant facilitator of drug resistance in human melanoma.Support or Funding InformationThis research was funded by the Ohio Northern University Summer Research Stipend.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.