Carfilzomib Induces Drug Resistance in A2780 Ovarian Cancer Cells Through p53-Dependent and Caspase-3 Independent Pathways

Resistance to selective small-molecule inhibitors has been a substantial factor for limiting the efficacy of ovarian cancer. Recent studies have revealed that proteasome inhibitors induce acquired drug resistance. The possible mechanisms underlying the resistance to carfilzomib (CFZ), a recently developed inhibitor of proteasome, has not been well studied. This experimental study has aimed to determine if CFZ induces drug resistance in A2780 ovarian cancer cells through p53- and caspase-3 dependent pathways. The A2780CFZ cells were generated by continuous culturing of A2780S cells in the presence of CFZ for 4 months. The MTT cytotoxic assay was applied to compare the survival rates in A2780CFZ and A2780S cells. Also, the relative expression of p53 and caspase-3 genes were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR). The nonparametric ANOVA and Friedman tests were used for data analysis. A significant difference was observed between the viability of resistant- and sensitive-A2780 cells exposed to various concentrations of CFZ, indicating that A2780S cells have become resistant to this drug under long-term culture. Compared with A2780CFZ cells, the mRNA levels of p53 gene in A2780S cells were significantly increased after 12 (P = 0.008), and 24 hours (P = 0.034) . Also, no significant differences were observed regarding caspase-3 mRNA levels between both cell lines (P > 0.05). The findings of this study suggest that regulation of p53 gene expression in A2780CFZ cells might be the possible primary mechanism for gaining resistance against CFZ, but this might be independent of caspase cascades activation. Further studies are required to find strategies for overcoming CFZ resistance.