Circadian Gene CLOCK Affects Drug-Resistant Gene Expression and Cell Proliferation in Ovarian Cancer SKOV3/DDP Cell Lines Through Autophagy

Abnormal autophagy regulation affects the chemoresistance of ovarian cancer, during which the circadian gene clock may play a major role. In this study, RNA interference plasmid pSUPER-Clock and overexpression plasmid pcDNA3.1-Clock of CLOCK were used to stably transfect the SKOV3/DDP cells by lipofection. Upon screening, the in vitro transfected cell lines with pSUPER-Clock, the autophagy level, and G(0)/G(1) phase cells were significantly reduced, and the expression levels of Clock, LC3, P-gp, and MRP2 were inhibited. In contrast, the autophagy level and G(0)/G(1) phase cells in cell lines transfected with pcDNA3.1-Clock were significantly increased, and the expressions of Clock, LC3, P-gp, and MRP2 were enhanced. In comparison with the untransfected control group showed the percentage of apoptotic cells in SKOV3/DDP cell lines of Clock interfering expression group after cisplatin treatment was significantly increased while the survival was substantially reduced. These results indicated that inhibiting the circadian gene Clock expression can reverse the cisplatin resistance of ovarian cancer SKOV3/DDP cell lines by affecting the protein expression of drug resistance genes during which autophagy plays an important role. The CLOCK gene may be designated as a novel candidate for targeted gene therapy in drug-resistant ovarian cancer.