Interfering EZH2 Expression Reverses the Cisplatin Resistance in Human Ovarian Cancer by Inhibiting Autophagy

We aimed to determine the effects of the inhibition of enhancer of zeste homolog 2 (EZH2) gene expression on the cisplatin resistance of the human ovarian cancer cell line, SKOV3/DDP, and to identify the underlying mechanisms. SKOV3/DDP cells were stably transfected with pSUPER-EZH2 (EZH2 RNA interference plasmid) or pcDNA3.1-EZH2 (EZH2 gene overexpression plasmid) using the lipofection method. Real-time fluorescence quantitative reverse transcription polymerase chain reaction and western blotting confirmed that EZH2 expression was downregulated in pSUPER-EZH2-transfected cells. Flow cytometry revealed that EZH2 inhibition did not induce apoptosis, but significantly inhibited autophagy. In addition, it significantly increased the expression of the cellular senescence-signaling proteins p14(ARF), p16(INK4a), p53, pRb, and p21, and significantly decreased the expression of cyclin-dependent kinase (CDK) 1, CDK2, and H3K27me3. Cellular senescence was characterized by a significant increase in the G(0)/G(1) ratio and the restoration of sensitivity to cisplatin in the drug-resistant cells. These findings suggest that interfering with EZH2 expression can inhibit SKOV3/DDP cell autophagy and reverse resistance to cisplatin. The underlying mechanisms could be associated with the regulation of the cellular senescence-signaling pathway.