Circ-NOLC1 promotes epithelial ovarian cancer tumorigenesis and progression by binding ESRP1 and modulating CDK1 and RhoA expression

Circular RNAs (circRNAs) play important roles in cancer tumorigenesis and progression, representing prognostic biomarkers and therapeutic targets. In this case, we demonstrated the role of circ-NOLC1 in epithelial ovarian cancer (EOC). Our results have shown that Circ-NOLC1 expression was higher in EOC tissues than in normal tissues, and was positively associated with FIGO stage, differentiation. Among ovarian cancer cell lines, circ-NOLC1 expression was the highest in A2780, and lowest in CAOV3. Overexpression of circ-NOLC1 in CAOV3 cells increased cell proliferation, migration, and invasion ability, whereas silencing of circ-NOLC1 in A2780 cells had the opposite effect: however, neither circ-NOLC1 downregulation nor overexpression influenced NOLC1 mRNA expression. In nude mice with subcutaneous tumors, circ-NOLC1 downregulation decreased tumor growth. Bioinformatic analysis and RNA-binding protein immunoprecipitation showed that circ-NOLC1 could bind to ESRP1. In addition, the overexpression of circ-NOLC1 significantly increased ESRP1, RhoA, and CDK1 protein and mRNA expression level; circ-NOLC1 downregulation had the opposite effects. The tumor-promoting effect of circ-NOLC1 was inhibited by knockdown of ESRP1, CDK1, or RhoA expression in circ-NOLC1 -overexpressing cells, which might act by modulating RhoA and CDK1 expression. In conclusion, our study demonstrated that Circ-NOLC1 might promote EOC tumorigenesis and development by binding ESRP1 and modulating CDK1 and RhoA expression.