CircNOLC1 promotes epithelial ovarian cancer tumorigenesis and progression by binding ESRP1 and modulating CDK1 and RhoA expression

Abstract Background: Circular RNAs (circRNAs) play important roles in cancer tumorigenesis and progression, and could represent prognostic biomarkers and therapeutic targets. Herein, we demonstrated the role of circNOLC1 in epithelial ovarian cancer (EOC). Methods: CircNOLC1 expression was quantified in ovarian cancer tissues and normal ovarian tissues using quantitative real-time reverse transcriptase. After circNOLC1 overexpression or downregulation using a circNOLC1 overexpression plasmid or circNOLC1 short hairpin RNA (shRNA) transfection, respectively, ovarian cancer cell phenotypes and molecular mechanisms were examined in vivo and in vitro. Results: 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 highest in A2780, and lowest in CAOV3. Overexpression of circ-NOLC1 in CAOV3 cells increased cell proliferation, migration, and invasion, while silencing of circ-NOLC1 in A2780 cells had the opposite effect: however, neither circ-NOLC1 downregulation nor overexpression influenced nucleolar and coiled-body phosphoprotein 1 ( NOLC1 ) mRNA expression. In nude mice with subcutaneous tumors, circ-NOLC1 downregulation decreased tumor growth . Bioinformatic analysis and RNA binding protein immunoprecipitation showed that circNOLC1 could bind to epithelial splicing regulatory protein 1 (ESRP1). In addition, circ-NOLC1 overexpression significantly increased ESRP1 protein levels, and those of ras homolog family member A (RhoA) and cyclin dependent kinase 1 (CDK1); circNOLC1 downregulation had the opposite effects. The tumor-promoting effect of circNOLC1 was inhibited by knockdown of ESRP1 expression in circ-NOLC1 overexpressing cells, which might act by modulating RhoA and CDK1 expression. Conclusion: CircNOLC1 might promote EOC tumorigenesis and development by binding ESRP1 and modulating CDK1 and RhoA expression.