Circulating exosomal circFoxp1 confers cisplatin resistance in epithelial ovarian cancer cells

OBJECTIVE: Early detection and treatment are particularly important to epithelial ovarian cancer (EOC). Studies have shown that circular RNA (circRNA) dysregulation is associated with the proliferation and metastasis of ovarian cancer cells. This study focused on the role of serum exosomal circular forkhead box protein P1 (circFoxp1) on survival outcome and cisplatin (DDP) resistance in patients with EOC. METHODS: Quantitative polymerase chain reaction, 5-ethynyl-2′-deoxyuridine (EdU) staining, CCK-8, luciferase reporter assay, RNA immunoprecipitation, tumor xenograft in nude mice, and bioinformatic analysis were performed. RESULTS: Circulating exosomal circFoxp1 was significantly increased in patients with EOC, especially in DDP-resistant EOC patients. circFoxp1 expression was positively associated with International Federation of Gynecology and Obstetrics stage, primary tumor size, lymphatic metastasis, distant metastasis, residual tumor diameter, and clinical response. Exosomal circFoxp1 also was an independent factor predicting survival and disease recurrence in patients with EOC. Overexpression of circFoxp1 could promote cell proliferation and confer DDP resistance, while knockdown of circFoxp1 could inhibit cell proliferation and enhance DDP sensitivity in vitro and in vivo. In addition, miR-22 and miR-150-3p mimic treatment attenuated circFoxp1-meadiated DDP resistance, while miR-22 and miR-150-3p inhibitor treatment enhanced DDP resistance that mitigated by circFoxp1 knockdown. Furthermore, circFoxp1 positively regulated the expression of CCAAT enhancer binding protein gamma (CEBPG) and formin like 3 (FMNL3) through miR-22 and miR-150-3p. CONCLUSIONS: circFoxp1 is an oncogene in EOC cells and can confer DDP resistance to EOC cells. Circulating exosomal circFoxp1 can be used as a biomarker and potential therapeutic target for EOC.