[Effect of circBIRC6 targeting miR-367-3p on cisplatin resistance of ovarian cancer cells].

Objective: To explore the effect of circBIRC6 on cisplatin resistance of ovarian cancer cells and the molecular mechanism. Methods: The ovarian cancer cell line SKOV3 and ovarian cancer cisplatin-resistant cell line SKOV3 / DDP were cultured in vitro, and treated with different concentrations of cisplatin. SKOV3 and SKOV3/DDP cells were transfected with si-NC, si-circBIRC6, si-circBIRC6+ anti-miR-NC, si-circBIRC6+ anti-miR-367-3p by liposome-mediated method, which were denoted as DDP+ si-NC group, DDP+ si-circBIRC6 group, DDP+ si-circBIRC6+ anti-miR-NC group and DDP+ si-circBIRC6+ anti-miR-367-3p group, respectively, and then were treated with 2 µg/ml cisplatin for 24 hours. The cell proliferation inhibition rate was detected by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide method, and the half inhibitory concentration (IC(50)) value of cisplatin was calculated. Real-time fluorescent quantitative polymerase chain reaction was used to detect the transcriptional levels of circBIRC6 and miR-367-3p. Flow cytometry was used to detect the apoptotic rate. Dual luciferase report experiment verified the targeting relationship of circBIRC6 and miR-367-3p. Western blot was used to detect the expressions of Cyclin D1, Bcl-2, p21, Bax. Results: The expression levels of circBIRC6 in SKOV3 cells were 1.00±0.05, significantly lower than 3.04±0.24 in SKOV3/DDP cells (P<0.001). The expression levels of miR-367-3p in SKOV3 cells were 1.00±0.08, significantly higher than 0.54±0.05 in SKOV3/DDP cells (P<0.001). The cell proliferation inhibition rates of SKOV3 cells and SKOV3/DDP cells were (22.47±2.04)% and (8.84±0.71)%, the IC(50) values of SKOV3 cells and SKOV3/DDP cells were 6.65±0.94 and 28.18±4.91, respectively, with significant difference (P<0.05). The proliferation inhibition rate and apoptosis rate of SKOV3 cells in DDP+ si-NC group[(22.19±2.19)% and (10.98±1.12)%] were lower than those in DDP+ si-circBIRC6 group [(74.18±5.36)% and (32.91±3.19)%, all P<0.05]. The proliferation inhibition rate and apoptosis rate of SKOV3/DDP cells[(8.71±0.87)% and (7.39±0.63)%] were lower than those of DDP+ si-circBIRC6 group [(40.85±4.07)% and (25.31±2.53)%, all P<0.05]. The protein expression levels of Cyclin D1 and Bcl-2 in SKOV3 and SKOV3/DDP cells in DDP+ si-circBIRC6 group were lower than those in DDP+ si-NC group, and the protein expression levels of p21 and Bax were higher than those in DDP+ si-NC group (all P<0.05). The dual luciferase report experiment confirmed that circBIRC6 targeted miR-367-3p. Inhibition of miR-367-3p expression reduced the effect of circBIRC6 deletion on ovarian cancer cell proliferation, apoptosis and cisplatin resistance. Conclusion: Knockdown of circBIRC6 may inhibit the proliferation of ovarian cancer cisplatin-resistant cells and induce apoptosis by up-regulating the expression of miR-367-3p, therefore impair the cisplatin resistance of these cells.