[Effect of CASC19 on proliferation, apoptosis and radiation sensitivity of cervical cancer cells by regulating miR-449b-5p expression].

To investigate the effects of cancer susceptibility candidate gene 19 (CASC19) regulating the expression of microRNA-449b-5p (miR-449b-5p) on the proliferation, apoptosis and radiation sensitivity of cervical cancer cells. (1) HeLa cells of cervical cancer cell line were cultured. HeLa cells were irradiated with X-ray at different doses (0, 2, 4, 6, 8 Gy, respectively), then the expression level of CASC19 mRNA and miR-449b-5p were detected by real-time quantitative PCR. (2) HeLa cell proliferation, apoptosis, radiation sensitivity (expressed as a survival fraction) and its related protein expression included cyclin D1, cleaved-caspase-3, and histone variant H2AX (γ-H2AX) were examined after different treatment including silencing CASC19 expression, over-expressing miR-449b-5p, down-regulating miR-449b-5p and silencing CASC19 expression. (3) The dual luciferase reporter gene experiment and real-time quantitative PCR technology were used to verify the targeting relationship between CASC19 and miR-449b-5p. (1) With the increase of X-ray irradiation different dose (0, 2, 4, 6, 8 Gy), the expression level of CASC19 mRNA in HeLa cells gradually increased (502.681, 0.000), and the expression level of miR-449b-5p gradually decreased (202.936, 0.000).(2) After silencing CASC19 expression or over-expressing miR-449b-5p, the survival rate of HeLa cells was significantly reduced (0.05), the apoptosis rate was significantly increased (0.05), the survival fraction was significantly reduced (0.05), the expression level of cyclin D1 protein was significantly reduced (0.05), and the expression levels of cleaved-caspase-3 and γ-H2AX protein were significantly increased (0.05). After down-regulating miR-449b-5p and silencing CASC19 expression, the survival rate of HeLa cells was significantly reduced (0.05), the apoptosis rate was significantly increased (0.05), the survival fraction was significantly reduced (0.05), the expression levels of cyclin D1 and γ-H2AX protein were significantly increased (0.05), and the expression level of cleaved-caspase-3 was significantly decreased (0.05). (3) Over expression of miR-449b-5p could significantly reduce the luciferase activity of CASC19 wild type (1.00±0.09 versus 0.37±0.05, 0.01), but there were no significant effect on the luciferase activity of CASC19 mutant type (0.92±0.07 versus 0.94±0.05, 0.05). After the expression of CASC19 was silenced, the expression level of miR-449b-5p in HeLa cells increased significantly (1.00±0.12 versus 4.84±0.49, 0.05). After overexpression of CASC19, the expression level of miR-449b-5p in HeLa cells was significantly reduced (1.00±0.09 versus 0.38±0.04, 0.05). CASC19 in HeLa cells negatively regulates the expression of miR-449b-5p, and down-regulating the expression of miR-449b-5p could partially reverse the effects of silencing CASC19 on HeLa cell proliferation, apoptosis and radiation sensitivity.