miR-203a regulates bladder cancer cell proliferation and radiosensitivity by targeting CDK6 / 中华放射肿瘤学杂志

ABSTRACT

Objective:To investigate the expression of miR-203a in bladder cancer (BC) cell lines (RT-112, T24, 5637, UM-UC-3) and evaluate the effects on BC cell proliferation and radiosensitivity.Methods:Mir-203a mimics, mir-203a inhibitor, CDK6 siRNA, CDK6 expression plasmid and corresponding negative controls were transfected into BC cells. Quantitative real-time PCR was used to detect the expression of miR-203a in BC cell lines and human bladder epithelial immortalized cell line (SV-HUC-1). CCK8 assay was used to investigate the regulation of miR-203a and cyclin-dependent kinases 6(CDK6) on the proliferation of BC cells. Colony formation assay was performed to assess the effect of miR-203a and CDK6 on the radiosensitivity of BC cells. The target gene of miR-203a was confirmed by luciferase reporter assay. The effect of miR-203a on CDK6 protein expression was detected by Western blot. Multi-group comparison was performed by one-way ANOVA and two-group comparison was conducted by t-test. Results:Compared with the SV-HUC-1 cells, the expression levels of miR-203a in RT-112, T24, 5637 and UM-UC-3 cells were significantly down-regulated (all P<0.05). Compared with NC group, overexpression of miR-203a significantly inhibited the proliferation of BC cells, whereas knockdown of miR-203a significantly promoted the proliferation of BC cells (both P<0.05). Compared with NC group, overexpression of miR-203a significantly increased the sensitivity of BC cells to radiotherapy, whereas knockdown of miR-203a significantly weakened the sensitivity of BC cells to radiotherapy (both P<0.05). CDK6 was the target of miR-203a. Compared with NC group, overexpression of miR-203a significantly down-regulated the expression level of CDK6 protein, whereas knockdown of miR-203a significantly up-regulated the expression level of CDK6 protein (both P<0.05). After overexpression of CDK6 in T24 and UM-UC-3 cells transfected with miR-203a mimics, the cell proliferation ability was significantly increased, whereas the sensitivity to radiotherapy was significantly decreased compared with mir-203a mimics (both P<0.05). After CDK6 was silenced in RT-112 and 5637 cells transfected with miR-203a inhibitor, the proliferation ability of cells was significantly decreased, whereas the sensitivity to radiotherapy was remarkably increased compared with miR-203a inhibitor group (both P<0.05). Conclusion:miR-203a can serves as a tumor suppressor gene to inhibit the proliferation of BC cells and enhance the radiosensitivity of BC cells.