Effects Of Downregulating CDK9 Expression On Proliferation Of Hepatoma Cells By MiR-206

miR-206 plays important roles in regulate cell proliferation and apoptosis and relates with various types of cancer.Cyclin-dependent kinase 9(CDK9)stimulates excessive production of abundant pro-survival proteins,leading to impaired apoptosis of cancer cells.The objective of this study was to determine whether CDK9 was involved in miR-206 mediated suppression of proliferation and apoptosis in human hepatocellular carcinoma(HCC).Objective: The objective of this study is to determine whether CDK9 was involved in miR-206 mediated suppression of proliferation and apoptosis in human hepatocellular carcinoma(HCC).Methods:1.The miR-206 and CDK9 m RNA expression assay by quantitative PCR(qPCR).2.Two well-used bioinformatics tools(Target Scan and miRanda)were used to predict the potential sites of m R-206 miRNA at the CDK9 3′-UTR.3.Luciferase reporter assays were performed to determine the biological effect of miR-206 on CDK9.4.The expression levels of CDK9,RNA PolⅡSer2 phosphorylation and its downstream target gene Mcl-1 were detected by Western Blot.5.The Cell Counting Kit(CCK-8)assay was used to analyze the cell proliferation.6.The cell apoptosis assays and the cell-cycle phase distribution was detected by flow cytometry.Results:1.The expression level of miR-206 was significantly lower in HepG2,Bell7402,and HLE cell lines than normal hepatic cell line(L02).Meanwhile,CDK9 was upregulated in HepG2,Bell7402,and HLE cell lines.2.Dual luciferase reporter assay demonstrated that CDK9 was a direct and functional target gene of miR-206.miR-206 directly inhibits the protein expression of CDK9 via its 3’-UTR.3.Transfection of miR-206 mimics suppressed CDK9 expression and triggered a decrease in RNA PolⅡSer2 phosphorylation and Mcl-1 level in the HCC cells.miR-2064.Disruption of CDK9 activity with shRNA-CDK9 and CDK9 specific inhibitor also inhibited cell proliferation,arrested cell cycle and induced cell apoptosis in Bell7402 and HepG2 cells which is similar to the effect of miR-206 on HCC cell lines.Conclusions:1.The levels of CDK9 was higher and the level of miR-206 was lower in HCC cell lines compared with normal hepatocytes.2.MiR-206 inhibits the proliferation of hepatoma cells through negatively regulating CDK9-related pathways.