MicroRNAs mediate regulation of chemoresistance of hepatocellular carcinoma cells with involvement of p53 tumour suppressor.

Abstract

BACKGROUND: Accumulating studies have indicated the involvement of microRNAs (miRNAs) in the progression and treatment of human hepatocellular carcinoma (HCC). miRNAs mediate drug resistance of HCC and regulating miRNAs may give rise to novel strategy of treatment of HCC. The aim of this study is to investigate the involvement of particular miRNA in regulating chemosensitivity of HCC cells and its possible mechanism. MATERIAL AND METHOD: Human HCC cell lines were used. Expression of mRNAs and miRNAs were detected by quantitative real-time PCR; Profiling of miRNAs were probed with on-chip microarray; protein expression was detected by immunoblotting; prediction and identification of miRNA-targeted genes were conducted by TargetScan and luciferase reporter assay. RESULTS: We identify miR-23a as one of the effective miRNAs that mediates chemosensitivity of HCC towards treatment of topoisomerase II inhibitor VP-16. miR-23a expression was overexpressed in human HCC tissue and HCC cell lines, which naturally led to reduced of topoisomerase I by directly targeting to 3’UTR of its mRNA. Reduced expression of topoisomerases I resulted in an overall dropdown of total topoisomerases level in HCC cells, leading to augment of DNA damage cause by topoisomerase II inhibitor due to the inadequate DNA repair by topoisomerases. Expression of miR-23a was transcriptionally controlled by a tumour suppressor p53, which was evidenced by up-regulation of both primary and precursor miR-23a in HCC cells upon exposure of p53 inducers. Furthermore, we identified a regulatory loop between p53 and miR-23a. Up-regulation of miR-23a can induce expression of p53-transcription targets including GADD45a and p21, while miR-23a inhibition reduced their transcription. Interestingly, up-regulation of miR-23a can further initiate phosphorylation of p53, which leads to nuclear localisation of p53 and improves its binding to promoter regions of targeted genes. Expression profile of miRNAs in HCC cells exposed to p53 inducers proved that miR-23a is one of the most-upregulated miRNAs in HCC cells. CONCLUSION: Our study proved miR-23a as a potential target that regulates chemoresistance of HCC cells.