miR-340 Reverses Cisplatin Resistance of Hepatocellular Carcinoma Cell Lines by Targeting Nrf2-dependent Antioxidant Pathway

Many chemotherapeutic agents have been successfully used to treat hepatocellular carcinoma (HCC);however, the development of chemoresistance in liver cancer cells usually results in a relapse and worseningof prognosis. It has been demonstrated that DNA methylation and histone modification play crucial roles inchemotherapy resistance. Currently, extensive research has shown that there is another potential mechanismof gene expression control, which is mediated through the function of short noncoding RNAs, especially formicroRNAs (miRNAs), but little is known about their roles in cancer cell drug resistance. In present study, bytaking advantage of miRNA effects on the resistance of human hepatocellular carcinoma cells line to cisplatin, ithas been demonstrated that miR-340 were significantly downregulated whereas Nrf2 was upregulated in HepG2/CDDP (cisplatin) cells, compared with parental HepG2 cells. Bioinformatics analysis and luciferase assays ofNrf2-3’-untranslated region-based reporter constructor indicated that Nrf2 was the direct target gene of miR-340, miR-340 mimics suppressing Nrf2-dependent antioxidant pathway and enhancing the sensitivity of HepG2/CDDP cells to cisplatin. Interestingly, transfection with miR-340 mimics combined with miR-340 inhibitorsreactivated the Nrf2 related pathway and restored the resistance of HepG2/CDDP cells to CDDP. Collectively,the results first suggested that lower expression of miR-340 is involved in the development of CDDP resistancein hepatocellular carcinoma cell line, at least partly due to regulating Nrf2-dependent antioxidant pathway.