Reciprocal negative feedback loop between EZH2 and miR-101-1 contributes to miR-101 deregulation in hepatocellular carcinoma.

Although the tumor suppressive role of miR-101 is well documented in hepatocellular carcinoma (HCC), how the expression of miR-101 itself is regulated remains elusive. In the present study, we demonstrated that the miR-101 precursor pre-miR-101-1 could be regulated by an important epigenetic regulator, the enhancer of zeste homolog 2 (EZH2). Reporter gene assays revealed that ectopic expression of EZH2 inhibited the transcriptional activities of miR-101-1 promoter. Subsequent analyses revealed that miR-101-1 directly represses the expression of EZH2, and miR-101-1 and EZH2 form a reciprocal negative feedback loop as indicated by the fact that ectopic mature miR-101 could induce endogenous pre-miR-101-1 expression. This mature miR-101-induced pre-miR-101 expression was specific to pre-miR-101-1 and depended on EZH2 activities. Moreover, our results also demonstrated that similar antitumor effects can be achieved either by ectopic miR-101 or EZH2 silencing in HCC cells. These findings show that elevated EZH2 contributes to miR-101 deregulation in HCC and highlight the coordinated role of miR-101 and EZH2 in hepatocarcinogenesis.