%0 Journal Article
%T A CCRK-EZH2 epigenetic circuitry drives hepatocarcinogenesis and associates with tumor recurrence and poor survival of patients.
%A Feng H
%A Yu Z
%A Tian Y
%A Lee YY
%A Li MS
%A Go MY
%A Cheung YS
%A Lai PB
%A Chan AM
%A To KF
%A Chan HL
%A Sung JJ
%A Cheng AS
%J J Hepatol
%V 62
%N 5
%D May 2015
%M 25500144
%F 30.083
%R 10.1016/j.jhep.2014.11.040
%X <B>OBJECTIVE: </B>Aberrant chromatin modification is a key feature of hepatocellular carcinoma (HCC), which is characterized by strong sexual dimorphism. Both enhancer of zeste homolog 2 (EZH2) and cell cycle-related kinase (CCRK) contribute to hepatocarcinogenesis, yet whether the two oncogenic factors have functional crosstalk is unknown.<BR><B>METHODS: </B>Cellular proliferation and tumorigenicity upon transgenic expression and RNA interference were determined by colony formation and soft agar assays, xenograft, orthotopic and diethylnitrosamine-induced HCC models. Gene regulation was assessed by chromatin immunoprecipitation, site-directed mutagenesis, luciferase reporter, co-immunoprecipitation and expression analyses. Protein levels in clinical specimens were correlated with clinicopathological parameters and patient survival rates.<BR><B>RESULTS: </B>Ectopic CCRK expression in immortalized human liver cells increased EZH2 and histone H3 lysine 27 trimethylation (H3K27me3) to stimulate proliferation and tumor formation. Conversely, knockdown of CCRK reduced EZH2/H3K27me3 levels and decreased HCC cell growth, which could be rescued by EZH2 over-expression. Mechanistically, GSK-3β phosphorylation by CCRK activated a β-catenin/TCF/E2F1/EZH2 transcriptional feedback loop to epigenetically enhance androgen receptor (AR) signaling. Simultaneously, the phosphorylation of AKT/EZH2 by CCRK facilitated the co-occupancy of CCRK promoter by EZH2-AR and its subsequent transcriptional activation, thus forming a self-reinforcing circuitry. Lentiviral-mediated knockdown of CCRK, which abrogated the phosphorylation-transcriptional network, prevented diethylnitrosamine-induced tumorigenicity. More importantly, the hyperactivation of the CCRK-EZH2 circuitry in human HCCs correlated with tumor recurrence and poor survival.<BR><B>CONCLUSIONS: </B>These findings uncover an epigenetic vicious cycle in hepatocarcinogenesis that operates through reciprocal regulation of CCRK and EZH2, providing novel therapeutic strategy for HCC.