A CCRK-EZH2 epigenetic circuitry drives hepatocarcinogenesis and associates with tumor recurrence and poor survival of patients
A CCRK-EZH2 epigenetic circuitry drives hepatocarcinogenesis and associates with tumor recurrence and poor survival of patients
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CCRK-EZH2 表观遗传电路驱动肝癌发生，并与肿瘤复发和患者生存率低相关
DOI：
10.1016/j.jhep.2014.11.040
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发表时间：
2015-05-01
影响因子：
25.7
通讯作者：
Cheng, Alfred S. L.
中科院分区：
文献类型：
--
作者：
Feng, Hai;Yu, Zhuo;Cheng, Alfred S. L.
背景与目的：异常染色质修饰是肝细胞癌（HCC）的一个关键特征，其特点是强烈的性别二态性。 zeste同系物增强子2（EZH2）和细胞周期相关激酶（CCRK）均与肝癌发生有关，但这两种致癌因子是否具有功能性串扰尚不清楚。方法：通过集落形成和软琼脂实验、异种移植、原位和二乙基亚硝胺诱导的HCC模型来确定转基因表达和RNA干扰后的细胞增殖和致瘤性。通过染色质免疫沉淀、定点诱变、荧光素酶报告基因、免疫共沉淀和表达分析来评估基因调控。临床标本中的蛋白质水平与临床病理参数和患者存活率相关。结果：永生化人肝细胞中的异位CCRK表达增加了EZH2和组蛋白H3赖氨酸27三甲基化(H3K27me3)以刺激增殖和肿瘤形成。相反，敲低 CCRK 会降低 EZH2/H3K27me3 水平并减少 HCC 细胞生长，这可以通过 EZH2 过表达来挽救。从机制上讲，CCRK 磷酸化 GSK-3b 激活 b-catenin/TCF/E2F1/EZH2 转录反馈环，从而在表观遗传上增强雄激素受体 (AR) 信号传导。同时，CCRK 对 AKT/EZH2 的磷酸化促进了 EZH2-AR 共同占据 CCRK 启动子及其随后的转录激活，从而形成自我强化电路。慢病毒介导的 CCRK 敲低可消除磷酸化转录网络，从而防止二乙基亚硝胺诱导的致瘤性。更重要的是，人类 HCC 中 CCRK-EZH2 回路的过度激活与肿瘤复发和不良生存相关。结论：这些发现揭示了肝癌发生中的表观遗传恶性循环，该循环通过 CCRK 和 EZH2 的相互调节发挥作用，为 HCC 提供了新的治疗策略。 (C) 2014 年欧洲肝脏研究协会。由 Elsevier B.V. 出版。保留所有权利。
Background & Aims: 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.Methods: 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.Results: 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-3b phosphorylation by CCRK activated a b-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.Conclusions: These findings uncover an epigenetic vicious cycle in hepatocarcinogenesis that operates through reciprocal regulation of CCRK and EZH2, providing novel therapeutic strategy for HCC. (C) 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.