Xu Leibo, Lin Junlong, Deng Wanyu, Luo Weixin, Huang Yipei, Liu Chao-Qun, Zhang Fa-Peng, Qin Yu-Fei, Wong Ping-Pui, Liu Chao
Department of Biliary-Pancreatic Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, 510120, China.
Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, 510120, China.
Oncogenesis. 2020 Nov 9;9(11):101. doi: 10.1038/s41389-020-00284-w.
EZH2, a histone methyltransferase, has been shown to involve in cancer development and progression via epigenetic regulation of tumor suppressor microRNAs, whereas BMI1, a driver of hepatocellular carcinoma (HCC), is a downstream target of these microRNAs. However, it remains unclear whether EZH2 can epigenetically regulate microRNA expression to modulate BMI1-dependent hepatocarcinogenesis. Here, we established that high EZH2 expression correlated with enhanced tumor size, elevated metastasis, increased relapse, and poor prognosis in HCC patients. Further clinical studies revealed that EZH2 overexpression was positively correlated to its gene copy number gain/amplification in HCC. Mechanistically, EZH2 epigenetically suppressed miR-200c expression both in vitro and in vivo, and more importantly, miR-200c post-transcriptionally regulated BMI1 expression by binding to the 3'-UTR region of its mRNA. Furthermore, miR-200c overexpression inhibits the growth of HCC cells in vivo. Silencing miR-200c rescued the tumorigenicity of EZH2-depleted HCC cells, whereas knocking down BMI1 reduced the promoting effect of miR-200c depletion on HCC cell migration. Finally, combination treatment of EZH2 and BMI1 inhibitors further inhibited the viability of HCC cells compared with the cells treated with EZH2 or BMI1 inhibitor alone. Our findings demonstrated that alteration of EZH2 gene copy number status induced BMI1-mediated hepatocarcinogenesis via epigenetically silencing miR-200c, providing novel therapeutic targets for HCC treatment.
EZH2是一种组蛋白甲基转移酶,已被证明可通过对肿瘤抑制性微小RNA进行表观遗传调控而参与癌症的发生和发展,而BMI1作为肝细胞癌(HCC)的驱动因子,是这些微小RNA的下游靶点。然而,EZH2是否能通过表观遗传调控微小RNA表达来调节BMI1依赖性肝癌发生仍不清楚。在此,我们证实,EZH2高表达与HCC患者肿瘤大小增加、转移增多、复发增加及预后不良相关。进一步的临床研究表明,EZH2过表达与其在HCC中的基因拷贝数增加/扩增呈正相关。机制上,EZH2在体外和体内均可通过表观遗传抑制miR-200c表达,更重要的是,miR-200c通过与其mRNA的3'-UTR区域结合,在转录后调控BMI1表达。此外,miR-200c过表达可在体内抑制HCC细胞生长。沉默miR-200c可挽救EZH2缺失的HCC细胞的致瘤性,而敲低BMI1可降低miR-200c缺失对HCC细胞迁移的促进作用。最后,与单独使用EZH2或BMI1抑制剂处理的细胞相比,联合使用EZH2和BMI1抑制剂进一步抑制了HCC细胞的活力。我们的研究结果表明,EZH2基因拷贝数状态的改变通过表观遗传沉默miR-200c诱导BMI1介导的肝癌发生,为HCC治疗提供了新的治疗靶点。