Chen Qian, Zheng Peng-Sheng, Yang Wen-Ting
Department of Reproductive Medicine, The First Affiliated Hospital of The Medical College, Xi'an Jiaotong University, Xi'an, The People's Republic of China.
Section of Cancer Stem Cell Research, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education of The People's Republic of China, Xi'an, The People's Republic of China.
Oncotarget. 2016 Jun 14;7(24):36115-36129. doi: 10.18632/oncotarget.8741.
Enhancer of zeste homolog 2 (EZH2), a catalytic core component of the Polycomb repressive complex 2 (PRC2), stimulates the silencing of target genes through histone H3 lysine 27 trimethylation (H3K27me3). Recent findings have indicated EZH2 is involved in the development and progression of various human cancers. However, the exact mechanism of EZH2 in the promotion of cervical cancer is largely unknown. Here, we show that EZH2 expression gradually increases during the progression of cervical cancer. We identified a significant positive correlation between EZH2 expression and cell proliferation in vitro and tumor formation in vivo by the up-regulation or down-regulation of EZH2 using CRISPR-Cas9-mediated gene editing technology and shRNA in HeLa and SiHa cells. Further investigation indicated that EZH2 protein significantly accelerated the cell cycle transition from the G0/G1 to S phase. TOP/FOP-Flash reporter assay revealed that EZH2 significantly activated Wnt/β-catenin signaling and the target genes of Wnt/β-catenin pathway were up-regulated, including β-catenin, cyclin D1, and c-myc. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays confirmed that EZH2 inhibited the expression of glycogen synthase kinase-3β (GSK-3β) and TP53 through physically interacting with motifs in the promoters of the GSK-3β and TP53 genes. Additionally, blockage of the Wnt/β-catenin pathway resulted in significant inhibition of cell proliferation, and activation of the Wnt/β-catenin pathway resulted in significant enhancement of cell proliferation, as induced by EZH2. Taken together, our data demonstrate that EZH2 promotes cell proliferation and tumor formation in cervical cancer through activating the Wnt/β-catenin pathway by epigenetic silencing via GSK-3β and TP53.
zeste 同源物 2 增强子（EZH2）是多梳抑制复合物 2（PRC2）的催化核心成分，通过组蛋白 H3 赖氨酸 27 三甲基化（H3K27me3）促进靶基因沉默。最近的研究发现表明 EZH2 参与了多种人类癌症的发生和发展。然而，EZH2 在宫颈癌发生发展中的具体机制尚不清楚。在此，我们发现 EZH2 的表达在宫颈癌进展过程中逐渐升高。我们利用 CRISPR-Cas9 介导的基因编辑技术和 shRNA 在 HeLa 和 SiHa 细胞中上调或下调 EZH2，发现 EZH2 表达与体外细胞增殖及体内肿瘤形成之间存在显著正相关。进一步研究表明，EZH2 蛋白显著加速了细胞周期从 G0/G1 期向 S 期的转变。TOP/FOP-Flash 报告基因检测显示，EZH2 显著激活 Wnt/β-连环蛋白信号通路，Wnt/β-连环蛋白通路的靶基因上调，包括β-连环蛋白、细胞周期蛋白 D1 和 c-myc。此外，双荧光素酶报告基因和染色质免疫沉淀（ChIP）检测证实，EZH2 通过与糖原合酶激酶-3β（GSK-3β）和 TP53 基因启动子中的基序直接相互作用，抑制 GSK-3β和 TP53 的表达。此外，阻断 Wnt/β-连环蛋白通路可显著抑制细胞增殖，激活 Wnt/β-连环蛋白通路则可显著增强 EZH2 诱导的细胞增殖。综上所述，我们的数据表明，EZH2 通过对 GSK-3β和 TP53 进行表观遗传沉默来激活 Wnt/β-连环蛋白通路，从而促进宫颈癌的细胞增殖和肿瘤形成。
