Alterations of DNA methylation and histone modifications contribute to gene silencing in hepatocellular carcinomas
Alterations of DNA methylation and histone modifications contribute to gene silencing in hepatocellular carcinomas
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DOI：
10.1111/j.1872-034x.2007.00141.x
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发表时间：
2007-11-01
影响因子：
4.2
通讯作者：
Sekido, Yoshitaka
中科院分区：
文献类型：
--
作者：
Kondo, Yutaka;Shen, Lanlan;Sekido, Yoshitaka
目的：本研究的目的是研究肝细胞癌（HCC）中DNA甲基化和组蛋白修饰的变化。方法：采用定量亚硫酸氢盐-磷酸测序技术检测肝癌患者P16、RASSF1a、孕激素受体（PGR）和雌激素受体α (ER α)启动子的DNA甲基化。用染色质免疫沉淀法（ChIP）检测肝癌细胞系中这四个基因的组蛋白h3 -赖氨酸(K) 4、H3-K9和H3-K27的修饰。实时聚合酶链反应检测两种DNA甲基转移酶（DNMT1和DNMT3b）和三种组蛋白甲基转移酶（SUV39H1、G9a和EZH2）在HCC患者中的表达。结果：所有HCC中均检测到DNA甲基化异常。癌症中RASSF1a、PGR和alpha启动子DNA甲基化的患者在其非癌性肝组织中也存在大量DNA甲基化，而P16启动子的DNA甲基化是癌症特异性的。肝癌细胞系的表观遗传状态显示P16和RASSF1a的沉默依赖于DNA甲基化和组蛋白H3-K9甲基化。然而，PGR和ER α基因的沉默与H3-K27甲基化而非DNA甲基化关系更密切。G9a和EZH2在HCC组织中的表达高于非癌性肝组织（P < 0.01），与组蛋白状态的改变一致。结论：这些数据表明多种表观遗传沉默机制在HCC细胞中不适当地活跃。
Aim:The aim of the present study was to examine DNA methylation and histone modification changes in hepatocellular carcinomas (HCC).Methods: DNA methylation in the P16, RASSF1a, progesterone receptor (PGR) and estrogen receptor alpha (ER alpha) promoters was determined by quantitative bisulfite-pyrosequencing technique in HCC patients. Histone H3-lysine (K) 4, H3-K9 and H3-K27 modifications in all these four genes were examined by chromatin immunoprecipitation (ChIP) assay in HCC cell lines. Expression of two DNA methyltransferases (DNMT1 and DNMT3b) and three histone methyltransferases (SUV39H1, G9a and EZH2) in HCC patients was measured by real-time polymerase chain reaction.Results: Aberrant DNA methylation was detected in all the HCC. Patients with DNA methylation in the RASSF1a, PGR andER alpha promoters in cancers also had substantial DNA methylation in their non-cancerous liver tissues, whereas DNA methylation in the P16 promoter was cancer specific. Epigenetic states in HCC cell lines showed that silencing of P16 and RASSF1a depended on DNA methylation and histone H3-K9 methylation. However, silencing of the PGR and ER alpha genes was more closely related to H3-K27 methylation rather than DNA methylation. Consistent with the alteration of histone status, higher expression of G9a and EZH2 was found in HCC than in non-cancerous liver tissues (P < 0.01).Conclusion: These data suggest that multiple epigenetic silencing mechanisms are inappropriately active in HCC cells.