(-)-Epigallocatechin-3-gallate reactivates silenced tumor suppressor genes, Cip1/p21 and p16INK4a, by reducing DNA methylation and increasing histones acetylation in human skin cancer cells
(-)-Epigallocatechin-3-gallate reactivates silenced tumor suppressor genes, Cip1/p21 and p16INK4a, by reducing DNA methylation and increasing histones acetylation in human skin cancer cells
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DOI：
10.1093/carcin/bgq285
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发表时间：
2011-04-01
期刊：
影响因子：
4.7
通讯作者：
Katiyar, Santosh K.
中科院分区：
文献类型：
--
作者：
Nandakumar, Vijayalakshmi;Vaid, Mudit;Katiyar, Santosh K.
绿茶儿茶素的抗皮肤致癌作用已在体外和体内模型中进行了广泛的研究，但确切的表观遗传学分子机制仍不清楚。越来越多的数据表明，饮食中的植物化学物质可能通过改变细胞中的表观遗传过程来改变癌症风险。本研究旨在研究茶儿茶素，特别是(-)-表没食子儿茶素没食子酸酯(EGCG)是否会改变表观遗传学事件，以调节皮肤癌细胞中DNA甲基化沉默的肿瘤抑制基因。以人表皮样癌A431细胞为模型，采用细胞染色、Western blotting、斑点印迹分析、实时定量聚合酶链式反应和酶活性检测等方法，对EGCG作用后A431细胞的DNA甲基化、组蛋白修饰和抑癌基因表达进行了详细的研究。我们的研究表明，EGCG治疗以剂量依赖的方式降低了A431细胞的整体DNA甲基化水平。EGCG可降低DNMT1、DNMT3a和DNMT3b的5-甲基胞嘧啶水平、DNA甲基转移酶(DNMT)活性、信使RNA(MRNA)和蛋白水平。EGCG降低了组蛋白脱乙酰酶活性，增加了组蛋白H3(H3-Lys 9和14)上的乙酰化赖氨酸9和14以及组蛋白H4上的乙酰化赖氨酸5、12和16的水平，但降低了H3-Lys 9的甲基化水平。此外，EGCG治疗导致沉默的肿瘤抑制基因p16(INK4a)和Cip1/p21的mRNA和蛋白重新表达。总之，我们的研究为EGCG的表观遗传作用机制提供了新的见解，这可能有助于皮肤癌的化学预防，并可能对表观遗传治疗具有重要意义。
The anti-skin carcinogenic effects of green tea catechins have been studied extensively in vitro and in vivo models but the precise epigenetic molecular mechanisms are still unclear. Accumulating data suggest that dietary phytochemicals may alter cancer risk by modifications of epigenetic processes in the cells. The present study was designed to investigate whether tea catechins, particularly (-)-epigallocatechin-3-gallate (EGCG), would modify epigenetic events to regulate DNA methylation-silenced tumor suppressor genes in skin cancer cells. DNA methylation, histone modifications and tumor suppressor gene expressions were studied in detail using human epidermoid carcinoma A431 cells as an in vitro model after EGCG treatment using cytostaining, western blotting, dot blot analysis, real-time polymerase chain reaction and enzymatic activity assays. Our study shows that EGCG treatment decreased global DNA methylation levels in A431 cells in a dose-dependent manner. EGCG decreased the levels of 5-methylcytosine, DNA methyltransferase (DNMT) activity, messenger RNA (mRNA) and protein levels of DNMT1, DNMT3a and DNMT3b. EGCG decreased histone deacetylase activity and increased levels of acetylated lysine 9 and 14 on histone H3 (H3-Lys 9 and 14) and acetylated lysine 5, 12 and 16 on histone H4 but decreased levels of methylated H3-Lys 9. Additionally, EGCG treatment resulted in re-expression of the mRNA and proteins of silenced tumor suppressor genes, p16(INK4a) and Cip1/p21. Together, our study provides new insight into the epigenetic mechanism of action of EGCG that may contribute to the chemoprevention of skin cancer and may have important implications for epigenetic therapy.