In vitro mechanism for downregulation of ER-α expression by epigallocatechin gallate in ER+/PR+ human breast cancer cells.
In vitro mechanism for downregulation of ER-α expression by epigallocatechin gallate in ER+/PR+ human breast cancer cells.
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DOI：
10.1002/mnfr.201200560
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发表时间：
2013-05
影响因子：
5.2
通讯作者：
Andò S
中科院分区：
文献类型：
--
作者：
De Amicis F;Russo A;Avena P;Santoro M;Vivacqua A;Bonofiglio D;Mauro L;Aquila S;Tramontano D;Fuqua SA;Andò S
乳房接触雌激素和其他性激素是一个重要的癌症危险因素，雌激素受体下调剂引起了临床的广泛关注。表没食子儿茶素没食子酸酯 (EGCG) 是绿茶中的一种多酚化合物，因其抗肿瘤特性而受到广泛关注。在这里，我们的目的是研究 EGCG 调节 ER+ PR+ 乳腺癌细胞中 ERα 表达的分子机制。 Western blotting 分析、实时 PCR 和 ERα 基因启动子缺失片段的瞬时转染表明，EGCG 下调 ERα 蛋白、mRNA 和基因启动子活性，同时减少 ERα 基因组和非基因组信号。这些事件通过 p38MAPK/CK2 激活而发生，导致 PR-B 的 Hsp90 释放及其随后的核易位，如免疫荧光研究所证明的。 EMSA 和 ChIP 测定表明，经 EGCG 处理后，PR-B 被招募到 ERα 启动子上的半 PRE 位点。这伴随着含有 NCoR 和 HDAC1 的辅阻遏物复合物的形成，同时 RNA 聚合酶 II 被取代。这些事件主要是由 PR-B 同工型介导的，因为它们可以被 PR-B siRNA 消除。我们的数据为 EGCG 下调 ERα 的机制提供了证据，并解释了 EGCG 对测试的 ER+ PR+ 癌细胞增殖的抑制作用。我们建议 EGCG/PR-B 信号传导应进一步用于临床方法。
Exposure of the breast to estrogens and other sex hormones is an important cancer risk factor and estrogen receptor down-regulators are attracting significant clinical interest. Epigallocatechin gallate (EGCG), a polyphenolic compound found in green tea, has gained considerable attention for its antitumor properties. Here we aimed to investigate the molecular mechanisms through which EGCG regulates ERα expression in ER+ PR+ breast cancer cells. Western blotting analysis, real time PCR and transient transfections of deletion fragments of the ERα gene promoter show that EGCG down-regulates ERα protein, mRNA and gene promoter activity with a concomitant reduction of ERα genomic and non genomic signal. These events occur through p38MAPK/CK2 activation, causing the release from Hsp90 of PR-B and its consequent nuclear translocation as evidenced by immunofluorescence studies. EMSA and ChIP assay reveal that, upon EGCG treatment, PR-B is recruited at the half PRE site on ERα promoter. This is concomitant with the formation of a corepressor complex containing NCoR and HDAC1 while RNA polymerase II is displaced. The events are crucially mediated by PR-B isoform, since they are abrogated with PR-B siRNA. Our data provide evidence for a mechanism by which EGCG down-regulates ERα and explain the inhibitory action of EGCG on the proliferation of ER+ PR+ cancer cells tested. We suggest that the EGCG/PR-B signaling should be further exploited for clinical approach.