Department of Pathology, University of Nevada School of Medicine, Reno, NV 89557-0350, USA.
Oncogene. 2010 Mar 11;29(10):1451-62. doi: 10.1038/onc.2009.433. Epub 2010 Jan 18.
The ERalpha signaling pathway is one of the most important and most studied pathways in human breast cancer, yet numerous questions still exist such as how hormonally responsive cancers progress to a more aggressive and hormonally independent phenotype. We have noted that human breast cancers exhibit a strong direct correlation between ERalpha and E-cadherin expression by immunohistochemistry, suggesting that ERalpha signaling might regulate E-cadherin and implying that this regulation might influence epithelial-mesenchymal transition (EMT) and tumor progression. To investigate this hypothesis and the mechanisms behind it, we studied the effects of ERalpha signaling in ERalpha-transfected ERalpha-negative breast carcinoma cell lines, the MDA-MB-468 and the MDA-MB-231 and the effects of ERalpha knockdown in naturally expressing ERalpha-positive lines, MCF-7 and T47D. When ERalpha was overexpressed in the ERalpha-negative lines, 17beta-estradiol (E2) decreased slug and increased E-cadherin. Clones maximally exhibiting these changes grew more in clumps and became less invasive in Matrigel. When ERalpha was knocked down in the ERalpha-positive lines, slug increased, E-cadherin decreased, cells became spindly and exhibited increased Matrigel invasion. ERalpha signaling decreased slug expression by two different mechanisms: directly, by repression of slug transcription by the formation of a corepressor complex of ligand-activated ERalpha, HDAC inhibitor (HDAC1), and nuclear receptor corepressor (N-CoR) that bound the slug promoter in three half-site estrogen response elements (EREs); indirectly by phosphorylation and inactivation of GSK-3beta through phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt). The GSK-3beta inactivation, in turn, repressed slug expression and increased E-cadherin. In human breast cancer cases, there was a strong inverse correlation between slug and ERalpha and E-cadherin immunoreactivity. Our findings indicate that ERalpha signaling through slug regulates E-cadherin and EMT.
雌激素受体α（ERα）信号通路是人类乳腺癌中最重要和研究最多的通路之一，但仍存在许多问题，例如激素反应性癌症如何发展为更具侵袭性和激素独立性的表型。我们注意到，通过免疫组织化学检测，人类乳腺癌表现出 ERα 与 E-钙黏蛋白表达之间的强烈直接相关性，表明 ERα 信号可能调节 E-钙黏蛋白，并暗示这种调节可能影响上皮-间充质转化（EMT）和肿瘤进展。为了研究这一假说及其背后的机制，我们研究了 ERα 信号在 ERα 转染的 ERα 阴性乳腺癌细胞系 MDA-MB-468 和 MDA-MB-231 中的作用，以及在天然表达 ERα 的 MCF-7 和 T47D 细胞系中 ERα 敲低的作用。当 ERα 在 ERα 阴性细胞系中过表达时，17β-雌二醇（E2）降低了 slug 的表达，增加了 E-钙黏蛋白的表达。最大程度表现出这些变化的克隆在基质胶中形成的团块中生长得更多，侵袭性降低。当 ERα 在 ERα 阳性细胞系中被敲低时，slug 表达增加，E-钙黏蛋白表达减少，细胞变得细长，并表现出基质胶侵袭性增加。ERα 信号通过两种不同的机制降低 slug 的表达：直接通过配体激活的 ERα、组蛋白去乙酰化酶抑制剂（HDAC1）和核受体共抑制因子（N-CoR）形成核心抑制复合物，结合 slug 启动子上的三个半位点雌激素反应元件（EREs），抑制 slug 转录；间接通过磷酸化和失活 GSK-3β，通过磷酸肌醇 3-激酶（PI3K）/蛋白激酶 B（Akt）。GSK-3β 的失活反过来又抑制 slug 的表达并增加 E-钙黏蛋白的表达。在人类乳腺癌病例中，slug 与 ERα 和 E-钙黏蛋白免疫反应性之间存在强烈的负相关。我们的研究结果表明，ERα 通过 slug 信号调节 E-钙黏蛋白和 EMT。
