The present study aims to discover the influences of tamoxifen and 17β-estradiol (E2) on tamoxifen-resistant (TamR) patients in vitro. Herein, we established a stabilized TamR MCF-7 cell line at 1 μM via gradient concentrations of tamoxifen cultivation. The expression changes of four ER subtypes (ERα66, ERβ, ERα36 and GPR30) were found to bring about tamoxifen resistance. Moreover, the generation of tamoxifen resistance involved in apoptosis escape via a reactive oxygen species-regulated p53 signaling pathway. Interestingly, E2 at environmental concentrations (0.1–10 nM) could activate the expression of both ERα36 and GPR30, and then stimulate the phosphorylation of ERK1/2 and Akt, resulting in cell growth promotion. Cell migration and invasion promotion, apoptosis inhibition, and cell cycle G1-S progression are involved in such proliferative effects. Conversely, the application of specific antagonists of ERα36 and GPR30 could restore tamoxifen's sensitivity as well as partially offset E2-mediated proliferation. In short, overexpression of ERα36 and GPR30 not only ablate tamoxifen responsiveness but also could promote tumor progression of TamR breast cancer under estrogen conditions. These results provided novel insights into underlying mechanisms of tamoxifen resistance and the negative effects of steroid estrogens at environmental concentrations on TamR MCF-7 cells, thus generating new thoughts for future management of ER-positive breast cancer.

中文翻译：

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低浓度 17β-雌二醇通过膜雌激素受体介导的信号通路加剧乳腺癌治疗中他莫昔芬的耐药性

本研究旨在体外发现他莫昔芬和 17β-雌二醇 (E2) 对他莫昔芬耐药 (TamR) 患者的影响。在此，我们通过梯度浓度的他莫昔芬培养建立了 1 μM 稳定的 TamR MCF-7 细胞系。发现四种ER亚型（ERα66、ERβ、ERα36和GPR30）的表达变化导致他莫昔芬耐药。此外，与细胞凋亡有关的他莫昔芬抗性的产生通过活性氧调节的 p53 信号通路逃逸。有趣的是，环境浓度（0.1-10 nM）的 E2 可以激活 ERα36 和 GPR30 的表达，然后刺激 ERK1/2 和 Akt 的磷酸化，从而促进细胞生长。促进细胞迁移和侵袭，抑制细胞凋亡，和细胞周期 G1-S 进程参与这种增殖作用。相反，ERα36 和 GPR30 的特异性拮抗剂的应用可以恢复他莫昔芬的敏感性并部分抵消 E2 介导的增殖。总之，ERα36和GPR30的过表达不仅可以消除他莫昔芬的反应，而且可以促进雌激素条件下TamR乳腺癌的肿瘤进展。这些结果为他莫昔芬耐药的潜在机制和环境浓度下类固醇雌激素对 TamR MCF-7 细胞的负面影响提供了新的见解，从而为未来治疗 ER 阳性乳腺癌提供了新思路。总之，ERα36和GPR30的过表达不仅可以消除他莫昔芬的反应，而且可以促进雌激素条件下TamR乳腺癌的肿瘤进展。这些结果为他莫昔芬耐药的潜在机制和环境浓度下类固醇雌激素对 TamR MCF-7 细胞的负面影响提供了新的见解，从而为未来治疗 ER 阳性乳腺癌提供了新思路。总之，ERα36和GPR30的过表达不仅可以消除他莫昔芬的反应，而且可以促进雌激素条件下TamR乳腺癌的肿瘤进展。这些结果为他莫昔芬耐药的潜在机制和环境浓度下类固醇雌激素对 TamR MCF-7 细胞的负面影响提供了新的见解，从而为未来治疗 ER 阳性乳腺癌提供了新思路。