Treeck Oliver, Weber Angela, Boester Michaela, Porz Simone, Frey Nicola, Diedrich Klaus, Ortmann Olaf
Department of Obstetrics and Gynecology, University of Regensburg, Regensburg, Germany.
Breast Cancer Res Treat. 2003 Jul;80(2):155-62. doi: 10.1023/A:1024502107690.
A crosstalk between cellular estrogen response and receptor tyrosine kinase signaling has been shown in a variety of estrogen receptor (ER)-positive cell lines. We intended to examine the presence of estrogenic growth factor effects in an ER alpha-negative breast cancer cell line. By means of reporter gene assays, we investigated the activation of estrogen response elements (EREs) by epidermal growth factor (EGF) in the estrogen-unresponsive cell line MDA-MB-231. Our results demonstrate the H-ras-dependent activation of EREs after EGF treatment in this estrogen-unresponsive cell line, an effect which was not observed in the ERalpha/beta-positive breast cancer cell line MCF-7. In MDA-MB-231 cells, the transcriptional activity of an ERE-containing promotor was enhanced dose dependently by all tested EGF concentrations. This effect could be blocked by co-treatment with the epidermal growth factor receptor (EGFR) inhibitors AG1478 and ZD1839, as well as by co-transfection with a vector coding for a dominant negative H-ras mutant, but not by co-treatment with the pure antiestrogen ICI182,780. Furthermore, expression of constitutively active H-ras was shown to be sufficient to activate EREs in MDA-MB-231 cells. Our results suggest alternative utilization of ERE-mediated gene regulation in an estradiol-unresponsive breast cancer cell line in response to an EGF stimulus. This mechanism was shown to be dependent on EGFR and H-ras activity, but independent of the presence of functional ERalpha.
细胞雌激素反应与受体酪氨酸激酶信号传导之间的相互作用已在多种雌激素受体（ER）阳性细胞系中得到证实。我们旨在检测雌激素非依赖性乳腺癌细胞系中雌激素生长因子效应的存在情况。通过报告基因检测，我们研究了表皮生长因子（EGF）在雌激素无反应性细胞系MDA-MB-231中对雌激素反应元件（ERE）的激活作用。我们的结果表明，在该雌激素无反应性细胞系中，EGF处理后ERE会发生H-ras依赖性激活，而在ERα/β阳性乳腺癌细胞系MCF-7中未观察到这种效应。在MDA-MB-231细胞中，所有测试的EGF浓度均剂量依赖性地增强了含ERE启动子的转录活性。这种效应可被表皮生长因子受体（EGFR）抑制剂AG1478和ZD1839共同处理阻断，也可被编码显性负性H-ras突变体的载体共转染阻断，但不能被纯抗雌激素ICI182,780共同处理阻断。此外，组成型活性H-ras的表达足以激活MDA-MB-231细胞中的ERE。我们的结果表明，在雌激素无反应性乳腺癌细胞系中，对EGF刺激的反应中ERE介导的基因调控存在替代利用方式。该机制被证明依赖于EGFR和H-ras活性，但不依赖于功能性ERα的存在。
