Breast tumor aromatase: functional role and transcriptional regulation
Breast tumor aromatase: functional role and transcriptional regulation
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DOI：
10.1677/erc.0.0060149
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发表时间：
1999-06-01
影响因子：
3.9
通讯作者：
Yang, C
中科院分区：
文献类型：
--
作者：
Chen, S;Zhou, D;Yang, C
通过酶活性测量、免疫细胞化学和RT-PCR分析，已证明芳香酶在人类乳腺癌组织中的表达水平高于正常乳腺组织。包括MCF-7乳腺癌细胞在内的细胞培养、使用芳香化酶转染的乳腺癌细胞的动物实验以及转基因小鼠研究已经证明，原位雌激素产生在乳腺肿瘤促进中比循环雌激素发挥更重要的作用。此外，肿瘤芳香化酶被认为能够通过自分泌和旁分泌途径刺激乳腺癌生长，如三维细胞培养研究所证明的。RT-PCR和基因转录研究表明，芳香化酶启动子从糖皮质激素刺激的启动子，1.4，在正常组织中cAMP刺激的启动子，1.3和II，在癌组织中切换。最近，我们通过DNA缺失和突变分析鉴定并表征了启动子1.3上游的cAMP反应元件（CREaro）。我们的启动子功能分析结果也证明了CREaro和沉默元件（S1）之间的相互作用，这是以前在我们的实验室中确定的。在cAMP存在下，正调控CREaro可以克服沉默子对启动子1.3功能的作用。从我们自己和其他实验室产生的结果的基础上，我们提出，在正常的乳腺脂肪基质细胞和成纤维细胞，芳香化酶的表达是由启动子1.4（糖皮质激素依赖），和启动子1.3和II的行动被抑制的沉默负调控元件。然而，在癌细胞和周围的脂肪基质细胞中，cAMP水平增加，芳香化酶启动子转换为cAMP依赖性启动子-1.3和II。此外，我们应用酵母单杂交筛选方法来寻找与沉默元件S1相互作用的蛋白质。鉴定的主要蛋白质是ERR α-1;然而，存在于卵巢中的SF-1在乳腺癌组织中未检测到。使用带有芳香酶基因组片段的报告质粒，该片段含有启动子1.3和S1，在乳腺癌SK-BR-3细胞中，发现ERR α-1具有正调节功能。据信，由于转录因子的不同表达模式，人芳香化酶基因中的沉默元件在不同组织中可能具有不同的功能。
Aromatase has been shown to be expressed at a higher level in human breast cancer tissue than in normal breast tissue, by means of enzyme activity measurement, immunocytochemistry, and RT-PCR analysis. Cell culture including MCF-7 breast cancer cells, animal experiments using aromatase-transfected breast cancer cells, and transgenic mouse studies have demonstrated that estrogen production in situ plays a more important role than circulating estrogens in breast tumor promotion. In addition, tumor aromatase is believed to be able to stimulate breast cancer growth through both autocrine and paracrine pathways, as demonstrated by a three-dimensional cell culture study. RT-PCR and gene transcriptional studies have revealed that the aromatase promoter is switched from a glucocorticoid-stimulated promoter, 1.4, in normal tissue to cAMP-stimulated promoters, 1.3 and II, in cancerous tissue. Recently, we identified and characterized a cAMP-responsive element (CREaro) upstream from promoter 1.3 by DNA deletion and mutational analyses. Our results from promoter functional analysis also demonstrated an interaction between the CREaro and the silencer element (S1) that was identified previously in our laboratory. In the presence of cAMP, the positive regulatory CREaro can overcome the action of the silencer on the function of promoter 1.3. On the basis of results generated from our own and other laboratories, we propose that, in normal breast adipose stromal cells and fibroblasts, aromatase expression is driven by promoter 1.4 (glucocorticoid dependent), and that the action of promoters 1.3 and II is suppressed by the silencer negative regulatory element. However, in cancer cells and surrounding adipose stromal cells, the cAMP level increases, and aromatase promoters are switched to cAMP-dependent promoters - 1.3 and II. Furthermore, we applied the yeast one-hybrid screening method to search for proteins interacting with the silencer element, S1. The major protein identified was ERR alpha-1; however, SF-1, which is present in the ovary, is not detected in breast cancer tissue. Using a reporter plasmid with the aromatase genomic fragment containing promoter 1.3 and S1, in breast cancer SK-BR-3 cells, ERR alpha-1 was found to have a positive regulatory function. It is believed that the silencer element in the human aromatase gene may function differently in different tissues, as a result of distinct expression patterns of transcription factors.