Analysis of estrogen-induced genes in breast cancer

我们发现，雌激素增加了胆碱激酶的活性和蛋白水平在DMBA诱导的大鼠乳腺癌。胆碱激酶基因可能受雌激素或雌激素诱导因子的调控。为了研究该酶的激活机制，我们进行了两个实验。首先，我们分离并鉴定了大鼠胆碱激酶基因。胆碱激酶基因的5 '端不仅具有典型的管家基因的特征，而且还具有受多种调控因子调控的基因的特征。事实上，致癌物3-甲基胆蒽和肝毒性四氯化碳诱导了大鼠肝脏中的这种酶。然而，在该基因的5 '端和第一内含子的起始端之间，既没有发现雌激素反应元件，也没有发现与雌激素结合的类似序列。其次，我们从雌激素诱导的大鼠乳腺癌和人乳腺癌细胞系MCF-7裸鼠移植瘤中的mRNA中获得cDNA。在存在或不存在雌激素的情况下从这些肿瘤中提取总RNA。通过逆转录合成cDNA，并使用各种引物对进行聚合酶链反应。反应产物通过电泳分离并平行差异显示。我们从大鼠肿瘤中获得了13个雌激素诱导基因的cDNA，从MCF-7肿瘤中获得了39个。我们正在分析这些cDNA。我们将阐明胆碱激酶激活和生长调节雌激素的机制。

We found that estrogen increased the activity and protein levels of choline kinase in DMBA-induced rat mammary carcinoma. Choline kinase gene was expected to be regulated by estrogen or by factor induced by estrogen. To investigate the activation mechanism of the enzyme, we carried out two experiments. First, we isolated and characterized rat choline kinase gene. The 5'region of choline kinase gene showed features not only of a typical housekeeping gene but also of a gene regulated by a various kind of regulatory factors. In fact, the carcinogen 3-methylcholanthrene, and hepatotoxic carbon tetrachloride induced this enzyme in rat liver. However, neither estrogen responsive element norits similar sequence of the estrogen binds was found between 5'region and the beginning of the first intron of this gene. Second, we obtained cDNAs from mRNA induced by estrogen in DMBA-induced rat mammary carcinoma and in human breast cancer cell line MCF-7 implanted in nude mice. Total RNA was extracted from these tumors in the presence or absence of estrogen. cDNA was synthesized by reverse transcription and used to polymerase chain reaction with a various pair of primers. Reaction products were separated by electrophoresis and differentially displayd in parallel. We obtained 13 cDNAs of estrogen-induced genes from rat tumors and 39 cDNAs of these from MCF-7 tumors. We are analyzing these cDNAs. We will elucidate the mechanism of choline kinase activation and growth regulation by estrogen.