AROMATASE IN ADIPOSE--RELATIONSHIP TO AGING AND CANCER

在人类体内，雌激素在许多组织部位合成。 包括卵巢颗粒细胞和黄体、胎盘 合体滋养层细胞，脑内各种部位，以及脂肪 组织。脂肪组织中雌激素的生物合成不仅随着 肥胖也与年龄有关。它的生理意义尚不清楚，但 从病理生理学的角度来看，它与许多 人类疾病，特别是子宫内膜癌和乳腺癌。为了 我们克隆并研究了雌激素生物合成的调控 编码人芳香酶细胞色素P450基因的特征 (P450arom)，负责雌激素生物合成的酶。我们有 发现这个基因的长度超过70kb，并且它的组织特异性 通过使用替代启动子来调节表达。在卵巢里 表达受翻译起始附近的启动子的调控 位点(启动子II)。在胎盘中，表达受启动子的调节 从翻译开始(启动子)的上游至少40kb I.L.)。在原位脂肪组织中，表达受三分之一的调控 启动子(1.4)，其在基因中的位置尚未确定。 出乎意料的是，当人类脂肪基质细胞被放置在培养中时， 启动子的选择似乎由培养条件决定， 即有无cAMP、地塞米松和生长因子。 为了研究分子和细胞机制， 这一新的基因表达调控，我们建议表征 调控元件存在于每个基因上游的区域 推动脂肪基质细胞表达的启动子，以及 SITE。与这些基因组相互作用的转录因子 调节元件的特征及其在荷尔蒙和 定义了特定于组织的调节。特别是，我们希望确定 生长因子在细胞培养中转换启动子使用的作用。 我们还将寻求确定转录激活或 抑制本身就足以决定启动子用途的改变 或者是否需要额外的机制，例如监管 决定优先就业的备选拼接因素 特定的5‘-剪接位点。最后，我们将确定相对的 这些不同的因素和机制在生理学中的重要性 调节脂肪组织中雌激素的生物合成，例如， 作为年龄的函数而出现的增长，以及随年龄的变化 区域脂肪分布。特别是，我们将解决这样一个概念： 乳腺肿瘤的发展受地区分布的影响 乳腺局部雌激素的生物合成及其机制 由此建立了P450arom表达的这种梯度 将对维修者进行调查。我们相信，这些研究将 为哺乳动物基因表达的调控提供了新的见解 以及特别是P450arom的表达，但特别是 将有助于揭示涉及雌激素的年龄相关过程 脂肪组织中的生物合成，即作为一种 衰老的作用及脂肪组织雌激素的意义 癌症发展过程中的生物合成。

In the human, estrogens are synthesized in a number of tissue sites including ovarian granulosa cells and corpus luteum, placental syncytiotrophoblast, various sites in the brain, as well as adipose tissue. Estrogen biosynthesis in adipose tissue increases not only with obesity but also with age. Its physiological significance is unclear, but from a pathophysiological standpoint it has been implicated in a number of human diseases, notably endometrial cancer and breast cancer. In order to study the regulation of estrogen biosynthesis we have cloned and characterized the gene encoding human aromatase cytochrome P450 (P450arom), the enzyme responsible for estrogen biosynthesis. We have found that this gene exceeds 70 kb in length and that its tissue-specific expression is regulated by the use of alternative promoters. In the ovary expression is regulated by a promoter proximal to the translational start site (promoter II). In the placenta, expression is regulated by a promoter which is at least 40 kb upstream from the start of translation (promoter I.l). In adipose tissue in situ, expression is regulated by a third promoter (1.4) whose position within the gene has yet to be ascertained. Unexpectedly, when human adipose stromal cells are placed in culture, promoter selection appears to be dictated by the culture conditions, namely the presence or absence of cAMP, dexamethasone and growth factors. In order to study the molecular and cellular mechanisms responsible for this novel regulation of gene expression, we propose to characterize the regulatory elements present in regions of the gene upstream of each of the promoters which drive expression in adipose stromal cells, as well as in situ. The transcription factors which interact with these genomic regulatory elements will be characterized and their role in hormonal and tissue-specific regulation defined. In particular, we wish to determine the role of growth factors in switching promoter use in cells in culture. We will also seek to establish whether transcriptional activation or inhibition per se is sufficient to determine the switching of promoter use or whether additional mechanisms are required, such as the regulation of alternative splicing factors which determine the preferential employment of specific 5'-splice sites. Lastly, we will determine the relative importance of these various factors and mechanisms in the physiological regulation of estrogen biosynthesis in adipose tissue, for example, the increase which occurs as a function of aging, and the variation with regional fat distribution. In particular we will address the concept that breast tumor development is influenced by the regional distribution of estrogen biosynthesis in local areas of the breast, and the mechanisms whereby such gradients of P450arom expression are established and maintained will be investigated. We believe that these studies will provide new insights into the regulation of mammalian gene expression in general as well as of P450arom expression in particular, but especially will throw light on age-dependent processes involving estrogen biosynthesis in adipose tissue, namely the increase that occurs as a function of aging, as well as the implication of adipose tissue estrogen biosynthesis in the development of cancer.