CARCINOGENICITY OF B RING UNSATURATED ESTROGENS

B环不饱和雌激素的致癌性

• 批准号: 6052012
• 负责人: DAVID C SPINK
• 金额: $ 19.15万
• 依托单位: WADSWORTH CENTER
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-01-07 至 2003-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6052012
• 关键词: DNA damage; adduct; breast neoplasms; catechols; cell line; chemical carcinogenesis; chemical conjugate; cytochrome P450; enzyme activity; estrogens; female; genetically modified animals; hormone related neoplasm /cancer; hormone therapy; laboratory mouse; longitudinal animal study; mammary epithelium; nonhuman therapy evaluation; steroid hormone metabolism; tissue /cell culture

The major concern regarding estrogen replacement therapy (ERT) is the significant increase in the risk of breast cancer that accompanies long-term use. The most commonly used formulation for ERT is Premarin, a preparation consisting largely of B-ring unsaturated estrogens including conjugated forms of equilin (Eq) and equilenin (Eqn). Our preliminary studies show Ah-receptor-regulated metabolism of Eqn to 4-hydroxylated metabolites in several human breast-derived cell lines expressing cytochrome P4501B1 (CYP1Bl). Semiquinones and quinones derived from these 4-hydroxy metabolites, which are adductive and lead to free radical production, may be involved in carcinogenesis. We hypothesize that estrogens are involved in both the initiation and promotion phases of carcinogenesis, and that aromaticity of the B-ring of steroidal estrogens increases carcinogenic potency. Our broad, long-term goal is to determine whether steroidal estrogens, including the B-ring unsaturated estrogens, Eq and Eqn, are carcinogenic through metabolic activation via catechol estrogens. 0ur Specific Aims are to: 1) Characterize Eq and Eqn metabolism in a series of immortalized tumor- and non-tumor-derived human breast-cell lines. Pathways of Eq and Eqn bioactivation involving hydrolysis of conjugates, reduction to 17beta-dihydro forms and hydroxyation to catechol estrogens will be investigated. 2) Determine the catechol synthetic activities of human cytochromes P450 of the CYP1, CYP2, and CYP3 families with Eq, Eqn, and their 17alpha- and 17beta-dihydro forms as substrates. 3) Establish transgenic mouse lines expressing human CYP1B1 in the mammary epithelium, 4) Determine the effects of treatment with Eq and Eqn on DNA damage and the incidence of mammary-gland tumors in human CYP1B1-transgenic mice. The studies described here will provide novel results regarding the metabolism of the B-ring unsaturated estrogens by human enzymes in breast epithelial cells, and may provide mechanistic data supporting a role of metabolic activation of Eq, Eqn, and endogenous in the initiation of carcinogenesis in the human breast.

关于雌激素替代疗法（ERT）的主要担忧是长期使用会显着增加患乳腺癌的风险。 最常用的 ERT 制剂是 Premarin，这是一种主要由 B 环不饱和雌激素组成的制剂，包括马烯雌酮 (Eq) 和马烯雌酮 (Eqn) 的缀合形式。 我们的初步研究表明，在表达细胞色素 P4501B1 (CYP1Bl) 的几种人乳腺来源的细胞系中，Ah 受体调节 Eqn 代谢为 4-羟基化代谢物。 源自这些 4-羟基代谢物的半醌和醌具有加合性并导致自由基产生，可能与致癌作用有关。 我们假设雌激素参与致癌作用的起始阶段和促进阶段，并且类固醇雌激素的 B 环的芳香性增加了致癌效力。我们广泛、长期的目标是确定类固醇雌激素（包括 B 环不饱和雌激素 Eq 和 Eqn）是否通过儿茶酚雌激素代谢激活而致癌。 0ur 具体目标是： 1) 表征一系列永生化肿瘤和非肿瘤来源的人乳腺细胞系中的 Eq 和 Eqn 代谢。 将研究 Eq 和 Eqn 生物活化途径，包括缀合物水解、还原为 17β-二氢形式以及羟基化为儿茶酚雌激素。 2) 以Eq、Eqn及其17α-和17β-二氢形式为底物，测定CYP1、CYP2和CYP3家族的人细胞色素P450的儿茶酚合成活性。 3) 建立在乳腺上皮中表达人 CYP1B1 的转基因小鼠系。 4) 确定 Eq 和 Eqn 治疗对人 CYP1B1 转基因小鼠 DNA 损伤和乳腺肿瘤发生率的影响。 这里描述的研究将提供有关乳腺上皮细胞中人类酶对 B 环不饱和雌激素代谢的新结果，并可能提供支持 Eq、Eqn 和内源性代谢激活在人类乳腺癌发生起始中的作用的机制数据。