Carcinogenic Metabolites formed from Antiestrogens

描述（由申请人提供）：他莫昔芬仍然是激素依赖性乳腺癌所有阶段治疗的内分泌治疗选择。此外，临床试验正在进行中，以确定他莫昔芬作为一种化学预防剂对乳腺癌高风险妇女的潜力。然而，一些研究提出了对这种药物长期治疗安全性的担忧。替代serm可能没有遗传毒性，因为不同的代谢途径可能导致最终致癌物的数量和/或类型减少。这个项目的中心假设是，对于某些抗雌激素，类醌的形成是致癌和细胞毒性的重要机制。例如，他莫昔芬可代谢为三种醌类，包括两种醌类和一种邻醌类。提出了以下具体目标：类黄酮在抗雌激素的致癌和细胞毒性作用中的作用。我们计划在细胞系中检测由serm形成的类醌的致癌潜力。我们将在雌激素受体阳性或阴性的人乳腺癌和子宫内膜癌细胞系中研究抗雌激素类药物的生化作用。2. 研究醌类化合物结构对亲电性和/或氧化还原性的影响。将测量SERM类醌与水和谷胱甘肽的反应速率。选定的具有雌激素或抗雌激素活性的中间体与脱氧核苷和DNA的反应也将被研究并阐明加合物结构。氧化还原活性代谢物将通过监测还原辅因子浓度的变化，确定活性氧的形成，并检查DNA的氧化损伤来测试。3. 确定抗雌激素代谢物的拮抗剂/激动剂活性是否与细胞系DNA损伤程度相关。我们预测，与雌激素受体的过度结合，然后转移到细胞核，将与DNA损伤的增加有关。石川细胞系统将用于确定SERM代谢物的雌激素或抗雌激素作用。石川细胞实验的结果将与测量抗雌激素代谢物与雌激素受体结合的研究进行比较。雌激素受体阳性和阴性细胞系经试验化合物处理后分离细胞DNA。DNA将被水解成脱氧核苷，并检查DNA是否受损。最后，我们将利用大鼠肝脏模型确定最具致癌性/细胞毒性的抗雌激素代谢物在体内诱导的DNA损伤程度。这些研究将阐明烷基化和自由基形成对每种抗雌激素的相对重要性，从而使反应性与结构的相关性成为可能，从而揭示影响细胞中抗雌激素反应性代谢物行为的一般原理。

DESCRIPTION (provided by applicant): Tamoxifen remains the endocrine therapy of choice in the treatment of all stages of hormone-dependent breast cancer. In addition, clinical trials are in progress to determine the potential of tamoxifen to act as a chemopreventive agent in women considered at high risk for developing breast cancer. However, several studies have raised concern over the safety of chronic treatment with this drug. Alternative SERMs may not be genotoxic because of different routes of metabolism that could lead to a decrease in amount and/or type of ultimate carcinogen(s). The central hypothesis of this project is that the formation of quinoids is an important mechanism of carcinogenesis and or cytotoxicity, for certain antiestrogens. For example, tamoxifen can be metabolized to three quinoids including two quinone methides and one o-quinone. The following specific aims are proposed: 1. Role of quinoids in the carcinogenic and cytotoxic effects of antiestrogens. We plan to examine the carcinogenic potential of quinoids formed from SERMs in cell lines. The biochemical effects of the antiestrogen quinoids will be investigated in human breast and endometrial cancer cell lines, which are either estrogen receptor positive or negative. 2. Investigate the effect of quinoids structure on electrophilic and/or redox reactivity. The rates of reaction of the SERM quinoids with water and GSH will be measured. Reactions of selected intermediates with either estrogenic or antiestrogenic activity with deoxynucleosides and DNA will also be investigated and adduct structures elucidated. Redox active metabolites will be tested by monitoring changes in the concentrations of reduced cofactors, determining the formation of reactive oxygen species, and examining oxidative damage to DNA. 3. Determine if the antagonist/agonist activity of antiestrogen metabolites correlates with the extent of DNA damage in cell lines. We predict that excessive binding to the estrogen receptor, which then translocates to the nucleus, will be correlated with an increase in DNA damage. The Ishikawa cell system will be used to determine the estrogenic or antiestrogenic effect of the SERM metabolites. The results from the Ishikawa cell experiments will be compared to studies measuring binding of the antiestrogen metabolites to the estrogen receptors. Cellular DNA from estrogen receptor positive and negative cells lines will be isolated after treatment with the test compound. The DNA will be hydrolyzed to deoxynucleosides and examined for DNA damage. Finally, we will determine the extent of DNA damage induced in vivo by the most carcinogenic/cytotoxic antiestrogen metabolites using the rat liver model. These studies will elucidate the relative importance of alkylation and free radical formation for each antiestrogen, thereby enabling correlations of reactivity with structure from which general principles influencing the behavior of antiestrogen reactive metabolites in cells will emerge.