Gonadotropins & Cox-2 in Ovarian Cancer Prevention

描述(申请人提供)：流行病学观察已经确定了卵巢癌的危险因素，如围绝经期的高癌症发病率和口服避孕药的预防作用。然而，这些公认的想法的机制仍然不清楚，实验系统是非常可取的，以获得对流行病学结果的生物学和机械学理解。绝经期卵巢会发生形态变化，也就是所谓的“卵巢老化”，这与围绝经期和绝经后卵巢癌的高发病率有关。我们探索了一种生殖细胞缺陷的WV(白点变异)突变小鼠系，以模拟绝经生理对卵巢癌风险增加的影响，该模型还可能允许我们测试预防药物。WV小鼠在c-Kit中存在点突变，将酪氨酸激酶活性降低到约1-5%(不是零突变)。这种突变会导致卵巢生殖细胞和卵泡的过早丧失，但其他生物表型非常温和，小鼠的寿命接近正常。生殖细胞缺陷的WV小鼠概括了绝经后卵巢形态的一些变化，并发展为管状腺瘤。此外，加上p27kip1或p53缺失等致癌突变，可将卵巢腺瘤转化为肿瘤。在初步实验中，抑制COX-1被发现除了抑制肿瘤的发展外，还可以延缓卵泡的枯竭。在研究的几种蛋白水解酶中，我们发现uPA在WV卵巢中升高，我们推测uPA可能是WV卵巢肿瘤表型的潜在原因。该提案的目的是利用具有额外致癌基因突变的WV小鼠模型来研究绝经后卵巢癌风险增加的机制，并测试几种潜在的预防方法。首先，我们将进一步研究COX-1在卵巢生殖细胞、卵泡成熟和存活以及卵巢肿瘤发生发展中的作用(目标1)。我们还将利用WV小鼠模型研究uPA在卵巢肿瘤形成中的重要性，以及uPA抑制剂减少卵巢肿瘤形成的能力(目标2)。最后，我们将用孕激素抑制WV小鼠的促性腺激素，以验证“卵泡耗竭假说”。这些实验将揭示卵泡枯竭或促性腺激素增加是否是WV小鼠卵巢肿瘤发生的主要原因(目标3)。这些研究将探讨与生殖因素有关的卵巢癌病因学的基本机制，以及COX-1、COX-2、uPA和孕激素(口服避孕药)的作用和机制，这些都是卵巢癌潜在的预防靶点/制剂。这些实验的成功完成将进一步加深我们对生殖因素对卵巢癌风险的潜在机制的理解，并为卵巢癌可能的预防方法提供理论基础。 公共卫生相关性：在这项应用中，我们建议研究卵巢肿瘤发生中的生殖因素。进一步的研究将集中在COX-1和uPA，预防方法的潜在靶点以及阿司匹林、孕激素和WX-UK1(一种uPA抑制剂)的使用。这些研究将验证卵泡耗竭在卵巢肿瘤发生发展中的重要性，并为卵巢癌的病因学和肿瘤生物学提供新的认识。这一结果可能会使人们对预防卵巢癌的潜力以及孕酮/孕激素在避孕药和绝经后激素替代疗法中的作用机制有新的理解。此外，这些研究还将测试COX和uPA通路是否可以作为预防卵巢癌靶点的有用靶点，并提供对其机制的理解。

DESCRIPTION (provided by applicant): Epidemiological observations have established ovarian cancer risk factors, such as high cancer incidence in peri- postmenopausal ages and preventive activity of oral contraceptives. However, the mechanisms for these well-established ideas remain obscure, and experimental systems are highly desirable to gain biological and mechanistic understanding of the epidemiological findings. Menopausal ovaries undergo morphological changes, known as "ovarian aging" which are implicated in the high incidence of ovarian cancer occurring during the peri-menopausal and immediate post-menopausal periods. We explore a germ cell-deficient Wv (white spotting variant) mutant mouse line to model the impact of menopausal physiology on the increased risk of ovarian cancer, and the model may also allow us to test preventive agents. The Wv mice harbor a point mutation in c-Kit that reduces the tyrosine kinase activity to about 1-5% (not a null mutation). The mutation results in a premature loss of ovarian germ cells and follicles, but other biological phenotypes are very mild and the mice have a near normal life span. The germ cell- deficient Wv mice recapitulate some of these post-menopausal alterations in ovarian morphology and develop tubular adenomas. Furthermore, addition of oncogenic mutation such as loss of p27kip1 or loss of p53 converts the ovarian adenomas into neoplastic tumors. In preliminary experiments, suppression of Cox-1 was found to delay ovarian follicle depletion in addition to suppressing tumor development. Among several proteolytic enzymes investigated, we found that uPA was elevated in Wv ovaries, and we speculate that uPA may be the underlying cause of Wv ovarian tumor phenotype. The goal of the proposal is to use the Wv mouse models with additional oncogenic mutation to study the mechanisms responsible for the menopausal increase in ovarian cancer risk and to test several potential preventive approaches. First, we will further study the roles of Cox-1 in ovarian germ cell and follicle maturation and survival, and ovarian tumor development (Aim 1). We also will investigate the importance of uPA in ovarian tumor formation using the Wv mouse models, and the ability of uPA inhibitors to reduce ovarian tumorigenesis (Aim 2). Lastly, we will use progestin to suppress gonadotropins in Wv mice to verify the "follicle depletion hypothesis". The experiments will reveal whether follicle depletion or increased gonadotropins is the principal cause of ovarian tumorigenesis in Wv mice (Aim 3). These studies will address a fundamental mechanism of ovarian cancer etiology related to reproductive factors and the roles and mechanisms of Cox-1, Cox-2, uPA, and progestins (oral contraceptives), which are potential preventive targets/agents for ovarian cancer. Successful completion of the experiments will further our understanding of the underlying mechanism for reproductive factors on ovarian cancer risk and provide rationale for possible preventive approaches for ovarian cancer. PUBLIC HEALTH RELEVANCE: In this application, we propose to study reproductive factors in ovarian tumor development. Further studies are to focus on Cox-1 and uPA, potential targets for preventive approaches and the use of aspirin, progestins, and WX-UK1 (a uPA inhibitor). These studies will verify the importance of follicle depletion in the development of ovarian neoplasms and provide new understanding of the etiology and tumor biology of ovarian cancer. The results may generate new understanding for the potential to prevent ovarian cancer and the mechanisms of progesterone/progestins in contraceptives and in postmenopausal hormone replacement therapy. Also, the studies will test if Cox and uPA pathways may be useful as targets for prevention of ovarian cancer targets, and provide an understanding of their mechanisms.