Progesterone Signaling and Blockade in Human Breast Tumorigenesis and Prevention

 说明(申请人提供)：终生孕酮(P4)暴露是乳腺癌风险的重要因素，这反映在与终生排卵周期数相关的风险、黄体期P4峰值伴随的乳房上皮细胞增殖增加，以及外源性孕激素使用者较高的乳腺癌风险。此外，使用孕激素的肿瘤似乎更具侵袭性。这一临床和流行病学证据表明，黄体酮阻断是预防乳腺癌的一种很好的候选策略。新一代选择性孕激素受体调节剂(SPRM)现已问世；其中之一(醋酸替拉普司酮，TPA)可抑制P4驱动的乳腺癌细胞增殖，并减弱P4驱动的致癌剂治疗大鼠的肿瘤生长。我们已经确定了一组与乳腺癌细胞增殖相关的新基因 被TPA有效抑制的孕激素R5020。基于这些数据以及其他人的发现，我们假设P4促进促增殖和肿瘤允许的表型，支持乳腺癌的发展，通过SPRM抑制这种表型将显著降低乳腺癌的风险。SPRM对乳腺癌的潜在保护作用和机制尚不清楚。我们建议定义SPRM在分子水平上拮抗PR的机制，以及辅助激活因子和辅助抑制因子的作用。此外，将确定SPRM在对抗P4增殖反应方面的有效性，以指导SPRM治疗患者的选择。在目标1中，我们将确定SPRM调节乳腺细胞PR活性的机制。我们将研究SPRM影响与PR结合的能力；我们将进行CHIP-SEQ以确定SPRM如何影响PR在全球范围内向基因组的招募，并将评估核受体辅阻遏子NCoR和SMRT以及其他转录辅助因子的参与。在目标2中，我们将确定SPRM是否抑制P4介导的肿瘤允许表型；我们定义了一个与P4驱动的增殖相关的16基因小组。我们将在体外，在人类乳腺器官中测试这一点，以确定SPRM是否抑制这些签名基因的表达。我们还将研究SPRM抑制与P4接触相关的乳腺干细胞扩张的能力，以及携带BRCA1突变的肿瘤的增殖和生长。在目标3中，我们将评估P4反应基因在人类临床样本中的表达，a)在高孕酮环境和低环境孕酮环境中，以及b)醋酸替拉普司酮治疗后。这些实验将1)确定SPRM在PR信号活跃的细胞和组织中的作用模式；2)将抑制乳房细胞增殖和干细胞扩张与特定的遗传途径联系起来；3)展示这些标记在人类乳房样本中的用途。这些结果将极大地推动乳腺癌预防领域向新的方向发展，提供新的有效药物，特别是对绝经前妇女。

 DESCRIPTION (provided by applicant): Lifetime progesterone (P4) exposure is an important contributor to breast cancer risk, as reflected in the risk associated with the lifetime number of ovulatory cycles, increased breast epithelial proliferation accompanying the P4 peak in the luteal phase, and the higher breast cancer risk of exogenous progestin users. Moreover, the tumors seen with progestin use appear to be more aggressive. This clinical and epidemiological evidence points to progesterone blockade as an excellent candidate strategy for breast cancer prevention. A new generation of selective progesterone receptor modulators (SPRMs) is now available; one of these (telapristone acetate, TPA) inhibits P4-driven proliferation of breast cancer cells, and attenuates P4-driven tumor growth in carcinogen treated rats. We have identified a novel set of genes associated with proliferation of breast cancer cells in response to the progestin, R5020 that are effectively suppressed by TPA. Based on these data as well as findings from others, we hypothesize that P4 promotes a pro-proliferative and tumor permissive phenotype which supports breast cancer development, suppression of which by SPRMs will significantly decrease breast cancer risk. The breast-specific effects and mechanisms for potential breast cancer protection of SPRMs are unknown. We propose to define the mechanisms by which SPRMs antagonize PR at the molecular level, and the role of coactivators and corepressors. In addition, the efficacy of SPRMs in antagonizing the proliferative response to P4 will be determined, to guide selection of patients for SPRM therapy. In Aim 1, we will determine the mechanisms by which SPRMs regulate PR activity in breast cells. The ability of SPRMs to affect binding to the PR will be studied; we will perform ChIP-Seq to determine how SPRMs affect PR recruitment to the genome in a global manner, and the involvement of the nuclear receptor corepressors, NCOR and SMRT as well as other transcription cofactors will be assessed. In Aim 2, we will determine if SPRMs inhibit the P4-mediated tumor permissive phenotype; we have defined a 16 gene panel, which is associated with P4 driven proliferation. We will test this in vitro, in human mammary organoids, to determine whether SPRMs inhibit expression of these signature genes. We will also study the ability of SPRMs to inhibit mammary stem cell expansion associated with P4 exposure, and the proliferation and growth of tumors that carry BRCA1 mutations. In Aim 3, we will evaluate the expression P4-response genes in human clinical samples, a) in high and low ambient progesterone environments and b) following treatment with telapristone acetate. These experiments will 1) define modes of actions of SPRMs in cells and tissues where PR signaling is active, 2) relate inhibition of proliferation of breast cells, and of stem cell expansion, to speciic genetic pathways; and 3) demonstrate utility of these markers in human breast samples. These results will significantly advance the field of breast cancer prevention in novel directions, providing both new, effective agents, particularly for premenopausal women.