Hormonal regulation of p53 activity in mammary tissue

描述（由申请人提供）：p53通路遗传缺陷的女性患乳腺癌的风险极高，这揭示了p53在乳腺癌易感性中的特殊重要性。我们的实验室已经证明乳腺上皮中p53肿瘤抑制蛋白的活性受激素调节。具体来说，在未生育小鼠的乳腺上皮中，p53活性受到损害，但对内分泌治疗有反应，已被证明可以使乳腺上皮抵抗癌变。初步数据表明，雌激素和孕激素（E+P）治疗是乳腺上皮中p53依赖的DNA损伤反应所必需的。我们认为，在乳腺发育的特定时期，由于p53活性受损，乳腺上皮容易发生癌变，但特定的内分泌刺激有助于激活p53功能并减轻这种风险。本提案中概述的实验将确定E+P治疗调节乳腺中p53功能的途径。目的1：通过确定启动级联反应的受体（目的1.1），E+P转导信号的转录靶标（目的1.2），以及作用于p53蛋白使其对DNA损伤诱导的应激信号作出反应的酶（目的1.3），将研究介导E+P对p53活性影响的途径。目的2：将使用携带p53状态不同的乳腺上皮移植小鼠（BALB/c-Trp53+/- vs BALB/c-Trp53-/-）来确定激素治疗是否通过p53依赖机制抑制乳腺肿瘤。目的3：在整个器官培养中，使用药物抑制剂和敲除小鼠的乳腺组织来检测E+ p依赖性p53激活所需的途径，以确定特定靶点。乳腺上皮细胞系将用于提供更高分辨率的分子机制分析。在初步数据的基础上，我们将重点介绍维甲酸代谢和tgf - β信号的作用。该结果将导致确定在乳腺上皮中调节p53功能的细胞机制。这些途径将为治疗和预防乳腺癌提供新的靶点。

DESCRIPTION (provided by applicant): The extreme risk of breast cancer among women bearing genetic deficiencies in the p53 pathway reveals the particular importance of p53 in breast cancer susceptibility. Our laboratory has demonstrated that the activity of the p53 tumor suppressor protein in the mammary epithelium is subject to hormonal regulation. Specifically, p53 activity is compromised in mammary epithelium of nulliparous mice, but is responsive to endocrine treatments that have been shown to render the mammary epithelium resistant to carcinogenesis. Preliminary data demonstrate that treatment with both estrogen and progesterone (E+P) are required for p53-dependent responses to DNA damage in the mammary epithelium. We propose that the mammary epithelium is rendered susceptible to carcinogenesis due to impaired p53 activity during specific periods of mammary gland development, but that specific endocrine stimuli serve to activate p53 function and mitigate this risk. The experiments outlined in this proposal will define the pathways by which treatment with E+P regulate p53 function in the mammary gland. Aim 1: The pathways that mediate the effects of E+P on p53 activity will be examined by determining the receptors that initiate the cascade (Aim 1.1), the transcriptional targets of E+P that transduce the signal (Aim 1.2), and the enzymes that act on p53 protein to render it responsive to DNA damage-induced stress signals (Aim 1.3). Aim 2: Mice bearing transplants of mammary epithelium that vary in p53 status (BALB/c-Trp53+/- vs BALB/c-Trp53-/-) will be used to determine whether hormonal treatments inhibit mammary tumors by p53-dependent mechanisms. Aim 3: The pathways necessary for E+P-dependent activation of p53 will be examined in whole organ cultures using drug inhibitors and mammary tissue from knockout mice to identify specific targets. Breast epithelial cell lines will be used to provide higher resolution analysis of the molecular mechanisms. Based on preliminary data, the effects of retinoic acid metabolism and TGF-beta signaling will be emphasized. The results will lead to identification of cellular mechanisms that regulate p53 function in the mammary epithelium. These pathways will provide novel targets for both treatment and prevention of breast cancer.