P53-dependent responses to toxicants in parous and nulliparous breast

描述(由申请人提供)： 在流行病学文献中，乳腺癌和暴露于环境致癌物之间的联系往往很弱或不一致，即使存在强有力的实验数据也是如此。对环境致癌最有力的支持来自小鼠模型，该模型表明，暴露于电离辐射(IR)和多环芳烃(PAHs)等环境中会增加乳腺癌的形成。这些相同的实验模型表明，产次具有P53介导的预防癌变的保护作用。本申请提出了一种比较毒理学方法，用于解剖导致环境致癌的生物途径，重点是环境致癌物质、P53途径和产次之间的相互作用。选择了三类环境暴露进行研究，每一类都有很强的流行病学和毒理学文献：IR、多环芳烃和有机氯(OCS)。前两类(IR和PAHs)均可引起DNA损伤，并诱导依赖于P53的DNA损伤反应，但DNA损伤机制不同。相比之下，OCS并不直接破坏DNA，因此对P53依赖的信号转导提供了负面控制。OCS还提供了PAHs的比较，因为PAHs和OCS都可以激活乳房中的芳香烃受体(AhR)并扰乱内分泌作用。在目标1中，我们将使用相同基因的人乳腺细胞系(有和没有表达p53RNAi来下调P53的表达)和未分娩的TrP53/和TrP53-/-小鼠来评估每种毒物对P53的依赖效应。在目标2中，我们将研究人类(使用缩乳术样本)和小鼠中与生育相关的基因表达谱，特别关注识别P53调节的基因表达。在目标3中，将通过比较产后和年龄匹配的未分娩小鼠对毒物的转录反应来评估产次和环境致癌之间的相互作用。对毒物的不同反应将在来自未分娩和临产妇女(缩乳术的多余组织)的人乳腺组织的外植体培养中得到验证。因此，每个目标都将整合人类和老鼠的反应，以确定对毒物和胎次的反应。来自所有三个AIMS的数据将被整合，以允许对环境暴露于这些毒物、p53信号和产次状态如何相互作用影响乳房信号，并最终导致癌症进行全面、多因素的评估。这些研究将确定环境诱发乳腺癌的机制，以定义易感性的基因-表型相关性为基础，并将确定新的候选易感性生物标记物，可用于未来的动物和人类研究。

DESCRIPTION (provided by applicant): Associations between breast cancer and exposure to environmental carcinogens are often weak or inconsistent in the epidemiologic literature, even when strong experimental data exists. The strongest support for environmental carcinogenesis comes from mouse models showing that exposures such as ionizing radiation (IR) and polycyclic aromatic hydrocarbons (PAHs) increase mammary tumor formation. These same experimental models have shown that parity has a p53-mediated, protective effect against carcinogenesis. This application proposes a comparative toxicology approach for dissecting the biological pathways that lead to environmental carcinogenesis of the breast, with emphasis on interactions between environmental carcinogens, the p53 pathway, and parity. Three classes of environmental exposure, each with a strong epidemiologic and toxicological literature, have been selected for study: IR, PAHs, and organochlorines (OCs). The first two classes (IR and PAHs) both cause DNA damage and induce p53-dependent DNA damage responses, but the DNA damage mechanisms are different. In contrast, OCs do not act by directly damaging DNA, and thus, provide a negative control for p53-dependent signaling. OCs also provide a comparison for the PAHs as both PAHs and OCs can activate the aryl hydrocarbon receptor (AhR) and perturb endocrine action in the breast. In Aim 1, we will assess the p53 dependent effects of each toxicant using isogenic human breast cell lines (with and without expression of p53RNAi to knockdown p53 expression) and nulliparous Trp53+/+ and Trp53-/- mice. In Aim 2, we will examine gene expression profiles associated with parity in humans (using reduction mammoplasty samples) and mice, with specific attention to identifying p53-regulated gene expression. In Aim 3, the interaction between parity and environmental carcinogenesis will be assessed by comparing transcriptional responses to toxicants in parous and age-matched nulliparous mice. Differential responses to toxicants will be verified in explant cultures of human breast tissue from nulliparous and parous women (excess tissue from reduction mammoplasty). Thus, each aim will integrate human and mouse responses to define responses to toxicants and parity. The data from all three aims will be integrated to allow a complete, multifactorial evaluation of how environmental exposures to these toxicants, p53 signaling, and parity status interact to affect breast signaling, and ultimately carcinogenesis. These studies will define the mechanisms of environmentally-induced breast cancer, anchored on genotype-phenotype correlations that define susceptibility, and will identify new candidate biomarkers of susceptibility that can be used in future animal and human studies.