P53-dependent responses to toxicants in parous and nulliparous breast

描述（由申请人提供）： 即使存在强有力的实验数据，乳腺癌与环境致癌物暴露之间的关联在流行病学文献中通常很弱或不一致。对环境致癌的最有力支持来自小鼠模型，该模型显示，电离辐射（IR）和多环芳烃（PAH）等暴露会增加乳腺肿瘤的形成。这些相同的实验模型表明，胎次具有 p53 介导的抗癌作用。本申请提出了一种比较毒理学方法，用于剖析导致乳腺癌环境致癌的生物途径，重点关注环境致癌物、p53 途径和胎次之间的相互作用。选择了三类环境暴露进行研究：IR、PAH 和有机氯 (OC)，每一类都有丰富的流行病学和毒理学文献。前两类（IR 和 PAH）都会引起 DNA 损伤并诱导 p53 依赖性 DNA 损伤反应，但 DNA 损伤机制不同。相比之下，OC 不会直接破坏 DNA，因此为 p53 依赖性信号传导提供阴性对照。 OC 还提供了 PAH 的比较，因为 PAH 和 OC 都可以激活芳基碳氢化合物受体 (AhR) 并扰乱乳房的内分泌作用。在目标 1 中，我们将使用同基因人类乳腺细胞系（表达或不表达 p53RNAi 来敲低 p53 表达）和未产的 Trp53 / 和 Trp53-/- 小鼠来评估每种毒物的 p53 依赖性效应。在目标 2 中，我们将检查人类（使用乳房缩小成形术样本）和小鼠中与胎次相关的基因表达谱，特别关注识别 p53 调节的基因表达。在目标 3 中，将通过比较经产小鼠和年龄匹配的未产小鼠对有毒物质的转录反应来评估胎次与环境致癌之间的相互作用。对毒物的不同反应将在未产妇和已产妇女的人类乳腺组织（乳房缩小成形术的多余组织）的外植体培养物中得到验证。因此，每个目标都将整合人类和小鼠的反应来定义对毒物和奇偶性的反应。来自所有三个目标的数据将被整合，以便对这些有毒物质的环境暴露、p53 信号传导和胎次状态如何相互作用以影响乳腺信号传导以及最终的致癌作用进行完整的多因素评估。这些研究将定义环境诱发乳腺癌的机制，以定义易感性的基因型-表型相关性为基础，并将确定可用于未来动物和人类研究的新的候选易感性生物标志物。

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.