Developmental Exposure to Low-dose Bisphenol A and Human Prostate Cancer Suscepti

描述（由申请方提供）：先前在大鼠中进行的研究提供了证据，证明在环境相关剂量下短暂暴露于双酚A（BPA）会通过表观遗传修饰导致前列腺的发育重编程，从而增强日后的致癌易感性。虽然剂量-反应曲线，BPA的药代动力学和接触途径的啮齿动物模型的研究正在进行中，以验证这些发现，有一个当前和迫切需要研究BPA对人类前列腺的影响。国家毒理学计划2008年的报告概括地指出，“对实验室动物的研究只提供了有限的证据，证明对发育的不利影响，需要更多的研究来更好地了解它们对人类健康的影响”。为了满足这一需求，已经用人前列腺祖细胞开发了新的模型，该模型允许直接检查低剂量BPA暴露的影响，因为它们在体外和体内形成前列腺样结构。拟议研究的目标是确定在人类前列腺发育的早期阶段暴露于环境相关水平的BPA是否会增加以后生活中前列腺癌发生的易感性，并确定这种重编程事件的潜在机制。据推测，前列腺上皮祖细胞是BPA作用的早期腺体形成过程中的直接目标。此外，据预测，BPA诱导的重编程是通过改变的DNA甲基化和组蛋白修饰的组合介导的，所述改变的DNA甲基化和组蛋白修饰是可遗传的，因为祖细胞自我更新，在个体的整个寿命期间传递改变的表观基因组信息。因此，拟议的研究代表了一种新的范式，即人类前列腺癌可能在生命早期就开始开始，以应对表观遗传学改变祖细胞的不利环境影响。将利用一种创新的方法来测试这一假设，并使用两种模型系统直接检查BPA对人前列腺祖细胞的影响：1）与人原代前列腺上皮/基质细胞的3-D共培养系统，以在体外形成前列腺球，以及2）作为与大鼠尿生殖窦间充质移植到小鼠肾囊1-3个月的重组体，以在体内形成嵌合前列腺样组织。这些新方法将允许检查人类前列腺上皮细胞中的分化缺陷（目标1）和致癌作用（目标2）作为发育BPA暴露的函数。这些研究将通过使用人类基因启动子阵列和Solexa ChIP-seq分析进行的DNA甲基化模式和可遗传染色质修饰的全基因组研究提供信息（目的3）。利用综合生物信息学，预计将确定BPA重编程基因候选人，可能作为生物标志物的早期生活BPA暴露在人类流行病学研究。为了确定BPA重编程的候选基因与人前列腺癌的潜在相关性，将利用人前列腺癌的组织微阵列（TMA）来筛选作为疾病阶段、进展和种族的函数的候选基因的错误表达。从拟议的研究中获得的信息将对科学，医学和监管界产生重大影响：1）为BPA对人类的负面影响提供强有力的证据，2）建立发育重编程的机制框架，3）鉴定BPA重编程的候选基因用作生物标志物，4）确定BPA基因与人类前列腺癌的相关性，5）验证筛选其他内分泌干扰物的有用模型系统; 6）为研究BPA在其他器官系统和疾病中的作用奠定基础。 公共卫生相关性：在啮齿动物模型中，越来越多的证据表明，在人类通常发现的剂量水平下，短暂的早期生活暴露于双酚A（BPA）会导致前列腺的发育重编程，并增加日后患前列腺癌的易感性。本提案将使用新开发的具有人前列腺祖细胞的模型系统在人前列腺组织中测试这种可能性。鉴定表观遗传标记和BPA重编程基因可以作为发育BPA暴露的生物标志物，并提供对表观基因组可塑性的分子见解，该可塑性易患前列腺癌。这些发现将对医学和监管界具有很高的价值，并可作为人类暴露于具有致癌潜力的普遍环境内分泌干扰物的模型。

DESCRIPTION (provided by applicant): Previous studies in rats have provided evidence that brief, early-life exposures to bisphenol A (BPA) at environmentally relevant doses results in developmental reprogramming of the prostate gland via epigenetic modifications that enhance carcinogenic susceptibility later in life. While dose-response profiles, BPA pharmacokinetics and route of exposure studies in rodent models are underway to validate these findings, there is a current and compelling need for research on BPA effects in the developing human prostate gland. The National Toxicology Program 2008 report summarily stated that "studies in laboratory animals provide only limited evidence for adverse effects on development and more research is needed to better understand their implications for human health". In response to this need, novel models have been developed with human prostate progenitor cells that permit a direct examination of the impact of low-dose BPA exposures as they form prostate-like structures in vitro and in vivo. The goals of the proposed studies are to determine if exposure to environmentally relevant levels of BPA during the early stages of human prostate development increases susceptibility to prostate carcinogenesis later in life and to identify the underlying mechanism of this reprogramming event. It is hypothesized that prostate epithelial progenitor cells are the direct targets of BPA action during early gland formation. Further, it is predicted that BPA-induced reprogramming is mediated through a combination of altered DNA methylation and histone modifications that are heritable as progenitor cells self renew, transmitting altered epigenomic information throughout the lifespan of the individual. The proposed research thus represents a new paradigm that human prostate carcinogenesis may begin early in life in response to adverse environmental influences that epigenetically alter progenitor cells. An innovative approach will be exploited to test this hypothesis and directly examine BPA effects on human prostate progenitor cells using two model systems: 1) a 3-D co-culture system with human primary prostate epithelial/stromal cells to form prostaspheres in vitro, and 2) as recombinants with rat urogenital sinus mesenchyme grafted to murine kidney capsules for 1-3 months to form chimeric prostate-like tissues in vivo. These novel approaches will permit an examination of differentiation defects (Aim 1) and carcinogenesis (Aim 2) in the human prostate epithelial cells as a function of developmental BPA exposures. These studies will be informed by genome-wide studies of DNA methylation patterns and heritable chromatin modifications using human gene promoter arrays and Solexa ChIP-seq analysis (Aim 3). Using integrative bioinformatics, it is expected to identify BPA reprogrammed gene candidates that may serve as biomarkers for early-life BPA exposures in human epidemiology studies. To determine the potential relevance of BPA-reprogrammed candidate genes to human prostate cancer, tissue microarrays (TMAs) of human prostate cancer will be utilized to screen for misexpression of gene candidates as a function of disease stage, progression and ethnicity. The information gained from the proposed studies will be of high impact on the scientific, medical and regulatory communities in terms of 1) providing strong and compelling evidence for negative effects of BPA in humans, 2) establishing a mechanistic framework for developmental reprogramming, 3) identifying BPA-reprogrammed candidate genes for use as biomarkers, 4) ascertaining relevance of BPA-genes to human prostate cancer, 5) validating a useful model system for screening other endocrine disrupting chemicals, and 6) establishing a basis for studies on BPA in other organ systems and diseases. PUBLIC HEALTH RELEVANCE: There is increasing evidence in rodent models that brief, early-life exposures to bisphenol A (BPA) at dose levels typically found in humans results in developmental reprogramming of the prostate gland and increases susceptibility to prostate cancer later in life. The present proposal will test for this possibility in human prostate tissue using newly developed model systems with human prostate progenitor cells. Identification of epigenetic marks and BPA-reprogrammed genes may serve as biomarkers for developmental BPA exposures and provide molecular insight into the epigenomic plasticity that predisposes to prostate cancer with aging. The findings will be of high value to the medical and regulatory communities and serve as a model for human exposures to prevalent environmental endocrine disruptors with suspected carcinogenic potential.