Prenatal xenoestrogen exposure and mammary cancer

产前异雌激素暴露与乳腺癌

• 批准号: 6868360
• 负责人: ANA SOTO
• 金额: $ 24.53万
• 依托单位: TUFTS UNIVERSITY BOSTON
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-03 至 2006-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6868360
• 关键词: breast neoplasms; cancer risk; embryo /fetus; environmental exposure; estrogen analog; estrogen receptors; estrogens; gene expression; hormone regulation /control mechanism; hormone related neoplasm /cancer; in situ hybridization; laboratory rat; laser capture microdissection; longitudinal animal study; microarray technology; nucleic acid amplification techniques; nucleic acid hybridization; polymerase chain reaction

DESCRIPTION (provided by applicant): Increased breast cancer incidence has prompted scientists to consider the possible role of hormonally active environmental chemicals. However, epidemiological studies searching for correlations between adult environmental exposures and breast cancer incidence have been mainly inconclusive. Yet, epidemiological studies do suggest that fetal estrogen level fluctuations have long-term consequences on the risk of developing breast cancer as an adult. Studies in mice reveal that prenatal exposure to low doses of the xenoestrogen bisphenol A (BPA) alters the development of these mammary glands. These effects manifested long after exposure ceased. The increased number of terminal end buds and terminal ducts in these mammary glands is particularly relevant since carcinomas originate in these structures. We hypothesize that prenatal exposure to low doses of BPA may increase the risk of mammary cancer and that the mechanism responsible for the neoplastic outcome may include the extemporaneous expression of genes that mediate mammary gland development. Xenoestrogens administered prenatally may alter the expression of estrogen-responsive genes that would then affect downstream genes in the mammary development program and predispose these animals to cancer. To test this hypothesis we will use a rat model whereby exposure to the carcinogen nitroso-methyl-urea (NMU) at puberty induces mammary cancer. A pilot study performed using Wistar rats showed that this model could be modified to assess the effect of fetal exposure to environmentally relevant xenoestrogen levels. It produced data consistent with the proposed hypothesis. Aim 1: To determine the levels at which prenatal BPA exposure results in an increased incidence of mammary cancer. Tumor incidence and latency will be measured in Wistar rats exposed to BPA from gestational day 9 to birth. At 50 days of age, animals will be injected with a sub-carcinogenic dose of NMU. Aim 2: To test the hypothesis that prenatal BPA exposure alters gene expression in the mammary gland during both the period of BPA exposure and throughout life. Total RNA will be isolated from mammary glands and analyzed by DNA microarray technology. Where appropriate, laser-capture microdissection and/or RNA linear amplification techniques will also be used to obtain samples. Up- and down-regulated genes will be confirmed by QRTPCR. Cellular distribution will be assessed by in situ hybridization. Developmental points to be analyzed are: 1) during gestational BPA exposure; 2) 5 days postnatal; 3) peripubertal; and 4) after ductal development is completed. Aim 3: To test the hypothesis that in utero exposure to BPA alters the histoarchitecture of the rat mammary gland and results in the expression of pre-neoplastic phenotypes. This Aim will assess whether exposure to low doses of BPA results in specific morphological alterations in the rat mammary gland that may confer a propensity to carcinogenesis, such as an increase in the number of terminal end buds (TEBs) and terminal ducts (TDs) at the time of NMU administration), the persistence of TEBs beyond puberty, and the appearance of pre-neoplastic lesions at several age points. In addition, the histoarchitecture of the mammary gland at the time-points studied in Aim 2 will be examined. Aims 1, 2 and 3 are intimately linked, because they seek to study the same phenomenon at different levels of biological organization. Gene expression alterations may suggest histoarchitectural consequences and vice-versa. This exploratory research is central to the generation of testable hypotheses about cause-effect relationships linking prenatal hormonal exposure and mammary gland carcinogenesis and may finally provide the direct link between environmental exposures and incidence of breast cancer researchers have been looking for over the past 20 years. Moreover, if, as suspected, low doses of BPA increase the incidence of mammary cancer, this work may have a great impact on the way we study risk factors and conduct epidemiological studies. It may even influence public policy about prevention.

描述（由申请人提供）：乳腺癌发病率的增加促使科学家考虑对人体有活性的环境化学物质的可能作用。然而，寻找成人环境暴露与乳腺癌发病率之间相关性的流行病学研究基本上没有结论。然而，流行病学研究确实表明，胎儿雌激素水平的波动对成年后患乳腺癌的风险有长期影响。对小鼠的研究表明，产前暴露于低剂量的异种雌激素双酚A（BPA）会改变这些乳腺的发育。这些影响在接触停止后很久才显现出来。这些乳腺中末端芽和末端导管的数量增加是特别相关的，因为癌起源于这些结构。我们推测，产前暴露于低剂量的BPA可能会增加乳腺癌的风险，肿瘤的结果负责的机制可能包括临时表达的基因，介导乳腺发育。产前给予异雌激素可能会改变雌激素反应基因的表达，然后影响乳腺发育程序中的下游基因，使这些动物易患癌症。为了验证这一假设，我们将使用大鼠模型，其中暴露于致癌物亚硝基甲基脲（NMU）在青春期诱发乳腺癌。使用Wistar大鼠进行的一项初步研究表明，可以修改该模型，以评估胎儿暴露于环境相关的异种雌激素水平的影响。它产生的数据与提出的假设一致。目的1：确定产前BPA暴露导致乳腺癌发病率增加的水平。将测量从妊娠第9天至出生暴露于BPA的Wistar大鼠的肿瘤发生率和潜伏期。在50日龄时，动物将注射亚致癌剂量的NMU。目标二：检验产前BPA暴露在BPA暴露期间和整个生命过程中改变乳腺基因表达的假设。将从乳腺中分离总RNA，并通过DNA微阵列技术进行分析。在适当情况下，还将使用激光捕获显微切割和/或RNA线性扩增技术获得样本。上调和下调基因将通过QRTPCR确认。将通过原位杂交评估细胞分布。待分析的发育点为：1）妊娠期BPA暴露期间; 2）出生后5天; 3）青春期前后; 4）导管发育完成后。目标三：检验子宫内暴露于BPA改变大鼠乳腺组织结构并导致肿瘤前表型表达的假设。该目的将评估暴露于低剂量BPA是否会导致大鼠乳腺的特定形态学改变，这些改变可能导致致癌倾向，例如NMU给药时末端芽（TEB）和末端导管（TD）数量增加，TEB在青春期后的持续存在，以及在几个年龄点出现肿瘤前病变。此外，将检查目标2中研究的时间点乳腺的组织结构。目标1、2和3是密切相关的，因为它们试图在生物组织的不同层次上研究同一现象。基因表达的改变可能提示组织结构的后果，反之亦然。这项探索性的研究是核心的可检验的假说的产生的因果关系联系产前激素暴露和乳腺癌的发生，并可能最终提供环境暴露和乳腺癌的发病率之间的直接联系研究人员一直在寻找在过去的20年。此外，如果低剂量的BPA如怀疑的那样增加了乳腺癌的发病率，这项工作可能会对我们研究风险因素和进行流行病学研究的方式产生重大影响。它甚至可能影响有关预防的公共政策。