In utero availability of the essential nutrient, choline, and mammary cancer risk

描述（由申请人提供）：拟议研究的目的是检验产前胆碱可调节乳腺癌发展风险的假设。这一概念是基于证据，即产前胆碱的可得性具有持久的生物效应，持续到成年和老年。胆碱是人体必需的营养素。由于胎儿发育构成了对胆碱需求增加的时期，美国饮食指南呼吁妇女在怀孕期间增加胆碱摄入量。在我们之前的研究中，我们关注的是产前胆碱对大脑发育和认知功能的影响，我们发现在妊娠后半期补充胆碱的大鼠在整个生命周期中都表现出记忆力的改善。这些影响与大脑的分子、生化和结构变化有关。在成年大鼠中，缺乏饮食胆碱会导致肝癌，这是在没有任何已知致癌物的情况下导致癌症的唯一营养缺乏症。我们发现，成年期胆碱缺乏会增加患乳腺癌的风险，而补充胆碱则会降低服用致癌物丙卡嗪的大鼠患乳腺癌的风险。目的1旨在验证这样一种假设，即通过组织学技术和微阵列确定的基因表达模式监测，产前胆碱可用性（缺乏、充足和补充）调节雌性大鼠乳腺的发育。为了评估后一种变化的机制，我们将基于胆碱作为甲基的供体可以改变体内DNA甲基化和基因表达的证据，测试产前胆碱可用性改变基因调控元件DNA甲基化的假设。我们将研究受这一过程调控的选定基因的DNA甲基化，我们发现其表达受产前胆碱可用性（如胰岛素样生长因子II， Igf2）的调节。Aim 2的目的是测试产前胆碱可调节乳腺癌发生的假设，使用被7,12 -二甲基苯[a]蒽（DMBA）治疗的Sprague Dawley大鼠作为模型，DMBA是一种致癌物质，可导致类似人类乳腺癌的肿瘤。肿瘤发病率和肿瘤发展将被确定。这些动物乳腺组织的癌前病变和恶性病变将使用组织学和微阵列技术进行评估。在这类的初步研究中，我们观察到在产前胆碱补充大鼠中疾病进展缓慢的趋势，以及由于产前胆碱缺乏而加速肿瘤生长的趋势。与对照组和产前胆碱缺乏组相比，产前胆碱补充组的乳腺肿瘤细胞cyclin D1、STATS和催乳素受体的表达较高，而STATS mRNA的表达较低。该提案是根据美国国立卫生研究院项目公告而准备的，使用R21探索性发展资助机制，旨在为研究发展的早期阶段提供支持，例如评估新研究领域可行性的项目。我们研究的最终目标是将我们的结果与人类联系起来，并制定有利于人类的围产期营养策略。

DESCRIPTION (provided by applicant): The goal of the proposed studies is to test the hypothesis that prenatal availability of choline modulates the risk of development of mammary carcinoma. This notion is based on evidence that prenatal availability of choline has long-lasting biological effects persisting into adulthood and old age. Choline is an essential nutrient for humans. Because fetal development constitutes a period of increased demand for choline, US dietary guidelines call for increased choline intake by women during pregnancy. In our previous studies, that focused on the effects of prenatal availability of choline on brain development and cognitive functions, we found that rats supplemented with choline during the second half of gestation exhibited improvements in memory which lasted throughout their entire lifespan. These effects correlated with molecular, biochemical, and structural changes in brain. In adult rats, lack of dietary choline causes hepatocarcinoma and is the only nutritional deficiency that leads to cancer in the absence of any known carcinogens. We found that choline deficiency in adulthood increased mammary cancer risk while choline supplementation reduced it in rats treated with procarbazine as a carcinogen. Aim 1 is designed to test the hypothesis that prenatal choline availability (deficiency, sufficiency, and supplementation) modulates the development of the mammary gland in female rats as monitored by histological techniques and patterns of gene expression determined by microarrays. To assess the mechanisms of the latter changes we will test the hypothesis that prenatal availability of choline alters DNA methylation of the regulatory elements of genes, based on the evidence that choline, via its action as a donor of methyl groups, can alter DNA methylation and gene expression in vivo. We will study DNA methylation of selected genes that are regulated by this process and whose expression we found to be modulated by prenatal availability of choline (e.g. insulin-like growth factor II, Igf2). Aim 2 is designed to test the hypothesis that prenatal availability of choline modulates mammary carcinogenesis using as a model Sprague Dawley rats treated with 7, 12-dimethylbenz[a]anthracene (DMBA), a carcinogen that causes tumors similar to human breast cancers. Tumor incidence and tumor development will be determined. Premalignant as well as malignant changes in mammary tissues from these animals will be evaluated using histological and microarray techniques. In a pilot study of this kind we observed trends for a slowed disease progression in prenatally choline-supplemented rats and an acceleration of tumor growth by prenatal choline deficiency. The mammary tumors from prenatally choline-supplemented rats had higher expression of cyclin D1, STATS, and prolactin receptor and lower expression of STATS mRNA as compared to the tumors from the control- and prenatally choline-deficient subjects. This proposal, prepared in response to an NIH Program Announcement, uses the R21 Exploratory Developmental grant mechanism designed to provide support for the early stages of research development such as projects to assess the feasibility of a novel area of investigation. The ultimate goal of our studies is to relate our results to humans and to develop perinatal nutritional strategies which could benefit people.