DNA methylation alterations in response to pesticides exposure

描述（由申请人提供）：本申请涉及广泛的挑战领域（08）基因组学和特定的挑战主题，08-ES-104：鉴定与环境暴露相关的表观遗传标记的改变。在美国，接触农药是无处不在的，超过一百万人受到高职业暴露。农药及其残留物在我们的环境中无处不在，我们对农药的依赖正在增加。尽管在美国销售的所有杀虫剂都通过了环境保护署（EPA）的致癌性测试，但在流行病学研究中，暴露于杀虫剂与人类癌症发病率增加有关。我们最近对农业健康研究（AHS）队列的分析也表明，农药暴露会增加几种癌症的风险。AHS队列是世界上对爱荷华州和北卡罗来纳州农药施用者进行的最大规模的前瞻性研究。令人担忧的是，EPA对化学致癌性的评估主要基于对诱变事件的检测。改变的DNA甲基化，一种新出现的癌症标志，在EPA测试系统中没有考虑。新出现的证据表明，启动子DNA甲基化受到环境暴露的影响。先前的研究表明，血细胞DNA中包含的表观遗传信息，包括DNA甲基化，是癌症风险的有价值的预测标志。血液是外部环境和人体组织之间的管道，因此构成了评估环境毒物对人体健康影响的种子靶组织。我们最近的初步数据将美国最常用的杀虫剂有机磷农药（OP）暴露与血液DNA中几种肿瘤抑制基因的启动子甲基化增加联系起来。我们进一步证实了这一发现在体外，使用人血细胞处理OP。综上所述，我们假设暴露于农药可以诱导血细胞DNA中启动子DNA甲基化的变化，这将为农药暴露与癌症风险之间的关联提供目前未知的机制见解。我们建议研究OP暴露是否会改变人类受试者和OP处理的细胞系中基因启动子DNA甲基化模式。我们将首先在具有最高和最低OP暴露的人群亚组和细胞系中进行全基因组筛选。研究结果将进行验证，使用基因特异性的方法在一个独立的复制人口，和不同剂量的OP治疗后的细胞。我们还将研究是否甲基供体相关的营养物质和相关的遗传多态性，DNA甲基化过程中的两个主要因素，修改OP暴露和启动子DNA甲基化水平之间的关联。本研究中提出的调查将利用现有NIEHS资助的AHS横断面研究中包含的人口和资源。 公共卫生相关性：本研究检查了700名AHS参与者的有机磷农药（OP）暴露和神经系统疾病。因此，我们将获得明确的OP暴露数据、血液样本中的DNA以及可能影响数据评价的混杂和修饰效应的综合数据。此外，我们已经建立了一个体外系统，用于评估农药的表观遗传效应。这些都是新颖和创新的研究，因为DNA甲基化研究与互补的人类数据和细胞系与农药处理还没有完成。由于美国和世界范围内广泛使用农药，这项研究将具有很高的公共卫生意义。一个主要的优势是研究的农民人口具有良好的特点暴露评估。在一般人群队列中很难获得如此高质量和完整的农药使用数据。另一个主要优势是，这项研究保证及时完成（如果得到资助的话），因为DNA已经可以进行分析，其他相关数据也很容易获得。农药在美国和世界各地广泛使用，在我们的环境中无处不在。我们对农药的依赖越来越大。虽然在美国销售的农药已经通过了环境保护署（EPA）的致癌能力测试，并被批准为安全的，但一再表明，一些农药会增加人类癌症的发病率。令人担忧的是，EPA对农药安全性的评估不包括检查DNA甲基化改变的测试，这是一种新出现的癌症标志。我们提出的研究是调查农药暴露对DNA甲基化改变的影响，在一个子集的人口从农业健康研究（AHS），在世界上最大的前瞻性研究农药施用者从爱荷华州和北卡罗来纳州。这项研究的结果将解决我们对农药及其致癌能力的认识中的一个关键空白。

DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (08) Genomics and specific Challenge Topic, 08-ES-104: Identification of alterations in epigenetic marks related to environmental exposures. In the US, exposure to pesticides is ubiquitous, and over one million people are subjected to high occupational exposure. Pesticides and their residues are pervasive in our environment and our dependence upon pesticides is increasing. Although all pesticides sold in the US have passed Environmental Protection Agency (EPA) tests for carcinogenicity, exposure to pesticides have repeatedly been associated with increased human cancer incidence in epidemiologic studies. Our recent analysis of the Agricultural Health Study (AHS) cohort, the largest prospective study in the world of pesticide applicators from Iowa and North Carolina, also indicates that pesticide exposure increases risk for several cancers. The concern is that EPA's evaluation of chemical carcinogenicity is primarily based on the detection of mutagenic events. Altered DNA methylation, an emerging hallmark of cancer, is not considered in the EPA testing system. Emerging evidence suggests that promoter DNA methylation is affected by environmental exposures. Prior studies have shown that epigenetic information, including DNA methylation, contained in blood cell DNA represents a valuable predictive marker of cancer risk. Blood is a conduit between the external environment and human tissues, and as such constitutes a seminal target tissue to evaluate the effects of environmental toxicants on human health. Our preliminary data recently linked exposure to organophosphate pesticides (OPs), the most commonly used insecticides in the US, to increased promoter methylation of several tumor suppressor genes in blood DNA. We further confirmed this finding in vitro, using human blood cells treated with OPs. Taken together, we hypothesize that exposure to pesticides can induce promoter DNA methylation changes in blood cell DNA, and that this will provide currently unknown mechanistic insights into the association between pesticide exposure and cancer risk. We propose to study whether OP exposure alters gene promoter DNA methylation patterns in human subjects, and in OP-treated cell lines. We will first conduct a genome-wide screening in a subset of the population with the highest and lowest OP exposure, and in cell lines. Findings will then be validated using a gene-specific approach in an independent replication population, and after treatment of cells with varying doses of OP. We will also examine whether methyl donor-related nutrients and related genetic polymorphisms, two major factors in DNA methylation process, modify the associations between OP exposure and promoter DNA methylation levels. The investigations proposed in the current study will take advantage of the population and resources included in an existing NIEHS-funded cross-sectional study nested in AHS. PUBLIC HEALTH RELEVANCE: This study examines organophosphate pesticide (OP) exposure and neurological disorders in 700 AHS participants. Thus, we will have well-defined OP exposure data, DNA from blood samples, and comprehensive data for confounding and modifying effects that may impact data evaluation. Further, we have an established in-vitro system for evaluating epigenetic effects of pesticides. These are novel and innovative investigations, as DNA methylation studies with complementary human data and cell lines with pesticide treatment have not been done. This study will have high public health significance due to the widespread pesticide use in the US and worldwide. A major strength is the study population of farmers with well-characterized exposure assessment. Data on pesticide use, of this high quality and completeness, would be difficult to achieve in a general population cohort. Another major strength is that this study is guaranteed to be completed in a timely manner (if funded), since the DNA is ready for analysis, and other relevant data are also readily available. Pesticides are widely used in the US and worldwide, are pervasive in our environment. Our dependence upon pesticides is increasing. Although pesticides sold in the US have passed the Environmental Protection Agency (EPA) tests for their ability to cause cancer and been approved as safe, it has repeatedly been shown that some pesticides increased human cancer incidence. The concern is that EPA's evaluation on the safety of pesticides does not include the tests that examine DNA methylation alterations, a new emerging hallmark of cancer. Our proposed study is to investigate the effects of pesticides exposure on DNA methylation alterations in a subset of the population from the Agricultural Health Study (AHS), the largest prospective study in the world of pesticides applicators from Iowa and North Carolina. The results from this study will address a critical gap in our knowledge of pesticides and their ability to cause cancer.