Epigenetic effects on susceptibility to heavy metal & PAH induced DNA damage

表观遗传对重金属敏感性的影响

• 批准号: 6442969
• 负责人: Eric Moon-shong M. TANG
• 金额: $ 16.41万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6442969
• 关键词: DNA damage; adduct; arsenic; benzopyrenes; carbopolycyclic compound; chemical carcinogenesis; chromium; clinical research; environmental toxicology; gene environment interaction; genetic susceptibility; hazardous substances; heavy metals; human subject; methylation; nickel; p53 gene /protein; polymerase chain reaction

Heavy metals such as arsenic, nickel, and chromium as well as polycyclic aromatic hydrocarbons (PAHs) as benzo(a)pyrene are common environmental contaminants. Human exposure to such toxicants greatly increases cancer risk. The carcinogenicity of PAHs has been attributed to their covalent binding to DNA, which can result in mutations that ultimately lead to carcinogenesis. The mechanisms of metal-induced carcinogenesis are less clear. It has been found that nickel and arsenic exposure can induce DNA hypermethylation. Such non-mutational epigenetic changes could also result in suppression of tumor suppressor genes, such as the p53 gene, triggering tumorigenesis. Recently, we have found that the guanines at C5 cytosine methylated CpG sites are the major DNA targets of many PAHs, including benzo(a)pyrene diol epoxide (BPDE). In fact, we have found that the BPDE binding spectrum in the tumor suppressor p53 gene coincides with the mutation spectrum of this gene in lung cancer. It has been found that a mutated p53 gene is sufficient to trigger carcinogenesis in animal models, and that more importantly, 50% of human cancers have a mutation in the p53 gene. These findings have lead us to hypothesize that targeted DNA damage, rather than selection, is the major determinant of the p53 mutation spectrum in cancer, and that the CpG selection, is the major determinant of the p53 mutation spectrum in human cancer, and that the CpG methylation status of an individual p53 gene may determine the susceptibility of this gene to DNA damage and mutation. These findings have led us to hypothesize that targeted DNA damage, rather than selection, is the major determinant of the p53 mutation spectrum in human cancer, and that the CpG methylation status of an individual p53 gene may determine the susceptibility of this gene to DNA damage and mutation. In light of these findings, we propose that the carcinogenicity of nickel, arsenic and chromium may be partly due to their ability to induce DNA hypermethylation, which in turn enhances the susceptibility of methylated tumor suppressor genes and protooncogenes to bulky carcinogen-induced DNA damage and mutations. The objective of this research is to test the hypothesis using two state-of-the-art technologies; UvrABC-ligation-mediated-PCR to map DNA adducts at the single nucleotide level, and the p53 GeneChip to detect mutations and cytosine methylation. We will determine: 1) the p53 gene methylation status in lymphocytes of different individuals and assess its relationship with the susceptibility to BDE damage, 2) whether nickel, arsenic, and chromium induce changes in the methylation status of the p53 gene and whether nickel, arsenic, and chromium induce changes in the methylation status of the p53 gene and, consequently, in the susceptibility of this gene to BPDE induced-DNA damage, and 3) the effect of nickel, arsenic and chromium treatment on the repair of BPDE-DNA adducts in the p53, beta-actin and HPRT gene.

砷、镍和铬等重金属以及苯并芘等多环芳烃 (PAH) 是常见的环境污染物。人类接触此类有毒物质会大大增加癌症风险。 PAH 的致癌性归因于它们与 DNA 的共价结合，这可能导致突变，最终导致致癌。金属诱发致癌的机制尚不清楚。研究发现，镍和砷暴露可诱发DNA高甲基化。这种非突变表观遗传变化也可能导致抑癌基因（例如 p53 基因）受到抑制，从而引发肿瘤发生。最近，我们发现 C5 胞嘧啶甲基化 CpG 位点的鸟嘌呤是许多 PAH 的主要 DNA 靶标，包括苯并（a）芘二醇环氧化物（BPDE）。事实上，我们发现抑癌基因p53基因中的BPDE结合谱与该基因在肺癌中的突变谱是一致的。在动物模型中发现，一个突变的p53基因足以引发癌变，更重要的是，50%的人类癌症都存在p53基因突变。这些发现使我们推测，靶向DNA损伤而不是选择是癌症中p53突变谱的主要决定因素，而CpG选择是人类癌症中p53突变谱的主要决定因素，并且单个p53基因的CpG甲基化状态可能决定该基因对DNA损伤和突变的易感性。这些发现使我们推测，人类癌症中 p53 突变谱的主要决定因素是靶向 DNA 损伤，而不是选择，并且单个 p53 基因的 CpG 甲基化状态可能决定该基因对 DNA 损伤和突变的易感性。根据这些发现，我们提出镍、砷和铬的致癌性可能部分归因于它们诱导 DNA 高甲基化的能力，这反过来又增强了甲基化抑癌基因和原癌基因对大量致癌物诱导的 DNA 损伤和突变的敏感性。这项研究的目的是使用两种最先进的技术来检验这一假设； UvrABC 连接介导的 PCR 在单核苷酸水平绘制 DNA 加合物图谱，p53 GeneChip 检测突变和胞嘧啶甲基化。我们将确定：1) 不同个体淋巴细胞中 p53 基因甲基化状态，并评估其与 BDE 损伤易感性的关系，2) 镍、砷和铬是否会引起 p53 基因甲基化状态的变化，以及镍、砷和铬是否会引起 p53 基因甲基化状态的变化，从而导致该基因对 BDE 损伤的易感性发生变化。 BPDE 诱导 DNA 损伤，3) 镍、砷和铬处理对 p53、β-肌动蛋白和 HPRT 基因中 BPDE-DNA 加合物修复的影响。