Mutational Signatures of a Combined Environmental Exposure: Arsenic and Ultraviolet Radiation

项目摘要 全世界有超过2亿人长期接触饮用水中浓度高于标准的砷。 美国环保局或世界卫生组织的安全标准。有很强的实验性和流行病学 有证据表明，低水平的砷与其他环境伤害，如紫外线辐射相结合 (UVR)会增加致癌作用，这表明砷是人类的共同致癌物。然而，人们对此知之甚少 关于砷共同致癌的分子机制或预防砷的有效策略 增大的癌症。在分析下一代测序方面的最新进展已经产生了强大的 定义肿瘤中不同突变特征的工具，以识别DNA修复过程中的特定缺陷或 致癌暴露是癌症病因学的一部分。在目前提议的研究中，我们将应用这项新技术 增进我们对砷在DNA损伤UVR时是一种共同致癌物质的理解。我们 已经发表了大量的工作证明砷干扰锌指图案 选择导致修复能力降低、DNA损伤和突变增加的DNA修复蛋白 而锌则能缓解这些症状。辐射对正常人角质形成细胞突变模式的初步分析 0.1微米亚砷酸盐、UVR或两者都显示，这种低浓度的亚砷酸盐足以增强UVR- 诱导的C&gt；T突变和补锌减少了C&gt；T突变，暗示了一种潜在的干预。 此外，紫外线和亚砷酸盐产生的突变特征不同于紫外线单独产生的突变特征， 这表明亚砷酸盐改变了突变谱，而不是简单地放大了UVR特征。基于 我们已发表的和初步的发现是，我们假设砷可以增强紫外线辐射诱导的皮肤 通过破坏关键DNA修复蛋白XPA的锌指功能而致癌，这反过来又导致 核苷酸切除修复不足导致更多的体细胞突变积累。在目标1中，我们将 确定暴露在砷和/或紫外线下是否会产生独特的突变特征，以及 使用全基因组测序和先进的计算方法对已识别的特征进行锌 由合作研究员亚历山德罗夫博士开发。目的2研究C&GT；T突变的分子机制 砷对转录偶联核苷酸切除修复抑制的增强作用 全基因组测序数据的生化方法和计算分析。在目标3中，我们将使用 已证实的紫外线诱发皮肤癌的动物模型，以确定紫外线照射的体内突变特征。 加砷或不加砷诱发肿瘤及锌对突变信号的影响。成果来自于 我们精心设计的研究有望提供金属诱导的第一个实验定义 突变特征及联合暴露致突变特征的首次分析 重要的和相关的环境侮辱，以及对砷 增强紫外线诱导的致癌作用以及锌如何起到保护作用。

Project Summary Over 200 million people worldwide are chronically exposed to arsenic in drinking water at concentrations above the EPA or World Health Organization safety standard. There is strong experimental and epidemiological evidence that low levels of arsenic in combination with other environmental insults such as ultraviolet radiation (UVR) increases carcinogenesis, suggesting arsenic is a co-carcinogen in humans. However, little is known about the molecular mechanisms of arsenic co-carcinogenesis or effective strategies for prevention of arsenic- augmented cancers. Recent advances in analysis of next generation sequencing have given rise to powerful tools to define distinct mutational signatures in tumors that identify specific defects in DNA repair processes or carcinogenic exposures as part of cancer etiology. In current proposed study we will apply this new technology to advance our understanding of arsenic as a co-carcinogen when combined with the DNA damaging UVR. We have published an extensive body of work demonstrating that arsenic interferes with the zinc finger motifs of select DNA repair proteins leading to decreased repair capacity and increased DNA damage and mutations that are alleviated by zinc. A preliminary mutation pattern analysis of normal human keratinocytes exposed to 0.1 µM arsenite, UVR, or both revealed that this low concentration of arsenite was sufficient to enhance UVR- induced C>T mutations and zinc supplement reduced C>T mutations suggesting a potential intervention. Furthermore, the mutational signatures generated by UVR and arsenite differ from those of UVR alone, indicating that arsenite modifies the mutation spectrum rather than simply amplify the UVR signature. Based on our published and preliminary findings, we hypothesize that arsenic enhances UVR-induced skin carcinogenesis by disrupting the zinc finger function of the key DNA repair protein XPA, which in turn, results in deficient nucleotide excision repair leading to greater accumulation of somatic mutations. In Aim 1, we will determine whether exposure to arsenic, UVR or both generates unique mutational signatures and the impact of zinc on identified signatures using whole genome sequencing and advanced computational approaches developed by co-investigator Dr. Alexandrov. Aim 2 will investigate the molecular mechanism of C>T mutation enhancement by arsenic through transcription-coupled nucleotide excision repair inhibition using both biochemical approaches and computational analysis of whole genome sequencing data. In Aim 3, we will use a proven animal model of UVR-induced skin carcinogenesis to define in vivo mutational signatures from UVR- induced tumors with or without arsenic and the impact of zinc on the mutation signature. The outcomes from our rigorously designed studies are expected to provide the first experimental definition of a metal-induced mutation signature and the first analysis of mutational signatures generated by combination exposures to two important and relevant environmental insults, as well as the insights into mechanisms by which arsenic enhances UVR-induced carcinogenesis and how zinc confers protection.