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

项目摘要 全世界有2亿多人长期暴露于饮用水中的砷， EPA或世界卫生组织的安全标准。有很强的实验和流行病学 有证据表明，低水平的砷与其他环境污染，如紫外线辐射， (UVR)增加致癌作用，表明砷是人类的共同致癌物。然而， 关于砷致癌的分子机制或预防砷的有效策略- 增强的癌症下一代测序分析的最新进展已经产生了强大的 用于定义肿瘤中不同突变特征的工具，这些特征可识别DNA修复过程中的特定缺陷， 致癌物暴露作为癌症病因的一部分。在目前提出的研究中，我们将应用这项新技术 以促进我们对砷作为一种共同致癌物的理解，当它与DNA破坏性紫外线结合时。我们 已经发表了大量的工作，证明砷干扰锌指基序， 选择DNA修复蛋白，导致修复能力下降，DNA损伤和突变增加 而锌可以缓解这些症状。人正常角质形成细胞暴露后突变模式的初步分析 0.1μM的亚砷酸盐、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>T突变和锌补充剂减少C>T突变，提示潜在的干预。 此外，由UVR和亚砷酸盐产生的突变特征不同于单独的UVR， 这表明亚砷酸盐改变了突变谱，而不是简单地放大紫外线辐射信号。基于 根据我们已发表的初步研究结果，我们假设砷能增强紫外线辐射引起的皮肤损伤， 通过破坏关键DNA修复蛋白XPA的锌指功能，从而导致 核苷酸切除修复缺陷导致体细胞突变的更大积累。在目标1中，我们 确定暴露于砷、紫外线或两者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确定的签名上的锌 由共同研究员亚历山德罗夫博士研发目的2探讨C>T突变的分子机制 砷通过转录偶联核苷酸切除修复抑制的增强作用， 生物化学方法和全基因组测序数据的计算分析。在目标3中，我们将使用 UVR诱导的皮肤癌发生的经证实的动物模型，以确定来自UVR的体内突变特征， 在有或没有砷的情况下诱发肿瘤以及锌对突变特征的影响。的结局 我们严格设计的研究有望提供金属诱导的第一个实验定义。 突变特征和对由组合暴露于两种 重要的和相关的环境侮辱，以及砷的机制的见解， 增强紫外线诱导的致癌作用以及锌如何提供保护。

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.