Cytosine Deamination Adducts and Cancer Etiology

DNA损伤驱动人类遗传疾病，包括癌症。外源性化学物质和内源性活性物质 分子可以破坏DNA碱基形成“加合物”。未修复的DNA加合物可以阻止DNA合成或 在聚合酶介导的复制过程中的错误编码。在人类癌症中观察到的突变景观是 由C：G到T：A的过渡突变主导。这些突变的一个主要原因是水解脱氨基作用 DNA中胞嘧啶和胞嘧啶类似物与其相应的尿嘧啶类似物的结合，产生一类胞嘧啶 脱氨加合物，xU.内源性DNA加合物如xU已被证明更难以研究，这是由于 这些加合物与正常DNA成分的相似性以及它们在正常、未受干扰的细胞中的形成 和纸巾。在本申请中，我们描述了创新的新方法，其将允许确定性地鉴定 xU加合物在DNA中使用质谱方法。此外，我们将测量的形成和修复 这种加合物在已知的癌症驱动突变热点和基因组范围内在正常人类细胞中， 已知有修复缺陷的细胞。我们还将检查代表正常的废弃人体组织中的xU， 发炎和患病的标本。这里提出的研究将提供一个前所未有的审查， 在DNA序列水平上，这类重要但研究不足的DNA加合物。的结果 拟议的研究可能会导致临床上有用的方法来检查损伤的历史， 给定的组织，并提供一个估计，以多远的损害已经进展到发展， 肿瘤的预期的结果将为癌症病因学和潜在的直接治疗方法提供新的线索。 降低癌症发病率并提供早期检测。

DNA damage drives human genetic disease including cancer. Exogenous chemicals and endogenous reactive molecules can damage DNA bases forming “adducts”. Unrepaired DNA adducts can block DNA synthesis or miscode during polymerase-mediated replication. The landscape of mutations observed in human cancers is dominated by C:G to T:A transition mutations. A major cause of these mutations is the hydrolytic deamination of cytosine and cytosine analogs in DNA to their corresponding uracil analogs, generating a class of cytosine deamination adducts, xU. Endogenous DNA adducts such as xU have proven more difficult to study due to the similarity of these adducts to normal DNA constituents as well as their formation in normal, unperturbed cells and tissues. In this application, we describe innovative new approaches that will allow definitive identification of xU adducts in DNA using mass spectrometry methods. Further, we will measure the formation and repair of such adducts at known cancer-driving mutational hotspots and genome-wide in both normal human cells and cells with known repair defects. We will also examine xU in discard human tissues representing normal, inflamed and diseased specimens. The studies proposed here will provide an unprecedented examination of this important but understudied class of DNA adducts at the level of DNA sequence. The results of the proposed studies could potentially result in clinically useful approaches to examine the damage history of a given tissue, and provide an estimate as to how far the damage had progressed toward the development of tumors. The anticipated results will shed new light on cancer etiology and potentially direct approaches to reduce cancer incidence and provide earlier detection.