Polymorphic variants of human DNA glycosylase NEIL2 and lung cancer susceptibilit

描述（由申请人提供）：尽管遗传易感性和环境因素（如暴露于基因毒性物质）在许多癌症中起着关键的病因学作用，但尚未发现与散发性肺细胞癌发展直接相关的基因。与其他内脏器官不同，肺部持续暴露于内源性和外源性氧化应激中，已知氧化应激会对包括DNA在内的各种细胞大分子造成损伤。氧化修饰的DNA碱基通常具有诱变性和/或毒性。这些DNA碱基损伤主要通过DNA碱基切除修复途径修复。DNA修复基因突变可能与许多散发性癌症的发生有关。我们开展了一项旨在确定肺细胞癌的遗传原因的研究，并研究DNA修复基因变异是否在肺癌的发生和发展中起病因学作用。我们发现，NEIL2（一种最近发现的氧化碱基特异性DNA糖基酶）的下调会增加中国仓鼠V79肺细胞系和人肺细胞系A549的hprt基因突变频率。这些结果促使我们在肺癌患者中寻找NEIL2位点突变（White）。我们在NEIL2基因的编码区发现了四个错义突变；其中，两种多态变异（R103Q和R257L）在癌症患者中的频率（16%）远高于正常、明显健康的个体（2-4%）。我们建议通过确定这些变异在其他主要种族群体（非裔美国人和西班牙裔美国人）中的患病率，并对所有这些变异进行功能表征，来推进我们的研究。我们还将产生Neil2缺失小鼠，以深入了解Neil2在保护肺癌中的作用。因此，结合细胞生物学和动物研究，对野生型和变异蛋白进行全面的生化分析，将使我们对肺癌的分子发病机制和NEIL2在预防这种疾病中的可能病因学作用有更深入的了解。我们研究的中心目标是将DNA修复和诱变的基本知识转化为评估与环境中暴露于诱变剂相关的人类风险的实用方法。这些研究的成功完成不仅将牢固地确立DNA修复蛋白基因突变与肺癌发展的因果关系，而且将为评估与暴露于环境中各种诱变剂相关的人类风险提供明确的见解。这些基础知识可用于制定肺癌患者的治疗干预策略。公共卫生相关性：本研究旨在研究一种蛋白质在修复DNA损伤中的作用及其对癌症发展的可能影响。其中一个阶段是培育一种不产生这种蛋白质的转基因小鼠，并研究其患癌症的可能性。第二阶段是检查肺癌患者的血液样本，以确定这种蛋白质是否存在与这种疾病相关的特定变体，以及这些变体是否功能失调。

DESCRIPTION (provided by applicant): Although genetic predisposition and environmental factors such as exposure to genotoxic agents play critical etiological roles in many cancers, no gene yet has been identified as being directly responsible for the development of sporadic lung cell carcinoma. Unlike other internal organs, the lungs are continuously exposed to endogenous and exogenously generated oxidative stress, which is known to cause damage to various cellular macromolecules, including DNA. Oxidatively modified DNA bases are often mutagenic and/or toxic. These DNA base lesions are repaired primarily via the DNA base excision repair pathway. DNA repair gene mutations are likely to be involved in developing many sporadic cancers. We undertook a study aimed at identifying the genetic cause of lung cell carcinoma and investigated whether DNA repair gene variants play an etiological role in lung cancer initiation and development. We have found that downregulation of NEIL2, a recently identified oxidized base-specific DNA glycosylase, increases mutation frequency in the hprt gene of Chinese hamster V79 lung cell line as well as human lung cell line A549. These results prompted us to search for mutations at the NEIL2 locus in lung cancer patients (White). We identified four missense mutations in the coding regions of the NEIL2 gene; of these, two polymorphic variants (R103Q and R257L) were much more frequent (16%) in cancer patients than in normal, apparently healthy individuals (2-4%). We propose to advance our study by determining the prevalence of these variants in the other major ethnic groups (African American and Hispanics) as well and characterizing all these variants functionally. We will also generate Neil2-null mice to get insight into Neil2's role in protecting lung cancer. Thus a comprehensive biochemical analysis of wild-type vs. variant proteins along with cell biological and animal studies should give us insights into the molecular pathogenesis of lung cancer and NEIL2's likely etiological role in protecting against this disease. The central goal of our study is to translate basic knowledge of DNA repair and mutagenesis into practical approaches for assessing human risks associated with exposure to mutagenic agents in the environment. Successful completion of these studies will not only firmly establish the causal involvement of genetic mutation of DNA repair protein and the development of lung cancer but will also provide definitive insights for assessing human risks associated with exposure to various mutagens in the environment. Such basic knowledge could be exploited in developing therapeutic intervention strategies for lung cancer patients. PUBLIC HEALTH RELEVANCE: This study proposes to examine the role of a protein in repairing damage to DNA and its possible effect on cancer development. One phase is to develop a genetically altered mouse that does not produce this protein and study its potential to develop cancers. The second phase is to examine blood samples from lung cancer patients to determine if there are particular variants of this protein associated with this disease and if these variants are dysfunctional.