Polymorphic variants of human DNA glycosylase NEIL2 and lung cancer susceptibilit

描述(申请人提供)：尽管遗传易感性和环境因素，如接触遗传毒性物质在许多癌症中起着关键的病因作用，但目前还没有基因被确定为直接导致散发性肺癌的发展。与其他内部器官不同，肺持续暴露在内源性和外源性产生的氧化应激下，众所周知，氧化应激会对包括DNA在内的各种细胞大分子造成损害。氧化修饰的DNA碱基通常具有致突变性和/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癌遗传原因的研究，并研究了DNA修复基因变异在肺癌发生发展中的病因学作用。我们发现，新近发现的氧化碱基特异性DNA糖基酶NEIL2的下调会增加中国仓鼠V79肺癌细胞系和人肺细胞系A549细胞HPRT基因的突变频率。这些结果促使我们在肺癌患者(White)中寻找NEIL2基因的突变。我们在NEIL2基因编码区发现了四个错义突变，其中两个多态突变(R103Q和R257L)在癌症患者中的频率(16%)比正常、表面健康的人(2-4%)高得多。我们建议通过确定这些变异在其他主要种族群体(非洲裔美国人和西班牙裔美国人)中的流行率并从功能上表征所有这些变异来推进我们的研究。我们还将建立Neil2基因缺失的小鼠，以深入了解Neil2基因在S保护肺癌中的作用。因此，对野生型和变异型蛋白进行全面的生化分析，结合细胞生物学和动物研究，应该能让我们深入了解肺癌的分子发病机制，以及NIL-2‘S在预防这种疾病中可能的病因学作用。我们研究的中心目标是将DNA修复和突变的基本知识转化为评估与环境中诱变剂暴露相关的人类风险的实用方法。这些研究的成功完成不仅将坚定地确定DNA修复蛋白基因突变与肺癌发生之间的因果关系，而且还将为评估与环境中各种诱变剂有关的人类风险提供明确的见解。这些基本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：这项研究建议研究蛋白质在修复DNA损伤中的作用及其对癌症发展的可能影响。其中一个阶段是开发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，以确定这种蛋白是否存在与这种疾病相关的特定变异，以及这些变异是否功能失调。

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.