Carcinogenic Cyclic Nitrosamine DNA Adducts

描述（由申请方提供）：本提案重点关注已确定人体暴露的四种致癌亚硝胺的DNA加合物：N-亚硝基吡咯烷（NPYR）、N-亚硝基哌啶（NPIP）、N-亚硝基肌氨酸（NSAR）和3-（甲基亚硝胺）丙酸（MNPA）。所有这些致癌物质都存在于人类环境中，可能是在人体内内源性形成的，并已在人类尿液中检测到。DNA加合物在亚硝胺致癌作用中是绝对关键的。我们的总体假设是，这些亚硝胺在人体组织中产生DNA加合物，因此与人类癌症的原因有关。在该项目的前五年中，我们在体外广泛表征了由α-乙酰氧基NPYR（NPYR代谢活化的模型化合物）形成的DNA加合物，以及相关化合物巴豆醛、乙醛及其羟醛缩合产物的DNA加合物。通过NPYR和NPIP的代谢比较实验，我们也为这两种亚硝胺在大鼠体内的致癌活性的强烈对比建立了合理的依据。在目前的更新建议，我们的重点是在体内形成的DNA加合物的表征和分析，在大鼠和人类，从这些亚硝胺。我们假设，每个亚硝胺将产生一个表型组的DNA加合物。这些加合物可用作人体暴露于这些致癌物及其代谢活化的生物标志物。我们的具体目标是：1.鉴定NPYR处理后大鼠肝脏中形成的DNA加合物; 2.建立一种全面的液相色谱-电喷雾电离-质谱（LC-ESI- MS）方法来定量NPYR在处理大鼠组织和人体组织中的DNA加合物，并将这些研究扩展到NPIP; 3.鉴定大鼠中NSAR和MNPA的DNA加合物，并开发LC-ESI-MS方法来定量大鼠和人体组织中的DNA加合物。这项研究的结果将提供关键的数据，我们了解的DNA加合物的形成和致癌作用，这四个亚硝胺与良好的记录人类接触。我们的方法是创新的，因为很少有实验室已经开发出可靠的方法，用于定量分析特定的DNA加合物，反映了特定致癌物在人体内的代谢活化。拟议的研究是重要的，因为已知人类暴露于这些致癌物通过饮食，烟草制品，和内源性形成。

DESCRIPTION (provided by applicant): This proposal focuses on DNA adducts of four carcinogenic nitrosamines to which human exposure has been firmly established: A/-nitrosopyrrolidine (NPYR), A/-nitrosopiperidine (NPIP), A/-nitrososarcosine (NSAR), and 3-(methylnitrosamino)propionic acid (MNPA). All of these carcinogens occur in the human environment, are likely formed endogenously in humans, and have been detected in human urine. DNA adducts are absolutely critical in nitrosamine carcinogenesis. Our overall hypothesis is that these nitrosamines produce DNA adducts in human tissues and are therefore involved as causes of human cancer. In the previous five years of this program, we have extensively characterized, in vitro, DNA adducts formed from a-acetoxyNPYR, a model compound for the metabolic activation of NPYR, as well as DNA adducts of the related compounds crotonaldehyde, acetaldehyde, and their aldol condensation products. We have also established, through comparative metabolism experiments of NPYR and NPIP, a reasonable basis for the strongly contrasting carcinogenic activities of these two nitrosamines in rats. In the current renewal proposal, our focus is on the characterization and analysis of DNA adducts formed in vivo, in rats and humans, from these nitrosamines. We hypothesize that each nitrosamine will produce a phenotypic group of DNA adducts. These adducts can be used as biomarkers of human exposure to and metabolic activation of these carcinogens. Our specific aims are: 1. Identify the DNA adducts that are formed in rat liver upon treatment with NPYR; 2. Develop a comprehensive liquid chromatography-electrospray ionization-mass spectrometric (LC-ESI- MS) method to quantify DNA adducts of NPYR in tissues of treated rats and in human tissues, and extend these studies to NPIP; 3. Identify DNA adducts of NSAR and MNPA in rats and develop LC-ESI-MS methods to quantify them in rat and human tissues. The results of this research will provide critical data pertinent to our understanding of DNA adduct formation and carcinogenesis by these four nitrosamines with well-documented human exposure. Our approach is innovative because few laboratories have developed reliable methods for the quantitative analysis of specific DNA adducts which reflect the metabolic activation of particular carcinogens in humans. The proposed research is significant because of the known human exposure to these carcinogens through the diet, tobacco products, and endogenous formation.