Project 4 - Oral Cell DNA Adducts and Urinary Biomarkers to Investigate Ethnic/Racial Differences in Lung Cancer Susceptibility

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Project 4. Oral Cell DNA Adducts and Urinary Biomarkers to Investigate Ethnic/Racial Differences in Lung Cancer Susceptibility. ABSTRACT Our ongoing studies demonstrate that carcinogen and toxicant doses account for some of the ethnic differences in risk for lung cancer among smokers as observed in the Multiethnic Cohort. Carcinogen and toxicant dose are only the first part of the risk paradigm for smoking-related lung cancer. DNA adduct formation is the next critical step because DNA adducts lead to the multiple mutations that are found in smokers' lungs and that cause miscoding, genetic instability, and cancer. Therefore, in this study, we will compare DNA adduct formation in smokers from three ethnic groups with differing risks for lung cancer: Native Hawaiians (highest risk), Whites (lower risk), and Japanese Americans (lowest risk). Three-hundred subjects will be recruited by the Clinical and Biomarker Core. Oral cells, as a surrogate for lung cells, will be obtained for DNA adduct measurements; urine samples will be collected for analysis of carcinogen and toxicant metabolites. Specific DNA adducts as well as DNA adductomic signatures will be obtained from oral cells of each subject. Analysis of the urine samples as well as those previously collected from never smokers will test the hypothesis that the high lung cancer susceptibility of Native Hawaiians is partially due to endogenous generation of the toxicants acrolein and crotonaldehyde, possibly due to inflammation and oxidative damage. Thus, our specific aims are: 1. Using high resolution mass spectrometry, quantify known DNA adducts in oral mucosa cells of 100 smokers from each ethnic group – Native Hawaiians, Whites, and Japanese Americans. DNA adducts of tobacco-specific compounds, formaldehyde, and acrolein will be quantified. 2. Analyze the urine of 100 smokers and 100 non-smokers from each of these groups for mercapturic acids of acrolein and crotonaldehyde, the F2-isoprostane 8-iso-PGF-2α, a biomarker of oxidative damage, and the prostaglandin E2 metabolite PGEM, a biomarker of inflammation, as well as total nicotine equivalents and total NNAL (smokers only). These data will provide critical information relevant to the high risk of Native Hawaiians for lung cancer, and in relationship to the DNA adduct measurements of Specific Aim 1. 3. Use our newly developed high resolution mass spectrometric, high throughput DNA adductomic approach to screen for known and unknown DNA adducts to identify a comprehensive DNA modification signature derived from cigarette smoking. a. Using a targeted DNA adductomic method we will screen for multiple DNA modifications simultaneously. The adducts analyzed in Specific Aim 1 will be added to a list including endogenous, 1,3-butadiene-derived (in collaboration with Project 3), aldehyde-derived and nitrosamine or alkylating agent-derived DNA adducts. In parallel we will apply our DNA adductomic method in an untargeted mode to investigate the presence of previously unknown DNA adducts. The unknown adducts detected by the untargeted analysis will be included in the list of targeted DNA adducts to ultimately obtain a sensitive method to assess overall DNA damage resulting from cigarette smoking . b. The list of DNA adducts created in Specific Aim 3a will be applied to investigate differences in the DNA damage signature in selected samples analyzed in Specific Aim 1. The results of this unique and innovative study will provide critical information relevant to the differing risks for lung cancer among Native Hawaiians, Whites, and Japanese Americans. We expect generation of new smoking-related DNA adduct signatures as well as important data on DNA adducts and urinary metabolites of known carcinogens and toxicants. The results will provide a critical test of the relationship of DNA adducts and certain urinary metabolites to lung cancer risk, thus possibly leading to new insights for lung cancer prevention strategies.