To date our research on susceptibility to tobacco carcinogenesis has focused on the polycyclic hydrocarbon, benzo[a]pyrene, as an in vitro mutagen challenge for functional assays of DNA damage and repair. The tobacco-specific nitrosamine, NNK, is a selective inducer of adenocarcinoma (AC) of the lung, now the leading histologic subtype in the US. We therefore propose to build upon the infrastructure created from our parent grant, """"""""Ecogenetics Study of Lung Cancer"""""""" to extend our research to a detailed assessment of susceptibility to NNK, incorporating functional assays of DNA damage and repair and specific polymorphisms in NNK-relevant metabolic and repair pathways. We will enroll 500 patients with newly diagnosed, previously untreated AC of the lung, from M. D. Anderson Cancer Center who are residents of Harris County, Texas, or the seven contiguous counties. Controls (n=500) will be frequency-matched to the cases on age, gender, ethnicity and smoking status (never, former and current) identified from Houston's largest private multi-specialty physician group encompassing a network of 23 clinics. By following the same design for data collection and control selection in the renewal, we can combine previously recruited AC cases (n= 600) and controls (n=600) from the parent grant with this renewal study for epidemiologic and genotype analyses, and thereby achieve time and cost efficiency and statistical power. Epidemiologic analyses will focus on smoking, diet (micronutrients such as isothiocyanates and folate intake), and family history. We propose to apply a panel of functional assays of DNA damage and repair, using activated NNK acetate (NNKOAc) as the in vitro challenge mutagen in the host cell reactivation, comet and micronucleus assays. We will evaluate frequencies of polymorphisms in genes involved in the following carefully selected pathways: metabolic activation and detoxification of NNK; repair via the alkyltransferase pathway; methylation genes; and p53. In a subgroup of cases for whom tumor tissue is available (estimated 300 patients), we will evaluate genetic (mutations in K-ras) and epigenetic changes (CpG island methylation in the promoter region of select genes). Analyses will focus on diet-gene, gene-environment, genotype/phenotype and surrogate tissue/target tissue genetic and epigenetic correlations. The unifying theme is that susceptibility to the genotoxic effects of NNK is an important determinant of lung AC risk. Identification of high risk smokers has potential for primary and secondary preventive initiatives. This research is also applicable to other sites since tobacco-specific nitrosamines are causative agents in esophagus, pancreas and oral cavity cancers, and are the most prevalent carcinogen in snuff products. ? ?
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