Polymorphism of Xeroderma Pigmentosum Group G and dietary flavonoid intake on the risk of lung and upper aero-digestive tract cancers

Lung and upper aero-digestive tract (UAT) cancers are major health concerns in the US. Tobacco smoking is a well-established risk factor for lung cancer; while tobacco smoking and alcohol drinking are well-documented risk factors for UAT cancers. Although cigarette smoke and alcohol are strongly carcinogenic, only a small fraction of individuals with those exposures will develop lung or UAT cancers in their lifetimes. Why some individuals with the exposures develop the above-mentioned cancers and others do not is not fully understood.; We conducted a population-based case-control study to assess two factors---polymorphism of the Xeroderma Pigmentosum Group G (XPG) and dietary intake of flavonoids---in the development of lung and UAT cancers. The study comprised 611 lung cancer cases, 601 UAT cancer cases, and 1,040 cancer-free controls. Detailed questionnaire information and buccal cells were collected during interviews. Unconditional logistic regression models were fitted to assess the effects with the adjustment for potential confounders.; We investigated the effects of XPG His1104Asp polymorphism on the risk of lung and UAT cancers among subjects (497 lung cancer cases, 443 UAT cancer cases, and 912 controls) with genotyping data. We found that the XPG Asp1104Asp genotype was inversely associated with lung cancer and squamous cell carcinoma of UAT (SCCUAT), with the combined His1104His and His1104Asp genotypes as the referent. Furthermore, we found some suggestion that the genotype might synergistically modify the effect of tobacco use on lung cancer risk.; We also investigated the intakes of flavonoid compounds on the risk of lung and UAT cancers. Comparisons were made between 558 lung cancer cases and 837 controls, and between 445 UAT cancer cases and 844 controls. We found inverse associations between lung cancer risk and the intakes of quercetin, kaempferol, catechin, epicatechin, epigallocatechin, epigallocatechin 3-gallate, and thearubigins. We also found inverse associations between UAT cancer risk and the intakes of catechin and epicatechin.; In conclusion, our study suggests that the XPG Asp1104Asp genotype may be associated with decreased susceptibility to lung cancer and SCCUAT. Our study also suggests that dietary intakes of certain flavonoid compounds may protect against lung and UAT cancers.