Role of alcohol dehydrogenase 3 and cytochrome P-4502E1 genotypes in susceptibility to cancers of the upper aerodigestive tract

Abstract

Alcohol is a recognized risk factor for upper aerodigestive tract (UAT) cancers, but the mechanism by which alcohol causes cancer remains obscure. Ethanol is oxidized to acetaldehyde (the suspected carcinogenic agent in alcohol) by alcohol dehydrogenases (ADHs) and cytochrome P-4502E1 (CYP2E1), both of which exhibit great inter-individual variability in activity. The hypothesis that these polymorphisms influence susceptibility to alcohol-related cancers remains poorly documented. We investigated whether ADH(3) and CYP2E1 DraI and RsaI genotypes modified the risk of UAT cancers among 121 oral cavity/pharyngeal cancer patients, 129 laryngeal cancer patients, and 172 controls, all French Caucasians. Cancer risks and gene-alcohol interactions were analyzed by unconditional logistic regression, accounting for potential confounders. ADH(3) genotype was not associated with UAT cancer. In contrast, a 2-fold risk of oral cavity/pharyngeal (OR = 2.0, 95% CI 1.0-3.9) and laryngeal (OR = 1.8, 95% CI 1.0-3.5) cancers was observed for carriers of the CYP2E1 DraI C variant allele compared with other individuals. The risk associated with the CYP2E1 RsaI c2 variant allele also increased for oral cavity/pharyngeal cancer (OR = 2.6, 95% CI 1.0-6. 6). The effects of ADH(3) or CYP2E1 genotype and alcohol or tobacco were independent. The highest risk of oral cavity/pharyngeal cancer was observed among the heaviest drinkers (>80 g/day) with the CYP2E1 DraI C allele (OR = 5.8, 95% CI 1.9-18.2) or the CYP2E1 RsaI c2 allele (OR = 7.2, 95% CI 1.4-38.2) compared with lighter drinkers with other genotypes. Our study suggests that CYP2E1 genotype modifies the risk of UAT cancers, but due to the low frequency of CYP2E1 variant alleles, large-scale studies are needed to confirm our findings.