LARYNX CANCER RISK IN RELATION TO GLUTATHIONE-S-TRANSFERASE M1 AND T1GENOTYPES AND TOBACCO SMOKING

Glutathione S-transferase (GST) isoenzymes are involved in the detoxif ication of several tobacco smoke-derived carcinogens, It is thus conce ivable that deficiency in GST activity due to homozygous deletion of t he GSTM1 and GSTT1 genes (the null genotypes) may modulate susceptibil ity to smoking-induced cancers, The effects of the GSTM1 and GSTT1 nul l genotypes on laryngeal cancer risk were evaluated using peripheral b lood DNA from 129 larynx cancer patients and 172 noncancer controls, a ll of whom were regular smokers, Increased larynx cancer risk was rela ted to the GSTM1 null genotype [odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.0-2.8], The OR associated with the GSTT1 null genoty pe was increased, although not significantly (OR = 1.4, 95% CI = 0.7-2 .9), Individuals with concurrent lack of GSTM1 and GSTT1 genes had a d oubled, although not significant, risk for larynx cancer when compared with those having at least one of these genes (OR = 2.0, 95% CI = 0.8 -5.2) and had almost a 3-fold risk (OR = 2.7, 95% CI = 1.0-7.4) when c ompared with those with both genes, Moreover, a significant interactio n between the GSTM1 genotype and levels of tobacco consumption (P < 0. 05) was found; the GSTM1 null genotype was associated with an increase d risk of larynx cancer among smokers of 20 g/day or less (OR = 2.9, 9 5% CI = 1.3-6.3) but not among heavier smokers (OR = 1.0; 95% CI = 0.5 -2.0), In contrast, the GSTT1 null genotype posed an increased, althou gh not significant, risk among long-term smokers (OR = 2.3, 95% CI = 0 .9-5.4).