Alcohol is an important risk factor for upper aerodigestive cancers and is principally metabolized by alcohol dehydrogenase (ADH) enzymes. We have investigated six ADH genetic variants in over 3,800 aerodigestive cancer cases and 5,200 controls from three individual studies. Gene variants rs1229984 (ADH1B) and rs1573496 (ADH7) were significantly protective against aerodigestive cancer in each individual study and overall (P ¼ 10 À10 and 10 À9 , respectively). These effects became more apparent with increasing alcohol consumption (P for trend ¼ 0.0002 and 0.065, respectively). Both gene effects were independent of each other, implying that multiple ADH genes may be involved in upper aerodigestive cancer etiology.The alcohol dehydrogenase (ADH) pathway includes seven distinct ADH genes, a key candidate gene group for aerodigestive cancers 1-3 .Studies of aerodigestive cancer in populations of European origin have focused on ADH1C with little evidence of any effect 4 . We previously reported an association for ADH1B R48H (rs1229984) in a central European (CE) population 5 and now consider the effect of this and five other ADH variants in an expanded study comprising 809 aerodigestive cancer cases and 2,586 controls from the CE study as well as a further 3,067 aerodigestive cancer cases and 2,692 controls from two other studies in Europe (ARCAGE study) and Latin America (LA study) (total of 3,876 cases and 5,278 controls). All three studies were coordinated by the International Agency for Research on Cancer (IARC) and followed a similar protocol (Supplementary Methods online). Of the 3,876 cases, 1,790 were cancers of the oral cavity or pharynx, 1,659 were cancers of the hypopharynx or larynx and 427 were cancers of the esophagus (Supplementary Table 1 online). Cases with a histology other than squamous cell were excluded.The HapMap Consortium has genotyped 163 SNPs in the vicinity of the ADH gene cluster with a minor allele frequency (MAF) of 4% or more in the CEPH Utah (CEU) population 6 . Inspection of the linkage disequilibrium (LD) pattern across this region indicates that ADH1A, ADH1B, ADH1C, ADH4, ADH5 and ADH6 are relatively highly correlated, whereas ADH7 showed little correlation with the remaining six ( Supplementary Fig. 1a online). From all verified missense SNPs in the seven ADH genes found in both the NCBI SNP and SNP500 databases 7 , we selected eight that had a MAF 4 4% in the CEU population. Three missense SNPs in ADH4 (rs1126671, rs1126673 and rs1042364) were in strong LD, and thus were genotyped by the highly correlated tagging SNP rs1984362 (r 2 4 0.89). In total, we genotyped six genetic variants (five missense SNPs and one tagging SNP) in all three studies (Table 1 and Supplementary Table 2 online).In the pooled analysis on all 3,876 cases and 5,278 controls, four variants reported a significant association (Supplementary Table 3 online). The most prominent was with rs1229984 (in ADH1B; OR for codominant model ¼ 0.59 (95% CI ¼ 0.50-0.69); P under codominant model ¼ 8 Â 10 À10 ). This variant w...

Trichloroethylene (TCE) is a suspected renal carcinogen. TCE-associated renal genotoxicity occurs predominantly through glutathione S-transferase (GST) conjugation and bioactivation by renal cysteine β-lyase (CCBL1). We conducted a case-control study in Central Europe (1,097 cases and 1,476 controls) specifically designed to assess risk associated with occupational exposure to TCE through analysis of detailed job histories. All jobs were coded for organic/chlorinated solvent and TCE exposure (ever/never) as well as the frequency and intensity of exposure based on detailed occupational questionnaires, specialized questionnaires, and expert assessments. Increased risk was observed among subjects ever TCE exposed [odds ratio (OR) = 1.63; 95% confidence interval (95% CI), 1.04-2.54]. Exposure-response trends were observed among subjects above and below the median exposure [average intensity (OR = 1.38; 95% CI, 0.81-2.35; OR = 2.34; 95% CI, 1.05-5.21; P trend = 0.02)]. A significant association was found among TCE-exposed subjects with at least one intact GSTT1 allele (active genotype; OR = 1.88; 95% CI, 1.06-3.33) but not among subjects with two deleted alleles (null genotype; OR = 0.93; 95% CI, 0.35-2.44; P interaction = 0.18). Similar associations for all exposure metrics including average intensity were observed among GSTT1-active subjects (OR = 1.56; 95% CI, 0.79-3.10; OR = 2.77; 95% CI, 1.01-7.58; P trend = 0.02) but not among GSTT1 nulls (OR = 0.81; 95% CI, 0.24-2.72; OR = 1.16; 95% CI, 0.27-5.04; P trend = 1.00; P interaction = 0.34). Further evidence of heterogeneity was seen among TCE-exposed subjects with ≥1 minor allele of several CCBL1-tagging single nucleotide polymorphisms: rs2293968, rs2280841, rs2259043, and rs941960. These findings provide the strongest evidence to date that TCE exposure is associated with increased renal cancer risk, particularly among individuals carrying polymorphisms in genes that are important in the reductive metabolism of this chemical, and provides biological plausibility of the association in humans.