NAD(P)H : quinone oxidoreductase-dependent risk for colorectal cancer and its association with the presence of K-ras mutations in tumors

NAD(P)H:quinone oxidoreductase (NQO1) is a polymorphic enzyme involved in t he detoxification of potentially mutagenic and carcinogenic quinones, The h omozygous C609T NQO1 genotype resulting in loss of reductase activity is fo und in 2-20% of individuals. In the present study, the NQO1-dependent risk for sporadic colorectal cancer (CRC) was studied in 247 incident CRC cases and 296 hospital-based controls recruited during 1996-1997, Four subgroups of cases were studied: (i) all CRCs; (ii) a molecular CRC subgroup (n = 117 , cases with molecular tumor analyses); (iii) within the molecular subgroup those tumors with K-ras mutations in codon 12 (CRC K12); (iv) within the m olecular subgroup those tumors with K-ras mutations in codon 13 (CRC K13), The C609T NQO1 genotype was found to be twice as prevalent in all CRC patie nts (6.8%) compared with controls (3%) and six times more common in the sub set CRC K12 (20%), Multivariant analyses in the overall population of 247 c ases and 296 controls showed a significant age and gender adjusted risk for CRC associated with the C609T NQO1 genotype (OR 2.9, 95% CI 1.19-6.97; P = 0.01) or with any variant genotype (the low activity allele frequency, i,e , heterozygotes plus homozygotes) (OR 1.41, 95% CI 1.02-1.92; P = 0.03). Wi thin cases of the molecular subgroup (n = 117) the C609T NQO1 genotype was associated with the presence of K-ras codon 12 mutation (OR 6.5 95%, CI 1.3 9-34.9; P = 0.003). Logistic: regression showed an age and gender adjusted risk for K-ras codon 12 mutant CRC associated with the C609T NQO1 genotype (OR 10.5, 95% CI 2.99-36.7; P = 0.0002) or with any variant NQO1 genotype ( OR 2.23, 95% CI 1.23-4.00; P = 0.007) compared with the control group. Gene tically determined variations in NQO1 may modify the risk for CRC and these risks may be greatest for tumors containing K-ras codon 12 mutations. CRC with K-ras codon 12 mutations may represent a distinct and etiologically mo re homogeneous subtype of the disease, which may be associated with toxican ts that are metabolized via a NQO1-dependent pathway.