Microsomal epoxide hydrolase polymorphisms, cigarette smoking and prostate cancer risk in the Slovak population

Polymorphisms in tobacco carcinogen metabolizing enzymes may generate interindividual variations towards the risk of developing prostate cancer. One of these enzymes is microsomal epoxide hydrolase (EPHX1) which metabolizes polycyclic aromatic hydrocarbons, or PAH, carcinogens found in cigarette smoke. The activity of this enzyme is affected by two polymorphisms, a substitution of Tyr113 by His in exon 3 and a substitution of His139 by Arg in exon 4. The aim of this study was to use a population-based case-control study to investigate whether or not such genetic polymorphisms in EPHX1 gene can modify the relationship between smoking status and the risk of developing prostate cancer. We used restriction fragment length polymorphism, or PCR-RFLP to determine EPHX1 genotypes in subjects comprising 194 patients with histologically verified prostate cancer and 305 healthy individuals as control. We found no overall association between prostate cancer risk and functional polymorphisms of EPHX1 gene in exon 3 and exon 4. We further analysed the association between the EPHX1 genotypes and smoking. Smokers carrying the exon 3 Tyr/Tyr and Tyr/His genotypes were at no significant risk compared to non-smokers with the rapid Tyr/Tyr genotype. By contrast, a significant interaction of smoking and the exon 4 polymorphism was present (p < 0.05). Excess statistically significant risk was apparent among smokers with imputed normal phenotype in comparison to non-smokers with normal phenotype (p < 0.01). Based on these results we conclude that in the Slovak population studied, EPHX1 gene polymorphism in exon 4 would alter the risk of prostate cancer, particularly among smokers. Further analysis of other polymorphic variants in biotransformation enzymes and evaluation of gene-gene interactions may provide a more complete picture of how EPHX1 might influence the risk of developing prostate cancer.