Background and aim: Microsomal epoxide hydrolase 1 (EPHX1) is involved in the metabolism of environmental and tobacco carcinogens. Tobacco smoking, betel quid chewing, and alcohol consumption are the major known risk factors for esophageal cancer. The present case-control study evaluated the influence of EPHX1 genetic variations on esophageal cancer susceptibility in 142 patients and 185 healthy controls from a high-incidence region of India where tobacco use and alcohol consumption are widespread and the users of these two substances are also betel quid chewers.
Methods: EPHX1 polymorphic alleles (exon 3, Tyr113His and exon 4, His139Arg) were genotyped by polymerase chain reaction-restriction fragment length polymorphism method and direct sequencing. The results were analyzed using logistic regression to calculate odds ratios (OR) and confidence intervals (CI).
Results: Patients with exon 4 genotypes (139His/Arg, 139Arg/Arg) and the 139Arg allele were significantly associated with a risk of esophageal cancer (OR(His139Arg) 1.887, 95% CI = 1.112-3.201, P = 0.019; OR(Arg139Arg) 7.140, 95% CI = 1.276-393.953, P = 0.025 and OR(Arg) 1.83, 95% CI = 1.19-2.82, P = 0.003). The 139His/Arg genotype was a significant risk factor for esophageal cancer in tobacco chewers and betel quid chewers. Patients with the 139Arg/Arg genotype were at significantly higher risk for developing a well-differentiated and moderately-differentiated grade of tumor. In contrast, the 113His/His genotype of exon 3 was a significant protective factor for esophageal cancer in tobacco smokers (OR 0.291, 95% CI = 0.138-0.616, P = 0.001), betel quid chewers (OR 0.434, 95% CI = 0.236-0.797, P = 0.007), and alcohol users.
Conclusion: EPHX1 exon 4 139His/Arg, and 139Arg/Arg genotypes were associated with a higher risk of esophageal cancer in a high-risk area of India.