Association of EC-SOD, CYP1A1 gene polymorphisms, and smoking with oral cancer

We explored the correlation between smoking, polymorphisms of extracellular superoxide dismutase (ECSOD) and cytochrome P450 (CYP) 1A1-Msp I and the prevalence of oral cancer. The genetic polymorphisms of EC SOD and CYP1A1-Msp I were detected by polymerase chain reaction (PCR) technique in peripheral blood leukocytes of 874 oral cancer patients and 874 non-cancer controls, and the correlations between smoking, genetic polymorphisms of the two metabolic enzymes and oral cancer were analyzed. The frequencies of EC-SOD (C/G) and CYP1A1-Msp I mutation homozygous genotype (m2/m2) were 37.87% and 63.62%, respectively, in the oral cancer patients, and 26.54% and 46.45%, respectively, in the healthy controls, both indicating significant differences (P<0.05). The risk of oral cancer was significantly higher in individuals with EC-SOD (C/G) than that in the controls (OR=2.68, 95% CI=1.46-5.17). The individuals carrying CYP1A1-Msp I (m2/m2) also had a higher risk of oral cancer (OR=2.35, 95% CI=1.63-4.92). The synergetic analysis of gene mutation indicated that the distribution frequency of EC-SOD (C/G)/CYP1A1-Msp I (m2/m2) was 26.66% in the case group and 3.43% in the control group. The difference was statistically significant (P<0.05). The individuals carrying EC-SOD (C/G)/CYP1A1-Msp I (m2/m2) had a higher risk of oral cancer (OR=5.46, 95% CI=2.73-8.94). The smoking rate in the case group was significantly higher than that in the control group (P<0.05), and statistic analysis indicated a synergetic interaction between smoking and EC-SOD (C/G)/CYP1A1-Msp I (m2/m2) genotype polymorphisms, which increased the risk of oral cancer (OR=42.11, 95% CI=16.71-63.29). Smoking index (SI) higher than 400 and EC-SOD (C/G)/CYP1A1-Msp I (m2/m2) genotype polymorphisms synergistically increased the risk of oral cancer (OR=246.32, 95% CI=176.23-386.14). EC-SOD (C/G) and CYP1A1-Msp I (m2/m2) were the risk factors for oral cancer. Smoking was also correlated with the susceptibility to oral cancer. EC-SOD (C/G)/CYP1A1-Msp I (m2/m2) and smoking were working synergistically in elevating the incidence of oral cancer.