A Common Promoter Polymorphism (-23HphI) in Insulin Gene and Susceptibility to Colorectal Cancer

Background: With regard to the major role of insulin resistance in colorectal cancer (CRC), this study investigated whether insulin (INS) gene -23HphI variant was associated with susceptibility to CRC risk. Methods: Our study was conducted as a case-control study and 312 cases with CRC and 438 controls were enrolled. All 750 subjects were genotyped for INS gene -23HphI variant using PCR-RFLP method. Results: There was no significant difference for the -23HphI variant of INS gene in either genotype or allele frequencies between the cases and the controls and this lack of difference remained non-significant even after adjustment for age, BMI, sex, smoking status, regular NSAID use, and family history of CRC. No evidence for the effect modification of the association -23HphI variant and CRC by BMI, sex, or tumor site was also observed. Moreover, the risk of obesity in relation to the -23HphI variant in the controls and the cases was separately analyzed and we observed no significant difference between normal weight (BMI 25 kg/m2) and overweight/obese (BMI ≥ 25 kg/m2) subjects. Conclusions: These findings do not support the plausible effect of the INS gene -23HphI variant on CRC risk; nonetheless, our finding requires confirmation and the role of the gene variant in carcinogenesis needs to be further evaluated.