Interleukin-22 genetic polymorphisms and risk of colon cancer

Interleukin-22 (IL-22) is a member of the IL-10 family of anti-inflammatory cytokines that mediates epithelial immunity. IL-22 expression is enhanced in inflamed colon mucosa in individuals with inflammatory bowel disease. We carried out an association study to examine the hypothesis that common variation in the IL-22 gene is associated with risk of colon cancer. Seven tagging SNPs were genotyped in 561 colon cancer cases and 722 population controls. Information on lifestyle risk factors was collected via a self-administered questionnaire. The rs1179251 SNP conferred an estimated odds ratio (OR) of 1.46 (95% CI = 1.04-2.05) and 2.10 (95% CI = 0.66-6.66), respectively, for those heterozygous and homozygous for the G variant (p (additive) = 0.013) after adjustment for age, gender, and race; the OR assuming a dominant model was 1.50 (95% CI = 1.05-2.08, p (dominant) = 0.016). No other SNP was statistically significantly associated with colon cancer risk. Haplotype analysis found that one haplotype containing the rs1179251 G allele gave an estimated 52% increase in risk of colon cancer for individuals with at least one copy (OR = 1.52, 95% CI = 1.12-2.06, p = 0.0073). Our findings suggest that the rs1179251 SNP in IL-22 is associated with risk of colon cancer.