Effect of polymorphisms of IL-17A, -17F and MIF genes on CpG island hyper-methylation (CIHM) in the human gastric mucosa.

CpG island hyper-methylation (CIHM) is one of the major events in the gastric carcinogenesis and also occurs in non-neoplastic gastric mucosa. IL-17A, -17F and MIF have a crucial role in the gastric inflammation and carcinogenesis. The CIHM status in the non-cancerous gastric mucosa, in relation to IL-17A (-197G>A, rs2275913), -17F (7488T>C, rs763780) and MIF (-173G>C and -794 tetranucleotide repeats) polymorphisms was investigated. Gastric mucosa samples were obtained from 121 cancer free subjects. CIHM of p14, p16, DAP-kinase and CDH1 genes were determined by methylation-specific polymerase chain reaction (MSP). CIHM high was defined as three or all CpG islands methylated. We employed the PCR-SSCP (multiplex PCR for IL-17A and -17F) method to detect the gene polymorphisms. No association were found between CIHM status and L-17A (-197G>A), IL-17F (7488T>C) and MIF (-173G>C) polymorphisms. MIF 5-CATT repeat carrier (5/5+5/6+5/7) held a significantly higher risk of CIHM of DAP-kinase (OR=2.33, 95% CI=1.07-5.09, p=0.03) and CIHM high (OR=3.63, 95% CI=1.31-10.08, p=0.01). Weak association was also found between the same genotype and increased risk of CIHM of p16 (OR=2.45, 95% CI=0.90-6.68, p=0.08) and CDH1 (OR=2.23, 95% CI=0.94-5.32, p=0.07). 6-CATT repeat carrier (5/6+6/6+6/7) was significantly associated with reduced risk of CIHM of p16 (OR=0.31, 95% CI=0.11-0.90, p=0.03), CDH1 (OR=0.40, 95% CI=0.17-0.98, p=0.045), DAP-kinase (OR=0.37, 95% CI=0.17-0.83, p=0.02) and CIHM high (OR=0.25, 95% CI=0.09-0.74, p=0.01). -7-CATT repeat carrier (6/7+7/7) was weakly associated with reduced risk of CIHM of p16 (OR=0.34, 95% CI=0.10-1.13, p=0.08), DAP-kinase (OR=0.43, 95% CI=0.17-1.06, p=0.07) and CIHM high (OR=0.38, 95%CI=0.12-1.20, p=0.098). The present results provided the first evidence that the genetic polymorphisms MIF polymorphism is associated with CIHM status in the human gastric mucosa. Genetic polymorphisms of MIF-794-CATT repeat may be involved in methylation related carcinogenesis in the stomach.