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To study Helicobacter pylori (H. pylori) infection in relation to E-cadherin (E-cad) promoter polymorphism and hypermethylation in GCs.Specimens were taken from representative cancerous lesions and adjacent non-cancerous epithelia of 67 resected GCs. H. pylori was detected by real-time PCR of the cagA gene from non-neoplastic epithelium. E-cad promoter polymorphism and hypermethylation were determined by restriction fragment length polymorphism analysis and methylation-specific PCR, respectively. Expression of E-cad protein was determined by immunohistochemistry.H. pylori was found in 57% of patients with GC. H. pylori infection was more frequently found in tumors with the -160C/C genotype than those with the -160C/A and -160A/A genotypes (74% vs 47%, P = 0.02). H. pylori infection was associated with E-cad methylation in non-neoplastic epithelium; however, no significant difference in H. pylori was observed between methylated and unmethylated cancerous lesions.Patients with the -160C/C genotype might require H. pylori infection to promote the inactivation of CDH1, suggesting that H. pylori infection might affect GC in an initial stage because polymorphism is germ line. Mechanism of hypermethylation of CDH1 promoter in GC is complex, and H. pylori infection might affect it in an initial stage.

AIM: To study the role of CDH1/E-cadherin (E-cad) gene alteration profiles including mutation, loss of heterozygosity (LOH), promoter polymorphism and hypermethylation in mechanisms of CDH1 inactivation in gastric carcinoma (GC). METHODS: Specimens were collected surgically from 70 patients with GC. Allelotyping PCR and detection of LOH, denaturing high pressure liquid chromatography and DNA sequencing, restriction fragment length polymorphism analysis, methylation specific PCR, and immunohistochemical staining were used. RESULTS: Promoter polymorphism was not a major mechanism of E-cad inactivation. Only one truncating mutation was found in a diffuse type tumor (3%). Both LOH and promoter hypermethylation were major mechanisms of E-cad inactivation, but interestingly, there was a negative association between the fraction of allelic loss (LOH) in tumors and hypermethylation of CDH1. Therefore LOH and hypermethylation were two different tumorigenic pathways involved in GC. CONCLUSION: Given the findings that somatic mutation was extremely low and the relationship between LOH and hypermethylation was inverse, any two combinations of these three factors cannot fulfill the classical two-hit hypothesis of CDH1 inactivation. Thus, other mechanisms operating at the transcriptional level or at the post-translational level might be required to induce E-cadherin inactivation.