E-cadherin gene promoter hypermethylation in primary human gastric carcinomas

Background: E (epithelial)-cadherin, the cell adhesion molecule also consid ered a potential invasion/metastasis suppressor, is mutationally inactivate d in nearly half of all undifferentiated-scattered (diffuse-type) gastric c arcinomas. In addition, silencing of E-cadherin by CpG methylation within i ts promoter region has been reported in several gastric carcinoma cell line s. We investigated the methylation status of the E-cadherin promoter region in 53 primary human gastric carcinomas. Methods: Hypermethylation of the E -cadherin promoter was determined by utilizing methylation-specific polymer ase chain reaction (PCR)-single-strand conformation polymorphism (MSP-SSCP) analysis followed by direct sequencing of PCR products. Expression of E-ca dherin was studied by western blot analysis. All statistical tests were two -sided. Results: Hypermethylation of the E-cadherin promoter was evident in 27 (51%) of 53 primary gastric carcinomas examined by MSP-SSCP. It occurre d more frequently in carcinomas of the undifferentiated-scattered type (in 15 [83%] of 18) than in other histologic subtypes (in 12 [34%] of 35) (P = .0011, Fisher's exact test), and it was present at similar rates in early ( in six [60%] of 10) versus advanced (in 21 [49%] of 43) carcinomas (P = .73 , Fisher's exact test). Methylation occurring at all cytosine-guanosine seq uences (CpGs) near the transcriptional start site was confirmed in six of s ix tumors examined by bisulfite-DNA sequencing, including two early gastric carcinomas. In addition, loss or diminished expression of E-cadherin was c onfirmed by western blotting in four of the six tumor tissues demonstrating hypermethylation. Conclusions: The E-cadherin promoter frequently undergoe s hypermethylation in human gastric cancers, particularly those of the undi fferentiated-scattered histologic subtype. E-cadherin promoter hypermethyla tion is associated with decreased expression and may occur early in gastric carcinogenesis.