Frequent CpG island methylation in sporadic and syndromic gastric fundic gland polyps

We studied methylation of 2 tumor suppressor genes (p14, p16) and 4 MINT (methylated in tumor) clones (MINT1, MINT2, MINT25, MINT31) among 51 fundic gland polyps (FGPs) and 27 normal gastric body biopsy samples using bisulfite treatment of genomic DNA followed by methylation-specific polymerase chain reaction. Thirty-two FGPs were syndromic polyps from 14 patients with familial adenomatous polyposis (FAP); 19 were sporadic FGPs from 15 patients without FAP. Significantly higher mean methylation indices were found between FGPs and normal gastric mucosa (P = .012). FGPs arising in a background of proton pump inhibitor (PPI) effect had significantly higher mean methylation indices than those that did not (P = .023). Perhaps because sporadic FGPs were more likely to be associated with PPI effect than were FAP-associated FGPs, they also demonstrated higher mean methylation indices than syndromic polyps (P = .024). Among FAP-associated FGPs, there was no statistical difference in methylation indices between polyps that were dysplastic, indefinite for dysplasia, or nondysplastic (P = .87). Epigenetic alterations involving methylation of CpG islands might have a role in the development of some FGPs, particularly those with a PPI effect. They do not account for the presence or absence of a dysplastic phenotype in FGPs.