Abstract: Abstract:Objective To investigate the effects and mechanism of Helicobacter pylori (Hp) infection and methylation of p16 gene in gastric carcinoma development. Methods The hypermethylation of p16 gene was detected by methylation specific polymerase chain reaction (MSP) in 75 cases of different gastric tissues, while the Hp infection was detected by boric acid methylene blue. Results Nineteen cases with hypermethylation of the p16 gene were found from 75 cases of different gastric tissues(25.3%),Among the 19 cases with hypermethylation of the p16 gene,2 cases were from atrophic gastritis tissues (11.1%), 4 cases from severe dysplasia tissues (23.5%) and 13 cases from gastric carcinoma tissues(43.3%),respectively. No cases with hypormethylation of the p16 gene were foud in chronic superficial gastric and light-moderate dysplasia.The ratio of methylation in dysplasia and gastric cancer group was significantly higher than that in the superficial gastritis group(P<0.05). The positive rate of Hp infection was 56% in 75 cases of different gastric tissues (42/75).Among the cases with Hp infection,2 cases were from chronic superficial gastritis(20%),12 cases from atrophic gastritis(66.7%), 12 cases from dysplasia (70.6%)and 16 cases from gastric carcinoma(53.3%), respectively. Positive rate of Hp infection in atrophic gastritis and dysplasia was significantly higher than in superficial gastritis(P<0.05). Sixteen cases with hypermethylation of the p16 gene were found.Forty-two cases of Hp infected gastric tissues (38.1%),while only 3 cases with hypermethylation of the p16 gene were found in 33 cases of Hp uninfected gastric tissues. There are obvious correlation between p16 gene methylation and Hp infection (P<0.05). Conclusion Hp infection and aberrant methylation of p16 gene might play an important role in the pathogenesis of gastric carcinoma. Hp infection might contribute to the increase of aberrant methylation of p16 gene.