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AIM: To investigate the relationship between Helicobacterpylori (H. pylori) infection and the expressions of the p53,Rb, c-myc, bcl-2 and hTERT mRNA in a series of diseasesfrom chronic gastritis (CG), intestinal metaplasia type Ⅰ or Ⅱ(IMⅠ-Ⅱ), intestinal metaplasia type Ⅲ (IMⅢ), mild or modestdysplasia (DysⅠ-Ⅱ), severe dysplasia (DysⅢ) to gastric cancer(GC) and to elucidate the mechanism of gastriccarcinogenesis relating to H.pyloriinfection.METHODS: 272 cases between 1998 and 2001 wereavailable for the study including 42 cases of CG, 46 cases ofIMⅠ-Ⅱ, 25 cases of IMⅢ, 48 cases of DysⅠ-Ⅱ, 27 cases ofDysⅢ, 84 cases of GC.-H. pyloriinfection and the expressionsof p53, Rb, c-myc, bcl-2 were detected by means ofstreptavidin-peroxidase (SP) immunohistochemical method.HTERT mRNA was detected byin situ hybridization(ISH).RESULTS: The expressions of p53, Rb, c-myc, hTERT mRNAand bcl-2 were higher in the GC than in CG, IN, Dys. Theexpression of c-myc was higher in IMⅢ with-H.pyloriinfection(10/16) than that without infection (1/9) and the positive ratein DysⅠ-Ⅱ and DysⅢ with-H.pyloriinfection was 18/30 and 13/17, respectively, higher than that without infection (4/18 and3/10, respectively). In our experiment mutated p53 had noassociation with H.pyloriinfection, theexpression of Rb wasassociated with-H. pyloriinfection in GC, but the p53-Rb tumor-suppressor system abnormal in DysⅠ-Ⅱ cases, DysⅢⅡ and GCcases with H. pyloriinfection was 21/30, 15/17 and 48/48respecively, higher than non-infection groups (4/18, 3/10, 28/36). Furthermore the level of hTERT mRNA in GC with H. pyloriinfection (47/48) was higher than that without infection (30/36), however the relationship between bcl-2 and H. pyloriwasonly in IMⅢ. C-myc had a close association with hTERT mRNAin DysⅢ and GC (P＝0.0 253,0.0 305 respectively).CONCLUSION: In the gastric carcinogenesis, H. pylorimightcause the severe imbalance of proliferation and apoptosisin the precancerous lesions (IMⅢ and GysⅢ) first, leadingto p53-Rb tumor-suppressor system mutation and telomerasereactivation, and finally causes gastric cancer.