AIM:To identify genes potentially involved in Helicobacter pylori(H.pylori)-induced gastric carcinogenesis.METHODS:GES-1 cells were co-cultured with H.pylori strains isolated from patients with gastric carcinoma(GC,n = 10) or chronic gastritis(CG,n = 10) for in vitro proliferation and apoptosis assays to identify the most and least virulent strains.These two strains were cagA-genotyped and used for further in vivo carcinogenic virulence assays by infecting Mongolian gerbils for 52 wk,respectively;a broth free of H.pylori was lavaged as control.Genomic profiles of GES-1 cells cocultured with the most and least virulent strains were determined by microarray analysis.The most differentially expressed genes were further verified using quantitative real-time polymerase chain reaction in GES-1cells infected with the most and least virulent strains,and by immunohistochemistry in H.pylori positive CG,precancerous diseases,and GC biopsy specimens in an independent experiment.RESULTS:GC-derived H.pylori strains induced a potent proliferative effect in GES-1 cells in co-culture,whereas CG-derived strains did not.The most(from a GC patient) and least(from a CG patient) virulent strains were cagA-positive and negative,respectively.At week 52,CG,atrophy,metaplasia,dysplasia,and GC were observed in 90.0%,80.0%,80.0%,90%,and 60.0%,respectively,of the animals lavaged with the most virulent strain.However,only mild CG was observed in 90% of the animals lavaged with the least virulent strain.On microarray analysis,800 differentially expressed genes(49 up-and 751 down-regulated),involving those associated with cell cycle regulation,cell apoptosis,cytoskeleton,immune response,and substance and energy metabolisms,were identified in cells co-cultured with the most virulent strain as compared with those co-cultured with the least virulent strain.The six most differentially expressed genes(with a betweenness centrality of 0.1-0.2) were identified among the significant differential gene profile network,including JUN,KRAS,BRCA1,SMAD2,TRAF1,and HDAC6.Quantitative real-time polymerase chain reaction analyses verified that HDAC6 and TRFA1 mRNA expressions were significantly more up-regulated in GES-1 cells cocultured with the most virulent strain than in those cocultured with the least virulent strain.Immunohistochemistry of gastric mucosal specimens from H.pyloripositive patients with CG,intestinal metaplasia(IM),dysplasia,and GC showed that moderately positive and strongly positive HDAC6 expression was detected in 21.7% of CG patients,30.0% of IM patients,54.5% of dysplasia patients,and 77.8% of GC patients(P < 0.001).The up-regulation of TRAF1 expressions was detected in 34.8%,53.3%,72.7%,and 88.9% specimens of CG,IM,dysplasia,and GC,respectively(P < 0.001).CONCLUSION:The overexpression of HDAC6 and TRAF1 in GES-1 cells co-cultured with the GC-derived strain and in H.pylori-positive dysplasia and GC suggests that HDAC6 and TRAF1 may be involved in H.pyloriinduced gastric carcinogenesis. AIM: To identify genes potentially involved in Helicobacter pylori (H. pylori) -induced gastric carcinogenesis. METHODS: GES-1 cells were co-cultured with H. pylori isolates from patients with gastric carcinoma (GC, n = 10) gastritis (CG, n = 10) for in vitro proliferation and apoptosis assays to identify the most and least virulent strains. these two strains were cagA-genotyped and used for further in vivo carcinogenic virulence assays by infecting Mongolian gerbils for 52 wk, respectively; a broth free of H. pylori was lavaged as control. Genomic profiles of GES-1 cells cocultured with the most and least virulent strains were determined by microarray analysis. most likelyally expressed genes were further verified using quantitative real-time polymerase chain reaction in GES-1 cells infected with the most and least virulent strain, and by immunohistochemistry in H. pylori positive CG, precancerous diseases, and GC biopsy specimens in an independent experiment .RESULTS: GC-derived H. pylori induced a potent proliferative effect in GES-1 cells in co-culture, whereas CG-derived strains did not. The most (from a GC patient) and least (from a CG patient) virulent strains were cagA-positive and negative, respectively. At week 52, CG, atrophy, metaplasia, dysplasia, and GC were observed in 90.0%, 80.0%, 80.0%, 90%, and 60.0%, respectively, of the animals lavaged with the most virulent strain. , only mild CG was observed in 90% of the animals lavaged with the least virulent strain. On microarray analysis, 800 differentially expressed genes (49 up-and 751 down-regulated), involving those associated with cell cycle regulation, cell apoptosis, cytoskeleton , immune response, and substance and energy metabolisms, were identified in cells co-cultured with the most virulent strain as compared with those co-cultured with the least virulent strain. the six most differentially expressed genes (with a betweenness centrality of 0.1-0.2 ) were identified among the significant differential gene profile network, including JUN, KRAS, BRCA1, SMAD2, TRAF1, and HDAC6.Quantitative real-time polymerase chain reaction analyzes verified that HDAC6 and TRFA1 mRNA expressions were significantly more up-regulated in GES-1 cells cocultured with the most virulent strain than in those cocultured with the least virulent strain. Immunohistochemistry of gastric mucosal specimens from H. pyloripositive patients with CG, intestinal metaplasia (IM), dysplasia, and GC showed that moderately positive and strongly positive HDAC6 expression was detected in 21.7% of CG patients, 30.0% of IM patients, 54.5% of dysplasia patients, and 77.8% of GC patients (P <0.001). The up-regulation of TRAF1 expressions was detected in 34.8%, 53.3%, 72.7%, and 88.9% specimens of CG, CONCLUSION: The overexpression of HDAC6 and TRAF1 in GES-1 cells co-cultured with the GC-derived strain and in H. pylori-positive dysplasia and GC suggests that HDAC6 and TRAF1 may be involved in H. pylori induced gastric c arcinogenesis.