AIM: To elucidate the sequential gene expression profile in AGS cells co-cultured with wild-type Hellcobacter pylori (Hpylon) as a model of H pylori-infected gastric epithelium, and to further examine the contribution of cag-pathogenicity islands (cagPAI)-coding type Ⅳ secretion system and the two pathways, nuclear factor kappa B (NF-κB) and extracellular signal-regulated kinases (ERK) on wild-type H pylori-induced gene expression. METHODS: Gene expression profiles induced by H pylori were evaluated in AGS gastric epithelial cells using cDNA microarray, which were present in the 4 600 independent clones picked up from the human gastric tissue. We also analyzed the contribution of NF-κB and ERK signaling on H pylori-induced gene expression by using inhibitors of specific signal pathways. The isogenic mutant with disrupted capE (△cagE) was used to elucidate the role of capPAI-encoding type Ⅳ secretion system in the gene expression profile. RESULTS: According to the expression profile, the genes were classified into four clusters. Among them, the clusters characterized by continuous upregulation were most conspicuous, and it contained many signal transducer activity-associated genes. The role of cagPAI on cultured cells was also investigated using isogenic mutant cagE, which carries non-functional cagPAI. Then the upregulation of more than 80% of the induced genes (476/566) was found to depend on cagPAI. Signal transducer pathway through NF-κB or ERK are the major pathways which are known to be activated by cagPAI-positive H pylori. The role of these pathways in the whole signal activation by cagPAI- positive H pylori was analyzed. The specific inhibitors against NF-κB or ERK pathway blocked the activation of gene expression in 65% (367/566) or 76% (429/566) of the genes whose activation appealed to depend on cagPAI. CONCLUSION: These results suggest that more than half of the genes induced by cagPAI-positive H pylori depend on NF-κB and ERK signaling activation, and these pathways may play a role in the gene expression induced by host-bacterial interaction which may associate with H pylori-related gastro-duodenal diseases. AIM: To elucidate the sequential gene expression profile in AGS cells co-cultured with wild-type Hellcobacter pylori (Hpylon) as a model of H pylori-infected gastric epithelium, and to further examine the contribution of cag-pathogenicity islands (cagPAI) - coding type IV secretion system and the two pathways, nuclear factor kappa B (NF-κB) and extracellular signal-regulated kinases (ERK) on wild-type H pylori-induced gene expression. METHODS: Gene expression profiles induced by H pylori were evaluated as in AGS gastric epithelial cells using cDNA microarray, which were present in the 4 600 independent clones picked up from the human gastric tissue. We also analyze the contribution of NF-κB and ERK signaling on H pylori-induced gene expression by using inhibitors of specific signal pathways. The isogenic mutant with disrupted capE (ΔcagE) was used to elucidate the role of capPAI-encoding type Ⅳ secretion system in the gene expression profile. RESULTS: According to the expression pro The genes of cagPAI on cultured cells were also investigated using isogenic mutant cagE, which Then the upregulation of more than 80% of the induced genes (476/566) was found to depend on cagPAI. Signal transducer pathway through NF-κB or ERK are the major pathways which are known to be activated by The role of these pathways in the whole signal activation by cagPAI-positive H pylori was analyzed. The specific inhibitors against NF-κB or ERK pathway blocked the activation of gene expression in 65% (367/566) or 76% (429/566) of the genes whose activation appealed to depend on cagPAI. CONCLUSION: These results suggest that more than half of the genes induced by cagPAI-positive H pylori depend on NF-κB and ERK signaling activa tion, and tthese pathways may play a role in the gene expression induced by host-bacterial interaction which may associate with H pylori-related gastroduodenal diseases.