Abstract: ObjectiveTo observe the effects of a cagA-deleted mutant strain of Chinese H.pylori on the phenotypes, proliferation and apoptosis in human gastric cancer cell line BGC823 in vitro,and to determine the cytotoxicity of cagA,one of the virulence gene of H.pylori.MethodsBGC 823 cells were co-cultured with the wild type H.pylori and the isogenous mutant,which were called the wild tue strain group and the mutant stain group,respectively.The cell phenotype was observed at 6,12,24 and 48h and the cellular proliferation was examined by methyl thiazolyl tetrazo lium(MTT)method.The induction of apoptosis was determined by flow cytometry.ResultsThe chang es of cell morphology were observed when BGC823 cells were co-cultured with H.pylori for 6 hours,and cell scatterring and hummingbird morphology(cell elongation)were presented after co-cultured for 48 hours in both groups.The MTT assay showed that the viability of BGC823 cells was inhibited in the wild type strain group,while was significanthigherin the mutant strain group than that of the control group and the wild type strain group when co-cultured with H.pylori for 24 and 48 hours,respectively.As demonstrated by flow cytometry,the apoptotic rate in both the wild type and the mutant group was higher than that of control group(P<0.05), but there was no difference between the two groups treated with H.pylori.ConclusionsCell scatterring and hummingbird phenotype(cell elongation)were not the cell morphology characteristics specific related to the cagA gene after treated with H.pylori;The cagA gene may play the crucial role in H.pylori's actions of inhibiting cellular proliferation;The cagA gene may have the only limited effects on the cellular apoptosis induced by H.pylori.