Abstract: ObjectiveTo screen and identify the cancer-related proteins in host cells with relation to cagA gene of Helicobacter pylori(H pylori).MethodsGastric epithelium cell line Ges-1 cells were co-cultured with the wild-type strains Hp 27 and the isogenic cagA-deleted mutants Hp 27△cagA at a ratio of 100:1 for the bacteria and the cells in culture medium for 10 hr.Total cellular proteins of two groups were extracted with Sonication-Urea-CHAPS-DTT method and the protein concentration was measured with Bradford's method.The soluble proteins of two groups were separated firstly by isoelectric focusing(IEF)electrophoresis and then by SDS-PAGE to obtain 2-DE maps,which were digitalized and analysed to search the protein spots of differential expression.Spots of interest were cut out and subjected to in-gel digestion.Then the peptide mass finger-printer(PMF)was obtained with matrix assisted laser adsorption ionization time of flight mass spectrometry (MALDI-TOF-MS).Then the biology information was used to search protein database of these PMF and to identify the proteins,and analyze the biological significance and function of the proteins.ResultsFour protein spots of differential expression,which were high abundance in the cellular proteins of wild-type strain group and were down-regulated or absently expressed in the proteins of mutant group,were selected and identified.The identified proteins were triosephosphate isomerase, annexin A1 and a-enolase,which were reported to have close relationship with the pathophysiological processes of many kinds of cancers.ConclusionThree tumor marker proteins of triosephosphate isomerase,a-enolase and annexin A1 are associated with cagA gene of H pylori.The result suggests that the cagA gene is involved in the carcinogenesis of H pylori.