Helicobacter pylori CagA-dependent macrophage migration inhibitory factor produced by gastric epithelial cells binds to CD74 and stimulates procarcinogenic events

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that has recently been implicated in carcinogenesis. Helicobacter pylori, which is closely linked to gastric cancer, induces the gastric epithelium to produce proinflammatory cytokines, including MIF. MIF can bind to CD74, which we have previously shown to be highly expressed on the surface of gastric epithelial cells (GEC) during H. pylori infection. In this study, we sought to investigate the role of the H. pylori-induced MIF on epithelial proliferation and procarcinogenic events. Upon establishing a role for the H. pylori CagA virulence factor in MIF production, MIF binding to CD74 on GEC was confirmed. rMIF and H. pylori were shown to increase GEC proliferation, which was decreased when cagA- strains were used and when CD74 was blocked by mAbs. Apoptosis was also decreased by MIF, but increased by cagA- strains that induced much lower amounts of MIF than the wild-type bacteria. Furthermore, MIF binding to CD74 was also shown to decrease p53 phosphorylation and up-regulate Bcl-2 expression. This data describes a novel system in which an H. pylori virulence factor contributes to the production of a host factor that in turn up-regulates procarcinogenic events by the gastric epithelium.     

Helicobacter pylori stimulates epithelial cell migration via CagA-mediated perturbation of host cell signaling

Helicobacter pylori CagA is delivered into gastric epithelial cells, where undergoes tyrosine phosphorylation at the Glu-Pro-Ile-Tyr-Ala (EPIYA) motif to interact with Src homology 2-containing protein tyrosine phosphatase-2 (SHP2) oncoprotein. CagA also binds to partitioning-defective 1 (PAR1) polarity-regulating kinase via the CagA multimerization (CM) sequence. To investigate pathophysiological role of CagA-SHP2 and/or CagA-PAR1 interaction in H. pylori infection, we generated H. pylori isogenic strains producing a phosphorylation-resistant CagA and a CagA without CM sequence. Infection studies revealed that deregulation of epithelial cell motility was more prominent in the wild-type strain than in the mutant strains. Thus, both CagA-SHP2 and CagA-PAR1 interactions are involved in the pathogenicity of cagA-positive H. pylori.     

Helicobacter pylori encoding the pathogenicity island activates matrix metalloproteinase 1 in gastric epithelial cells via JNK and ERK

Helicobacter pylori colonizes the human gastric epithelium and induces an inflammatory response that is a trigger for gastric carcinogenesis. Matrix metalloproteinases (MMPs) have recently been shown to be up-regulated in gastric epithelial cells infected with H. pylori and might contribute to the pathogenesis of peptic ulcer. The aim of this study was to extend the knowledge about the effect of H. pylori infection on MMP-1 expression by gastric epithelial cells, the kinetics of induction, the pathogenetic properties of the bacterium, and the intracellular signaling pathways required for MMP-1 up-regulation. Expression of MMP-1 was induced more than 10-fold by co-culture of AGS+cells with H. pylori strains carrying the pathogenicity island (PAI). H. pylori strains with mutations in the PAI and a defective type IV secretion system had no effect on MMP-1. Double immunofluorescence revealed strong MMP-1 staining in epithelial cells of gastric biopsies at sites of bacterial attachment. In vitro, MMP-1 is up-regulated by interleukin-1beta and tumor necrosis factor-alpha, but these regulatory mechanisms are not operating in H. pylori infection as shown by inhibitory antibodies. Specific inhibitors of JNK kinase and ERK1/2 kinase were found to suppress the H. pylori-induced MMP-1 expression and activity. AGS cells treated with antisense MMP-1 showed a significantly reduced potential to degrade reconstituted basement membrane. Our results suggest that in gastric epithelial cells, H. pylori up-regulates MMP-1 in a type IV secretion system-dependent manner via JNK and ERK1/2. Induction of MMP-1 is further implicated in complex processes induced by H. pylori, resulting in tissue degradation and remodeling of the gastric mucosa.     

ERK介导幽门螺杆菌HSP60感染胃上皮细胞的IL-8分泌

目的：探讨幽门螺杆菌热休克蛋白60（H．pylori—HSP60）感染胃上皮细胞后ERK与白介素-8（IL-8）分泌的关系。方法：利用ELISA技术,对活菌（IntactH．pylori）、死菌（Heat—killedH．pylori）及H．pylori—HSP60刺激胃上皮细胞KATOIII的IL_8蛋白分泌水平进行分析,观察IL-8随以上抗原浓度梯度的变化及ERK抑制剂PD98059对其分泌量的影响;利用Westernblot技术,观察KATOⅢ胞中磷酸化ERK随IntactH．pylori、Heat—killedH．pylori及H．pylori—HSP60刺激时间的变化状况。结果：IL-8的分泌随着IntactH．pylori、Heat—killedH．pylori及H．pylori—HSP60刺激浓度的升高而增高;H．pylori刺激KATOⅢ胞1h后ERK开始表达,其中IntactH．pylori在9h时表达达到高峰,Heat·killedH．pylori在24h时达到高峰,而H．pylori-HSP60刺激KATOⅢ胞6h后ERK开始表达,9h时达到高峰;PD98059抑制了H．pylori—HSP60诱导的IL-8的分泌。结论：ERK介导了H．pylori—HSP60感染的胃上皮细胞的IL-8的分泌。     

Non-T cell activation linker regulates ERK activation in Helicobacter pylori-infected epithelial cells

It is supposed that human pathogens, e.g. Helicobacter pylori abuse lipid raft domains on the host cell plasma membrane to infect the cell. Investigating DRM-associated molecules we identified the transmembrane adapter proteins (TRAPs), non-T cell activation linker (NTAL) and lymphocyte-specific protein tyrosine kinase (Lck)-interacting membrane protein (LIME) to be regulated by H. pylori in the human epithelial cell line HCA-7. Up to now, raft-associated TRAPs were exclusively described to mediate signal propagation downstream of antigen receptors. Our results posed the question whether these proteins adopt a role in H. pylori-infected epithelial cells too. Our studies revealed that H. pylori induces tyrosine phosphorylation of NTAL as well as LIME within 15 min of infection. We observed that activated NTAL and LIME bind to the Src homology 2 (SH2)-domain of growth factor receptor-bound protein 2 (Grb2) within 15 to 30 min of infection and associate with the c-Met receptor. Further, NTAL has a contributory role in regulating H. pylori-induced extracellular signal-regulated kinase (ERK) activation. After suppression of NTAL protein levels by siRNA, ERK phosphorylation was reduced to approximately 50%. Additionally, the knockdown of NTAL suppressed the phosphorylation of cytosolic phospholipase A₂ (cPLA₂). Activated cPLA₂ catalyzes the release of arachidonic acid (AA), whose metabolites are pivotal mediators in the H. pylori-induced inflammatory response. Thus, we propose that NTAL participates in the activation of the c-Met-Grb2-ERK-cPLA₂ signalling cascade at early stages of H. pylori infection.     

Helicobacter pylori induces gastric epithelial cell invasion in a c-Met and type IV secretion system-dependent manner

Helicobacter pylori interacts with gastric epithelial cells, activating signaling pathways important for carcinogenesis. In this study we examined the role of H. pylori on cell invasion and the molecular mechanisms underlying this process. The relevance of H. pylori cag pathogenicity island-encoded type IV secretion system (T4SS), CagA, and VacA for cell invasion was also investigated. We found that H. pylori induces AGS cell invasion in collagen type I and in Matrigel invasion assays. H. pylori-induced cell invasion requires the direct contact between bacteria and cancer cells. H. pylori-mediated cell invasion was dependent on the activation of the c-Met receptor and on increased MMP-2 and MMP-9 activity. The abrogation of the c-Met receptor using the specific NK4 inhibitor or the silencing of c-Met expression with small interference RNA suppressed both cell invasion and MMP activity. Studies with different H. pylori strains revealed that cell invasion, c-Met tyrosine phosphorylation, and increased MMP-2 and MMP-9 activity were all dependent on the presence of a functional bacterial T4SS, but not on VacA cytotoxicity. Our findings demonstrate that H. pylori strains with a functional T4SS stimulate gastric epithelial cell invasion through a c-Met-dependent signaling pathway that comprises an increase in MMP-2 and MMP-9 activity.     

Helicobacter pylori CagA inhibits the expression of Runx3 via Src/MEK/ERK and p38 MAPK pathways in gastric epithelial cell

Infection with CagA-positive Helicobacter pylori is the strongest risk factor for gastric carcinoma. Upon delivery into gastric epithelial cells, CagA disturbs cellular functions by physically interacting with and deregulating intracellular signaling molecules via both tyrosine phosphorylation-dependent and -independent mechanisms. Runx3 was suggested to be a tumor suppressor and closely associated with tumorigenesis and progression of gastric cancer. The aim of our study is to verify the effect of H. pylori virulence factor CagA on Runx3 expression level and investigate the corresponding molecular mechanisms and signaling pathways influencing Runx3 expression. Human gastric epithelial immortalized GES-1 cells were transfected with CagA-expression vector or control vector with FuGENE HD transfection reagent. Runx3 expression levels were determined by QRT-PCR and immunoblotting. Then we constructed a 1,150 bp Runx3 promoter luciferase reporter plasmid, pGL(3)-1150 bp, which was co-transfected into GES-1 cell with CagA-expression vector or control vector. Luciferase reporter assay was used to determine the effects of CagA on the 1,150 bp promoter activity of Runx3. Signal inhibitors were used to detect the signal pathway(s) through which CagA affects Runx3. Our results showed that CagA can reduce the expression level of Runx3 at both mRNA and protein levels significantly. Importantly, the 1,150 bp Runx3 promoter activity was decreased in cells transfected with CagA-expression vector comparing with cells transfected with control vector. And this inhibition is dependent on the phosphorylation of CagA. Signal pathways Src/MEK/ERK and p38 MAPK are involved in this regulation. Our findings provide new insights for understanding the mechanism of H. pylori carcinogenesis.     

MMP-12 induces IL-8/CXCL8 secretion through EGFR and ERK1/2 activation in epithelial cells

Macrophage metalloelastase (MMP-12) is described to be involved in pulmonary inflammatory response. To determine the mechanisms linking MMP-12 and inflammation, we examined the effect of recombinant human MMP-12 (rhMMP-12) catalytic domain on IL-8/CXCL8 production in cultured human airway epithelial (A549) cells. Stimulation with rhMMP-12 resulted in a concentration-dependent IL-8/CXCL8 synthesis 6 h later. Similar results were also observed in cultured BEAS-2B bronchial epithelial cells. In A549 cells, synthetic matrix metalloproteinase (MMP) inhibitors prevented rhMMP-12-induced IL-8/CXCL8 release. We further demonstrated that in A549 cells, rhMMP-12 induced transient, peaking at 5 min, activation of ERK1/2. Selective MEK inhibitors (U0126 and PD-98059) blocked both IL-8/CXCL8 release and ERK1/2 phosphorylation. IL-8/CXCL8 induction and ERK1/2 activation were preceded by EGF receptor (EGFR) tyrosine phosphorylation, within 2 min, and reduced by selective EGFR tyrosine kinase inhibitors (AG-1478 and PD168393) by a neutralizing EGFR antibody and by small interfering RNA oligonucleotides directed against EGFR, implicating EGFR activation. In addition, we observed an activation of c-Fos in A549 cells stimulated by rhMMP-12, dependent on ERK1/2. Using small interfering technique, we showed that c-Fos is involved in rhMMP-12-induced IL-8/CXCL8 production. From these results, we conclude that one mechanism, by which MMP-12 induces IL-8/CXCL8 release from the alveolar epithelium, is the EGFR/ERK1/2/activating protein-1 pathway.     

Helicobacter pylori infection and CagA protein translocation in human primary gastric epithelial cell culture

BACKGROUND: Increasing evidence has shown that Helicobacter pylori CagA protein translocation into gastric epithelial cells plays an important role in the development of gastric inflammation and malignancy. Translocated CagA undergoes tyrosine phosphorylation in gastric adenocarcinoma cell line cells, and CagA involves disruption of cellular apical-junction complex in Madin-Darby canine kidney cells. METHODS: To elucidate whether these events take place in normal human gastric epithelium, we infected human primary gastric epithelial cells with H. pylori. RESULTS: Our results demonstrate that CagA protein was translocated into primary gastric epithelial cells and tyrosine phosphorylated. The translocated CagA induces cytoskeletal rearrangement and the disruption of tight junctions in primary gastric epithelial cells. CONCLUSIONS: This study provides direct evidence of the modulation of gastric epithelial cells by CagA protein translocation, and advances our understanding of the pathogenesis of H. pylori infection.     

幽门螺杆菌ureB基因转染胃上皮细胞及其对细胞的作用

研究幽门螺杆菌 (Helicobacterpylori,Hp)ureB基因重组子转染胃上皮细胞后对胃上皮细胞的作用。用PCR方法从Hp标准株NCTC116 37中获取ureB全长基因 ,将其开放读码框架定向克隆入真核表达载体pcDNA3 1;获得的重组子转染SGC 790 1细胞 ,筛选耐潮霉素的细胞克隆 ,用RT PCR方法检测细胞内ureB基因在转录水平的表达 ;分别用荧光染色技术、MTT、流式细胞术检测UreB对细胞表型、增殖、凋亡及细胞周期的影响。UreB阳性表达的细胞 (SureB)胞膜出芽、细胞皱缩 ;用MTT法检测细胞增殖 ,结果表明 ,SureB细胞与SpcDNA3 1细胞比较 (pcDNA3 1转染的细胞 ) ,生长增殖无显著性差异 (P >0 0 5 ) ,流式细胞术检测细胞凋亡结果显示 ,SureB的凋亡率显著高于SpcDNA3 1(P值为 0 0 0 7) ;细胞周期分析显示 ,SureB细胞有S期比率增高、G2 M、G0 G1 期比率下降的趋势。ureB在培养细胞内的表达可促进细胞凋亡     

Helicobacter pylori inhibits gastric cell cycle progression

Helicobacter pylori infection of the gastric mucosa is associated with changes in gastric epithelial cell proliferation. In vitro studies have shown that exposure to H. pylori inhibits proliferation of gastric cells. This study sought to investigate the cell cycle progression of gastric epithelial cell lines in the presence and absence of H. pylori. Unsynchronized and synchronized gastric epithelial cell lines AGS and KatoIII were exposed to H. pylori over a 24-h period. Cell cycle progression was determined by flow cytometry using propidium iodide (PI), and by analysis of cyclin E, p21, and p53 protein expression using Western blots. In the absence of H. pylori 40, 45, and 15% of unsynchronized AGS cells were in G(0)-G(1), S, and G(2)-M phases, respectively, by flow cytometry analysis. When AGS cells were cultured in the presence of H. pylori, the S phase decreased 10% and the G(0)-G(1) phase increased 17% after 24 h compared with the controls. KatoIII cells, which have a deleted p53 gene, showed little or no response to H. pylori. When G1/S synchronized AGS cells were incubated with media containing H. pylori, the G(1) phase increased significantly (25%, P < 0.05) compared with controls after 24 h. In contrast, the control cells were able to pass through S phase. The inhibitory effects of H. pylori on the cell cycle of AGS cells were associated with a significant increase in p53 and p21 expression after 24 h. The expression of cyclin E was downregulated in AGS cells following exposure of AGS cells to H. pylori for 24 h. This study shows that H. pylori-induced growth inhibition in vitro is predominantly at the G(0)-G(1) checkpoint. Our results suggest that p53 may be important in H. pylori-induced cell cycle arrest. These results support a role for cyclin-dependent kinase inhibitors in the G(1) cell cycle arrest exerted by H. pylori and its involvement in changing the regulatory proteins, p53, p21, and cyclin E in the cell cycle.     

Sphingosine-1-phosphate stimulates human Caco-2 intestinal epithelial proliferation via p38 activation and activates ERK by an independent mechanism

Sphingosine-1-phosphate (S-1-P) has been identified as an extracellular mediator and an intracellular second messenger that may modulate cell motility, adhesion, proliferation, and differentiation and cancer cell invasion. Widely distributed, S-1-P is most abundant in the intestine. Although S-1-P is likely to modulate various intracellular pathways, activation of the mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase 1 (ERK1), ERK2, and p38 is among the best-characterized S-1-P effects. Because the MAPKs regulate proliferation, we hypothesized that S-1-P might stimulate intestinal epithelial cell proliferation by MAPK activation. Human Caco-2 intestinal epithelial cells were cultured on a fibronectin matrix because fibronectin is an important constituent of the gut mucosal basement membrane. We assessed ERK1, ERK2, and p38 activation by Western blotting with antibodies specific for their active forms and proliferation by Coulter counting at 24 h. Specific MAP kinase kinase (MEK) and p38 inhibitors PD98059 (20 microM) and SB202190 and SB203580 (10 and 20 microM) were used to probe the role of ERK and p38 in S-1-P-mediated proliferation. Three or more similar studies were pooled for the analysis. S-1-P stimulated Caco-2 proliferation and dose-responsively activated ERK1, ERK2, and p38. Proliferation peaked at 5 microM, yielding a cell number 166.3 +/- 2.7% of the vehicle control (n = 6, P < 0.05). S-1-P also maximally stimulated ERK1, ERK2, and p38 at 5 microM, to 164.4 +/- 19.9%, 232.2 +/- 38.5%, and 169.2 +/- 20.5% of the control, respectively. Although MEK inhibition prevented S-1-P activation of ERK1 and ERK2 and slightly but significantly inhibited basal Caco-2 proliferation, MEK inhibition did not block the S-1-P mitogenic effect. However, pretreatment with 10 microM SB202190 or SB203580 (putative p38 inhibitors) attenuated the stimulation of proliferation by S-1-P. Twenty micromolars of SB202190 or SB203580 completely blocked the mitogenic effect of S-1-P. Ten to twenty micromolars of SB202190 and SB203580 also dose-dependently ablated the effects of 5 microM S-1-P on heat shock protein 27 accumulation, a downstream consequence of p38 MAPK activation. Consistent with the reports in some other cell types, S-1-P appears to activate ERK1, ERK2, and p38 and to stimulate proliferation. However, in contrast to the mediation of the S-1-P effects in some other cell types, S-1-P appears to stimulate human intestinal epithelial proliferation by activating p38. ERK activation by S-1-P is not required for its mitogenic effect.     

Effect of Helicobacter pylori infection and eradication on gastric epithelial cell proliferation and apoptosis.

OBJECTIVES: the effect of Helicobacter pylori infection on gastric epithelial cell proliferation and apoptosis is still controversial. Our aim was to evaluate the effect of H. pylori infection on cell kinetic parameters in normal gastric epithelium, gastritis with/without intestinal metaplasia and gastric cancer. PATIENTS AND METHODS: antral biopsies were taken from 121 patients (61 women, 60 men, mean age 58.5+/-14.3 years of age) who underwent routine gastroscopy for upper gastrointestinal symptoms. Sections were scored for normal epithelia (n=15), gastritis without intestinal metaplasia (n=74), gastritis with intestinal metaplasia (n=24), and gastric adenocarcinoma (n=8). Fifty-two patients had H. pylori positive gastritis, and success of H. pylori eradication therapy was controlled in 12 cases, all with intestinal metaplasia. To characterize cell proliferation and assess apoptosis, immunohistochemistry [Proliferating Cell Nuclear Antigen (PCNA)], histochemistry [Argyrophil Nucleolar Organizer Regions (AgNOR)], and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridinetriphosphate (dUTP) nick end-labeling (TUNEL) were used, respectively. RESULTS: both cell proliferation and apoptosis is was higher in chronic gastritis when compared with normal epithelia, but neither PCNA LI (54.79+/-19.1 vs. 53.20+/-20.7) nor AgNOR counts (291.43+/-44.3 vs. 277.8+/-57.54) were different in H. pylori positive versus negative chronic gastritis. A significant positive correlation (P<0.05) was found in this group between PCNA and AgNOR techniques. Apoptosis was significantly higher (P<0.05) in H. pylori positive cases only when intestinal metaplasia was not present. Cell proliferation in intestinal metaplasia decreased to the activity of normal epithelium after successful eradication of H. pylori but remained high if eradication therapy failed. CONCLUSIONS: epithelial cell proliferation does not depend on H. pylori status in chronic gastritis. H. pylori increases apoptosis only in the absence of intestinal metaplasia.     

ANG II stimulates PKC-dependent ERK activation,DNA synthesis,and cell division in intestinal epithelial cells

PKC, a major target for the tumor-promoting phorbol esters, has been implicated in the signal transduction pathways that mediate important functions in intestinal epithelial cells, including proliferation and carcinogenesis. With the use of IEC-18 cells arrested in G0/G1, addition of phorbol esters resulted in a modest increase in [3H]thymidine incorporation and a slight shift toward the S and G2/M phases of the cell cycle, whereas the combination of EGF and phorbol 12,13-dibutyrate (PDB) synergistically stimulated DNA synthesis. To investigate the effects of receptor-mediated PKC activation on mitogenesis, we demonstrated that ANG II induced ERK activation, a response completely blocked by pretreatment with mitogen/extracellular signal-regulated kinase inhibitors or specific PKC inhibitors. Furthermore, ANG II stimulated an over threefold increase in [3H]thymidine incorporation that was corroborated by flow cytometric analysis of the cell cycle to levels comparable to that achieved by the combination of EGF and PDB. Taken together, our results indicate that receptor-mediated PKC activation, as induced by ANG II, transduces mitogenic signals leading to DNA synthesis and cell proliferation in IEC-18 cells.     

Nutrients released by gastric epithelial cells enhance Helicobacter pylori growth

BACKGROUND: Helicobacter pylori survives and proliferates in the human gastric mucosa. In this niche, H. pylori adheres to the gastric epithelial cells near the tight junctions. In vitro, H. pylori proliferated well in tissue-culture medium near gastric epithelial cells. However, in the absence of epithelial cells, growth of H. pylori could only be established in tissue-culture medium when, prior to the experiment, it was preincubated near gastric epithelial cells. Therefore, we aimed to determine whether diffusion of nutrients derived from epithelial cells was required for H. pylori growth in Dulbecco's modified Eagle's minimal essential medium (DMEM) cell culture medium. MATERIALS AND METHODS: Cell culture conditions essential for H. pylori growth in vitro were determined with gastric epithelial HM02 cells. RESULTS: Deprivation of iron in cell-culture-conditioned DMEM resulted in a growth arrest of H. pylori. However, near gastric epithelial cells, growth of H. pylori was resistant to iron deprivation. Evidently, when residing close to epithelial cells, H. pylori was able to fulfil its iron requirements, even when the DMEM was deprived of iron. Nevertheless, supplementation with iron alone did not restore H. pylori growth in DMEM, hence other nutrients were deficient as well in the absence of epithelial cells. Growth of H. pylori in DMEM was restored when hypoxanthine, L-alanine and L-proline were added to the DMEM. CONCLUSIONS: Diffusion of (precursors of) these nutrients from the gastric epithelial cells is essential for H. pylori growth in vitro. We hypothesize that in vivo, H. pylori favors colonization near the tight junctions, to gain maximal access to the nutrient(s) released by gastric epithelial cells.     

Translocation of the Helicobacter pylori CagA protein in gastric epithelial cells by a type IV secretion apparatus

Helicobacter pylori is one of the most common bacterial pathogens, infecting about 50% of the world population. The presence of a pathogenicity island (PAI) in H. pylori has been associated with gastric disease. We present evidence that the H. pylori protein encoded by the cytotoxin-associated gene A ( cagA ) is translocated and phosphorylated in infected epithelial cells. Two-dimensional gel electrophoresis (2-DE) of proteins isolated from infected AGS cells revealed H. pylori strain-specific and time-dependent tyrosine phosphorylation and dephosphorylation of several 125–135 kDa and 75–80 kDa proteins. Immunoblotting studies, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), cell fractionation and confocal microscopy demonstrated that one of the 125–135 kDa proteins represents the H. pylori CagA protein, which is translocated into the host cell membrane and the cytoplasm. Translocation of CagA was dependent on functional cagA gene and virulence ( vir ) genes of a type IV secretion apparatus composed of virB4 , virB7 , virB10 , virB11 and virD4 encoded in the cag PAI of H. pylori . Our findings support the view that H. pylori actively translocates virulence determinants, including CagA, which could be involved in the development of a variety of gastric disease.     

Protein changes in gastric epithelial cells RGM-1 in response to Helicobacter pylori infection

Helicobacter pylori-induced inflammation significantly increases the risk of gastric cancer. To investigate the role of H. pylori infection in gastric epithelial cell carcinogenesis, flow cytometry was used to analyze the apoptosis of gastric epithelial cells infected by H. pylori. Next, LTQ MS mass spectrometry (MS) was applied to identify protein changes in gastric epithelial cells infected with H. pylori, and then bioinformatics was adopted to analyze the cellular localization and biological function of differential proteins. LTQ MS/MS successfully identified identified 22 differential proteins successfully, including 20 host-cell proteins and two H. pylori bacterial proteins. Also, human proteins were located in all areas of cells and involved in various cell biological functions. The oncogene proteins p53, p16, and C-erbB-2 proteins in H. pylori-infected RGM-1 cells were remarkably increased from the analysis by Western blot analysis. H. pylori infection of gastric epithelial cells leads to changes in various protein components in the cell, and enhances the expression of oncogene proteins, thereby increasing the possibility of possibility of carcinogenesis of H. pylori infection.