Helicobacter pylori in a Korean isolate expressed proteins differentially in human gastric epithelial cells

Application of proteomics to the study of Helicobacter pylori and implications for the clinic

INTRODUCTION

Helicobacter pylori (H. pylori) is a gram-negative bacterium that colonizes the gastric epithelium and mucous layer of more than half the world's population. H. pylori is a primary human pathogen, responsible for the development of chronic gastritis, peptic ulceration and gastric cancer. Proteomics is impacting several aspects of medical research: understanding the molecular basis of infection and disease manifestation, identification of therapeutic targets and discovery of clinically relevant biomarkers. Areas covered: The main aim of the present review is to provide a comprehensive overview of the contribution of proteomics to the study of H. pylori infection pathophysiology. In particular, we focused on the role of the bacterium and its most important virulence factor, CagA, in the progression of gastric cells transformation and cancer progression. We also discussed the proteomic approaches aimed at the investigation of the host response to bacterial infection. Expert commentary: In the field of proteomics of H. pylori, comprehensive analysis of clinically relevant proteins (functional proteomics) rather than entire proteomes will result in important medical outcomes. Finally, we provided an outlook on the potential development of proteomics in H. pylori research.

Differential Proteomic Analysis of Human Saliva using Tandem Mass Tags Quantification for Gastric Cancer Detection

Novel biomarkers and non-invasive diagnostic methods are urgently needed for the screening of gastric cancer to reduce its high mortality. We employed quantitative proteomics approach to develop discriminatory biomarker signatures from human saliva for the detection of gastric cancer. Salivary proteins were analyzed and compared between gastric cancer patients and matched control subjects by using tandem mass tags (TMT) technology. More than 500 proteins were identified with quantification, and 48 of them showed significant difference expression (p < 0.05) between normal controls and gastric cancer patients, including 7 up-regulated proteins and 41 down-regulated proteins. Five proteins were selected for initial verification by ELISA and three were successfully verified, namely cystatin B (CSTB), triosephosphate isomerase (TPI1), and deleted in malignant brain tumors 1 protein (DMBT1). All three proteins could differentiate gastric cancer patients from normal control subjects, dramatically (p < 0.05). The combination of these three biomarkers could reach 85% sensitivity and 80% specificity for the detection of gastric cancer with accuracy of 0.93. This study provides the proof of concept of salivary biomarkers for the non-invasive detection of gastric cancer. It is highly encouraging to turn these biomarkers into an applicable clinical test after large scale validation.

Identification of pathways related to FAF1/H. pylori-associated gastric carcinogenesis through an integrated approach based on iTRAQ quantification and literature review

Previously we showed that down-regulation of tumor suppressor FAF1 mRNA, potentially caused by H. pylori, correlated with increasing tumor differentiation and distant metastasis in gastric cancer. To identify molecular details about how FAF1 and H. pylori contribute to gastric carcinogenesis, we used the iTRAQ labeling approach involving LC-MS/MS to perform proteomic analysis of HGC-27 gastric cancer cells stably transfected with an FAF1 transgene and/or infected with H. pylori. Of the 2926 proteins examined, proteomics identified 157 for which the expression was altered as a result of FAF1 expression, 500 with altered expression as a result of H. pylori infection, and 246 with altered expression as a combined result of FAF1 expression and H. pylori infection. A literature review identified 21 proteins as being differentially expressed in H. pylori-associated gastric cancer in at least two studies. These two complementary analyses were combined in Ingenuity Pathway software, which predicted that FAF1/H. pylori-associated gastric carcinogenesis alters primarily biochemical pathways related to mitochondrial dysfunction, oxidative phosphorylation, integrin signaling, cholesterol/leucine metabolism and G2/M checkpoint regulation. Differential expression of key proteins in several of these pathways was validated by immunoblotting in HGC-27 cells. This integrated approach combining proteomics and literature searching may prove fruitful for elucidating how FAF1 expression and H. pylori infection affect gastric carcinogenesis.

BIOLOGICAL SIGNIFICANCE

We established, for the first time, the proteomics databases of gastric cancer cell HGC-27 overexpressing FAF1 and infected with H. pylori through an integrated approach based on iTRAQ quantification and literature review, this strategy responded to the call for greater focus on data integration in primary/previous proteomic studies; and provided an integrated picture of the reference pathways and networks behind FAF1/H. pylori-associated gastric carcinogenesis, particularly pathways of mitochondrial dysfunction, oxidative phosphorylation, integrin signaling, cholesterol/leucine metabolism and G2/M checkpoint regulation.

Proteomics-Based Identification and Analysis of Proteins Associated with Helicobacter pylori in Gastric Cancer

Helicobacter pylori (H. pylori) is a spiral-shaped Gram-negative bacterium that causes the most common chronic infection in the human stomach. Approximately 1%-3% of infected individuals develop gastric cancer. However, the mechanisms by which H. pylori induces gastric cancer are not completely understood. The available evidence indicates a strong link between the virulence factor of H. pylori, cytotoxin-associated gene A (CagA), and gastric cancer. To further characterize H. pylori virulence, we established three cell lines by infecting the gastric cancer cell lines SGC-7901 and AGS with cagA⁺H. pylori and transfecting SGC-7901 with a vector carrying the full-length cagA gene. We detected 135 differently expressed proteins from the three cell lines using proteome technology, and 10 differential proteins common to the three cell lines were selected and identified by LC-MS/MS as well as verified by western blot: β-actin, L-lactate dehydrogenase (LDH), dihydrolipoamide dehydrogenase (DLD), pre-mRNA-processing factor 19 homolog (PRPF19), ATP synthase, calmodulin (CaM), p64 CLCP, Ran-specific GTPase-activating protein (RanGAP), P43 and calreticulin. Detection of the expression of these proteins and genes encoding these proteins in human gastric cancer tissues by real-time PCR (RT-qPCR) and western blot revealed that the expression of β-ACTIN, LDH, DLD, PRPF19 and CaM genes were up-regulated and RanGAP was down-regulated in gastric cancer tissues and/or metastatic lymph nodes compared to peri-cancerous tissues. High gene expression was observed for H. pylori infection in gastric cancer tissues. Furthermore, the LDH, DLD and CaM genes were demethylated at the promoter -2325, -1885 and -276 sites, respectively, and the RanGAP gene was highly methylated at the promoter -570 and -170 sites in H. pylori-infected and cagA-overexpressing cells. These results provide new insights into the molecular pathogenesis and treatment targets for gastric cancer with H. pylori infection.

[Proteomics analysis for Helicobacter pylori-infected gastric mucosa]

BACKGROUND/AIMS

Helicobacter pylori infection is linked to the development of gastric cancer. H. pylori-associated gastric inflammation is considered to be the first important step in the histogenesis of such neoplasia. However, studies that compare proteome of gastric mucosa infected with or without H. pylori are lacking.

METHODS

We employed proteomics analysis on the endoscopic biopsy specimens of gastric mucosa obtained from two groups (30 cases): healthy subjects without H. pylori infection (15 cases), and gastritis patients with H. pylori infection (15 cases). The pooled proteins obtained from gastric mucosa infected with or without H. pylori were separated by two-dimensional gel electrophoresis and analyzed by a computer-aided program. The altered protein expressions were then identified by mass spectrometry and validated by Western blotting and immunohistochemistry.

RESULTS

On mass spectrometry using MALDI TOF™ Analyzer, the up-regulation of Keratin 1, ezrin, adenosine triphosphate (ATP) synthase subunit alpha mitochondrial isoform c, Keratin type I cytoskeletal 19, and Keratin type I cytoskeletal 9 were identified; in contrast, 71 kd heat shock cognate protein, ATP synthase subunit alpha mitochondrial precursor, and annexin IV were down-regulated. Among them, membrane cytoskeleton linker ezrin was validated using Western blot and immunohistochemistry.

CONCLUSIONS

Expression of ezrin was significantly different between the gastric mucosa with and without H. pylori infection. Therefore, ezrin could be considered a promising potential molecular marker for detecting H. pylori infection in gastric mucosa.

The phenyl-thiophenyl propenone RK-I-123 reduces the levels of reactive oxygen species and suppresses the activation of NF-κB and AP-1 and IL-8 expression in Helicobacter pylori-infected gastric epithelial AGS cells

OBJECTIVE

To investigate whether the phenyl-thiophenyl propenone RK-I-123 suppresses interleukin-8 (IL-8) expression and activation of mitogen-activated protein kinases (MAPKs) and transcription factors (nuclear factor-κB [NF-κB] and activator protein-1 [AP-1]) by reducing reactive oxygen species (ROS) levels in Helicobacter pylori-infected gastric epithelial cells.

MATERIAL

Helicobacter pylori in Korean isolates, human gastric epithelial AGS cells.

TREATMENT

AGS cells pretreated with or without RK-I-123 were cultured in the presence of H. pylori at a bacterium/cell ratio of 300:1.

METHODS

Reactive oxygen species and IL-8 levels were determined by dichlorofluorescein fluorescence and enzyme-linked immunosorbent assay. The IL-8 mRNA expression was analyzed by the real-time reverse transcription-polymerase chain reaction (RT-PCR). The MAPK and IκBα levels were determined by western blotting. The activation of NF-κB and AP-1 was determined by the electrophoretic mobility shift assay.

RESULTS

Helicobacter pylori induced an increase in ROS and IL-8 expression and activation of MAPKs and transcription factors (NF-κB and AP-1) together with the degradation of IκBα in AGS cells, all of which were inhibited by RK-I-123.

CONCLUSIONS

The RK-I-123 suppressed the H. pylori-induced IL-8 expression and activation of MAPKs, NF-κB, and AP-1 by reducing ROS levels in AGS cells. The RK-I-123 may be a potential candidate for the treatment of H. pylori-induced gastric inflammation.

Protein disulfide isomerase in redox cell signaling and homeostasis

Thiol proteins may potentially act as redox signaling adaptor proteins, adjusting reactive oxygen species intermediates to specific signals and redox signals to cell homeostasis. In this review, we discuss redox effects of protein disulfide isomerase (PDI), a thioredoxin superfamily oxidoreductase from the endoplasmic reticulum (ER). Abundantly expressed PDI displays ubiquity, interactions with redox and nonredox proteins, versatile effects, and several posttranslational modifications. The PDI family contains >20 members with at least some apparent complementary actions. PDI has oxidoreductase, isomerase, and chaperone effects, the last not directly dependent on its thiols. PDI is a converging hub for pathways of disulfide bond introduction into ER-processed proteins, via hydrogen peroxide-generating mechanisms involving the oxidase Ero1α, as well as hydrogen peroxide-consuming reactions involving peroxiredoxin IV and the novel peroxidases Gpx7/8. PDI is a candidate pathway for coupling ER stress to oxidant generation. Emerging information suggests a convergence between PDI and Nox family NADPH oxidases. PDI silencing prevents Nox responses to angiotensin II and inhibits Akt phosphorylation in vascular cells and parasite phagocytosis in macrophages. PDI overexpression spontaneously enhances Nox activation and expression. In neutrophils, PDI redox-dependently associates with p47phox and supports the respiratory burst. At the cell surface, PDI exerts transnitrosation, thiol reductase, and apparent isomerase activities toward targets including adhesion and matrix proteins and proteases. Such effects mediate redox-dependent adhesion, coagulation/thrombosis, immune functions, and virus internalization. The route of PDI externalization remains elusive. Such multiple redox effects of PDI may contribute to its conspicuous expression and functional role in disease, rendering PDI family members putative redox cell signaling adaptors.

Role of 14-3-3 proteins in tumorigenesis and tumor progression

14-3-3 proteins are a family of acidic proteins that are predominantly localized in the cytoplasm. They have been known to play a role in tumorigenesis and tumor progression by regulating tumor cell growth, survival, proliferation, migration, and apoptosis. Of all 14-3-3 proteins, 14-3-3σ has tumor-suppressor activity, while other members have tumor-promoting activity. In this paper, we briefly review the role of 14-3-3 proteins in tumor pathogenesis.