ceRNA network construction and comparison of gastric cancer with or without Helicobacter pylori infection

Gastric cancer (GC) is a lethal disease, and among its variety of etiological factors, Helicobacter pylori (H. pylori) infection is the strongest risk factor. However, the genetic and molecular mechanisms underlying H. pylori-related GC need further elucidation. We investigated the competing endogenous RNA (ceRNA) network differences between H. pylori (+) and H. pylori (−) GC. The long noncoding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) expression data from 32 adjacent noncancerous samples and 18 H. pylori (+) and 141 H. pylori (−) stomach adenocarcinoma samples were downloaded from the TCGA database. After construction of lncRNA–miRNA–mRNA ceRNA networks of H. pylori (+) and H. pylori (−) GC, Panther and Kobas databases were used to analyze the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Finally, survival analysis was used to discover the key genes. In H. pylori (+) GC, we identified a total of 1,419 lncRNAs, 82 miRNAs, and 2,501 mRNAs with differentially expressed profiles. In H. pylori (−) GC, 2,225 lncRNAs, 130 miRNAs, and 3,146 mRNAs were differentially expressed. Furthermore, three unique pathways (cytokine–cytokine receptor interaction, HIF-1 signaling pathway, and Wnt signaling pathway) were enriched in H. pylori (+) GC. According to the overall survival analysis, three lncRNAs (AP002478.1, LINC00111, and LINC00313) and two mRNAs (MYB and COL1A1) functioned as prognostic biomarkers for patients with H. pylori (+) GC. In conclusion, our study has identified the differences in ceRNA regulatory networks between H. pylori (+) and H. pylori (−) GC and provides a rich candidate reservoir for future studies.     

Genome-wide DNA methylation profiles in noncancerous gastric mucosae with regard to Helicobacter pylori infection and the presence of gastric cancer

Background and Aims: To determine genome‐wide DNA methylation profiles induced by Helicobacter pylori (H. pylori) infection and to identify methylation markers in H. pylori‐induced gastric carcinogenesis. Methods: Gastric mucosae obtained from controls (n = 20) and patients with gastric cancer (n = 28) were included. A wide panel of CpG sites in cancer‐related genes (1505 CpG sites in 807 genes) was analyzed using Illumina bead array technology. Validation of the results of Illumina bead array technique was performed using methylation‐specific PCR method for four genes (MOS, DCC, CRK, and PTPN6). Results: The Illumina bead array showed that a total of 359 CpG sites (269 genes) were identified as differentially methylated by H. pylori infection (p < .0001). The correlation between methylation‐specific PCR and bead array analysis was significant (p < .0001, Spearman coefficient = 0.5054). Methylation profiles in noncancerous gastric mucosae of the patients with gastric cancer showed quite distinct patterns according to the presence or absence of the current H. pylori infection; however, 10 CpG sites were identified to be hypermethylated and three hypomethylated in association with the presence of gastric cancer regardless of H. pylori infection (p < .01). Conclusions: Genome‐wide methylation profiles showed a number of genes differentially methylated by H. pylori infection. Methylation profiles in noncancerous gastric mucosae from the patients with gastric cancer can be affected by H. pylori‐induced gastritis. Differentially methylated CpG sites in this study needs to be validated in a larger population using quantitative methylation‐specific PCR method.     

Immune and proliferative cellular responses to Helicobacter pylori infection in the gastric mucosa of Mexican children

BACKGROUND: Helicobacter pylori infection occurs mostly during childhood, but few studies on this age group have addressed the innate immune and the proliferative response to this infection. Mexico has a high H. pylori prevalence in children, but a low risk of gastric cancer. The aim of this work was to study the cellular responses of the gastric mucosa to this infection in Mexican children. METHODS: Antral and corpus gastric biopsies were obtained from 44 H. pylori-infected children (mean age 12 +/- 3.2 years) and 44 uninfected children (mean age 10 +/- 3 years). Mucosal cellular responses were studied by immunohistochemistry, using anti-Ki67 antibodies for proliferation studies, antihuman tryptase for mast cells, and antihuman CD68 for macrophages. T and B lymphocytes were stained with a commercial integrated system. The intensity of cellular responses was estimated histologically using the software KS300. RESULTS: Epithelium proliferation and infiltration of macrophages and T and B lymphocytes were significantly higher in H. pylori-infected than in uninfected children. A balanced increase of CD4, CD8, and CD20 lymphocytes was observed in infected children. However, activated mast cells were decreased, and infiltration of neutrophil and mononuclear cells was low. Epithelial proliferation was associated with polymorphonuclear infiltration but not with infiltration of macrophages or lymphocytes. Inflammation and proliferation was higher in CagA (+)-infected children. CONCLUSIONS: Mexican children respond to H. pylori infection with a low inflammatory response, a balanced increase of T and B lymphocytes, and a high regenerative activity.     

Current information on the association of Helicobacter pylori with autophagy and gastric cancer

Helicobacter pylori (H. pylori) is a Gram-negative bacterium and causative agent of gastric cancer. H. pylori induce defective autophagy or inhibit it by means of CagA and vacuolating cytotoxin A (VacA) toxins leading to the gastric cancer induction. Impaired or defective autophagy leads to the accumulation of cytotoxic materials, such as ROS and P62 that lead to increased mutations in the DNA, genome instability, and risk of cancer formation. H. pylori CagA may inhibit autophagy through the c-Met-PI3k/Akt-mTOR signaling pathway. However, VacA induces autophagy by some signaling pathways. In the gastric epithelial cells, VacA is a necessary and sufficient factor for the creation of autophagy. While CagA is a negative regulator of this phenomenon, the elimination of this gene from H. pylori has increased autophagy and the production of inflammatory cytokines is reduced. In gastrointestinal cancers, some of the microRNAs (miRNAs) act as tumor suppressors and some other are oncogenes by regulating various genes expression. H. pylori can also modify autophagy through a mechanism that includes the function of miRNAs. In autophagy, oncogenic miRNAs inhibit activation of some tumor suppressor signaling pathways (e.g., ULK1 complex, Beclin-1 function, and Atg4 messaging), whereas tumor suppressor miRNAs can block the activation of oncogenic signaling pathways. For instance, Beclin-1 is negatively regulated by miRNA-376b (oncogenic miRNA) and miRNA-30a (tumor suppressor miRNA). Similarly, Atg4 by miRNA-376b (oncogenic miRNA) and miRNA-101 (tumor suppressor miRNA). So, this apparent paradox can be explained as that both Beclin-1 and Atg4 play different roles in a particular cell or tissue.     

Epigenetic changes in gastric cancer induction by Helicobacter pylori

Epigenetic disorder mechanisms are one of the causes of cancer. The most important of these changes is the DNA methylation, which leads to the spread of Helicobacter pylori and inflammatory processes followed by induction of DNA methylation disorder. Mutations and epigenetic changes are the two main agents of neoplasia. Epithelial cells infection by H. pylori associated with activating several intracellular pathways including: MAPK, NF-κB, Wnt/β-catenin, and PI3K are affects a variety of cells and caused to an increase in the production of inflammatory cytokines, changes in apoptosis, proliferation, differentiation, and ultimately leads to the transformation of epithelial cells into oncogenic. The arose of free radicals impose the DNA cytosine methylation, and NO can increase the activity of DNA methyltransferase. H. pylori infection causes an environment that mediates inflammation and signaling pathways that probably caused to stomach tumorigenicity. The main processes that change by decreasing or increasing the expression of various microRNAs expressions include immune responses, apoptosis, cell cycle, and autophagy. In this review will be describe a probably H. pylori roles in infection and mechanisms that have contribution in epigenetic changes in the promoter of genes.     

Helicobacter pylori infection and colorectal cancer risk: a meta-analysis

BACKGROUND: Several studies suggested an association between Helicobacter pylori infection and colorectal carcinoma or adenoma risk. However, different authors reported quite varying estimates. We carried out a systematic review and meta-analysis of published studies investigating this association and paid special attention to the possibility of publication bias and sources of heterogeneity between studies. Materials and METHODS: An extensive literature search and cross-referencing were performed to identify all published studies. Summary estimates were obtained using random-effects models. The presence of possible publication bias was assessed using different statistical approaches. RESULTS: In a meta-analysis of the 11 identified human studies, published between 1991 and 2002, a summary odds ratio of 1.4 (95% CI, 1.1-1.8) was estimated for the association between H. pylori infection and colorectal cancer risk. The graphical funnel plot appeared asymmetrical, but the formal statistical evaluations did not provide strong evidence of publication bias. The proportion of variation of study results because of heterogeneity was small (36.5%). CONCLUSIONS: The results of our meta-analysis are consistent with a possible small increase in risk of colorectal cancer because of H. pylori infection. However, the possibility of some publication bias cannot be ruled out, although it could not be statistically confirmed. Larger, better designed and better controlled studies are needed to clarify the situation.     

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.     

Development of a novel gene signature in patients without Helicobacter pylori infection gastric cancer

Gastric cancer (GC) is one of the most fatal common cancers in worldwide. Helicobacter pylori (H. pylori) infection is closely related to the development of GC, although the mechanism is still unclear. In our study, we aim to develop a robust messenger RNA (mRNA) signature associated with H. pylori (-) GC that can sensitively and efficiently predict the prognostic. The RNA-seq expression profile and corresponding clinical data of 598 gastric cancer samples and 63 normal samples obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus database. Using gene set enrichment analysis H. pylori (+) GC and H. pylori (-) GC patients and normal samples to select certain genes for further analysis. Using univariate and multivariate Cox regression model to establish a gene signature for predicting the overall survival (OS). Finally, we identified G2/M related seven-mRNA signature (TGFB1, EGF, MKI67, ILF3, INCENP, TNPO2, and CHAF1A) closely related to the prognosis of patients with H. pylori (-) GC. The seven-mRNA signature was identified to act as an independent prognostic biomarker by stratified analysis and multivariate Cox regression analysis. It was also validated on two test groups from TCGA and GSE15460 and shown that patients with high-risk scores based on the expression of the seven mRNAs had significantly shorter survival times compared to patients with low-risk scores (P < .0001). In this study, we developed a seven-mRNA signature related to G2/M checkpoint from H. pylori (-) GCs that as an independent biomarker potentially with a good performance in predicting OS and might be valuable for the clinical management for patients with GC.     

Diversity of Helicobacter pylori cagA and vacA genes in Costa Rica: its relationship with atrophic gastritis and gastric cancer

BACKGROUND: Associations between Helicobacter pylori gene diversity and gastric cancer have not been reported on in Costa Rica, despite its being one of the countries with the highest gastric cancer incidence and mortality rates in the world. The aim of this study was to determine the prevalence of H. pylori cagA and vacA genes and investigate whether it could be correlated with atrophic gastritis (AG) and gastric cancer (GC) in Costa Rica. MATERIALS AND METHODS: Genomic DNAs from isolates of 104 patients classified into two groups: non-atrophic gastritis group (n = 68) and atrophic gastritis group (n = 36), were subjected to PCR-based genotyping of cagA and vacA genes and their correlation with clinical outcome was investigated. Total DNA extractions from gastric tissues of 25 H. pylori-infected gastric cancer patients were utilized for comparative purposes. RESULTS: The presence of cagA (75.3%), vacA s1b (75.3%), and vacA m1 (74.2%) was detected, and colonization by strains with different vacA genotypes in the same stomach was found in 9.7% of the patients. Age- and sex-adjusted vacA s1b and vacA m1 were associated with GC while only vacA m1 was significantly associated with AG. A tendency for association between cagA and vacA s1b, and AG was reported. CONCLUSIONS: The prevalence status of the cagA and vacA (s1/m1) genes in Costa Rica seems to fall between that found in European/North American and East Asian countries, and both cagA and vacA seem to have clinical relevance in this country.     

Helicobacter pylori antibodies and gastric cancer: a gender-related difference

Helicobacter pylori has been proposed as a causative agent of gastric cancer. The aim of this study was to define serum antibodies response against different H. pylori antigens in patients with gastric cancer. Serum samples were collected from 115 Lithuanian patients with non-cardia gastric cancer and 110 age- and sex-matched controls without cancer. Heat-stable, low-molecular-mass, and outer membrane proteins were used as antigens to analyze serum IgG antibody response against H. pylori by enzyme-linked immunosorbent assay. Seroprevalence of H. pylori using low-molecular-mass antigen was significantly higher in gastric cancer patients, compared to controls (77% versus 57%, p<0.05). Significant differences in the prevalence of H. pylori infection between gastric cancer patients and controls were found in females using all three studied antigens: heat-stable (98% versus 84%, p<0.05), low-molecular-mass (88% versus 48%, p<0.05) and outer membrane proteins (78% versus 57%, p<0.05). In males, no significant differences were revealed between gastric cancer patients and controls. There may be other cofactors in addition to H. pylori that are important for the development of gastric cancer. H. pylori seems, however, to be a more important for development of gastric cancer in females than in males or males may have more confounding risk factors for gastric cancer than females.     

Helicobacter pylori Infection in Children

The review summarizes the articles published on Helicobacter pylori in children between April 2007 and March 2008. Evidence is emerging in different populations including developing countries that the prevalence of H. pylori is declining in all age groups. The reasons for this are unclear but it is unlikely that treatment of infection or improvement in socioeconomic conditions fully explains the decline. For the first time, differences in the inflammatory response between adults and children have been well characterized in a group of adults and children from Chile with similar levels of H. pylori infection. This study suggests that the reduced inflammatory response to H. pylori at a cellular level in children could be the consequence of an enhanced Treg cell response, which in turn down-regulates H. pylori -induced inflammation. The publication of the Paediatric European Register for Treatment of Helicobacter pylori study (PERTH) is important as it demonstrates the advantages of different centers working in collaboration for the benefit of children. It also highlights the fact that while bismuth-based treatment is more effective than proton pump inhibitor-based treatment in children, bismuth preparations are not widely available for use in children.     

Helicobacter pylori infection up-regulates gland mucous cell-type mucins in gastric pyloric mucosa

Background. Two types of mucous cell are present in gastric mucosa: surface mucous cells (SMCs) and gland mucous cells (GMCs), which consist of cardiac gland cells, mucous neck cells, and pyloric gland cells. We have previously reported that the patterns of glycosylation of SMC mucins are reversibly altered by Helicobacter pylori infection. In this study, we evaluated the effects of H. pylori infection on the expression of GMC mucins in pyloric gland cells. Methods. Gastric biopsy specimens from the antrums of 30 H. pylori‐infected patients before and after eradication of H. pylori and 10 normal uninfected volunteers were examined by immunostaining for MUC6 (a core protein of GMC mucins), α1,4‐N‐acetyl‐glucosaminyl transferase (α4GnT) (the glycosyltransferase which forms GlcNAcα1‐4Galβ‐R), and GlcNAcα1‐4Galβ‐R (a GMC mucin‐specific glycan). Results. MUC6, α4GnT, and HIK1083‐reactive glycan were expressed in the cytoplasm, supranuclear region, and secretory granules in pyloric gland cells, respectively. The immunoreactivity of MUC6 and α4GnT, but not of GlcNAcα1‐4Galβ‐R, in the pyloric gland increased in H. pylori‐associated gastritis, and after the eradication of H. pylori, the increased expression of MUC6 and α4GnT in the gastric mucosa of H. pylori‐infected patients decreased to almost normal levels. This up‐regulation was correlated with the degree of inflammation. Conclusions. In addition to the synthesis of GMC mucins increasing reversibly, their metabolism or release may also increase reversibly in H. pylori‐associated gastritis. The up‐regulation of the expression of gastric GMC mucins may be involved in defense against H. pylori infection in the gastric surface mucous gel layer and on the gastric mucosa.