Helicobacter pylori-associated gastritis is related to babA2 expression without heterogeneity of the 3' region of the cagA genotype in gastric biopsy specimens

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

Bile acid promotes intestinal metaplasia and gastric carcinogenesis

BACKGROUND

Bile acid and Helicobacter pylori (H. pylori) are important toxic factors for gastric mucosal injury. We examined the role of bile acid in promoting histologic gastritis and gastric carcinoma in Japanese patients.

METHODS

A total of 767 patients (452 men, mean age 51.1 years) were studied. Gastric juice was collected by gastro-endoscopic examination, and the bile acid concentration was examined by enzymatic method. The grade of histologic gastritis was evaluated by gastric biopsies, and the relationship between the bile acid concentration and the gastritis score was examined. The occurrence of gastric cancer was examined by a retrospective cohort study. CDX2/CINC1 expression in RGM-1 cells was evaluated by real-time PCR.

RESULTS

In H. pylori-positive patients, we found significant positive correlation between the bile acid concentration and the grades of atrophy/intestinal metaplasia (P < 0.01). However, we found significant negative associations between the bile acid concentrations and the histologic scores of mononuclear cell/neutrophil infiltrations (P < 0.01). Patients with a high concentration of bile acid developed gastric cancer more frequently than those with a low concentration (P < 0.05). Cholic acid treatment significantly increased CDX2 expression in RGM-1 cells. CINC1 expression in RGM-1 cell was significantly induced by coculture with H. pylori, and the induction was reduced by glycochenodeoxycholic acid treatment.

CONCLUSION

The bile acid in gastric juice contributes to the progression of histologic atrophy and intestinal metaplasia without inflammatory cell infiltration, followed by carcinogenesis in H. pylori-positive patients.

IMPACT

Bile acid promotes intestinal metaplasia and gastric carcinogenesis without inflammatory cell infiltration.

Risk assessment of gastric cancer caused by Helicobacter pylori using CagA sequence markers

Background

As a marker of Helicobacter pylori, Cytotoxin-associated gene A (cagA) has been revealed to be the major virulence factor causing gastroduodenal diseases. However, the molecular mechanisms that underlie the development of different gastroduodenal diseases caused by cagA-positive H. pylori infection remain unknown. Current studies are limited to the evaluation of the correlation between diseases and the number of Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs in the CagA strain. To further understand the relationship between CagA sequence and its virulence to gastric cancer, we proposed a systematic entropy-based approach to identify the cancer-related residues in the intervening regions of CagA and employed a supervised machine learning method for cancer and non-cancer cases classification.

Methodology

An entropy-based calculation was used to detect key residues of CagA intervening sequences as the gastric cancer biomarker. For each residue, both combinatorial entropy and background entropy were calculated, and the entropy difference was used as the criterion for feature residue selection. The feature values were then fed into Support Vector Machines (SVM) with the Radial Basis Function (RBF) kernel, and two parameters were tuned to obtain the optimal F value by using grid search. Two other popular sequence classification methods, the BLAST and HMMER, were also applied to the same data for comparison.

Conclusion

Our method achieved 76% and 71% classification accuracy for Western and East Asian subtypes, respectively, which performed significantly better than BLAST and HMMER. This research indicates that small variations of amino acids in those important residues might lead to the virulence variance of CagA strains resulting in different gastroduodenal diseases. This study provides not only a useful tool to predict the correlation between the novel CagA strain and diseases, but also a general new framework for detecting biological sequence biomarkers in population studies.

Helicobacter pylori cagA polymorphism and gastric inflammation: an international comparison between Japanese and Brazilian patients

OBJECTIVE

Gastritis induced by Helicobacter pylori can cause the onset of gastric cancer, and H. pylori cytotoxin associated gene A (cagA) is considered to be an important factor for its development. We investigated the relationship between the grades of gastritis and cagA phenotype in Japanese and Brazilian patients.

MATERIAL AND METHODS

We studied 47 Brazilian and 47 age-, gender-matched Japanese patients. Status of H. pylori infection, the degree of histologic gastritis, and the levels of serum pepsinogen levels were evaluated. DNA was extracted from paraffin-embedded sections and a portion of the cagA gene was amplified using the polymerase chain reaction, followed by direct sequencing of the fragment. We investigated the cagA subtype using a newly developed restriction fragment length polymorphism (RFLP) system.

RESULTS

In H. pylori-positive patients, the grades of histological and serological gastritis were more prominent in the Japanese subjects than their Brazilian counterparts, although no difference was detected in the H. pylori-negative subjects. According to cagA phenotype analysis, our RFLP system was helpful for evaluating cagA phenotype, and we found that the prevalence of the East Asia subtype was significantly higher in the Japanese subjects than in the Brazilian.

CONCLUSION

Infection with H. pylori possessing the East Asian cagA gene contributes to the progression of gastritis.

Pathogenetic role of the tyrosine-phosphorylated CagA EPIYA sequence of Helicobacter pylori in histological gastritis in Japanese patients

BACKGROUND

Helicobacter pylori (H. pylori) CagA protein plays an important role in the clinical outcome of gastritis treatment. Tyrosine phosphorylated Glu-Pro-Ile-Tyr-Ala motif in CagA (CagA-P) plays a critical role in the morphological transformation of cells.

AIM

We examine the relationship between serum titer of anti-CagA-P antibody and gastric inflammation as well as the status of the CagA-P expression in gastric mucosa.

METHODS

Fasting sera from 127 dyspeptic patients were collected, and anti-CagA-P antibody was evaluated. Gastric biopsy specimens were collected and histological gastritis was evaluated. We investigate the expression of CagA-P in human gastric mucosa by Western blotting and immunohistochemistry.

RESULTS

The titers of anti-CagA-P antibodies in the sera of H. pylori (+) patients were significantly higher than those of H. pylori (-) patients (P < 0.001). In 107 H. pylori (+) patients, anti-CagA-P titer was statistically higher in patients with high gastritis scores in the corpus than in those with low scores (P < 0.05). CagA-P expression was detected in the foveolar epithelium of the H. pylori infected gastric mucosa.

CONCLUSION

CagA-P is an antigen-peptide against the host, and serum titer of anti-CagA-P antibody may be a new marker for gastritis in the corpus.