Effect of Helicobacter pylori Eradication on Incidence of Gastric Cancer in Human and Animal Models: Underlying Biochemical and Molecular Events

Background:  Gastric cancer remains one of the most common cancers worldwide. A strong association exists between Helicobacter pylori infection and the risk of developing noncardia gastric cancer. H. pylori eradication by antibiotic treatment is regarded as a primary chemoprevention strategy to reduce gastric cancer incidence.
Aim:  To analyze the efficacy of H. pylori eradication in preventing gastric cancer in human and animal models, and to discuss whether biochemical, genetic, and epigenetic changes associated with H. pylori infection are reversible after curing the infection.
Results:  Several intervention trials have indicated that in some patients, H. pylori eradication leads to regression and prevents the progression of precancerous lesions. The eradication therapy reduces gastric cancer incidence in patients without any precancerous lesions at the baseline and is most effective before the development of atrophic gastritis. A few recent intervention studies in Japan have demonstrated significant prophylactic effects of eradication therapy on the development of gastric cancer, suggesting the use of eradication therapy in high-risk populations as a gastric cancer reduction strategy. However, gastric cancer may still develop despite successful eradication therapy. Studies in animal models have confirmed the use of eradication therapy at an early point of infection to prevent gastric cancer development.
Conclusion:  H. pylori eradication may not completely abolish the risk of gastric cancer. However, eradication therapy may be used in high-risk populations to reduce gastric cancer incidence. It can reverse many biochemical, genetic, and epigenetic changes that H. pylori infection induces in the stomach.     

Prevalence and risk factors for Helicobacter pylori infection in Chinese populations

Background:  The prevalence of Helicobacter pylori is higher in developing countries. The aim of this study was to investigate the prevalence and risk factors of H. pylori infection in areas with high prevalence of gastric cancer in Jiangsu Province, China.
Methods:  A prospective epidemiologic survey of H. pylori infection was accomplished in a natural population of 1457 individuals in Xiangshui and Gaoyou counties, Jiangsu Province, China. Questionnaires and laboratory tests for H. pylori infection (¹³C-urea breath test and serum IgG antibodies to H. pylori ) were used and performed, respectively.
Result:  Among 1371 subjects who completed questionnaires and H. pylori detection, 851 (62%) were H. pylori positive. The prevalence reached a peak at the age of 30–40 years (67%). There was no sex difference. The annual family income level was shown to be positively correlated with the risk of H. pylori infection. The prevalence of H. pylori infection was also associated with family size, education level, and several diet-related factors, such as the number of times cooked rice and potatoes eaten per week, and a family history of stomach diseases. Compared to nonsymptomatic individuals, people with dyspeptic symptoms (nausea, vomiting, and belching) presented a low prevalence of H. pylori infection. No association between H. pylori prevalence and smoking or drinking was found. Using multivariate logistic regression analysis, annual family income and education level were the independent predictors for H. pylori infection.
Conclusion:  High prevalence of H. pylori infection was found in areas with a high risk of gastric cancer and was related to several risk factors. The underlying mechanisms need to be further investigated.     

When Does Gastric Atrophy Develop in Japanese Children?

Background: Long-term Helicobacter pylori infection causes inflammatory sequelae such as atrophy and intestinal metaplasia in the stomach, which is thought to increase the risk of developing gastric malignancy. We previously reported that gastric atrophy can develop in Japanese children with H. pylori infection, predominantly in the antrum. However, detailed data about the age of children with atrophy are largely lacking.
Methods and results: In the present study, 131 children (79 boys) with H. pylori infection were re-analyzed for an association between age and the grade of gastric atrophy. The gastric antrum was histologically evaluated in all 131 patients and the corpus in 46 patients. Grade 2 and 3 antral atrophy was observed in 13 and one patients, respectively: the mean age was 12.1 years. Two patients (11 and 14 years old) had grade 2 corpus atrophy but no patients had grade 3. No significant difference was found in age among patients with grade 0, 1 and 2 or 3 atrophy in the antrum ( p =  .97) and in the corpus ( p =  .59). None of the patients with grade 2 or 3 atrophy had intestinal metaplasia either in the antrum or in the corpus.
Conclusions: The results of the present study require a careful interpretation because of the retrospective analysis. In high-risk countries of gastric cancer, however, eradicating H. pylori in childhood could prove more effective in preventing gastric atrophy, ultimately, the development of cancer.     

Genetic Variation in a4GnT in Relation to Helicobacter pylori Serology and Gastric Cancer Risk

Background:  Helicobacter pylori, a known risk factor of gastric cancer, rarely colonize the deeper portion of normal gastric glands, where the mucus is rich in α-1,4-linked N -acetylglucosamine capped O -glycans, that strongly inhibit H. pylori growth in vitro .
Materials and methods:  We investigated the association between genetic variation in the O -glycan transferase encoding gene ( a4GnT ) and H. pylori infection and gastric cancer risk using a Polish population-based case–control study (273 gastric cancer patients and 377 controls).
Results:  A haplotype at the rs2622694–rs397266 locus was associated with H. pylori infection, with the A-A haplotype associated with a higher risk compared with the most frequent G-G haplotype (odds ratio 2.30; 95% confidence interval 1.35–3.92). The association remained significant after correction for multiple tests (global p value: nominal 0.002, empirical 0.045). Neither this haplotype nor the tagSNPs were associated with overall gastric cancer risk.
Conclusion:  a4GnT genetic variation may be relevant to H. pylori infection, but not to gastric cancer risk.     

Helicobacter pylori-induced epithelial cell signalling in gastric carcinogenesis

Helicobacter pylori represents a highly successful human microbial pathogen that infects the stomach of more than half of the world's population. H. pylori induces gastric inflammation, and the diseases that can follow such infection include chronic gastritis, peptic ulcers and, more rarely, gastric cancer. The reasons why a minority of patients with H. pylori develops gastric cancer could be related to differences in host susceptibility, environmental factors and the genetic diversity of the organism. This review examines the features of H. pylori-induced epithelial cell signalling in gastric diseases. Clinical studies and animal models, and also evidence for H. pylori strain-related differences in gastric epithelial cell proliferation in vivo are discussed. In addition, the mechanisms by which H. pylori triggers hyperproliferative processes and takes direct command of epithelial cell signalling, including activation of tyrosine kinase receptors, cell-cell interactions and cell motility are reviewed.     

Acid, helicobacter and immunity: a new paradigm for oesophagogastric cancer.

Epidemiological evidence has clearly shown a highly significant relationship between Helicobacter pylori infection and the development of duodenal ulcer and distal gastric adenocarcinoma. Despite H. pylori being a common aetiological factor for both disorders, the two disease phenotypes are virtually mutually exclusive. This indicates that the host response to infection has a pivotal role in determining outcome; these disease phenotypes relate to the effect of infection on gastric acid secretion, duodenal ulcer being closely related to sustained acid secretion whereas gastric cancer follows gastric atrophy and impaired gastric acid secretion. Cancer at the oesophageal junction and that associated with Barrett's oesophagus is now the most rapidly increasing tumour in the gastrointestinal tract. The challenge for the next millennium, therefore, is to try and develop methods for identifying patients at risk of developing oesophagogastric cancer. A common feature in the pathogenesis of both gastric and oesophageal adenocarcinoma is inflammation presenting clinically as gastritis and oesophagitis. The pathway from gastritis to gastric atrophy, dysplasia and carcinoma is thought to be a multi-step process, probably triggered by free radicals within the gastric epithelium and increased exposure to luminal carcinogens. However, it has been unclear as to which aspect of the host response determines whether an individual will move along the neoplasia pathway. Recent work has shown that qualitative aspects of the immune environment in the stomach may account for a substantial part of the phenotypic divergence following H. pylori infection. Interleukin-1 beta polymorphisms relate closely to the propensity for an individual to develop distal gastric cancer and maybe useful for predicting risk in family members. In Barrett's oesophagus, we have recently shown that the immune environment may also be important in determining whether an individual will develop cancer. Although we did not find that Barrett's oesophagus was a profoundly inflammatory condition (unlike esophagitis in the squamous epithelium), where there was evidence of inflammation it was qualitatively different from that of oesophagitis in that a Th-2 response with increased expression of IL-4 predominated in Barrett's, whereas a Th-1 proinflammatory response characterised oesophagitis in squamous epithelium. It seems likely that the specific immune environment within Barrett's metaplasia may be an important driver towards dysplasia and carcinoma. Thus, the immune environment in the stomach and esophagus may be critical in determining whether an individual is at risk of developing neoplastic complications of H. pylori infection and gastroesophageal reflux. Identification of the genetic factors which underpin these responses may ultimately result in development of methods to identify individuals at high risk.     

Helicobacter pylori Infection and Family History of Gastric Cancer Decrease Expression of FHIT Tumor Suppressor Gene in Gastric Mucosa of Dyspeptic Patients

Background:  The expression of a fragile histidine triad (FHIT) protein is lost in stomach tumors. The study aimed at determining whether FHIT expression is affected by Helicobacter pylori infection, strain virulence ( vacA and cagA genes) and histopathological changes in the gastric mucosa of patients with functional dyspepsia having first-degree relatives with gastric cancer.
Materials and Methods:  Eighty-eight never-smoking patients with functional dyspepsia were selected for the study, and 48 of them had first-degree relatives with gastric cancer. Bacterial DNA amplification was used to identify H. pylori colonization. The level of FHIT gene expression was determined by qRT-PCR (mRNA) and Western blot (FHIT protein) analyses.
Results:  For patients having first-degree relatives with gastric cancer FHIT expression was lower (mRNA by ca. 40–45% and protein by 30%) compared with the control patients ( p  < .05). H. pylori infection decreased the FHIT mRNA level by 10–35% and the protein level by 10–20%. Bacterial strain vacA (+) cagA (+) lowered FHIT mRNA by ca. 30–35% in the antrum samples of both groups and in corpus samples of patients with first-degree relatives with gastric cancer ( p  < .05). The FHIT mRNA level was twice as high in control H. pylori- negative patients with intestinal metaplasia, compared with those with non-atrophic gastritis.
Conclusions:  The decreased FHIT gene expression associated with hereditary factors and with H. pylori infection, especially with vacA (+) cagA (+)-positive strains, may be related to gastric carcinoma development.     

Helicobacter pylori Immunology and Vaccines

Helicobacter pylori infection causes chronic gastritis, peptic ulcer, and gastric cancer. Colonization of H. pylori in the stomach activates Toll-like and Nod-like receptors to induce not only innate immunity but also adaptive Th1 responses against this organism. Adaptive Th1 response is not sufficient to clear this organism and, as a result, the infection persists. Insufficient adaptive immunity can be explained by poor activation of Toll-like receptors, suppressive effects of bacterial factors, and induction of regulatory T-cell responses. Significant progress in the understanding of innate and adaptive immunity against H. pylori was made during the past year. Recent findings in the fields of vaccines for H. pylori are also reviewed.     

Guidelines for the Management of Helicobacter pylori Infection in Japan: 2009 Revised Edition

Background:  Over the past few years, the profile of Helicobacter pylori infection has changed in Japan. In particular, the relationship between H. pylori and gastric cancer has been demonstrated more clearly. Accordingly, the committee of the Japanese Society for Helicobacter Research has revised the guidelines for diagnosis and treatment of H. pylori infection in Japan.
Materials and Methods:  Four meetings of guidelines preparation committee were held from July 2007 to December 2008. In the new guidelines, recommendations for treatment have been classified into five grades according to the Minds Recommendation Grades, while the level of evidence has been classified into six grades. The Japanese national health insurance system was not taken into consideration when preparing these guidelines.
Results:  Helicobacter pylori eradication therapy achieved a Grade A recommendation, being useful for the treatment of gastric or duodenal ulcer, for the treatment and prevention of H. pylori -associated diseases such as gastric cancer, and for inhibiting the spread of H. pylori infection. Levels of evidence were determined for each disease associated with H. pylori infection. For the diagnosis of H. pylori infection, measurement of H. pylori antigen in the feces was added to the tests not requiring biopsy. One week of proton-pump inhibitor-based triple therapy (including amoxicillin and metronidazole) was recommended as second-line therapy after failure of first-line eradication therapy.
Conclusion:  The revised Japanese guidelines for H. pylori are based on scientific evidence and avoid the administrative restraints that applied to earlier versions .     

Functional Role of Metaplastic Paneth Cell Defensins in Helicobacter pylori-Infected Stomach

Background and Aims:  Chronic gastritis is caused by Helicobacter pylori infection, and gastritis is classified as inflammation, atrophy, and intestinal metaplasia. Detailed pathologic studies have shown that H. pylori settles on the surface of gastric mucosa, and that it is eliminated from metaplastic mucosa. However, its mechanism of natural protection is not well known.
Methods:  Antimicrobial human enteric defensin expression was determined in the RNA and protein levels. Recombinant enteric defensins were produced with a bacterial expression system and their anti- H. pylori activities were assessed by bactericidal assay.
Results:  Human enteric defensin (HD)-5 and HD-6 were detected in Paneth cells, which are observed in the gastric metaplastic mucosa as well as small intestinal epithelia. HD-5 protein was coexpressed with trypsin, which is considered to be an activating enzyme of HD-5. Less H. pylori was observed in the intestinal metaplasia with HD-5 expressing Paneth cells. The recombinant defensins showed killing activity against H. pylori at a low concentration in vitro.
Conclusions:  The human defensins that are expressed in the metaplastic Paneth cells eliminate H. pylori . Metaplastic change may be a purposive development of the human stomach.     

Design and planned analyses of an ongoing randomized trial assessing the preventive effect of Helicobacter pylori eradication on occurrence of new gastric carcinomas after endoscopic resection

BACKGROUND: A causal relationship between Helicobacter pylori infection and gastric cancer has been established. A nonrandomized study has shown eradication of H. pylori after endoscopic resection (ER) of early gastric cancer inhibits development of new carcinomas. SUBJECTS AND METHODS: Eligible subjects are patients with H. pylori infection who are newly diagnosed with early gastric cancer and plan to have ER or who are in the post-resection follow-up phase after ER time of enrollment. Patients are randomly allocated to the eradication or the control arms (no eradication and standard of care). Patients will be evaluated by endoscopy at 0.5, 1, 2, and 3 years after randomization. Diagnosis of a new carcinoma at another site of the stomach is defined as primary endpoint, and recurrence of tumors at the resection site as a secondary endpoint. In addition to intention-to-treat and per-protocol analyses using proportional hazards models, time to recurrence will be compared between treatment and control using multiple logistic regression analyses. In the latter two situations, the models will be adjusted for the factors exerting significant influences on the results. RESULTS: Five hundred and forty-two subjects have been enrolled into the study and are being followed-up. CONCLUSIONS: This study will have the statistical power to demonstrate whether H. pylori eradication therapy exerts any clinically relevant inhibitory effects on occurrence or recurrence of gastric cancer. In addition, it will be able to test the hypothesis that H. pylori infection is a promoter in gastric carcinogenesis.     

Cost-Effectiveness of Eradication of Helicobacter pylori in Gastric Cancer Survivors After Endoscopic Resection of Early Gastric Cancer

Background:  Clinical effectiveness of Helicobacter pylori eradication in gastric cancer survivors after endoscopic resection of early gastric cancer (EGC) was recently established in a randomized controlled trial. We aimed to establish long-term cost-effectiveness in gastric cancer survivors after endoscopic resection of EGC.
Materials and Methods:  A Markov model was constructed to compare the costs and outcomes of the two intervention strategies: (1) eradicate H. pylori after complete resection of EGC by endoscopy (2) do not eradicate. Estimates for variables in the model were obtained by extensive review of published reports. Analyses were made from the Korean public healthcare provider's perspective.
Results:  Base-case analysis indicated H. pylori eradication costs less (US$ 29,780 vs. US$ 30,594) than no eradication, and save more lives (mean life expectancy from eradication: 13.60 years vs. 13.55 years). One-way and three-way sensitivity analyses showed the robustness of the cost-effectiveness results.
Conclusion:  In this selective population with very high risk of developing gastric cancer, H. pylori eradication should be considered for reimbursement with priority to prevent subsequent cancer and also reduce health care cost.     

Epidemiology of Helicobacter pylori Infection

This review summarizes studies on the epidemiology of Helicobacter pylori published in peer-reviewed journals between April 2007 and March 2008. Infection with H. pylori often occurs in childhood, and once established, can persist lifelong if untreated. Prevalence of H. pylori infection is higher in developing countries when compared to developed countries, and can vary by ethnicity, place of birth, and socioeconomic factors even among persons living in the same country. Prevalence of infection is decreasing in many countries due to improvements in sanitation and living standards and the relatively recent movement of populations from rural to urban settings; however, post-treatment recurrence rates of H. pylori infection remain high in developing countries, and in given populations within developed countries. In addition, a number of recent studies have begun to explore the possible link between childhood infection with H. pylori and protection against asthma and allergy.     

Combined serum IgG response to Helicobacter pylori VacA and CagA predicts gastric cancer

Helicobacter pylori is a major factor for the development of gastric cancer. The aim of this study was to define serum antibody patterns associated with H. pylori infection in patients with gastric cancer using a Western blot technique. Serum samples collected from 115 patients with gastric cancer and 110 age- and gender-matched patients without gastrointestinal diseases were tested for IgG antibodies to H. pylori antigens (outer membrane proteins and whole cell preparations). No significant differences were found between patients with and without gastric cancer using outer membrane proteins (82% and 73%, P>0.05) or whole cell antigens (84% and 76%, P>0.05), respectively. The significant differences between patients with and without gastric cancer were associated with bands of 94 kDa (54% and 20%, P<0.001) and 30 kDa (65% and 44%, P<0.01). A combination of antibodies to 85 kDa (VacA) and 120 kDa (CagA) was significantly (P<0.01) more frequent in gastric cancer patients than in patients without gastric cancer. The detection of antibodies to 94- and 30-kDa bands, in association with the determination of serum antibodies to CagA+/VacA+, may have a prospective value in assessment of the risk of developing of gastric cancer.     

Helicobacter pylori: an invading microorganism? A review

In this review we evaluate the pros and cons of Helicobacter pylori invasion of epithelial cells as part of the natural history of H. pylori infection. H. pylori is generally considered an extracellular microorganism. However, a growing body of evidence supports the controversial hypothesis that at least a subset of H. pylori microorganisms has an intracellular (intraepithelial) location. Most significant is the fact that H. pylori invades cultured epithelial cells with invasion frequencies similar to Yersinia enterocolitica and better than Shigella flexneri; furthermore, studies of invasion mechanisms suggest that H. pylori invasion of and survival within epithelial cells is not merely a passive event, but requires active participation of the microorganism. Although many studies of human gastric biopsy specimens have failed to demonstrate any intracellular H. pylori, some studies have revealed a minor fraction of H. pylori inside gastric epithelial cells, with possible linkage to peptic ulceration and epithelial cell damage. In conclusion, these data encourage further research to establish whether intracellular H. pylori does play a role in H. pylori colonization of the human stomach and in peptic ulcer pathogenesis.     

Effect of H. pylori on the expression of TRAIL, FasL and their receptor subtypes in human gastric epithelial cells and their role in apoptosis

BACKGROUND AND AIMS: In the human stomach expression of TNF-related apoptosis inducing ligand (TRAIL) and its receptors and the modulatory role of Helicobacter pylori are not well described. Therefore, we investigated the effect of H. pylori on the expression of TRAIL, FasL and their receptors (TRAIL-R1-R4, Fas) in gastric epithelial cells and examined their role in apoptosis. MATERIALS AND METHODS: mRNA and protein expression of TRAIL, FasL and their receptors were analyzed in human gastric epithelial cells using RT-PCR, Western blot, and immunohistochemistry. Gastric epithelial cells were incubated with FasL, TRAIL and/or H. pylori, and effects on expression, cell viability and epithelial apoptosis were monitored. Apoptosis was analyzed by histone ELISA, DAPI staining and immunohistochemistry. RESULTS: TRAIL, FasL and their receptor subtypes were expressed in human gastric mucosa, gastric epithelial cell primary cultures and gastric cancer cells. TRAIL, FasL and H. pylori caused a time- and concentration-dependent induction of DNA fragmentation in gastric cancer cells with synergistic effects. In addition, H. pylori caused a selective up-regulation of TRAIL, TRAIL-R1 and Fas mRNA and protein expression in gastric cancer cells. CONCLUSIONS: Next to FasL and Fas, TRAIL and all of its receptor subtypes are expressed in the human stomach and differentially modulated by H. pylori. TRAIL, FasL and H. pylori show complex interaction mediating apoptosis in human gastric epithelial cells. These findings might be important for the understanding of gastric epithelial cell kinetics in patients with H. pylori infection.     

Gastric MALT lymphoma and Helicobacter pylori.

Primary gastric low-grade B-cell lymphomas are neoplastic mimics of mucosa associated lymphoid tissue (MALT) as exemplified by Peyer''s patches in the terminal ileum. Architectural and immunophenotypic properties of the neoplastic cells suggest that they originate from MALT-derived marginal zone B-cells. Paradoxically, the normal human stomach is devoid of organized MALT within which a lymphoma can develop. Lymphoid tissue is acquired in the stomach in response to antigenic stimulation, predominantly associated with Helicobacter pylori infection. Studies of patients with low-grade MALT lymphoma have confirmed a high incidence of H. pylori infection and suggest that the infection predates neoplastic transformation. Certain morphological features of MALT lymphomas suggest that the tumor cells remain responsive to antigen drive. Given the close association between gastric MALT lymphoma and H. pylori, it is possible that this organism provides such a drive. In vitro studies have shown that the tumor cells proliferate in a T-cell-dependent way to the presence of H. pylori. Several studies have now demonstrated that eradication of the organism in patients with low-grade gastric MALT lymphoma can result in regression of the tumor. In cases with a high-grade component, the associated low-grade part may regress, but most high-grade gastric MALT lymphomas are unresponsive to this conservative therapy.     

Monocyte and Macrophage Killing of Helicobacter pylori: Relationship to Bacterial Virulence Factors

Background:  Helicobacter pylori infection is an important health problem, as it involves approximately 50% of the world's population, causes chronic inflammatory disease and increases the risk of gastric cancer development. H. pylori infection elicits a vigorous immune response, but this does not usually result in bacterial clearance. We have investigated whether the persistence of H. pylori in the host could be partly due to an inability of macrophages to kill this bacterium.
Materials and Methods:  Monocytes and macrophages isolated from the peripheral blood of normal human controls were infected in vitro with five H. pylori isolates. The isolates were characterized for known H. pylori virulence factors; vacuolating cytotoxin (VacA), the cag pathogenicity island ( cag PAI), urease, and catalase by Western blot and polymerase chain reaction analysis. The ability of primary human monocytes and macrophages to kill each of these H. pylori strains was then defined at various time points after cellular infection.
Results:  The five H. pylori strains showed contrasting patterns of the virulence factors. There were different rates of killing for the bacterial strains. Macrophages had less capacity than monocytes to kill three H. pylori strains. There appeared to be no correlation between the virulence factors studied and differential killing in monocytes.
Conclusions:  Primary human monocytes had a higher capacity to kill certain strains of H. pylori when compared to macrophages. The VacA, cag PAI, urease, and catalase virulence factors were not predictive of the capacity to avoid monocyte and macrophage killing, suggesting that other factors may be important in H. pylori intracellular pathogenicity.