Helicobacter pylori infection induces gastric cancer in mongolian gerbils

Diffuse submucosal cysts of the stomach: report of two cases in association with development of multiple gastric cancers during endoscopic follow up

BACKGROUND

Diffuse submucosal cysts of the stomach have been suggested as a predisposing condition for the development of gastric cancer, especially multiple cancers. We report here two cases of diffuse submucosal cysts of the stomach associated with multiple gastric cancers which were detected during endoscopic follow-up.

METHODS AND RESULTS

The first patient was a 75-year-old man and the second patient was a 72-year-old man. In the first case, we performed an endoscopic examination every year and detected an advanced cancer and two early cancers on the fifth year of the follow up. Because one of these cancers was advanced, we examined the second patient endoscopically every six months. In this patient, we detected two early cancers after 1.5 years follow up.

CONCLUSIONS

We suggest that patients with this disorder should be examined regularly by endoscopy for the detection of gastric cancer, preferably every six months.

How useful is the detection kit for antibody to Helicobacter pylori in urine (URINELISA) in clinical practice?

OBJECTIVE

Increased knowledge of the significance of Helicobacter pylori (H. pylori) infection in gastric disorders has accelerated the trend of screening patients with dyspepsia for its infection. Serological examination of antibody for H. pylori has been widely performed. Recently, a urine-based enzyme-linked immunosorbent assay (URINELISA) kit for detection of antibody for H. pylori has been developed. Accordingly, we evaluated its diagnostic accuracy in clinical practice.

METHODS

Subjects of this study were 132 patients who presented at our university hospital because of dyspeptic symptoms (81 men, 51 women; age, 41.5+/-1.4 yr). 13C urea breath test, blood drawing for serological antibody for H. pylori infection by four different kits, and urine collection for the URINELISA test for detection of the antibody were performed. Diagnostic accuracy of the commercially available antibodies in serum and in urine were investigated using the results of the 13C urea breath test as the gold standard.

RESULTS

Sensitivity, specificity, and accuracy of URINELISA were 86.3% (95% confidence intervals [CI], 76-93%), 91.5% (95% CI, 81-97%), and 88.6% (95% CI, 82-93%), respectively, which were comparable to those of imported serological kits.

CONCLUSIONS

The URINELISA kit for detecting anti-H. pylori antibody in urine provides diagnostic accuracy comparable to that of imported kits for detecting antibodies in serum and is considered to be clinically useful for the diagnosis of H. pylori infection.

Ethanol intake preceding Helicobacter pylori inoculation promotes gastric mucosal inflammation in Mongolian gerbils

BACKGROUND

Mongolian gerbils have been reported to be a suitable model for Helicobacter pylori-associated gastric mucosal injury, including gastric cancer. Although ethanol is known to be one of the harmful substances in the gastric mucosa, the relationship between ethanol and H. pylori infection remains unknown. The aim of the present study is to investigate the effect of ethanol treatment prior to H. pylori inoculation on associated gastric mucosal injury.

METHODS

Male Mongolian gerbils were used for the study. Helicobacter pylori was orally inoculated after 15 h fasting (Hp group). Thirty minutes prior to H. pylori inoculation, a group of gerbils was orally treated with 40% ethanol (20 mL/kg; E + Hp group). Another group of animals was treated either with H. pylori culture media alone (controls) or with 40% ethanol plus culture media (E group). Gerbils were killed 2, 4 or 12 weeks after H. pylori inoculation. Helicobacter pylori infection was confirmed by both histological examination and serological tests. Mucosal damage was evaluated histologically according to the modified Sydney system.

RESULTS

Although in the controls and E group no significant change to the gastric mucose was observed, persistent H. pylori infection was seen in the mucosa and mucosal leucocyte infiltration and severe epithelial damage was observed in the Hp and E + Hp groups after 4 weeks. The histological scores for polymorphonuclear cell infiltration and myeloperoxidase activity were higher in the E + Hp group at 4 weeks than in the Hp group (P < 0.05).

CONCLUSIONS

Ethanol intake preceding H. pylori inoculation could promote the progression of gastric mucosal inflammation in Mongolian gerbils.

Association of Helicobacter pylori infection with gastric carcinoma: a meta-analysis

OBJECTIVE

As conflicting studies have recently been published, we aimed to determine if Helicobacter pylori (H. pylori) infection is associated with gastric adenocarcinoma.

METHODS

This was a meta-analysis of observational epidemiological studies.

RESULTS

A total of 42 studies met the selection criteria and were categorized by the type of study design: eight cohort and 34 case-control studies. The pooled odds ratio for H. pylori in relation to gastric carcinoma was 2.04 (95% CI: 1.69-2.45). Both patient age (OR 0.77, 95% CI: 0.68-0.89) and intestinal type cancers (OR 1.14, 95% CI: 1.05-1.25) were independent effect modifiers. Analysis of other effect modifiers showed no relationship with female gender (OR 0.76, 95% CI: 0.64-0.89), stage of cancer (advanced %) (OR 1.12, 95% CI: 0.88-1.43), anatomical location (cardia %) (OR 1.54, 95% CI: 0.32-7.39) or cohort (nested case-control) studies (OR 1.72, 95% CI: 0.32-9.17). There was significant heterogeneity among the studies (tau2 = 149; p < 0.001). The quality of the studies varied considerably, with the majority of excellent studies producing positive results and the very poor to moderate studies producing mixed results.

CONCLUSIONS

H. pylori infection is associated with a 2-fold increased risk of developing gastric adenocarcinoma.

Molecular response of gastric epithelial cells to Helicobacter pylori-induced cell damage

Infection with the Gram-negative bacterium Helicobacter pylori leads to different clinical and pathological outcomes in humans, including chronic gastritis, peptic ulcer disease and adenocarcinoma of the stomach. H. pylori-induced damage to gastric mucosal cells is controlled by bacterial virulence factors encoded by genes of the cag pathogenicity island, which trigger the inflammatory response of the host through the activation of nuclear factor kappaB-dependent gene transcription. Also, H. pylori infection impairs the processes of gastric mucosal healing through inhibition of epidermal growth factor receptor-dependent signal transduction pathways and induction of apoptosis. H. pylori infection may influence the progression from chronic gastritis to gastric adenocarcinoma by stimulating cell proliferation and growth factor expression, inhibiting apoptosis and increasing the DNA mutation rate of infected gastric mucosa.

Cellular Immune Responses Are Essential for the Development of Helicobacter felis-Associated Gastric Pathology

The bacteria Helicobacter pylori is a major human pathogen that infects over half of the world’s population. Infection initiates a series of changes in the gastric mucosa, beginning with atrophic gastritis and leading in some patients to peptic ulcer disease, mucosa-associated lymphomas, and gastric adenocarcinoma. Although this cascade of events clearly occurs, little is known about the role of the host immune response in disease progression. We have utilized the C57BL/6 Helicobacter felis mouse model to critically analyze the role of the adaptive immune response in the development of Helicobacter-associated gastric pathology. Infection of B and T cell-deficient RAG-1−/− mice or T cell-deficient TCRβδ−/− mice with H. felis resulted in high levels of colonization, but no detectable gastric pathology. Conversely, infection of B cell-deficient μMT mice resulted in severe gastric alterations identical with those seen in immunocompetent C57BL/6-infected mice, including gastric mucosal hyperplasia and intestinal metaplasia. These results demonstrate that the host T cell response is a critical mediator of Helicobacter-associated gastric pathology, and that B cells and their secreted Abs are not the effectors of the immune-mediated gastric pathology seen after H. felis infection. These results indicate that in addition to specific Helicobacter virulence factors, the host immune response is an important determinant of Helicobacter-associated disease.

The role of gastric carditis in metaplasia and neoplasia at the gastroesophageal junction

Adenocarcinomas at the gastroesophageal junction appear to arise from foci of intestinal metaplasia that develop either in the distal esophagus or the proximal stomach (the gastric cardia). Metaplasia is usually a consequence of chronic inflammation, and it is logical to assume that intestinal metaplasia at the gastroesophageal junction develops as a result of chronic inflammation in the epithelia that normally line the junction region. Intestinal metaplasia in the esophagus is known to be a sequela of chronic inflammation in squamous epithelium caused by gastroesophageal reflux disease, whereas intestinal metaplasia in the distal stomach is often a consequence of chronic gastritis caused by Helicobacter pylori infection. For the gastric cardia, the contributions of gastroesophageal reflux disease, H. pylori infection, and other factors to inflammation, metaplasia, and neoplasia are not clear. If physicians are to develop meaningful preventive strategies and specific therapies for tumors of the proximal stomach, a clear understanding of pathogenesis is important. Recent studies on pathogenetic factors for inflammation in cardiac epithelium (gastric carditis) have yielded contradictory results, perhaps because of fundamental differences in the techniques used by different investigators for identifying and sampling the gastric cardia. This report explores the roots of the controversy regarding the role of gastric carditis in the development of metaplasia and neoplasia at the gastroesophageal junction and suggests practical guidelines for biopsy protocols to be used in future studies that will be necessary to resolve these disputes.

Personal review: Helicobacter pylori, NSAIDs and cognitive dissonance

Helicobacter pylori and non-steroidal anti-inflammatory drugs (NSAIDs) each cause peptic ulcers but by different mechanisms. As a result, the effect of both of these risk factors together is not a synergistic enhancement of injury, ulceration or rates of complications. Indeed, there are circumstances under which patients infected with H. pylori are less prone to NSAID-induced ulcers than those who are not infected or who have undergone eradication treatment. This may be because of opposite effects on gastric mucosal prostaglandin synthesis or for other reasons. Reluctance to accept that there may be specific circumstances where H. pylori is beneficial may arise because of the psychological process of cognitive dissonance.

Helicobacter pylori virulence and genetic geography

Isolated for the first time in 1982 from human gastric biopsy, Helicobacter pylori is responsible for gastritis, peptic ulcer, and gastric cancer. A pathogenicity island acquired by horizontal transfer, coding for a type IV secretion system, is a major determinant of virulence. The infection is now treated with antibiotics, and vaccines are in preparation. The geographic distribution suggests coevolution of man and Helicobacter pylori.

Poliovirus replicons encoding the B subunit of Helicobacter pylori urease elicit a Th1 associated immune response

The development of a vaccine for Helicobacter pylori is a key strategy for reducing the worldwide prevalence of H. pylori infection. Although immunization with recombinant B subunit of H. pylori urease (ureB) has yielded promising results, for the most part, these studies relied on the use of strong adjuvant, cholera toxin, precluding the use in humans. Thus, the development of new vaccine strategies for H. pylori is essential. Previous studies from our laboratory have described a vaccine vector based on poliovirus in which foreign genes are substituted for the poliovirus capsid genes. The genomes encoding foreign proteins (replicons) are encapsidated into authentic poliovirions by providing the capsids in trans. To test the utility of replicons as a vaccine vector for H. pylori, a replicon was constructed which encodes ureB. Expression of ureB in cells from the replicon was demonstrated by metabolic labeling followed by immunoprecipitation with anti-urease antibodies. To investigate the immunogenicity of the replicons, mice containing the transgene for the receptor for poliovirus were immunized via the intramuscular route. Mice given three doses of replicons did not develop substantial antibodies to ureB as determined by Western blot analysis using lysates from H. pylori. In contrast, mice given two doses of replicon followed by a single injection of recombinant ureB developed serum antibodies to ureB which were predominately IgG2a. Splenic lymphocytes from mice immunized with replicons alone, or replicons plus recombinant ureB produced abundant interferon-gamma and no detectable interleukin-4 upon stimulation with recombinant ureB. These results establish that poliovirus replicons encoding H. pylori ureB are immunogenic and induce primarily a T helper 1 associated immune response.

Helicobacter pylori infection enhances glandular stomach carcinogenesis in Mongolian gerbils treated with chemical carcinogens

Helicobacter pylori (Hp) is thought to be a stomach carcinogen from epidemiological findings. To determine the effects of infection with the bacteria on experimental carcinogenesis, a study of the glandular stomach of Mongolian gerbils (MGs) was performed. Male MGs were treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by inoculation with Hp or infected with Hp followed by N-methyl-N'-nitro-N-nitrosoguanidine administration. Animals were killed at week 50, and their excised stomachs underwent microbiological and histopathological examinations. In addition, a serological investigation was performed. The incidences of adenocarcinomas were significantly higher in animals treated with 60 or 300 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 10 weeks followed by Hp inoculation or Hp followed by 20 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 30 weeks than in the respective controls. Moreover, tumour-bearing animals had higher titres of anti-Hp antibodies than tumour-free animals. Of interest was the finding that a dose of 100 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine given to infected gerbils eradicated the Hp in about half the animals, with a concomitant reduction in the promoting effect. No tumours were found in animals infected with Hp without N-methyl-N'-nitro-N-nitrosoguanidine or non-treated gerbils. Hp infection enhances glandular stomach carcinogenesis in MGs treated with N-methyl-N'-nitro-N-nitrosoguanidine. Animals with high titres of anti-Hp antibodies are at greatest risk of developing neoplasms.

Review article: the role of inflammation in the pathogenesis of gastric cancer

Helicobacter pylori induces infiltration of the gastric mucosa by polymorphonuclear cells and macrophages, as well as T and B lymphocytes. Paradoxically, this robust immune/inflammatory response cannot clear the infection, and thus leaves the host prone to complications resulting from chronic inflammation. One adverse consequence of this inflammatory response may be gastric cancer, as inflammation has been implicated in the development of intestinal metaplasia and mutations in oncogenes that precede the development of gastric adenocarcinoma. The gastric inflammatory response is affected somewhat, by the strain of H. pylori that infects the host. Thus, the more severe clinical manifestation associated with some strains may be attributed to the higher grade of inflammation that they induce. Both H. pylori and cytokines induced during infection can stimulate the recruitment and activation of inflammatory cells including neutrophils and macrophages. When activated, these cells produce inflammatory mediators that include reactive oxygen species (ROS). These mediators impart an oxidative stress on the cells in the immediate vicinity, in this case, the gastric epithelium. Normally, oxidative stress is neutralized by natural antioxidants such as vitamin C, however, levels of this antioxidant in the gastric juice are decreased during infection. The increased levels of oxidants and decreased antioxidants create a stress that can change many processes in the gastric epithelium. For example, an accumulation of intracellular ROS regulates the expression of many genes and can induce DNA damage. Point mutations in the DNA that disrupt the expression and function of genes that inhibit cell growth (i.e. p53) are believed to contribute to the pathogenesis of gastric cancer. Several studies suggest that epithelial cell turnover is affected by the inflammatory response to H. pylori. This notion is supported by studies describing an increase in both epithelial cell proliferation, as well as cell death by apoptosis, in response to infection. Apoptosis is a regulated process of cell death that is triggered by H. pylori as well as various inflammatory mediators, including tumour necrosis factor and interferon-gamma. Activated T-cells also kill gastric epithelial cells directly. Moreover, the host response increases the expression of receptors for H. pylori and thus increases bacterial binding and the induction of apoptosis by the bacteria. There are several other immune/inflammatory responses that contribute to epithelial cell damage mucosa and the pathogenesis of gastric cancer. For example, gastric B cells produce autoreactive antibodies that bind to gastric epithelial cells. As a consequence of this antigen-antibody complex formation, complement becomes activated suggesting that some of the inflammation and epithelial cell damage is attributable to immune-complex formation. Epithelial cell death can then stimulate the proliferative response of epithelial cell precursors. In summary, the proposed model may explain how the gastric inflammatory response contributes to the pathogenesis of cancer. This model raises the possibility that it could be preferable to identify the patients at highest risk of developing gastric cancer and then apply an intervention that eliminates the infection and inflammatory response. Alternatively, clinical interventions should at least attenuate the oxidative stress that is directly attributed to inflammation. These mechanisms have to be examined in the paediatric population.

Review article: exploring the link between Helicobacter pylori and gastric cancer

Cancer of the distal stomach, both of the intestinal and diffuse type, is strongly associated with Helicobacter pylori colonization. This bacterium causes chronic active inflammation of the gastric mucosa in the majority of colonized subjects. In a considerable number of them, this will eventually lead to a loss of gastric glands, and thus the establishment of atrophic gastritis, which is associated with the development of intestinal metaplasia and dysplasia. Development of atrophy and metaplasia of the gastric mucosa are thus strongly associated with H. pylori infection, instead of a direct and inevitable consequence of ageing. Approximately 40-50% of infected subjects develop these conditions, but they are rare in non-infected subjects. The presence of these consecutive disorders leads to a 5-90-fold increased risk for cancer of the distal stomach, in particular of the intestinal type. This sequence explains the increased risk for gastric cancer in H. pylori-infected subjects, as has been shown in various cross-sectional and longitudinal studies. In a combined analysis of three longitudinal studies, a significant trend was observed towards an increased odds ratio with longer intervals between (retrospective) serological diagnosis of H. pylori infection and observation of gastric cancer, this risk being more than eight-fold increased if the interval had been at least 15 years. This is thought to reflect development of atrophic gastritis and intestinal metaplasia with loss of H. pylori colonization in the years prior to development of cancer. Atrophic gastritis and gastric cancer thus appear closely associated with the presence of H. pylori, yet not all infected subjects will eventually develop atrophy and only a small minority develop gastric cancer. Factors that influence the risks for atrophy and cancer in the presence of infection may be related to the time that infection occurred and to characteristics of the bacterial strain and the host. Evidence for the role of these factors is now increasing. Recognition of the causal role of H. pylori in the induction of gastric cancer theoretically presents tools for cancer prevention. The efficacy of screening and bacterial eradication for prevention of distal gastric cancer is being studied in a number of large-scale intervention studies in different populations. It is hoped that these studies will also provide answers to the potential preventive role of H. pylori colonization in the development of gastro-oesophageal reflux disease and associated conditions, in particular development of cancer of the proximal stomach. Infection with H. pylori plays an important role in the aetiology of atrophic gastritis and gastric cancer. Studies suggest an eight-fold increased risk for both conditions in the presence of infection. Factors that influence the risk for both conditions in the presence of infection are the age at which infection occurred and the presence of cagA as a marker for more pathogenetic H. pylori strains. The efficacy and side-effects of intervention for the prevention of distal gastric cancer has yet to be established.

Coexistence of Helicobacter pylori spiral and coccoid forms in experimental mice

AIM: To infect mice with Helicobacter pylori and detect immune response against two form of H. pylori.

METHODS: An isolate of H. pylori obtained from a patient with gastric cancer was used to infect mice. Fifty mice were divided into eight groups. Two groups served as negative control without any inoculation and internal negative control with 0.5 M NaHCO₃ and brain heart infusion (HBI), respectively. Mice in each experimental group were first inoculated with 0.5 M NaHCO₃ and then H. pylori suspension for 3 times at a 2-d interval. Mice from controls and infectious groups were sacrificed at a weekly interval postinfection. Gastric samples were trimmed, inoculated onto chocolate blood agar and then incujbated in microaerophilic atmosphere at 37¡æ for 14 d. Sera were examined for immunoglobulins against H. pylori spiral and coccoid antigens by ELISA.

RESULTS: After inoculation H. pylori was isolated in one mouse from one week postinfection. No H. pylori was detected in control mice. However, urease test was positive in 50% (5/10) control mice, 70% (7/10) mice inoculated with NaHCO₃ and BHI and 77% (23/30) mice infected with H. pylori. The systemic immune responses of the mice to H. pylori strain were determined by ELISA. The mice showed immune responses to both H. pylori spiral and coccoid antigens one week after infection with H. pylori. The peak mean absorbances of antibodies against spiral and coccoid forms were four weeks postinfection which showed 6 and 18 times higher than that of negative control group respectively (P < 0.01).

CONCLUSION: Spiral and coccoid forms of H. pylori coexist in experimental mice studied.