CagA seropositivity associated with development of gastric cancer in a Japanese population

Hereditary Gastric Cancer Is Linked With Hereditary Breast and Ovarian Cancer

Background

Helicobacter pylori (H. pylori), a bacterium which chronically infects the stomach of approximately half the world's population, is a risk factor for the development of gastric cancer (GC). However, the underlying mechanism whereby H. pylori infection induces GC development remains unclear. Intermittent injection of the H. pylori cytotoxin-associated gene A antigen (CagA) protein into its host cell inhibits nuclear translocation of BRCA1/BRCA2, DNA repair proteins involved in the development of breast cancer/ovarian cancer. Interestingly, hereditary breast and ovarian cancer (HBOC) syndrome is associated with GC development. Here, we aimed to clarify the molecular link between H. pylori infection, BRCA1/2 pathogenic variants (PVs), GC and higher GC incidence in HBOC families.

Methods

We retrospectively reviewed data from Japanese patients undergoing precision treatment using cancer genomic medicine.

Results

We found a higher GC incidence in HBOC families having germline pathogenic variants (GPVs) of BRCA1/2 (2.95% vs. 0.78% in non-HBOC families). Next, we found that 96.1% of H. pylori-infected patients received cancer genomic medicine for advanced GC, and > 16% advanced GC patients had gBRCA2 PVs. Furthermore, expressing wild-type BRCA1/2 in Gan mice (a mouse model of human GC) inhibited GC development. Thus, gBRAC1/2 PVs and H. pylori infection synergistically increase the risk of GC development.

Conclusion

Our study highlights the need to investigate the potential of therapeutic agents against BRCA1/2 PVs to avoid the development of GC in HBOC families. In addition, our results suggest that poly (ADP-ribose) polymerase (PARP) inhibitors could potentially inhibit GC development and progression with gBRCA1/2 PVs.

Bacteria-Mediated Oncogenesis and the Underlying Molecular Intricacies: What We Know So Far

Cancers are known to have multifactorial etiology. Certain bacteria and viruses are proven carcinogens. Lately, there has been in-depth research investigating carcinogenic capabilities of some bacteria. Reports indicate that chronic inflammation and harmful bacterial metabolites to be strong promoters of neoplasticity. Helicobacter pylori-induced gastric adenocarcinoma is the best illustration of the chronic inflammation paradigm of oncogenesis. Chronic inflammation, which produces excessive reactive oxygen species (ROS) is hypothesized to cause cancerous cell proliferation. Other possible bacteria-dependent mechanisms and virulence factors have also been suspected of playing a vital role in the bacteria-induced-cancer(s). Numerous attempts have been made to explore and establish the possible relationship between the two. With the growing concerns on anti-microbial resistance and over-dependence of mankind on antibiotics to treat bacterial infections, it must be deemed critical to understand and identify carcinogenic bacteria, to establish their role in causing cancer.

Intracellular Presence of Helicobacter pylori and Its Virulence-Associated Genotypes within the Vaginal Yeast of Term Pregnant Women

BACKGROUND

Helicobacter pylori transmission routes are not entirely elucidated. Since yeasts are postulated to transmit this pathogen, this study aimed to detect and genotype intracellular H. pylori harbored within vaginal yeast cells.

METHODS

A questionnaire was used to determine risk factors of H. pylori infection. Samples were seeded on Sabouraud Dextrose Agar and horse blood-supplemented Columbia agar. Isolated yeasts were identified using and observed by optical microscopy searching for intra-yeast H. pylori. Total yeast DNA, from one random sample, was extracted to search for H. pylori virulence genes by PCR and bacterial identification by sequencing.

RESULTS

43% of samples contained yeasts, mainly Candida albicans (91%). Microscopy detected bacteria such as bodies and anti-H. pylori antibodies binding particles in 50% of the isolated yeasts. Total DNA extracted showed that 50% of the isolated yeasts were positive for H. pylori 16S rDNA and the sequence showed 99.8% similarity with H. pylori. In total, 32% of H. pylori DNA positive samples were cagA+ vacAs1a vacAm1 dupA-. No relationship was observed between possible H. pylori infection risk factors and vaginal yeasts harboring this bacterium.

CONCLUSION

H. pylori having virulent genotypes were detected within vaginal yeasts constituting a risk for vertical transmission of this pathogen.

Development of Helicobacter pylori Whole-Proteome Arrays and Identification of Serologic Biomarkers for Noncardia Gastric Cancer in the MCC-Spain Study

BACKGROUND

Helicobacter pylori (H. pylori) is a bacterial carcinogen and the leading risk factor for noncardia gastric cancer (NCGC). Detecting antibodies against specific H. pylori proteins in peripheral blood can be applied to characterize infection and determine disease associations. Most studies analyzing the association between H. pylori infection and gastric cancer have focused on previously identified antigens, predominantly the virulence factor cytotoxin-associated gene A (CagA). Selecting antigens in an unbiased approach may, however, allow the identification of novel biomarkers.

METHODS

Using a combination of multiple spotting technique and cell-free, on-chip protein expression, we displayed the H. pylori genome (strain 26695) on high-density microarrays. Immunogenic proteins were identified by serum pool incubations and henceforth analyzed in individual samples. To test its applicability, we used sera from a multicase-control (MCC)-Spain study. Serologic responses between NCGC cases and controls were assessed by conditional logistic regression estimating ORs and 95% confidence intervals.

RESULTS

We successfully expressed 93% of the 1,440 H. pylori open reading frames in situ. Of these, 231 (17%) were found to be immunogenic. By comparing 58 NCGC cases with 58 matched controls, we confirmed a higher seroprevalence of CagA among cases (66%) than controls (31%). We further identified a potential novel marker, the Helicobacter outer membrane protein A (HopA).

CONCLUSIONS

In this study, we provide evidence that our H. pylori whole-proteome microarray offers a platform for unbiased de novo identification of serologic biomarkers.

IMPACT

Given its versatile workflow, antibody responses against other H. pylori strains and possible associations with diverse H. pylori-related outcomes can be systematically analyzed.

Racial Differences in Helicobacter pylori CagA Sero-prevalence in a Consortium of Adult Cohorts in the United States

BACKGROUND

Prevalence of Helicobacter pylori (H. pylori) infection, the main risk factor for gastric cancer, has been decreasing in the United States; however, there remains a substantial racial disparity. Moreover, the time-trends for prevalence of CagA-positive H. pylori infection, the most virulent form, are unknown in the U.S.

POPULATION

We sought to assess prevalence of CagA-positive H. pylori infection over time by race in the United States.

METHODS

We utilized multiplex serology to quantify antibody responses to H. pylori antigens in 4,476 participants across five cohorts that sampled adults from 1985 to 2009. Using log-binomial regression models, we calculated prevalence ratios and 95% confidence intervals for the association between H. pylori-CagA sero-prevalence and birth year by race.

RESULTS

African Americans were three times more likely to be H. pylori-CagA sero-positive than Whites. After adjustment, H. pylori-CagA sero-prevalence was lower with increasing birth year among Whites (P trend = 0.001), but remained stable for African Americans. When stratified by sex and education separately, the decline in H. pylori-CagA sero-positivity among Whites remained only for females (P trend < 0.001) and was independent of educational attainment. Among African Americans, there was no difference by sex; furthermore, sero-prevalence increased with increasing birth year among those with a high school education or less (P = 0.006).

CONCLUSIONS

Among individuals in the United States born from the 1920s to 1960s, H. pylori-CagA sero-prevalence has declined among Whites, but not among African Americans.

IMPACT

Our findings suggest a widening racial disparity in the prevalence of the most virulent form of H. pylori, the main cause of gastric cancer.

Epitope peptides of Helicobacter pylori CagA antibodies from sera by whole-peptide mapping

BACKGROUND

Helicobacter pylori CagA has been found to be immuno-dominant protein and utilized for the diagnosis of the infection with cagA-positive strains. It is important to characterize the peptide epitopes capable of detecting serum anti-CagA antibodies to understand CagA immunogenicity.

METHODS

Sera from 171 Japanese patients were subjected for the epitope mapping study. Eighty seven peptides were designed from the CagA consensus sequence and were used for ELISA protocol to test the serum samples. The reacting anti-CagA IgG amounts to specific peptides were measured and compared.

RESULTS

The study revealed a strong reactivity of two peptides (c7-NNTEPIYAQVNKKKAGQAT and c8-AGQATSPEEPIYAQVAKKV) in H. pylori-infected group. Interestingly, these two peptides contained the well-known EPIYA-A and EPIYA-B region, respectively, which are two out of three CagA phosphorylation domains. Tyrosine-phosphorylation of these peptides reduced their reactivity in most sera. Moreover, additional peptides' mapping and chimeric-peptides' experiments indicated that the amino acids (QV and KK) accommodated in right-side flanking regions of both EPIYA-motifs were essential for their strong reactivity, whereas the third EPIYA-motif containing peptide (c12-GRSASPEPIYATIDFDEA) with differing flanking amino acids was not reactive in most cases.

CONCLUSIONS

Our results suggest that the amino acid sequences constituted in the two reactive peptides are the important immunogenic regions of CagA which would be useful to develop next-generation peptide-based diagnostic assays.

Differences in Helicobacter pylori and CagA antibody changes after eradication between subjects developing and not developing gastric cancer

We evaluated serological Helicobacter pylori and cytotoxin-associated gene A (CagA) antibodies and endoscopic atrophy after eradication to identify factors predicting post-eradication gastric cancer development. Thirty-five patients with successful eradiation were divided into the post-eradication gastric cancer (13 cases) and non-gastric cancer (22 cases) groups. Serum Helicobacter pylori and CagA antibody titers and endoscopic atrophy before and six years after eradication were examined. Median Helicobacter pylori antibody titers had decreased significantly from baseline at 0.5–2 years after eradication in both groups (gastric cancer group, from 39.0 to 11.0 U/ml, p = 0.011; non-gastric cancer group, from 29.6 to 4.97 U/ml, p<0.001), but were significantly higher in the gastric cancer than in the non-gastric cancer group (p = 0.029). Median serum CagA antibody titers had also decreased significantly at 0.5–2 years after eradication (gastric cancer group, from 6.35 to 3.23 U/ml, p = 0.028; non-gastric cancer group, from 9.88 to 1.21 U/ml, p = 0.0045). Serum CagA in each group showed no significance. Endoscopic atrophy improved significantly after eradication in the non-gastric cancer, but not the gastric cancer, group (p = 0.0007). In conclusion, changes in Helicobacter pylori and CagA antibody titers and endoscopic atrophy after eradication might be useful as predictive factors for post-eradication gastric cancer.

Epidemiology of Helicobacter pylori and CagA-Positive Infections and Global Variations in Gastric Cancer

Gastric cancer is a major health burden and is the fifth most common malignancy and the third most common cause of death from cancer worldwide. Development of gastric cancer involves several aspects, including host genetics, environmental factors, and Helicobacter pylori infection. There is increasing evidence from epidemiological studies of the association of H. pylori infection and specific virulence factors with gastric cancer. Studies in animal models indicate H. pylori is a primary factor in the development of gastric cancer. One major virulence factor in H. pylori is the cytotoxin-associated gene A (cagA), which encodes the CagA protein in the cag pathogenicity island (cag PAI). Meta-analysis of studies investigating CagA seropositivity irrespective of H. pylori status identified that CagA seropositivity increases the risk of gastric cancer (OR = 2.87, 95% CI: 1.95⁻4.22) relative to the risk of H. pylori infection alone (OR = 2.31, 95% CI: 1.58⁻3.39). Eradicating H. pylori is a strategy for reducing gastric cancer incidence. A meta-analysis of six randomised controlled trials (RCTs) suggests that searching for and eradicating H. pylori infection reduces the subsequent incidence of gastric cancer with a pooled relative risk of 0.66 (95% CI: 0.46⁻0.95). The introduction in regions of high gastric cancer incidence of population-based H. pylori screening and treatment programmes, with a scientifically valid assessment of programme processes, feasibility, effectiveness and possible adverse consequences, would impact the incidence of H. pylori-induced gastric cancer. Given the recent molecular understanding of the oncogenic role of CagA, targeting H. pylori screening and treatment programmes in populations with a high prevalence of H. pylori CagA-positive strains, particularly the more oncogenic East Asian H. pylori CagA strains, may be worth further investigation to optimise the benefits of such strategies.

From inflammation to gastric cancer: Role of Helicobacter pylori

Gastric cancer is a multifactorial disease and a leading cause of mortality and the risk factors for this include environmental factors and factors that influence host-pathogen interaction and complex interplay between these factors. Gastric adenocarcinomas are of two types, namely intestinal and diffuse type, and Helicobacter pylori (H. pylori) infection has been suspected of being causally linked to the initiation of chronic active gastritis, which leads to adenocarcinoma of the intestinal type. Even though most individuals with H. pylori infection do not show any clinical symptoms, long-term infection leads to inflammation of gastric epithelium and approximately 10% of infected patients develop peptic ulcers and 1–3% of patients develop gastric adenocarcinoma. Among the several mechanisms involved in tumorigenesis, CagA and peptidoglycan of H. pylori, which enter the infected gastric epithelial cells play an important role by triggering oncogenic pathways. Inflammation induced by H. pylori in gastric epithelium, which involves the cyclooxygenase-2/prostaglandin E2 pathway and IL-1β, is also an important factor that triggers chronic active gastritis and adenocarcinoma. H. pylori infection induced oxidative stress and dysregulated E-cadherin/β-catenin/p120 interactions and function also play a critical role in tumorigenesis. Environmental and dietary factors, in particular salt intake, are known to modify the pathogenesis induced by H. pylori. Gastric cancer induced by H. pylori appears to involve several mechanisms, making this mode of tumorigenesis a highly complicated process. Nevertheless, there are many events in this tumorigenesis that remain to be clarified and investigated.

Clinical relevance of Helicobacter pylori vacA and cagA genotypes in gastric carcinoma

Helicobacter pylori infection is the major etiological factor of gastric carcinoma. This disease is the result of a long, multistep, and multifactorial process, which occurs only in a small proportion of patients infected with H. pylori. Gastric carcinoma development is influenced by host genetic susceptibility factors, environmental factors, and H. pylori virulence. H. pylori is genetically highly variable, and variability that affects H. pylori virulence factors may be useful to identify strains with different degrees of pathogenicity. This review will focus on VacA and CagA that have polymorphic regions that impact their functional properties. The characterization of H. pylori vacA and cagA-associated could be useful for identifying patients at highest risk of disease, who could be offered H. pylori eradication therapy and who could be included in programs of more intensive surveillance in an attempt to reduce gastric carcinoma incidence.

Helicobacter pylori-induced IL-1β secretion in innate immune cells is regulated by the NLRP3 inflammasome and requires the cag pathogenicity island

Infection with the gram-negative bacterium Helicobacter pylori is the most prevalent chronic bacterial infection, affecting ∼50% of the world's population, and is the main risk factor of gastric cancer. The proinflammatory cytokine IL-1β plays a crucial role in the development of gastric tumors and polymorphisms in the IL-1 gene cluster leading to increased IL-1β production have been associated with increased risk for gastric cancer. To be active, pro-IL-1β must be cleaved by the inflammasome, an intracellular multiprotein complex implicated in physiological and pathological inflammation. Recently, H. pylori was postulated to activate the inflammasome in murine bone marrow-derived dendritic cells; however, the molecular mechanisms as well as the bacterial virulence factor acting as signal 2 activating the inflammasome remain elusive. In this study, we analyzed the inflammasome complex regulating IL-1β upon H. pylori infection as well as the molecular mechanisms involved. Our results indicate that H. pylori-induced IL-1β secretion is mediated by activation of the nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 inflammasome. We also show that reactive oxygen species, potassium efflux, and lysosomal destabilization are the main cellular mechanisms responsible of nucleotide-binding oligomerization domain family, pyrin domain-containing 3 inflammasome activation upon H. pylori infection, and identify vacuolating cytotoxin A and cag pathogenicity island as the bacterial virulence determinants involved. Moreover, in vivo experiments indicate an important role for the inflammasome in the onset and establishment of H. pylori infection and in the subsequent inflammatory response of the host.

Serum Helicobacter pylori CagA antibody may not be used as a tumor marker for diagnosing gastric cancer in east Asian countries

Gastric cancer (GC) is a highly malignant cancer with increasing incidence and mortality worldwide. Serum Helicobacter pylori CagA antibody has been widely reported to play an important role in diagnosing GC. However, published data on this subject are inconclusive. Therefore, we performed a meta-analysis to evaluate the sensitivity and specificity of serum H. pylori CagA antibody in the diagnosis of GC. We conducted a comprehensive search to identify eligible related studies, in which the pooled sensitivity, specificity, diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curves could be determined. A total of 12 studies including 1,524 cases and 3,324 controls who fulfilled all of the inclusion criteria were included for analysis. The summary estimates for serum H. pylori CagA antibody in the diagnosis of GC in these studies were pooled sensitivity 0.71 (95 % CI 0.69-0.73), specificity 0.40 (95 % CI 0.39-0.42), DOR 2.11 (95 % CI 1.55-2.8), and the area under the curve was 0.636. Our meta-analysis showed that serum H. pylori CagA antibody should not be used for detecting GC.

Serum Helicobacter pylori CagA antibody titer as a useful marker for advanced inflammation in the stomach in Japan

BACKGROUND AND AIM

Subjects infected with Helicobacter pylori containing cagA do not always induce serum CagA antibody. Our previous meta-analysis showed that serum CagA seropositivity was associated with gastric cancer even in East Asian countries. However, it remains unclear why serum CagA-positive status is associated with gastric cancer. In this study, we aimed to examine the relationship between anti-CagA antibody titer and the levels of pepsinogen (PG), and histological score.

METHODS

Eighty-eight H. pylori-positive Japanese patients with gastritis were included. Serum CagA antibody titer, PG I, and PG II were evaluated by ELISA. Histological scores were evaluated according to Update Sydney System. CagA expression was examined by immunoblot.

RESULTS

Seroprevalence of CagA antibody was found in 75.0%. Interestingly, serum CagA antibody titer was significantly correlated with PG I and PG II levels (P = 0.003 and 0.004, respectively). Serum CagA antibody titer was also significantly correlated with mucosal inflammation in the corpus (P = 0.04). On the other hand, bacterial density was not related with CagA antibody titer. CagA expression level of the strains was irrespective of the status of PG and serum CagA antibody.

CONCLUSIONS

Subjects with higher serum CagA antibody titer can be considered as high-risk population for the development of gastric cancer from the point of strong gastric inflammatory response even in Japan. Host recognition rather than bacterial colonization might be associated with the difference of serum CagA antibody titer.

Helicobacter pylori CagA and VacA genotypes and gastric phenotype: a meta-analysis

BACKGROUND

CagA+ and vacuolizing cytotoxin (VacA)-specific strains of Helicobacter pylori have been associated with different risks for developing gastric lesions. We aim to summarize a possible association between these genotypes and the risk for developing different gastric phenotypes.

MATERIALS AND METHODS

A MEDLINE database (PubMed) search was performed and a meta-analysis conducted.

RESULTS

Forty-four studies were retrieved, all with either a case-control (n=13) or cross-sectional (n=31) design, including 17 374 patients. CagA positivity was associated with an increased risk for gastric cancer [odds ratio (OR) 2.09 (95% confidence interval (CI), 1.48-2.94)] compared with that in individuals without gastric lesions [OR 2.44 (95% CI 1.27-4.70)] and in those with previously identified gastritis. In addition, there was an increased risk for peptic ulcer disease [OR 1.69 (95% CI 1.12-2.55)]. Individuals harboring the H. pylori strains VacA s1 (vs. s2), m1 (vs. m2), s1m1 (vs. s1m2), and s1m1 (vs. s2m2) had an increased risk for development of cancer [OR of 5.32 (95% CI 2.76-10.26), 2.50 (95% CI 1.67-3.750), 2.58 (95% CI 1.24-5.38), and 4.36 (95% CI 2.08-9.10), respectively]. s1m1 strains (vs. s2m2) were also associated with peptic ulcer disease [OR 2.04 (1.01-4.13)].

CONCLUSION

Our results indicate that individuals infected with CagA+ H. pylori strains and those infected with VacA s1 and m1 strains have an increased risk for gastric cancer. Cohort studies are welcome to integrate this information in the management of at-risk individuals such as those with precancerous cancer conditions and/or a family history of gastric cancer.

Meta-analysis: eradication of Helicobacter pylori infection is associated with the development of endoscopic gastroesophageal reflux disease

OBJECTIVE

The role of Helicobacter pylori infection in the pathogenesis of gastroesophageal reflux disease (GORD) is controversial. We aimed to confirm the negative association between H. pylori infection and endoscopic GORD and further determine whether eradication of the infection is associated with the development of endoscopic GORD.

MATERIALS AND METHODS

Case-control studies comparing the prevalence of H. pylori infection between patients with and those without GORD, type A cohort studies comparing the incidence of GORD between patients with and those without anti-H. pylori eradication therapy, and type B cohort studies comparing the incidence of GORD between H. pylori-positive patients with and those without successful eradication were included. Moreover, the effects of H. pylori eradication on the development of GORD in randomized-controlled trials were also analyzed.

RESULTS

Overall, 43 studies were analyzed. Case-control studies showed a lower prevalence of H. pylori infection in patients with GORD [odds ratio 0.64, 95% confidence interval (CI) 0.49-0.83]. Type A cohort studies showed an increased incidence of GORD in patients whose H. pylori infection was successfully eradicated [risk ratio (RR) 2.50, 95% CI 1.46-4.26]. Type B cohort studies showed that patients whose H. pylori had been eradicated had a higher risk of GORD (RR 1.70, 95% CI 1.30-2.23). Moreover, randomized-controlled trials showed that H. pylori eradication leads to a higher risk of GORD (RR 1.99, 95% CI 1.23-3.22); subanalyses showed that the risk existed especially in Asian studies (RR 4.53, 95% CI 1.66-12.36).

CONCLUSION

H. pylori infection shows a negative association with the development of endoscopic GORD. Eradication of the infection may be a risk factor for de-novo endoscopic GORD, especially in Asian populations.

The significance of virulence factors in Helicobacter pylori

Helicobacter pylori (H. pylori) infection is linked to various gastroduodenal diseases; however, only a small fraction of these patients develop associated diseases. Despite the high prevalence of H. pylori infection in Africa and South Asia, the incidence of gastric cancer in these areas is much lower than those in other countries. The incidence of gastric cancer tends to decrease from north to south in East Asia. Such geographical differences in the pathology can be explained, at least in part, by the presence of different types of H. pylori virulence factors in addition to host and environmental factors. Virulence factors of H. pylori, such as CagA, VacA, DupA, IceA, OipA and BabA, have been demonstrated to be the predictors of severe clinical outcomes. Interestingly, a meta-analysis showed that CagA seropositivity was associated with gastric cancer compared with gastritis, even in East Asian countries where almost the strains possess cagA. Another meta-analysis also confirmed the significance of vacA, dupA and iceA. However, it is possible that additional important pathogenic genes may exist because H. pylori consists of approximately 1600 genes. Despite the advances in our understanding of the development of H. pylori infection-related diseases, further work is required to clarify the roles of H. pylori virulence factors.

Development of an ELISA for Quantitative Detection of Immunoglobulin G (IgG) and IgA Antibodies to Helicobacter pylori for Use in Korean Patients with H. pylori-Associated Diseases

BACKGROUND/AIMS

We aimed to develop a quantitative enzyme-linked immunosorbent assay (ELISA) using whole-cell lysates of Helicobacter pylori 51 and to investigate its validity.

METHODS

Data from 300 plates were obtained by two different operators. Standard sera were used to make a standard curve to analyze the quantity of anti-H. pylori immunoglobulin G (IgG) and IgA antibody. We obtained reproducible data with fewer dilutions of samples by the addition of serially diluted standard serum to each ELISA plate. To evaluate the validity of this ELISA, the 114 H. pylori-positive and -negative subjects were stratified into four age groups, i.e., 0 to 4, 5 to 9, 10 to 15, and 20 to 29 years, before testing.

RESULTS

The mean IgG-antibody titers in H. pylori-positive and -negative subjects were 1,766.4 IU/mL and 654.3 IU/mL (p<0.001). The mean IgA-antibody titers in H. pylori-positive and -negative subjects were 350.1 IU/mL and 193.5 IU/mL (p<0.001). Anti-H. pylori IgG and IgA titers in the four age groups were higher in H. pylori-positive subjects than in H. pylori-negative subjects (p<0.05).

CONCLUSIONS

Using the current ELISA based on whole-cell lysates of H. pylori 51, reliable anti-H. pylori antibody titers were obtained regardless of the subject's age.

Helicobacter pylori infection in Japan

The prevalence of Helicobacter pylori infection is gradually decreasing in Japan. On the main island of Japan, nearly all H. pylori isolates possess cagA and vacA with strong virulence. However, less virulent H. pylori strains are frequently found in Okinawa where cases of gastric cancer are the lowest in Japan. Eradication therapy for peptic ulcer, idiopathic thrombocytopenic purpura, gastric mucosa-associated lymphoid tissue lymphoma and early gastric cancer after endoscopic resection has been approved by the Japanese national health insurance system. However, the Japanese Society for Helicobacter Research recently stated that all 'H. pylori infection' was considered as the indication for eradication irrespective of the background diseases. To eliminate H. pylori in Japan, the Japanese health insurance system should approve the eradication of all H. pylori infections.

The Helicobacter pylori cag Pathogenicity Island

The cag pathogenicity island is a well-characterized virulence determinant. It is composed of 32 genes that encode a type IV bacterial secretion system and is linked with a more severe clinical outcome. The following chapters will explore the manipulation of bacterial factors in order to understand their role in gastric mucosal disease.

"Targeted disruption of the epithelial-barrier by Helicobacter pylori"

Helicobacter pylori colonizes the human gastric epithelium and induces chronic gastritis, which can lead to gastric cancer. Through cell-cell contacts the gastric epithelium forms a barrier to protect underlying tissue from pathogenic bacteria; however, H. pylori have evolved numerous strategies to perturb the integrity of the gastric barrier. In this review, we summarize recent research into the mechanisms through which H. pylori disrupts intercellular junctions and disrupts the gastric epithelial barrier.

Relationship between cagA-positive Helicobacter pylori infection and risk of gastric cancer: a case control study in Porto Alegre, RS, Brazil

CONTEXT

Gastric cancer is the second most common cause of cancer related death worldwide. Although Helicobacter pylori has been classified as a class I carcinogen, the presence of infection is not a factor that alone is able to lead to gastric cancer, and one of the possible explanations for this is the existence of different strains of H. pylori with different degrees of virulence.

OBJECTIVES

To investigate the association between cagA-positive H. pylori and gastric cancer, using polymerase chain reaction (PCR) for the detection of this bacterial strain.

METHODS

Twenty-nine patients with gastric cancer were matched by sex and age (± 5 years) with 58 patients without gastric cancer, submitted to upper gastrointestinal endoscopy. All patients were evaluated for the status of infection by H. pylori (through urease test, histological analysis and PCR for the genes ureA and 16SrRNA) and by cagA-positive strain (through PCR for cagA gene).

RESULTS

Evaluating the presence of infection by cagA-positive H. pylori, it was verified that the rate of infection was significantly higher in the group with gastric cancer when compared with the matched controls, occurring in 62.1% and 29.3%, respectively (OR = 3.95; CI 95% 1.543-10.096).

CONCLUSIONS

There is an association between cagA-positive H. pylori strain and risk of gastric cancer.

Prevention of Gastric Cancer: When is Treatment of Helicobacter Pylori Warranted?

Chronic gastritis induced by Helicobacter pylori (H. pylori) is the strongest known risk factor for adenocarcinoma of the distal stomach, yet the effects of bacterial eradication on carcinogenesis remain unclear. H. pylori isolates possess substantial genotypic diversity, which engenders differential host inflammatory responses that influence clinical outcome. H. pylori strains that possess the cag pathogenicity island and secrete a functional cytotoxin induce more severe gastric injury and further augment the risk for developing distal gastric cancer. Carcinogenesis is also influenced by host genetic diversity, particularly involving immune response genes such as interleukin-1ß and tumor necrosis factor-α. Human trials and anima studies have indicated that eradication of H. pylori prior to the development of atrophic gastritis offers the best chance for prevention of gastric cancer. However, although the timing of intervention influences the magnitude of suppression of premalignant and neoplastic lesions, bacterial eradication, even in longstanding infections, is of clear benefit to the host. It is important to gain insight into the pathogenesis of H. pylori-induced gastritis and adenocarcinoma not only to develop more effective treatments for gastric cancer, but also because it might serve as a paradigm for the role of chronic inflammation in the genesis of other malignancies that arise within the gastrointestinal tract.

The human microbiome and surgical disease

OBJECTIVE

The purpose of this review article is to summarize what is currently known about microbes associated with the human body and to provide examples of how this knowledge impacts the care of surgical patients.

BACKGROUND

Pioneering research over the past decade has demonstrated that human beings live in close, constant contact with dynamic communities of microbial organisms. This new reality has wide-ranging implications for the care of surgical patients.

METHODS AND RESULTS

Recent advances in the culture-independent study of the human microbiome are reviewed. To illustrate the translational relevance of these studies to surgical disease, we discuss in detail what is known about the role of microbes in the pathogenesis of obesity, gastrointestinal malignancies, Crohn disease, and perioperative complications including surgical site infections and sepsis. The topics of mechanical bowel preparation and perioperative antibiotics are also discussed.

CONCLUSIONS

Heightened understanding of the microbiome in coming years will likely offer opportunities to refine the prevention and treatment of a wide variety of surgical conditions.

Serum Helicobacter pylori CagA antibody as a biomarker for gastric cancer in east-Asian countries

AIMS

In east-Asian countries, while almost all Helicobacter pylori strains possess the cytotokine-associated gene A (CagA) gene, serum CagA antibody is not detected in some infected subjects. We aimed to clarify the association between anti-CagA antibody and gastric cancer in east-Asian countries.

MATERIALS AND METHODS

We performed a meta-analysis of case-control studies with age- and sex-matched controls, which provided raw data in east-Asian countries.

RESULTS

Ten studies with a total of 4325 patients were identified in the search. Some reports from Japan, Korea and China showed a positive association between the presence of anti-CagA antibody and gastric cancer; however, the results differed in their various backgrounds. The disparate findings appeared to result from the use of different methods or from variations in the antigens used to detect the anti-CagA antibody. CagA seropositivity was associated with an increased risk of developing gastric cancer.

CONCLUSION

Anti-CagA antibody can be used as a biomarker for gastric cancer even in east-Asian countries.

Helicobacter pylori and gastric cancer: factors that modulate disease risk

Helicobacter pylori is a gastric pathogen that colonizes approximately 50% of the world's population. Infection with H. pylori causes chronic inflammation and significantly increases the risk of developing duodenal and gastric ulcer disease and gastric cancer. Infection with H. pylori is the strongest known risk factor for gastric cancer, which is the second leading cause of cancer-related deaths worldwide. Once H. pylori colonizes the gastric environment, it persists for the lifetime of the host, suggesting that the host immune response is ineffective in clearing this bacterium. In this review, we discuss the host immune response and examine other host factors that increase the pathogenic potential of this bacterium, including host polymorphisms, alterations to the apical-junctional complex, and the effects of environmental factors. In addition to host effects and responses, H. pylori strains are genetically diverse. We discuss the main virulence determinants in H. pylori strains and the correlation between these and the diverse clinical outcomes following H. pylori infection. Since H. pylori inhibits the gastric epithelium of half of the world, it is crucial that we continue to gain understanding of host and microbial factors that increase the risk of developing more severe clinical outcomes.

Role of innate immunity in Helicobacter pylori-induced gastric malignancy

Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.

Helicobacter pylori CagA causes mitotic impairment and induces chromosomal instability

Infection with cagA-positive Helicobacter pylori is the strongest risk factor for the development of gastric carcinoma. The cagA gene product CagA, which is delivered into gastric epithelial cells, specifically binds to and aberrantly activates SHP-2 oncoprotein. CagA also interacts with and inhibits partitioning-defective 1 (PAR1)/MARK kinase, which phosphorylates microtubule-associated proteins to destabilize microtubules and thereby causes epithelial polarity defects. In light of the notion that microtubules are not only required for polarity regulation but also essential for the formation of mitotic spindles, we hypothesized that CagA-mediated PAR1 inhibition also influences mitosis. Here, we investigated the effect of CagA on the progression of mitosis. In the presence of CagA, cells displayed a delay in the transition from prophase to metaphase. Furthermore, a fraction of the CagA-expressing cells showed spindle misorientation at the onset of anaphase, followed by chromosomal segregation with abnormal division axis. The effect of CagA on mitosis was abolished by elevated PAR1 expression. Conversely, inhibition of PAR1 kinase elicited mitotic delay similar to that induced by CagA. Thus, CagA-mediated inhibition of PAR1, which perturbs microtubule stability and thereby causes microtubule-based spindle dysfunction, is involved in the prophase/metaphase delay and subsequent spindle misorientation. Consequently, chronic exposure of cells to CagA induces chromosomal instability. Our findings reveal a bifunctional role of CagA as an oncoprotein: CagA elicits uncontrolled cell proliferation by aberrantly activating SHP-2 and at the same time induces chromosomal instability by perturbing the microtubule-based mitotic spindle. The dual function of CagA may cooperatively contribute to the progression of multistep gastric carcinogenesis.

Genetic factors involved in the development of Helicobacter pylori-related gastric cancer

Developmental process to gastric cancer by Helicobacter pylori infection consists of three steps: (1) H. pylori infection; (2) gastric atrophy development; and (3) carcinogenesis. In each step, genetic traits may influence the process, interacting with lifestyle. In the step of H. pylori infection, two lines of genetic polymorphisms were assumed: one influencing gastric acid inhibition interacting with smoking, and the other concerning innate immune response attenuation. The former includes functional polymorphisms of IL-1B (C-31T or tightly linked T-511C), and TNF-A (T-1031C and C-857T), and the latter possibly includes NQO1 C609T. In the step to gastric atrophy, polymorphisms pertaining to the signal transduction from cytotoxin-associated gene A (PTPN11 A/G at intron 3) and to T-cell responses (IL-2 T-330G and IL-13 C-1111T) were hypothesized. There are a limited number of epidemiological genotype studies on the final step of literal carcinogenesis, potentially interacting with smoking, a low vegetable and fruit intake, and salty foods, the well-documented risk factors. In past case-control studies on the associations between genotype and gastric cancer risk, the cases consisted of H. pylori-related and unrelated gastric cancer patients and the controls consisted of individuals including the uninfected (H. pylori unexposed and exposed) and the infected with and without gastric atrophy. Accordingly, it was not clear whether the observed risk was for H. pylori-related or -unrelated gastric cancer, nor which step was involved in the observed associations even when nearly all cases were H. pylori-related. In order to elucidate the genetic traits of H. pylori-related gastric cancer, stepwise evaluation will be required.

Local and systemic immune and inflammatory responses to Helicobacter pylori strains

Colonization with Helicobacter pylori eventuates in varied clinical outcomes, which relate to both bacterial and host factors. Here we examine the relationships between cagA status, serum and gastric juice antibody responses, and gastric inflammation in dyspeptic patients. Serum, gastric juice, and gastric biopsy specimens were obtained from 89 patients undergoing endoscopy. H. pylori colonization and cagA status were determined by histology, culture, and PCR methods, and acute inflammation and chronic inflammation in the gastric mucosa were scored by a single pathologist. Serum and gastric juice antibodies to H. pylori whole-cell and CagA antigens were determined by enzyme-linked immunosorbent assay. Relationships between variables were sequentially analyzed using univariate and multivariate statistical methods. Of the 89 subjects, 62 were colonized by H. pylori. By univariate analyses, levels of serum immunoglobulin G (IgG) and IgA and gastric juice IgA antibodies against whole-cell and CagA antigens each were significantly higher in the H. pylori-positive group than in the H. pylori-negative group (P<0.001). H. pylori and CagA sero-positivities were both significantly associated with enhanced inflammation in gastric antrum and body (P<0.02). The presence of gastric juice antibodies to H. pylori antigens was associated with more severe gastric inflammation. However, in multivariate analyses, only the presence of serum antibodies against CagA and, to a lesser extent, whole-cell antigens remained significantly associated with acute and chronic inflammation in antrum and body (P<0.05). Thus, serum antibody response to CagA correlates with severity of gastric inflammation. Furthermore, given the relationships demonstrated by multivariate analysis, determination of gastric juice antibodies may provide a better representation of serum, rather than secretory, immune response.

Causal role of Helicobacter pylori infection in gastric cancer

Gastric cancer is the second most frequent cancer in the world, accounting for a large proportion of all cancer cases in Asia, Latin America, and some countries in Europe. Helicobacter pylori (H pylori) is regarded as playing a specific role in the development of atrophic gastritis, which represents the most recognized pathway in multistep intestinal-type gastric carcinogenesis. Recent studies suggest that a combination of host genetic factors, bacterial virulence factors, and environmental and lifestyle factors determine the severity of gastric damage and the eventual clinical outcome of H pylori infection. The seminal discovery of H pylori as the leading cause of gastric cancer should lead to effective eradication strategies. Prevention of gastric cancer requires better screening strategies to identify candidates for eradication.

Helicobacter pylori CagA: a new paradigm for bacterial carcinogenesis

Infection with CagA-positive Helicobacter pylori is associated with the development of gastric adenocarcinoma. The CagA gene product CagA is injected directly from the bacterium into the bacterium-attached gastric epithelial cells via the type-IV secretion system. Upon membrane localization and subsequent tyrosine phosphorylation by Src family kinases, CagA functions as a scaffolding adaptor and interacts with a number of host proteins that regulate cell growth, cell motility and cell polarity in both CagA phosphorylation-dependent and phosphorylation-independent manners. Of special interest is the interaction of CagA with the SHP-2 tyrosine phosphatase, gain-of-function mutations that of which have recently been found in a variety of human malignancies. The CagA-SHP-2 interaction is entirely dependent on CagA tyrosine phosphorylation and, through the complex formation, SHP-2 is catalytically activated and induces morphological transformation with elevated cell motility. Intriguingly, structural diversity of the tyrosine phosphorylation sites of CagA accounts for the differential activity of individual CagA to bind and activate SHP-2. Deregulation of SHP-2 and other intracellular signaling molecules by H. pylori CagA may predispose cells to accumulate multiple genetic and epigenetic changes involved in gastric carcinogenesis. Furthermore, the differential potential of individual CagA to disturb cellular functions indicates that H. pylori strains carrying biologically more active CagA are more virulent than those with less active CagA and are more closely associated with gastric carcinoma.

Helicobacter pylori and Schistosoma japonicum co-infection in a Chinese population: helminth infection alters humoral responses to H. pylori and serum pepsinogen I/II ratio

The effects of helminth infection on humoral IgG responses and clinical outcome of gastric Helicobacter pylori infection are unknown. IgG and IgG subclass responses to H. pylori and serum pepsinogen I/II ratio, a marker of gastric atrophy, were investigated in a Schistosoma japonicum prevalent Chinese population. H. pylori, CagA and IgG subclass responses were assayed by ELISA. Serum pepsinogen I and pepsinogen II were assayed by ELISA and the pepsinogen I/II ratio determined. In 150 subjects, infection with S. japonicum and H. pylori was 55.3% and 51.3%, respectively. H. pylori IgG titres and CagA seropositivity were significantly lower (P<0.05) in co-infected subjects, and differences in H. pylori IgG isotype responses were evident. In H. pylori positives, a significantly higher (P<0.05) pepsinogen I/II ratio was observed in co-infected subjects. The difference between S. japonicum positive and negative subjects was only evident in H. pylori CagA seronegative subjects. In conclusion, S. japonicum co-infection with H. pylori is associated with alterations in IgG responses to H. pylori and less gastric atrophy.

Relation of CagA seropositivity to cagPAI phenotype and histological grade of gastritis in patients with Helicobacter pylori infection

AIM

Infection with Helicobacter pylori (H pylori) possessing the cag pathogenicity island (PAI) has been associated with severe clinical outcome and CagA-antibody has been used to indicate cagPAI-positive infection. The aim of this study was to examine the accuracy of CagA seropositivity to indicate the virulence of the cagPAI in Japan.

METHODS

Sixty isolates of H pylori cultured from gastric biopsies were examined by polymerase chain reaction assays for the presence of cagA, cagE and VirD4. Anti-CagA IgG antibody in matching sera was tested by both ELISA and immunoblot assay. Histological grade of gastritis was graded according to the updated Sydney System.

RESULTS

Amongst 53 patients infected with cagA+/cagE+/VirD4+ strain, 38 were CagA seropositive. There were four patients infected with strains possessing incomplete cagPAI. Two out of three patients with cagA+/cagE-/VirD4- infection were CagA seropositive, while a patient with cagA-/cagE+/VirD4+ infection was CagA seronegative. Accuracy of ELISA to predict bacterial possession of cagA was 61.7% whereas 58.3% for cagE and VirD4. The immunoblot assay showed relatively higher sensitivity and showed better accuracy. The lower grade of gastric mucosal inflammatory infiltration was seen in false CagA-seronegative patients.

CONCLUSION

Some serodiagnosis does not seem to have enough accuracy to indicate virulence of cagPAI, particularly in infection of strains with incomplete cagPAI. The degree of gastric mucosal inflammation may affect the results of CagA serodiagnosis.

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Helicobacter infection and gastric neoplasia

Chronic gastritis induced by Helicobacter pylori is the strongest known risk factor for adenocarcinoma of the distal stomach, yet only a minority of people who harbour this organism ever develop cancer. H. pylori isolates possess substantial genotypic diversity, which engenders differential host inflammatory responses that influence clinical outcome. H. pylori strains that possess the cag pathogenicity island and secrete a functional cytotoxin induce more severe gastric injury and further augment the risk for developing distal gastric cancer. However, carcinogenesis is also influenced by host genetic diversity, particularly involving immune response genes such as IL-1ss and TNF-alpha. It is important to gain insight into the pathogenesis of H. pylori-induced gastritis and adenocarcinoma, not only to develop more effective treatments for gastric cancer, but also because it might serve as a paradigm for the role of chronic inflammation in the genesis of other malignancies that arise within the gastrointestinal tract.

Gastric transcription profile of Helicobacter pylori infection in the rhesus macaque

Infection with Helicobacter pylori is usually asymptomatic but sometimes progresses to peptic ulcer disease or gastric adenocarcinoma. The development of disease involves both host and bacterial factors. In order to better understand host factors in pathogenesis, we studied the gastric transcription profile of H. pylori infection in the rhesus macaque by using DNA microarrays. Significant changes were found in the expression of genes important for innate immunity, chemokines and cytokines, cell growth and differentiation, apoptosis, structural proteins, and signal transduction and transcription factors. This broad transcription profile demonstrated expected up-regulation of cell structural elements and the host inflammatory and immune response, as well as the novel finding of down-regulation of heat shock proteins. These results provide a unique view of acute H. pylori infection in a relevant animal model system and will direct future studies regarding the host response to H. pylori infection.

Helicobacter pylori-CagA seropositivity and nitrite and ascorbic acid food intake as predictors for Gastric Cancer

A hospital-based case-control study was carried out between 1994 and 1996 to evaluate the risk of gastric cancer (GC) according to Helicobacter pylori-CagA (+) seropositivity, nitrite and ascorbic acid intake. Three geographical areas of Mexico were selected on the basis of their contrasting dietary patterns and H. pylori seroprevalence. Nitrite and ascorbic acid consumption were estimated by interview among 211 cases and 454 matched controls. Serum antibodies against IgG H. pylori and CagA were detected by immunosorbent assays. The adjusted risk for GC was significantly higher among CagA+ subjects compared with those that were CagA negative (Odds Ratio (OR)=2.04 95% Confidence Interval (CI) 1.37-3.02 P for trend P < 0.001), this effect remained significant among diffuse GC cases (OR 2.05 95% CI 1.25-3-36). No significant effects due to nitrite and ascorbic consumption or interactions of these nutrients with CagA seropositivity were detected. Seropositivity to H. pylori CagA+ strains may be an independent factor for diffuse GC in Mexico.

IgG subclass response to Helicobacter pylori and CagA antigens in children

Specific serum IgG subclass antibodies against Helicobacter pylori antigens and recombinant CagA were analysed in 75 symptomatic children with histologically confirmed H. pylori infection. H. pylori stimulated an IgG1 predominant response, and IgG3 titres showed a positive association with peptic ulcer disease, chronicity of antral inflammation and density of H. pylori colonization. Two methods used for assessing serum IgG CagA antibody status, i.e. Western blotting and enzyme-linked immunosorbent assay (ELISA), were concordant. CagA stimulated an IgG1 and IgG3 predominant humoral response. Total CagA IgG titres were higher in children with active and more severe chronic antral inflammation. These findings suggest that in children the systemic humoral immune response to H. pylori infection may reflect gastroduodenal pathology.

Meta-analysis of the relationship between cagA seropositivity and gastric cancer

BACKGROUND & AIMS

Reports in the literature regarding the relationship of infection with cagA -positive strains of Helicobacter pylori to gastric cancer over and above H. pylori infection alone are conflicting. The aim of this study was to estimate the magnitude of the risk for gastric cancer associated with cagA seropositivity and to identify any sources of heterogeneity between studies.

METHODS

A meta-analysis of case-control studies with age- and sex-matched controls, which provided raw data on the infection rates with H. pylori and cagA strains of H. pylori as detected by serology or polymerase chain reaction DNA, was performed.

RESULTS

A comprehensive literature search identified 16 qualified studies with 2284 cases and 2770 controls. H. pylori and cagA seropositivity significantly increased the risk for gastric cancer by 2.28- and 2.87-fold, respectively. Among H. pylori -infected populations, infection with cagA -positive strains further increased the risk for gastric cancer by 1.64-fold (95% confidence interval [CI], 1.21-2.24) overall and by 2.01-fold (95% CI, 1.21-3.32) for noncardiac gastric cancer. Gastric cancer at the cardia is not associated with H. pylori infection or cagA -positive strains of H. pylori. Patient age and site of gastric cancer contributed to the heterogeneity between studies.

CONCLUSIONS

Infection with cagA -positive strains of H. pylori increases the risk for gastric cancer over the risk associated with H. pylori infection alone. Searching for cagA status over H. pylori infection may confer additional benefit in identifying populations at greater risk for gastric cancer.

The evolving epidemiology of Helicobacter pylori infection and gastric cancer

The relationship between Helicobacter pylori infection and the risk of gastric cancer has been well established in the last decade. Four meta-analyses have found that the infection increases the risk of noncardia gastric cancer by 2- to 6-fold compared with noninfected control populations. However, the role of cagA strains of H pylori in relation to gastric cancer has not been evaluated systematically. We undertook a meta-analysis of epidemiological studies examining the relationship between infection with cagA-positive strains of H pylori and the risk of gastric cancer, and found that patients who are seropositive for cagA strains of H pylori are at an increased risk for developing noncardia gastric cancer compared with those with H pylori infection alone. Therefore, searching for cagA-positive strains of H pylori may help identify populations at a greater risk for developing gastric cancer.

Role of Helicobacter pylori CagA+ strains and risk of adenocarcinoma of the stomach and esophagus

Infection with Helicobacter pylori (H. pylori), especially CagA+ strains, has been associated with an increased risk of noncardia gastric adenocarcinoma. The relationship with junctional cancer (adenocarcinomas of the esophagus and gastric cardia combined) has not been adequately investigated, although some studies have reported a reduced risk associated with H. pylori and CagA seroseropositivity. We investigated this question in a subset of cases and controls from a recently completed, large population-based case-control study of gastric and esophageal adenocarcinomas in Los Angeles County. Using established antigen-specific ELISAs, serum IgG antibodies to H. pylori whole-cell antigens (Helico-G) and CagA were measured in population controls (n = 356) and patients with incident esophageal adenocarcinoma (n = 80), gastric cardia cancer (n = 87) or distal gastric cancers (noncardia gastric adenocarcinoma) (n = 127). After controlling for demographic characteristics (age, gender, race, birthplace, education), smoking and body mass index, seropositivity for H. pylori was associated with a statistically significant increased risk of distal gastric cancer (adjusted odds ratio [OR] = 1.85, 95% confidence interval [CI] = 1.03, 3.32) but the risk of junctional cancer was not increased (adjusted OR = 1.26, 95% CI = 0.82, 1.94). The risk of junctional cancer was not changed when CagA and H. pylori were both considered, but the risk of distal gastric cancer was further increased. Subjects who were seropositive for both CagA and H. pylori compared to those who were seronegative for H. pylori showed a risk of 2.20 (95% CI = 1.13, 4.26) for distal gastric cancer and 0.86 (95% CI = 0.47, 1.59) for junctional cancer. Although tests for interaction between smoking and H. pylori were not statistically significant for junctional or distal gastric cancers, risk for both tumor types tended to be higher among current smokers who were also H. pylori seropositive. In conclusion, we find no evidence that infection with CagA+ strains of H. pylori reduces risk of esophageal and gastric cardia adenocarcinoma in this population. Our findings confirm the positive association between risk of distal gastric cancer and infection with H. pylori infection, especially CagA+ strains.

Helicobacter pylori CagA--a potential bacterial oncoprotein that functionally mimics the mammalian Gab family of adaptor proteins

Helicobacter pylori virulence factor CagA is injected into gastric epithelial cells and undergoes tyrosine phosphorylation. Similar to mammalian Gab protein, tyrosine-phosphorylated CagA recruits and activates SHP-2 phosphatase at the plasma membrane, thereby inducing a growth factor-like effect. CagA-SHP-2 interaction may play an important role in bacterial pathogenesis, leading to gastric carcinoma.

Helicobacter pylori infection: CagA-specific antibodies are associated with clinical outcome, but not with HLA-class II polymorphisms of the host

In order to investigate the interrelation between immunogenetic host and bacterial factors the T-cell receptor (TCR) polymorphism TCRBV6S1 A/B, HLA-DRB1 alleles and cagA status was analyzed in 380 unrelated German individuals. H. pylori infection with cagA-positive bacterial strains was significantly associated with peptic ulcer disease in the German cohort. Patients homozygous for the non-functional TCRBV6S1B allele and presenting with peptic ulcer disease showed no CagA-specific antibodies in the majority of cases. There was no association between HLA-DRB1 alleles and the CagA status of infected individuals, although certain alleles show significant association to the infection status in different populations.

Ethnic difference in serology of Helicobacter pylori CagA between Japanese and non-Japanese Brazilians for non-cardia gastric cancer

The usefulness of serology against CagA of Helicobacter pylori as a biomarker to identify high-risk individuals for non-cardia gastric cancer (ncGC) remains unclear among several ethnic populations with a high prevalence of cagA-positive strains. We investigated ethnic differences of CagA serology in two sets of case-control subjects, Japanese-Brazilians (JB) and non-Japanese Brazilians (NJB). We performed a cross-sectional comparison of IgG antibody titers to CagA (CagA-Ab) and the combination of CagA-Ab with conventional surface antigen (Hp-Ab) in 80 JB and 178 NJB ncGC patients and their controls (160 JB and 178 NJB). The level of CagA-Ab titer in cancer cases was significantly higher in NJB than in JB. The strength of the association between CagA-Ab seropositivity (+) (> or = 10 U/ml) and ncGC was almost 2-fold higher in NJB than in JB [odds ratio (OR) (95% confidence interval), 4.5 (2.6-7.8) and 2.1 (1.2-3.6), respectively]. However, in both JB and NJB, the OR was highest in CagA-Ab(+) subjects with low titer (10-29 U/ml), and decreased inversely with elevating CagA-Ab titer. In addition, the serological status of CagA-Ab(+) and Hp-Ab(-) showed a similar close association with ncGC between JB and NJB [5.4 (1.9-15.3) and 5.4 (2.0-15.0), respectively]. These results suggest that although the roles of CagA in the carcinogenic process of ncGC might be different between JB and NJB, the CagA-Ab could be a useful marker for ncGC, independently of ethnicity, particularly in high-risk individuals with the serological status of CagA-Ab(+) with low IgG titer or combined with Hp-Ab(-).

Role of Helicobacter pylori infection among offspring or siblings of gastric cancer patients

A positive family history is an increased risk factor for gastric cancer within family members, and one of the possible causes of this is the intrafamilial clustering of Helicobacter pylori infection. Our study examined the prevalence of H. pylori infection, serum antibodies to CagA and VacA and atrophic gastritis and/or intestinal metaplasia in the offspring or siblings of gastric cancer patients. A total of 726 subjects included 300 relatives of 300 separate gastric cancer patients and 426 controls. All subjects underwent upper gastrointestinal endoscopic examination with a rapid urease test. Blood samples were obtained to test for the presence of serum antibodies to the CagA and VacA proteins of H. pylori. The prevalence of H. pylori infection was higher in relatives of cancer patients (75.3%) than in controls (60.1%), and the adjusted odds ratio was 2.1 (95% CI 1.5-2.9). When either siblings or 2 or more family members were gastric cancer patients, the prevalence of H. pylori infection was much higher compared to the prevalence in controls. There was no specific relationship between CagA and VacA, and H. pylori infection. Atrophic gastritis and/or intestinal metaplasia were more frequently found in H. pylori-infected relatives of cancer patients (26.1%) than in H. pylori-infected controls (12.9%). These results strongly support a role for H. pylori infection in familial aggregation of gastric cancer. The prophylactic eradication of H. pylori infection in the offspring or siblings of gastric cancer patients may be clinically beneficial.

Helicobacter pylori strain-specific modulation of gastric mucosal cellular turnover: implications for carcinogenesis

Helicobacter pylori colonization induces inflammation in essentially all hosts, a persistent process that increases the risk of developing distal gastric adenocarcinoma. However, only a small percentage of persons carrying H. pylori develop neoplasia; enhanced risk may be related to differences in expression of specific bacterial products, differences in the host response to the bacteria, or the interaction between host and microbe. H. pylori strains that have the cag pathogenicity island are associated with further increased risk for developing distal gastric cancer; however, host responses to H. pylori, such as altered epithelial cell proliferation and apoptosis, also may be important in lowering the threshold for carcinogenesis. H. pylori cag+ strains selectively enhance proliferation and attenuate apoptosis in human mucosa compared to cag- strains. However, cag+ strains also induce more severe gastritis, suggesting that host inflammatory mediators such as cytokines, prostaglandins, and hormones may modulate H. pylori-induced alterations in cellular turnover. In the Mongolian gerbil model of gastric carcinogenesis, apoptosis increases early and transiently following H. pylori infection, but scores progressively decline despite worsening gastric inflammation. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms. An emerging model invoked by these data is one in which H. pylori cag+ strains, in conjunction with host mediators, enhance gastric epithelial cell proliferation but not apoptosis in vivo. The combination of increased proliferation without a concordant increase in apoptosis may therefore contribute to the heightened retention of mutagenized cells, which over decades may increase the subsequent risk for gastric cancer.

Treatment with a proton pump inhibitor promotes corpus gastritis in patients with Helicobacter pylori-infected antrum-predominant gastritis

BACKGROUND

Proton pump inhibitors have been reported to modify the level of Helicobacter pylori gastritis.

AIM

To quantitatively investigate the effect of a proton pump inhibitor on the mucosal neutrophil reaction.

METHODS

Forty-six H. pylori-infected patients (17 duodenal ulcer, 29 gastric ulcer) were enrolled. During endoscopic examination, biopsy samples were obtained from the antrum and the corpus. The tissue content of neutrophil myeloperoxidase was measured by enzyme-linked immunoabsorbent assay, and H. pylori infection was histologically assessed. A proton pump inhibitor was administered orally for 8 weeks.

RESULTS

In the patients as a whole, antral myeloperoxidase decreased significantly after proton pump inhibitor treatment, but corpus myeloperoxidase remained largely unchanged. In duodenal ulcer patients, myeloperoxidase significantly decreased in the antrum, but increased in the corpus. In gastric ulcer patients, a significant reduction was observed in antral myeloperoxidase, but corpus myeloperoxidase remained unchanged. In the antral myeloperoxidase > corpus myeloperoxidase subgroup (n=24), antral myeloperoxidase significantly decreased, whereas corpus myeloperoxidase increased. No changes were observed at either site in the corpus myeloperoxidase > antral myeloperoxidase subgroup. Histology showed that the antral bacterial load of H. pylori decreased in all subgroups, but that it was mostly unchanged in the corpus.

CONCLUSIONS

Proton pump inhibitor treatment stimulated the neutrophil reaction in the corpus mucosa of duodenal ulcer patients and of patients in whom antral neutrophil accumulation was more predominant than that of the corpus. This phenomenon may not be caused by increased bacterial density.