The biology of Helicobacter pylori infection, a major risk factor for gastric adenocarcinoma

Histopathological Features of Chronic Gastritis and its Association with Helicobacter pylori Infection

Background/Aims

A Helicobacter pylori (H. pylori) infection is the most common cause of chronic gastritis (CG), with approximately 50% of the world's population infected. Long-term infection increases the risk of progression to gastric cancer. This study evaluated the histopathological changes in CG using the Updated Sydney System (USS) to estimate the prevalence and correlation of H. pylori gastritis with other histological variables.

Methods

This research was a prospective observational study conducted in the Department of Pathology of a tertiary care teaching hospital in Central India. The study was conducted between Feb 2017 to April 2018. Two antral biopsies were taken per patient, one for a Rapid Urease Test and the second for routine histopathology. All samples were analyzed according to the USS.

Results

CG was found in 83.84% of total dyspeptic patients. The most common age group was 31-40 years, with a male preponderance. Of 109 gastric antral biopsies with histopathological evidence of chronic gastritis, neutrophilic activity, intestinal metaplasia, atrophy, and lymphoid aggregates were present in 50 (45.87%), 10 (9.2%), 23 (21.10%), and 11(10.09%) cases, respectively. The prevalence of H. pylori was 46.78%, and its association with the degree of chronic inflammation and intestinal metaplasia was statistically significant.

Conclusions

H. pylori was significantly associated with the degree of chronic inflammation and intestinal metaplasia. Hence, this study suggests a vigorous search for H. pylori should be initiated if chronic inflammation and intestinal metaplasia are seen in antral gastric biopsies.

The Spectrum of Helicobacter-Mediated Diseases

Helicobacter pylori is the leading cause of peptic ulcer disease. The infection has been implicated in more than 75% of duodenal ulcer cases and 17% of gastric ulcer cases. H. pylori has been classified as a human carcinogen, since it is the main cause of distal gastric adenocarcinoma and B cell mucosa-associated lymphoid tissue lymphoma. Evidence also links H. pylori with extragastric conditions including iron deficiency anemia, idiopathic thrombocytopenic purpura, and vitamin B₁₂ deficiency. Studies indicate that H. pylori may be protective against other conditions of the gastrointestinal tract (e.g., reflux esophagitis and related pathologies) and elsewhere in the body (e.g., asthma). The infection is asymptomatic in the vast majority of cases; more serious outcomes occur in only 10-15% of infected individuals. Despite extensive research over the past 3 decades, there is no effective vaccine, and the circumstances leading to disease development remain unclear. In addition, there is now a growing prevalence of antimicrobial resistance in H. pylori. This review discusses these important issues.

Chronic inflammation: key player and biomarker-set to predict and prevent cancer development and progression based on individualized patient profiles

A strong relationship exists between tumor and inflammation, which is the hot point in cancer research. Inflammation can promote the occurrence and development of cancer by promoting blood vessel growth, cancer cell proliferation, and tumor invasiveness, negatively regulating immune response, and changing the efficacy of certain anti-tumor drugs. It has been demonstrated that there are a large number of inflammatory factors and inflammatory cells in the tumor microenvironment, and tumor-promoting immunity and anti-tumor immunity exist simultaneously in the tumor microenvironment. The typical relationship between chronic inflammation and tumor has been presented by the relationships between Helicobacter pylori, chronic gastritis, and gastric cancer; between smoking, development of chronic pneumonia, and lung cancer; and between hepatitis virus (mainly hepatitis virus B and C), development of chronic hepatitis, and liver cancer. The prevention of chronic inflammation is a factor that can prevent cancer, so it effectively inhibits or blocks the occurrence, development, and progression of the chronic inflammation process playing important roles in the prevention of cancer. Monitoring of the causes and inflammatory factors in chronic inflammation processes is a useful way to predict cancer and assess the efficiency of cancer prevention. Chronic inflammation-based biomarkers are useful tools to predict and prevent cancer.

Common Core Bacterial Biomarkers of Bladder Cancer Based on Multiple Datasets

Recent studies have shown that microorganisms may be associated with the onset and development of bladder cancer. The purpose of this study is to identify the common core bacteria associated with bladder cancer. We characterized the urinary microbial profile of the individuals with bladder cancer by 16S rRNA gene sequencing, and the results of 24 bladder cancer samples collected in our laboratory reveal 31 common core bacteria at genera level. In addition, the abundance of four common core bacteria is significantly higher in bladder cancer samples than in samples from nondiseased people analyzed by LEfSe, based on two previous datasets. In particular, the abundance of Acinetobacter is much higher in bladder cancer samples. It has been reported that Acinetobacter is involved not only in biofilm formation but also in the adhesion and invasion of epithelial cells, the spread of bacteria caused by the degradation of phospholipids in the mucosal barrier, and the escape of the host immune response. Thus, Acinetobacter may be related to bladder cancer and is a potential microbial marker of bladder cancer. However, due to the limited number of participants, further studies are needed to better understand the role of microorganisms in bladder cancer to provide novel biomarkers for diagnosis, prognosis, and therapy.

Helicobacter pylori: History and facts in Peru

Helicobacter pylori (H. pylori) is a cosmopolite bacteria and the main responsible for the high burden of gastric cancer in developing countries, such as Peru. In this review, we describe some historical facts in the H. Pylori discovery, the first researches of this bacterium in Peru, as well as its epidemiology, clinical characteristics, diagnosis, treatments, and outcomes. Our literature and review of real-life data suggest that several efforts should be conducted in our country to deal with antibiotic-resistance and lack of adherence to treatment in order to reduce our incidence of gastric cancer.

Biofilm infections between Scylla and Charybdis: interplay of host antimicrobial peptides and antibiotics

Purpose

The aim of this study is to improve the anti-biofilm activity of antibiotics. We hypothesized that the antimicrobial peptide (AMP) complex of the host’s immune system can be used for this purpose and examined the assumption on model biofilms.

Methods

FLIP7, the AMP complex of the blowfly Calliphora vicina containing a combination of defensins, cecropins, diptericins and proline-rich peptides was isolated from the hemolymph of bacteria-challenged maggots. The complex interaction with antibiotics of various classes was studied in biofilm and planktonic cultures of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii by the checkerboard method using trimethyl tetrazolium chloride cell viability and crystal violet biofilm eradication assays supplemented with microscopic analysis.

Results

We found that FLIP7 demonstrated: high synergy (fractional inhibitory concentration index <0.25) with meropenem, amikacin, kanamycin, ampicillin, vancomycin and cefotaxime; synergy with clindamycin, erythromycin and chloramphenicol; additive interaction with oxacillin, tetracycline, ciprofloxacin and gentamicin; and no interaction with polymyxin B. The interaction in planktonic cell models was significantly weaker than in biofilms of the same strains. The analysis of the dose–effect curves pointed to persister cells as a likely target of FLIP7 synergistic effect. The biofilm eradication assay showed that the effect also caused total destruction of S. aureus and E. coli biofilm materials. The effect allowed reducing the effective anti-biofilm concentration of the antibiotic to a level well below the one clinically achievable (2–3 orders of magnitude in the case of meropenem, ampicillin, cefotaxime and oxacillin).

Conclusion

FLIP7 is a highly efficient host antimicrobial system helping antibiotics to overcome biofilm barriers through persisters’ sensitization and biofilm material destruction. It is promising for the treatment of biofilm infections as an adjuvant of various small-molecule antibiotics.

Natural antimicrobial peptide complexes in the fighting of antibiotic resistant biofilms: Calliphora vicina medicinal maggots

Biofilms, sedimented microbial communities embedded in a biopolymer matrix cause vast majority of human bacterial infections and many severe complications such as chronic inflammatory diseases and cancer. Biofilms’ resistance to the host immunity and antibiotics makes this kind of infection particularly intractable. Antimicrobial peptides (AMPs) are a ubiquitous facet of innate immunity in animals. However, AMPs activity was studied mainly on planktonic bacteria and little is known about their effects on biofilms. We studied structure and anti-biofilm activity of AMP complex produced by the maggots of blowfly Calliphora vicina living in environments extremely contaminated by biofilm-forming germs. The complex exhibits strong cell killing and matrix destroying activity against human pathogenic antibiotic resistant Escherichia coli, Staphylococcus aureus and Acinetobacter baumannii biofilms as well as non-toxicity to human immune cells. The complex was found to contain AMPs from defensin, cecropin, diptericin and proline-rich peptide families simultaneously expressed in response to bacterial infection and encoded by hundreds mRNA isoforms. All the families combine cell killing and matrix destruction mechanisms, but the ratio of these effects and antibacterial activity spectrum are specific to each family. These molecules dramatically extend the list of known anti-biofilm AMPs. However, pharmacological development of the complex as a whole can provide significant advantages compared with a conventional one-component approach. In particular, a similar level of activity against biofilm and planktonic bacteria (MBEC/MIC ratio) provides the complex advantage over conventional antibiotics. Available methods of the complex in situ and in vitro biosynthesis make this idea practicable.

Pattern-recognition receptors and gastric cancer

Chronic inflammation has been associated with an increased risk of several human malignancies, a classic example being gastric adenocarcinoma (GC). Development of GC is known to result from infection of the gastric mucosa by Helicobacter pylori, which initially induces acute inflammation and, in a subset of patients, progresses over time to chronic inflammation, gastric atrophy, intestinal metaplasia, dysplasia, and finally intestinal-type GC. Germ-line encoded receptors known as pattern-recognition receptors (PRRs) are critical for generating mature pro-inflammatory cytokines that are crucial for both Th1 and Th2 responses. Given that H. pylori is initially targeted by PRRs, it is conceivable that dysfunction within genes of this arm of the immune system could modulate the host response against H. pylori infection, and subsequently influence the emergence of GC. Current evidence suggests that Toll-like receptors (TLRs) (TLR2, TLR3, TLR4, TLR5, and TLR9), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) (NOD1, NOD2, and NLRP3), a C-type lectin receptor (DC-SIGN), and retinoic acid-inducible gene (RIG)-I-like receptors (RIG-I and MDA-5), are involved in both the recognition of H. pylori and gastric carcinogenesis. In addition, polymorphisms in genes involved in the TLR (TLR1, TLR2, TLR4, TLR5, TLR9, and CD14) and NLR (NOD1, NOD2, NLRP3, NLRP12, NLRX1, CASP1, ASC, and CARD8) signaling pathways have been shown to modulate the risk of H. pylori infection, gastric precancerous lesions, and/or GC. Further, the modulation of PRRs has been suggested to suppress H. pylori-induced inflammation and enhance GC cell apoptosis, highlighting their potential relevance in GC therapeutics. In this review, we present current advances in our understanding of the role of the TLR and NLR signaling pathways in the pathogenesis of GC, address the involvement of other recently identified PRRs in GC, and discuss the potential implications of PRRs in GC immunotherapy.

Diet, Helicobacter pylori strain-specific infection, and gastric cancer risk among Chinese men

Evidence for the association of diet and gastric cancer is equivocal, and the majority of previous studies have not evaluated the interaction of diet and infection with Helicobacter pylori, the leading risk factor for gastric cancer. We examined these associations among 226 cases and 451 controls nested within a prospective cohort. Dietary intakes were calculated from validated food frequency questionnaires. Blood levels of 15 antibodies to Helicobacter pylori proteins were assessed using multiplex serology. Odds ratios (ORs) were calculated using logistic regression. Among individuals infected with high-risk Helicobacter pylori (sero-positivity to 5-6 virulent H. pylori proteins), increasing intake of red meat, heme iron, and sodium increased risk (comparing highest tertile to lowest: ORs [95% confidence interval {CI}]: 1.85 [1.01-3.40]; 1.95 [1.06-3.57]; and 1.76 [0.91-3.43], respectively) while increasing intake of fruit decreased gastric cancer risk (comparing highest tertile of intake to lowest: OR [95% CI]: 0.52 [0.28-0.94]). No associations of diet with risk were found among individuals infected with low-risk H. pylori (P for interaction for red meat and sodium: 0.02 and 0.01, respectively). In this population with over 90% prevalence of CagA-positive H. pylori infection, categorizing individuals using H. pylori multiplex serology may identify individuals for whom a diet intervention may be effective.

The interplay between pathogen-associated and danger-associated molecular patterns: an inflammatory code in cancer?

There is increasing evidence of a close link between inflammation and cancer, and at the core of inflammation there are both pathogen-associated molecular patterns (PAMPs) and danger (or damage)-associated molecular patterns (DAMPs). Microorganisms harbor molecules structurally conserved within groups called PAMPs that are recognized by specific receptors present on immune cells, such as monocytes and dendritic cells (DCs); these are the pattern recognition receptors (PRRs). Activation through different PRRs leads to production of pro-inflammatory cytokines. A robust immune response also requires the presence of endogenous molecules that pose 'danger' to self-tissues and are produced by damaged or stressed cells; these are the DAMPs, which act also as inducers of inflammation. PAMPs and DAMPs are each recognized by a limited set of receptors that in number probably do not exceed 100. PAMPs and DAMPs interact with each other, and a single PRR can bind to a PAMP as well as a DAMP. Within this framework, we propose that PAMPs and DAMPs act in synchrony, modifying the activation threshold of one another. Thus, the range of PAMP-DAMP partnerships defines the course of inflammation, in a predictable manner, in an 'inflammatory code'. The definition of relevant PAMP-DAMP complexes is important for the understanding of inflammatory disorders in general, and of cancer in particular. Here, we review relevant findings that support the notion of a PAMP-DAMP-based inflammatory code, with emphasis on cancer immunology and immunotherapy.

Prospective study of Helicobacter pylori biomarkers for gastric cancer risk among Chinese men

BACKGROUND

Helicobacter pylori is the leading risk factor for gastric cancer, yet only a fraction of infected individuals ever develop neoplasia.

METHODS

To identify potential predictive biomarkers, we assessed the association of 15 antibodies to H. pylori proteins and gastric cancer in a nested case-control study. Blood levels of antibodies were assessed using multiplex serology for 226 incident cases and 451 matched controls from the Shanghai Men's Health Study. ORs and 95% confidence intervals (CI) were calculated using conditional logistic regression.

RESULTS

Seropositivity to four (Omp, HP0305, HyuA, and HpaA) proteins was associated with a 1.5- to 3-fold increased risk for gastric cancer. When excluding cases diagnosed within 2 years of study enrollment, seropositivity to two additional proteins (CagA and VacA) showed significant associations with risk. Compared with individuals with three or fewer seropositive results to the six virulent proteins identified in this population, individuals with four to five seropositive results were at a 2-fold increased risk (OR, 2.08; 95% CI, 1.31-3.30) and individuals seropositive to all six proteins had a 3.5-fold increase in risk (OR, 3.49; 95% CI, 2.00-6.11) for gastric cancer. Among individuals diagnosed at least 2 years after study enrollment, these associations were even stronger (ORs, 2.79 and 4.16, respectively).

CONCLUSIONS

Increasing number of seropositives to six H. pylori proteins may be a risk marker for distal gastric cancer in China.

IMPACT

In a population with a 90% prevalence of CagA-positive H. pylori infection, assessment of additional virulent H. pylori proteins might better identify individuals at high risk for gastric cancer.

Genetic variation in alcohol dehydrogenase (ADH1A, ADH1B, ADH1C, ADH7) and aldehyde dehydrogenase (ALDH2), alcohol consumption and gastric cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

Studies that have examined the association between alcohol consumption and gastric cancer (GC) risk have been inconsistent. We conducted an investigation of 29 genetic variants in alcohol metabolism loci (alcohol dehydrogenase, ADH1 gene cluster: ADH1A, ADH1B and ADH1C; ADH7 and aldehyde dehydrogenase, ALDH2), alcohol intake and GC risk. We analyzed data from a nested case-control study (364 cases and 1272 controls) within the European Prospective Investigation into Cancer and Nutrition cohort. Single nucleotide polymorphisms (SNPs) were genotyped using a customized array. We observed a statistically significant association between a common 3'-flanking SNP near ADH1A (rs1230025) and GC risk [allelic odds ratio (OR)(A v T) = 1.30, 95% confidence interval (CI) = 1.07-1.59]. Two intronic variants, one in ADH1C (rs283411) and one in ALDH2 (rs16941667), also were associated with GC risk (OR(T v C) = 0.59; 95% CI = 0.38-0.91 and OR(T v C) = 1.34; 95% CI = 1.00-1.79, respectively). Individuals carrying variant alleles at both ADH1 (rs1230025) and ALDH2 (rs16941667) were twice as likely to develop GC (OR(A+T) = 2.0; 95% CI = 1.25-3.20) as those not carrying variant alleles. The association between rs1230025 and GC was modified by alcohol intake (<5 g/day: OR(A) = 0.89, 95% CI = 0.57-1.39; ≥5 g/day: OR(A) = 1.45, 95% CI = 1.08-1.94, P-value = 0.05). The association was also modified by ethanol intake from beer. A known functional SNP in ADH1B (rs1229984) was associated with alcohol intake (P-value = 0.04) but not GC risk. Variants in ADH7 were not associated with alcohol intake or GC risk. In conclusion, genetic variants at ADH1 and ALDH2 loci may influence GC risk, and alcohol intake may further modify the effect of ADH1 rs1230025. Additional population-based studies are needed to confirm our results.

Relationship between full-length sequence characteristics of the vacA gene from high-cytotoxic and low-cytotoxic Helicobacter pylori in China and VacA activities

AIM: To evaluate the effect of vacA gene sequence variation on VacA activity by analyzing the full-length sequence of the vacA gene of high- and low-cytotoxic Helicobacter pylori (H. pylori) strains isolated from China.

METHODS: The full-length sequences of the vacA gene of four high- and four low-cytotoxic H. pylori strains were retrieved from GenBank database and analyzed using three bioinformatic programs (DNAMAN, Lasergene 7.0 and MEGA 5.0).

RESULTS: There existed significant sequence variations in the vacA gene among high- and low-cytotoxic H. pylori strains isolated from China and a high-cytotoxic H. pylori 60190 strain isolated from west country. These variations were mainly concentrated on the p55 domain of the vacA gene, resulting in transitions between hydrophobic and polar amino acids. Several insertion variations were detected in low-cytotoxic H. pylori strains compared to the H. pylori 60190 strain. High- and low-cytotoxic strains as well as strains isolated from China and west countrywere clustered as different H. pylori lineages.

CONCLUSION: Sequence and insert variation in the vacA gene might be an important reason resulting in VacA activity difference among H. pylori strains.

Association of circulating VacA-neutralizing antibodies with gastric cancer and duodenal ulcer

OBJECTIVE

To study the association between anti-VacA antibodies and pre-neoplastic lesions (IM), gastric cancer (GC), and duodenal ulcer (DU).

METHODS

A case-control study that included 347 patients, 90 with IM, 60 with GC, 52 with DU, and 145 with non-atrophic gastritis was conducted. For the analysis, a polytomous logistic regression models were used. Anti-VacA antibodies were identified in sera from these patients, either by Western blot assay (WB), using antigens produced by H. pylori s1m1 strain, or by neutralization assay challenging HeLa cells with H. pylori VacA s1m1 cytotoxin.

RESULTS

Results of the WB assay showed no association between WB-anti-VacA antibodies and gastroduodenal diseases. In contrast, when antibodies that neutralize VacA cytotoxic activity were studied, a significant association was found with IM (OR 2.7, 95% CI 1.4-5.1) and DU (OR 2.3, 95% CI 1.1-4.9) and an even stronger association with GC (OR 3.9, 95% CI 1.8-8.5). A significant association with histological subtypes of GC (diffuse and intestinal) and of IM (complete and incomplete) was also found. In addition, the association showed a significant dose-response effect in the case of GC, but not of DU or IM. These associations did not change substantially after adjustment for confounding factors.

MAIN CONCLUSION

This study showed that VacA-neutralizing antibodies are significantly associated with gastroduodenal diseases, especially GC, and that they might be used as risk markers of GC and DU.

Race, African ancestry, and Helicobacter pylori infection in a low-income United States population

BACKGROUND

Gastric cancer incidence in African Americans is twice that of whites, and differing prevalence of Helicobacter pylori strain-specific isolates may help explain the disparity.

METHODS

Serum levels of antibodies to each of 15 H. pylori proteins were assessed using multiplex serology for a sample of 689 African American and white participants from the Southern Community Cohort Study. African and European admixture was estimated using a panel of 276 ancestry genetic markers, with "low," "medium," and "high" categories of African ancestry defined as <85%, 85% to 95%, and ≥95%.

RESULTS

The majority (79%) of our study population were sero-positive for H. pylori. African American race was associated with a two- to sixfold increased odds for sero-positivity to eight H. pylori proteins, including the cancer-associated virulence constituents CagA [odds ratio (OR), 6.4; 95% CI, 4.5-9.1], and VacA (OR, 2.3; 95% CI, 1.5-3.5). Compared to whites, African Americans of low, medium, and high African ancestry had 1.6-, 4.1-, and 5.2-fold increased odds of sero-positivity to H. pylori, primarily related to CagA sero-positive strains, for which increasing African ancestry led to 2.5-, 9.6-, and 13.1-fold increased odds. Among African Americans alone, compared to those of low African ancestry, African Americans of medium and high African ancestry had 2.5- and 3.4-fold increased odds of sero-positivity to H. pylori, and 3.5- and 4.9-fold increased odds of CagA sero-positive H. pylori strains.

CONCLUSIONS

Host genetic variation and/or lifestyle factors associated with African ancestry contribute to the likelihood of infection with H. pylori, particularly its virulent strains, in this low-income U.S. southern population.

IMPACT

Our findings that low-income African Americans of high African ancestry have a particularly high prevalence of antibodies against H. pylori provides a framework for further research into better detection and prevention of gastric cancer in this population.

Helicobacter pylori induces activation of human peripheral γδ+ T lymphocytes

Helicobacter pylori is a gram-negative bacterium that causes gastric and duodenal diseases in humans. Despite a robust antibody and cellular immune response, H. pylori infection persists chronically. To understand if and how H. pylori could modulate T cell activation, in the present study we investigated in vitro the interaction between H. pylori and human T lymphocytes freshly isolated from peripheral blood of H. pylori-negative donors. A direct interaction of live, but not killed bacteria with purified CD3+ T lymphocytes was observed by microscopy and confirmed by flow cytometry. Live H. pylori activated CD3+ T lymphocytes and predominantly γδ+ T cells bearing the TCR chain Vδ2. Upon interaction with H. pylori, these cells up-regulated the activation molecule CD69 and produced cytokines (such as TNFα, IFNγ) and chemokines (such as MIP-1β, RANTES) in a non-antigen-specific manner. This activation required viable H. pylori and was not exhibited by other gram-negative bacteria. The cytotoxin-associated antigen-A (CagA), was at least partially responsible of this activation. Our results suggest that H. pylori can directly interact with T cells and modulate the response of γδ+ T cells, thereby favouring an inflammatory environment which can contribute to the chronic persistence of the bacteria and eventually to the gastric pathology.

Bacteria peptidoglycan promoted breast cancer cell invasiveness and adhesiveness by targeting toll-like receptor 2 in the cancer cells

Chronic bacterial infection increased the risk of many solid malignancies and the underlying mechanism is usually ascribed to bacterial-caused inflammation. However, the direct interaction of infectious bacteria with cancer cells has been largely overlooked. We identified that highly metastatic breast cancer MDA-MB-231 cells expressed high level of Toll-like receptor 2 (TLR2) in contrast to poorly metastatic breast cancer cells and homogenous untransformed breast cells. TLR2 in MDA-MB-231 cells were actively triggered by peptidoglycan (PGN) from infectious bacterium Staphylococcus aureus (PGN-SA), resulting in the promoted invasiveness and adhesiveness of the cancer cells in vitro. PGN-SA induced phosphorylation of TAK1 and IkappaB in the TLR2-NF-kappaB pathway of the cancer cells and stimulated IL-6 and TGF-beta secretion in MDA-MB-231 cells. All these effects were abrogated by TLR2 blockade. Further investigation showed that the NF-kappaB, STAT3 and Smad3 activities were augmented sequentially in MDA-MB-231 cells after PGN-SA stimulation. Phosphorylation of NF-kappaBp65 was initially increased and then followed by phosphorylation of STAT3 and Smad3 in the delayed 4 or 6 hours. NF-kappaB inhibition attenuated STAT3 and Smad3 activities whereas PGN-SA-stimulated cell culture supernatants reversed these inhibitory effects. Our study indicated that TLR2 activation by infectious bacterial PGN played an important role in breast cancer cell invasiveness and illustrated a new link between infectious bacteria and the cancer cells, suggesting the importance of antibiotic therapy to treat cancer with bacterial infection.

Gastric helicobacters in domestic animals and nonhuman primates and their significance for human health

Helicobacters other than Helicobacter pylori have been associated with gastritis, gastric ulcers, and gastric mucosa-associated lymphoid tissue lymphoma in humans. These very fastidious microorganisms with a typical large spiral-shaped morphology were provisionally designated "H. heilmannii," but in fact they comprise at least five different Helicobacter species, all of which are known to colonize the gastric mucosa of animals. H. suis, which has been isolated from the stomachs of pigs, is the most prevalent gastric non-H. pylori Helicobacter species in humans. Other gastric non-H. pylori helicobacters colonizing the human stomach are H. felis, H. salomonis, H. bizzozeronii, and the still-uncultivable "Candidatus Helicobacter heilmannii." These microorganisms are often detected in the stomachs of dogs and cats. "Candidatus Helicobacter bovis" is highly prevalent in the abomasums of cattle but has only occasionally been detected in the stomachs of humans. There are clear indications that gastric non-H. pylori Helicobacter infections in humans originate from animals, and it is likely that transmission to humans occurs through direct contact. Little is known about the virulence factors of these microorganisms. The recent successes with in vitro isolation of non-H. pylori helicobacters from domestic animals open new perspectives for studying these microorganisms and their interactions with the host.

Impact of pepsinogen C polymorphism on individual susceptibility to gastric cancer and its precancerous conditions in a Northeast Chinese population

PURPOSE

Human pepsinogen C (PGC) is an aspartic protease produced specifically by the gastric mucosa, and is considered as a mature marker of gastric epithelium. This study examined the contributions of PGC polymorphisms and the Helicobacter pylori (H. pylori) infection to the risk of gastric cancer (GC), and its precancerous conditions in a Northeast Chinese population.

METHODS

The PGC insertion/deletion polymorphism was evaluated by polymerase chain reaction analysis, followed by direct DNA sequencing in 564 cases of GC, atrophic gastritis (AG), gastric ulcer (GU) and superficial gastritis (as control). All cases were frequency-matched 1:1 by gender and age (+/-5). H. pylori infection was identified by serum anti-H. pylori IgG measurement through enzyme-linked immunosorbent assay.

RESULTS

Patients with a homozygous PGC allele 1 genotype had a significant risk of AG [adjusted odds ratio (OR) 3.11; 95% confidence interval (CI) 1.44-6.71] or of GC (OR 3.00; 95% CI 1.38-6.51), and a significantly elevated risk of intestinal metaplasia (OR 1.90, 95% CI 1.11-3.27). PGC polymorphism with H. pylori infection increased risk of GU (OR 8.69; 95% CI 1.01-74.69), and AG (OR 11.12; 95% CI 1.37-90.84) or GC (OR 10.61; 95% CI 1.28-87.79) in a super-multiplicative manner. The S value was 5.40, 6.48 and 4.34; and the AP value was 72.09, 7.00 and 69.69%, respectively.

CONCLUSIONS

The PGC gene polymorphism increases an individual's susceptibility to GC and its precancerous conditions. Moreover, the PGC gene polymorphism shows a positive link to H. pylori infection in the development of GC.

Association of Helicobacter pylori restriction endonuclease-replacing gene, hrgA with overt gastrointestinal diseases

BACKGROUND AND AIM

Helicobacter pylori has been proven to be responsible for causing various gastrointestinal disorders including gastric adenocarcinoma. Several genes of pathogen (the genes of the cag-PAI, vacA, iceA, and babA) either in combination or independently have been reported to significantly increase the risk of ulceration/gastric carcinoma, with the cagA gene having the strongest predictive value. Pursuit to identify new genes which could serve as a marker of overt disease progression, lead to the discovery of hrgA gene.

METHODS

Fifty-six indigenous strains of H. pylori from subjects with various gastric disorder were screened to assess the status of hrgA gene along with the cagA gene using simple polymerase chain reaction using specific oligonucleotide primers. Post-amplification, amplicons were subjected for sequencing to identify any strain specific variations in sequences from the H. pylori isolated from different disease manifestations. Histopathological analysis was done to ascertain any significant change in the histological scores of subjects infected with cagA+/hrgA+ and cagA-/hrg+ strains.

RESULTS

All the 56 (100%) subjects amplified with the oligonucleotide primers specific to hrgA gene, whereas 81.71% subjects showed the presence of cagA gene. Sequencing of the amplimers showed 99% homology. Histology of the cagA+/hrgA+ and cagA-/hrg+ subjects did not show any significant difference.

CONCLUSION

hrgA gene of Helicobacter pylori is not a ideal surrogate marker for identifying individuals with higher risk of developing overt gastro-duodenal diseases such as neoplasia of the stomach.

Association of Helicobacter pylori infection and diet on the risk of gastric cancer: a case-control study in Hawaii

OBJECTIVE

The risk factors most strongly associated with gastric cancer are the gastric bacteria Helicobacter pylori and diet. Utilizing data from a case-control study among residents in Hawaii, we examined the association of diet, presence of H. pylori, and non-cardia gastric cancer risk.

METHODS

Serum taken at diagnosis for cases (n = 212) and at interview for controls (n = 336) was assayed for IgG antibodies to H. pylori group antigens and to a recombinant fragment of the cytotoxin-associated antigen A (CagA) protein, and subjects completed food frequency questionnaires. Risk measures were calculated using logistic regression. The likelihood ratio test was used to assess interactions.

RESULTS

Inverse associations were found between gastric cancer risk and increasing intake of several micronutrients and vegetables among all individuals. For H. pylori/CagA-positive subjects, significant trends were present for total, green, and yellow vegetables, while a significant trend was present only for yellow vegetables among H. pylori/CagA-negative individuals. For intestinal gastric cancer, there was a suggestion that intake of vegetables, especially cruciferous vegetables, had a stronger protective effect for the H. pylori/CagA-positive group.

CONCLUSIONS

Diet may play a greater role in the etiology of non-cardia gastric cancer among individuals with evidence of H. pylori infection than among those without.

Meta-analysis of different test indicators: Helicobacter pylori infection and the risk of colorectal cancer

BACKGROUND AND AIMS

Recent studies have demonstrated the relationship between Helicobacter pylori infection and the risk of colorectal carcinoma. However, the results of these studies remain controversial as the studies were relatively small in size and partially differed in designs, and so we reviewed the published studies and carried out a meta-analysis to further explore this relationship.

MATERIALS AND METHODS

We performed an extensive systematic review to find all the published case-control studies up to Jan. 2007 using electronic searching, hand searching, and reference lists of retrieved articles. Odds ratio (OR) was employed to evaluate the relationship of H. pylori infection and risk of colorectal cancer. Summary estimates were obtained using random effect models according to the result of a statistical test for heterogeneity across the studies. The presence of possible publication bias was assessed using different statistical approaches.

RESULTS

Thirteen studies were included, and summary OR 1.49 (95% confidence interval [CI] 1.17-1.91) was estimated for the association between H. pylori infection and colorectal cancer. Summary OR 1.56 (95% CI 1.14-2.14) was estimated for the association between immunoglobulin G antibody and colorectal cancer risk. By trimming and filling, the number of inputted studies was zero, and summary OR was still 1.49 (95% CI 1.17-1.91). The graphical funnel plot appeared asymmetrical, but there was no statistical evidence of publication bias. The method of fail-safe suggested that the effect of publication bias was small.

CONCLUSION

Current evidence, though limited, suggests that there is a possible increase in risk of colorectal cancer because of H. pylori infection.

Identification and characterization of a novel p42.3 gene as tumor-specific and mitosis phase-dependent expression in gastric cancer

Multiple genetic alterations are attributed to gastric cancer (GC); however, only a few critical genes have been identified so far. In this study, we isolated and characterized a novel gene p42.3, represented as tumor-specific and mitosis phase-dependent expression protein in GC cell line BGC823. Our data showed that the expression of p42.3 was cell cycle-dependent in GC cell lines. Moreover, p42.3 was specifically expressed in primary GC tissues but not in the matched normal mucosa of stomach, and this gene was expressed in diverse embryonic tissues. Furthermore, significant suppression of cell proliferation and tumorigenicity were detected and G(2)/M phase arrest was observed in cell line BGC823 depleted of p42.3 expression by RNAi technique, and we confirmed the expression changes of cyclin B1 and Chk2 following the silence of p42.3. Taken together, we cloned and characterized p42.3 gene that was specifically expressed in GC tumors but not in normal gastric mucosa, and the gene was associated with M-phase regulation. Moreover, p42.3 might be involved in cell proliferation and tumorigenesis; therefore, this gene might have potential applications in the diagnosis or treatment of GC.

Identification of Helicobacter pylori genes that contribute to stomach colonization

Chronic infection of the human stomach by Helicobacter pylori leads to a variety of pathological sequelae, including peptic ulcer and gastric cancer, resulting in significant human morbidity and mortality. Several genes have been implicated in disease related to H. pylori infection, including the vacuolating cytotoxin and the cag pathogenicity island. Other factors important for the establishment and maintenance of infection include urease enzyme production, motility, iron uptake, and stress response. We utilized a C57BL/6 mouse infection model to query a collection of 2,400 transposon mutants in two different bacterial strain backgrounds for H. pylori genetic loci contributing to colonization of the stomach. Microarray-based tracking of transposon mutants allowed us to monitor the behavior of transposon insertions in 758 different gene loci. Of the loci measured, 223 (29%) had a predicted colonization defect. These included previously described H. pylori virulence genes, genes implicated in virulence in other pathogenic bacteria, and 81 hypothetical proteins. We have retested 10 previously uncharacterized candidate colonization gene loci by making independent null alleles and have confirmed their colonization phenotypes by using competition experiments and by determining the dose required for 50% infection. Of the genetic loci retested, 60% have strain-specific colonization defects, while 40% have phenotypes in both strain backgrounds for infection, highlighting the profound effect of H. pylori strain variation on the pathogenic potential of this organism.

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