Helicobacter pylori CagA status associated with gastric cancer incidence rate variability in Costa Rican regions

Regional variations in Helicobacter pylori infection, gastric atrophy and gastric cancer risk: The ENIGMA study in Chile

BACKGROUND

Regional variations in gastric cancer incidence are not explained by prevalence of Helicobacter pylori, the main cause of the disease, with several areas presenting high H. pylori prevalence but low gastric cancer incidence. The IARC worldwide H. pylori prevalence surveys (ENIGMA) aim at systematically describing age and sex-specific prevalence of H. pylori infection around the world and generating hypotheses to explain regional variations in gastric cancer risk.

METHODS

We selected age- and sex-stratified population samples in two areas with different gastric cancer incidence and mortality in Chile: Antofagasta (lower rate) and Valdivia (higher rate). Participants were 1-69 years old and provided interviews and blood for anti-H. pylori antibodies (IgG, VacA, CagA, others) and atrophy biomarkers (pepsinogens).

RESULTS

H. pylori seroprevalence (Age-standardized to world population) and antibodies against CagA and VacA were similar in both sites. H. pylori seroprevalence was 20% among children <10 years old, 40% among 10-19 year olds, 60% in the 20-29 year olds and close to or above 80% in those 30+ years. The comparison of the prevalence of known and potential H. pylori cofactors in gastric carcinogenesis between the high and the low risk area showed that consumption of chili products was significantly higher in Valdivia and daily non-green vegetable consumption was more common in Antofagasta. Pepsinogen levels suggestive of gastric atrophy were significantly more common and occurred at earlier ages in Valdivia, the higher risk area. In a multivariate model combining both study sites, age, chili consumption and CagA were the main risk factors for gastric atrophy.

CONCLUSIONS

The prevalence of H. pylori infection and its virulence factors was similar in the high and the low risk area, but atrophy was more common and occurred at younger ages in the higher risk area. Dietary factors could partly explain higher rates of atrophy and gastric cancer in Valdivia.

IMPACT

The ENIGMA study in Chile contributes to better understanding regional variations in gastric cancer incidence and provides essential information for public health interventions.

Nutrition and Helicobacter pylori: Host Diet and Nutritional Immunity Influence Bacterial Virulence and Disease Outcome

Helicobacter pylori colonizes the stomachs of greater than 50% of the world's human population making it arguably one of the most successful bacterial pathogens. Chronic H. pylori colonization results in gastritis in nearly all patients; however in a subset of people, persistent infection with H. pylori is associated with an increased risk for more severe disease outcomes including B-cell lymphoma of mucosal-associated lymphoid tissue (MALT lymphoma) and invasive adenocarcinoma. Research aimed at elucidating determinants that mediate disease progression has revealed genetic differences in both humans and H. pylori which increase the risk for developing gastric cancer. Furthermore, host diet and nutrition status have been shown to influence H. pylori-associated disease outcomes. In this review we will discuss how H. pylori is able to create a replicative niche within the hostile host environment by subverting and modifying the host-generated immune response as well as successfully competing for limited nutrients such as transition metals by deploying an arsenal of metal acquisition proteins and virulence factors. Lastly, we will discuss how micronutrient availability or alterations in the gastric microbiome may exacerbate negative disease outcomes associated with H. pylori colonization.

Pepsinogen-II 100 bp ins/del gene polymorphism and its elevated circulating levels are associated with gastric cancer, particularly with Helicobacter pylori infection and intestinal metaplasia

BACKGROUND

Polymorphism in the gene of pepsinogen-II (PG-II) and its serum level are effective biomarkers for terminal differentiation of gastric mucosa into gastritis, intestinal metaplasia (IM), and gastric cancer (GC) in relationship to Helicobacter pylori infection.

METHODS

Genotyping of the PG-II 100 bp insertion/deletion (ins/del) polymorphism was performed in patients with GC (n = 192) and age- and gender-matched H. pylori-associated dyspepsia (n = 180) and healthy subjects (HS, n = 240) by PCR. IgG anti-H. pylori (in all subjects) and serum PG-II levels were estimated in 145 patients each with GC and dyspepsia and in 65 healthy controls (HC) using ELISA (Biohit Oyj, Finland).

RESULTS

Five alleles were amplified by PCR: allele 5 (510 bp), allele 4 (480 bp), allele 3 (450 bp), allele 2 (400 bp), and allele 1 (shorter allele, 310 bp). Allele 1 carriage was infrequent, and serum PG-II level was higher among patients with GC than in HC [OR 0.43 (95 % CI, 0.29-0.85), p < 0.001 and mean ± SD; 17.53 ± 12.60 vs. 12.77 ± 7.53 µg/l, p = 0.005, respectively], particularly in the presence of H. pylori [OR 0.42 (0.25-0.71), p = 0.001 and 18.78 ± 12.63 vs. 13.97 ± 8.14, p = 0.034]. However, allele 1 carriage and PG-II levels were comparable among patients with GC and dyspepsia. Patients with IM also carried allele 1 infrequently and had higher levels of PG-II than those without [OR 0.5 (0.29-0.85), p = 0.011 and 20.07 ± 14.22 vs. 16.61 ± 12.08, p = 0.048].

CONCLUSIONS

Carriage of the shorter allele of the PG-II 100 bp ins/del polymorphism and elevated levels of PG-II are associated with GC, particularly with H. pylori infection and IM.

Phylogenetic analysis of Helicobacter pylori cagA gene of Turkish isolates and the association with gastric pathology

Background

The cagA gene is one of the important virulence factors of Helicobacter pylori. The diversity of cagA 5′ conserved region is thought to reflect the phylogenetic relationships between different H. pylori isolates and their association with peptic ulceration. Significant geographical differences among isolates have been reported. The aim of this study is to compare Turkish H. pylori isolates with isolates from different geographical locations and to correlate the association with peptic ulceration.

Methods

Total of 52 isolates of which 19 were Turkish and 33 from other geographic locations were studied. Gastric antral biopsies collected from 19 Turkish patients (Gastritis = 12, ulcer = 7) were used to amplify the cagA 5′ region by PCR then followed by DNA sequencing.

Results

The phylogenetic tree displayed 3 groups: A) a mix of 2 sub-groups “Asian” and “African/Anatolian/Asian/European”, B) “Anatolian/European” and C) “American-Indian”. Turkish H. pylori isolates clustered in the mixed sub-group A were mostly from gastritis patients while those clustered in group B were from peptic ulcer patients. A phylogenetic tree constructed for our Turkish isolates detected distinctive features among those from gastritis and ulcer patients. We have found that 2/3 of the gastritis isolates were clustered alone while 1/3 was clustered together with the ulcer isolates. Several amino acids were found to be shared between the later groups but not with the first group of gastritis.

Conclusions

This study provided an additional insight into the profile of our cagA gene which implies a relationship in geographic locations of the isolates.

Gastric cancer: an infectious disease

The role of infectious agents and chronic inflammation in carcinogenesis is being increasingly recognized. It has been estimated that about 18% of cancers are directly linked to infections, particularly gastric adenocarcinoma (Helicobacter pylori), cervical carcinoma (human papilloma viruses), and hepatocarcinoma (hepatitis B and C viruses). Multiple clinical trials of COX-2 inhibitors and other antiinflammatory agents have shown a beneficial effect on the development of diverse tumors, such as those of the colon, stomach, prostate, and breast. However, their mechanism of action is not completely understood and may differ among the infectious agents and tumor types. Because gastric adenocarcinomas account for more than 90% of all gastric malignancies, this review focuses on adenocarcinomas.

The enigma of Helicobacter pylori infection and gastric cancer

Although H. pylori has been recognized as a class I carcinogen, incongruence between infection prevalence and cancer incidence has been reported. Holcombe called attention to the high prevalence of infection in the face of low cancer rates, which he called "The African Enigma". Similar observations have now been made in other geographic areas. Gastric carcinoma should be considered an infectious disease, for which the classical epidemiologic model of causality applies. The model proposes that tissue injury inflicted by the infectious agent is modulated by its interactions with host and environmental factors. Although approximately half of the world's population is infected, only a small proportion of people develop cancer. The African enigma is a striking example of the major contrasts in cancer risk among populations with similarly high prevalence of infection. The mechanisms involved in reducing the risk of cancer in infected individuals are explored in this article, which may lead to the design of effective prevention strategies.

Role of bacterial and genetic factors in gastric cancer in Costa Rica

AIM: To evaluate several risk factors for gastric cancer (GC) in Costa Rican regions with contrasting GC incidence rate (GCIR).

METHODS: According to GCIR, 191 Helicobacter pylori (H pylori)-positive patients were classified into groups A (high GCIR, n = 101) and B (low GCIR, n = 90). Human DNA obtained from biopsy specimens was used in the determination of polymorphisms of the genes coding for interleukin (IL)-1&bgr; and IL-10 by PCR-RFLP, and IL-1RN by PCR. H pylori DNA extractions obtained from clinical isolates of 83 patients were used for PCR-based genotyping of H pylori cagA, vacA and babA2. Human DNA from gastric biopsies of 52 GC patients was utilized for comparative purposes.

RESULTS: Cytokine polymorphisms showed no association with GCIR variability. However, gastric atrophy, intestinal metaplasia and strains with different vacA genotypes in the same stomach (mixed strain infection) were more frequently found in group A than in group B, and cagA and vacA s1b were significantly associated with high GCIR (P = 0.026 and 0.041, respectively). IL-1&bgr;+3954_T/C (OR 2.1, 1.0-4.3), IL-1RN*2/L (OR 3.5, 1.7-7.3) and IL-10-592_C/A (OR 3.2, 1.5-6.8) were individually associated with GC, and a combination of these cytokine polymorphisms with H pylori vacA s1b and m1 further increased the risk (OR 7.2, 1.4-36.4).

CONCLUSION: Although a proinflammatory cytokine genetic profile showed an increased risk for developing GC, the characteristics of H pylori infection, in particular the status of cagA and vacA genotype distribution seemed to play a major role in GCIR variability in Costa Rica.

Frequency of Helicobacter pylori and CagA antibody in patients with gastric neoplasms and controls: the Indian enigma

BACKGROUND

Despite association between H. pylori and gastric neoplasm (GN) from the developed world, studies from India, where infection is more common and acquired early, are scant and contradictory.

METHODS

Two hundred and seventy-nine patients with GN from two northern and one eastern Indian centers during the period 1997-2005, 101 non-ulcer dyspepsia (NUD), and 355 healthy volunteers (HV) were evaluated for H. pylori [rapid urease test (RUT), histology and anti-H. pylori, and CagA IgG serology].

RESULTS

Patients with GN [263 gastric carcinoma and 16 (6%) primary gastric lymphoma, 208 male] were older than HV (n = 355, 188 male) and NUD (n = 101, 54 male) patients (53 +/- 12 versus 44 +/- 17 and 43 +/- 13 years, respectively; P < 0.001). Eastern Indian patients with GN (n = 145) were younger than those from northern India (n = 134; 52 +/- 12 versus 55 +/- 12 years; P < 0.007, t-test). In GN and NUD patients H. pylori positivity by RUT [86/225 (38%) versus 46/101 (46%)], anti-H. pylori IgG [154/198 (78%) versus 85/101 (84%)], and histology [136/213 (64%) versus 55/101 (55%)] were comparable (chi(2)-test). Serum IgG anti-H. pylori antibody was more common among HV than among GN patients [300/355 (85%) versus 154/198 (78%); P = 0.04, chi(2)-test]. Intestinal metaplasia was more common in GN than in NUD patients [101/252 (40%) versus 2/98 (2%), P < 0.000, chi(2)-test]. CagAIgG was more common in GN than in NUD patients [124/163 (76%) versus 64/101 (63%)] but comparable to that in HV patients [87/98 (89%), P = NS].

CONCLUSION

Frequency of H. pylori as detected using endoscopy and serology-based tests is not higher among patients with GN as compared with controls in India.

A new model for the transmission of Helicobacter pylori: role of environmental reservoirs as gene pools to increase strain diversity

Twenty-five years after the first successful cultivation and isolation of Helicobacter pylori, the scientific community is still struggling to understand the way(s) this bacterium is transmitted among the human population. Here, both epidemiologic and microbiologic evidence addressing this matter is reviewed and explored to conclude that most H. pylori successful colonizations are derived from direct person-to-person contact and that even though exposure of humans to H. pylori from environmental sources is a very common event, in most occasions the host is able to fight off infection. In addition, under a new model developed here, we propose that the near elimination of environmental reservoirs is the main responsible for the lower prevalence observed in the more industrialized countries by acting on two levels: by decreasing the number of direct infections and by diminishing the number of intraspecies recombination events for producing strain variation within H. pylori.

Relationship between Helicobacter pylori and DNA mismatch repair system

Helicobacter pylori infection causes the defect of mismatch repair (MMR) in eucaryotes, and microsatellite instability (MSI) in gastric epithelial cells, which increases the spontaneous mutation of relative genes, and finally results in the susceptibility to tumors in human bodies. DNA MMR can prevent the excessive proliferation of mutant cells and development of tumors by correcting mismatched bases, which occur in the process of duplication and recombination, and inducing apoptosis of the cells in which DNA had been seriously impaired. The majority of the mutation in mismatch repair gene is the gene mutation in which substitution exceeds the absence or insertion of the single basic group. In MMR, hMLH1 and hMSH2 gene are the main controlling genes. Current research showed that H pylori infection might lead to functional defect of MMR, which had played an important role in the development of gastric carcinomas. In this article, we reviewed the correlations between H pylori infection and DNA mismatch repair system.

The role of bacterial pathogens in cancer

The association of Helicobacter pylori with gastric cancer is the best-studied relationship between a bacterial infection and cancer. Other bacterial pathogens in humans and rodents are now being recognized as potentially having a direct role in carcinogenesis. Thus, it might be possible to understand the pathogenesis and prevention of certain cancers by studying the bacterial infections associated with them, and their effects on the host. However, the mechanisms by which bacteria contribute to cancer formation are complex, and recent investigations show that they involve the interplay between chronic inflammation, direct microbial effects on host cell physiology and, ultimately, changes in tissue stem cell homeostasis.