Host-bacterial interaction in the development of gastric precancerous lesions in a high risk population for gastric cancer in Venezuela

Helicobacter pylori Diversity and Gastric Cancer Risk

Gastric cancer is a leading cause of cancer-related death worldwide. Helicobacter pylori infection is the strongest known risk factor for this malignancy. An important goal is to identify H. pylori-infected persons at high risk for gastric cancer, so that these individuals can be targeted for therapeutic intervention. H. pylori exhibits a high level of intraspecies genetic diversity, and over the past two decades, many studies have endeavored to identify strain-specific features of H. pylori that are linked to development of gastric cancer. One of the most prominent differences among H. pylori strains is the presence or absence of a 40-kb chromosomal region known as the cag pathogenicity island (PAI). Current evidence suggests that the risk of gastric cancer is very low among persons harboring H. pylori strains that lack the cag PAI. Among persons harboring strains that contain the cag PAI, the risk of gastric cancer is shaped by a complex interplay among multiple strain-specific bacterial factors as well as host factors. This review discusses the strain-specific properties of H. pylori that correlate with increased gastric cancer risk, focusing in particular on secreted proteins and surface-exposed proteins, and describes evidence from cell culture and animal models linking these factors to gastric cancer pathogenesis. Strain-specific features of H. pylori that may account for geographic variation in gastric cancer incidence are also discussed.

Effect of Helicobacter pylori on cyclooxygenase-2 and inducible nitric oxide synthase in patients with gastric precancerous lesions and its clinical significance

The aim of this study was to investigate the effect of Helicobacter pylori (Hp) on cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) levels in patients with gastric precancerous lesions and its clinical significance. A total of 114 patients with gastric precancerous lesions, 57 whom were positive for Hp (observation group) and 57 of whom were negative for Hp (control group), were selected for the study. The mRNA levels of COX-2 and iNOS in the gastric precancerous lesion tissue from the two groups of patients were analyzed through the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The protein expression levels of COX-2 and iNOS were analyzed using western blotting and an iNOS kit, respectively. In addition, normal human gastric mucosal GES-1 cells were cultured in vitro and stimulated by Hp for 3, 6, 9 and 12 h. The variations in the mRNA and protein levels of COX-2 and iNOS were then analyzed via RT-qPCR and western blotting. Compared with the control group, the mRNA levels of COX-2 and iNOS in the gastric tissue from the observation group were significantly increased (P<0.05). Furthermore, the expression level of COX-2 and iNOS protein in the gastric tissue from the observation group was significantly higher than that in the tissue from the control group (P<0.05). In vitro analysis showed that the COX-2 and iNOS mRNA and protein levels were significantly increased in the Hp-stimulated normal human gastric mucosal GES-1 cells compared with those in the unstimulated cells. Furthermore, the effect was time-dependent (P<0.05). In conclusion, COX-2 and iNOS are the main inflammatory markers. Hp can induce high expression levels of COX-2 and iNOS in gastric precancerous lesion tissue, which may be associated with the occurrence and development of gastric precancerous lesions.

To be or not to be: The host genetic factor and beyond in Helicobacter pylori mediated gastro-duodenal diseases

Helicobacter pylori (H. pylori) have long been associated with a spectrum of disease outcomes in the gastro-duodenal system. Heterogeneity in bacterial virulence factors or strains is not enough to explain the divergent disease phenotypes manifested by the infection. This review focuses on host genetic factors that are involved during infection and eventually are thought to influence the disease phenotype. We have summarized the different host genes that have been investigated for association studies in H. pylori mediated duodenal ulcer or gastric cancer. We discuss that as the bacteria co-evolved with the host; these host gene also show much variation across different ethnic population. We illustrate the allelic distribution of interleukin-1B, across different population which is one of the most popular candidate gene studied with respect to H. pylori infections. Further, we highlight that several polymorphisms in the pathway gene can by itself or collectively affect the acid secretion pathway axis (gastrin: somatostatin) thereby resulting in a spectrum of disease phenotype

Genotyping of Helicobacter pylori virulence-associated genes shows high diversity of strains infecting patients in western Venezuela

BACKGROUND

Helicobacter pylori is a major cause of chronic gastritis and an established risk factor for gastric adenocarcinoma. This bacterium also exhibits an extraordinarily high genetic diversity.

METHODS

The genetic diversity of H. pylori strains from Venezuelan patients with chronic gastritis was evaluated by PCR-typing of vacA, cagA, iceA, and babA2 virulence-associated genes using DNA extracted directly from biopsies. The nucleotide sequence and prevalence of size variants of iceA1, iceA2, and babA2 PCR products were introduced in this analysis.

RESULTS

The frequency of vacA s1 was associated (p<0.01) with moderate/severe grades of atrophic gastritis. The cagA, iceA1, iceA2, and babA2 genotypes were found in 70.6%, 66.4%, 33.6%, and 92.3% of strains, respectively. The frequency of iceA2 and its subtype iceA2_D were higher (p<0.015) in cases with moderate/severe granulocytic inflammation. The most prevalent combined genotypes were vacA s1m1/cagA/iceA1/babA2 (26.3%), vacA s2m2/iceA1/babA2 (19.5%), and vacA s1m1/cagA/iceA2/babA2 (18.8%). Sequence analysis of iceA1, iceA2, and babA2 PCR-amplified fragments allowed us to define allelic variants and to increase the number of genotypes detected (from 19 to 62). A phylogenetic tree made with iceA1 sequences showed that the H. pylori strains analyzed here were grouped with those of Western origin.

CONCLUSIONS

Our results show that patients from the western region of Venezuela have an elevated prevalence of infection with H. pylori strains carrying known virulence genotypes with high genetic diversity. This highlights the importance of identifying gene variants for an early detection of virulent genotypes.

Multifactorial etiology of gastric cancer

The prevalence of gastric cancer is associated with several factors including geographical location, diet, and genetic background of the host. However, it is evident that infection with Helicobacter pylori (H. pylori) is crucial for the development of the disease. Virulence of the bacteria is also important in modulating the risk of the disease. After infection, H. pylori gains access to the gastric mucosa and triggers the production of cytokines that promote recruitment of inflammatory cells, probably involved in tissue damage. Once the infection is established, a cascade of inflammatory steps associated with changes in the gastric epithelia that may lead to cancer is triggered. H. pylori-induced gastritis and H. pylori-associated gastric cancer have been the focus of extensive research aiming to discover the underlying mechanisms of gastric tissue damage. This research has led to the association of host genetic components with the risk of the disease. Among these is the presence of single nucleotide polymorphisms (SNPs) in several genes, including cytokine genes, which are able to differentially modulate the production of inflammatory cytokines and then modulate the risk of gastric cancer. Interestingly, the frequency of some of these SNPs is different among populations and may serve as a predictive factor for gastric cancer risk within that specific population. However, the role played by other genetic modifications should not be minimized. Methylation of gene promoters has been recognized as a major mechanism of gene expression regulation without changing the primary structure of the DNA. Most DNA methylation occurs in cytosine residues in CpG dinucleotide, but it can also be found in other DNA bases. DNA methyltransferases add methyl groups to the CpG dinucleotide, and when this methylation level is too high, the gene expression is turned off. In H. pylori infection as well as in gastric cancer, hypermethylation of promoters of genes involved in cell cycle control, metabolism of essential nutrients, and production of inflammatory mediators, among others, has been described. Interestingly, DNA changes like SNPs or mutations can create CpG sites in sequences where transcription factors normally sit, affecting transcription.In this chapter, we review the literature about the role of SNPs and methylation on H. pylori infection and gastric cancer, with big emphasis to the H. pylori role in the development of the disease due to the strong association between both.

Multifactorial etiology of gastric cancer

The prevalence of gastric cancer is associated with several factors including geographical location, diet, and genetic background of the host. However, it is evident that infection with Helicobacter pylori (H. pylori) is crucial for the development of the disease. Virulence of the bacteria is also important in modulating the risk of the disease. After infection, H. pylori gains access to the gastric mucosa and triggers the production of cytokines that promote recruitment of inflammatory cells, probably involved in tissue damage. Once the infection is established, a cascade of inflammatory steps associated with changes in the gastric epithelia that may lead to cancer is triggered. H. pylori-induced gastritis and H. pylori-associated gastric cancer have been the focus of extensive research aiming to discover the underlying mechanisms of gastric tissue damage. This research has led to the association of host genetic components with the risk of the disease. Among these is the presence of single nucleotide polymorphisms (SNPs) in several genes, including cytokine genes, which are able to differentially modulate the production of inflammatory cytokines and then modulate the risk of gastric cancer. Interestingly, the frequency of some of these SNPs is different among populations and may serve as a predictive factor for gastric cancer risk within that specific population. However, the role played by other genetic modifications should not be minimized. Methylation of gene promoters has been recognized as a major mechanism of gene expression regulation without changing the primary structure of the DNA. Most DNA methylation occurs in cytosine residues in CpG dinucleotide, but it can also be found in other DNA bases. DNA methyltransferases add methyl groups to the CpG dinucleotide, and when this methylation level is too high, the gene expression is turned off. In H. pylori infection as well as in gastric cancer, hypermethylation of promoters of genes involved in cell cycle control, metabolism of essential nutrients, and production of inflammatory mediators, among others, has been described. Interestingly, DNA changes like SNPs or mutations can create CpG sites in sequences where transcription factors normally sit, affecting transcription.In this chapter, we review the literature about the role of SNPs and methylation on H. pylori infection and gastric cancer, with big emphasis to the H. pylori role in the development of the disease due to the strong association between both.

Genetic predisposition to Helicobacter pylori-induced gastric precancerous conditions

Gastric cancer is the most common malignancy of the gastrointestinal tract in East Asian populations and the second most frequent cause of cancer-related mortality in the world. While previous studies have investigated the genetic factors involved in gastric carcinogenesis, there still exist relatively few studies that have investigated the genetic traits associated with the risk of gastric precancerous conditions. In this paper we will review the biology and genetic polymorphisms involved in the genesis of gastric precancerous conditions reported to date and discuss the future prospects of this field of study. The associations of gastric precancerous conditions with polymorphisms in the cytotoxin-associated gene A-related genes (e.g. PTPN11 G/A at intron 3, rs2301756), those in the genes involved in host immunity against Helicobacter pylori (H. pylori) infection (e.g. TLR4 +3725G/C, rs11536889) or polymorphisms of the genes essential for the development/ differentiation of the gastric epithelial cells (e.g. RUNX3 T/A polymorphism at intron 3, rs760805) have been reported to date. Genetic epidemiological studies of the associations between H. pylori-induced gastric precancerous conditions and other gene polymorphisms in these pathways as well as polymorphisms of the genes involved in other pathways like oxidative DNA damage repair pathways would provide useful evidence for the individualized prevention of these H. pylori-induced gastric precancerous conditions.

Combination of Helicobacter pylori-iceA2 and proinflammatory interleukin-1 polymorphisms is associated with the severity of histological changes in Venezuelan chronic gastritis patients

Helicobacter pylori is a major cause of chronic gastritis (CG) and a firmly established carcinogen for gastric adenocarcinoma. However, the underlying pathogenic mechanisms are not fully understood. In this work we studied the association of the allelic variation of H. pylori-iceA virulence factor and human proinflammatory interleukin (IL)-1 polymorphisms (IL-1B-31, IL-1B-511, IL-1B+3954 and IL-1RN) with histopathological changes in the gastric mucosa of patients with CG in Venezuela, a country with a high incidence of and mortality from gastric cancer. Although in this work the iceA1 allele was found more frequently (69.7%), iceA2 allele prevalence was higher in samples with atrophic gastritis (AG) and more severe grades of granulocytic (G2/G3) [P=0.02; odds ratio (OR) 3.3] and lymphocytic infiltration (L2/L3). The carriage of iceA2 strains combined with proinflammatory IL-1 polymorphisms IL-1-31C or IL-1-511T allele carrier genotypes increased even more the risk of presenting G2/G3 with ORs of 5.1 and 5.4, respectively. Moreover, the iceA2/IL-1B-511T and iceA2/IL-1B-31C/-511T/IL-1RN(*)2 bacteria/host genotype combinations showed a significant association with AG and L2/L3, respectively. Despite not being well established, the bacterial risk factor iceA2 seems an important predictor of severe histological changes in CG, separately or in combination with host genetic factors in the Venezuelan population.

Premalignant lesions in gastric cancer

Despite a plateau in incidence, gastric cancer is one of the most common cancers worldwide and causes considerable morbidity and mortality. Premalignant gastric lesions are well known risk factors for the development of intestinal-type gastric adenocarcinomas. In this multistep model of gastric carcinogenesis, Helicobacter pylori causes chronic active inflammation of the gastric mucosa, which slowly progresses through the premalignant stages of atrophic gastritis, intestinal metaplasia, and adenoma/dysplasia to gastric carcinoma. This progression is paralleled by a stepwise accumulation of multiple genetic and epigenetic abnormalities. Detection, treatment, and molecular analyses of premalignant lesions may thus provide a basis for gastric cancer prevention. This review describes an overview of current knowledge on premalignant gastric lesions. It also reviews the issue of surveillance of patients with premalignant lesions in order to improve the survival of patients with gastric cancer.

Host single nucleotide polymorphisms of MMP-9 -1562/TIMP-1 372 have gender differences in the risk of gastric intestinal metaplasia after Helicobacter pylori infection

BACKGROUND

Helicobacter pylori infection causes chronic gastric inflammation and intestinal metaplasia (IM), related with deregulation of Wnt pathway and over-expressions of COX-2, matrix metalloproteinase (MMP), and tissue inhibitors of matrix metalloproteinase (TIMP). We thus test the host genomic predispositions related to the risk of IM after H. pylori infection.

METHODS

We enrolled 296 H. pylori-infected patients to provide gastric biopsies for histology and genomic DNA for genotypes of single nucleotide polymorphisms (SNPs), including APC, COX-2, IL-1B, IL-1RN, IL-10, MMP-2, MMP-9, TIMP-1, and TIMP-2 determined by sequence specific oligonucleotide probe, sequence specific primers, restriction fragment length polymorphism, or real-time polymerase chain reaction.

RESULTS

There was no association between the presence of IM and SNPs in APC, COX-2, IL-1B, IL-1RN, IL-10, MMP-2, and TIMP-2. The risk of IM was increased up to 2.29-folds in males with TIMP-1 372 C, and 3.03-fold in females with T carrier (p < .05). The combination genotype of MMP-9 -1562/TIMP-1 372 as CC/C and CT/T in males had a 4.5-fold increased risk of IM, as compared to CC/T (p < .05). Females with such combination genotype as CC/T-carrier had a 3-fold risk of IM than males with CC/T (p < .05). In contrast, males' combination genotype as CC/C had a 3-fold risk of IM than females with CC/CC (p = .05).

CONCLUSIONS

The host MMP-9 -1562/TIMP-1 372 SNPs had gender differences in the risk of IM after H. pylori infection, and could possibly serve as a host factor to identify the risk group harboring gastric precancerous changes after H. pylori infection.

Effect of Helicobacter pylori infection on telomerase-associated genes, cell proliferation and apoptosis in gastric precancerous lesion

AIM: To analyze expression of human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT), c-Myc and proliferating cell nuclear antigen (PCNA) and their relationship, and to explore the mechanism of H pylori in gastric precancerous lesions.

METHODS: Thirty three cases of gastric precancerous lesions including 19 H pylori-positive cases and 14 H pylori-negative cases were included in the study. hTR was determined using in situ RNA hybridization; hTERT, c-Myc and PCNA were detected using streptavidin-peroxidase immunohistochemical method; apoptosis was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling.

RESULTS: The expression of hTR, hTERT and c-Myc were 63.2%, 68.4% and 47.4% in H pylori-positive group and 28.6%, 21.4% and 7.1% in H pylori-negative group (P < 0.01); the proliferation index (PI) and apoptotic index (AI) were significant higher in H pylori-positive group than in H pylori-negative group (17.5 ± 5.4 vs 8.3 ± 3.6, 17.7 ± 3.9 vs 9.2 ± 5.2, P < 0.01). There were significant correlations between hTERT and hTR (r_s = 0.45, P < 0.01), hTERT and c-Myc protein (r_s = 0.54, P < 0.01) in gastric precancerous lesions.

CONCLUSION: H pylori infection induces the over-expression of telomerase-associated genes, c-Myc and prompts cell proliferation and apoptosis in gastric precancerous lesions.

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.

Genetic polymorphisms in mediators of inflammation and gastric precancerous lesions

Chronic inflammation induced by Helicobacter pylori is a key process in gastric carcinogenesis. We hypothesized that genetic polymorphisms in important mediators of H. pylori-induced inflammation may influence the risk of developing various grades of precancerous lesions. We studied the associations between single nucleotide polymorphisms (SNPs) in cyclooxygenase 1 and 2 (PTGS1 and PTGS2), inducible nitric oxide synthase (NOS2A), interferon gamma (IFNG) and its receptor (IFNGR1), and risk of gastric precancerous lesions in a Venezuelan population characterized by high rates of H. pylori infection. We found no association of precancerous lesions with SNPs in PTGS1 and in IFNG. A nonsynonymous SNP of NOS2A (Ser608Leu) and an SNP located in the promoter of IFNGR1 (C-56T) were associated with higher risk of atrophic gastritis [odds ratio (OR)=1.37, 95% confidence interval (CI)=1.01-1.86, and OR=1.49, 95% CI=1.01-2.19, respectively]. Two SNPs of PTGS2 were associated with risk of dysplasia (OR=1.60, 95% CI=1.01-2.54, and OR=0.66, 95% CI=0.43-0.99). We conclude that genetic variability in the genes we studied does not play a major role in the early stages of gastric carcinogenesis.

Gastric cancer risk in patients with premalignant gastric lesions: a nationwide cohort study in the Netherlands

BACKGROUND & AIMS

A cascade of precursor lesions (eg, atrophic gastritis, intestinal metaplasia, and dysplasia) precedes most gastric adenocarcinomas. Quantification of gastric cancer risk in patients with premalignant gastric lesions is unclear, however. Consequently, endoscopic surveillance is controversial, especially in Western populations.

METHODS

To analyze current surveillance practice and gastric cancer risk in patients with premalignant gastric lesions, all patients with a first diagnosis between 1991 and 2004 were identified in the Dutch nationwide histopathology registry (PALGA); follow-up data were evaluated until December 2005.

RESULTS

In total, 22,365 (24%) patients were diagnosed with atrophic gastritis, 61,707 (67%) with intestinal metaplasia, 7616 (8%) with mild-to-moderate dysplasia, and 562 (0.6%) with severe dysplasia. Patients with a diagnosis of atrophic gastritis, intestinal metaplasia, or mild-to-moderate dysplasia received re-evaluation in 26%, 28%, and 38% of cases, respectively, compared with 61% after a diagnosis of severe dysplasia (P < .001). The annual incidence of gastric cancer was 0.1% for patients with atrophic gastritis, 0.25% for intestinal metaplasia, 0.6% for mild-to-moderate dysplasia, and 6% for severe dysplasia within 5 years after diagnosis. Risk factors for gastric cancer development were increasing severity of premalignant gastric lesions at initial diagnosis (eg, severe dysplasia, hazard ratio 40.14, 95% confidence interval 32.2-50.1), increased age (eg, 75-84 years, hazard ratio 3.75, 95% confidence interval 2.8-5.1), and male gender (hazard ratio 1.50, 95% CI 1.3-1.7).

CONCLUSIONS

Patients with premalignant gastric lesions are at considerable risk of gastric cancer. As current surveillance of these patients is inconsistent with their cancer risk, development of guidelines is indicated.

The chemokine network. II. On how polymorphisms and alternative splicing increase the number of molecular species and configure intricate patterns of disease susceptibility

In this second review on chemokines, we focus on the polymorphisms and alternative splicings and on their consequences in disease. Because chemokines are key mediators in the pathogenesis of inflammatory, autoimmune, vascular and neoplastic disorders, a large number of studies attempting to relate particular polymorphisms of chemokines to given diseases have already been conducted, sometimes with contradictory results. Reviewing the published data, it becomes evident that some chemokine genes that are polymorphic have alleles that are found repeatedly, associated with disease of different aetiologies but sharing some aspects of pathogenesis. Among CXC chemokines, single nucleotide polymorphisms (SNPs) in the CXCL8 and CXCL12 genes stand out, as they have alleles associated with many diseases such as asthma and human immunodeficiency virus (HIV), respectively. Of CC chemokines, the stronger associations occur among alleles from SNPs in CCL2 and CCL5 genes and a number of inflammatory conditions. To understand how chemokines contribute to disease it is also necessary to take into account all the isoforms resulting from differential splicing. The first part of this review deals with polymorphisms and the second with the diversity of molecular species derived from each chemokine gene due to alternative splicing phenomena. The number of molecular species and the level of expression of each of them for every chemokine and for each functionally related group of chemokines reaches a complexity that requires new modelling algorithms akin to those proposed in systems biology approaches.

Epidemiology of premalignant gastric lesions: implications for the development of screening and surveillance strategies

Gastric cancer is one of the most common cancers worldwide; however, gastric cancer incidence varies greatly between different geographic areas. As gastric cancer is usually diagnosed at an advanced stage, the disease causes considerable morbidity and mortality. To detect gastric carcinomas at an early and curable stage, screening and surveillance seem necessary. Premalignant gastric lesions are well known risk factors for the development of intestinal type gastric adenocarcinomas. In a multistep cascade, chronic Helicobacter pylori-induced gastritis progresses through premalignant stages of atrophic gastritis, intestinal metaplasia and dysplasia, to eventually gastric cancer. Therefore, this cascade may provide a basis for early detection and treatment of gastric cancer. Epidemiology of gastric cancer and premalignant gastric lesions should guide the development of screening and surveillance strategies, as distinct approaches are required in countries with low and high gastric cancer incidences.

Helicobacter pylori cytotoxin-associated genotype and gastric precancerous lesions

BACKGROUND

Helicobacter pylori infection is associated with the development of gastric cancer. Although infection with an H. pylori strain containing the cytotoxin-associated (cag A) gene (a marker for a pathogenicity island) may increase the risk of atrophic gastritis and gastric cancer, the relationship of variants in pathogenic H. pylori genes to the severity and progression of precancerous lesions is not well defined.

METHODS

Gastric biopsy specimens were obtained at enrollment from 2145 participants in a chemoprevention trial in Tachira State, Venezuela, and examined histologically to determine the severity of precancerous lesions. The presence of H. pylori DNA in gastric biopsies and the strain type according to presence or absence of the cagA gene were detected by polymerase chain reaction and specific probes. The relationship between H. pylori DNA and histologic diagnosis was analyzed by polytomous logistic regression. Rates of progression and regression of precancerous lesions were determined from biopsies from additional annual gastroscopies (mean follow-up = 3.5 years). All statistical tests were two-sided.

RESULTS

At enrollment, there was a strong association between cagA-positive H. pylori infection and the severity of gastric precancerous lesions, but cagA-negative H. pylori was associated only with chronic gastritis. Using individuals with normal mucosa or superficial gastritis as control subjects, the odds ratio for dysplasia was 15.5 (95% confidence interval [CI] = 6.42 to 37.2) in cagA-positive individuals compared with uninfected individuals and 0.90 (95% CI = 0.37 to 2.17) for individuals infected with cagA-negative H. pylori compared with uninfected individuals. Individuals infected with cagA-positive H. pylori appeared more likely to experience progression (and less likely to experience regression) of precancerous lesions than those infected with cagA-negative H. pylori, but the differences did not attain statistical significance.

CONCLUSIONS

This large epidemiologic study shows a strong relationship between the presence of H. pylori DNA in gastric biopsies and the severity of precancerous lesions that is specific to cagA-positive strains. The association between H. pylori and gastric carcinoma may have been previously underestimated due to the poor accuracy of serologic H. pylori markers and lack of discrimination by cagA genotype.