p16Ink4a is overexpressed in H. pylori-associated gastritis and is correlated with increased epithelial apoptosis

Background. Cell cycle regulatory proteins may be critical targets during carcinogenesis. We have previously shown that chronic H. pylori infection is associated with decreased expression of the cyclin dependent kinase inhibitor (CDI) p27^kip1. Loss of p27^kip1 and p16^Ink4a (p16) expression, another CDI, has been reported during the progression of gastric tubular adenomas to advanced gastric cancer. The aim of the current study was to examine whether H. pylori infection also affects the expression of p16 in the gastric mucosa of H. pylori‐infected patients. Methods. p16 expression was evaluated in gastric antral biopsies by immunohistochemistry in 50 patients with nonulcer dyspepsia (n = 18 uninfected, n = 32 H. pylori infected, 24 by cagA⁺ strains). Adjacent sections were stained for proliferating epithelial cells (by Ki67) and for apoptotic cells (by TUNEL assay). Results. Both in H. pylori infected and uninfected patients the expression of p16 was higher in the neck and base of the gland than in the foveolar region. Epithelial staining for p16 was increased with H. pylori infection (31.3% vs. 11.1% in the foveolar region, 68.8% vs. 27.8% in the neck and 75% vs. 50% in the glandular base). There was no correlation between the expression of 16 and proliferation but there was a significant positive correlation between apoptosis and 16 immunostaining. Conclusions. The tumor suppressor gene 16 is over expressed in gastric epithelial cells of H. pylori infected patients and this is associated with an increase in apoptosis. These findings suggest a possible role for this cell cycle regulator in the increase in gastric cell turnover that is associated with H. pylori infection.     

Expression of cagA,virB/D Complex and/or vacA Genes in Helicobacter pylori Strains Originating from Patients with Gastric Diseases

In order to better understand pathogenicity of Helicobacter pylori, particularly in the context of its carcinogenic activity, we analysed expression of virulence genes: cagA, virB/D complex (virB4, virB7, virB8, virB9, virB10, virB11, virD4) and vacA in strains of the pathogen originating from persons with gastric diseases. The studies were conducted on 42 strains of H. pylori isolated from patients with histological diagnosis of non-atrophic gastritis—NAG (group 1, including subgroup 1 containing cagA⁺ isolates and subgroup 2 containing cagA^- strains), multifocal atrophic gastritis—MAG (group 2) and gastric adenocarcinoma—GC (group 3). Expression of H. pylori genes was studied using microarray technology. In group 1, in all strains of H. pylori cagA⁺ (subgroup 1) high expression of the gene as well as of virB/D was disclosed, accompanied by moderate expression of vacA. In strains of subgroup 2 a moderate expression of vacA was detected. All strains in groups 2 and 3 carried cagA gene but they differed in its expression: a high expression was detected in isolates of group 2 and its hyperexpression in strains of group 3 (hypervirulent strains). In both groups high expression of virB/D and vacA was disclosed. Our results indicate that chronic active gastritis may be induced by both cagA⁺ strains of H. pylori, manifesting high expression of virB/D complex but moderate activity of vacA, and cagA^- strains with moderate expression of vacA gene. On the other hand, in progression of gastric pathology and carcinogenesis linked to H. pylori a significant role was played by hypervirulent strains, manifesting a very high expression of cagA and high activity of virB/D and vacA genes.     

Association of Malaysian Helicobacter pylori Virulence Polymorphisms with Severity of Gastritis and Patients' Ethnicity

Background and aim: Polymorphisms of Helicobacter pylori cagA and vacA genes do exist and may contribute to differences in H. pylori infection and gastroduodenal diseases among races in the Malaysian population. This study was conducted to characterize the polymorphisms in H. pylori cagA and vacA in Malaysian population. Methods: A total of 110 H. pylori isolates were genotyped by PCR and sequenced for cagA and PCR‐RFLP for vacA. Results: East Asian cagA was predominantly detected (64.5%), whereas vacA s1m1 and s1m2 alleles were detected in 60.9 and 37.3% of strains, respectively. A statistical association between cagA type with patients’ ethnicity (p < .0001) and age group >50 years old (p = .027) was identified. vacA alleles showed significant association with age group >50 years old (p = .017) and increased neutrophil activity in gastric mucosa (p = .028 and p = .016 for moderate and marked activity, respectively). Further identification of vacA polymorphism revealed that 84% of strains from Malays and Indians showed one RFLP pattern (RFLP‐1), whereas more than one RFLP patterns (RFLP‐2, 3, 4, 5, 6, and 8) were predominantly observed in strains from Chinese (82%) (p < .0001). Increasing severity of gastric inflammation was observed in gastric mucosa infected with strains carrying RFLP‐2, 3, 4, 5, and 6 (p = .037). About 86.6% of H. pylori strains with East Asian cagA were vacA RFLP‐2, 3, 4, 5, 6, and 8, and 88% of Western cagA strains were vacA RFLP‐1 (p < .0001). Chinese and Indians are susceptible to different virulence genotypes of H. pylori, whereas Malays showed a mixed virulence genotypes. Conclusion: Marked differences in the polymorphisms of cagA and vacA were observed among strains in Malaysian population. This provides a new insight into the pathogenicity of H. pylori in multiracial population.     

Helicobacter pylori infection in children and adults: a single pathogen but a different pathology

Background. The aims of this retrospective study were to ascertain in large series of children and adults: the relationship of the infecting strain to gastric mucosal lesions; and the relationship of the infecting strain to its duodenal localization. Materials and Methods. We studied 307 and 604 consecutive children and adults. In gastric mucosal samples H. pylori was cultured, genotyped and histologically assessed, while inflammation, activity and intestinal metaplasia were graded. In a subset of 171 patients H. pylori ureaseA (ureA) and cagA genes were amplified (PCR) using mucosal biopsies from the duodenum. Results. H. pylori infection was diagnosed in 40 children and 308 adults. cagA was identified in 50% and 65.5% of infected children and adults. Antral activity was associated with the density of infecting bacteria (p < .001) and with cagA (p < .01). Intestinal metaplasia was correlated with cagA (p < .001). The ureA gene was found in 56 duodenal samples from 82 H. pylori positive patients. Duodenal H. pylori ureA was significantly more frequent in patients with duodenal diseases than in those without (p < .01), cagA positive strains being mainly involved in the infection of this anatomical area (p < .01). Conclusions. A severe H. pylori‐associated gastritis is more prevalent when the density of infecting bacteria is high and when cagA positive strains cause the infection. The most virulent cagA positive H. pylori colonizes not only the gastric, but also the duodenal mucosa, which can be directly damaged by the bacteria itself or by its products.     

Detection of primary clarithromycin resistance of Helicobacter pylori and association between cagA + status and clinical outcome

Helicobacter pylori was examined in 110 patients (82 (74.5) with gastritis, 18 (16.4) with duodenitis, six (5.5) with duodenal ulcer and gastroesophageal reflux, and four (3.6 %) with normal) with gastrointestinal problems living in rural area, no history of macrolide use, and detected by culture (71.8) or direct detection from gastric biopsies by PCR (82.7 %). Also, cagA gene was identified using PCR and was found positive in 68/91 (74.7 %) strains. The prevalence of clarithromycin-resistant H. pylori was investigated by two methods including PCR–RFLP (7.7 (A2142G 1.1 and A2143G 6.6 %)) and twofold agar dilution (8.9 %) to detect phenotypic and genotypic status simultaneously. Among all the H. pylori positive patients, eight (8.8 %) isolates were found to be resistant to clarithromycin by at least one of the AD and/or PCR–RFLP methods. H. pylori positive rates were significantly correlated with patients' sex, age, and endoscopic findings (p?=?0.040, <0.001 and <0.001, respectively). There were no differences in gender or endoscopic findings related to cagA ⁺ and cagA ^? patients. The gene of cagA was not significantly helpful in predicting the clinical outcome of H. pylori infection alone. In conclusion, we revealed that there was a low prevalence of primer clarithromycin resistance in patients living in rural area with no history of macrolide use. The prevalence of mutant strains among the macrolide-resistant H. pylori varies even geographically between close provinces.     

High Diversity of vacA and cagA Helicobacter pylori Genotypes in Patients with and without Gastric Cancer

Background

Helicobacter pylori is associated with chronic gastritis, peptic ulcers, and gastric cancer. The aim of this study was to assess the topographical distribution of H. pylori in the stomach as well as the vacA and cagA genotypes in patients with and without gastric cancer.

Methodology/Principal Findings

Three gastric biopsies, from predetermined regions, were evaluated in 16 patients with gastric cancer and 14 patients with dyspeptic symptoms. From cancer patients, additional biopsy specimens were obtained from tumor centers and margins; among these samples, the presence of H. pylori vacA and cagA genotypes was evaluated. Positive H. pylori was 38% and 26% in biopsies obtained from the gastric cancer and non-cancer groups, respectively (p = 0.008), and 36% in tumor sites. In cancer patients, we found a preferential distribution of H. pylori in the fundus and corpus, whereas, in the non-cancer group, the distribution was uniform (p = 0.003). A majority of the biopsies were simultaneously cagA gene-positive and -negative. The fundus and corpus demonstrated a higher positivity rate for the cagA gene in the non-cancer group (p = 0.036). A mixture of cagA gene sizes was also significantly more frequent in this group (p = 0.003). Ninety-two percent of all the subjects showed more than one vacA gene genotype; s1b and m1 vacA genotypes were predominantly found in the gastric cancer group. The highest vacA-genotype signal-sequence diversity was found in the corpus and 5 cm from tumor margins.

Conclusion/Significance

High H. pylori colonization diversity, along with the cagA gene, was found predominantly in the fundus and corpus of patients with gastric cancer. The genotype diversity observed across systematic whole-organ and tumor sampling was remarkable. We find that there is insufficient evidence to support the association of one isolate with a specific disease, due to the multistrain nature of H. pylori infection shown in this work.     

Proteomics-Based Identification and Analysis of Proteins Associated with Helicobacter pylori in Gastric Cancer

Helicobacter pylori (H. pylori) is a spiral-shaped Gram-negative bacterium that causes the most common chronic infection in the human stomach. Approximately 1%-3% of infected individuals develop gastric cancer. However, the mechanisms by which H. pylori induces gastric cancer are not completely understood. The available evidence indicates a strong link between the virulence factor of H. pylori, cytotoxin-associated gene A (CagA), and gastric cancer. To further characterize H. pylori virulence, we established three cell lines by infecting the gastric cancer cell lines SGC-7901 and AGS with cagA⁺ H. pylori and transfecting SGC-7901 with a vector carrying the full-length cagA gene. We detected 135 differently expressed proteins from the three cell lines using proteome technology, and 10 differential proteins common to the three cell lines were selected and identified by LC-MS/MS as well as verified by western blot: β-actin, L-lactate dehydrogenase (LDH), dihydrolipoamide dehydrogenase (DLD), pre-mRNA-processing factor 19 homolog (PRPF19), ATP synthase, calmodulin (CaM), p64 CLCP, Ran-specific GTPase-activating protein (RanGAP), P43 and calreticulin. Detection of the expression of these proteins and genes encoding these proteins in human gastric cancer tissues by real-time PCR (RT-qPCR) and western blot revealed that the expression of β-ACTIN, LDH, DLD, PRPF19 and CaM genes were up-regulated and RanGAP was down-regulated in gastric cancer tissues and/or metastatic lymph nodes compared to peri-cancerous tissues. High gene expression was observed for H. pylori infection in gastric cancer tissues. Furthermore, the LDH, DLD and CaM genes were demethylated at the promoter -2325, -1885 and -276 sites, respectively, and the RanGAP gene was highly methylated at the promoter -570 and -170 sites in H. pylori-infected and cagA-overexpressing cells. These results provide new insights into the molecular pathogenesis and treatment targets for gastric cancer with H. pylori infection.     

Inactivation and Inducible Oncogenic Mutation of p53 in Gene Targeted Pigs

Mutation of the tumor suppressor p53 plays a major role in human carcinogenesis. Here we describe gene-targeted porcine mesenchymal stem cells (MSCs) and live pigs carrying a latent TP53^R167H mutant allele, orthologous to oncogenic human mutant TP53^R175H and mouse Trp53^R172H, that can be activated by Cre recombination. MSCs carrying the latent TP53^R167H mutant allele were analyzed in vitro. Homozygous cells were p53 deficient, and on continued culture exhibited more rapid proliferation, anchorage independent growth, and resistance to the apoptosis-inducing chemotherapeutic drug doxorubicin, all characteristic of cellular transformation. Cre mediated recombination activated the latent TP53^R167H allele as predicted, and in homozygous cells expressed mutant p53-R167H protein at a level ten-fold greater than wild-type MSCs, consistent with the elevated levels found in human cancer cells. Gene targeted MSCs were used for nuclear transfer and fifteen viable piglets were produced carrying the latent TP53^R167H mutant allele in heterozygous form. These animals will allow study of p53 deficiency and expression of mutant p53-R167H to model human germline, or spontaneous somatic p53 mutation. This work represents the first inactivation and mutation of the gatekeeper tumor suppressor gene TP53 in a non-rodent mammal.     

Mixed infection with cagA positive and cagA negative strains of Helicobacter pylori lowers disease burden in The Gambia

Background

The prevalence of Helicobacter pylori including strains with putatively virulent genotypes is high, whereas the H. pylori-associated disease burden is low, in Africa compared to developed countries. In this study, we investigated the prevalence of virulence-related H. pylori genotypes and their association with gastroduodenal diseases in The Gambia.

Methods and Findings

DNA extracted from biopsies and H. pylori cultures from 169 subjects with abdominal pain, dyspepsia or other gastroduodenal diseases were tested by PCR for H. pylori. The H. pylori positive samples were further tested for the cagA oncogene and vacA toxin gene.One hundred and twenty one subjects (71.6%) were H. pylori positive. The cagA gene and more toxigenic s1 and m1 alleles of the vacA gene were found in 61.2%, 76.9% and 45.5% respectively of Gambian patients harbouring H. pylori. There was a high prevalence of cagA positive strains in patients with overt gastric diseases than those with non-ulcerative dyspepsia (NUD) (p = 0.05); however, mixed infection by cagA positive and cagA negative strains was more common in patients with NUD compared to patients with gastric disease (24.5% versus 0%; p = 0.002).

Conclusion

This study shows that the prevalence of H. pylori is high in dyspeptic patients in The Gambia and that many strains are of the putatively more virulent cagA⁺, vacAs1 and vacAm1 genotypes. This study has also shown significantly lower disease burden in Gambians infected with a mixture of cag-positive and cag-negative strains, relative to those containing only cag-positive or only cag-negative strains, which suggests that harbouring both cag-positive and cag-negative strains is protective.     

Microbial Regulation of p53 Tumor Suppressor

p53 tumor suppressor has been identified as a protein interacting with the large T antigen produced by simian vacuolating virus 40 (SV40). Subsequent research on p53 inhibition by SV40 and other tumor viruses has not only helped to gain a better understanding of viral biology, but also shaped our knowledge of human tumorigenesis. Recent studies have found, however, that inhibition of p53 is not strictly in the realm of viruses. Some bacterial pathogens also actively inhibit p53 protein and induce its degradation, resulting in alteration of cellular stress responses. This phenomenon was initially characterized in gastric epithelial cells infected with Helicobacter pylori, a bacterial pathogen that commonly infects the human stomach and is strongly linked to gastric cancer. Besides H. pylori, a number of other bacterial species were recently discovered to inhibit p53. These findings provide novel insights into host–bacteria interactions and tumorigenesis associated with bacterial infections.     

Susceptibility to Helicobacter pylori infection: results of an epidemiological investigation among gastric cancer patients

The aim of this study was to identify the clinical, demographic, lifestyle factors and selected genetic polymorphisms that affect the susceptibility towards Helicobacter pylori (H. pylori) infection in gastric cancer patients. Histological confirmed gastric adenocarcinoma cases that underwent curative gastrectomy between 2002 and 2012 were included. Gastric biopsy samples were obtained to determine the H. pylori status, and further cagA status and vacA m and s genotypes by polymerase chain reaction. Patients were interviewed with structured questionnaires, and blood samples were collected for EPHX1, GSTM1, GSTT1, IL1B, IL1-RN, MTHFR and p53 genotyping. Proportions were compared in univariate analysis, while the relation between putative risk factors and H. pylori status and genotype were measured using logistic regression analysis. One hundred forty-nine gastric cancer patients were included, of which 78.5 % were H. pylori positive. Among positive patients 50 % were cagA+, 72.5 % vacA m1 and 80.7 % vacA s1. The presence of cagA was less frequent among vacA m1 (p = 0.031) and vacA s1 (p = 0.052) subtypes. The presence of father history for any cancer was a significant risk factor for H. pylori infection [adjusted odds ratio (OR) = 8.18, 95 % confidence interval (CI) 1.04–64.55]. EPHX1 exon 3 T > C (OR = 0.35, CI 95 % 0.13–0.94), IL1B-511 T > C (OR = 0.38, CI 95 % 0.15–0.97) and IL1-RN VNTR (OR = 0.19, CI 95 % 0.06–0.58) polymorphisms were protective towards H. pylori infection in the univariate analysis. Wine consumption was associated with higher risk of carrying the H. pylori vacA m1 virulent subtype (p = 0.034). Lastly, cardiovascular diseases were less common among cagA positive subjects (p = 0.023). Father history of any cancer is a risk factor for H. pylori infection. Polymorphisms in IL1B-511, IL1-RN and EPHX1 exon 3 genes might be protective towards H. pylori infection.     

Infection of less virulent Helicobacter pylori strains in asymptomatic healthy individuals in Thailand as a potential contributing factor to the Asian enigma

In Thailand, gastric cancer incidence is considerably low despite the high prevalence of Helicobacter pylori infection. We investigated the prevalence of H. pylori infection and the genotypes of cagA by using 179 stool specimens obtained from asymptomatic Thai individuals. In this study, the prevalence of H. pylori infection was 43.6%, and the detection rate of cagA-positive strains was 43.5%. In addition, the proportion of the highly virulent East-Asian type of cagA was 7.2%. These results indicate that the low prevalence of cagA-positive H. pylori strain as well as the low prevalence of East-Asian genotype cagA-positive strains may contribute to the low gastric cancer incidence.     

Real-time in vivo imaging of p16Ink4a reveals cross talk with p53

Expression of the p16^Ink4a tumor suppressor gene, a sensor of oncogenic stress, is up-regulated by a variety of potentially oncogenic stimuli in cultured primary cells. However, because p16^Ink4a expression is also induced by tissue culture stress, physiological mechanisms regulating p16^Ink4a expression remain unclear. To eliminate any potential problems arising from tissue culture–imposed stress, we used bioluminescence imaging for noninvasive and real-time analysis of p16^Ink4a expression under various physiological conditions in living mice. In this study, we show that oncogenic insults such as ras activation provoke epigenetic derepression of p16^Ink4a expression through reduction of DNMT1 (DNA methyl transferase 1) levels as a DNA damage response in vivo. This pathway is accelerated in the absence of p53, indicating that p53 normally holds the p16^Ink4a response in check. These results unveil a backup tumor suppressor role for p16^Ink4a in the event of p53 inactivation, expanding our understanding of how p16^Ink4a expression is regulated in vivo.     

Long-term Helicobacter pylori infection in Japanese monkeys induces atrophic gastritis and accumulation of mutations in the p53 tumor suppressor gene

Background. Helicobacter pylori is accepted as a definite human gastric carcinogen from an epidemiological point of view despite insufficient experimental data. Although we previously showed that the number of p53 immunopositive cells in the atrophic gastric mucosa of H. pylori‐infected Japanese monkeys gradually increased over time, data on p53 gene mutations were not obtained in that study. To obtain direct evidence of carcinogenesis associated with H. pylori infection, we investigated whether p53 gene mutations are present in the gastric mucosa of a nonhuman primate model susceptible to H. pylori. Materials and Methods. Using the DNA from gastric tissues obtained from six H. pylori‐uninfected monkeys of different ages, nucleotide sequence of the wild‐type p53 gene was determined by amplification of exons (Ex) 5, 6, 7 and 8 and sequencing. Gastric specimens obtained from eight Japanese monkeys that had been infected with H. pylori for different lengths of time (1.5–7.5 years), were analyzed for mutations in exons 5–8 of p53. Results. In the six H. pylori‐uninfected monkeys, nucleotide sequences of p53 Ex 5–8 were completely common and no mutations were noted. However, among the monkeys that were infected with H. pylori over various periods of time, there was an accumulation of p53 nucleotide (amino acid) substitutions as the gastric atrophy score increased. Conclusions. We conclude that the appearance of p53 gene mutation may be closely associated with the degree of gastric mucosal atrophy, which depends on the duration of H. pylori infection. Searching for p53 gene mutations may be useful for studying the progression of gastric carcinogenesis associated with H. pylori.     

Serological Indicators of Helicobacter pylori Infection in Adult Dyspeptic Patients and Healthy Blood Donors

The levels of IgM, IgG and IgA antibodies reacting with two Helicobacter pylori antigens (glycine acid extract (GE) and a recombinant CagA protein) were determined in the sera from adult dyspeptic patients, positive (H.p.⁽⁺⁾) or negative (H.p.^(-)) for H. pylori urease/culture, and from healthy blood donors. All sera were also examined against GE by Western blot (immunoblot) technique. Similar levels of anti-GE IgG were detected in the sera from all H.p.⁽⁺⁾ and almost all H.p.^(-) patients and from over 40% of the healthy volunteers. In contrast, higher levels of anti-GE IgA were found in the sera from patients than that from healthy subjects, although such antibodies were not detected in the sera from 30% of the H.p.⁽⁺⁾ patients. In general, our results suggest that a combination of ELISA and immunoblot may be more sensitive in the detection of H. pylori infection in dyspeptic patients than the examination of biopsy specimens by culturing or histology.     

TLR4 and TLR2 expression in biopsy specimens from antral and corporal stomach zones in Helicobacter pylori infections

Background:

It is not yet known which types of Toll-like receptors (TLRs) are most effective in Helicobacter pylori (H. pylori) recognition. It is also not known which gastric zones have the most prominent roles in TLR-mediated bacterial recognition. The aim of this work was to analyze the expression of TLR2 and TLR4 in biopsy specimens from H. pylori-infected patients.

Methods:

Thirty-eight patients with gastrointestinal disorders were divided into four groups in this study. The groups were: (A) H. pylori infection and peptic ulcer (n=15), (B) peptic ulcer only (n=5), (C) H. pylori infection only (n=10) and (D) control, with neither H. pylori infection nor peptic ulcer (n=8). Biopsy specimens from sites of redness or atrophic mucosa from gastric antrum and body in patients with gastritis were collected. RNAs from the antrum and body specimens were isolated. TLR2 and TLR4 mRNA expression was assessed by RT-PCR and quantified as densitometric ratios of TLR2 and TLR4/β-actin mRNA.

Results:

In the antral zones of H. pylori-infected patients (Groups A and C) TLR2 and TLR4 expression was significantly greater than in uninfected patients (Groups B and D) regardless of peptic ulcers (p < 0.05). In the gastric body samples TLR2 expression was significantly greater in Group C (H. pylori infection only) than in Group B (peptic ulcer only) and TLR4 expression was significantly greater in group A (H. pylori infection and peptic ulcer) than in Group B (peptic ulcer only) (p < 0.05). No significant differences in expression of TLR4 and TLR2 were observed between samples from the antrum and body in same groups.

Conclusions:

We conclude that H. pylori infection leads to significant increase in TLR2 and TLR4 molecules expression in antral region related to the control group. Considering the stimulatory effect of H. pylori on TLRs expression in the gastric tissue, we assume that colonization of H. pylori infection might occurs more in the gastric antral region than in the gastric body.Key Words: Helicobacter pylori, Toll-like receptors, TLR4; TLR2, Peptic ulcer     

Helicobacter pylori CagA Status,Mucosal Oxidative Damage and Gastritis Phenotype: A Potential Pathway to Cancer?

Background. Oxidative DNA damage is associated with Helicobacter pylori infection, atrophy and intestinal metaplasia. H. pylori‐cagA‐positive strains are associated with the highest risk of gastric cancer. Aims. To ascertain whether cagA‐positive H. pylori infection correlates with higher concentrations of 8OHdG and the presence of precancerous changes. Patients and Methods. 118 patients were studied (65M/53F, age 61 ± 14 years). Twelve were H. pylori‐negative. Among the H. pylori‐positive patients, 34 were cagA‐positive and 40 were cagA negative. In 32 patients H. pylori had been eradicated at least 6 months before endoscopic sampling. The phenotype of the gastritis (atrophic compared with nonatrophic, with and without intestinal metaplasia) was scored in biopsy samples obtained from the antrum, corpus, and angularis incisura. In antral biopsy samples, 8‐hydroxydeoxyguanosine was assessed by HPLC (electrochemical detector). CagA status was determined by PCR. Results. The highest scores for both mononuclear inflammation and activity of gastritis were significantly associated with cagA status (p = 0.036 antrum and p = 0.02 corpus). cagA‐positive infection significantly correlated with a higher prevalence of atrophic‐metaplastic lesions (p = 0.04). cagA‐positive patients had higher 8‐hydroxydeoxyguanosine levels than both cagA‐negative and H. pylori‐negative cases (p = 0.01). The 8‐hydroxydeoxyguanosine levels were significantly higher in multifocal atrophic gastritis (p = 0.04). The odds ratio for cagA‐positive patients having 8OHdG levels above a cut‐off calculated on the basis of the ROC curves were 7.12, overall, reaching 11.25 when only patients younger than 50 were considered. Conclusions. cagA‐positive patients were characterized: first, for higher scores for gastritis, activity and atrophic and metaplastic lesions; and second for greater oxidative DNA damage overall, at younger age and in the presence of multifocal atrophy. This setting may represent a cancer‐prone biological context.