Factors contributing to the development of gastric cancer due to Helicobacter pylori infection

Interaction of cyclooxygenase-2 promoter polymorphisms with Helicobacter pylori infection and risk of gastric cancer

Overexpression of cyclooxygenase (COX)-2 has been implicated in the development of cancer. This study aimed to evaluate the relationship between genetic variants in COX-2 promoter interacting with Helicobacter pylori and the susceptibility to gastric cancer (GC). Three COX-2 polymorphisms -1290A>G (rs689465), -1195G>A (rs689466), and -765G>C (rs20417) were genotyped in 323 GC patients and 944 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression model. In GC patients, the ORs were 2.33 (95% CI = 1.50-3.63) and 2.70 (95% CI = 1.68-4.33) for -1195AA and -765CG genotype carriers, respectively. Haplotype analysis showed all -1195A allele-containing haplotypes, except G(-1290)-A(-1195)-G(-765), were associated with increased risk for GC, compared with the A(-1290)-G(-1195)-G(-765) haplotype. Moreover, significant multiplicative and additive interactions were observed between H. pylori infection and all these three polymorphisms, and H. pylori-infected subjects carrying the variant allele of -1290A>G, -1195G>A, or -765G>C had increased risk of GC compared with non-H. pylori-infected subjects with wild-type allele (OR = 4.10, 95% CI = 1.90-8.83; OR = 3.46, 95% CI = 1.31-9.11; and OR = 3.32, 95% = 1.27-8.73, respectively). Our results suggested that the COX-2 promoter polymorphisms were associated with increased risk of GC, especially interacting with H. pylori infection.

Helicobacter pylori gamma-glutamyl transpeptidase is a pathogenic factor in the development of peptic ulcer disease

BACKGROUND & AIMS

gamma-Glutamyl transpeptidase (GGT) has been reported to be a virulence factor of Helicobacter pylori associated with bacterial colonization and cell apoptosis. But its mechanism of pathogenesis is not firmly established. This study aims to examine its role in H pylori-mediated infection.

METHODS

Various H pylori isogenic mutants were constructed by a polymerase chain reaction (PCR) approach. H pylori native GGT protein (HP-nGGT) was purified with ion-exchange and gel-filtration chromatography. Generation of H2O2 was measured with fluorimetric analysis, whereas nuclear factor-kappaB (NF-kappaB) activation was determined by luciferase assay and Western blot. Cytokine production was examined by enzyme-linked immunoabsorbent assay and real-time PCR. DNA damage was assessed with comet assay and flow cytometry. The GGT activity of 98 H pylori isolates was analyzed by an enzymatic assay.

RESULTS

Purified HP-nGGT generated H2O2 in primary gastric epithelial cells and AGS gastric cancer cells, resulting in the activation of NF-kappaB and up-regulation of interleukin-8 (IL-8) production. In addition, HP-nGGT caused an increase in the level of 8-OH-dG, indicative of oxidative DNA damage. In contrast, Deltaggt showed significantly reduced levels of H2O2 generation, IL-8 production, and DNA damage in cells compared with the wild type (P<.05). The clinical importance of GGT was indicated by significantly higher (P<.001) activity in H pylori isolates obtained from patients with peptic ulcer disease (n=54) than isolates from patients with nonulcer dyspepsia (n=44).

CONCLUSION

Our findings provide evidence that GGT is a pathogenic factor associated with H pylori-induced peptic ulcer disease.

Promoter polymorphisms of IL2, IL4, and risk of gastric cancer in a high-risk Chinese population

Interleukin 2 (IL2) is a typical Th1 cytokine, and interleukin 4 (IL4) is an inducible Th2 cytokine. These cytokines are critical mediators of the Th1/Th2 balance and apoptosis potential and involved in the process of inflammation-mediated carcinogenesis in human organs, including the gastrointestinal tract. Therefore, we tested the hypothesis that functional variants in IL2 and IL4 were associated with risk of gastric cancer by genotyping two promoter polymorphisms in IL2 G-330T (rs2069762) and IL4 T-168C (rs2070874) in a case-control study of 1045 patients with incident gastric cancer and 1100 cancer-free controls in a high-risk Han Chinese population. We found that, compared with the IL4 -168TT genotype, heterozygous -168TC and combined -168TC/CC genotypes were associated with a significantly decreased gastric cancer risk [adjusted odds ratio (OR) = 0.81, 95% confidence interval (CI) = 0.67-0.98 for -168TC; OR = 0.83, 95% CI = 0.69-1.00 for -168TC/CC, respectively]. Furthermore, this significant protective effect was more evident for gastric cardia cancer patients (adjusted OR = 0.73, 95% CI = 0.56-0.95 for -168TC/CC vs. -168TT). For IL2 G-330T, subjects carrying GT/TT genotypes also had a significantly reduced risk of gastric cardia cancer (adjusted OR = 0.68, 95% CI = 0.46-0.99), compared with those carrying the GG genotype. Our results indicate that IL4 T-168C and IL2 G-330T promoter polymorphisms may contribute to the etiology of gastric cardia cancer in Chinese populations.

Novel interleukin-4 and interleukin-1 receptor antagonist gene variations associated with non-cardia gastric cancer in Japan: comprehensive analysis of 207 polymorphisms of 11 cytokine genes

BACKGROUND AND AIM

Helicobacter pylori (H. pylori)-induced chronic atrophic gastritis is a high-risk factor for gastric cancer. Immune responses to H. pylori are involved in gastric mucosal inflammation, and might affect clinical outcome, including the development of gastric cancer. The present study examines the significance of gene polymorphisms of various cytokines in the development of gastric cancer following H. pylori infection.

METHODS

One hundred Japanese non-cardia gastric cancer patients and 93 dyspeptic patients as controls were enrolled in the study (age range 50-75 years). All patients were positive for H. pylori. Genomic DNA was extracted from peripheral whole blood leukocytes, and we comprehensively analyzed 207 single nucleotide polymorphisms (SNP) in 11 cytokine genes; interleukin (IL)-1alpha, IL-1beta, IL-1 receptor antagonist (RN), IL-4, IL-4R, IL-8, IL-10, IL-12, TNF-alpha, TNF-beta, and IFN-gamma, using either invader assay (163 SNP), direct sequencing (22 SNP), or PCR-restriction fragment length polymorphism (22 SNP).

RESULTS

Among the 207 SNP examined, the IL-4 gene diplotypes (984 and 2983 AA/GA) had a significant negative association with gastric cancer development (odds ratio =0.3, 95% confidence interval =0.1-0.9). When we adopted the dyspeptic patients over 66 years of age as the controls, the IL-1RN gene diplotypes (-1102 and 6110 CG/GA) also had a significant negative association (odds ratio =0.2, 95% confidence interval =0.1-0.7).

CONCLUSION

A comprehensive analysis of 207 SNP of 11 cytokine genes revealed that variations in IL-4 and IL-1RN genes are negatively associated with the risk of developing gastric cancer following H. pylori infection. Distinct host cytokine responses in the gastric mucosa might have a role in H. pylori-induced carcinogenesis.

Th response to Helicobacter pylori differs between patients with gastric ulcer and duodenal ulcer

OBJECTIVE

Helicobacter pylori (H. pylori) infection induces both gastric (GU) and duodenal ulcers (DU). We examined whether host immunological response to H. pylori determines different disease outcomes.

MATERIAL AND METHODS

Thirty-two GU and 28 DU patients infected with H. pylori, and 24 dyspeptic patients without infection were enrolled. The constituents of cellular infiltrates in biopsies from each patient were determined and lymphokines secreted by stimulated T cells were measured. Serum concentrations of IgG subclasses specific to H. pylori were measured.

RESULTS

Low pepsinogen I and high pepsinogen II levels were observed in GU patients, while a high pepsinogen I level was found in DU patients. T cells predominate over other cell types in both GU and DU patients. GU patients had a higher number of T cells (p < 0.01) and lower plasma cells (p < 0.05) than those in DU patients. T cells from GU patients produced greater amounts of IFN-gamma and less IL-4 than those in DU patients (p < 0.01). GU patients had a higher serum level of IgG2 specific to H. pylori than that in DU patients (p < 0.01).

CONCLUSIONS

Th response by gastric T cells in GU patient was more polarized to Th1 as compared with that in DU patients, suggesting that a distinct immune response to H. pylori induces different disease outcomes.