Zun-Wu Zhang

Helicobacter pylori adherence to gastric epithelial cells: a role for non-adhesin virulence genes.

Helicobacter pylori is a major aetiological agent in gastroduodenal disorders and adherence of the bacteria to the gastric mucosa is one of the initial stages of infection. Although a number of specific adhesins has been identified, other H. pylori virulence factors may play a role in adherence to gastric epithelial cells directly or through interaction with other adhesins. This study assessed the effect of 16 H. pylori virulence factors on the adherence of the bacteria to gastric AGS cells and on gastric epithelial cell cycle distribution. Defined isogenic H. pylori SS1 mutants were used. After co-incubation of gastric AGS cells and bacteria, adherence of H. pylori to AGS cells was visualised by immunofluorescence microscopy and quantified by flow cytometry. Cell cycle phase distribution was analysed by flow cytometry with propidium iodide staining. Mutants were tested for their ability to adhere to AGS cells and compared with the wild-type SS1 strain. Mutations in genes in the cag pathogenicity island showed that cagP and cagE mutants adhered less than the wild-type strain to AGS cells, whereas a cagF mutant showed no reduction in adherence. Mutations in genes involved in flagellar biosynthesis showed that the adherence ability of fliQ, fliM and fliS mutants was reduced, but a flhB mutant possessed wild-type levels of adherence. Mutations in genes coding for the urease (ureB) and phospholipase (pldA) enzymes did not affect adherence, but mutation of the tlyA gene encoding an H. pylori haemolysin resulted in a reduced adherence. A fliQ mutant, with reduced adherence to AGS cells, was less able to induce AGS cell apoptosis than SS1. The ability to induce G0G1 cell cycle arrest was also abolished in the fliQ mutant. However, an increased cell number in S phase was observed when AGS cells were exposed to the fliQ mutant compared with SS1, suggesting that unattached bacteria may still be able to stimulate cell proliferation. In addition to known adhesins, other bacterial virulence factors such as CagE, CagP, FliQ, FliM, FliS and TlyA appear to play a role in H. pylori adherence to gastric epithelial cells. Mutations in these genes may affect H. pylori pathogenicity by reducing either the ability of the bacteria to attach to gastric epithelial cells or the intensity of bacteria-host cell interactions.

Gastric α-tocopherol and β-carotene concentrations in association with Helicobacter pylori infection.

OBJECTIVE The effects of Helicobacter pylori infection and its associated gastric histology on alpha-tocopherol and beta-carotene concentrations in serum, gastric juice and antral mucosa were investigated in patients undergoing routine gastroscopy for investigation of dyspepsia. METHOD Eighty-six patients were studied. High-performance liquid chromatography was used to measure alpha-tocopherol and beta-carotene concentrations. H. pylori infection was assessed by histology, bacterial culture, rapid urease test and serology. RESULTS No obvious association was found between age, sex, smoking or endoscopic diagnosis and alpha-tocopherol or beta-carotene concentrations in serum, gastric juice and antral mucosa. However, alcohol drinkers had significantly lower antral mucosal and gastric juice beta-carotene concentrations compared to non-drinkers. Gastric juice beta-carotene concentration was markedly lower in patients infected with H. pylori than uninfected controls (2.9 nmol/l (interquartile range 0.3-4.3) versus 4.6 nmol/l (interquartile range 3.5-7.6), P = 0.01), but there was no significant difference in serum or gastric mucosal beta-carotene concentrations between the two patient groups. The presence of gastric atrophy and intestinal metaplasia was significantly associated with reduced mucosal alpha-tocopherol and beta-carotene concentrations. Furthermore, antral mucosal alpha-tocopherol concentrations decreased progressively as antral mucosal histology changed from normal to chronic gastritis alone and finally to atrophy and intestinal metaplasia. CONCLUSION Gastric alpha-tocopherol and beta-carotene concentrations are affected by H. pylori-associated gastric histological changes, and these findings suggest that H. pylori infection may not only impair the protective role of vitamin C, but also of alpha-tocopherol and beta-carotene in the stomach.

Prognostic value of TP53 codon 72 polymorphism in advanced gastric adenocarcinoma

Purpose: A common polymorphism of the tumor suppressor gene TP53 at codon 72 has been associated with human cancer susceptibility. The prognostic role of the polymorphism was assessed in 102 patients with advanced gastric adenocarcinoma. Experimental Design: We followed up 102 consecutive Caucasian patients with advanced gastric adenocarcinoma for >5 years and determined the status of the TP53 codon 72 polymorphism in DNA samples extracted from archived gastric tissues. Results: The frequency of the arginine homozygous allele was positively correlated to patient age at baseline (P = 0.002). However, the age-related increase in the percentage of codon 72 arginine p53 was not correlated to the prognosis for gastric cancer patients. Multivariable analysis in patients who had surgery showed that baseline age may be inversely associated with patient survival (odds ratio, 1.1; 95% confidence interval, 1.0–1.2; P = 0.02). Furthermore, alcohol consumption may be associated with reduced survival (P = 0.06). Conclusions: These findings indicate that codon 72 arginine p53 may not be associated with a prolonged survival in patients with advanced gastric adenocarcinoma, but further study is needed to assess whether this polymorphism is associated with a late onset or slow progress of early gastric adenocarcinoma.

Topoisomerase I inhibitor (camptothecin)-induced apoptosis in human gastric cancer cells and the role of wild-type p53 in the enhancement of its cytotoxicity.

Camptothecin (CPT), a human topoisomerase I inhibitor, blocks DNA replication in human cancer cells. It represents a promising new class of chemotherapeutic agents with broad anti-tumor activity. However, its effect on gastric cancer cells remains unknown. We examined cell growth, apoptosis and cell cycle phase distribution in gastric cancer cells by exposing these cells to CPT for up to 72 h. Cell viability was determined by the Trypan blue exclusion assay. Cell cycle phase distribution and apoptosis were measured using flow cytometry, fluorescence microscopy and DNA ladder assay. Exposure of exponentially growing gastric AGS cancer cells to CPT induced time-dependent apoptosis and growth inhibition. Serum starvation-synchronized AGS cells (about 60% cells in G0/G1 phase) showed similar cellular responses. Analysis of cell cycle phase distribution of AGS cells treated with CPT for up to 72 h showed no obvious differences compared to untreated control cells. Although the induction of apoptosis was noticed in gastric cancer cell lines both with and without p53, cells lacking p53 showed less apoptosis compared to those cell lines possessing p53. Our data show that CPT is capable of inducing gastric cancer cell growth inhibition and apoptosis. Wild-type p53 may enhance the cytotoxicity of CPT against gastric carcinoma.

Role of Helicobacter pylori and p53 in regulation of gastric epithelial cell cycle phase progression

H. pylori disrupts gastric mucosal homeostasis by altering gastric epithelial cell cycle distribution, and this may contribute to the diverse disease outcomes associated with this infection. The effect of H. pylori on gastric epithelial cells and the role of p53 were assessed in this study by incubating H. pylori strains with gastric epithelial cells. During a 72-hr coincubation, H. pylori induced a time- and dose-dependent inhibition of cell growth and induction of apoptosis. However, at low inocula, H. pylori stimulates cell DNA synthesis compared to untreated controls. Although there was no difference in the induction of AGS cell line apoptosis and cell proliferation between cells exposed to cagA+/vacA+ and cagA−/vacA− strains, an interstrain variation on H. pylori-induced cell cycle events was noted. Serum starvation enhanced the sensitivity of gastric epithelial cells to H. pylori-induced apoptosis. H. pylori induced apoptosis in all the cell lines regardless of their p53 status, but cells with wild-type p53 had higher apoptosis rates. Therefore, bacterial density, diversity, local nutrient levels, and host cell p53 status may contribute to the regulation of H. pylori-induced cell cycle events.

Insulin-like growth factor binding protein-3: relationship to the development of gastric pre-malignancy and gastric adenocarcinoma (United Kingdom).

IGF family proteins play a pivotal role in regulating cell growth and apoptosis in normal and tumour tissues. IGFBP-3 is the major binding protein of IGFs and modulates the bioactivity of IGFs. To examine the role of IGFBP-3 in gastric cancer, an IGFBP3 promoter polymorphism, and serum and gastric mucosal levels of IGFBP-3 were assessed in two independent groups of patients (396 and 117 patients, respectively) with gastroduodenal diseases. There was no significant association between IGFBP-3 polymorphism and different gastroduodenal diseases (p = 0.6), but a significantly higher frequency of CC, a genotype related to lower levels of serum IGFBP-3 previously, were observed in patients with antral intestinal metaplasia when compared with those without this pre-malignancy (p = 0.04). Similarly, data from another independent group of patients further showed that patients with antral or corpus intestinal metaplasia had significantly lower serum levels of IGFBP-3 than those without these changes (p = 0.03 and 0.04, respectively). Furthermore, the percentage of positive IGFBP-3 staining in tumour tissue was significantly higher in patients with well or moderately differentiated tumours than those with poorly differentiated tumours (p = 0.04), indicating that IGFBP-3 may be associated with a better prognosis. In conclusion, our study suggests that IGFBP-3 may be protective against the development of gastric adenocarcinoma by preventing the formation of intestinal metaplasia and improve the prognosis of gastric cancer.

A Comparison Study of Gastric Cancer Risk in Patients with Duodenal and Gastric Ulcer: Roles of Gastric Mucosal Histology and p53 Codon 72 Polymorphism

Gastric ulcer is positively, and duodenal ulcer negatively, associated with the risk of gastric cancer. The relationship between a common p53 polymorphism at codon 72 and gastric cancer risk in patients with gastric and duodenal ulcer was examined in 397 Caucasian patients using PCR-RFLP. Noncardiac cancer patients had a distribution pattern of codon 72 genotypes similar to that of other non-cancer patient groups, though the frequency of the Pro/Pro genotype looks higher in duodenal ulcer. However, patients with cancer of the cardiac region had a significantly higher frequency of the Arg/Arg genotype than patients with chronic gastritis, duodenal ulcer, and noncardiac cancer. There was no significant difference in the distribution patterns between gastric ulcer and noncardiac or cardiac cancer or between gastric and duodenal ulcer. These findings may be a reflection of differences in the interaction between p53 codon 72 polymorphism and local factors in the stomach.