Apoptosis, proliferation and p53 gene expression of H. pylori associated gastric epithelial lesions

Correlation analysis of gastric mucosal lesions with Helicobacter pylori infection and its virulence genotype in Guiyang, Guizhou province, China

Background

Helicobacter Pylori (H. pylori) infection is the most important factor affecting clinical outcome in patients with gastric mucosal lesions. This study aimed to investigate H. pylori infection in patients with gastric mucosal lesions and their virulence genotype in Guiyang, China.

Methods

Pathological examinations of 1,364 biopsies from patients with upper gastrointestinal symptoms and H. pylori infection were analyzed according to different pathological types. The bacterial genome DNA was extracted from H. pylori strains isolated from gastric biopsies, and the cagA, vacA, and iceA virulence genes were detected and typed to analyze the correlation of their genotypes between different pathological lesions.

Results

The positive rate of H. pylori infection was approximately 19.9% (272/1,364), as determined by histopathological examination (HPE). It was more frequently detected in men than in women. A total of 85 H. pylori isolates were obtained from 280 clinical samples (positive rate 30.4%, 85/280). Of these 85 strains, cagA, vacA, and iceA genes were identified in 85.9%, 100%, and 83.5% of samples, respectively. Approximately 74.1% of strains were cagA East Asian type (cagA-ABD), and 11.8% of were cagA Western strains (cagA-AB, cagA-ABC), only present in patients with chronic non-atrophic gastritis. Gastric intraepithelial neoplasia and gastric cancer harbored both Asian strains. A total of 7 combinations of vacA genotypes were noted, among which s1c/m1b (30.6%) and s1c/m2 (41.2%) were the dominant genotypes. The predominant iceA genotype was iceA1 (64.7%).

Conclusions

We observed that the positive rate of H. pylori infection was related to the pathological type of patients' gastric mucosal lesions. Isolated H. pylori strains showed a unique genotype, mainly East Asian type cagA (ABD), vacA s1c/m2 genotype, and iceA1. These results provide an important reference for further studies of H. pylori in Guizhou province, China.

Helicobacter pylori infection and a P53 codon 72 single nucleotide polymorphism: a reason for an unexplained Asian enigma

AIM

P53, the most commonly mutated tumor suppressor gene in all types of human cancer, is involved in cell cycle arrest and control of apoptosis. Although p53 contains several polymorphic sites, the codon 72 polymorphism is by far more common. There are divergent reports but many studies suggest p53 pro/pro SNP may be associated with susceptibility to developing various cancers in different regions of the world. The present study aimed to find any correlation between H. pylori infection and progression of carcinogenesis, by studying apoptosis and the p53 gene in gastric biopsies from north Indian population.

MATERIALS AND METHODS

A total of 921 biopsies were collected and tested for prevalence of H. pylori by rapid urease test (RUT), imprint cytology and histology. Apoptosis was studied by the TUNEL method. Analysis of p53 gene polymorphism at codon 72 was accomplished by PCR using restriction enzyme BstU1.

OBSERVATION

Out of 921 samples tested 56.7% (543) were H. pylori positive by the three techniques. The mean apoptotic index (AI) in the normal group was 2.12, while gastritis had the maximum 4.24 followed by gastric ulcer 2.28, gastropathy 2.22 and duodenal ulcer 2.08. Mean AI in cases with gastric cancer (1.72) was less than the normal group. The analysis of p53 72 SNP revealed that p53 (Arg/Arg), (Pro /Arg) variant are higher (40.59% and 33.66%) as compared to p53 pro/pro variant (25.74%) in the healthy population.

CONCLUSIONS

The North Indian population harbors Arg or Pro/Arg SNP that is capable of withstanding stress conditions; this may be the reason of low incidence of gastric disease in spite of high infection with H. pylori. There was no significant association with H. pylori infection and AI. However, there is increased apoptosis in gastritis which may occur independent of H. pylori or p53 polymorphism.

Helicobacter pylori Infection Activates the Akt-Mdm2-p53 Signaling Pathway in Gastric Epithelial Cells

BACKGROUNDS AND AIMS

Although Helicobacter pylori is widely accepted as a causative factor of many gastric diseases, the signaling pathways affected by H. pylori and subsequent effects on cell apoptosis and proliferation remain unclear. Here, we investigated the molecular mechanisms mediating H. pylori infection in gastric epithelial cells.

METHODS

Tissues from 160 patients with various gastric diseases with or without H. pylori infection were obtained and analyzed by immunohistochemistry for Akt, pAkt, Mdm2, p53, and Bax expression. In vitro, human gastric epithelial cells, GES-1, were incubated with H. pylori culture filtrates. Cell viability was measured by MTT assay. Apoptosis was evaluated by Annexin V/PI double staining followed by flow cytometry, DNA electrophoresis, and comet assay. mRNA and protein expression was assessed by RT-PCR and Western blot analysis.

RESULTS

In patient tissues, H. pylori infection was associated with significantly elevated levels of pAkt in chronic nonatrophic gastritis (CNAG), Mdm2 in dysplasia, p53 in metaplastic atrophy (MA), and Bax in CNAG and MA. In vitro, H. pylori culture filtrates reduced GES-1 cell viability in a time- and dose-dependent manner, induced G0/G1 arrest, triggered apoptosis, and increased DNA fragmentation. Mdm2 and Bax mRNA expression and pAkt, Mdm2, p53, and Bax protein expression were significantly upregulated when treated with H. pylori culture filtrates. Akt inhibition by LY294002 decreased Mdm2 expression, upregulated p53, and enhanced H. pylori-induced growth inhibition of GES-1 cells.

CONCLUSIONS

These findings suggest that Akt-Mdm2-p53 signaling is involved in the molecular response of GES-1 cells to H. pylori infection.

Mitochondrial dependent apoptosis: ameliorative effect of flunarizine on ischemia-reperfusion of celiac artery-induced gastric lesions in the rat

OBJECTIVES

Ischemia-reperfusion is a major event for induction of cellular apoptosis. Apoptosis is due to the activation of death receptor and/or mitochondrial pathways. Mitochondrial permeability transition pore opening is the cause of apoptosis. In our present study, we tried to evaluate the role of flunarizine in ischemia and reperfusion of celiac artery-induced gastric lesion in the rat.

METHODS

The therapeutic potential of flunarizine was assessed by measuring the changes in gastric lesion index, biomarker (i.e., thiobarbituric acid reactive substance, reduced glutathione, superoxide dismutase, myeloperoxidase, and total calcium and protein content), and mitochondrial damage (i.e., adenosine triphosphate and deoxyribonucleic acid fragmentation content) in ischemia and reperfusion-induced gastric lesion model.

RESULTS

Medium and higher doses of flunarizine produced a significant (P<0.05) ameliorative effect which was observed from the assessment of all the above-mentioned parameters (i.e., increase in reduced glutathione, superoxide dismutase and decrease in thiobarbituric acid reactive substance, myeloperoxidase, and total calcium content). Similar results were also obtained from omeprazole and cyclosporine. In the pre-treated group, deoxyribonucleic acid fragmentation pattern has also indicated that a mitochondria-associated anti-apoptotic effect of flunarizine was responsible to prevent the ischemia and reperfusion of celiac artery-induced gastric lesion.

CONCLUSION

The gastroprotective effect of flunarizine may be produced due to its inactivation potential of mitochondrial permeability transition pore opening associated with anti-oxidative, calcium regulation along with its anti-apoptotic effect.

Possible association of Helicobacter pylori infection with laryngeal cancer risk: an evidence-based meta-analysis. Arch Med Res. 2008;39:625-628. [PMID: 18662596 DOI: 10.1016/j.arcmed.2008.04.008]

BACKGROUND

Infection with Helicobacter pylori (H. pylori) is a major cause of various gastric diseases and has been reported to play a role in the process of tumorigenesis and progression of gastric carcinoma. However, whether H. pylori infection increases susceptibilities to other cancers is not fully understood. Several studies have been devoted to the relationship between H. pylori infection and laryngeal cancer risk and have yielded conflicting results. In this study, we aimed to evaluate the possible association of H. pylori infection with laryngeal cancer risk.

METHODS

The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications. Extracted data were further analyzed by a systematic meta-analysis.

RESULTS

A total of 15 papers were identified. Of these, five case-control studies were selected. Laryngeal cancer risk for H. pylori infection was 2.03-fold (95% CI=1.28-3.23) (Z=3.00, p<0.01) compared with the controls.

CONCLUSIONS

The pooled data suggest infection with H. pylori as a possible risk factor for laryngeal cancer.

Relationship between precancerous gastric lesions and cell proliferation and apoptosis in a high-risk population

AIM: To evaluate the relationship between gastric lesions and cell proliferation and apoptosis activity.

METHODS: A total of 1523 subjects received an endoscopic examination and five biopsies were obtained from standard sites of the stomach. Expression of Ki-67 was assessed by immunohistochemistry, and apoptotic cells were detected with the terminal deoxynucleotide transferase mediated dUTP nick end-labeling (TUNEL) method.

RESULTS: Among the subjects screened by endoscopic examination, 93.8% had chronic atrophic gastritis, intestinal metaplasia or dysplasia. The prevalence rates of gastric lesions varied in different sites of the stomach. In the greater curvature of the body, the proportion of normal mucosa or superficial gastritis was 84.56%, but dysplasia was only 0.07%. In the angulus, the proportion of normal mucosa or superficial gastritis was reduced to 19.19%, while the proportion of dysplasia reached 5.26%. Furthermore, gastric lesions were positively associated with cell proliferation activity, showing a tendency to increase Ki-67 labeling index according to the severity of gastric lesions. However, no significant association was seen between gastric lesion and cell apoptosis (P = 0.159).

CONCLUSION: Advanced gastric lesions, such as intestinal metaplasia and dysplasia, tend to occur along the lesser curvature of stomach, where gastric cancer occurs. Imbalance in cell proliferation and apoptosis can be observed in advanced gastric lesions.

Correlations of Helicobacter pylori infection with the expression of basic fibroblast growth factor and fibroblast growth factor receptor-2 in gastric mucosa and their significances

AIM: To study the expression of basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor-2 (FGFR-2) in gastric mucosal epithelia with H. pylori infection and their significances in the carcinogenesis of stomach cancer.

METHODS: A total of 30 patients with chronic superficial gastritis (CGS), 29 with intestinal metaplasia (IM), 31 with dysplasia (Dys) and 55 with gastric cancer (GC) were included in this study. The expression of bFGF and FGFR-2 were assessed by immunohistochemistry (SP method). Rapid urease test and histological examination with Warthin-Starry were used to determine the status of H. pylori infection.

RESULTS: The expression of bFGF and FGFR-2 in CSG patients were significantly lower than those in the other patients (IM: χ² = 4.002, P < 0.05; χ² = 4.163, P < 0.05; Dys: χ² = 15.779, P = 0.000; χ² = 15.949, P = 0.000; GC: χ² = 24.110, P = 0.000; χ² = 18.736, P = 0.000). The expression of bFGF and FGFR-2 in IM patients were significantly lower than those in Dys and GC patients (Dys: χ² = 4.258, P < 0.05; χ² = 4.212, P < 0.05; GC: χ² = 7.786, P < 0.01; χ² = 4.687, P < 0.05). But there was no significant difference between Dys and GC patients. The positive rates of bFGF and FGFR-2 expression were significantly higher in H. pylori-infected IM and Dys patients than those in the patients without H. pylori infection (IM: χ² = 10.076, P < 0.01; χ² = 7.535, P < 0.01; Dys: χ² = 11.501, P < 0.01; χ² = 8.330, P < 0.01). The positive rates of bFGF and FGFR-2 expression in H. pylori-infected Dys patients were significantly higher than those in GC group (bFGF: χ² = 4.201, P < 0.05; FGFR-2: χ² = 3.982, P < 0.05), while no significant difference was found between GC and IM patients. The expression of bFGF in Dys and IM patients without H. pylori infection were significantly lower than that in GC patients (Dys: χ² = 5.736, P < 0.05; IM: χ² = 17.113, P = 0.000), and FGFR-2 expression in H. pylori-negative IM patients was significant lower than that in GC patients (χ² = 11.091, P < 0.05). No significant difference was found between H. pylori-negative Dys and GC patients.

CONCLUSION: H. pylori may induce over-expression of bFGF and FGFR-2 in gastric mucosal epithelia, which may play a vital role in the carcinogenesis of stomach cancer.

Extracellular signal-regulated kinase 1- and 2-mediated gastric mucosal injury and repair in gastric ischemia-reperfusion of rats

BACKGROUND

The current study was undertaken to investigate the time course of gastric ischemia-reperfusion (GI-R)-induced gastric mucosal injury and repair and whether extracellular signal-regulated kinase 1/2 (ERK1/2) were involved in GI-R-induced gastric mucosal injury and repair.

METHODS

Immunohistochemistry and Western blot analyses were used.

RESULTS

Gastric mucosal injury induced by ischemia alone was mild. However, the injury worsened after reperfusion, reaching a maximum at 1 h, and was accompanied by increased apoptotic cells and decreased proliferative cells. Then, the gastric mucosal cells began to repair the injury by enhanced proliferation, which peaked at 24 h after reperfusion, and by 72 h the damaged gastric mucosa was mostly repaired. The ERK1/2 (nonactivated ERK1/2) protein expression level and distribution profile showed no significant changes during the entire reperfusion phase, but the p-ERK1/2 (activated ERK1/2) level changed dramatically. The p-ERK1/2 protein level was decreased at 0.5 h after reperfusion began, and then gradually increased, peaking after 3 h of reperfusion; these changes in p-ERK1/2 occurred simultaneously in the cytoplasm and nucleus. On the other hand, inhibition of the activation of ERK1/2, induced by PD98059, a specific ERK1/2 upstream inhibitor, aggravated the gastric mucosal injury, and apoptosis was increased and proliferation was reduced in the gastric mucosal cells after the same duration of reperfusion.

CONCLUSIONS

Serious gastric mucosal damage involving apoptotic cells occurred rapidly at an early stage of reperfusion and was closely related to the suppression of ERK1/2 activation. The activated ERK1/2 signaling transduction pathway played an important role. Activated ERK1/2 participated in the regulation of gastric mucosal injury and repair induced by GI-R, and might be mediated by the inhibition of apoptosis and the promotion of proliferation in gastric mucosal cells.

Effects of Helicobacter pylori infection on gastric epithelial cell kinetics in patients with chronic renal failure

AIM

To evaluate the effects of Helicobacter pylori infection on gastric epithelial cell kinetics in patients with chronic renal failure (CRF).

METHODS

Forty-four patients were enrolled in this study and divided into four groups with respect to their Helicobacter pylori (H pylori) and CRF status. Groups were labeled as follows: 1a: normal renal function, H pylori negative (n = 12), 1b: normal renal function, H pylori positive (n = 11), 2a: CRF, H pylori negative (n = 10), 2b: CRF, H pylori positive (n = 11). Upper gastrointestinal endoscopy was done in all the patients involved in the study. During endoscopical investigation, antral biopsy specimens were taken from each patient. In order to evaluate the cell apoptosis and proliferation in gastric epithelial cells, Bax and proliferating cell nuclear antigen (PCNA) labeling indexes (LI) were assessed with immunohistochemical staining method.

RESULTS

For groups 1a, 1b, 2a, and 2b, mean Bax LI was identified as 34.4+/-13.7, 44.1+/-16.5, 46.3+/-20.5, 60.7+/-13.8, respectively and mean PCNA LI was identified as 36.2+/-17.2, 53.6+/-25.6, 59.5+/-25.6, 67.2+/-22, respectively. When the one-way ANOVA test was applied, statistically significant differences were detected between the groups for both Bax LI (P = 0.004 <0.01) and PCNA LI (P = 0.009 <0.01). When groups were compared further in terms of Bax LI and PCNA LI with Tukeyos HSD test for multiple pairwise comparisons, statistically significant difference was observed only between groups 1a and 2b (P = 0.006 <0.01).

CONCLUSION

In gastric epithelial cells, expression of both the pre-apoptotic protein Bax and the proliferation marker PCNA increase with H pylori infection. This increase is more evident in patients with uremia. These findings suggest that uremia accelerates apoptosis and proliferation in gastric epithelial cells.

Epstein-Barr virus (EBV) infection and p53 protein expression in gastric carcinoma

In the presented studies p53 protein expression was evaluated in samples of gastric carcinoma originating from 32 selected adult patients (with documented diagnosis of adenocarcinoma of the stomach and without the presence of Helicobacter pylori infection). Among the patients 14 individuals carried EBV-positive gastric carcinoma (group 1) while the 18 remaining patients carried EBV-negative gastric carcinoma (group 2). EBV infection was detected testing the tissue material for the presence of EBER by RNA in situ hybridization (ISH) and testing sera of the patients for EBV-specific antibodies. Expression of p53 protein was analysed using immunohistochemistry. Presence of p53 protein was noted in 9 (64.3%) cases of EBV-positive gastric cancer (group 1) and in 10 (55.5%) cases of EBV-negative gastric cancer (group 2). No significant differences were detected in the frequencies of p53 protein expression in the two studied groups. The results permit to conclude that abnormalities in p53 in gastric cancer are independent of EBV infection, even if EBV may participate in development of the tumour.

Cell proliferation and inflammation on biopsy samples with multifocal atrophic gastritis before and 1 year after Helicobacter pylori eradication

CONTEXT

Results of clinical trials that have assessed whether gastric cancer is preventable with Helicobacter pylori eradication therapy remain inconclusive. These trials have used atrophy, intestinal metaplasia, and dysplasia as histopathologic end points that reflect possible preneoplastic lesions. Trial results would be more compelling if cell proliferation and inflammatory markers improved simultaneously with histopathologic lesions.

OBJECTIVE

To study the presence of cell proliferation markers and type of inflammatory cells in biopsy specimens with gastritis, atrophy, and intestinal metaplasia before and 1 year after H pylori therapy and to determine if immunohistochemistry can be used to study these.

DESIGN

We evaluated 12 subjects with gastritis and 16 with gastritis and multiple foci of atrophy and intestinal metaplasia by using immunohistochemical assays for tumor suppressor protein p53, proliferation marker Ki-67, cell cycle regulator cyclin D1, T and B lymphocytes, macrophages, and TUNEL (terminal deoxynucleotide transferase deoxyuridine triphosphate nick end labeling) assay for apoptosis. The biopsy specimens were selected from a randomized clinical trial that studied improvement of histopathologic gastric lesions after H pylori eradication.

RESULTS

Groups of surface epithelial cells that expressed p53 and Ki-67 were observed more often in subjects with atrophy and intestinal metaplasia compared with those with gastritis alone. T lymphocytes in the lamina propria were frequently observed 1 year after treatment in subjects with atrophy and intestinal metaplasia.

CONCLUSIONS

Immunohistochemical assays for cell proliferation and inflammatory cell markers showed different distribution patterns in these gastric biopsy specimens. The presence of T lymphocytes and groups of cells that expressed proliferation markers in subjects with multiple foci of atrophy and intestinal metaplasia needs further study.

Helicobacter pylori induces apoptosis of rat gastric epithelial cells in vitro

AIM: To investigate the effect of Helicobacter pylori (H. pylori) sonicated extract on the apoptosis of rat gastric epithelial cells as well as the expression of apoptosis-related genes in vitro.

METHODS: H. pylori sonicated extract from strain Sydney SS-1 was cultured with OUMS-37, a kind of immortalized rat gastric cell lines. Apoptosis of the cells was confirmed according to specific changes of morphology and DNA ladder 24-48 h after co-incubation. The expression of P53 protein was detected by Western blotting and the expression of bax and bcl-2 mRNA were observed by Northern blotting.

RESULTS: The specific morphology of the cells such as shrinkage, condensation, margination of nuclear chromatin and apoptotic bodies were observed under light microscope. DNA ladder was manifested by fragment analysis. Western blotting showed a dose-dependent increased expression of wild-type P53 protein and Northern blotting showed a dose-pendent increased expression of bax mRNA and reduced expression of bcl-2 mRNA in the treated cells.

CONCLUSION: H. pylori sonicated extract induces the apoptosis in vitro through up-regulation of wild-type P53 protein and bax mRNA expression, and down-regulation of bcl-2 mRNA expression, suggesting that H. pylori infection may interrupt the balance between proliferation and apoptosis of the gastric epithelial cells, which plays a key role in gastric carcinogenesis.

Proton pump inhibitor co-therapy normalizes the increased cell turnover of the gastric mucosa both in NSAID and selective COX-2 users

Proton pump inhibitor (PPI) co-therapy is considered the best strategy in preventing gastrointestinal complications during non-steroidal anti-inflammatory drug (NSAID) treatment, but there is limited information available on its effect on gastric mucosal cell kinetics. To evaluate the effect of PPI co-therapy on gastric mucosa we investigated epithelial cell proliferation, apoptosis, epithelial growth factor receptor (EGFR) and p53 expression in patients on chronic non-selective NSAID or cyclooxygenase-2 selective inhibitor (COX-2) treatment. Gastric biopsies of the antrum were taken from 10-10 patients on chronic NSAID and COX-2, therapy prior and after 6 months PPI co-therapy, and 10 controls without any treatment. Cell proliferation, apoptosis, EGFR and p53 expression were measured by immunohistochemistry. At least 600 glandular epithel cells were encountered and results were expressed as % of total cells counted. We found increased cell proliferation in patients on chronic COX-2 but not on NSAID therapy. Patients on either NSAID or COX-2 therapy had an increased p53 and decreased EGFR expression. PPI therapy reversed not only the increased cell proliferation and p53 expression, but also the suppressed EGFR expression when administered as co-therapy. The fewer gastrointestinal side effects observed during chronic COX-2 therapy may partially be the result of the higher cell proliferation. This effect is not mediated by the EGFR pathway. PPI co-therapy normalizes the disturbed cell kinetics irrespective of NSAID treatment used.

Relationship between bcl-2 gene expression and cell proliferation and apoptosis in human gastric carcinomas

AIM: To investigate the relationship between bcl -2 gene expression levels in human gastric carcinoma and the frequency of tumor cell proliferation activity and apoptosis.

METHODS: In situ hybridization and immunohistochemistry methods were used to study the frequencies of expressions of bcl -2 gene and nuclear antigen of proliferating cells (PCNA) in 53 gastric carcinomas. Meanwhile, an in situ apoptotic cell detection (TUNEL method) was adopted to compare the number of apoptotic cells and PCNA with the Bcl -2 protein expression in each case.

RESULTS: Of the 53 gastric carcinomas, 41 and 43 expressed bcl -2 mRNA and Bcl -2 protein, which were count for 77.4% and 81.1% respectively. There was no significant difference between the positive rates obtained by these two methods. The apoptotic index of gastric carcinomas negatively related to PCNA index (r = -0.993, P < 0.01). With the increase of Bcl-2 protein expression , the cell proliferating activity increased but the apoptosis decreased in the tumor cells. Significant difference of cell proliferation and apoptosis existed between +++ group and ++ group of Bcl -2 protein expression (t = 2.552, 2.699, P < 0.05) as well as between the former two groups and the -, + group (t = 4.487, 3.975, 2.807, 3.094, 4.885, 5.816, 3.404, 3.895, P < 0.01) respectively.

CONCLUSION: The overexpression of bcl -2 gene inhibits cell apoptosis and excessive cell proliferation in the development and progress of gastric carcinomas.

Interferon-gamma cooperates with Helicobacter pylori to induce iNOS-related apoptosis in AGS gastric adenocarcinoma cells

Helicobacter pylori colonizes the human stomach and causes gastric disease. The resulting gastric damage is a multi-step process involving several molecular factors and different target cells. Th1 cytokines released by neutrophils and lymphoid cells that infiltrate gastric mucosa, nitric oxide production and inducible nitric oxide synthase (iNOS) are associated with immune activation and tissue injury. Many other molecular processes such as apoptosis, as well as angiogenic factors and integrins, are involved in H. pylori pathogenesis. We used cancer gastric cells AGS and MKN as experimental models to evaluate apoptotic rates, iNOS gene expression with and without the presence of interferon-gamma (IFN-gamma), placenta growth factor gene expression and alphav modulation. Our results show that AGS cells stimulated with H. pylori underwent apoptosis. Moreover, the addition of IFN-gamma caused a further increase in iNOS gene expression and in the apoptotic rates. We also found early modulation in PlGF and alphav expression, and noted that p53 and bax gene expression was involved in the apoptotic process. Taken together, these findings demonstrate that H. pylori employs a series of mechanisms to avoid the host defense and cause gastric mucosa damage. One H. pylori pathogenic mechanism for causing gastric damage is the induction of iNOS-dependent apoptosis that is strongly enhanced by IFN-gamma. Thus, data obtained indicate that Th1 cytokines such as IFN-gamma, via modulation of iNOS gene expression, may contribute to an increase in the pathogenicity of H. pylori infections.

Construction of expression systems for flaA and flaB genes of Helicobacter pylori and determination of immunoreactivity and antigenicity of recombinant proteins

AIM: To clone flagellin genes A (flaA) and B (flaB) from a clinical strain of Helicobacter pylori (H pylori) and to construct prokaryotic expression systems of the genes and identify immunity of the fusion proteins.

METHODS: The flaA and flaB genes from a clinical H pylori isolate Y06 were amplified by high fidelity PCR. The nucleotide sequences of target DNA amplification fragments from the two genes were sequenced after T-A cloning. The recombinant expression vector pET32a inserted with flaA and flaB genes was constructed, respectively. The expressions of FlaA and FlaB fusion proteins in E. coli BL21DE3 induced by isopropylthio-β-D-galactoside (IPTG) at different concentrations were examined by SDS-PAGE. Western blot using commercial antibodies against whole cell of H pylori and immunodiffusion assay using self-prepared rabbit antiserum against FlaA (rFlaA) or FlaB (rFlaB) recombinant proteins were applied to the determination of the fusion proteins immunity. ELISA was used to detect the antibodies against rFlaA and rFlaB in sera of 125 H pylori infected patients and to examine rFlaA and rFlaB expression in 98 clinical isolates of H pylori, respectively.

RESULTS: In comparison with the reported corresponding sequences, the nucleotide sequence homologies of the cloned flaA and flaB genes were from 96.28%-97.13% and 96.31%-97.73%, and their putative amino acid sequence homologies were 99.61%-99.80% and 99.41%-100% for the two genes, respectively. The output of rFlaA and rFlaB expressed by pET32a-flaA-BL21DE3 and pET32a-flaB-BL21DE3 systems was as high as 40%-50% of the total bacterial proteins. Both rFlaA and rFlaB were able to combine with the commercial antibodies against whole cell of H pylori and to induce rabbits to produce specific antibodies with the same 1:2 immunodiffusion titers after the animals were immunized with the two recombinant proteins. Ninety-eight and zero point 4 and 92.80% of the serum samples from 125 patients infected with H pylori were positive for rFlaA and rFlaB antibodies, respectively. One hundred percent and 98.98% of the 98 tested isolates of H pylori were detectable for rFlaA and rFlaB epitopes, respectively.

CONCLUSION: Two prokaryotic expression systems with high efficiency of H pylori flaA and flaB genes were successfully established. The expressed rFlaA and rFlaB showed satisfactory immunoreactivity and antigenicity. High frequencies of FlaA and FlaB expression in different H pylori clinical strains and the general existence of specific antibodies against FlaA and FlaB in H pylori infected patients strongly indicate that FlaA and FlaB are excellent antigen candidates for developing H pylori vaccine.

Association of glutathione S-transferase M1 and T1 genetic polymorphisms with Helicobacter pylori infection and gastric adenocarcinoma

AIM

To study the association of genetic polymPphisms of glutathione S-transferase M1 and T1 (GSTM1, GSTT1) with clinicopathological features of gastric adenocarcinoma(GAC) and Helicobacter pylPi (Hp) infection.

METHODS

All subjects were unrelated Han people in Hubei Province of China. Using multiplex PCR, we studied the genetic polymPphisms of the GSTM1, GSTT1 genes. Hp infection was determined by IgG antibodies to Hp in stPed serum samples using enzyme-linked immunosobant assay and 14C urea breath test.

RESULTS

The null genotype fP GSTM1 was mPe significantly common in GACs when compared with controls (x²=5.40, P <0.05), and mPe common in early stage of GACs when compared with controls too (x²=4.74, P <0.05). All the differences of the frequency of GSTM1 null genotype between advanced stage GACs P intestinal type carcinomas P diffuse type carcinomas and controls did not reach statistical significance. The null genotype fP GSTT1 was significantly mPe common among intestinal type GACs when compared with controls (x²=4.09, P <0.05), but all the differences of the frequency of GSTT1 null genotype between early stage GACs P advanced stage GACs P diffuse type carcinomas and controls did not reach statistical significance. The subjects carrying both of the null genotypes fP GSTM1 and GSTT1 had mPe than 3.38-fold risk fP developing GAC compared with the subjects carrying both of the nonull genotypes fP GSTM1 and GSTT1 (adjusted odds ratio, P=3.38,95 % confidence interval, CI=1.58-7.51). The null genotype fP GSTM1 was mPe significantly common among those patients with Hp positive GAC compared with Hp positive controls (x²=6.68, P <0.01).

CONCLUSION

The null genotype fP GSTM1 has an increased risk of GAC, and most tumPs are in early stage GACs. The null genotype fP GSTT1 is significantly related to the intestinal type GAC,but not significantly related to the tumP stage. Subjects carrying both of the null genotypes fP GSTM1 and GSTT1 have increased risks fP GAC, GSTM1 gene polymPphisms and Hp infection may interact with each other in the initialization of GAC.

Apoptosis-inducing effect of recombinant Caspase-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901

AIM: To investigate the apoptosis-inducing effect of Caspases-3 expressed by constructed eukaryotic vector on gastric cancer cell line SGC7901.

METHODS: PCR was employed to amplify the sequences of both small and large subunits of Caspases-3. Its products were separately cloned into the Sma I site of pBluescript KS⁺ to generate both plasmids pBS/SS and pBS/LS. The small subunit fragment was excised from plasmid pBS/SS with BamH I and then inserted into the BamH I site of plasmid pBS/LS preceding that of the large subunit to yield plasmid pBS/Rev-Caspase-3. Rev-Caspase-3 cDNA was excised with Kpn I + Xba I and then subcloned into plasmid pcDNA3.1 (+) to construct Rev-Caspase-3 eukaryotic expression vector pcDNA/Rev-Caspase-3, which was used to transiently transfect SGC7901 cell line. Cell count, MTT assay and electron microscopy were used to confirm the antiproliferation and apoptosis-inducing effect of Rev-Caspase-3 expression on gastric cancer cells.

RESULTS: Plasmid pBS/Rev-Caspase-3 and eukaryotic expression vector pcDNA/Rev-Caspase-3 were successfully constructed. SGC7901 cells were transiently transfected by either pcDNA/Rev-Caspase-3 or pcDNA3.1 (+) for 24, 48, 72, and 96 h respectively. Cell growth was measured by cell count and MTT assay. In cell count assay, the cell numbers were 1.8 × 10⁶, 1.55 × 10⁶, 2.0 × 10⁶, and 3.1 × 10⁶ in the experimental group and 2.5 × 10⁶, 3.1 × 10⁶, 4.0 × 10⁶, and 5.7 × 10⁶ in the control group at 24, 48, 72 and 96 h respectively. The growth of SGC7901 cells was suppressed by Rev-Caspase-3 in a time-dependent manner (P < 0.05). The results of MTT assay were similar to that of cell count (P < 0.05). The characteristics of apoptosis such as chromatin condensation, crescent formation and margination were seen and more obvious with time in the given-experimental period in the experimental group, but not easily observed in the control group.

CONCLUSION: The expression of Rev-Caspase-3 by the constructed eukaryotic vector can significantly induce apoptosis of gastric cancer cell line SGC7901, which may exhibit a potential way in gastric cancer gene therapy.

cagA and vacA genotype of Helicobacter pylori associated with gastric diseases in Xi’an area

AIM: To establish stock of clinical Helicobacter pylori (H. pylori) isolates, to perform cagA and vacA typing of these isolates, to evaluate the relationship between genotypes of cagA and vacA and upper gastrointestinal diseases and to assess the association of vacA genotypes with presence of the pathogenicity marker-cagA.

METHODS: Clinical H.pylori strains were isolated from the antrum of 259 patients in Clumbia agar. The isolated H. pylori strains were identified by histology, and16SrRNA PCR. CagA genotypes were detected by colony hybridization, the probe was derived from the cloned plasmid PcagA, and digested by EcoRI-HindIII and the isolated PcagA DNA fragment was radioactively labelled by the random priming method. vacA genes types (s,m)and subtypes (s1a, s1b, s2) were typed by PCR. Vacuolating toxin was detected with neutral red absorb test. The results were treated statistically by χ² test, t test, and rank sum test.

RESULTS: A total of 192 clinical H.pylori strains were isolated and the stock of Helicobacter pylori was established. The total positive rate of cagA was 87% in all gastric diseases, and 95% in gastric cancer group. There was a difference between gastric cancer group and the other groups (P < 0.05) except duodenal ulcer group. The expression of type s1 of vacA was more than type s2 (P < 0.05), and, the expression of type m1 was equal to type m2. In gastric cancer group, there was a difference between s1a and s1b (P < 0.05), and s1a was more than s1b. Vacuolating toxins were more in Xi’an area isolates.

CONCLUSION: The cagA⁺ vacA type s1 clinical isolates are more in Xi’an area, but this can not serve as an index to predict gastric cancer.

Identification of H. pylori strain specific DNA sequences between two clinical isolates from NUD and gastric ulcer by SSH

AIM: The genomes of Helicobacter pylori (H. pylori) from different individuals are different. This project was to identify the strain specific DNA sequences between two clinical H. pylori isolates by suppression subtractive hybridization (SSH).

METHODS: Two clinical H. pylori isolates, one from gastric ulcer (GU, tester) and the other from non-ulcer dyspepsia (NUD, driver), were cultured and the genomic DNA was prepared and submitted to Alu I digestion. Then two different adaptors were ligated respectively to the 5’-end of two aliquots of the tester DNA fragments and SSH was made between the tester and driver DNA. The un-hybridized tester DNA sequences were amplified by two sequential PCR and cloned into pGEM-T-Easy Vector. The tester strain specific inserts were screened and disease related DNA sequences were identified by dot blotting.

RESULTS: Among the 240 colonies randomly chosen, 50 contained the tester strain specific DNA sequences. Twenty three inserts were sequenced and the sizes ranged from 261 bp to 1036 bp. Fifteen inserts belonged to the H.pylori plasmid pHPO100 that is about 3.5 kb and codes a replication protein A. Other inserts had patches of homologous to the genes of H.pylori in GenBank. Various patterns of dot blots were given and no GU strain unique DNA sequences were found when 4 inserts were used as probes to screen the genomic DNA from 27 clinical isolates, 8 from GU, 12 from duodenum ulcer (DU), 4 from GU-DU, 2 from NUD and 1 from gastric cancer (GC). But a 670 bp DNA fragment (GU198) that was a bit homologous to the 3’-end of the gene of thymidylate kinase was positive in 7 GU strains (7/8), 3 GU-DU strains (3/4) and 3 DU strains (3/12). A 384 bp fragment (GU79) of the replication gene A (repA) was positive only in 4 H.pylori isolates, 2 from GU and 2 from GU-DU.

CONCLUSION: Differences exist in the genes of different H.pylori isolates. SSH is very effective to screen H.pylori strain specific DNA sequences between two clinical isolates, and some of these sequences may have clinical significance.

Expression of survivin in human gastric carcinoma and gastric carcinoma model of rats

AIM: To study the expression of survivin, an inhibitor of apoptosis protein, in human gastric carcinomas and gastric carcinoma models of rats.

METHODS: With the method of immunohistochemical staining, we studied the expression of survivin in 20 cases of chronic gastritis and 56 cases of gastric carcinomas. We used N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and high dose sodium-chloride diet to induce rat gastric carcinomas. Survivin expression was studied in glandular stomachs of normal rats, adenocarcinomas and tissues adjacent to the tumor, as well as in rats during the induction period.

RESULTS: Survivin was expressed in 27 of 56 (48.2%) cases of human gastric carcinoma tissues and 1 of 20 (5%) cases of chronic gastritis. It was found that the expression of survivin had no relation with the elements of age, tumor depth, tumor size, and disease stage, but was significantly related to histological type. The positive rate of survivin expression in cases of intestinal type was significantly higher than that in cases of diffuse type (P < 0.05). In animal experiments, survivin expression in glandular stomachs of normal rats, of rats in middle induction period, in adenocarcinomas and tissues adjacent to tumor were 0, 40.0%, 78.3% and 38.9%, respectively. Compared with the survivin expression in normal rats, the differences were significant.

CONCLUSION: These data imply that survivin plays an important role in the onset of gastric carcinoma and that high survivin expression is an early event of gastric carcinoma.

Construction of hpaA gene from a clinical isolate of Helicobacter pylori and identification of fusion protein

AIM: To clone hpaA gene from a clinical strain of Helicobacter pylori and to construct the expression vector of the gene and to identify immunity of the fusion protein.

METHODS: The hpaA gene from a clinical isolate Y06 of H. pylori was amplified by high fidelity PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The recombinant expression vector inserted with hpaA gene was constructed. The expression of HpaA fusion protein in E.coli BL21(DE3) induced by IPTG at different dosages was examined by SDS-PAGE. Western blot with commercial antibody against whole cell of H. pylori as well as immunodiffusion assay with self-prepared rabbit antiserum against HpaA fusion protein were applied to determine immunity of the fusion protein. ELISA was used to detect the antibody against HpaA in sera of 125 patients infected with H. pylori and to examine HpaA expression of 109 clinical isolates of H. pylori.

RESULTS: In comparison with the reported corresponding sequences, the homologies of nucleotide and putative amino acid sequences of the cloned hpaA gene were from 94.25%-97.32% and 95.38%-98.46%, respectively. The output of HpaA fusion protein in its expression system of pET32a-hpaA-BL21(DE3) was approximately 40% of the total bacterial proteins. HpaA fusion protein was able to combine with the commercial antibody against whole cell of H. pylori and to induce rabbit producing specific antiserum with 1:4 immunodiffusion titer after the animal was immunized with the fusion protein. 81.6% of the serum samples from 125 patients infected with H. pylori (102/125) were positive for HpaA antibody and all of the tested isolates of H. pylori (109/109) were detectable for HpaA.

CONCLUSION: A prokaryotic expression system with high efficiency of H. pylorihpaA gene was successfully established. The HpaA expressing fusion protein showed satisfactory immunoreactivity and antigenicity. High frequencies of HpaA expression in different H. pylori clinical strains and specific antibody production in H. pylori infected patients indicate that HpaA is an excellent and ideal antigen for developing H. pylori vaccine.

Primary adenocarcinomas of lower esophagus, esophagogastric junction and gastric cardia: in special reference to China

Gastric cardia adenocarcinoma (GCA) is an under-studied subject. The pathogenesis, molecular changes in the early stage of carcinogenesis and related risk factors have not been well characterized. There is evidence, however, that GCA differs from cancer of the rest of the stomach in terms of natural history and histopathogenesis. Adenocarcinomas of the lower esophagus, esophagogastric junction (EGJ) and gastric cardia have been given much attention because of their increasing incidences in the past decades, which is in striking contrast with the steady decrease in distal stomach adenocarcinoma. In China, epidemiologically, GCA shares very similar geographic distribution with esophageal squamous cell carcinoma (SCC), especially in Linzhou (formerly Linxian County), Henan Province, North China, the highest incidence area of esophageal SCC in the world. Historically, both GCA and SCC in these areas were referred to as esophageal cancer (EC) by the public because of the common syndrome of dysphagia. In Western countries, Barrett's esophagus is very common and has been considered as an important precancerous lesion of adenocarcinoma at EGJ. Because of the low incidence of Barrett's esophagus in China, it is unlikely to be an important factor in early stage of EGJ adenocarcinoma development. However, Z line up-growth into lower esophagus may be one of the characteristic changes in these areas in early stage of GCA development. Whether intestinal metaplasia (IM) is a premalignant lesion for GCA is still not clear. Higher frequency of IM observed at adjacent GCA tissues in Henan suggests the possibility of IM as a precancerous lesion for GCA in these areas. Molecular information on GCA, especially in early stage, is very limited. The accumulated data about the changes of tumor suppressor gene, such as p53 mutation, and ontogeny, such as C-erbB2, especially the similar alterations in GCA and SCC in the same patient, indicated that there might be some similar risk factors, such as nitrosamine, involved in both GCA and SCC in Henan population. The present observations also suggest that GCA should be considered as a distinct entity.

Role of inducible nitric oxide synthase expression in aberrant crypt foci-adenoma-carcinoma sequence

AIM: To investigate the expression of inducible nitric oxide synthase (iNOS) in aberrant crypt foci (ACF) -adenoma-carcinoma sequence and its relation with tumor cell apoptosis, proliferation and angiogenesis.

METHODS: The expression of iNOS, proliferating cell nuclear antigen (PCNA) and microvessel density (MVD) in different stages of colorectal cancer were studied by immunohistochemical method from 30 normal tissues, 30 nonhyperplastic ACF, 30 hyperplastic ACF, 30 dysplastic ACF, 30 adenomas and 60 carcinomas. The apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method using an Apop Tag in situ detection kit.

RESULTS: The immunoreactivity of iNOS significantly increased in the transition from hyperplastic ACF to dysplastic ACF. This transition was associated with a significant decrease in the apoptotic index (AI) (0.73 ± 0.37 vs 0.61 ± 0.35, P < 0.05) and significant increases in the PCNA labeling index (LI) (27.3 ± 2.80 vs 40.3 ± 3.11, P < 0.01) and microvessel density (MVD) (55 ± 11.5 vs 70 ± 13.2, P < 0.01). The expression of iNOS was in low levels and positively correlated with PCNA-LI (r = 0.812, P < 0.01) and MVD (r = 0.863, P < 0.01) during transition from normal mucosa to nonhyperplastic ACF and hyperplastic ACF. The expression of iNOS was in high levels and positively correlated with AI (r = 0.901, P < 0.01) after transition from hyperplastic ACF to dysplastic ACF, adenoma and carcinoma.

CONCLUSION: The results suggest that the transition from hyperplastic ACF to dysplastic ACF may be a crucial step in the ACF-adenoma-carcinoma sequence, in which iNOS plays an important role by regulating tumor cell apoptosis, proliferation and angiogenesis.

Expression of TFF2 and Helicobacter pylori infection in carcinogenesis of gastric mucosa

AIM: To investigate the expression of TFF2 and Helicobacter pylori infection in carcinogenesis of gastric mucosa.

METHODS: The expression of TFF2 was immunohistochemically analyzed in paraffin-embedded samples from 119 patients with endoscopic biopsy and subtotal gastrectomy specimens of gastric mucosal lesions, including 16 cases of chronic superficial gastritis (CSG), 20 chronic atrophic gastritis (CAG), 35 intestinal metaplasia (IM), 23 gastric epithelial dysplasia (GED) and 25 gastric carcinoma (CA), and Helicobacter pylori infection was detected by Warthin-Starry staining.

RESULTS: 1: TFF2 was located in the cytoplasm of gastric mucous neck cell. The expression of TFF2 was 100%, 100%, 0, 56.5% and 0 in CSGs, CAGs, IMs, GEDs and CAs, respectively. 2: The value of TFF2 positive cell density in CSG with Helicobacter pylori infection was higher than that without Helicobacter pylori infection. (52.89 ± 7.27vs 46.49 ± 13.04, P > 0.05); But the value of TFF2 positive cell density in CAG and GED with Helicobacter pylori infection was significantly lower than that without Helicobacter pylori infection (18.17 ± 4.09vs 37.93 ± 13.80, P < 0.01 and 14.44 ± 9.32vs 24.84 ± 10.22, P < 0.05).

CONCLUSION: Increase of TFF2 expression in CSG is perhaps associated with the protective mechanism after gastric mucosal injury. Decrease of TFF2 expression in CAG possibly attributes to the decrease in the number of gastric gland cell expressing TFF2. Re-expression of TFF2 in gastric epithelial dysplasia implies that TFF2 possibly contributes to the initiation of gastric carcinoma. The effect of Helicobacter pylori on the expression of TFF2 depends on the status of gastric mucosa.

Synergistic effects of nimesulide and 5-fluorouracil on tumor growth and apoptosis in the implanted hepatoma in mice

AIM: To compare the effect of nimesulide or/and 5-fluorouracil (5-FU) on tumor growth inhibition and apoptosis in mice with the implanted hepatoma and to observe their possible interactions.

METHODS: The inhibitory effects on tumor growth was evaluated by inhibition rate. Apoptosis was assessed by the ultrastructural, flow cytometry features and the DNA ladder demonstrated by agarose gel electrophoresis. PGE₂ level was determined by radioimmunoassay. Expression levels of c-jun, c-fos and p53 were evaluated by western blotting.

RESULTS: Nimesulide or 5-FU alone inhibited the growth of hepatoma, while a synergistic effect was observed for a combined use of both. More pronounced morphologic changes for tumor cell apoptosis and the DNA ladder were found for the latter treatment. Expression levels of c-jun and p53 were found to be elevated for the tumors from mice treated with nimesulide and 5-FU comparing to those with either of them, but a reduced PGE₂ level was observed only for the treatment with nimesulide. No change was detected on c-fos expression.

CONCLUSION: Nimesulide and 5-FU appear to have synergistic effects for the growth inhibition and apoptosis induction. Both were found to be overexpressed in p53 and c-jun proteins, rather than that of c-fos, associations with the resulted apoptosis.

Mutant p53 expression and apoptotic activity of Helicobacter pylori positive and negative gastritis in correlation with the presence of intestinal metaplasia

BACKGROUND

Mutation of the p53 gene is detectable in most cases of gastric cancer, as it is the most common genetic alteration in human malignancies. It is also well documented that Helicobacter pylori infection plays an important role in gastric carcinogenesis. There is still no clarification, however, concerning how genetic instability influences the homeostasis of gastric epithelium. We have studied the effect of H. pylori infection on apoptosis of the antral epithelium in the presence/absence of intestinal metaplasia and the expression of the p53 oncoprotein. The relationship between these two processes is analysed.

METHODS

Antral biopsies were taken from 36 patients who underwent routine upper endoscopy (17 men, 19 women, mean age 61.0 years). The biopsies were fixed in formalin and embedded in paraffin. Patients were classified into two histological groups: (1) as chronic gastritis without intestinal metaplasia (n = 19), and (2) chronic gastritis with intestinal metaplasia (n = 17). An immunohistochemical method was used to detect the expression of p53 oncoprotein, and the terminal transferase mediated dUTP nick end-labelling (TUNEL) method was used to detect apoptotic cells.

RESULTS

In the absence of intestinal metaplasia, both the apoptotic index (0.0272 +/- 0.011 vs 0.0128 +/- 0.006) and expresssion of p53 (35.55 +/- 31.16 vs 18.33 +/- 19.65) were significantly higher in H. pylori positive cases compared to H. pylori negative cases. In the presence of intestinal metaplasia, p53 expression was further increased (P < 0.05), but apoptosis was similar to that observed in H. pylori negative gastritis without intestinal metaplasia. In the presence of intestinal metaplasia, H. pylori infection did not influence apoptosis (0.013 +/- 0.004 vs 0.011 +/- 0.004), or p53 ratio (70.16 +/- 22.54 vs 68.50 +/- 28.96). In the sequence of gastritis-intestinal metaplasia the two indices show a close negative correlation (P < 0.05).

CONCLUSION

In the absence of intestinal metaplasia H. pylori infection increases both apoptotic activity and expression of p53 oncoprotein in the gastric mucosa. The lack of increased apoptosis with a higher p53 expression in the presence of intestinal metaplasia suggests an increased genetic instability and also may suggest that mutation of the p53 gene is an early step in the multistep process of gastric carcinogenesis.

TP53 and gastric carcinoma: a review

In this article, we survey the major p53 (TP53) alterations identified in gastric carcinomas and their precursors. These include p53 expression, mutations, and loss of heterozygosity (LOH). Not only are the various abnormalities summarized, but in addition there is a survey of the literature with respect to the impact of these changes on patient prognosis and treatment response. The majority of published studies involve the immunohistochemical detection of the protein. These use different antibodies, different detection techniques, and different methods of interpretation. Therefore not surprisingly, the results of many of the studies are contradictory with one another. Overall, however, it appears that p53 alterations occur early in the development of gastric carcinoma, being present even in the nonneoplastic mucosa and they increase in frequency as one progresses along the pathway of gastric carcinoma development. p53 immunoreactivity is seen in 17%-90.7% of invasive gastric carcinomas. p53 alterations occur much more commonly in proximal lesions than in distal ones, suggesting that the molecular events leading to the development of gastric carcinoma may be very different in proximal vs. distal tumors. p53 mutations occur in 0%-77% of gastric carcinomas. The mutations are distributed widely across the gene from exons 4-11 with hot spots of mutation at codons 175, 248, 273, 282, 245, and 213. G:C>A:T transitions at CpG sites are the commonest type of mutation. At least 60% of carcinomas with mutations also exhibit p53 LOH.

Expression of cyclooxygenase-2 in pancreatic cancer and its correlation with p53

AIM: To investigate the expressions of COX-2 and p53 in human pancreatic cancer and their correlation with biological behaviors of pancreatic cancer.

METHODS: The expressions of COX-2 and p53 in 51 specimens of human pancreatic ductal adenocarcinoma and 11 specimens of normal tissues adjacent human pancreatic ductal adenocarcinoma were detected with immunohistochemistry by Envision.

RESULTS: The detectable rate of COX-2 and p53 in pancreatic ductal adenocarcinoma were 74.5% and 60.8%, respectively; but none in adjacent normal tissues. The expression of COX-2 was significantly associated with the clinical stages and metastasis status of lymph nodes (P = 0.022, 0.036), but not with histological grade (P = 0.152). The expression of p53 was significantly correlated with the lymph node metastasis status (P = 0.035), but not with their histological grades and clinical stages (P = 0.131, 0.078). There was a significant correlation between the expression of COX-2 and p53 (r = 0.452, P = 0.001). Conditions such as age, sex, tumor size and location had no relation with expression of COX-2 or p53.

CONCLUSION: The cooperation of COX-2 and p53 may play a pivotal role in the carcinogenesis and the progression in pancreatic cancer. They may provide new targets for the therapy of pancreatic cancer.

TFF2 expression and H. pylori infection in gastric cancer tissues

AIM: To investigate the relationship between the expression of TFF2 and H. pylori infection in human gastric precancerous lesions and gastric cancer, and to explore the role of TFF2 and H. pylori in human gastric precancerous lesions and gastric cancer.

METHODS: The expression of TFF2 was immunohistochemic-ally analyzed in paraffin-embedded samples obtained by endoscopic biopsy and subtotal gastractomy specimens from 119 patients including chronic superficial gastritis(CSG, 16), chronic atrophic gastritis(CAG, 16), intestinal metaplasia(IM, 35), gastric epithelial dysplasia(GED, 23) and gastric cancer(CA, 25), and conditions of H. pylori infection were detected by means of Warthin-Starry staining.

RESULTS: TFF2 was located in the cell plasma of gastric mucous neck cells. The expressions of TFF2 were 100%, 100%, 0%, 56% and 0% in CSG, CAG, IM, GED and CA, respectively. The density of TFF2 positive cells was higher in CSG with H. pylori infection than that without H. pylori infection(52.9±7.3 vs 46.5±13.0, P > 0.05); but it was significantly lower in CAG and GED with H. pylori infection than that without H. pylori infection(18.2±4.1 vs 37.9±13.8, P < 0.01 and 14.4±9.3 vs 24.8±10.2, P < 0.05).

CONCLUSION: The high expression of TFF2 is associated with the protective mechanism after the gastric mucosal injury, the low expression of TFF2 in CAG might attribute to the decreased number of gastric gland cells secreting TFF2; but the re-expression of TFF2 in GED suggests that TFF2 is involved with the initiation of gastric cancer. The effect of H. pylori on the expression of TFF2 depends on the status of gastric mucosa.

Effect of Helicobacter pylori infection on bax protein expression in patients with gastric precancerous lesions

AIM: To evaluate the effect of Helicobacter pylori (H. pylori) infection on bax protein expression, and explore the role of H. pylori in the development of gastric carcinoma.

METHODS: H. pylori was examined by rapid urease test and Warthin-Starry method, and bax protein was examined by immunohistochemical staining in 72 patients with pre-malignant lesions.

RESULTS: Bax protein was expressed with different degree in intestinal metaplasia and gastric dysplasia, its positive rate being 63.9%. The positive rate of Bax protein expression in H. pylori-positive gastric precancerous lesions (72.3%) was significantly higher than that in H. pylori-negative gastric precancerous lesions (48.0%, x² = 4.191, P < 0.05). H. pylori infection was correlated well with the expression of Bax protein in gastric precancerous lesions(r = 0.978, P < 0.01). After eradication of H. pylori, the positive rate of bax protein expression was significantly decreased in H. pylori-positive gastric precancerous lesions(x² = 5.506, P < 0.05). In the persistent H. pylori infected patients, the positive rate of Bax protein expression was not changed.

CONCLUSION: H. pylori is involved in the expression of Bax gene. H. pylori infection increases the expression of Bax protein, this may be one of the mechanisms of H. pylori infection in the induction of gastric epithelial cell apoptosis. H. pylori might act as a tumor promoter in the genesis of gastric carcinoma. Eradication of H. pylori could inhibit the formation and development of gastric carcinoma.

Helicobacter pylori induces apoptosis in Barrett's-derived esophageal adenocarcinoma cells

Helicobacter pylori may protect against the development of dysplasia in Barrett's epithelium of patients with gastroesophageal reflux disease. The aim of this study was to determine whether H. pylori preferentially induces apoptosis in Barrett's-derived cancer cells compared to normal cells. A Barrett's-derived adenocarcinoma cell line (OE33) was grown. H. pylori wild-type, isogenic vacA-, cagA(-), and picB-/cagE- mutant strains were grown on agar plates. Intact or sonicated bacteria were used to treat normal and OE33 cells for 24 hours, and Hoechst dye binding was performed to measure apoptosis. FAS protein expression was determined by Western immunoblotting. OE33 cells treated with intact H. pylori wild-type strains produced significant (P < 0.05) dose-dependent increases in apoptosis compared to normal esophageal cells. H. pylori wild-type and vacA- isogenic strains were more effective than cagA- and picB-/cage- isogenic strains in inducing apoptosis in OE33 cells. In OE33 cells, H. pylori sonicates produced lower levels of apoptosis than intact bacteria. Wild-type H. pylori strains increased Fas protein expression in OE33 cells at 18 hours. H. pylori induced apoptosis at a higher rate in the Barrett's-derived human esophageal adenocarcinoma cells than in normal esophageal cells. The H. pylori-induced apoptosis was primarily dependent on intact bacteria and the presence of the cagA and picB/cagE gene products. H. pylori-induced apoptosis may involve the Fas-caspase cascade.

Expression of gastric cancer-associated MG7 antigen in gastric cancer, precancerous lesions and H. pylori-associated gastric diseases

AIM: To investigate the relationship between the antigen MG7 antigen expression and gastric cancer as well as precancerous condition; to study the relationship between the MG7 antigen expression and H. pylori infection in benign gastric lesions in order to find out the effect of H. pylori infection on the process of gastric cancer development.

METHODS: The level of MG7 antigen expression was determined by immunohistochemical method in 383 gastric biopsied materials. The intestinal metaplasia was determined by histochemistry method. The H. pylori infection was determined by HE stain, PCR and ELISA in 291 specimens, among which only 34 cases of H. pylori-associated gastric lesions were followed up.

RESULTS: The positive rate of MG7 expression in normal gastric mucosa, intestinal metaplasia, dysplasia and gastric cancer increased gradually in ascending order (P < 0.01). The positive rate of MG7 antigen expression in type III intestinal metaplasia of gastric mucosa was higher than that of type I and II intestinal metaplasia, being highly significant (P < 0.05). The positive rate of MG7 antigen expression in superficial gastritis, atrophic gastritis and gastric cancer increased gradually (11.9%, 64.8%, 91.2%, P < 0.01). There was no significant difference between H .pylori-negative and H. pylori-positive intestinal metaplasia, atrophic gastritis and dysplasia of gastric epithelium in the positive rate of MG7 antigen expression. There was no expression of MG7 antigen in H. pylori-negative superficial gastritis. The positive rate of MG7 expression in H. pylori-positive superficial gastritis was 20.5%, and the difference between them was significant (P < 0.05). During following up, one of the three H. pylori negative cases turned positive again, and its MG7 antigen expression turned to be stronger correspondingly. 3 of 31 H. pylori positive cases were detected as early gastric cancer, among which one with “+++” MG7 antigen expression was diminished after H. pylori eradication.

CONCLUSION: MG7 antigen expression is highly specific in gastric cancer and can be used as a good marker for screening of gastric cancer; type III intestinal metaplasia, atrophic gastritis and dysplasia should be followed up and MG7 antigen expression has high clinical value in the dynamic follow-up study; although the positive -MG7 in positive - H. pylori superficial gastritis show benign morphology in features, there is still the potential risk of developing into gastric cancer, hence special attention should be paid to those showing increasing MG7 antigen expression.

Intravenous chemotherapy for resected gastric cancer: meta-analysis of randomized controlled trials

AIM: To assess the safety and efficacy of different intravenous chemotherapeutic regimens in patients with gastric carcinomas who had undergone gastrectomy.

METHODS: A meta-analysis of all the relevant randomized controlled trials (RCTs) was performed. Language was restricted to Chinese and English. RCTs were identified from Medline and Embase (1980-2001/4), and Chinese Bio-medicine Database (1990-2001/1). Literature references were checked at the same time. We included randomized and quasi-randomized trials comparing the efficacy of intravenous chemotherapy after gastrectomy with that of surgery alone in patients with confirmed gastric carcinomas who had undergone gastrectomy. Selection criteria were: randomized or quasi-randomized trials with following-up results; Trials could be double-blind, single-blind or not blind; Chemotherapy groups were given intravenous chemotherapy after gastrectomy without neo-adjuvant chemotherapy, intraperitoneal hyperthermic perfusion, radiotherapy or chemoimmunotherapy; Controlled group included those receiving gastrectomy alone. The following data were extracted: the number of survival and death by the end of the follow-up; the different agents and doses of the intravenous chemotherapy; the baseline of the chemotherapy group and the controlled arm; the serious adverse events; the statistical consideration; cost-effectiveness analysis. The statistical analysis was performed by RevMan4.1 software which was provided by the Cochrane Collaboration. A P value of < 0.05 was considered statistically significant. Meta-analysis was done with random effects model. Heterogeneity was checked by chi-square test. Sensitivity analysis was performed by excluding the trials in which Jadad-scale was only 1 score. The result was expressed with odds ratio (OR) for the categorical variable.

RESULTS: Fourteen trials involving 4543 patients were included. Meta-analysis was done with random effects model Heterogeneity and sensitivity analysis were performed also. The effect of intravenous chemotherapy after gastrectomy was better than surgery alone (odds ratio 0.56, 95%CI 0.40-0.79). There was a significant difference between the two groups by u-test (P = 0.0008). Sensitivity analysis revealed the same difference (odds ratio 0.81, 95%CI 0.70-0.94). Of fourteen trials, only three studies were of high quality according to the Jadad-scale (with three score). There was one meta-analysis trial and the others, about ten trials, were of low quality. There was no trial which mentioned sample-size calculation, allocation concealment, intention-to-treat analysis. Most of the trials didn’t describe the blind-procedure. There were five trials which detailed the side-effects according to the toxicity grade by WHO standard. The side-effects halting treatment were haematologic and biochemical toxicity, debilitating nausea and vomiting. There were two patients died of chemotherapy toxicity.

CONCLUSION: Based on the review, intravenous chemotherapy after gastrectomy may have positive treatment effect on gastric cancer. However, the evidence is not strong because of the general low methodologic quality of the RCTs. Therefore, we can’t make the conclusion that intravenous chemotherapy after gastrectomy may have better treatment effect on gastric cancer than that of surgery alone. Rigorously designed, randomised, double-blind, placebo-controlled trials are required.

Ammonia-induced apoptosis is accelerated at higher pH in gastric surface mucous cells

Gastric luminal ammonia produced by Helicobacter pylori has been shown to cause gastric mucosal injury. This study was conducted to examine the mechanisms by which gastric luminal ammonia causes apoptosis of gastric epithelial cells. Monolayers of GSM06 cells, developed from murine gastric surface mucous cells, were cultured in the absence or presence of 10-30 mM NH(4)Cl at ambient pH of 5.0, 6.0, and 7.0. In the presence of luminal NH(4)Cl, GSM06 cells showed 1) cell shrinkage and nuclear chromatin condensation, 2) DNA fragmentation into oligonucleosomes, 3) leakage of cytochrome c into cytosolic fraction without affecting bax expression, and 4) increases in activity of caspases-3 and -9. These changes were accentuated when the cells were cultured at pH 7.0. In the absence of NH(4)Cl, none of these changes was detected at any pH examined. These results suggest that gastric luminal ammonia, at concentrations detected in H. pylori-infected subjects, induces apoptosis of gastric epithelial cells by release of cytochrome c from mitochondria, followed by activation of caspases-9 and -3, especially at higher ambient pH.

The point mutation of p53 gene exon7 in hepatocellular carcinoma from Anhui Province, a non HCC prevalent area in China

AIM: In hepatocellular carcinoma (HCC) prevalent areas of China, the point mutation of p53 exon7 is highly correlated with Hepatitis B virus (HBV) infection and aflatoxin B intake. While in non-HCC-prevalent areas of China, these factors are not so important in the etiology of HCC. Therefore, the point mutation of p53 exon7 may also be different than that in HCC-prevalent areas of China. The aim of this study is to investigate the status and carcinogenic role of the point mutation of p53 gene exon7 in hepatocellular carcinoma from Anhui Province, a non-HCC-prevalent area in China.

METHODS: PCR, PCR-SSCP and PCR-RFLP were applied to analyze the homozygous deletion and point mutation of p53 exon7 in HCC samples from Anhui, which were confirmed by DNA sequencing and Genbank comparison.

RESULTS: In the 38 samples of hepatocellular carcinoma, no homozygous deletion of p53 exon7 was detected and point mutations of p53 exon7 were found in 4 cases, which were found to be heterozygous mutation of codon 249 with a mutation rate of 10.53% (4/38). The third base mutation (GiúT) of p53 codon 249 was found by DNA sequencing and Genbank comparison.

CONCLUSION: The incidence of point mutation of p53 codon 249 is lower in hepatocellular carcinoma and the heterozygous mutation of p53 exon7 found in these patients only indicate that they have genetic susceptibility to HCC. p53 codon 249 is a hotspot of p53 exon7 point mutation, suggesting that the point mutation of p53 exon 7 may not play a major role in the carcinogenesis of HCC in Anhui Province, a non-HCC-prevalent area in China.

Inhibition of human telomerase in MKN-45 cell line by antisense hTR expression vector induces cell apoptosis and growth arrest

AIM: To investigate the effects of antisense human telomerase RNA (hTR) on the biologic behavior of human gastric cancer cell line: MKN-45 by gene transfection and its potential role in the gene therapy of gastric cancer.

METHODS: The hTR cDNA fragment was cloned from MKN-45 through RT-PCR and subcloned into eukaryotic expression vector (pEF6/V5-His-TOPO) in cis-direction or trans-direction by DNA recombinant methods. The constructed sense, antisense and empty vectors were transfected into MKN-45 cell lines separately by lipofectin-mediated DNA transfection technology. After drug selection, the expression of antisense hTR gene in stable transfectants and normal MKN-45 cells was detected by RT-PCR, the telomerase activity by TRAP, the apoptotic features by PI and Hoechst 33258 staining, the cell cycle distribution by flow cytometry and the population doubling time by cell counting. Comparison among the stable transfectants and normal MKN-45 cells was made.

RESULTS: The sense, antisense hTR eukaryotic expression vectors and empty vector were successfully constructed and proved to be the same as original design by restriction endonuclease analysis and sequencing. Then, they were successfully transfected into MKN-45 cell lines separately with lipofectin. The expression of antisense hTR gene was only detected in MKN-45 cells stably transfected with antisense hTR vector (named as MKN-45-ahTR) but not in the control cells. In MKN-45-ahTR, the telomerase activity was inhibited by 75%, the apoptotic rate was increased to 25.3%, the percentage of cells in the G0/G1 phase was increased to 65%, the proliferation index was decreased to 35% and the population doubling time was prolonged to 35.3 h. However, the telomerase activity, the apoptotic rate, the distribution of cell cycle, the proliferation index and the population doubling time were not different among the control cells.

CONCLUSION: Antisense hTR can significantly inhibit telomerase activity and proliferation of MKN-45 cells and induce cell apoptosis. Antisense gene therapy based on telomerase inhibition can be a potential therapeutic approach to the treatment of gastric cancer.