Gastrin-mediated alterations in gastric epithelial apoptosis and proliferation in a mastomys rodent model of gastric neoplasia

Occurrences and phenotypes of RIPK3-positive gastric cells in Helicobacter pylori infected gastritis and atrophic lesions

BACKGROUND

Research evidences suggest that diverse forms of programmed cell death (PCD) are involved in the helicobacter pylori (H. pylori)-induced gastric inflammation and disorders.

AIMS

To characterize occurrences and phenotypes of necroptosis in gastric cells in H. pylori infected gastritis and atrophic specimens.

METHODS

Occurrences and phenotypes of necroptosis in gastric cells were immunohistochemically characterized with receptor-interacting protein kinase 3 (RIPK3) antibody in both human H. pylori infected gastric gastritis, atrophic specimens, and transgenic mice.

RESULTS

Increased populations of RIPK3-positive cells were observed in both gastric glands and lamina propria in H. pylori infected human oxyntic gastritis and atrophic specimens. Phenotypic analysis revealed that many RIPK3-positive cells were H ⁺ K⁺ ATPase-positive parietal cells in the gastric glands and were predominantly CD3-positive T lymphocytes, CD68-positive macrophages, and SMA-alpha-positive stromal cells in the lamina propria. Furthermore, we found an increased expression of RIPK3-positive gastric glandular cells along with the histological process of hyperplasia-atrophy-dysplasia progression in hypergastrinemic INS-GAS mice.

CONCLUSIONS

An increased population of RIPK3-positive cells was observed in several types of gastric cells, future studies that define the effects and mechanisms of PCD implicated in the development of H. pylori induced gastric disorders are needed.

Topical issues of prevention of stomach cancer: A review

Prevention of gastric cancer, both primary and secondary, is an extremely important component of the management of gastroenterological patients. The correct collection of anamnesis with an assessment of the hereditary (family) cancer risk, the action of risk factors (eating disorders, habitual/chronic intoxication, obesity, Helicobacter pylori infection, etc.), as well as the use of gastroprotectors (in particular, the drug Regastim Gastro), especially in persons with potentially precancerous the condition is chronic atrophic gastritis. According to the data of a double-blind placebo-controlled randomized study Regastim Gastro (active ingredient alpha-glutamyl tryptophan) in the treatment of chronic atrophic gastritis, it was found that this drug has a powerful anti-inflammatory effect and regenerative activity. Taking the drug Regastim Gastro, compared with placebo, statistically significantly contributed to a decrease in the number of inflammatory infiltration cells per 1 mm2 of the gastric mucosa. Regastim Gastro decreases in eosinophilic (3 times) and neutrophilic (4 times) infiltration of the gastric mucosa and also reduced the number of macrophages, lymphocytes and plasmocytes. In addition to anti-inflammatory properties, the drug also had a pronounced regenerative effect. Taking of Regastim Gastro statistically significant (p=0.028) increases in the number of glands per 1 mm2 of the gastric mucosa by 26.1% compared with the initial screening indicators. In the group of patients taking placebo, on the contrary, there was a further progression of the pathological process, accompanied by a decrease in the number of glands per 1 mm2 of the gastric mucosa after the end of treatment in comparison with the initial indicators. After the course of therapy, the number of glands per 1 mm2 of the gastric mucosa in patients taking the drug Regastim Gastro was statistically significantly higher in comparison with the results in the placebo group (p=0.013). After the course of Regastim Gastro, there was an improvement in acid production: a shift in the acidic side of the average pH value (1.6 times) and an increase in the value of the acidity index, both when compared with the initial values (5.4 times) and in comparison with the placebo group (2.9 times). The intake of Regastim Gastro to patients with gastritis, both H. pylori (+) and H. pylori (-) before the development of atrophy of the gastric mucosa can reduce the inflammatory factor, prevent the occurrence of atrophy and may have maximum anti-carcinogenic action.

Chronic restraint stress promotes gastric epithelial malignant transformation by activating the Akt/p53 signaling pathway via ADRB2

The etiology of gastric cancer is associated with infectious, environmental and dietary factors, as well as genetic background. Additionally, emerging evidence has supported the vital role of chronic emotional stress on gastric carcinogenesis; however, the underlying mechanism remains unclear. The present study aimed to investigate the effects of chronic stress and a detrimental diet on gastric malignant epithelial transformation in rats. Therefore, 26 Wistar rats were randomly divided into the following four groups: i) Control; ii) detrimental diet (DD); iii) detrimental diet with chronic restraint (DR) and iv) detrimental diet with chronic restraint and propranolol treatment (DRP). ELISA was performed to detect the serum levels of epinephrine and norepinephrine. Epithelial cell apoptosis was analyzed using the TUNEL assay. The mRNA and protein expression levels of Akt and p53 were detected using reverse transcription quantitative PCR and western blotting, respectively. Pathological changes were analyzed using hematoxylin and eosin staining (H&E). The H&E staining results showed that dysplasia in the gastric mucosa occurred in two of eight rats in the DD group and in four of five rats in the DR group, whereas no dysplasia was detected in the DRP group. The apoptotic ratios of gastric epithelial cells were significantly decreased in all treatment groups compared with the control group. Adrenoceptor β2 (ADRB2) protein expression levels were increased significantly only in the DR group and this effect was significantly reduced in the DRP group. The mRNA expression levels of Akt and p53 were significantly upregulated in the DD group, and Akt mRNA expression was further elevated in the DR group. With regard to protein expression, the levels of Akt and p-Akt were significantly increased in the DR group, whereas these effects were reversed in the DRP group. Furthermore, the ratio of p-p53/p53 protein was significantly reduced in the DD or DR groups, but was reversed in the DRP group. Collectively, the findings of the present study suggested that chronic restraint stress potentially aggravates the gastric epithelial malignant transformation induced by a detrimental diet, at least partially via the Akt/p53 signaling pathway mediated via ADRB2.

Proton Pump Inhibitor Use and Risk of Gastric Cancer: Current Evidence from Epidemiological Studies and Critical Appraisal

Proton pump inhibitors (PPIs) are used for maintaining or improving gastric problems. Evidence from observational studies indicates that PPI therapy is associated with an increased risk of gastric cancer. However, the evidence for PPIs increasing the risk of gastric cancer is still being debated. Therefore, we aimed to investigate whether long-term PPI use is associated with an increased risk of gastric cancer. We systematically searched the relevant literature in electronic databases, including PubMed, EMBASE, Scopus, and Web of Science. The search and collection of eligible studies was between 1 January 2000 and 1 July 2021. Two independent authors were responsible for the study selection process, and they considered only observational studies that compared the risk of gastric cancer with PPI treatment. We extracted relevant information from selected studies, and assessed the quality using the Newcastle−Ottawa scale (NOS). Finally, we calculated overall risk ratios (RRs) with 95% confidence intervals (CIs) of gastric cancer in the group receiving PPI therapy and the control group. Thirteen observational studies, comprising 10,557 gastric cancer participants, were included. Compared with patients who did not take PPIs, the pooled RR for developing gastric cancer in patients receiving PPIs was 1.80 (95% CI, 1.46−2.22, p < 0.001). The overall risk of gastric cancer also increased in patients with gastroesophageal reflux disease (GERD), H. pylori treatment, and various adjusted factors. The findings were also consistent across several sensitivity analyses. PPI use is associated with an increased risk of gastric cancer in patients compared with those with no PPI treatment. The findings of this updated study could be used in making clinical decisions between physicians and patients about the initiation and continuation of PPI therapy, especially in patients at high risk of gastric cancer. Additionally, large randomized controlled trials are needed to determine whether PPIs are associated with a higher risk of gastric cancer.

Gastrin: From Physiology to Gastrointestinal Malignancies

Abetted by widespread usage of acid-suppressing proton pump inhibitors (PPIs), the mitogenic actions of the peptide hormone gastrin are being revisited as a recurring theme in various gastrointestinal (GI) malignancies. While pathological gastrin levels are intricately linked to hyperplasia of enterochromaffin-like cells leading to carcinoid development, the signaling effects exerted by gastrin on distinct cell types of the gastric mucosa are more nuanced. Indeed, mounting evidence suggests dichotomous roles for gastrin in both promoting and suppressing tumorigenesis. Here, we review the major upstream mediators of gastrin gene regulation, including inflammation secondary to Helicobacter pylori infection and the use of PPIs. We further explore the molecular biology of gastrin in GI malignancies, with particular emphasis on the regulation of gastrin in neuroendocrine neoplasms. Finally, we highlight tissue-specific transcriptional targets as an avenue for targetable therapeutics.

Exposure to proton pump inhibitors and risk of pancreatic cancer: a meta-analysis

Objectives: To estimate the pancreatic cancer risk among subjects exposed versus not exposed to proton pump inhibitors.Methods: The authors searched PubMed, EMBASE, Scopus, Cochrane Library, and clinicaltrials.gov to identify relevant studies. The authors quantified pancreatic cancer risk among subjects exposed versus not exposed to PPIs, expressed as the pooled (adjusted) odds ratio (OR/aOR) and 95% confidence interval (95%CI) in overall and sensitivity analyses.Results: One randomized trial, two cohort, four case-control, and five nested case-control studies with 700,178 subjects (73,985 cases; 626,193 controls) were retained. PPI exposure was associated with pancreatic cancer risk (OR = 1.75, 95%CI = 1.12-2.72, I2 = 99%); confirmed in sensitivity analyses for high-quality studies, observational studies, case-control studies, studies with pancreatic cancer as the primary outcome, and in sensitivity analyses for diabetes and obesity but not for pancreatitis and smoking. This association was independent of the duration and Defined Daily Dose of PPI exposure. Rabeprazole had a singular significant association with pancreatic cancer (OR = 5.40, 95%CI = 1.98-14.703, I2 = 87.9%).Conclusion: The class of PPIs is associated with a 1.75-fold increase in pancreatic cancer risk, confirmed in sensitivity analyses.

Gastrin, Cholecystokinin, Signaling, and Biological Activities in Cellular Processes

The structurally-related peptides, gastrin and cholecystokinin (CCK), were originally discovered as humoral stimulants of gastric acid secretion and pancreatic enzyme release, respectively. With the aid of methodological advances in biochemistry, immunochemistry, and molecular biology in the past several decades, our concept of gastrin and CCK as simple gastrointestinal hormones has changed considerably. Extensive in vitro and in vivo studies have shown that gastrin and CCK play important roles in several cellular processes including maintenance of gastric mucosa and pancreatic islet integrity, neurogenesis, and neoplastic transformation. Indeed, gastrin and CCK, as well as their receptors, are expressed in a variety of tumor cell lines, animal models, and human samples, and might contribute to certain carcinogenesis. In this review, we will briefly introduce the gastrin and CCK system and highlight the effects of gastrin and CCK in the regulation of cell proliferation and apoptosis in both normal and abnormal conditions. The potential imaging and therapeutic use of these peptides and their derivatives are also summarized.

Proton pump inhibitors on pancreatic cancer risk and survival

BACKGROUND

Hypergastrinemia may promote the development and progression of pancreatic cancer. Proton pump inhibitor (PPI) therapy is known to cause hypergastrinemia. We sought to determine the association between PPI therapy and the risk of developing pancreatic cancer as well as survival following pancreatic cancer diagnosis.

METHODS

We conducted a nested case-control study and a retrospective cohort study in The Health Improvement Network (THIN), a medical records database representative of the UK population. In the case-control study, each patient with incident pancreatic cancer was matched with up to four controls based on age, sex, practice site and both duration and calendar time of follow-up using incidence density sampling. The odds ratios (ORs) and 95% confidence intervals (CIs) for pancreatic cancer risk associated with PPI use were estimated using multivariable conditional logistic regression. The retrospective cohort study compared the survival of pancreatic cancer patients according to their PPI exposure at the time of diagnosis. The effect of PPI use on pancreatic cancer survival was assessed using a multivariable Cox regression analysis.

RESULTS

The case-control study included 4113 cases and 16,072 matched controls. PPI use was more prevalent in cases than controls (53% vs. 26% active users). Adjusting for diabetes, smoking, alcohol use and BMI, PPI users including both former users and active users with longer cumulative PPI use had a higher risk of pancreatic cancer compared to non-users. When assessing survival following pancreatic cancer diagnosis, only short-term, active users had a modest decrease in survival.

CONCLUSIONS

Long-term PPI therapy may be associated with pancreatic cancer risk. While PPI users recently started on treatment had a slightly worse survival, this result likely is from reverse causation.

PAI-1 deficiency increases the trophic effects of hypergastrinemia in the gastric corpus mucosa

The gastric hormone gastrin plays a role in organizing the gastric mucosa. Gastrin also regulates the expression of genes that have important actions in extracellular matrix modelling, including plasminogen activator inhibitor (PAI)-1 which is part of the urokinase plasminogen activator (uPA) system. The uPA system (including PAI-1) is associated with cancer progression, fibrosis and thrombosis. Its biological role in the stomach and molecular mechanisms of action are not well understood. The aim of this study was to examine the effect of PAI-1 on the trophic changes observed in gastric corpus mucosa in hypergastrinemia using PAI-1 and/or HK-ATPase beta subunit knockout (KO) mice. HK-ATPase beta subunit KO mice were used as a model of hypergastrinemia. In 12 month old female mice, intragastric acidity and plasma gastrin were measured. The stomachs were examined for macroscopic and histological changes. In mice null for both PAI-1 and HK-ATPase beta (double KO), there was exaggerated hypergastrinemia, increased stomach weight and corpus mucosal thickness, and more pronounced trophic and architectural changes in the corpus compared with HK-ATPase beta KO mice. Genome-wide microarray expression data for the gastric corpus mucosa showed a distinct gene expression profile for the HK-ATPase beta KO mice; moreover, enrichment analysis revealed changes in expression of genes regulating intracellular processes including cytoskeleton remodelling, cell adhesion, signal transduction and epithelial-to-mesenchymal transition (EMT). Genes differentially expressed in the double KO compared with HK-ATPase beta KO mice included the transcription factor Barx2 and the chromatin remodeler gene Tet2, which may be involved in both normal gastric physiology and development of gastric cancer. Based on the present data, we suggest that PAI-1 plays a role in maintaining gastric mucosal organization in hypergastrinemia.

Risk of gastric cancer, gastrointestinal cancers and other cancers: a comparison of treatment with pantoprazole and other proton pump inhibitors

BACKGROUND

Proton pump inhibitors (PPIs) have been shown to be carcinogenic in rodent studies.

AIM

As part of a long-term post-marketing surveillance study requested by the US Food and Drug Administration, to compare incidence rates of gastric and other cancers after sustained exposures to pantoprazole, a long-acting PPI, compared with other shorter acting PPIs.

METHODS

We conducted a cohort study within the membership of the Kaiser Permanente Northern California healthcare system and compared rates of gastric and other cancers among pantoprazole users and users of other PPI medications. The Cox proportional hazards model was used to adjust for potential confounders such as sex, age, receipt of treatment for Helicobacter pylori, cumulative PPI dose, total years PPI treatment and year of index date. The study was developed in consultation with, and approved by, the FDA.

RESULTS

A total of 61 684 persons with at least a 240-day supply of medication (34 178 pantoprazole and 27 686 other PPIs) were followed up for a total of 547 020 person-years (274 700 vs. 272 321 person-years, respectively). The primary analyses demonstrated comparable risks between the pantoprazole and other PPI groups for gastric cancer [hazard ratio (HR) = 0.68, 95% CI 0.24-1.93); colorectal, liver, pancreatic, or small bowel cancers (HR = 0.95, 95% CI 0.65-1.40) or any cancer (HR = 1.06, 95% CI 0.93-1.21).

CONCLUSIONS

We found no evidence that pantoprazole, a longer acting PPI, compared with shorter-acting agents, conferred an excess risk of gastric cancer, other gastrointestinal cancers or all cancers for pantoprazole compared with other shorter-acting PPIs.

A clinical perspective on gastric neuroendocrine neoplasia

The incidence of gastric neuroendocrine tumors (NETs) has increased exponentially based on widespread use of endoscopy and a greater pathological awareness of the condition. A key concern is the potential association with hypergastrinemia induced by proton pump inhibitor administration. Previous confusion regarding diagnosis and therapy has been diminished by a series of international consensus statements defining the biology and management strategies for the disease. Overall, gastric NETs are categorized as well-differentiated or poorly differentiated neoplasms. Well-differentiated gastric NETs are enterochromaffin-like (ECL) cell tumors subclassified into three types based on their relationship to gastrin, a key regulator of ECL cell neoplastic transformation. The treatment of type 1 and type 2 tumors depends on the size and invasiveness of the tumor, whereas type 3 tumors and poorly differentiated neuroendocrine carcinomas warrant aggressive surgical resection. The disease-specific 5-year survival ranges from about 95% in type 1 gastric carcinoids to about 25% in poorly differentiated gastric NECs. Elucidation of the precise biology of a gastric NET is critical to diagnosis and delineation of a type-specific management strategy.

The CCK(2) receptor antagonist, YF476, inhibits Mastomys ECL cell hyperplasia and gastric carcinoid tumor development

YF476 is a potent and highly selective cholecystokin 2 (CCK(2)) receptor antagonist of the benzodiazepine class. It inhibits gastric neuroendocrine enterochromaffin-like (ECL) cell secretion, proliferation and spontaneous formation of gastric neuroendocrine tumors (carcinoids) in cotton rats. The Mastomys rodent species exhibits a genetic predisposition to gastric ECL neuroendocrine tumor formation which can be accelerated by acid suppression and induction of hypergastrinemia. In this respect, it mimics the human condition of atrophic gastritis, hypergastrinemia and gastric carcinoid development. We investigated whether YF476 could inhibit acid suppression-induced ECL cell hyperplasia and neoplasia in this model. In addition, we examined whether YF476 could reverse established ECL cell hyperplasia and neoplasia. Targeting the CCK(2) receptor during Loxtidine-induced hypergastrinemia resulted in a reduction in ECL cell secretion (plasma and mucosal histamine, and histidine decarboxylase (HDC) transcripts, p<0.05) and proliferation (numbers of HDC-positive cells, connective tissue growth factor (CTGF) and cyclin D1 transcription). This was associated with a decrease in ECL cell hyperplasia and a 60% reduction in gastric ECL cell microcarcinoid (tumors <0.3mm in size) formation. YF476 inhibited ECL cell neoplasia (gastric carcinoid) in animals with hyperplasia, inhibited the formation of ECL cell tumors when co-administered with Loxtidine and reversed the growth and developement of gastric ECL cell carcinoids in long-term acid suppressed Mastomys. Variable importance analysis using a logistic multinomial regression model indicated the effects of YF476 were specific to the ECL cell and alterations in ECL cell function reflected inhibition of transcripts for HDC, Chromogranin A (CgA), CCK(2) and the autocrine growth factor, CTGF. We conclude that specifically targeting the CCK(2) receptor inhibits gastrin-mediated ECL cell secretion and ECL cell proliferation and tumor development in vivo.

Importance of gastrin in the pathogenesis and treatment of gastric tumors

In addition to regulating acid secretion, the gastric antral hormone gastrin regulates several important cellular processes in the gastric epithelium including proliferation, apoptosis, migration, invasion, tissue remodelling and angiogenesis. Elevated serum concentrations of this hormone are caused by many conditions, particularly hypochlorhydria (as a result of autoimmune or Helicobacter pylori (H pylori)-induced chronic atrophic gastritis or acid suppressing drugs) and gastrin producing tumors (gastrinomas). There is now accumulating evidence that altered local and plasma concentrations of gastrin may play a role during the development of various gastric tumors. In the absence of H pylori infection, marked hypergastrinemia frequently results in the development of gastric enterochromaffin cell-like neuroendocrine tumors and surgery to remove the cause of hypergastrinemia may lead to tumor resolution in this condition. In animal models such as transgenic INS-GAS mice, hypergastrinemia has also been shown to act as a cofactor with Helicobacter infection during gastric adenocarcinoma development. However, it is currently unclear as to what extent gastrin also modulates human gastric adenocarcinoma development. Therapeutic approaches targeting hypergastrinemia, such as immunization with G17DT, have been evaluated for the treatment of gastric adenocarcinoma, with some promising results. Although the mild hypergastrinemia associated with proton pump inhibitor drug use has been shown to cause ECL-cell hyperplasia and to increase H pylori-induced gastric atrophy, there is currently no convincing evidence that this class of agents contributes towards the development of gastric neuroendocrine tumors or gastric adenocarcinomas in human subjects.

Gastrin increases mcl-1 expression in type I gastric carcinoid tumors and a gastric epithelial cell line that expresses the CCK-2 receptor

Elevated serum concentrations of the hormone gastrin are associated with the development of gastric carcinoid tumors, but the mechanisms of tumor development are not fully understood. We hypothesized that the antiapoptotic effects of gastrin may be implicated and have therefore investigated the role of antiapoptotic members of the bcl-2 family of proteins. AGS-G(R) human gastric carcinoma cells stably transfected with the CCK-2 receptor were used to assess changes in the expression of bcl-2 family members following gastrin treatment and the function of mcl-1 during apoptosis was investigated by use of small-interfering RNA (siRNA). Treatment of AGS-G(R) cells with 10 nM gastrin for 6 h caused maximally increased mcl-1 protein abundance. Gastrin-induced mcl-1 expression was inhibited by the transcription inhibitor actinomycin D and by the protein synthesis inhibitor cycloheximide. Downstream signaling of mcl-1 expression occurred via the CCK-2 receptor, protein kinase C, and MAP kinase pathways, but not via PI 3-kinase. Transfection with mcl-1 siRNA significantly suppressed mcl-1 protein expression and abolished the antiapoptotic effects of gastrin on serum starvation-induced apoptosis. Mcl-1 protein expression was also specifically increased in the type I enterochromaffin-like cell carcinoid tumors of 10 patients with autoimmune atrophic gastritis and hypergastrinemia. Gastrin therefore signals via the CCK-2 receptor, protein kinase C, and MAP kinase to induce expression of antiapoptotic mcl-1 in AGS-G(R) cells, and mcl-1 expression is also increased in human hypergastrinemia-associated type I gastric carcinoid tumors. Gastrin-induced mcl-1 expression may therefore be an important mechanism contributing toward type I gastric carcinoid development.

Changes in gene expression of gastric mucosa during therapeutic acid inhibition

BACKGROUND

Long-term therapy with potent acid inhibitors is a common treatment for gastro-esophageal reflux disease. Administration of proton pump inhibitors (PPIs) causes profound and continuous hypochlorhydria by inhibition of the proton pump in gastric parietal cells. Long-term hypergastrinaemia increases mucosal thickness and enterochromaffin-like cell density in oxyntic mucosa.

OBJECTIVE

The aim of this study was to see whether this very common clinical intervention induces significant changes in the gastric mucosal gene expression pattern.

METHODS

Seven patients suffering from gastro-esophageal reflux disease were included in this study. Endoscopic biopsies were taken from the corpus mucosa before and toward the end of a 3-month treatment with the PPI esomeprazole.

RESULTS

Microarray analysis identified 186 differentially expressed genes. A high proportion of genes with changed gene expression levels during PPI treatment are involved in proliferation, apoptosis, and stress response.

CONCLUSION

This study identified many genes that were not previously known to be affected by inhibition of gastric acid secretion. Further characterization of the functional roles of genes whose expression is modulated by potent acid inhibition may give new insight into the biological responses to potent acid inhibition, including the mucosal response to the moderately increased gastrin levels encountered in clinical practice.

[Study on histogenesis of enterochromaffin-like carcinoid in autoimmune atrophic gastritis associated with pernicious anemia]

BACKGROUND/AIM

Autoimmune atrophic fundic gastritis induces the pernicious anemia (PA), as well as the changes in both epithelium and endocrine cells of gastric mucosa. The most important complications are: achlorhydria, hypergastrinemia, gastric cancer and enterochromaffin-like (ECL) carcinoid. The aim of this study was to examine ECL carcinoid histogenesis in A-gastritis associated with PA.

METHODS

During the period from 2000-2006, 65 patients with PA and 30 patients of the control group were examined. Histopathological examination was done in endoscopical biopsies of gastric mucosa fixed in 10% formaldehyde. Paraffin sections were stained with classic hematoxylin-eosin (HE); histochemical AB-PAS (pH 2.5), cytochemical argyrophilic Servier-Munger's and immunocytochemical PAP methods for G cell identification and chromogranin A antibodies - specific marker for neuroendocrine ECL cells. Both G and ECL cells were counted per 20 fields, of surface 0.0245312 mm2 by a field. Basal gastrin serum levels were also examined by using radioimmunoassay (RIA) method. The obtained results were statisticaly calculated by using Student's t test.

RESULTS

Marked antral G cell hyperplasia associated with corporal ECL hyperplasia was found. ECL cell hyperplasia was of simplex, linear, adenomatoid type to the pattern of intramucous ECL cell carcinoid. An average number of G cells was statistically significant in the patients with PA as compared to the control group (p < 0.05) as well as an average number of ECL cells.

CONCLUSION

We concluded that antral G cell hyperplasia accompanied by gastrinemia induces ECL hyperplasia and ECL corporal carcinoid in A-gastritis and that their histogenesis develops trough simple, linear and adenomatoide hyperplasia.

Hypergastrinemia increases gastric epithelial susceptibility to apoptosis

Plasma concentrations of the hormone gastrin are elevated by Helicobacter pylori infection and by gastric atrophy. It has previously been proposed that gastrin acts as a cofactor during gastric carcinogenesis and hypergastrinemic transgenic INS-GAS mice are prone to developing gastric adenocarcinoma, particularly following H. pylori infection. We hypothesised that the increased risk of carcinogenesis in these animals may partly result from altered susceptibility of gastric epithelial cells to undergo apoptosis. Gastric corpus apoptosis was significantly increased 48 h after 12Gy gamma-radiation in mice rendered hypergastrinemic by transgenic (INS-GAS) or pharmacological (omeprazole treatment of FVB/N mice) methods and in both cases the effects were inhibited by the CCK-2 receptor antagonist YM022. However, no alteration in susceptibility to gamma-radiation-induced gastric epithelial apoptosis was observed in mice overexpressing progastrin or glycine-extended gastrin. Apoptosis was also significantly increased in gastric corpus biopsies obtained from H. pylori-infected humans with moderate degrees of hypergastrinemia. We conclude that hypergastrinemia specifically renders cells within the gastric corpus epithelium more susceptible to induction of apoptosis by radiation or H. pylori. Altered susceptibility to apoptosis may therefore be one factor predisposing to gastric carcinogenesis in INS-GAS mice and similar mechanisms may also be involved in humans.

Expression of gastrin receptor in tumors and its application as a molecular target for cancer diagnosis and therapy

Gastrin is widely distributed in gastrointestinal tract and pancreatic tissues, and it plays important roles in the modulation of physiological functions and pathogenic mechanism of some diseases. Recent studies showed that gastrin might promote the pathogenesis and growth of tumors, especially digestive tumors such as gastric cancer and colorectal cancer. The biological effect of gastrin is mainly mediated by cholecystokinin (CCK) receptors. Gastrin mRNA has been found in CCK-receptor positive small-cell lung carcinoma, breast cancer, ovarian cancer and cancer stem cells of various origins and it may serve as the indicator of self-secretive regulation. The tumors with over-expressed gastin receptor can be diagnosed and treated by radiolabelling or linking to the cytotoxic agents with gastin peptide and analogs, and scintigraphy was used to visualize the image in vivo.

Gastrin-induced apoptosis contributes to carcinogenesis in the stomach

Hypergastrinemia in INS-GAS mice leads to accelerated carcinogenesis of the stomach, but the mechanisms have not been well defined. We investigated the possible role of gastrin-induced gastric cell apoptosis in the development of gastric cancer. We examined apoptosis and the expression of Bcl-2 family proteins in INS-GAS mice of different ages, as well as in gastrin-deficient (GAS-KO) mice after gastrin-17 (G-17) infusion. In addition, we studied the effects of the gastrin/cholecystokinin-2 (CCK-2) receptor antagonist YF476 and/or histamine H2 (H-2) receptor antagonist loxtidine on apoptosis and atrophy in INS-GAS mice with or without Helicobacter felis (H. felis) infection. INS-GAS mice had age-associated increases in Bax protein expression and decreases in Bcl-2 protein expression, along with increased glandular and epithelial cell apoptosis. At 8-week gastrin infusions in GAS-KO mice resulted in a similar pattern of altered Bax and Bcl-2 expression, followed by gastric cell apoptosis. H. felis infection of INS-GAS mice led to increased apoptosis and the development of atrophy, whereas treatment with either YF476 and/or loxtidine strongly inhibited both apoptosis and atrophy. In vitro studies with Fas-expressing RGM1 cells showed that gastrin stimulation alone directly induced apoptosis via gastrin/CCK-2 receptor and synergized with FasL stimulation. These results indicate that gastrin can induce apoptosis in gastric epithelial cells and contribute to the development of gastric carcinogenesis.

Relationship between expression of gastrin, somatostatin mRNA and cell apoptosis and Bcl-2, Bax in large intestinal carcinoma

AIM: To explore the correlations the between expression of somatostatin (SS), gastrin (GAS) mRNA and cell apoptosis index (AI) and Bcl-2, Bax in large intestinal cancer.

METHODS: The expression of GAS and SS genes were detected in 62 colorectal cancer patients by nested reverse transcription polymerase chain reaction (RT-PCR), and the apoptosis of the cells was detected by TUNEL method. The protein expression of,Bcl-2, Bax, GAS, and SS were detected using immunohistochemical staining (S-P method).

RESULTS: The expression of GAS and SS mRNA and protein were basically consistent. The AI in SS high and moderate expression patients with large intestinal cancer was remarkably higher than that in SS low expression ones (q = 5.06, 3.95, both P < 0.01), while it was just opposite in GAS positive patients (q = 6.66, 6.33, P < 0.01). The positive rates of Bax and Bcl-2 expression had significant difference between SS (or GAS) high, moderate and low expression patients with large intestinal cancer (Bax: χ² = 9.24, 6.91, P < 0.05; Bcl-2: χ² = 7.17, 13.83, P < 0.05). The positive rate of Bax expression in SS high (80%, 8/10) and moderate (76.5%, 13/17) expression patients was notably higher than that in the low expression ones (40.0%, 14/35) (χ² = 5.24, 6.09, P < 0.05), but the rate of Bcl-2 expression was just opposite (χ² = 4.71, 4.70, P < 0.05). The positive rate of Bcl-2 expression in GAS high (90.9%,10/11) and moderate expression patients (86.7%,13/15) was markedly higher than that in the low expression ones (44.4%, 16/36) (χ² = 5.60, 7.69, P < 0.05), but the positive rate of Bax expression in GAS high expression patients (27.3%, 3/8) was obviously lower than that in the low expression ones (69.4%, 25/36) (χ² = 4.59, P < 0.05). Bax expression was not significantly different between moderate and low GAS positive patients. The value of GAS/SS was positively correlated with Bcl-2 expression (r = 0.34, P < 0.01), but negatively with the AI value and Bax expression (r = －0.546, P < 0.01; r = －0.299, P < 0.05).

CONCLUSION: GAS and SS play important roles in the regulation and control of cell apoptosis in large intestinal carcinoma, and the mechanism may be related to the aberrant expression of Bcl-2 and Bax.

Synergistic inhibitory effects of gastrin and histamine receptor antagonists on Helicobacter-induced gastric cancer

BACKGROUND & AIMS

Apart from its importance as an acid secretogogue, the role of histamine as a downstream target of gastrin has not been fully explored. Previous studies have shown that the combination of hypergastrinemia and Helicobacter infection resulted in accelerated gastric cancer in mice. We used this model to examine the role of cholecystokinin 2 (CCK2)/gastrin receptor and histamine H2-receptor signaling in the development of gastric atrophy and cancer.

METHODS

Male hypergastrinemic mice (INS-GAS mice) were infected with Helicobacter felis and given the CCK2/gastrin receptor antagonist YF476 and/or the histamine H2-receptor antagonist loxtidine for 3 or 6 months. In addition, mice were treated with omeprazole alone or in combination with either YF476 or loxtidine for 3 months.

RESULTS

Mice treated with YF476 or loxtidine alone showed partial suppression of both gastric acid secretion and progression to neoplasia. The combination of YF476 plus loxtidine treatment resulted in nearly complete inhibition of both parameters. YF476 and/or loxtidine treatment did not alter the overall level of H. felis colonization but did result in significant down-regulation of the growth factors regenerating gene I and amphiregulin. Loxtidine treatment, with or without YF476, induced a mild shift in T-helper cell polarization. In contrast, omeprazole treatment resulted in mild progression of gastric hyperplasia/dysplasia, which was ameliorated by the addition of YF476 or loxtidine.

CONCLUSIONS

The combination of CCK2/gastrin- and histamine H2-receptor antagonists has synergistic inhibitory effects on development of gastric atrophy and cancer in H. felis/INS-GAS mice, while the proton pump inhibitor showed no such effects. These results support an important role for the gastrin-histamine axis in Helicobacter-induced gastric carcinogenesis.

Overexpression of glycine-extended gastrin inhibits parietal cell loss and atrophy in the mouse stomach

Recently we have reported synergistic effects between glycine-extended gastrin (G-gly) and amidated gastrin-17 on acid secretion in short-term infusion studies. In the present study, we examined the long-term effect of G-gly on the atrophy-promoting effects of amidated gastrin in the mouse stomach with or without Helicobacter infection. Transgenic mice overexpressing amidated gastrin (INS-GAS mice), G-gly (MTI/G-gly mice), and both peptides (INS-GAS/G-gly mice) were used for assessment of acid secretion and ulcer susceptibility and histologic examination and scoring of preneoplastic lesions in response to the 3 and 6 months Helicobacter felis (H. felis) infection. We found that MTI/G-gly mice had normal gastric histology and acid secretion. Double transgenic (INS-GAS/G-gly) mice showed 2-fold increases in acid secretion compared with INS-GAS mice. Acute peptic ulcers after pyloric ligation were noted in 50% of the INS-GAS/G-gly mice but in none of the INS-GAS mice at 6 months of age. Whereas male INS-GAS mice had a >50% decrease in the numbers of parietal cell and enterochromaffin-like cell at 6 months of age, the male double transgenic mice had no such decrease. Overexpression of G-gly reduced the scores of preneoplasia in the stomach; however, it did not prevent the development of amidated gastrin-dependent gastric cancer in both H. felis-infected mice and uninfected mice. We conclude that G-gly synergizes with amidated gastrin to stimulate acid secretion and inhibits parietal cell loss in INS-GAS/G-gly mice. The overexpression of G-gly seems to increase the susceptibility to peptic ulcer disease and delay the development of Helicobacter-mediated gastric preneoplasia in this model.

A novel enterohepatic Helicobacter species 'Helicobacter mastomyrinus' isolated from the liver and intestine of rodents

BACKGROUND

A number of novel Helicobacter species have been isolated from both animals and humans. Many of these helicobacters colonize the lower gastrointestinal tract and hepatobiliary tract and are associated with diseases.

METHODS

A spiral-shaped bacterium, with bipolar single-sheathed flagella, was isolated from the liver and cecum of mastomys (the African rodent, Mastomys natalenis), from the feces and ceca of normal mice, and also from the cecum of a mouse with proctitis. 16S ribosomal RNA gene sequence analysis, restriction fragment length polymorphism (RFLP) and fluorophore-enhanced repetitive element polymerase chain reaction (FERP or rep-PCR) analysis were used to classify the organism.

RESULTS

The bacterium grew at 37 and 42 degrees C under microaerobic conditions, rapidly hydrolyzed urea, and was catalase and oxidase positive. It did not reduce nitrate to nitrite, and was resistant to cephalothin and nalidixic acid. Like many other enterohepatic Helicobacter species, this organism expressed cytolethal distending toxin and causes cell distention.

CONCLUSIONS

The organism was classified as a novel Helicobacter species for which we propose the name 'Helicobacter mastomyrinus'. Although 'H. mastomyrinus', like Helicobacter hepaticus and Helicobacter bilis, colonizes the liver of rodents, the pathogenic potential of this novel helicobacter is unknown.

Alterations in gastric mucosal lineages induced by acute oxyntic atrophy in wild-type and gastrin-deficient mice

In addition to their role in gastric acid secretion, parietal cells secrete a number of growth factors that may influence the differentiation of other gastric lineages. Indeed, oxyntic atrophy is considered the most significant correlate with increased risk for gastric adenocarcinoma. We studied the alterations in gastric mucosal lineages elicited by acute oxyntic atrophy induced by treatment of C57BL/6 and gastrin-deficient mice with the parietal cell protonophore [S-(R*,S*)]-N-[1-(1,3-benzodioxol-5-yl)butyl]-3,3-diethyl-2-[4-[(4-methyl-1-piperazinyl)carbonyl]phenoxy]-4-oxo-1-azetidinecarboxamide (DMP-777). In both wild-type and gastrin knockout mice, DMP-777 elicited the rapid loss of parietal cells within 2 days of treatment. In wild-type mice, oxyntic atrophy was accompanied by a rapid increase in 5-bromo-2'-deoxyuridine-labeled proliferative cells and attendant increase in surface cell numbers. However, gastrin knockout mice did not demonstrate significant foveolar hyperplasia and showed a blunted proliferative response. After 7 days of treatment in wild-type mice, a second proliferative population emerged at the base of fundic glands along with the development of a mucous cell metaplasia expressing TFF2/spasmolytic polypeptide (SPEM). However, in gastrin knockout mice, SPEM expressing both TFF2 mRNA and protein developed after only 1 day of DMP-777 treatment. In wild-type mice, all changes induced by DMP-777 were reversed 14 days after cessation of treatment. In gastrin-deficient mice, significant SPEM was still present 14 days after the cessation of treatment. The results indicate that foveolar hyperplasia requires the influence of gastrin, whereas SPEM develops in response to oxyntic atrophy independent of gastrin, likely through transdifferentiation of chief cells.

Global expression analysis of ECL cells in Mastomys natalensis gastric mucosa identifies alterations in the AP-1 pathway induced by gastrin-mediated transformation

Enterochromaffin-like (ECL) cell hyperplasia and then irreversible neoplasia can be generated in the African rodent Mastomys natalensis using the H2 receptor blocker, loxtidine, for 8–16 wk. We used a GeneChip approach complemented by standard technologies to identify gene expression alterations in the gastric mucosa during gastrin-mediated ECL cell transformation. Gastric mucosa (mucosal scrapping) and ECL cell-enriched fractions were obtained from untreated Mastomys (controls) and from animals treated with loxtidine for 8 wk (hyperplasia). Tumor ECL cells were obtained by hand-dissection of gastric ECL cell nodules from animals treated with loxtidine for >16 wk and from a spontaneously developed ECL cell tumor. RNA was isolated, examined on rat U34A GeneChips, and comparison analysis was performed to identify altered gene expression. Alterations in gene expressions were examined further by immunohistochemistry, quantitative RT-PCR (Q-RT-PCR), sequencing and Western blot. GeneSpring analysis demonstrated alterations in few genes (<20) in hyperplastic and tumor mucosa. The histamine H1 receptor was consistently increased in proliferating mucosa. This gene change was confirmed by Q-RT-PCR. Other genes showing alterations included neural-(chromogranin A and somatostatin), cell-cycle-, and AP-1-associated genes. Immunostaining confirmed alterations in neural markers. Cluster analysis of ECL cell-enriched samples demonstrated that c- fos and junD were differently regulated. Q-RT-PCR and Western blot in prospectively collected gastric mucosal samples confirmed the differential expression of Fos and Jun. The negative regulators of AP-1, JunD, and Menin were decreased in tumor mucosa. A missense of unknown function was noted in the menin gene. Hypergastrinemia in an animal model of gastric carcinoids differentially altered the histamine type 1 receptor and gene expression and protein composition of AP-1. These results suggest that expression of this receptor and an altered composition of AP-1 with a loss of inhibition play a role in ECL cell transformation.

ECL-Cell Derived Gastric Cancer in Male Cotton Rats Dosed with the H2-Blocker Loxtidine

Spontaneously hypergastrinemic cotton rats (Sigmodon hispidus) develop tumors that have the phenotype of an adenocarcinoma but most likely originate from the enterochromaffin-like (ECL) cells. Among inbred animals approximately 50% of the females, but <1% of males develop spontaneous gastric carcinomas. Gastrin is the principle carcinogen in this model, as >4 months of hypergastrinemia results in carcinoma, but a gastrin receptor antagonist prevents carcinomas. Carcinomas can also be induced by partial corpectomy. In the present study, the insurmountable H2-receptor antagonist loxtidine (200 mg/kg/day) was given to male cotton rats for 6 months. The loxtidine-dosed animals developed hypergastrinemia, whereas control animals remained normogastrinemic. At termination, 4 of 5 cotton rats had cancer located to the oxyntic mucosa, whereas 1 animal had dysplasia. The gastric mucosa of all of the control animals was normal. In the dysplastic mucosa of loxtidine-dosed animals there was a marked increase in chromogranin A-positive cells, where numerous groups of cells also stained positive with the Sevier-Munger technique. In areas of high proliferation and cancer there were also histidine decarboxylase, chromogranin A, and Sevier-Munger-positive cells, altogether indicating an ECL cell origin of the tumors. This represents an interesting animal model where ECL cell-derived gastric cancer can be induced by pharmacological acid inhibition in 6 months.