Gastrin induces heparin-binding epidermal growth factor-like growth factor in rat gastric epithelial cells transfected with gastrin receptor

Dynamic gene screening enabled identification of a 10-gene panel for early detection and progression assessment of gastric cancer

Early diagnosis and progression assessment are critical for the timely detection and treatment of gastric cancer (GC) patients. Identification of diagnostic biomarkers for early detection of GC represents an unmet clinical need, and how these markers further influence GC progression is explored rarely. We performed dynamic gene screening based on high-throughput data analysis from patients with precancerous lesions and early gastric cancer (EGC) and identified a 10-gene panel by the lasso regression model. This panel demonstrated good diagnostic performance in TCGA (AUC = 0.95, sensitivity = 86.67 %, specificity = 90.63 %) and GEO (AUC = 0.84, sensitivity = 91.67 %, specificity = 78.13 %) cohorts. Moreover, three GC subtypes were clustered based on this panel, in which cluster 2 (C2) demonstrated the highest tumor progression level with a high expression of 10 genes, showing a decreased tumor mutation burden, significantly enriched epithelial-mesenchymal transition hallmark and increased immune exclusion/exhausted features. Finally, the cell localization of these panel genes was explored in scRNA-seq data based on more than 40,000 cells. The 10-gene panel is expected to be a new clinical early detection signature for GC and may aid in progression assessment and personalized treatment of patients.

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.

Hypergastrinemia Expands Gastric ECL Cells Through CCK2R+ Progenitor Cells via ERK Activation

BACKGROUND & AIMS

Enterochromaffin-like (ECL) cells in the stomach express gastrin/cholecystokinin 2 receptor CCK2R and are known to expand under hypergastrinemia, but whether this results from expansion of existing ECL cells or increased production from progenitors has not been clarified.

METHODS

We used mice with green fluorescent protein fluorescent reporter expression in ECL cells (histidine decarboxylase [Hdc]-green fluorescent protein), as well as Cck2r- and Hdc-driven Tamoxifen inducible recombinase Cre (Cck2r-CreERT2, Hdc-CreERT2) mice combined with Rosa26Sor-tdTomato (R26-tdTomato) mice, and studied their expression and cell fate in the gastric corpus by using models of hypergastrinemia (gastrin infusion, omeprazole treatment).

RESULTS

Hdc-GFP marked the majority of ECL cells, located in the lower third of the gastric glands. Hypergastrinemia led to expansion of ECL cells that was not restricted to the gland base, and promoted cellular proliferation (Ki67) in the gastric isthmus but not in basal ECL cells. Cck2r-CreERT2 mice marked most ECL cells, as well as scattered cell types located higher up in the glands, whose number was increased during hypergastrinemia. Cck2r-CreERT2⁺ isthmus progenitors, but not Hdc⁺ mature ECL cells, were the source of ECL cell hyperplasia during hypergastrinemia and could grow as 3-dimensional spheroids in vitro. Moreover, gastrin treatment in vitro promoted sphere formation from sorted Cck2r⁺Hdc^- cells, and increased chromogranin A and phosphorylated- extracellular signal-regulated kinase expression in CCK2R-derived organoids. Gastrin activates extracellular signal-regulated kinase pathways in vivo and in vitro, and treatment with the Mitogen-activated protein kinase kinase 1 inhibitor U0126 blocked hypergastrinemia-mediated changes, including CCK2R-derived ECL cell hyperplasia in vivo as well as sphere formation and chromogranin A expression in vitro.

CONCLUSIONS

We show here that hypergastrinemia induces ECL cell hyperplasia that is derived primarily from CCK2R⁺ progenitors in the corpus. Gastrin-dependent function of CCK2R⁺ progenitors is regulated by the extracellular signal-regulated kinase pathway.

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.

Melatonin in Prevention of the Sequence from Reflux Esophagitis to Barrett's Esophagus and Esophageal Adenocarcinoma: Experimental and Clinical Perspectives

Melatonin is a tryptophan-derived molecule with pleiotropic activities which is produced in all living organisms. This "sleep" hormone is a free radical scavenger, which activates several anti-oxidative enzymes and mechanisms. Melatonin, a highly lipophilic hormone, can reach body target cells rapidly, acting as the circadian signal to alter numerous physiological functions in the body. This indoleamine can protect the organs against a variety of damaging agents via multiple signaling. This review focused on the role played by melatonin in the mechanism of esophagoprotection, starting with its short-term protection against acute reflux esophagitis and then investigating the long-term prevention of chronic inflammation that leads to gastroesophageal reflux disease (GERD) and Barrett's esophagus. Since both of these condition are also identified as major risk factors for esophageal carcinoma, we provide some experimental and clinical evidence that supplementation therapy with melatonin could be useful in esophageal injury by protecting various animal models and patients with GERD from erosions, Barrett's esophagus and neoplasia. The physiological aspects of the synthesis and release of this indoleamine in the gut, including its release into portal circulation and liver uptake is examined. The beneficial influence of melatonin in preventing esophageal injury from acid-pepsin and acid-pepsin-bile exposure in animals as well as the usefulness of melatonin and its precursor, L-tryptophan in prophylactic and supplementary therapy against esophageal disorders in humans, are also discussed.

Abomasal dysfunction and cellular and mucin changes during infection of sheep with larval or adult Teladorsagia circumcincta

This is the first integrated study of the effects on gastric secretion, inflammation and fundic mucins after infection with L3 T. circumcincta and in the very early period following transplantation of adult worms. At 3 months-of-age, 20 Coopworth lambs were infected intraruminally with 35,000 L3; infected animals were killed on Days 5, 10, 15, 20 and 30 post-infection and 6 controls on either Day 0 or 30 post-infection. Another 15 Romney cross lambs received 10,000 adult worms at 4-5 months-of-age though surgically-implanted abomasal cannulae and were killed after 6, 12, 24 and 72 hours; uninfected controls were also killed at 72 hours. Blood was collected at regular intervals from all animals for measurement of serum gastrin and pepsinogen and abomasal fluid for pH measurement from cannulated sheep. Tissues collected at necropsy were fixed in Bouin's fluid for light microscopy, immunocytochemistry and mucin staining and in Karnovsky's fluid for electron microscopy. Nodules around glands containing developing larvae were seen on Day 5 p.i., but generalised effects on secretion occurred only after parasite emergence and within hours after transplantation of adult worms. After L3 infection, there were maximum worm burdens on Days 10-15 post-infection, together with peak tissue eosinophilia, inhibition of gastric acid secretion, hypergastrinaemia, hyperpepsinogenaemia, loss of parietal cells, enlarged gastric pits containing less mucin and increased numbers of mucous neck cells. After adult transplantation, serum pepsinogen was significantly increased after 9 hours and serum gastrin after 18 hours. Parallel changes in host tissues and the numbers of parasites in the abomasal lumen suggest that luminal parasites, but not those in the tissues, are key drivers of the pathophysiology and inflammatory response in animals exposed to parasites for the first time. These results are consistent with initiation of the host response by parasite chemicals diffusing across the surface epithelium, possibly aided by components of ES products which increased permeability. Parietal cells appear to be a key target, resulting in secondary increases in serum gastrin, pit elongation, loss of surface mucins and inhibition of chief cell maturation. Inflammation occurs in parallel, and could either cause the pathology or exacerbate the direct effects of ES products.

Chromosomal breaks at FRA18C: association with reduced DOK6 expression, altered oncogenic signaling and increased gastric cancer survival

Chromosomal rearrangements are common in cancer. More than 50% occur in common fragile sites and disrupt tumor suppressors. However, such rearrangements are not known in gastric cancer. Here we report recurrent 18q2 breakpoints in 6 of 17 gastric cancer cell lines. The rearranged chromosome 18, t(9;18), in MKN7 cells was flow sorted and identified by reverse chromosome painting. High-resolution tiling array hybridization mapped breakpoints to DOK6 (docking protein 6) intron 4 in FRA18C (18q22.2) and an intergenic region in 9q22.2. The same rearrangement was detected by FISH in 22% of 99 primary gastric cancers. Intron 4 truncation was associated with reduced DOK6 transcription. Analysis of The Cancer Genome Atlas stomach adenocarcinoma cohort showed significant correlation of DOK6 expression with histological and molecular phenotypes. Multiple oncogenic signaling pathways (gastrin-CREB, NGF-neurotrophin, PDGF, EGFR, ERK, ERBB4, FGFR1, RAS, VEGFR2 and RAF/MAP kinase) known to be active in aggressive gastric cancers were strikingly diminished in gastric cancers with low DOK6 expression. Median survival of patients with low DOK6-expressing tumors was 2100 days compared with 533 days in patients with high DOK6-expressing tumors (log-rank P = 0.0027). The level of DOK6 expression in tumors predicted patient survival independent of TNM stage. These findings point to new functions of human DOK6 as an adaptor that interacts with diverse molecular components of signaling pathways. Our data suggest that DOK6 expression is an integrated biomarker of multiple oncogenic signals in gastric cancer and identify FRA18C as a new cancer-associated fragile site.

Gastrin and Gastric Cancer

Gastric cancer is the third leading cause of cancer-related mortality worldwide. Despite progress in understanding its development, challenges with treatment remain. Gastrin, a peptide hormone, is trophic for normal gastrointestinal epithelium. Gastrin also has been shown to play an important role in the stimulation of growth of several gastrointestinal cancers including gastric cancer. We sought to review the role of gastrin and its pathway in gastric cancer and its potential as a therapeutic target in the management of gastric cancer. In the normal adult stomach, gastrin is synthesized in the G cells of the antrum; however, gastrin expression also is found in many gastric adenocarcinomas of the stomach corpus. Gastrin's actions are mediated through the G-protein-coupled receptor cholecystokinin-B (CCK-B) on parietal and enterochromaffin cells of the gastric body. Gastrin blood levels are increased in subjects with type A atrophic gastritis and in those taking high doses of daily proton pump inhibitors for acid reflux disease. In experimental models, proton pump inhibitor-induced hypergastrinemia and infection with Helicobacter pylori increase the risk of gastric cancer. Understanding the gastrin:CCK-B signaling pathway has led to therapeutic strategies to treat gastric cancer by either targeting the CCK-B receptor with small-molecule antagonists or targeting the peptide with immune-based therapies. In this review, we discuss the role of gastrin in gastric adenocarcinoma, and strategies to block its effects to treat those with unresectable gastric cancer.

Pernicious anemia and colorectal cancer risk - A nested case-control study

BACKGROUND

Hypergastrinemia was shown to stimulate colonic epithelial cell proliferation.

AIMS

To evaluate the association between pernicious anemia (PA), a disease with hypergastrinemia, and colorectal cancer (CRC) risk.

METHODS

We conducted a nested case-control study within a large database from the UK. Cases were defined as all individuals in the cohort with at least one medical code for CRC. Controls were selected based on incidence-density sampling. For each case, up to four eligible controls were matched on age at diagnosis, sex, practice-site, and both duration and calendar time of follow-up. Exposure of interest was diagnosis of PA prior to CRC diagnosis date. The primary analysis was a multivariable conditional logistic regression.

RESULTS

Our study included 22,098 CRC cases and 85,969 matched controls. We identified 154 (0.70%) cases and 563 (0.65%) controls with past history of PA. The adjusted OR for the association between PA and CRC risk was 1.02 (95% CI 0.85-1.22). There was no difference in the results after stratification according to sex. In a sensitivity analysis only among individuals without chronic use of proton pump inhibitors (PPIs) the adjusted OR was 1.14 (95% CI 0.90-1.45). There was no association between duration of PA and CRC risk.

CONCLUSION

PA is not associated with higher CRC risk.

The Role of Gastrin and CCK Receptors in Pancreatic Cancer and other Malignancies

The gastrointestinal (GI) peptide gastrin is an important regulator of the release of gastric acid from the stomach parietal cells and it also plays an important role in growth of the gastrointestinal tract. It has become apparent that gastrin and its related peptide cholecystokinin (CCK) are also significantly involved with growth of GI cancers as well as other malignancies through activation of the cholecystokinin-B (CCK-B) receptor. Of interest, gastrin is expressed in the embryologic pancreas but not in the adult pancreas; however, gastrin becomes re-expressed in pancreatic cancer where it stimulates growth of this malignancy by an autocrine mechanism. Strategies to down-regulate gastrin or interfere with its interface with the CCK receptor with selective antibodies or receptor antagonists hold promise for the treatment of pancreatic cancer and other gastrin--responsive tumors.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

The gastrin and cholecystokinin receptors mediated signaling network: a scaffold for data analysis and new hypotheses on regulatory mechanisms

Background

The gastrointestinal peptide hormones cholecystokinin and gastrin exert their biological functions via cholecystokinin receptors CCK1R and CCK2R respectively. Gastrin, a central regulator of gastric acid secretion, is involved in growth and differentiation of gastric and colonic mucosa, and there is evidence that it is pro-carcinogenic. Cholecystokinin is implicated in digestion, appetite control and body weight regulation, and may play a role in several digestive disorders.

Results

We performed a detailed analysis of the literature reporting experimental evidence on signaling pathways triggered by CCK1R and CCK2R, in order to create a comprehensive map of gastrin and cholecystokinin-mediated intracellular signaling cascades. The resulting signaling map captures 413 reactions involving 530 molecular species, and incorporates the currently available knowledge into one integrated signaling network. The decomposition of the signaling map into sub-networks revealed 18 modules that represent higher-level structures of the signaling map. These modules allow a more compact mapping of intracellular signaling reactions to known cell behavioral outcomes such as proliferation, migration and apoptosis. The integration of large-scale protein-protein interaction data to this literature-based signaling map in combination with topological analyses allowed us to identify 70 proteins able to increase the compactness of the map. These proteins represent experimentally testable hypotheses for gaining new knowledge on gastrin- and cholecystokinin receptor signaling. The CCKR map is freely available both in a downloadable, machine-readable SBML-compatible format and as a web resource through PAYAO (http://sblab.celldesigner.org:18080/Payao11/bin/).

Conclusion

We have demonstrated how a literature-based CCKR signaling map together with its protein interaction extensions can be analyzed to generate new hypotheses on molecular mechanisms involved in gastrin- and cholecystokinin-mediated regulation of cellular processes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0181-z) contains supplementary material, which is available to authorized users.

The anti-diabetic effects of GLP-1-gastrin dual agonist ZP3022 in ZDF rats

AIMS/HYPOTHESIS

Combination treatment with exendin-4 and gastrin has proven beneficial in treatment of diabetes and preservation of beta cell mass in diabetic mice. Here, we examined the chronic effects of a GLP-1-gastrin dual agonist ZP3022 on glycemic control and beta cell dysfunction in overtly diabetic Zucker Diabetic Fatty (ZDF) rats.

METHODS

ZDF rats aged 11 weeks were dosed s.c., b.i.d. for 8 weeks with vehicle, ZP3022, liraglutide, exendin-4, or gastrin-17 with or without exendin-4. Glycemic control was assessed by measurements of HbA1c and blood glucose levels, as well as glucose tolerance during an oral glucose tolerance test (OGTT). Beta cell dynamics were examined by morphometric analyses of beta and alpha cell fractions.

RESULTS

ZP3022 improved glycemic control as measured by terminal HbA1c levels (6.2±0.12 (high dose) vs. 7.9±0.07% (vehicle), P<0.001), as did all treatments, except gastrin-17 monotherapy. In contrast, only ZP3022, exendin-4 and combination treatment with exendin-4 and gastrin-17 significantly improved glucose tolerance and increased insulin levels during an OGTT. Moreover, only ZP3022 significantly enhanced the beta cell fraction in ZDF rats, a difference of 41%, when compared to the vehicle group (0.31±0.03 vs. 0.22±0.02%, respectively, P<0.05).

CONCLUSION

These data suggest that ZP3022 may have therapeutic potential in the prevention/delay of beta cell dysfunction in type 2 diabetes.

The effect of disintegrin-metalloproteinase ADAM9 in gastric cancer progression

Advanced gastric cancer is one of the most aggressive gastrointestinal malignancies, and ADAM (A disintegrin and metalloproteinase)-9 is a cell-surface membrane glycoprotein with oncogenic properties that is overexpressed in several cancers. Herein, we investigated the biologic mechanism of ADAM9 in the progression, proliferation, and invasion of gastric cancer. First, we detected ADAM's expression, processing, and protease activity in gastric cancer cells. Protease activity was moderately correlated with ADAM9 protein expression, but was better related to a processed smaller molecular weight (84 kDa) form of ADAM9. Knockdown of ADAM9 or specifically targeted monoclonal antibody (RAV-18) suppressed cancer cell proliferation and invasion in high ADAM9-expressing cells, not in low ADAM9-expressing cells. RAV-18 showed in vivo antitumor activity in a gastric cancer xenograft model. Hypoxia (1% oxygen) induced ADAM9 expression and functional activity in low ADAM9-expressing gastric cancer cells that was inhibited by siRNA knockdown or RAV-18 antibody to levels in normoxic cells. Overall, our studies show that ADAM9 plays an important role in gastric cancer proliferation and invasion, and that while expressed in some gastric cancer cells at high levels that are responsive to functional inhibition and antitumor activity of a catalytic site-directed antibody, other gastric cancer cells have low levels of expression and only when exposed to hypoxia do ADAM9 levels increase and the cells become responsive to ADAM9 antibody inhibition. Therefore, our findings suggest that ADAM9 could be an effective therapeutic target for advanced gastric cancer.

Novel roles of gastrin

The existence of the hormone gastrin in the distal stomach (antrum) has been known for almost 110 years, and the physiological function of this amidated peptide in regulating gastric acid secretion via the CCK2 receptor is now well established. In this brief review we consider important additional roles of gastrin, including regulation of genes encoding proteins such as plasminogen activator inhibitors and matrix metalloproteinases that have important actions on extracellular matrix remodelling. These actions are, at least in part, effected by paracrine signalling pathways and make important contributions to maintaining functional integrity of the gastric epithelium. Recent studies also provide support for the idea that gastrin, in concert with other hormones, could potentially contribute a post-prandial incretin effect. We also review recent developments in the biology of other gastrin gene products, including the precursor progastrin, which causes proliferation of the colonic epithelium and in certain circumstances may induce cancer formation. Glycine-extended biosynthetic processing intermediates also have proliferative effects in colonic mucosa and in some oesophageal cancer cell lines. Whether these additional gene products exert their effects through the CCK2 receptor or a separate entity is currently a matter of debate.

Mouse models of gastric cancer

Animal models have greatly enriched our understanding of the molecular mechanisms of numerous types of cancers. Gastric cancer is one of the most common cancers worldwide, with a poor prognosis and high incidence of drug-resistance. However, most inbred strains of mice have proven resistant to gastric carcinogenesis. To establish useful models which mimic human gastric cancer phenotypes, investigators have utilized animals infected with Helicobacter species and treated with carcinogens. In addition, by exploiting genetic engineering, a variety of transgenic and knockout mouse models of gastric cancer have emerged, such as INS-GAS mice and TFF1 knockout mice. Investigators have used the combination of carcinogens and gene alteration to accelerate gastric cancer development, but rarely do mouse models show an aggressive and metastatic gastric cancer phenotype that could be relevant to preclinical studies, which may require more specific targeting of gastric progenitor cells. Here, we review current gastric carcinogenesis mouse models and provide our future perspectives on this field.

No higher risk for colorectal cancer in atrophic gastritis-related hypergastrinemia

BACKGROUND

Atrophic gastritis of the corporal mucosa is a frequent cause of hypergastrinemia. Hypergastrinemia is implicated in colorectal cancer development.

AIM

To assess whether hypergastrinemic atrophic gastritis is associated with a higher risk of neoplastic colorectal lesions.

METHODS

Among 441 hypergastrinemic atrophic gastritis patients, 160 who were aged >40 and underwent colonoscopy for anaemia, diarrhoea or colorectal cancer-screening were retrospectively selected. Each patient was age- and gender-matched with a normogastrinemic control with healthy stomach. Controls had colonoscopy, gastroscopy with biopsies and gastrin assessment.

RESULTS

160 hypergastrinemic atrophic gastritis patients and 160 controls were included. 28 atrophic gastritis patients and 36 controls had neoplastic colorectal lesions (p=0.33). Patients and controls did not differ for frequency of colorectal adenomas (10.6% vs. 13.1%, p=0.60) or cancer (6.9% vs. 9.4%, p=0.54). Hypergastrinemic atrophic gastritis was not associated with a higher probability of developing colorectal cancer (OR 1.03, 95% CI 0.34-3.16). Age >50 years (OR 3.86) but not hypergastrinemia (OR 0.61) was associated with colorectal cancer.

CONCLUSIONS

Hypergastrinemic atrophic gastritis is not associated with higher risk for colorectal cancer. Atrophic gastritis-related hypergastrinemia is not associated with an increased risk of neoplastic colorectal lesions. Closer surveillance of colonic neoplasia in atrophic gastritis patients seems not appropriate.

Gastrin increases its own synthesis in gastrointestinal cancer cells via the CCK2 receptor

The involvement of the gastrointestinal hormone gastrin in the development of gastrointestinal cancer is highly controversial. Here we demonstrate a positive-feedback loop whereby gastrin, acting via the CCK2 receptor, increases its own expression. Such an autocrine loop has not previously been reported for any other gastrointestinal hormone. Gastrin promoter activation was dependent on the MAP kinase pathway and did not involve Sp1 binding sites or epidermal growth factor receptor transactivation. As the treatment of gastrointestinal cancer cells with amidated gastrin led to increased expression of non-amidated gastrins, the positive-feedback loop may contribute to the sustained increase in circulating gastrins observed in colorectal cancer patients.

Immunostaining of gastric cancer with neuroendocrine differentiation: Reg IV-positive neuroendocrine cells are associated with gastrin, serotonin, pancreatic polypeptide and somatostatin

We previously reported that Reg IV is associated with neuroendocrine (NE) differentiation in gastric cancers. The aim was to examine which NE hormone products are related to Reg IV-positive NE cells and their roles in gastric cancers. In the present study, we performed immunohistochemical analysis in a tissue microarray (TMA) of a consecutive series of 630 cases with ten different antibodies, including chromogranin A, synaptophysin and neural cell adhesion molecule (NCAM) as NE differentiation markers, and gastrin, serotonin, calcitonin, gastrin-releasing peptide (GRP), pancreatic polypeptide (PP), somatostatin and glucagon as NE hormones. In 630 cases, we identified 205 (33%) with NE differentiation and 147 (23%) positive for Reg IV. Reg IV-positive cases showed NE differentiation more frequently than Reg IV-negative cases (P < 0.0001). In 205 cases with NE differentiation, Reg IV-positive cases expressed serotonin (P= 0.0032) and somatostatin (P= 0.036) more frequently than Reg IV-negative cases. Double immunofluorescence staining revealed co-expression of Reg IV with gastrin, serotonin and PP. These results indicate that Reg IV might be a mediating factor of several NE hormones.

The production and role of gastrin-17 and gastrin-17-gly in gastrointestinal cancers

The gastrointestinal peptide hormone gastrin is responsible for initiating the release of gastric acid in the stomach in response to the presence of food and/or humoral factors such as gastrin releasing peptide. However, it has a role in the growth and maintenance of the gastric epithelium, and has been implicated in the formation and growth of gastric cancers. Hypergastrinemia resulting from atrophic gastritis and pernicious anemia leads to hyperplasia and carcinoid formation in rats, and contributes to tumor formation in humans. Additionally, gastrin has been suspected to play a role in the formation and growth of cancers of the colon, but recent studies have instead implicated gastrin processing intermediates, such as gastrin-17-Gly, acting upon a putative, non-cholecystokinin receptor. This review summarizes the production and chemical structures of gastrin and of the processing intermediate gastrin-17-Gly, as well as their activities in the gastrointestinal tract, particularly the promotion of colon cancers.

Achlorhydria is associated with gastric microbial overgrowth and development of cancer: Lessons learned from the gastrin knockout mouse

Gastrin and gastrin receptor-deficient mice have been used for genetic dissection of the role of gastrins in maintaining gastric homeostasis and control of acid secretion. The gastrin knockout mice are achlorhydric due to inactivation of the ECL and parietal cells. Moreover, this achlorhydria is associated with intestinal metaplasia and bacterial overgrowth, which ultimately leads to the development of gastric tumours. The association between progastrin, progastrin-derived processing intermediates and colorectal carcinogenesis has also been examined through genetic or chemical cancer induction in several mouse models, although the clinical relevance of these studies remains unproven. While others have focused on models of increased gastrin production, the present review describes the lessons learned from gastrin-deficient mice. Study of these mice helps our understanding of how dysregulation of gastrin secretion may be implicated in human disease.

Growth of human pancreatic cancer is inhibited by down-regulation of gastrin gene expression

OBJECTIVES

This study evaluated the effects of gastrin messenger RNA (mRNA) down-regulation on growth of human pancreatic cancer.

METHODS

Gastrin expression was examined in human pancreatic cancer cell lines by reverse transcriptase-polymerase chain reaction, and peptide expression was assessed by immunocytochemistry. Gastrin was down-regulated using either stable transfection of an antisense gastrin cDNA or 1 of 3 shRNA (short hairpin RNA) constructs. Tumor formation was evaluated after either subcutaneous or orthotopic injections into nude mice. The effect of nanoliposomes loaded with gastrin siRNA (small interfering RNA) was tested in mice bearing pancreatic tumors.

RESULTS

Stable transfection of gastrin antisense or shRNAs into BxPC-3 cells resulted in clones with more than 90% reduction in gastrin mRNA. Tumor growth rate and incidence of metastases in both wild-type and transfected pancreatic cancer cells were directly proportional to the degrees of gastrin mRNA expression. Immunofluorescence analysis confirmed that gastrin peptide levels were decreased in antisense and shRNA tumors. Gastrin knockdown clones had lower Ki-67 and increased cleaved caspase-3 staining, consistent with known effects of gastrin on proliferation and apoptosis. Tumors in mice treated with gastrin siRNA were smaller than controls.

CONCLUSIONS

These results suggest that RNAi targeting of gastrin could serve as an effective treatment for pancreatic cancer.

Review article: Strategies to determine whether hypergastrinaemia is due to Zollinger-Ellison syndrome rather than a more common benign cause

BACKGROUND

As there is considerable overlap between the fasting serum gastrin concentrations found in Zollinger-Ellison syndrome and various common conditions such as Helicobacter pylori infection and acid suppressing medication use, establishing the cause of hypergastrinaemia in individual cases can sometimes be difficult.

AIM

To review the causes of hypergastrinaemia and the role of additional non-invasive investigations in hypergastrinaemic patients.

METHODS

Review of articles following a Pubmed search.

RESULTS

As gastrinomas may cause serious complications and be potentially life threatening, investigation of hypergastrinaemic patients should particularly focus on confirming or refuting the diagnosis of Zollinger-Ellison syndrome. Establishing the cause of hypergastrinaemia may be difficult when there is only a mild-to-moderate elevation of fasting serum gastrin concentration and concurrent treatment with proton pump inhibitor drugs and the presence of H. pylori infection can both confuse the clinical picture. A variety of provocative tests are therefore useful for establishing whether a hypergastrinaemic patient has a gastrinoma and current evidence suggests that the secretin test should be used first line.

CONCLUSIONS

We suggest an algorithm for the investigation of patients found to have an elevated fasting serum gastrin concentration and address the roles of gastrin stimulation tests in current clinical practice.

Identification of ezrin as a target of gastrin in immature mouse gastric parietal cells

The gastric acid-secreting parietal cell exhibits profound morphological changes on stimulation. Studies in gastrin null (Gas-KO) mice indicate that maturation of parietal cell function depends on the hormone gastrin acting at the G-protein-coupled cholecystokinin 2 receptor. The relevant cellular mechanisms are unknown. The application of differential mRNA display to samples of the gastric corpus of wild-type (C57BL/6) and Gas-KO mice identified the cytoskeletal linker protein, ezrin, as a previously unsuspected target of gastrin. Gastrin administered in vivo or added to gastric glands in vitro increased ezrin abundance in Gas-KO parietal cells. In parietal cells of cultured gastric glands from wild-type mice treated with gastrin, histamine or carbachol, ezrin was localized to vesicular structures resembling secretory canaliculi. In contrast, in cultured parietal cells from Gas-KO mice, ezrin was typically distributed in the cytosol, and this did not change after incubation with gastrin, histamine or carbachol. However, priming with gastrin for approximately 24 h, either in vivo prior to cell culture or by addition to cultured gastric glands, induced the capacity for secretagogue-stimulated localization of ezrin to large vesicular structures in Gas-KO mice. Similarly, in a functional assay based on measurement of intracellular pH, cultured parietal cells from Gas-KO mice were refractory to gastrin unless primed. The priming effect of gastrin was not attributable to the paracrine mediator histamine, but was prevented by inhibitors of protein kinase C and transactivation of the epidermal growth factor receptor. We conclude that in gastrin null mice there is reduced ezrin expression and a defect in ezrin subcellular distribution in gastric parietal cells, and that both can be reversed by priming with gastrin.

E-cadherin gene promoter hypermethylation in H. pylori-induced enlarged fold gastritis

BACKGROUND

Promoter hypermethylation of E-cadherin plays an important role on gastric carcinogenesis. We have previously reported that the odds ratio for gastric carcinoma and the prevalence of diffuse-type early gastric carcinoma in Helicobacter pylori-induced enlarged fold gastritis increased with increasing fold width. Thus, we examined E-cadherin methylation in gastric mucosa from H. pylori-induced enlarged fold gastritis before and after H. pylori eradication. Moreover, we analyzed the mechanism of H. pylori infection-induced E-cadherin hypermethylation.

MATERIALS AND METHODS

Twenty-three H. pylori-positive patients with enlarged folds, 18 H. pylori-positive and seven H. pylori-negative patients without enlarged folds, were involved in the study. E-cadherin promoter methylation was studied using quantitative methylation-specific polymerase chain reaction. We investigated methylation percentage and DNA methyltransferase activity in gastric cancer cell lines treated with EGF, TNFalpha, and MG132.

RESULTS

E-cadherin methylation percentage of the gastric antral and body mucosa in H. pylori-positive patients with enlarged folds was much greater than that in both H. pylori-positive and -negative patients without enlarged folds. After H. pylori eradication, the methylation percentage in six patients with enlarged fold gastritis decreased significantly from 15.6 +/- 3.9 to 8.8 +/- 2.2 (p < .05). Moreover, the methylation was induced by TNFalpha, MG132, and EGF treatment, and DNA methyltransferase activity was induced by EGF treatment in MKN-1 cells.

CONCLUSIONS

Our findings suggest that the hypermethylation of E-cadherin promoter might be involved in the process of gastric carcinoma through the specialized factors in H. pylori-induced enlarged fold gastritis.

Role of gastrin peptides in carcinogenesis

Gastrin gene expression is upregulated in a number of pre-malignant conditions and established cancer through a variety of mechanisms. Depending on the tissue where it is expressed and the level of expression, differential processing of the polypeptide product leads to the production of different biologically active peptides. In turn, acting through the classical CCK-2R receptor, CCK-2R isoforms and alternative receptors, these peptides trigger signalling pathways which influence the expression of downstream genes that affect cell survival, angiogenesis and invasion. Here we review this network of events, highlighting the importance of cellular context for interpreting the role of gastrin peptides and a possible role for gastrin in supporting the early stage of carcinogenesis.

G17DT: an antigastrin immunogen for the treatment of gastrointestinal malignancy

G17DT (Gastrimmune) is an antigastrin-17 immunogen, raising antibodies that blockade gastrin-stimulated tumor growth. It has completed Phase III trials in patients with pancreatic cancer, and Phase III trials in gastric cancer are planned. Preclinical studies have confirmed that the G17DT-induced antibodies both reduce gastrin-17-stimulated gastric acid secretion and inhibit gastrin from interacting with the cholecystokinin-2 receptor. The efficacy of both passive and active immunization with G17DT has been established in a number of tumor systems, with additive effects demonstrated in combination chemotherapy in pancreatic, colon and gastric tumor models. Phase I/II studies in advanced gastrointestinal malignancies have shown no systemic or autoimmune reactions to active immunization with G17DT. The use of an optimized dose and dosing schedule has yielded a high proportion of antibody responders (70%), with minimal side effects and antibody titers measurable within 2 - 4 weeks. Phase II trials of G17DT in combination with chemotherapy have also been conducted in gastric and colorectal cancer. A Phase III, multicenter, double-blind, randomized, controlled trial of G17DT versus placebo in patients with advanced pancreatic cancer confirmed improved survival of patients in the G17DT group through an intention-to-treat analysis. The results of a randomized, double-blind, multinational, multicenter study of G17DT in combination with gemcitabine versus placebo and gemcitabine in patients with advanced pancreatic cancer failed to show improved overall survival except on subset analysis of patients with high antibody titers. Therefore, G17DT represents an emerging new modality for gastrointestinal malignancy.

Attack and defence in the gastric epithelium - a delicate balance

The gastric epithelium is a complex structure formed into tubular branched gastric glands. The glands contain a wide variety of cell types concerned with the secretion of hydrochloric acid, proteases, mucus and a range of signalling molecules. All cell types originate from stem cells in the neck region of the gland, before migrating and differentiating to assume their characteristic positions and functions. Endocrine and local paracrine mediators are of crucial importance for maintaining structural and functional integrity of the epithelium, in the face of a hostile luminal environment. The first such mediator to be recognized, the hormone gastrin, was identified over a century ago and is now established as the major physiological stimulant of gastric acid secretion. Recent studies, including those using mice that overexpress or lack the gastrin gene, suggest a number of previously unrecognized roles for this hormone in the regulation of cellular proliferation, migration and differentiation. This review focuses on the identification of hitherto unsuspected gastrin-regulated genes and discusses the paracrine cascades that contribute to the maintenance of gastric epithelial architecture and secretory function. Helicobacter infection is also considered in cases where it shares targets and signalling mechanisms with gastrin.

Potentiation of oxyntic atrophy-induced gastric metaplasia in amphiregulin-deficient mice

BACKGROUND & AIMS

The loss of parietal cells from the gastric mucosa (oxyntic atrophy) is a critical step in the pathogenesis of chronic gastritis and gastric adenocarcinoma. Parietal cells are known to secrete epidermal growth factor receptor (EGFR) ligands, which are critical regulators of differentiation in the gastric mucosa. Although all of the actions of EGFR ligands are mediated through a common EGFR protein, individual ligands may produce different physiologic responses. Previous investigations have suggested that a deficit in EGFR signaling in waved-2 mice accelerates the emergence of metaplasia after induction of acute oxyntic atrophy. We sought to determine whether specific EGFR ligands regulate the metaplastic response to oxyntic atrophy.

METHODS

To induce spasmolytic polypeptide-expressing metaplasia (SPEM), amphiregulin (AR) and transforming growth factor-alpha-deficient mice and their wild-type littermates were treated with DMP-777 for 0-14 days and for 14 days followed by 14 days of recovery off drug. We evaluated the gastric mucosal response to oxyntic atrophy using cell lineage-specific markers.

RESULTS

Although loss of transforming growth factor-alpha did not influence the induction of SPEM, loss of AR caused an acceleration and amplification in the induction of SPEM after acute oxyntic atrophy. Trefoil factor family 2/spasmolytic polypeptide and intrinsic factor dual-immunostaining cells significantly increased in the SPEM of AR-deficient mice. At the bases of glands, intrinsic factor immunoreactive cells also were costained for 5-bromo-2'-deoxyuridine, suggesting their re-entry into the cell cycle.

CONCLUSIONS

The absence of AR promoted the rapid emergence of SPEM in response to oxyntic atrophy.

Gastrin - active participant or bystander in gastric carcinogenesis?

Gastrin is a pro-proliferative, anti-apoptotic hormone with a central role in acid secretion in the gastric mucosa and a long-standing association with malignant progression in transgenic mouse models. However, its exact role in human gastric malignancy requires further validation. Gastrin expression is tightly regulated by two closely associated hormones, somatostatin and gastrin-releasing peptide, and aspects of their interaction may be deregulated during progression to gastric adenocarcinoma. Furthermore, agonists and antagonists of the receptors for all three hormones have shown modest clinical efficacy against gastric adenocarcinoma, which might provide useful information on the future combined use of these agents.

Hyperplastic polyposis and cancer of the colon with gastrinoma of the duodenum

BACKGROUND

A 64-year-old woman presented to the emergency room with a 3-month history of intermittent abdominal cramps, accompanied by nausea, vomiting, anorexia, and decreased bowel movements consistent with a partial intestinal obstruction. She had a 12-year history of peptic ulcers, which had been treated with histamine-2 blockers.

INVESTIGATIONS

Physical examination, abdominal X-ray, abdominal CT scan, colonoscopy and assessment of gastrin levels.

DIAGNOSIS

Duodenal neuroendocrine neoplasm showing gastrin expression and stage III (T3N2M0), poorly differentiated adenocarcinoma of the cecum arising from hyperplastic polyposis.

MANAGEMENT

Right-sided hemicolectomy with ileocolonic anastomosis, duodenal resection, leucovorin and 5-fluorouracil chemotherapy, annual colonoscopic surveillance, and polypectomy.

Helicobacter pylori can induce heparin-binding epidermal growth factor expression via gastrin and its receptor

Both gastrin and Helicobacter pylori have been shown capable of up-regulating gene expression and protein shedding of heparin-binding epidermal growth factor (HB-EGF). Furthermore, the bacteria have previously been shown to induce serum hypergastrinemia in infected individuals. The aim of this work was to assess the extent to which the ability of H. pylori to up-regulate expression of HB-EGF can be attributed to its effect on gastrin. Gastric cells, transfected with either gastrin small interfering RNA or antisense plasmid or the gastrin/cholecystokinin-2 receptor (CCK-2R), were cultured for 24 hours with H. pylori(+/-), a CCK-2R antagonist. Gene expression levels were measured using reverse transcription-PCR, whereas protein changes were measured using ELISA, Western blotting, and immunofluorescence. H. pylori induced significantly higher levels of HB-EGF gene expression and ectodomain shedding in the CCK-2R-transfected cells than the vector control (P < 0.01). Addition of the CCK-2R inhibitor significantly decreased gene and shedding up-regulation. Gastrin down-regulation reduced the effect of the bacteria on HB-EGF gene and protein expression levels. Endogenous gastrin and CCK-2R expression were also found to be significantly up-regulated in all cell lines as a result of exposure to H. pylori (P < 0.02). Gastric mucosal tissue from H. pylori-infected individuals had significantly higher CCK-2R expression levels than noninfected (P < 0.003), and in hypergastrinemic mice, there was an increase in HB-EGF-expressing cells in the gastric mucosa and colocalization of HB-EGF with CCK-2R-positive enterochromaffin-like cells. In conclusion, gastrin and the CCK-2R play significant roles in the induction of HB-EGF gene and protein expression and ectodomain shedding by H. pylori.

Leptin stimulates proliferation and inhibits apoptosis in Barrett's esophageal adenocarcinoma cells by cyclooxygenase-2-dependent, prostaglandin-E2-mediated transactivation of the epidermal growth factor receptor and c-Jun NH2-terminal kinase activation

Obesity is an important risk factor for esophageal adenocarcinoma (EAC), and elevated serum leptin is characteristic of obesity. We hypothesized that leptin may have biological effects in promoting esophageal adenocarcinoma and examined the effects of leptin on the OE33 Barrett's-derived EAC line. Proliferation was assessed by dimethylthiazoldiphenyltetra-zoliumbromide and 5-bromo-2'-deoxyuridine incorporation assays and apoptosis by ELISA of intracellular nucleosomes. Intracellular signaling was examined using specific pharmacological inhibitors and direct detection of phosphorylated active kinases. Expression of the long and short leptin receptors by OE33 cells was confirmed by RT-PCR, Western blotting and immunocytochemistry. Leptin stimulated OE33 cell proliferation in a dose-dependent manner and inhibited apoptosis. These effects were dependent on cyclooxygenase (COX)-2 and replicated by adding prostaglandin E2 (PGE2). The effects of PGE2 and leptin were abolished by the EP-4 antagonist AH23848. ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and Janus tyrosine kinase (JAK)-2 were activated upstream of COX-2 induction, whereas the epidermal growth factor receptor and c-Jun NH2-terminal kinase (JNK) were downstream of COX-2. The activation of ERK and Akt but not p38 MAPK was JAK2 dependent. PGE2 stimulated phosphorylation of JNK in an EGF receptor-dependent manner, and activation of the epidermal growth factor receptor required protein kinase C, src, and matrix metalloproteinase activities. We conclude that leptin stimulates cell proliferation and inhibits apoptosis in OAC cells via ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and JAK2-dependent activation of COX-2 and PGE2 production. Subsequent PGE2-mediated transactivation of the epidermal growth factor receptor and JNK activation are essential to the leptin effects. These effects may contribute to the greatly increased risk of esophageal adenocarcinoma in obesity.

Cholecystokinin and gastrin receptors

Cholecystokinin and gastrin receptors (CCK1R and CCK2R) are G protein-coupled receptors that have been the subject of intensive research in the last 10 years with corresponding advances in the understanding of their functioning and physiology. In this review, we first describe general properties of the receptors, such as the different signaling pathways used to exert short- and long-term effects and the structural data that explain their binding properties, activation, and regulation. We then focus on peripheral cholecystokinin receptors by describing their tissue distribution and physiological actions. Finally, pathophysiological peripheral actions of cholecystokinin receptors and their relevance in clinical disorders are reviewed.

Mechanism for Src activation by the CCK2 receptor: Patho-physiological functions of this receptor in pancreas

AIM: To investigate in vivo, whether CCK2 receptors (CCK2R) regulate proteins known to play a crucial role in cell proliferation and cancer development and analyse in vitro the molecular mechanisms that lead to Src activation; in particular, to identify the domains within the CCK2R sequence that are implicated in this activation.

METHODS: The expression and activation of Src and ERK were studied in vivo using immuno-fluorescence and western-blot techniques. We used pancreatic tissues derived from wild type or Elas-CCK2 mice that expressed the CCK2R in pancreatic acini, displayed an increased pancreatic growth and developed preneoplastic lesions. The pancreatic tumor cell line AR4-2J expressing the endogenous CCK2R or COS-7 cells transiently transfected with wild type or mutant CCK2R were used as in vitro models to study the mechanism of Src activation. Src activation was measured by in vitro kinase assays, ERK activation by western blot using anti-phospho-ERK antibodies and the involvement of Src in gastrin-induced cell proliferation by MTT test.

RESULTS: We showed in vivo that the targeted CCK2R expression in the pancreas of Elas-CCK2 mice, led to the activation of Src and the ERK pathway. Src was activated upstream of the ERK pathway by the CCK2R in pancreatic tumoral cells and contributed to the proliferative effects mediated by this receptor. In vitro results demonstrated that activation of the Src/ERK pathway by the CCK2R required the NPXXY motif, located within the CCK2R sequence at the end of the 7^th transmembrane domain, and suggested the putative role of Gq in this mechanism.

CONCLUSION: Deregulation of the Src/ERK pathway by the CCK2R might represent an early step that contributes to cell proliferation, formation of preneoplastic lesions and pancreatic tumor development.

Gastrin enhances the angiogenic potential of endothelial cells via modulation of heparin-binding epidermal-like growth factor

This study examined whether gastrin modulates endothelial cell activity via heparin-binding epidermal growth factor-like growth factor (HB-EGF) expression. Human umbilical vascular endothelial cells (HUVEC) were assessed for tubule formation in the presence of amidated gastrin-17 (G17) and glycine-extended gastrin-17 (GlyG17) peptides. HB-EGF gene and protein expressions were measured by quantitative reverse transcription-PCR, immunocytochemistry, and Western blotting, and HB-EGF shedding by ELISA. Matrix metalloproteinases MMP-2, MMP-3, and MMP-9 were assessed by Western blotting. Chick chorioallantoic membrane studies measured the in vivo angiogenic potential of gastrin and microvessel density (MVD) was assessed in large intestinal premalignant lesions of hypergastrinaemic APC(Min) mice. MVD was also examined in human colorectal tumor and resection margin normals and correlated with serum-amidated gastrin levels (via RIA) and HB-EGF protein expression (via immunohistochemistry). HUVEC cells showed increased tubule and node formation in response to G17 (186%, P < 0.0005) and GlyG17 (194%, P < 0.0005). This was blockaded by the cholecystokinin-2 receptor (CCK-2R) antagonists JB95008 and JMV1155 and by antiserum to gastrin and HB-EGF. Gastrin peptides increased HB-EGF gene expression/protein secretion in HUVEC and microvessel-derived endothelial cells and the levels of MMP-2, MMP-3, and MMP-9. G17 promoted angiogenesis in a chorioallantoic membrane assay, and MVD was significantly elevated in premalignant large intestinal tissue from hypergastrinaemic APC(Min) mice. In terms of the clinical situation, MVD in the normal mucosa surrounding colorectal adenocarcinomas correlated with patient serum gastrin levels and HB-EGF expression. Gastrin peptides, acting through the CCK-2R, enhance endothelial cell activity in models of angiogenesis. This may be mediated through enhanced expression and shedding of HB-EGF, possibly resulting from increased activity of matrix metalloproteinases. This proangiogenic effect translates to the in vivo and human situations and may add to the tumorigenic properties attributable to gastrin peptides in malignancy.

Attenuation of Peroxisome Proliferator-activated Receptor γ (PPARγ) Mediates Gastrin-stimulated Colorectal Cancer Cell Proliferation

Peroxisome proliferators-activated receptor gamma (PPARgamma) has been shown to suppress cell proliferation and tumorigenesis, whereas the gastrointestinal regulatory peptide gastrin stimulates the growth of neoplastic cells. The present studies were directed to determine whether changes in PPARgamma expression might mediate the effects of gastrin on the proliferation of colorectal cancer (CRC). Initially, using growth assays, we determined that the human CRC cell line DLD-1 expressed both functional PPARgamma and gastrin receptors. Amidated gastrin (G-17) attenuated the growth suppressing effects of PPARgamma by decreasing PPARgamma activity and total protein expression, in part through an increase in the rate of proteasomal degradation. G-17-induced degradation of PPARgamma appeared to be mediated through phosphorylation of PPARgamma at serine 84 by a process involving the biphasic phosphorylation of ERK1/2 and activation of the epidermal growth factor receptor (EGFR). These results were confirmed through the use of EGFR antagonist AG1478 and MEK1 inhibitor PD98059. Furthermore, mutation of PPARgamma at serine 84 reduced the effects of G-17, as evident by inability of G-17 to attenuate PPARgamma promoter activity, degrade PPARgamma, or inhibit the growth suppressing effects of PPARgamma. The results of these studies demonstrate that the trophic properties of gastrin in CRC may be mediated in part by transactivation of the EGFR and phosphorylation of ERK1/2, leading to degradation of PPARgamma protein and a decrease in PPARgamma activation.

Helicobacter pylori eradication to prevent gastric cancer: Underlying molecular and cellular mechanisms

Numerous cellular and molecular events have been described in development of gastric cancer. In this article, we overviewed roles of Helicobacter pylori (H pylori) infection on some of the important events in gastric carcinogenesis and discussed whether these cellular and molecular events are reversible after cure of the infection. There are several bacterial components affecting gastric epithelial kinetics and promotion of gastric carcinogenesis. The bacterium also increases risks of genetic instability and mutations due to NO and other reactive oxygen species. Epigenetic silencing of tumor suppressor genes such as RUNX3 may alter the frequency of phenotype change of gastric glands to those with intestinal metaplasia. Host factors such as increased expression of growth factors, cytokines and COX-2 have been also reported in non-cancerous tissue in H pylori-positive subjects. It is noteworthy that most of the above phenomena are reversed after the cure of the infection. However, some of them including overexpression of COX-2 continue to exist and may increase risks for carcinogenesis in metaplastic or dysplastic mucosa even after successful H pylori eradication. Thus, H pylori eradication may not completely abolish the risk for gastric carcinogenesis. Efficiency of the cure of the infection in suppressing gastric cancer depends on the timing and the target population, and warrant further investigation.

An overview of acetic acid ulcer models--the history and state of the art of peptic ulcer research

Four types of experimental chronic ulcer models, named acetic acid ulcer models, have been developed to examine the healing process of peptic ulcers, screen anti-ulcer drugs, and better evaluate the adverse effects of various anti-inflammatory drugs on the gastrointestinal mucosa. The model easily and reliably produces round, deep ulcers in the stomach and duodenum, allowing acetic acid ulcer production in mice, rats, Mongolian gerbils, guinea pigs, cats, dogs, miniature pigs, and monkeys. These ulcer models highly resemble human ulcers in terms of both pathological features and healing process. The models have been established over the past 35 years and are now used throughout the world by basic and clinical scientists. One of the characteristic features of acetic acid ulcers in rats is the spontaneous relapse of healed ulcers >100 d after ulceration, an endoscopically confirmed phenomenon. Indomethacin significantly delays the healing of acetic acid ulcers, probably by reducing endogenous prostaglandins and inhibiting angiogenesis in ulcerated tissue. Helicobacter pylori significantly delays healing of acetic acid ulcers and causes relapse of healed ulcers at a high incidence in Mongolian gerbils. Anti-secretory drugs (e.g. omeprazole), prostaglandin analogs, mucosal defense agents (e.g. sucralfate), and various growth factors all significantly enhance healing of acetic acid ulcers. Gene therapy with epidermal growth factor and vascular endothelial growth factor applied to the base of acetic acid ulcers in rats is effective in enhancing ulcer healing. Since an inhibitor of nitric oxide syntase prevents ulcer healing, nitric oxide might be involved in the mechanism underlying ulcer healing. We conclude that acetic acid ulcer models are quite useful for various studies related to peptic ulcers.

Gastrin and cancer: a review

In 1905, a Cambridge physiologist, John Sydney Edkins, initially identified a hormone responsible of gastric acid secretion, which he called gastric secretin, or gastrin. While gastrin's role in acid secretion is now well defined, more recent studies have implicated the various isoforms of gastrin in cancer. Important advances in the last decade have included the recognition of biological activity for processing intermediates such as progastrin and the glycine-extended gastrin. Here, we give an overview of the roles of these peptides in cancer, highlighted by molecular, cellular and integrated studies on animal models for progastrin-derived peptides and their receptors.

Involvement of JAK2 upstream of the PI 3-kinase in cell-cell adhesion regulation by gastrin

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway has been implicated in cell transformation and proliferation. Besides aberrant cell proliferation, loss of cell-cell adhesion during epithelial-mesenchymal transition (EMT) is an important event which occurs during development of epithelial cancers. However, the role of JAK-dependent pathways in this process is not known. We analyzed the involvement of these pathways in the regulation of E-cadherin-dependent cell-cell adhesion by gastrin, a mitogenic factor for gastrointestinal (GI) tract. We identified JAK2/STAT3 as a new pathway in gastrin signaling. We demonstrated that JAK2 functions as an upstream mediator of the phosphatidylinositol 3 (PI 3)-kinase activity in gastrin signaling. Indeed, we observed a coprecipitation of both kinases and an inhibition of gastrin-induced PI 3-kinase activation when JAK2 activity is blocked. We also demonstrated that loss of cell-cell adhesion and the increase in cell motility induced by gastrin required the activation of JAK2 and the PI 3-kinase. Indeed, the modifications in localization of adherens junctions proteins and the migration, observed in gastrin-stimulated cells, were reversed by inhibition of both kinases. These results described the involvement of JAK2 in the modulation of cell-cell adhesion in epithelial cells. They support a possible role of JAK2 in the epithelial-mesenchymal transition which occurs during malignant development.

Clinical endocrinology and metabolism. Gastrin

The gastric hormone gastrin stimulates gastric acid secretion and epithelial cell proliferation. Multiple active products are generated from the precursor, preprogastrin, including the well-characterized amidated gastrins acting at the cholecystokinin-2 (CCK-2, or gastrin-CCK(B)) receptor, and others that may be growth factors in a range of cancers. Plasma concentrations of the amidated gastrins are elevated as a consequence of gastrin-secreting tumours (gastrinomas) and in conditions in which the normal inhibition of the antral G-cell by acid is depressed, for example chronic atrophic gastritis and prolonged treatment with proton pump inhibitors. There may also be increased gastrin release in Helicobacter pylori infection. Provocative tests for the diagnosis of gastrinoma include the secretin and calcium infusion tests. Hypergastrinaemia is associated with enterochromaffin-like (ECL) cell proliferation; the factors that determine progression to ECL cell dysplasia and gastric ECL cell carcinoid tumours are discussed. Several strategies for inhibiting the effects of gastrin are under evaluation, and their potential application is discussed.

Gastrin and interleukin-1beta stimulate growth factor secretion from cultured rabbit gastric parietal cells

The hormone gastrin stimulates proliferation of the gastric mucosa. Inflammation of the stomach is also associated with increased proliferation. The proliferative response is important in the reparative response to injury but can be deleterious by predisposing to the development of cancer. Parietal cells, but not the cells in the proliferative zone of the gastric glands, express the appropriate gastrin receptor. Parietal cells may mediate the trophic effects of gastrin by secreting other growth factors. The role of parietal cells in the proliferative responses has been examined in this study. Rabbit parietal cells were cultured with gastrin or the cytokine interleukin-1beta for 18 hours. The conditioned medium from gastrin or IL-1beta stimulated parietal cells increased proliferation of HeLa cells in an epidermal growth factor-receptor dependant manner. Gastrin and IL-1beta stimulated the secretion of heparin-binding epidermal growth factor and amphiregulin but not transforming growth factor-alpha from parietal cells. Combinations of gastrin and IL-1beta on growth factor secretion were synergistic. The protein kinase C inhibitor staurosporine abolished these stimulatory effects of gastrin and IL-1beta. Divergent effects on histamine-stimulated acid secretion were observed; 18 hours pre-treatment with gastrin enhanced acid secretion by 50% but IL-1beta inhibited acid secretion in both control and gastrin pre-treated parietal cells. The acid-secreting parietal cell plays a central role in the regulation of mucosal proliferation in gastric inflammation. Secretion of paracrine growth factors by parietal cells may be an important point of integration between the endocrine and inflammatory stimuli in determining mucosal responses to injury and inflammation.

Gastrin: old hormone, new functions

It is exactly a century since the gastric hormone gastrin was first described as a blood-borne regulator of gastric acid secretion. The identities of the main active forms of the hormone (the "classical gastrins") and their cellular and molecular sites of action in regulating acid secretion have all attracted sustained attention. However, recent work on peptides derived from the gastrin precursor that do not stimulate acid secretion ("non-classical gastrins"), together with studies on mice over-expressing the gene, or in which the gastrin gene has been deleted, suggest hitherto unsuspected roles in regulating cell proliferation, migration, and differentiation. Moreover, microarray and proteomic studies have identified previously unsuspected target genes of the classical gastrins. Some of the newer actions have implications for our understanding of the progression to cancer in oesophagus, stomach, pancreas and colon, all of which have recently been linked in one way or another to dysfunctional signalling involving products of the gastrin gene. The present review focuses on recent progress in understanding the biology of both classical and non-classical gastrins.

The biological and therapeutic importance of gastrin gene expression in pancreatic adenocarcinomas

The gastrin gene is expressed widely in pancreatic adenocarcinomas and the study aimed to assess its role in both the resistance of cancer cells to apoptosis and the sensitivity of cells to chemotherapeutic agents. Two human pancreatic cell lines, PAN1 and BXPC3, expressed gastrin at both the RNA and protein levels and are shown to be representative of human pancreatic adenocarcinomas in terms of gastrin expression. Inhibition of endogenous gastrin production by tumor cells was achieved with neutralizing gastrin antiserum and transfection with a gastrin antisense plasmid. Gastrin antiserum synergized with both taxotere and gemcitabine in inhibiting the in vitro growth of the PAN1 cell line with the inhibitory effect of the antiserum increasing from 12.7% to 70.2% with taxotere (P < 0.05) and 28.6% with gemcitabine (P < 0.01) after controlling for the effects of the cytotoxics. Synergy was only achieved with taxotere in BXPC3 cells with the inhibitory effect of gastrin antiserum increasing from 22.9% to 50.0% (P < 0.005). Cells transfected with gastrin antisense had reduced in vitro growth in low serum conditions and were poorly tumorigenic in nude mice at an orthotopic site. Gastrin antisense-transfected PAN1 cells had increased sensitivity to the antiproliferative effects of both gemcitabine (IC50 of > 100 microg/ml reduced to 0.1 microg/ml) and taxotere (IC50 of 20 microg/ml reduced to < 0.01 microg/ml) when compared with vector controls. The increased sensitivity of PAN1 antisense coincided with increased caspase-3 activity and reduced protein kinase B/Akt phosphorylation in response to both gemcitabine and taxotere. Gastrin gene circumvention may be an optimal adjunct to chemotherapeutic agents, such as taxotere and gemcitabine, in pancreatic adenocarcinoma.

A phase II study of G17DT in gastric carcinoma

PURPOSE

G17DT is a gastrin immunogen, raising antibodies that blockade gastrin-stimulated growth. The aim of the study was to characterise antibody response and assess safety and tolerability of G17DT given to patients with gastric cancer.

EXPERIMENTAL DESIGN

G17DT was administered to 52 patients with gastric adenocarcinoma at weeks 0, 2 and 6 by intramuscular injection at doses of 10, 100 and 250 microg. Antibody levels were measured by an ELISA assay. A radioligand displacement assay determined the ability of G17DT-immunised patients' sera to inhibit binding of 125IG17 to cholecystokinin (CCK)-2 receptors.

RESULTS

By week 12 of the study, 6/12 evaluable stage I-III patients achieved an antibody response in the 10 microg group, 7/11 in the 100 microg group, and 11/12 in the 250 microg group. Stage IV patients dosed at 250 microg achieved a similar response rate to stage I-III patients dosed at 10 or 100 microg. G17DT was well tolerated in 47/52 patients. Two patients suffered significant adverse reactions including injection site pain and abscess. G17DT antibodies displaced iodinated gastrin from CCK-2 receptors, with the level of displacement correlating with antibody titre.

CONCLUSIONS

G17DT immunisation is a well-tolerated method of raising functional antibodies to 17 amino acid gastrin forms in patients with gastric carcinomas.