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.

Humoral regulation of heart rate during digestion in pythons (Python molurus and Python regius).

Pythons exhibit a doubling of heart rate when metabolism increases several times during digestion. Pythons, therefore, represent a promising model organism to study autonomic cardiovascular regulation during the postprandial state, and previous studies show that the postprandial tachycardia is governed by a release of vagal tone as well as a pronounced stimulation from nonadrenergic, noncholinergic (NANC) factors. Here we show that infusion of plasma from digesting donor pythons elicit a marked tachycardia in fasting snakes, demonstrating that the NANC factor resides in the blood. Injections of the gastrin and cholecystokinin receptor antagonist proglumide had no effect on double-blocked heart rate or blood pressure. Histamine has been recognized as a NANC factor in the early postprandial period in pythons, but the mechanism of its release has not been identified. Mast cells represent the largest repository of histamine in vertebrates, and it has been speculated that mast cells release histamine during digestion. Treatment with the mast cell stabilizer cromolyn significantly reduced postprandial heart rate in pythons compared with an untreated group but did not affect double-blocked heart rate. While this study indicates that histamine induces postprandial tachycardia in pythons, its release during digestion is not stimulated by gastrin or cholecystokinin nor is its release from mast cells a stimulant of postprandial tachycardia.

Randomized Controlled Trial of the Gastrin/CCK2 Receptor Antagonist Netazepide in Patients with Barrett's Esophagus.

Hypergastrinemia has been associated with high-grade dysplasia and adenocarcinoma in patients with Barrett's esophagus, and experimental studies suggest proinflammatory and proneoplastic effects of gastrin on Barrett's esophagus. This is of potential concern, as patients with Barrett's esophagus are treated with medications that suppress gastric acid production, resulting in increased physiologic levels of gastrin. We aimed to determine whether treatment with the novel gastrin/CCK2 receptor antagonist netazepide reduces expression of markers associated with inflammation and neoplasia in Barrett's esophagus. This was a randomized, double-blind, placebo-controlled trial of netazepide in patients with Barrett's esophagus without dysplasia. Subjects were treated for 12 weeks, with endoscopic assessment at baseline and at end of treatment. The primary outcome was within-individual change in cellular proliferation as assessed by Ki67. Secondary analyses included changes in gene expression, assessed by RNA-sequencing, and safety and tolerability. A total of 20 subjects completed the study and were included in the analyses. There was no difference between arms in mean change in cellular proliferation (netazepide: +35.6 Ki67+ cells/mm2, SD 620.7; placebo: +307.8 Ki67+ cells/mm2, SD 640.3; P = 0.35). Netazepide treatment resulted in increased expression of genes related to gastric phenotype (TFF2, MUC5B) and certain cancer-associated markers (REG3A, PAX9, MUC1), and decreased expression of intestinal markers MUC2, FABP1, FABP2, and CDX1 No serious adverse events related to study drug occurred. The gastrin/CCK2 receptor antagonist netazepide did not reduce cellular proliferation in patients with nondysplastic Barrett's esophagus. Further research should focus on the biological effects of gastrin in Barrett's esophagus.Prevention Relevance: Treatment of patients with Barrett's esophagus with a gastrin/CCK2 receptor antagonist did not have obvious chemopreventive effects.

Blocking gastrin and CCK-B autocrine loop affects cell proliferation and apoptosis in vitro.

Gastrin and cholecystokinin-B receptor (CCK-B) were co-expressed in human gastric carcinoma tissues, suggesting that a functional autocrine loop, the gastrin and CCK-B receptor loop, may be presented in gastric cancer cells and play an important role in the pathogenesis and progression of gastric carcinomas. The present study was aimed at studying the effects of blocking the gastrin and CCK-B receptor loop on cell proliferation and apoptosis in gastric cancer cell line SGC-7901 cells (SGC-7901 cells). First, the expression of gastrin and CCK-B receptor mRNAs and gastrin protein in SGC-7901 cells were measured by RT-PCR and immunocytochemistry, respectively. Radioimmunoassay (RIA) was used to detect the concentrations of gastrin in culture medium. The gastrin-CCK-B receptor axis was blocked by using a specific neutralizing antibody against human gastrin and siRNA specifically targeting human CCK-B receptors, respectively. Flow cytometry was used to measure the cell cycle and apoptotic cells, and western blotting was used to measure the expression of CCK-B receptor, caspase-3, and matrix metalloproteinase-2 (MMP-2) in cells. The results showed that SGC-7901 cells not only coexpressed gastrin and CCK-B receptor mRNAs, but also endogenously secreted gastrin protein into the culture medium, thus forming gastrin-CCK-B receptor autocrine loop. Biologically, disrupting gastrin-CCK-B receptor autocrine loop by neutralizing the endogenous gastrin or by knocking down CCK-B receptor expression significantly inhibited the cell proliferation and decreased the percentage of cells residing in the S-phase of the cell cycle, and meanwhile promoted cell apoptosis and increased caspase-3 expression as well as decreased MMP-2 expression. An autocrine loop between endogenously secreted gastrin and CCK-B receptors may play a key role in the regulation of cell proliferation and apoptosis in SGC-7901 cells.

Netazepide Inhibits Expression of Pappalysin 2 in Type 1 Gastric Neuroendocrine Tumors.

BACKGROUND & AIMS: In patients with autoimmune atrophic gastritis and achlorhydria, hypergastrinemia is associated with the development of type 1 gastric neuroendocrine tumors (gNETs). Twelve months of treatment with netazepide (YF476), an antagonist of the cholecystokinin B receptor (CCKBR or CCK2R), eradicated some type 1 gNETs in patients. We investigated the mechanisms by which netazepide induced gNET regression using gene expression profiling. METHODS: We obtained serum samples and gastric corpus biopsy specimens from 8 patients with hypergastrinemia and type 1 gNETs enrolled in a phase 2 trial of netazepide. Control samples were obtained from 10 patients without gastric cancer. We used amplified and biotinylated sense-strand DNA targets from total RNA and Affymetrix (Thermofisher Scientific, UK) Human Gene 2.0 ST microarrays to identify differentially expressed genes in stomach tissues from patients with type 1 gNETs before, during, and after netazepide treatment. Findings were validated in a human AGSGR gastric adenocarcinoma cell line that stably expresses human CCK2R, primary mouse gastroids, transgenic hypergastrinemic INS-GAS mice, and patient samples. RESULTS: Levels of pappalysin 2 (PAPPA2) messenger RNA were reduced significantly in gNET tissues from patients receiving netazepide therapy compared with tissues collected before therapy. PAPPA2 is a metalloproteinase that increases the bioavailability of insulin-like growth factor (IGF) by cleaving IGF binding proteins (IGFBPs). PAPPA2 expression was increased in the gastric corpus of patients with type 1 gNETs, and immunohistochemistry showed localization in the same vicinity as CCK2R-expressing enterochromaffin-like cells. Up-regulation of PAPPA2 also was found in the stomachs of INS-GAS mice. Gastrin increased PAPPA2 expression with time and in a dose-dependent manner in gastric AGSGR cells and mouse gastroids by activating CCK2R. Knockdown of PAPPA2 in AGSGR cells with small interfering RNAs significantly decreased their migratory response and tissue remodeling in response to gastrin. Gastrin altered the expression and cleavage of IGFBP3 and IGFBP5. CONCLUSIONS: In an analysis of human gNETS and mice, we found that gastrin up-regulates the expression of gastric PAPPA2. Increased PAPPA2 alters IGF bioavailability, cell migration, and tissue remodeling, which are involved in type 1 gNET development. These effects are inhibited by netazepide.

Designing antibodies for the inhibition of gastrin activity in tumoral cell lines.

Gastrin and its derivatives are becoming important targets for immunotherapy of pancreatic, gastric and colorectal tumors. This study was conducted to design antibodies able to block gastrin binding to the gastrin/cholecystokinin-2 (CCK-2) receptor in order to delay tumor growth. The authors have used different gastrin molecules, combined with the diphtheria toxoid, to generate and select human single chain variable fragments (scFvs) as well as mouse monoclonal antibodies and scFvs against different regions of gastrin. There was a remarkable conservation in the antibody repertoire against gastrin, independently of the approach and the species. The germlines most frequently used in gastrin antibody formation were identified. Three different epitopes were identified in the gastrin molecule. The resulting mouse monoclonal antibodies and scFvs were analyzed for gastrin neutralization using Colo 320 WT cells, which overexpress the CCK-2 receptor. The gastrin neutralizing activity assay showed that N-terminal specific mouse monoclonal antibodies were more efficient to inhibit proliferation of Colo 320 WT cells than the anti-C terminal antibodies. Moreover, the human antigastrin scFvs obtained in this study inhibited significantly the proliferation of Colo 320 tumoral cells. These findings should contribute to a more rational design of antibody-based antigastrin therapies in cancer, including passive administration of human antibodies with blocking activity.

Gastroprotective action of orexin-A against stress-induced gastric damage is mediated by endogenous prostaglandins, sensory afferent neuropeptides and nitric oxide.

Orexin-A, identified in the neurons and endocrine cells in the gut, has been implicated in control of food intake and sleep behavior but little is known about its influence on gastric secretion and mucosal integrity. The effects of orexin-A on gastric secretion and gastric lesions induced in rats by 3.5 h of water immersion and restraint stress (WRS) or 75% ethanol were determined. Orexin-A (5-80 microg/kg i.p.) increased gastric acid secretion and attenuated gastric lesions induced by WRS and this was accompanied by the significant rise in plasma orexin-A, CGRP and gastrin levels, the gastric mucosal blood flow (GBF), luminal NO concentration and an increase in mRNA for CGRP and overexpression of COX-2 protein and the generation of PGE(2) in the gastric mucosa. Orexin-A-induced protection was abolished by selective OX-1 receptor antagonist, vagotomy and attenuated by suppression of COX-1 and COX-2, deactivation of afferent nerves with neurotoxic dose of capsaicin, pretreatment with CCK(2)/gastrin antagonist, CGRP(8-37) or capsazepine and by inhibition of NOS with L-NNA. This study shows for the first time that orexin-A exerts a potent protective action on the stomach of rats exposed to non-topical ulcerogens such as WRS or topical noxious agents such as ethanol and these effects depend upon hyperemia mediated by COX-PG and NOS-NO systems, activation of vagal nerves and sensory neuropeptides such as CGRP released from sensory nerves probably triggered by an increase in gastric acid secretion induced by this peptide.

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.

Hormonal regulation of human lower esophageal sphincter competence: interaction of gastrin and secretin.

The interaction of gastrin and secretin, in the regulation of human lower esophageal sphincter competence, was studied in 54 normal subjects. A dose-response curve, for the lower esophageal sphincter, was constructed from the rapid intravenous injections of synthetic gastrin I (amino acid sequence 2-17). This curve was sigmoid shaped and showed a peak response that was 460.0 +/-24.0% (mean +/-2 SE) of the initial sphincter pressure, at a dose of 0.7 mug/kg of gastrin I. Secretin, either endogenously released by duodenal acidification, or exogenously administered as a single intravenous injection, markedly reduced the peak response of the sphincter to gastrin I. To ascertain the character of this inhibition, a gastrin I dose-response curve was obtained during a continuous intravenous secretin infusion. This curve showed a parallel shift to the right, with the maximal sphincter response to gastrin I still attainable at higher doses. A sphincter, endogenously stimulated by gastrin, showed a dose-related reduction in pressure with rapid intravenous injections of secretin. At the level of resting sphincter pressure, response to secretin diminished, and larger doses were required for comparable reduction in pressure. These studies indicate; (a) Secretin interacts with gastrin in the physiological regulation of human lower esophageal sphincter competence; (b) Secretin is a sensitive inhibitor to gastrin stimulation of the lower esophageal sphincter; (c) This inhibitory effect of secretin is competitive in character.

Specific inhibition by prostaglandins E2 and I2 of histamine-stimulated [14C]aminopyrine accumulation and cyclic adenosine monophosphate generation by isolated canine parietal cells.

The effects of prostaglandins E2 and I2 on accumulation of [14C]aminopyrine and the generation of cyclic AMP by fractions of dispersed canine gastric mucosal cells, enriched in their content of parietal cells, have been studied. The parietal cell content of the fractions was enriched to between 43 and 70% using an elutriator rotor. The accumulation of [14C]aminopyrine was used as the index of parietal cell response to stimulation. Prostaglandin E2 (PGE2, 0.1 nM-0.1 mM) inhibited histamine stimulated aminopyrine uptake but did not block the response to carbachol, gastrin, or dibuturyl cyclic AMP. PGE2 did, however, inhibit aminopyrine uptake stimulated by carbachol and gastrin when the response to these agents was potentiated by histamine. PGE2 (0.1 NM-0.1 mM) inhibited histamine-stimulated cyclic AMP production in a dose-dependent fashion with maximal inhibition at 1 microM PGE2. Prostacyclin also inhibited both histamine-stimulated aminopyrine accumulation and histamine-stimulated cyclic AMP production. In the absence of added histamine, PGE2 in concentrations above 1 microM and prostacyclin in concentrations above 10 microM stimulated cyclic AMP production, probably by acting on the nonparietal cells as shown in previous studies. These present data are consistent with the hypothesis that prostaglandins E2 and I2 inhibit the response of isolated parietal cells to histamine by specifically blocking histamine-stimulated cyclic AMP production.

The genesis of lower esophageal sphincter pressure: its identification through the use of gastrin antiserum.

The purpose of this study was to evaluate the role of gastrin in the genesis of lower esophageal sphincter (LES) pressure by the use of a high titer gastrin antiserum. Intravenous infusions of increasing amounts of rabbit gastrin antiserum, but not control antiserum, produced graded reductions in the resting LES pressure in anesthetized opossums. A maximal inhibition in LES pressure of 80.0+/-3.1% (mean +/-SE) was achieved when gastrin antiserum was administered in an amount estimated to bind almost all endogenous circulating gastrin in the opossum. Gastrin antiserum also inhibited the LES response to endogenous gastrin release (gastric deacidification) and to exogenous intravenous administration of gastrin I. The inhibition of the LES response to exogenous gastrin I by gastrin antiserum could be eliminated by giving excess gastrin I. Studies performed in vitro showed that gastrin antiserum inhibited the contractile response of LES circular muscle to gastrin I, but not to acetylcholine. These studies indicate that gastrin antiserum: (a) specifically antagonized the response of LES circular muscle to gastrin, in vitro; (b) diminished the LES response to the endogenous release and to the exogenous administration of gastrin; and (c) markedly reduced the resting level of LES pressure. We conclude that endogenous gastrin is the major determinant of resting LES pressure.

Targeting the Wnt Pathway and Cancer Stem Cells with Anti-progastrin Humanized Antibodies as a Potential Treatment for K-RAS-Mutated Colorectal Cancer.

Purpose: Patients with metastatic colorectal cancer suffer from disease relapse mainly due to cancer stem cells (CSC). Interestingly, they have an increased level of blood progastrin, a tumor-promoting peptide essential for the self-renewal of colon CSCs, which is also a direct ß-catenin/TCF4 target gene. In this study, we aimed to develop a novel targeted therapy to neutralize secreted progastrin to inhibit Wnt signaling, CSCs, and reduce relapses.Experimental Design: Antibodies (monoclonal and humanized) directed against progastrin were produced and selected for target specificity and affinity. After validation of their effectiveness on survival of colorectal cancer cell lines harboring B-RAF or K-RAS mutations, their efficacy was assessed in vitro and in vivo, alone or concomitantly with chemotherapy, on CSC self-renewal capacity, tumor recurrence, and Wnt signaling.Results: We show that anti-progastrin antibodies decrease self-renewal of CSCs both in vitro and in vivo, either alone or in combination with chemotherapy. Furthermore, migration and invasion of colorectal cancer cells are diminished; chemosensitivity is prolonged in SW620 and HT29 cells and posttreatment relapse is significantly delayed in T84 cells, xenografted nude mice. Finally, we show that the Wnt signaling activity in vitro is decreased, and, in transgenic mice developing Wnt-driven intestinal neoplasia, the tumor burden is alleviated, with an amplification of cell differentiation in the remaining tumors.Conclusions: Altogether, these data show that humanized anti-progastrin antibodies might represent a potential new treatment for K-RAS-mutated colorectal patients, for which there is a crucial unmet medical need. Clin Cancer Res; 23(17); 5267-80. ©2017 AACR.

Antiulcerogenic activity of Alchornea castaneaefolia: effects on somatostatin, gastrin and prostaglandin.

The hydroethanolic extract of the leaves (HEL) and bark (HEB) obtained from Alchornea castaneaefolia (Euphorbiaceae) were investigated for their ability to prevent ulceration of the gastric mucosa in animal models. HEL (500 and 1000 mg/kg) and HEB (1000 mg/kg) significantly reduced the gastric injuries induced by the combination of HCl/ethanol and lowered the severity of gastric damage formation induced by indomethacin/bethanechol in mice. Further investigation showed that HEL also inhibited formation of ulcers in mice submitted to stress and pylorus ligature, but HEL did not modify gastric juice parameters in Shay mice. HEL was also effective in promoting the healing process in chronic gastric ulcer induced by acetic acid in rats. An enriched flavonoidic fraction (EFF at dose of 100mg/kg) obtained from HEL reduced gastric lesions induced by HCl/ethanol and indomethacin/bethanechol in mice. Although EFF did not modify the amount of free mucus production by gastric mucosa, it was able to increase prostaglandin production. When administered to rats submitted to ethanol-induced gastric lesions, EFF increased the somatostatin serum levels, while the gastrin serum levels were proportionally decreased. Phytochemical investigation on HEL and EFF led to the isolation of flavonoids glycosides as the main compounds, thus suggesting that these substances may be involved in the observed antiulcer activity.

Antiproliferative effects of gastrin receptor antagonists and antibodies to gastrin on human colon carcinoma cell lines.

The gastrointestinal hormone gastrin has been shown to stimulate the growth of normal colonic mucosa. To examine for a possible role of gastrin in the proliferation of cultured colon tumor cells, we have studied the effects of two gastrin receptor antagonists, proglumide and benzotript, and of antibodies to gastrin. We find that proglumide (50% effective concentration, 2 to 5 mM) and benzotript (50% effective concentration, 0.4 to 0.8 mM) inhibit the monolayer growth of six human colon cancer cell lines. Addition of exogenous gastrin abrogated the growth-inhibitory effect of proglumide. The anchorage-independent growth of colon carcinoma cells was also inhibited by the two gastrin antagonists. Also, a dose-dependent increase in carcinoembryonic antigen secretion was observed upon treatment with proglumide and benzotript in three cell lines examined. Half-maximal inhibition of labeled gastrin binding was observed at concentrations of 0.4 mM benzotript and 8.6 mM proglumide. In addition, antigastrin antiserum added to HCT 116 cells adapted to growth in serum-free medium resulted in a concentration-dependent inhibition of cellular proliferation. These data suggest that gastrin may function as an autocrine growth factor in colon carcinoma.

Gastrin stimulates Ca2+ mobilization and clonal growth in small cell lung cancer cells.

Gastrin has been postulated to be a physiological growth factor, but compelling in vitro evidence of this has been difficult to obtain. In the present study we investigated whether small cell lung carcinoma cell lines could provide a useful model system to study the effects of gastrin on signal transduction and cell proliferation in vitro. We found that the addition of gastrin to small cell lung cancer cells loaded with the fluorescent Ca2+ indicator fura 2-tetraacetoxymethylester causes a rapid and transient increase in the intracellular concentration of Ca2+ ([Ca2+]i) followed by homologous desensitization. The [Ca2+]i response was especially prominent in the small cell lung carcinoma cell line H510. In this cell line, gastrin I, gastrin II, cholecystokinin residues 26-33 (CCK-8), and unsulfated CCK-8 increased [Ca2+]i in a concentration-dependent fashion with half-maximum effects at 7, 2.5, 3, and 5 nM, respectively. The Ca(2+)-mobilizing effects of gastrin and CCK-8 were prevented by proglumide, benzotript, and the specific gastrin/CCKB receptor antagonist L365260. Gastrin stimulated the clonal growth of H510 cells in semisolid (agarose-containing) medium, increasing both the number and the size of the colonies. Gastrin and CCK agonists were equally effective in promoting clonal growth. The broad-spectrum neuropeptide antagonists [D-Arg1,D-Phe5,D-Trp7,9,Leu11] substance P and [Arg6,D-Trp7,9,MePhe8] substance P (6-11) markedly inhibited gastrin-stimulated Ca2+ mobilization and clonal growth. These results show that gastrin acts as a direct growth factor through gastrin/CCKB receptors and demonstrate, for the first time, that these peptides can stimulate the proliferation of cells outside the gastrointestinal tract.

GATA proteins are potential negative regulators of HDC gene expression in the gastric epithelium.

In this study, we used the gastric epithelial cell line AGS-G(R) to investigate the role of GATA transcription factors in the regulation of both basal and gastrin-stimulated L-histidine decarboxylase (HDC) gene transcription. Using reporter gene technology, we compared the transcriptional activity of a construct, hHDC503, which contained the 5'-flanking region of the human HDC gene with that of similar constructs lacking selected GATA consensus sequences. We demonstrated the expression of GATA-4 and GATA-6 proteins within the AGS-G(R) cells and found evidence that these transcription factors can negatively regulate HDC gene expression.

Phase I/II study of G17-DT, an anti-gastrin immunogen, in advanced colorectal cancer.

Gastrin is a growth factor for colorectal cancer, and therefore, anti-gastrin hormone therapy has a potential role in treatment of this disease. The gastrin immunogen gastrin-17-diphtheria toxoid (G17-DT; Gastrimmune) produces anti-G17 antibodies that have been shown to be effective in the treatment of colorectal carcinoma in preclinical models. Fifty patients with advanced colorectal cancer were treated with G17-DT in a multicenter, sequential group, open label Phase I/II study. Primary injections with two booster doses were given by i.m. injection. The main aim of the study was to assess the safety and efficacy of the production of antigastrin antibodies. Locally developed and standard WHO toxicity measurements with RIA and Scatchard analysis for antibody assessment were used. One center measured tumor response radiologically. Eighty % of patients produced a measurable antibody response. Antibodies of high affinity (median Kd, 0.295 nM; interquartile range, 0.16-0.41 nM) were detected between 4 and 12 weeks after primary injection. The antigen binding capacity was high at 2.8 x 10(-9) M (interquartile range, 5.1 x 10(-10) to 7.25 x 10(-9) M). The treatment was well tolerated with no systemic side effects seen. Myalgia at the injection site was seen in 46% of patients with severe pain caused by the formation of a sterile abscess seen in 14% of patients. The abscesses were all drained under ultrasound guidance, and the patients recovered fully within 6 weeks. No radiological responses were seen, but two patients had stable disease. G17-DT immunization produces anti-G17 antibodies in patients with advanced colorectal cancer. The antibodies were of an affinity high enough to compete with the cholecystokinin B/gastrin receptor for G17 binding with adequate capacity to neutralize postprandial gastrin surges. Additional dose-ranging studies have been performed in patients with gastric cancer using 100- and 200-microg doses of G17-DT formulated without adjuvant and the emulsifier aluminum monostearate. In addition, the effect of immunizing at different time intervals has been determined.

[A study of gastrin-focal adhesion kinase signal pathway in human colon cancer cells].

OBJECTIVE: The study investigated the effect of gastrin on tyrosine phosphorylation and protein expression of focal adhesion kinase (FAK) in human colon cancer cells. METHODS: The eukaryotic plasmid that expresses cholecystokinin 2 receptor (CCK2R) stably, named pCR3.1/CCK2R, was transfected into Colo320 to construct an up-regulated gastrin-CCK2R signal pathway; the gastrin antagonist was used to down-regulate the signal pathway. Thus, including the normal control, there were three signal pathways with different CCK2R levels. Different doses of gastrin were used to stimulate FAK in the different time. FAK tyrosine phosphorylation and FAK expression in different groups were detected by immunoprecipitation and Western-blotting assays, and analyzed with Labimage software. RESULTS: RT-PCR result showed that Colo320 transfected with CCK2R had a mRNA level four times higher than that normal Colo320 did, and which suggested that up-regulated signal transduction pathway was constructed. After stimulated by gastrin with 0, 0.1, 1, 10 and 100 nmol/L, tyrosine phosphorylation levels of Colo320 were 24.0%, 39.7%, 46.2%, 50.4% and 44.5%, and those of Colo320 transfected with CCK2R were 24.6%, 70.7%, 90.1%, 100% and 88.6%. When incubated with gastrin at 0, 2.5, 5, 10 and 20 min, the tyrosine phosphorylation levels of Colo320 were 23.9%, 63.6%, 58.6%, 45.5% and 40.9%, and those of Colo320 transfected with CCK2R were 24.5%, 84.6%, 100%, 98.6% and 97.9%. The increases of tyrosine phosphorylation in both Colo320 and Colo320 transfected with CCK2R were dose dependence of gastrin. In Colo320, the time of phosphorylation had a tendency of exhaustion at 2.5 min; but in Colo320 transfected with CCK2R, it was at 10 min. Gastrin had no effects on FAK protein expression in different cell groups. An up-regulated level of CCK2R could enhance the effect of gastrin on FAK tyrosine phosphorylation. The gastrin antagonist showed an effect of competitive inhibition on tyrosine phosphorylation of FAK. CONCLUSIONS: FAK is a signal transducer in downstream of CCK(2)R; FAK exerts its functions by tyrosine phosphorylation, but dose not increase FAK protein. Gastrin-CCK2R-FAK signal pathway is a pivotal one in the cell growth and proliferation caused by gastrin.

Role of proton pump inhibitors in preventing hypergastrinemia-associated carcinogenesis and in antagonizing the trophic effect of gastrin.

Gastrin is the main hormone stimulating gastric acid secretion, but it exerts proliferative and anti-apoptotic actions on various cancer cell types, in addition to its well-known trophic effect on enterochromaffin-like cells. As treatment with proton pump inhibitors (PPIs) increases the biosynthesis and secretion of gastrin, it has been postulated that treatment with PPIs could increase the risk of cancer, especially in Barrett's esophagus, gastric carcinoids, and colorectal cancer (CRC). Some tumors produce gastrin of their own, which can act in an autocrine manner to promote tumor growth. In addition, gastrin is known to foster the tumor microenvironment. However, in spite of these potentially increased cancer risks due to PPI-induced hypergastrinemia, prospective, large-scale cohort studies did not show an increase in CRC prevalence. The question as to why the long-term use of PPIs was not associated with an increased cancer risk of CRC might be answered by the fact that the PPIs antagonized the trophic effects of hypergastrinemia. Furthermore, the blockade of proton pumps or potassium channels in cancer cells could limit the abnormal glycolytic energy metabolism of cancer cells. Apart from their suppressive effect on gastric acids, PPIs exert an anti-tumor effect through the selective induction of apoptosis as well as an anti-inflammatory effect, and they protect cells from developing chemo- or radiotherapeutic resistance. Moreover, the anti-carcinogenic actions of PPIs were augmented with PPI-induced hypergastrinemia. Together with their potential targeted killing of cancer stem cells, these effects demonstrate their potential anti-cancer actions.

Inhibition of gastrin-stimulated growth of gastrointestinal tumour cells by octreotide and the gastrin/cholecystokinin receptor antagonists, proglumide and lorglumide.

The rat pancreatic cell line, AR42J possessed high-affinity gastrin and somatostatin receptors and its growth was stimulated by physiological gastrin-17 concentrations between 5 x 10(-11) mol/l and 10(-9) mol/l as measured by [75Se]selenomethionine uptake. The somatostatin analogue, octreotide (2 x 10(-7) to 2 x 10(-11) mol/l), reduced this stimulated growth. Gastrin-stimulated AR42J growth was also inhibited by proglumide (3 x 10(-4) mol/l) and lorglumide (3 x 10(-5) mol/l) at maximal G17 concentrations of 5 x 10(-11) and 10(-10) mol/l, respectively, and the analogues competed with [125I] gastrin-17 (5 x 10(-10) mol/l) for binding to gastrin receptors on AR42J (50% inhibitory concentrations, less than or equal to 10(-3) mol/l and 4 x 10(-6) mol/l, respectively. Octreotide reduced the basal growth of the human gastric cell line, MKN45G, (which is associated with intracellular gastrin immunoreactivity) in serum-free medium to 73% of control at a concentration of 2 x 10(-8) mol/l, which was reversed by gastrin-17 (10(-10) mol/l). Lorglumide (3 x 10(-5) mol/l) also reduced the basal growth to 30% of control, which was reversed to 78% by 10(-5) mol/l gastrin. Proglumide had no effect on the basal growth of MKN45G.