Gastrin promotes human colon cancer cell growth via CCK-2 receptor-mediated cyclooxygenase-2 induction and prostaglandin E2 production

The relationship of serum gastrin-17 and oral mucositis in head and neck carcinoma patients receiving radiotherapy

OBJECTIVE

The aim of this study was to analyze the relationship of serum gastrin-17 (G-17) and oral mucositis in head and neck carcinoma (HNC) patients receiving radiotherapy.

METHODS

Serum G-17 were detected in patients before and after radiotherapy. Patients were divided into high G-17 group (baseline serum G-17 ≥ 5pmol/L) and low G-17 group (baseline serum G-17 < 5pmol/L). The severity of oral mucositis was analyzed between the two groups. Other complications such as dysphagia, salivary gland, mandible, thyroid function, larynx, pain, and weight loss were also investigated.

RESULTS

Forty-two patients were analyzed in this study. The level of serum G-17 had a significant decrease after radiotherapy (7.29 ± 5.70pmol/L versus 4.93 ± 4.46pmol/L, P = 0.038). In low serum G-17 group, the incidences of grade 0, 1-2 and 3-4 of oral mucositis were 0%, 30.4%, and 69.6%, respectively. In high serum G-17 group, the incidences of grade 0, 1-2 and 3-4 of oral mucositis were 0%, 63.2%, and 36.8%, respectively. Pearson correlation analysis showed that serum G-17 was negatively correlated with oral mucositis (r=-0.595, P < 0.01). Weight loss of low G-17 group was more serious than that of high G-17 group.

CONCLUSION

Serum G-17 has a close relationship with oral mucositis. Baseline serum G-17 may be a potential predictor for the severity of oral mucositis in HNC patients receiving radiotherapy.

The hyperthermic effect of central cholecystokinin is mediated by the cyclooxygenase-2 pathway

Cholecystokinin (CCK) increases core body temperature via CCK₂ receptors when administered intracerebroventricularly (icv). The mechanisms of CCK-induced hyperthermia are unknown, and it is also unknown whether CCK contributes to the fever response to systemic inflammation. We studied the interaction between central CCK signaling and the cyclooxygenase (COX) pathway. Body temperature was measured in adult male Wistar rats pretreated with intraperitoneal infusion of the nonselective COX enzyme inhibitor metamizol (120 mg/kg) or a selective COX-2 inhibitor, meloxicam, or etoricoxib (10 mg/kg for both) and, 30 min later, treated with intracerebroventricular CCK (1.7 µg/kg). In separate experiments, CCK-induced neuronal activation (with and without COX inhibition) was studied in thermoregulation- and feeding-related nuclei with c-Fos immunohistochemistry. CCK increased body temperature by ∼0.4°C from 10 min postinfusion, which was attenuated by metamizol. CCK reduced the number of c-Fos-positive cells in the median preoptic area (by ∼70%) but increased it in the dorsal hypothalamic area and in the rostral raphe pallidus (by ∼50% in both); all these changes were completely blocked with metamizol. In contrast, CCK-induced satiety and neuronal activation in the ventromedial hypothalamus were not influenced by metamizol. CCK-induced hyperthermia was also completely blocked with both selective COX-2 inhibitors studied. Finally, the CCK₂ receptor antagonist YM022 (10 µg/kg icv) attenuated the late phases of fever induced by bacterial lipopolysaccharide (10 µg/kg; intravenously). We conclude that centrally administered CCK causes hyperthermia through changes in the activity of "classical" thermoeffector pathways and that the activation of COX-2 is required for the development of this response.NEW & NOTEWORTHY An association between central cholecystokinin signaling and the cyclooxygenase-prostaglandin E pathway has been proposed but remained poorly understood. We show that the hyperthermic response to the central administration of cholecystokinin alters the neuronal activity within efferent thermoeffector pathways and that these effects are fully blocked by the inhibition of cyclooxygenase. We also show that the activation of cyclooxygenase-2 is required for the hyperthermic effect of cholecystokinin and that cholecystokinin is a modulator of endotoxin-induced fever.

Proton pump inhibitors and colorectal cancer: A systematic review

BACKGROUND

The use of proton pump inhibitors (PPI) is common worldwide, with reports suggesting that they may be overused. Several studies have found that PPI may affect colorectal cancer (CRC) risk.

AIM

To summarize current knowledge on the relationship between PPI and CRC from basic research, epidemiological and clinical studies.

METHODS

This systematic review was based on the patients, interventions, comparisons, outcome models and performed according to PRISMA guidelines. MEDLINE, EMBASE, Scopus, and Web of Science databases were searched from inception until May 17, 2021. The initial search returned 2591 articles, of which, 28 studies met the inclusion criteria for this review. The studies were categorized as basic research studies (n = 12), epidemiological studies (n = 11), and CRC treatment studies (n = 5). The quality of the included studies was assessed using the Newcastle-Ottawa Scale or Cochrane Risk of Bias 2.0 tool depending on the study design.

RESULTS

Data from basic research indicates that PPI do not stimulate CRC development via the trophic effect of gastrin but instead may paradoxically inhibit it. These studies also suggest that PPI may have properties beneficial for CRC treatment. PPI appear to have anti-tumor properties (omeprazole, pantoprazole), and are potential T lymphokine-activated killer cell-originated protein kinase inhibitors (pantoprazole, ilaprazole), and chemosensitizing agents (pantoprazole). However, these mechanisms have not been confirmed in human trials. Current epidemiological studies suggest that there is no causal association between PPI use and increased CRC risk. Treatment studies show that concomitant PPI and capecitabine use may reduce the efficacy of chemotherapy resulting in poorer oncological outcomes, while also suggesting that pantoprazole may have a chemosensitizing effect with the fluorouracil, leucovorin, oxaliplatin (FOLFOX) regimen.

CONCLUSION

An unexpected inhibitory effect of PPI on CRC carcinogenesis by way of several potential mechanisms is noted. This review identifies that different PPI agents may have differential effects on CRC treatment, with practical implications. Prospective studies are warranted to delineate this relationship and assess the role of individual PPI agents.

Proton pump inhibitors and survival in patients with colorectal cancer: a Swedish population-based cohort study

BACKGROUND

Proton pump inhibitors (PPIs) are associated with microbiome changes of the gut, which in turn may affect the progression of colorectal cancer (CRC). This study aims to assess the associations between PPI use and all-cause and CRC-specific mortality.

METHODS

We selected all patients registered in the Swedish Prescribed Drug Registry who were diagnosed with CRC between 2006 and 2012 (N = 32,411, 54.9% PPI users) and subsequently followed them through register linkage to the Swedish Causes of Death Registry until December 2013. PPI users were patients with ≥1 post-diagnosis PPI dispensation. Time-dependent Cox-regression models were performed with PPI use as time-varying exposure.

RESULTS

Overall 4746 (14.0%) patients died, with an aHR of 1.38 (95% CI 1.32-1.44) for all-cause mortality comparing PPI users with PPI nonusers. Higher-magnitude associations were observed among male, cancer stage 0-I, rectal cancer and patients receiving CRC surgery. The PPI-all-cause mortality association was also more pronounced comparing new users to non-users (aHR = 1.47, 95%CI 1.40-1.55) than comparing continuous users to non-users (aHR = 1.32, 95%CI 1.24-1.39). The risk estimates for CRC-specific mortality comparing PPI users to PPI nonusers were similar to those for all-cause mortality.

CONCLUSION

PPI use after the CRC diagnosis was associated with increased all-cause and CRC-specific mortality.

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.

Gastric Peptides-Gastrin and Somatostatin

Gastric acid secretion (i) facilitates digestion of protein as well as absorption of micronutrients and certain medications, (ii) kills ingested microorganisms, including Helicobacter pylori, and (iii) prevents bacterial overgrowth and enteric infection. The principal regulators of acid secretion are the gastric peptides gastrin and somatostatin. Gastrin, the major hormonal stimulant for acid secretion, is synthesized in pyloric mucosal G cells as a 101-amino acid precursor (preprogastrin) that is processed to yield biologically active amidated gastrin-17 and gastrin-34. The C-terminal active site of gastrin (Trp-Met-Asp-Phe-NH₂ ) binds to gastrin/CCK₂ receptors on parietal and, more importantly, histamine-containing enterochromaffin-like (ECL) cells, located in oxyntic mucosa, to induce acid secretion. Histamine diffuses to the neighboring parietal cells where it binds to histamine H₂ -receptors coupled to hydrochloric acid secretion. Gastrin is also a trophic hormone that maintains the integrity of gastric mucosa, induces proliferation of parietal and ECL cells, and is thought to play a role in carcinogenesis. Somatostatin, present in D cells of the gastric pyloric and oxyntic mucosa, is the main inhibitor of acid secretion, particularly during the interdigestive period. Somatostatin exerts a tonic paracrine restraint on gastrin secretion from G cells, histamine secretion from ECL cells, and acid secretion from parietal cells. Removal of this restraint, for example by activation of cholinergic neurons during ingestion of food, initiates and maximizes acid secretion. Knowledge regarding the structure and function of gastrin, somatostatin, and their respective receptors is providing novel avenues to better diagnose and manage acid-peptic disorders and certain cancers. Published 2020. Compr Physiol 10:197-228, 2020.

Transcriptomics analysis reveals new insights in E171-induced molecular alterations in a mouse model of colon cancer

Titanium dioxide as a food additive (E171) has been demonstrated to facilitate growth of chemically induced colorectal tumours in vivo and induce transcriptomic changes suggestive of an immune system impairment and cancer development. The present study aimed to investigate the molecular mechanisms behind the tumour stimulatory effects of E171 in combination with azoxymethane (AOM)/dextran sodium sulphate (DSS) and compare these results to a recent study performed under the same conditions with E171 only. BALB/c mice underwent exposure to 5 mg/kg_bw/day of E171 by gavage for 2, 7, 14, and 21 days. Whole genome mRNA microarray analyses on the distal colon were performed. The results show that E171 induced a downregulation of genes involved in the innate and adaptive immune system, suggesting impairment of this system. In addition, over time, signalling genes involved in colorectal cancer and other types of cancers were modulated. In relation to cancer development, effects potentially associated with oxidative stress were observed through modulation of genes related to antioxidant production. E171 affected genes involved in biotransformation of xenobiotics which can form reactive intermediates resulting in toxicological effects. These transcriptomics data reflect the early biological responses induced by E171 which precede tumour formation in an AOM/DSS mouse model.

Advantages and Disadvantages of Long-term Proton Pump Inhibitor Use

Proton pump inhibitors (PPIs) potently inhibit gastric acid secretion and are widely used for treatment of acid-related diseases including gastroesophageal reflux disease and secondary prevention of aspirin/NSAID-induced ulcers. Although clinically important adverse effects of PPIs can occur, just as with other drugs, those are not frequently observed during or after administration. Thus, PPIs are regarded as relatively safe and considered to be clinically beneficial. Recently, PPIs have become frequently administered to patients with functional gastrointestinal diseases or primary prevention of drug-related gastroduodenal damage, even though their beneficial effects for those conditions have not been fully confirmed. PPIs tend to be given for conditions in which the necessity of the drug has not been clarified, thus otherwise rare adverse effects are presented as clinically relevant. Although several PPI-related adverse effects have been reported, their clinical relevance is not yet clear, since the evidence reported in those studies is not at a high enough level, as the majority are based on retrospective observational studies and the reported hazard ratios are low. It is important to administer PPIs only for patients who will gain a substantial clinical benefit and to continue to investigate their adverse effects with high quality prospective studies.

Activation of muscarinic receptors prevents TNF-α-mediated intestinal epithelial barrier disruption through p38 MAPK

Intestinal epithelial cells form a tight barrier to act as selective physical barriers, repelling hostile substances. Tumor necrosis factor-α (TNF-α) is a well characterized pro-inflammatory cytokine which can compromise intestinal barrier function and the suppression of TNF-α function is important for treatment of inflammatory bowel disease (IBD). In this study, we investigated the contribution of G-protein-coupled receptor (GPCR)-induced signalling pathways to the maintenance of epithelial barrier function. We first demonstrated the existence of functional muscarinic M3 and histamine H1 receptors in colonic epithelial cell HT-29/B6. As we previously reported, muscarinic M3 receptor prevented TNF-α-induced barrier disruption through acceleration of TNF receptor (TNFR) shedding which is carried out by TNF-α converting enzyme (TACE). M3 receptor-mediated suppression of TNF-α function depends on Gα_q/11 protein, however, histamine H1 receptor could not ameliorate TNF-α function, while which could induce Gα_q/11 dependent intracellular Ca²⁺ mobilization. We found that p38 MAPK was predominantly phosphorylated by M3 receptor through Gα_q/11 protein, whereas H1 receptor barely upregulated the phosphorylation. Inhibition of p38 MAPK abolished M3 receptor-mediated TNFR shedding and suppression of TNF-α-induced NF-κB signalling. The p38 MAPK was also involved in TACE- mediated EGFR transactivation followed by ERK1/2 phosphorylation. These results indicate that not H1 but M3 receptor-induced activation of p38 MAPK might contribute to the maintenance of epithelial barrier function through down-regulation of TNF-α signalling and activation of EGFR.

A retrospective analysis of the role of proton pump inhibitors in colorectal cancer disease survival

BACKGROUND

Proton pump inhibitors (ppis) are a commonly used medication. A limited number of studies have identified a weak-to-moderate association between ppi use and colorectal cancer (crc) risk, but none to date have identified an effect of ppi use on crc survival. We therefore postulated that an association between ppi use and crc survival might potentially exist.

METHODS

We performed a retrospective chart review of 1304 crc patients diagnosed from January 2005 to December 2011 and treated at the Cancer Centre of Southeastern Ontario. Kaplan-Meier analysis and Cox proportional hazards regression models were used to evaluate overall survival (os).

RESULTS

We identified 117 patients (9.0%) who were taking ppis at the time of oncology consult. Those taking a ppi were also more often taking asa or statins (or both) and had a statistically significantly increased rate of cardiac disease. No identifiable difference in tumour characteristics was evident in the two groups, including tumour location, differentiation, lymph node status, and stage. Univariate analysis identified a statistically nonsignificant difference in survival, with those taking a ppi experiencing lesser 1-year (82.1% vs. 86.7%, p = 0.161), 2-year (70.1% vs. 76.8%, p = 0.111), and 5-year os (55.2% vs. 62.9%, p = 0.165). When controlling for patient demographics and tumour characteristics, multivariate Cox regression analysis identified a statistically significant effect of ppi in our patient population (hazard ratio: 1.343; 95% confidence interval: 1.011 to 1.785; p = 0.042).

CONCLUSIONS

Our results suggest a potential adverse effect of ppi use on os in crc patients. These results need further evaluation in prospective analyses.

Cholecystokinin-1 receptor antagonists: 5-hydroxy-5-aryl-pyrrol-2-ones as anticancer agents

Hydroxy-pyrrolones, which were potent CCK1R antagonists, showed nanomolar in vitro activity and anticancer activity in vivo for colon and pancreatic cancer.

In silico discovery of significant pathways in colorectal cancer metastasis using a two-stage optimisation approach

Accurate and reliable modelling of protein-protein interaction networks for complex diseases such as colorectal cancer can help better understand mechanism of diseases and potentially discover new drugs. Different machine learning methods such as empirical mode decomposition combined with least square support vector machine, and discrete Fourier transform have been widely utilised as a classifier and for automatic discovery of biomarkers for the diagnosis of the disease. The existing methods are, however, less efficient as they tend to ignore interaction with the classifier. In this study, the authors propose a two-stage optimisation approach to effectively select biomarkers and discover interactions among them. At the first stage, particle swarm optimisation (PSO) and differential evolution (DE) are used to optimise parameters of support vector machine recursive feature elimination algorithm, and dynamic Bayesian network is then used to predict temporal relationship between biomarkers across two time points. Results show that 18 and 25 biomarkers selected by PSO and DE-based approach, respectively, yields the same accuracy of 97.3% and F1-score of 97.7 and 97.6%, respectively. The stratified analysis reveals that Alpha-2-HS-glycoprotein was a dominant hub gene with multiple interactions to other genes including Fibrinogen alpha chain, which is also a potential biomarker for colorectal cancer.

CI-988 Inhibits EGFR Transactivation and Proliferation Caused by Addition of CCK/Gastrin to Lung Cancer Cells

Cholecystokinin (CCK) receptors are G-protein coupled receptors (GPCR) which are present on lung cancer cells. CCK-8 stimulates the proliferation of lung cancer cells, whereas the CCK2R receptor antagonist CI-988 inhibits proliferation. GPCR for some gastrointestinal hormones/neurotransmitters mediate lung cancer growth by causing epidermal growth factor receptor (EGFR) transactivation. Here, the role of CCK/gastrin and CI-988 on EGFR transactivation and lung cancer proliferation was investigated. Addition of CCK-8 or gastrin-17 (100 nM) to NCI-H727 human lung cancer cells increased EGFR Tyr(1068) phosphorylation after 2 min. The ability of CCK-8 to cause EGFR tyrosine phosphorylation was blocked by CI-988, gefitinib (EGFR tyrosine kinase inhibitor), PP2 (Src inhibitor), GM6001 (matrix metalloprotease inhibitor), and tiron (superoxide scavenger). CCK-8 nonsulfated and gastrin-17 caused EGFR transactivation and bound with high affinity to NCI-H727 cells, suggesting that the CCK2R is present. CI-988 inhibited the ability of CCK-8 to cause ERK phosphorylation and elevate cytosolic Ca(2+). CI-988 or gefitinib inhibited the basal growth of NCI-H727 cells or that stimulated by CCK-8. The results indicate that CCK/gastrin may increase lung cancer proliferation in an EGFR-dependent manner.

Paradoxically augmented anti-tumorigenic action of proton pump inhibitor and GastrininAPCMin/+ intestinal polyposis model

Though long-term administration of proton pump inhibitor (PPI) imposed the risk of gastrointestinal track tumorigenesis by accompanied hypergastrinemia, no overt increases of colon cancer risk were witnessed after a long-term cohort study. Our recent investigation revealed that PPI prevented colitis-associated carcinogenesis through anti-inflammatory, anti-oxidative, and anti-mutagenic mechanisms in spite of hypergastrinemia. Therefore, we hypothesized that PPI might either antagonize the trophic action of gastrin on gastrointestinal tumorigenesis or synergize to exert augmented anti-tumorigenic actions. We challenged APCMin/+ mice with gastrin, PPI, PPI and gastrin together for 10 weeks and counted intestinal polyposis accompanied with molecular changes. Gastrin significantly increased intestinal polyposis, but combination of PPI and gastrin markedly attenuated intestinal polyposis compared to gastrin-promoted APCMin/+ mice (P<.001), in which significant β-catenin phosphorylation and inhibition of β-catenin nuclear translocation were observed with PPI alone or combination of PPI and gastrin, whereas gastrin treatment significantly increased β-catenin nuclear translocation. Significant footprints of apoptosis, G0/G1 accumulation, inactivation of p38 and extracellular signal-regulated kinase, decreased expressions of CD31, and inhibition of tumor necrosis factor-α and cyclooxygenase-2 were noted in the combination group. In vitro investigations were similar to in vivo findings as shown that PPI treatment inhibited the binding of gastrin to its receptor, inactivated β-catenin-associated signaling including Tcf/Lef and glycogen synthase kinase β, and paradoxically inhibited β-catenin-associated proliferative activities. Our investigations explain why colon cancer risk has not increased despite long-term use of PPIs and provide a rationale for using PPI to achieve anti-tumorigenesis beyond acid suppression.

Opioids, Neutral Endopeptidase, its Inhibitors and Cancer: Is There a Relationship among them?

The role of endogenous animal opioids in the biology of cancer is widely recognized but poorly understood. This is, among others, because of the short half-life of these peptides, which are quickly inactivated by endopeptidases, e.g., neutral endopeptidase (NEP, CD10). It has been established that NEP is engaged in the modulation of the tumor microenvironment, among others that of colon cancer, by exerting influence on cell growth factors, the extracellular matrix and other biologically active substances. Although there are some discrepancies among the findings on the role of both opioids and NEP in cancer development, authors agree that their role seems to depend on the origin, stage and grade of tumor, and even on the method of examination. Moreover, recently, natural inhibitors of NEP, such as sialorphin, opiorphin and spinorphin have been detected. Their analgesic activity has been established. It is interesting to ask whether there is a relationship among opioid peptides, tumor-associated NEP and its inhibitors.

Helicobacter pylori seropositivity is positively associated with colorectal neoplasms

BACKGROUND/AIMS

Helicobacter pylori is a well known precursor to gastric cancer and gastric mucosa-associated lymphoid tissue lymphoma. This study was to determine whether H. pylori was associated with colorectal neoplasms in Korean subjects undergoing routine checkup.

METHODS

A total of 10,082 subjects underwent routine checkups from January 2004 to April 2005. A H. pylori IgG test and stool occult blood test were included in the routine checkup program. Colonoscopy was performed if the stool occult blood test was positive or under subject request. Patients who underwent colonoscopy and had histologically confirmed cases of colorectal neoplasms were designanted as the subject group and those without as the control group.

RESULTS

Of the 10,082 subjects, 597 had full colonoscopy. The results identified 9 colorectal carcinomas and 118 adenomas. H. pylori seropositivity was identified in 6 (66%) subjects with colorectal carcinoma, 81 (68.6%) with colorectal adenoma and 248 (52.8%) controls. Subjects having colorectal neoplasms had a significantly higher H. pylori seropositivity rate compared with the controls (OR 1.94, 95% CI 1.28-2.95). This remained significant after adjusting for age, sex, body mass index, HbA1c and total cholesterol (OR 1.90, 95% CI 1.23-2.93). Patients with distal neoplasms also had a significantly higher H. pylori seroposivity rate (OR 1.88, 95% CI 1.17-3.01) which persisted after multivariate adjustment (OR 1.79, 95% CI 1.10-2.94).

CONCLUSIONS

Subjects with colorectal neoplasms present an increased H. pylori seroprevalence compared with controls.

MiR-148a regulates the growth and apoptosis in pancreatic cancer by targeting CCKBR and Bcl-2

Our previous studies have revealed that miR-148a is downregulated in pancreatic cancer. Bioinformatics analysis has shown cholecystokinin-B receptor (CCKBR) and B cell lymphoma (Bcl-2) to be potential targets of miR-148a. But the pathophysiologic role of miR-148a and its relevance to the growth and development of pancreatic cancer are yet to be investigated. The purpose of this study is to elucidate the molecular mechanisms where miR-148a acts as a tumor suppressor in pancreatic cancer. Our results showed significant downregulation of miR-148a in 28 pancreatic cancer tissue samples and five pancreatic cancer cell lines, compared with their non-tumor counterparts by qRT-PCR. MiR-148a was found to not only inhibit the proliferation of pancreatic cancer cells (PANC-1 and AsPC-1) in vitro by MTT assay and colony formation assay, but also to promote cells apoptosis in vitro by Annexin V-FITC apoptosis detection and caspase activity assay. Using western blot and luciferase activity assay, CCKBR and Bcl-2 were identified as targets of miR-148a. Moreover, we also found that the expression of Bcl-2 lacking in 3'UTR could abrogate the pro-apoptosis function of miR-148a. These findings suggest the importance of miR-148a's targeting of CCKBR and Bcl-2 in the regulation of pancreatic cancer growth and apoptosis.

Gastrin acting on the cholecystokinin2 receptor induces cyclooxygenase-2 expression through JAK2/STAT3/PI3K/Akt pathway in human gastric cancer cells

Gastrin, cholecystokinin2 receptor (CCK2R), and cyclooxygenase-2 (COX-2) have been implicated in the carcinogenesis and progression of gastric cancer. Our study demonstrated that antagonist or siRNA against CCK2R blocked amidated gastrin (G17)-induced activation of STAT3 and Akt in gastric cancer cell lines. G17-increased COX-2 expression and cell proliferation were effectively blocked by CCK2R antagonist and inhibitors of JAK2 and PI3K. In addition, knockdown of STAT3 expression significantly attenuated G17-induced PI3K/Akt activation, COX-2 expression, and cell proliferation. These results suggest that CCK2R-mediated COX-2 up-regulation via JAK2/STAT3/PI3K/Akt pathway is involved in the proliferative effect of G17 on human gastric cancer cells.

Identification of novel amino acid derived CCK-2R antagonists as potential antiulcer agent: homology modeling, design, synthesis, and pharmacology

The present study revisited the three-dimensional (3D) homology model of CCK-2R using human A(2a) adenosine receptor and the resolved NMR based structure of the third extracellular loop of the CCK-2R as templates. Further in order to identify novel antiulcer agents, rational designing have been performed utilizing the substructure of a well-known CCK-2R antagonist benzotript as a lead molecule and submitted to the combined docking and simulation studies. This led to the understanding of the essential structure requirement as well as variation of binding mode among conformational isomers of small molecule CCK-2R antagonists. In the next step, preparation of each configurational isomer of these molecules was carried out and submitted for their in vitro activity followed by in vivo screening into antiulcer rat model. The biological screening of these compounds has not only validated the developed homology model of CCK-2R but also led to the identification of highly potent CCK-2R antagonist 6a as an orally active and safe candidate molecule having better antiulcer properties than the well-known drug benzotript.

Role of gastrin-peptides in Barrett's and colorectal carcinogenesis

Gastrin is the main hormone responsible for the stimulation of gastric acid secretion; in addition, gastrin and its derivatives exert proliferative and antiapoptotic effects on several cell types. Gastrin synthesis and secretion are increased in certain situations, for example, when proton pump inhibitors are used. The impact of sustained hypergastrinemia is currently being investigated. In vitro experiments and animal models have shown that prolonged hypergastrinemia may be related with higher cancer rates; although, this relationship is less clear in human beings. Higher gastrin levels have been shown to cause hyperplasia of several cell types; yet, the risk for developing cancer seems to be the same in normo- and hypergastrinemic patients. Some tumors also produce their own gastrin, which can act in an autocrine manner promoting tumor growth. Certain cancers are extremely dependent on gastrin to proliferate. Initial research focused only on the effects of amidated gastrins, but there has been an interest in intermediates of gastrin in the last few decades. These intermediates aren’t biologically inactive; in fact, they may exert greater effects on proliferation and apoptosis than the completely processed forms. In certain gastrin overproduction states, they are the most abundant gastrin peptides secreted. The purpose of this review is to examine the gastrin biosynthesis process and to summarize the results from different studies evaluating the production, levels, and effects of the main forms of gastrin in different overexpression states and their possible relationship with Barrett’s and colorectal carcinogenesis.

Helicobacter pylori infection increases the risk of colorectal adenomas: cross-sectional study and meta-analysis

BACKGROUND

The studies concerning the association between Helicobacter pylori status and colorectal adenoma, premalignant lesions of colorectal cancers, are not consistent.

METHODS

This cross-sectional study investigated the association of colorectal adenoma with H. pylori infection in a consecutive series of 2,195 asymptomatic average-risk subjects who underwent screening colonoscopy and H. pylori testing. Multivariate analyses were adjusted for potential relevant confounders, including age, sex, smoking, alcohol consumption, family history of colorectal cancer, and regular use of aspirin. Furthermore, we performed a systematic literature review and meta-analysis of available studies, including the current study, to clarify whether H. pylori infection is associated with an increased risk of colorectal adenoma.

RESULTS

Among 2,195 eligible subjects, 1,253 subjects were H. pylori seropositive and 942 subjects were seronegative. In the H. pylori (+) group, the prevalence of colorectal adenoma and advanced adenoma was significantly higher than in the H. pylori (-) group (25.3 vs. 20.1 %, p = 0.004 and 6.1 vs. 2.9 %, p < 0.001, respectively). In our multivariate analysis, H. pylori seropositivity was an independent risk factor for overall colorectal adenoma (OR = 1.36, 95 % CI = 1.10-1.68) and advanced adenoma (OR = 2.21, 95 % CI = 1.41-3.48). The positive association was confined in cases with any proximal adenoma. In the meta-analysis, which included ten studies and 15,863 patients, the pooled OR for colorectal adenoma related to H. pylori infection was 1.58 (95 % CI = 1.32-1.88).

CONCLUSION

Our results from this cross-sectional study and current studies included in our meta-analysis indicated that H. pylori infection was associated with a modest increase in the risk for colorectal adenoma.

Somatic mutations in CCK2R alter receptor activity that promote oncogenic phenotypes

The roles of cholecystokinin 2 receptor (CCK2R) in numerous physiologic processes in the gastrointestinal tract and central nervous system are well documented. There has been some evidence that CCK2R alterations play a role in cancers, but the functional significance of these alterations for tumorigenesis is unknown. We have identified six mutations in CCK2R among a panel of 140 colorectal cancers and 44 gastric cancers. We show that these mutations increase receptor activity, activate multiple downstream signaling pathways, increase cell migration, and promote angiogenesis. Our findings suggest that somatic mutations in CCK2R may promote tumorigenesis through deregulated receptor activity and highlight the importance of evaluating CCK2R inhibitors to block both the normal and mutant forms of the receptor.

Downregulation of the CCK-B receptor in pancreatic cancer cells blocks proliferation and promotes apoptosis

Gastrin stimulates the growth of pancreatic cancer cells through the activation of the cholecystokinin-B receptor (CCK-BR), which has been found to be overexpressed in pancreatic cancer. In this study, we proposed that the CCK-BR drives growth of pancreatic cancer; hence, interruption of CCK-BR activity could potentially be an ideal target for cancer therapeutics. The effect of CCK-BR downregulation in the human pancreatic adenocarcinoma cells was examined by utilizing specific CCK-BR-targeted RNA interference reagents. The CCK-BR receptor expression was both transiently and stably downregulated by transfection with selective CCK-BR small-interfering RNA or short-hairpin RNA, respectively, and the effects on cell growth and apoptosis were assessed. CCK-BR downregulation resulted in reduced cancer cell proliferation, decreased DNA synthesis, and cell cycle arrest as demonstrated by an inhibition of G(1) to S phase progression. Furthermore, CCK-BR downregulation increased caspase-3 activity, TUNEL-positive cells, and decreased X-linked inhibitor of apoptosis protein expression, suggesting apoptotic activity. Pancreatic cancer cell mobility was decreased when the CCK-BR was downregulated, as assessed by a migration assay. These results show the importance of the CCK-BR in regulation of growth and apoptosis in pancreatic cancer. Strategies to decrease the CCK-BR expression and activity may be beneficial for the development of new methods to improve the treatment for patients with pancreatic cancer.

Toward the identification of a reliable 3D QSAR pharmacophore model for the CCK2 receptor antagonism

The present study describes application of computational approaches to identify a validated and reliable 3D QSAR pharmacophore model for the CCK-2R antagonism through integrated ligand and structure based studies using anthranilic sulfonamide and 1,3,4-benzotriazepine based CCK-2R antagonists. The best hypothesis consisted five features viz. two aliphatic hydrophobic, one aromatic hydrophobic, one H-bond acceptor, and one ring aromatic feature with an excellent correlation for 34 training set (r²(training) = 0.83) and 58 test set compounds (r²(test) = 0.74). This model was validated through F-test and docking studies at the active site of the plausible CCK-2R where the 99% significance and well corroboration with the pharmacophore model respectively describes the model's reliability. The model also predicts well to other known clinically effective CCK-2R antagonists. Therefore, the developed model may useful in finding new scaffolds that may aid in design and develop new chemical entities (NCEs) as potent CCK-2R antagonists before their synthesis.

αV integrin: A new gastrin target in human pancreatic cancer cells

AIM: To analyse α_V integrin expression induced by gastrin in pancreatic cancer models.

METHODS: α_V integrin mRNA expression in human pancreatic cancer cells was analysed using a “cancer genes” array and confirmed by real-time reverse transcription-polymerase chain reaction (PCR). Western blotting and semi-quantitative immunohistochemistry were used to examine protein levels in human pancreatic cancer cell lines and pancreatic tissues, respectively. The role of α_V integrin on gastrin-induced cell adhesion was examined using blocking anti-α_V integrin monoclonal antibodies. Adherent cells were quantified by staining with crystal violet.

RESULTS: Using a “cancer genes” array we identified α_V integrin as a new gastrin target gene in human pancreatic cancer cells. A quantitative real-time PCR approach was used to confirm α_V integrin gene expression. We also demonstrate that Src family kinases and the PI 3-kinase, two signalling pathways specifically activated by the CCK-2 receptor (CCK2R), are involved in gastrin-mediated α_V integrin expression. In contrast, inhibition of the ERK pathway was without any effect on α_V integrin expression induced by gastrin. Our results also show that gastrin modulates cell adhesion viaα_V integrins. Indeed, in vitro adhesion assays performed on fibronectin show that gastrin significantly increases adhesion of pancreatic cancer cells. The use of blocking anti-α_V integrin monoclonal antibodies completely reversed the increase in cell-substrate adhesion induced by gastrin. In addition, we showed in vivo that the targeted CCK2R expression in the pancreas of Elas-CCK2 mice, leads to the overexpression of α_V integrin. This process may contribute to pancreatic tumour development observed in these transgenic animals.

CONCLUSION: α_V integrin is a new gastrin target in pancreatic cancer models and contributes to gastrin effects on cell adhesion.

Effects of lorglumide on growth and invasion of human pancreatic cancer cell line Mia PaCa-2 in vitro through the cholecystokinin-cholecystokinin-1 receptor pathway

BACKGROUND

Cholecystokinin (CCK) has been found to be a growth stimulant through its special receptor pathway, especially for gastrointestinal malignancies. Although the CCK-1 receptor has been shown to be highly expressed in resected human pancreatic cancer samples, its role is less clear.

OBJECTIVE

The aim of this in vitro study was to investigate the CCK-1 receptor expression and the function of the CCK-CCK-1 receptor pathway in the human pancreatic adenocarcinoma cell line, Mia PaCa-2.

METHODS

The expression of the CCK-1 receptor in Mia PaCa-2 cells was detected by reverse-transcriptase polymerase chain reaction and flow cytometry. CCK-1 receptor agonist CCK-8S (the major transmitter form of CCK) and antagonist lorglumide were cultured respectively with Mia PaCa-2. Three groups were created for this study: CCK-8S group (Mia PaCa-2 cells treated with CCK-8S), lorglumide group (Mia PaCa-2 cells treated with lorglumide), and the control group (Mia PaCa-2 cells alone). Investigators were blinded to group designation. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry were used to detect the cell growth, cell cycle, and apoptosis. Apoptosis index rate was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. Cell invasion ability was observed by invasion assay. Expression of matrix metalloproteinase-2 (MMP-2) was measured by Western blotting.

RESULTS

Mia PaCa-2 cells were found to express the CCK-1 receptor. Compared with the control group (70.2% [1.5%]), CCK-8S was associated with significant mean (SD) cell proliferation (85.1% [1.7%]; P = 0.039), and the ratio in the S stage of the cell cycle increased significantly (50.5% [1.7%] vs 42.2% [1.4%]; P = 0.021). CCK-8S was also associated with increased Mia PaCa-2 cell invasion ability (123.8 [1.7] vs 102.1 [5.8]; P = 0.005 vs control). Compared with the control group, lorglumide was associated with significantly inhibited cell growth (52.1% [1.8%]; P = 0.002) and cell invasion (77.6% [1.2%]; P = 0.003). Lorglumide also induced G0/G1 cell cycle arrest and apoptosis (27.1% [3-5%] vs 3-7% [0.6%]; P = 0.003 vs control). The change of invasion ability appeared to be mediated by MMP-2 expression, which was upregulated by CCK-8S and downregulated by lorglumide.

CONCLUSION

The findings of this in vitro study suggest that CCK may exert a trophic action on the Mia PaCa-2 cell line, while lorglumide inhibited the cell growth and invasion.

Novel application of proton pump inhibitor for the prevention of colitis-induced colorectal carcinogenesis beyond acid suppression

Colitis-associated cancers arise in the setting of chronic inflammation wherein an "inflammation-dysplasia-carcinoma" sequence prevails. Based on our previous findings in which the proton pump inhibitor could impose significant levels of anti-inflammatory, antiangiogenic, and selective apoptosis induction beyond gastric acid suppression, we investigated whether omeprazole could prevent the development of colitis-associated cancer in a mouse model induced by repeated bouts of colitis. Omeprazole, 10 mg/kg, was given i.p. all through the experimental periods for colitis-associated carcinogenesis. Molecular changes regarding inflammation and carcinogenesis were compared between control groups and colitis-associated cancer groups treated with omeprazole in addition to chemopreventive outcome. Nine of 12 (75.0%) mice in the control group developed multiple colorectal tumors, whereas tumors were noted in only 3 of 12 (25.0%) mice treated with daily injections of omeprazole. The cancer-preventive results of omeprazole treatment was based on significant decreases in the levels of nitric oxide, thiobarbituric acid-reactive substance, and interleukin-6 accompanied with attenuated expressions of tumor necrosis factor-alpha, inducible nitric oxide synthase, and cyclooxygenase-2. The expressions of matrix metalloproteinase (MMP)-9, MMP-11, and MT1-MMMP were significantly decreased in mice treated with omeprazole in accordance with significant decreases in the number of beta-catenin-accumulated crypts. A significant induction of apoptosis was observed in tumor tissue treated with omeprazole. Omeprazole could block the trophic effect of gastrin in colon epithelial cells. The significant anti-inflammatory, antioxidative, and antimutagenic activities of omeprazole played a cancer-preventive role against colitis-induced carcinogenesis, and our novel in vivo evidence is suggestive of chemopreventive action independent of gastric acid suppression.

Altered expression of MiR-148a and MiR-152 in gastrointestinal cancers and its clinical significance

BACKGROUND

MicroRNAs are endogenous small noncoding RNAs that aberrantly expressed in various carcinomas. MiR-148a and miR-152, which have the same "seed region", have not been comprehensively investigated in gastrointestinal cancers.

METHODS

Total RNA was extracted from the tissues of 101 patients with gastric cancer and 101 patients with colorectal cancer as well as their matched nontumor adjacent tissues. After polyadenylation and reverse transcription, the expression of miR-148a and miR-152 was determined using quantitative real-time polymerase chain reaction. The protein level of cholecystokinin B receptor, which might be the target gene of miR-148a and miR-152, was analyzed by Western blot in 40 patients with gastric cancer.

RESULTS

Expression levels of miR-148a and miR-152 in human gastric (p < 0.001 and p = 0.038, respectively, t-test) and colorectal (all p < 0.001) cancers were significantly lower than that in their matched nontumor adjacent tissues. Moreover, their low expression was also found in several gastrointestinal cancer cell lines compared with normal gastric epithelial cell line and normal colorectal tissue, respectively. A strong correlation was found between the expression of miR-148a and miR-152 (all p < 0.001, Pearson's correlation). Furthermore, low expression of miR-152 was correlated with increased tumor size (p = 0.023 and 0.004, respectively, Mann-Whitney U test) and advanced pT stage (p = 0.018 and 0.002, respectively) in gastrointestinal cancers. Low expression of miR-148a was also correlated with increased tumor size (p = 0.045 and 0.018, respectively) in gastrointestinal cancers, but only correlated with advanced pT stage (p = 0.023) in colorectal cancer. We also found the expression of miR-148a (p < 0.001, chi-square test) and miR-152 (p = 0.002) inversely correlated with cholecystokinin B receptor protein in gastric cancer.

CONCLUSION

MiR-148a and miR-152 may be involved in the carcinogenesis of gastrointestinal cancers and might be potential biomarkers in these cancers.

Gastrin stimulates the VEGF-A promotor in a human colon cancer cell line

INTRODUCTION

Hypergastrinemia has been observed in patients suffering from colorectal cancer. Vascular endothelial growth factor (VEGF) is known to play a pivotal role in tumour growth. Therefore, we addressed whether gastrin-17-gly and gastrin-17-amide regulate VEGF-A-gene and protein expression.

MATERIALS AND METHODS

Colo-320-cells were stably transfected with a VEGF-Luciferase-reporter gene. Luciferase activity was assessed after stimulation with various gastrin concentrations. Relevant promotor elements were identified by deletion analyses. VEGF protein levels in culture supernatants were quantified by ELISA.

RESULTS

VEGF-A stimulation with gastrin induced a dose- and time-dependent stimulation of luciferase activity. The greatest activities were found 6h after stimulation at concentrations of 10(-)(6)mmol/l. VEGF-promotor expression resulted in significantly (p<0.05) increased VEGF-A protein secretion. These effects were restricted to gastrin-17-amide.

CONCLUSION

Gastrin-17-amide enhances VEGF-A gene and protein expression in Colo320 cells stably transfected with a wild-type CCK-B/gastrin receptor. The induction of VEGF-A transcription and translation may contribute to the carcinogenic effects of gastrin observed in clinical studies. Therefore, CCK-B receptor antagonists may represent a treatment strategy in patients with colorectal cancer.

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.

Effect of gastrin on aquaporin 4 expression in human colon cancer HT-29 cell line

AIM: To observe the effect of gastrin on aquaporin 4 expression in human colon cancer HT-29 cell line, and to explore possible mechanism for gastrin promoting the invasion and metastasis in colon cancer.

METHODS: The human colon cancer HT-29 cells were cultivated in vitro and treated with gastrin in different concentrations (10^-6 mol/L, 10^-7 mol/L, 10^-8 mol/L) for 12 h. Simultaneously proglumide was used to block the gastrin receptors for 1 h and then treated with gastrin (10^-7 mol/L) again for 12 h. The expression level of aquaporin 4 was detected by immunocytochemistry and flow cytometry.

RESULTS: The aquaporin 4 expression levels were significantly higher in the gastrin treated group compared with the normal group and the proglumide group (16.08% ± 1.93%, 17.00% ± 2.72%, 16.48% ± 2.22% vs 9.28% ± 2.74%, 8.52% ± 2.72%, all P < 0.01). The levels between the proglumide group and the normal group had no difference. The expression levels among the three gastric treatment groups also had no difference.

CONCLUSION: Gastrin could elevate the aquaporin 4 expression level in colon cancer cells. This effect could be blocked by proglumide.

Somatostatin inhibits colon cancer cell growth through cyclooxygenase-2 downregulation

BACKGROUND AND PURPOSE

Cyclooxygenase-2 (COX-2) is expressed in colonic neoplasms, where it supports cell proliferation via prostaglandin E(2) (PGE(2)) production. This study investigated the effects of somatostatin-14 on COX-2 expression, PGE(2) production and proliferation in colon cancer cells.

EXPERIMENTAL APPROACH

Human colon adenocarcinoma cell lines Caco-2, HT-29 and HCT116 were used. The following techniques were employed: colourimetric assay for cell growth; 5-bromo-2'-deoxyuridine assay for DNA synthesis; enzyme immunoassay for PGE(2); COX-2 mRNA silencing; RT-PCR or Western blot for somatostatin receptor subtypes, cyclooxygenase isoforms, phosphorylated-ERK-1/ERK-2 and phosphorylated-Akt.

KEY RESULTS

HT-29 and Caco-2 cells expressed COX-2 and somatostatin receptors (sst(3/4/5) and sst(3/5), respectively). HCT116 cells did express somatostatin receptors (sst(2/3/5)), but not COX-2. Somatostatin-14 inhibited basal COX-2 expression, PGE(2) production, DNA synthesis and growth in Caco-2 cells and these effects were prevented by BN81658 (sst(3) receptor antagonist). Basal proliferation of HT-29, HCT116 and COX-2-silenced Caco-2 cells was not affected by somatostatin-14. Stimulation of HT-29 cells with gastrin-17 elicited increments of ERK-1/ERK-2 and Akt phosphorylation, COX-2 expression, PGE(2) production, DNA synthesis and cell growth, which were all counteracted by somatostatin-14. Somatostatin-14-induced inhibition of COX-2 expression, PGE(2) production and DNA synthesis were blocked by BIM23056 (sst(5) receptor antagonist).

CONCLUSIONS AND IMPLICATIONS

Somatostatin decreases COX-2 expression and function in colon cancer cells via activation of sst(3) or sst(5) receptors, and these effects contribute to the inhibitory action of somatostatin on cell proliferation. These findings can be relevant to the development of therapeutic strategies based on the modulation of the COX-2 pathway.

Pre-clinical evaluation of a new orally-active CCK-2R antagonist, Z-360, in gastrointestinal cancer models

BACKGROUND

Gastrin has a role in gastrointestinal (GI) malignancy. This study provides pre-clinical evaluation of a novel, orally-active gastrin/cholecystokinin-2 receptor (CCK-2R) antagonist, Z-360.

METHODS

(125)I gastrin-17 (G17) displacement and G17-stimulated calcium assays were used in classical CCK-2R-transfected cell lines. Akt phosphorylation was assessed by Western blotting. Z-360 efficacy in vivo was evaluated in three human xenograft models, and microvessel density and apoptosis in these models were investigated by immunohistochemistry.

RESULTS

Z-360 inhibited (125)I G17 binding to cells expressing CCK-2R, and G17-stimulated signalling. Reduced Akt phosphorylation in an oesophageal cell-line treated with Z-360 was reversed by co-treatment with G17. Z-360 increased survival in a gastric ascites model (p=0.011) and decreased tumour growth in a hepatic metastasis model (81%, p=0.02). In an orthotopic pancreatic model, Z-360 combined with gemcitabine decreased final tumour weight compared to single agents (84%, p=0.002) and there was increased apoptosis and decreased microvessel density in ex vivo tumour tissue.

CONCLUSIONS

These results show that the orally-active CCK-2R antagonist, Z-360 has high sub-nM affinity for classical CCK-2R, is well tolerated in vivo and exerts an anti-tumour effect.

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.

Cyclo-oxygenase-independent inhibition of apoptosis and stimulation of proliferation by leptin in human colon cancer cells

Obesity increases the risk of colon cancer. Hyperleptinemia is characteristic of obesity and leptin has been reported to be a colonic growth factor. We have examined the involvement of the cyclo-oxygenase (COX) pathways in the proliferation and anti-apoptotic effects of leptin. Leptin stimulated proliferation in HT-29 colon cancer cells: this was unaffected by inhibition of COX-1, COX-2, protein kinase C, or the epidermal growth factor receptor. Leptin did not increase COX-2 mRNA or COX-derived prostaglandin E2 production. Celecoxib induced apoptosis in a COX-independent manner. Leptin reduced both serum starvation- and celecoxib-induced apoptosis. Inhibition of ERK, p38 MAP kinase, and nuclear factor (NF)-kappaB abolished the growth-promoting and anti-apoptotic effects of leptin. Treatment of HT-29 cells with leptin stimulated phosphorylation of ERK and p38 MAP kinase and nuclear translocation of active NF-kappaB. We conclude that leptin stimulates colon cancer proliferation via COX-independent pathways and reduces celecoxib-induced apoptosis via ERK, p38 MAP kinase, and NF-kappaB pathways.

15-Deoxy-delta(12,14)-prostaglandin J(2) down-regulates CXCR4 on carcinoma cells through PPARgamma- and NFkappaB-mediated pathways

The chemokine receptor CXCR4 plays a key role in the metastasis of colorectal cancer and its growth at metastatic sites. Here, we have investigated the mechanisms by which CXCR4 on cancer cells might be regulated by eicosanoids present within the colorectal tumor microenvironment. We show that prostaglandins PGE(2), PGA(2), PGD(2), PGJ(2) and 15dPGJ(2) each down-regulates CXCR4 receptor expression on human colorectal carcinoma cells to differing degrees. The most potent of these were PGD(2) and its metabolites PGJ(2) and 15dPGJ(2). Down-regulation was most rapid with the end-product 15dPGJ(2) and was accompanied by a marked reduction in CXCR4 mRNA. 15dPGJ(2) is known to be a ligand for the nuclear receptor PPARgamma. Down-regulation of CXCR4 was also observed with the PPARgamma agonist rosiglitazone, while 15dPGJ(2)-induced CXCR4 down-regulation was substantially diminished by the PPARgamma antagonists GW9662 and T0070907. These data support the involvement of PPARgamma. However, the 15dPGJ(2) analogue CAY10410, which can act on PPARgamma but which lacks the intrinsic cyclopentenone structure found in 15dPGJ(2), down-regulated CXCR4 substantially less potently than 15dPGJ(2). The cyclopentenone grouping is known to inhibit the activity of NFkappaB. Consistent with an additional role for NFkappaB, we found that the cyclopentenone prostaglandin PGA(2) and cyclopentenone itself could also down-regulate CXCR4. Immunolocalization studies showed that the cellular context was sufficient to trigger a focal nuclear pattern of NFkappaB p50 and that 15dPGJ(2) interfered with this p50 nuclear localization. These data suggest that 15dPGJ(2) can down-regulate CXCR4 on cancer cells through both PPARgamma and NFkappaB. 15dPGJ(2), present within the tumor microenvironment, may act to down-regulate CXCR4 and impact upon the overall process of tumor expansion.

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.

Prostaglandin E2-EP4 receptor signalling promotes tumorigenic behaviour of HT-29 human colorectal cancer cells

The predominant product of cyclooxygenase (COX) activity in the colon, prostaglandin (PG) E2 promotes intestinal tumorigenesis. Expression of the PGE2 receptor EP4 is upregulated during colorectal carcinogenesis. Therefore, we investigated the role of elevated PGE2-EP4 receptor signalling in the protumorigenic activity of PGE2 by increasing EP4 receptor expression in HT-29 human colorectal cancer (CRC) cells (HT-29-EP4) by stable transfection. Elevated PGE2-induced EP4 receptor activity in HT-29 cells increased resistance to spontaneous apoptosis and promoted anchorage-independent growth, but had no effect on proliferation of HT-29-EP4 cells. EP4 receptor activation by PGE2 in HT-29-EP4 cells also led to development of fluid-filled cysts, which was associated with increased tight junction protein (occludin and zonula occludens-1) expression. Overexpression of the EP4 receptor in HT-29 cells led to basal EP4 receptor signalling in the absence of exogenous PGE2, which was explained by autocrine activity of endogenous, COX-2-derived PGE2 and constitutive, ligand-independent EP4 receptor activity. The predominant signalling pathway mediating antiapoptotic activity downstream of PGE2-EP4 receptor activation in HT-29-EP4 cells was elevation of cyclic adenosine monophosphate (cAMP) levels, which was associated with phosphorylation of cAMP-response element binding protein. EP4 receptor activation led to a small increase in phosphorylated extracellular signal-regulated kinase (ERK) 2 protein levels but inhibition of ERK phosphorylation did not abrogate the antiapoptotic activity of PGE2. However, PGE2-EP4 receptor signalling did not lead to trans-activation of the epidermal growth factor receptor in HT-29 cells. Inhibition of protumorigenic PGE2-EP4 receptor signalling represents a potential strategy for anti-CRC therapy that may avoid the toxicity associated with systemic COX inhibition.

Identification and Optimization of Anthranilic Sulfonamides as Novel, Selective Cholecystokinin-2 Receptor Antagonists

A high throughput screening approach to the identification of selective cholecystokinin-2 receptor (CCK-2R) ligands resulted in the discovery of a novel series of antagonists, represented by 1-[2-[(2,1,3-benzothiadiazol-4-ylsulfonyl)amino]-5-chlorobenzoyl]-piperidine (1; CCK-2R, pK(I) = 6.4). Preliminary exploration of the structure-activity relationships around the anthranilic ring and the amide and sulfonamide moieties led to a nearly 50-fold improvement of receptor affinity and showed a greater than 1000-fold selectivity over the related cholecystokinin-1 receptor. Pharmacokinetic evaluation led to the identification of 4-[4-iodo-2-[(5-quinoxalinylsulfonyl)amino]benzoyl]-morpholine, 26d, a compound that demonstrates promising pharmacokinetic properties in the rat and dog with respect to plasma clearance and oral bioavailability and is a potent inhibitor in vivo of pentagastrin-stimulated acid secretion in the rat when dosed orally.

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.

Constitutive expression of cyclooxygenase-2 in the neuromuscular compartment of normal human colon

Prostaglandins regulate various functions throughout the gastrointestinal system. Their biosynthesis depends on cyclooxygenase isoforms, named COX-1 and COX-2. The initial hypothesis that COX-2 is an inducible enzyme has been challenged and its constitutive expression in the stomach has been established. In this study, an immunohistochemical analysis was performed to evaluate the distribution and cellular localization of COX-2 in normal human colon. Colonic surgical specimens were processed for COX-2, protein HuC/HuD, neurofilament, S-100 protein and CD117/c-kit immunodetection. COX-2 protein was found to be constitutively expressed in the colonic wall: detectable amounts were localized in mucosal, submucosal and muscular layers, mainly in the neuromuscular compartment. In particular, COX-2 was expressed in muscularis mucosae, submucosal ganglia, longitudinal muscle layer and myenteric ganglia, the neurons of which displayed different degrees of immunostaining. Intramuscular interstitial cells of Cajal, regarded as important sites for the regulation of enteric neuromuscular activity, were also partly COX-2 immunoreactive. This study provides a detailed mapping of COX-2 expression in human colon, and allows better understanding of the roles played by this isoenzyme in gut physiology.

Synergistic inhibitory effect of NS-398 combined with AG-041R on gastric cancer cells

AIM: To investigate the inhibitory effects and mechanisms of combined treatment of a special COX-2 inhibitor (NS-398) and a special gastric receptor antagonist (AG-041R) on gastric cancer cell line MKN-45.

METHODS: The human gastric cancer cell line MKN-45 was treated with NS398 and AG-041R, respectively, or in combination. The growth of MKN-45 cells was detected by MTT assay; the cell apoptosis was detected by flow cytometry; the expression of c-Myc mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: NS-398 and AG-041R inhibited the growth of MKN-45 cells in a time- and dose-dependent manner (12-72 h; NS-398: 1 × 10^-8 - 1 × 10^-4 mol/L; AG-041R: 1 × 10^-8 - 1 × 10^-5 mol/L). AG-041R (1×10^-6 mol/L) and NS-398 (1×10^-5 mol/L) inhibited the proliferation of MKN-45 cells at rates of 42.1% and 41.8%, respectively, at 72 h. NS-398 and AG-041R in combination resulted in a synergistic effect on inhibiting growth, and the inhibition effect was enhanced along with time. When NS-398 (1×10^-5 mol/L) or AG-041R (1×10^-6 mol/L) or their combination was used, the rate of apoptosis was 9.57% ± 0.60%, 10.25% ± 0.68% and 20.83% ± 1.90%, respectively, which was significantly higher than the rate in the controls (1.67% ± 0.76%)(all P < 0.01), and the agents in combination induced a higher apoptosis rate than either of them did (P < 0.01). NS-398 and AG-041R down-regulated the level of c-Myc mRNA, respectively, but their combination down-regulated it more significantly than either of the agents did.

CONCLUSION: Combined treatment of NS-398 and AG-041R synergistically inhibits the growth of MKN-45 cells in a time- and dose-dependent manner, induces the cell apoptosis and down-regulates c-Myc mRNA expression in MKN-45 cells.

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.

Effects of cyclooxygenase-2 inhibition on serum and tumor gastrins and expression of apoptosis-related proteins in colorectal cancer

The objective of the present study was to determine the influence of cyclooxygenase-2 (COX-2) inhibition by Celecoxib (CLX) in humans with distal colorectal adenocarcinoma (CRC) on serum and tumor levels of progastrin and gastrin and serum levels of proinflammatory cytokines (IL-8, TNF-alpha). In addition, the effects of this CLX treatment on tumor and adjacent mucosa expression of gastrin, its receptors (CCK2), and COX-1 and COX-2, as well as protein expression of the active form of nuclear factor kappa B (NFkappa B) and the apoptotic-related proteins Bcl-2 and survivin, have been examined. Ten distal CRC patients were examined twice, once before and then after 14-day treatment with CLX (200 mg bid). Large biopsy samples were taken from the tumor and intact mucosa 10 cm above the tumor. For comparison, 20 age- and sex-matched healthy controls were enrolled and treated with CLX as CRC patients. Serum levels of IL-8 and TNF-alpha were measured by enzyme-linked immunosorbent assay, and serum levels of amidated gastrins and progastrin, by specific radioimmunoassay. The gene or protein expressions of progastrin, gastrin, CCK2, COX-1, COX-2, Bcl-2, and survivin as well as NFkappa B were determined by RT-PCR or Western blot in biopsy samples of tumor and intact mucosa of CRC patients. Serum IL-8 and TNF-alpha values were severalfold higher in CRC patients than in controls. The increase in serum proinflammatory cytokines was accompanied by increased expression of the active form of NFkappa B. Serum progastrin levels were also found to be significantly higher in CRC than in controls. Treatment of CRC with CLX resulted in a significant decrease in serum levels of progastrin and this was accompanied by an increment in tumor expression of COX-2 with a concomitant reduction in gastrin, Bcl-2, survivin, and NFkappa B expression. We conclude that (1) distal CRC patients show significantly higher serum progastrin levels than matched healthy controls, confirming that this hormone may be implicated in rectal carcinogenesis; (2) CRC patients exhibit significantly higher serum levels of IL-8 and TNF-alpha than healthy controls, probably reflecting more widespread inflammatory reaction in the colonic mucosa in CRC; (3) gastrin, COX-2, Bcl-2, survivin, and NFkappa B were overexpressed in CRC tumor compared to intact mucosa, but treatment with CLX significantly reduced serum levels of progastrin and IL-8 and TNF-alpha, which could mediate the up-regulation of COX-2 in CRC; and (4) CLX also enhanced expression of COX-2, while inhibiting the expression of gastrin, Bcl-2, survivin, and NFkappa B, suggesting that COX-2 inhibition might be useful in chemoprevention against CRC, possibly due to suppression of the antiapoptotic proteins and reduction in progastrin-induced and NFkappa B-promoted tumor growth.