Expression of gastrin and its receptor in human gastric cancer tissues

Gastrin/CCK-B Receptor Signaling Promotes Cell Invasion and Metastasis by Upregulating MMP-2 and VEGF Expression in Gastric Cancer

Accumulated evidence suggests that a functional loop composed of gastrin and cholecystokinin B receptor (CCK-BR) may exist in gastric carcinogenesis. However, this suggestion is not completely supported due to a lack of direct evidence, and the underlying mechanism is not completely understood. Here, we evaluated the effects of gastrin/CCK-BR signaling on the cell growth, invasion, and expression of MMP-2 and VEGF, as well as xenograft growth in vivo. Furthermore, we detected gastrin mRNA content in human gastric cancer tissues, metastatic lymph nodes, and adjacent nontumor tissues. We found that the forced gastrin could promote the proliferation, migration, and invasion of gastric cancer cells by upregulating the expression of MMP-2 and VEGF. Blocking gastrin/CCK-BR signal using either Proglumide, a CCK-BR antagonist, or shRNA against GASTRIN significantly inhibited the gastrin-promoting effects. In vivo study revealed that the tumor growth in nude mice inoculated with gastrin-overexpressed cells was significantly faster than control cells. The gastrin mRNA content in metastatic lymph nodes was higher in patients with gastric cancer than in primary gastric cancer and adjacent nontumor tissues. In conclusion, we provided direct evidence and possible mechanism of gastrin/CCK-BR signaling in the initiation and progression of gastric cancer.

Near-infrared (NIR) fluorescence-emitting small organic molecules for cancer imaging and therapy

We discuss recent advances made in the development of NIR fluorescence-emitting small organic molecules for tumor imaging and therapy.

Gastrin Vaccine Alone and in Combination With an Immune Checkpoint Antibody Inhibits Growth and Metastases of Gastric Cancer

Gastric cancer is a leading cause of cancer-related deaths worldwide. Recently, clinical studies have demonstrated that many of those with advanced gastric cancer are responsive to immune checkpoint antibody therapy, although the median survival even with these new agents is less than 12 months for advanced disease. The gastrointestinal peptide gastrin has been shown to stimulate growth of gastric cancer in a paracrine and autocrine fashion through the cholecystokinin-B receptor (CCK-BR), a receptor that is expressed in at least 56.6% of human gastric cancers. In the current investigation, we studied the role of the gastrin-CCK-BR pathway in vitro and in vivo as well as the expression of the CCK-BR in a human gastric cancer tissue array. CCK-BR and PD-L1 receptor expression and gastrin peptide was found in two murine gastric cancer cells (NCC-S1 and YTN-16) by qRT-PCR and immunocytochemistry. Treatment of NCC-S1 cells with gastrin resulted in increased growth. In vivo, the effects of a cancer vaccine that targets gastrin peptide (polyclonal antibody stimulator-PAS) alone or in combination with a Programed Death-1 antibody (PD-1 Ab) was evaluated in immune competent mice (N = 40) bearing YTN-16 gastric tumors. Mice were treated with PBS, PD-1 Ab (50 µg), PAS (250 µg), or the combination of PD-1 Ab with PAS. Tumor growth was significantly slower than controls in PAS-treated mice, and tumor growth was decreased even more in combination-treated mice. There were no metastases in any of the mice treated with PAS either alone or in combination with PD-1 Ab. Tumor proliferation by the Ki67 staining was significantly decreased in mice treated with PAS monotherapy or the combination therapy. PAS monotherapy or combined with PD-1 Ab increased tumor CD8+ T-lymphocytes and decreased the number of immunosuppressive M2-polarized tumor-associated macrophages. CCK-BR expression was identified in samples from a human tissue array by immunohistochemistry confirming the clinical relevance of this study. These results confirm the significance of the gastrin-CCK-BR signaling pathway in gastric cancer and suggest that the addition of a gastrin vaccine, PAS, to therapy with an immune checkpoint antibody may decrease growth and metastases of gastric cancer by altering the tumor microenvironment.

Pseudomonas Exotoxin A-Based Immunotherapy Targeting CCK2R-Expressing Colorectal Malignancies: An In Vitro and In Vivo Evaluation

Cholecystokinin-2 receptor (CCK2R) has been proven to be a specific biomarker for colorectal malignancies. Immunotoxins are a valuable class of immunotherapy agents consisting of a targeting element and a bacterial or plant toxin. Previous work demonstrated that targeting CCK2R is a good therapeutic strategy for the treatment of colorectal cancer (CRC). In the present study, we developed a new version of CCK2R-targeting immunotoxin GD9P using a targeted peptide, GD9, as the binding motif and a truncated Pseudomonas exotoxin A (PE38) as the cytokiller. BALB/c nude mice were treated with different doses of GD9P, and pharmacodynamics, pharmacokinetic, and toxicological data were obtained throughout this study. Compared to the parental immunotoxin rCCK8PE38, GD9P exhibited about 1.5-fold yield, higher fluorescence intensity, and increased antitumor activity against human CRC in vitro and in vivo. The IC50 values of GD9P in vitro ranged from 1.61 to 4.55 nM. Pharmacokinetic studies were conducted in mice with a T1/2 of 69.315 min. When tumor-bearing nude mice were treated with GD9P at doses ≥2 mg/kg for five doses, a rapid shrinkage in tumor volume and, in some cases, complete remission was observed. A preliminary safety evaluation demonstrated a good safety profile of GD9P as a Pseudomonas exotoxin A-based immunotherapy. The therapy in combination with oxaliplatin can increase the antitumor efficacy and reduce the toxic side effects caused by chemotherapy. In conclusion, the data support the use of GD9P as a promising immunotherapy targeting CCK2R-expressing colorectal malignancies.

The Diagnostic Value of Serum Gastrin-17 and Pepsinogen for Gastric Cancer Screening in Eastern China

Objective

To evaluate the diagnostic value of gastrin-17 (G-17) and pepsinogen (PG) in gastric cancer (GC) screening in China, especially eastern China, and to determine the best diagnostic combination and threshold (cutoff values) to screen out patients who need gastroscopy.

Methods

The serum concentrations of G-17 and pepsinogen I and II (PGI and PGII) in 834 patients were analyzed, and the PGI/PGII ratio (PGR) was calculated. According to pathological results, patients can be divided into chronic nonatrophic gastritis (NAG)/chronic atrophic gastritis (CAG)/intraepithelial neoplasia (IN)/GC groups. The differences in G-17, PG, and PGR in each group were analyzed, and their values in GC diagnosis were evaluated separately and in combination.

Results

There were differences in serum G-17, PGII, and PGR among the four groups (NAG/CAG/IN/GC) (P ≤ 0.001). In total, 54 GC cases were diagnosed, of which 50% were early GC. There was no significant difference in the PGI levels among the four groups (P = 0.377). NAG and CAG composed the chronic gastritis (CG) group. The G-17 and PGII levels in the IN and GC groups were higher than those in the CG group (both P ≤ oth C), while the PGR levels were lower (P ≤ lower). When distinguishing NAG from CAG, the best cutoff value for G-17 was 9.25 pmol/L, PGII was 7.06 μg/L, and PGR was 12.07. When distinguishing CG from IN, the best cutoff value for G-17 was 3.86 pmol/L, PGII was 11.92 μg/L, and PGR was 8.26. When distinguishing CG from GC, the best cutoff value for G-17 was 3.89 pmol/L, PGII was 9.16 μg/L, and PGR was 14.14. The sensitivity, specificity, accuracy, and positive and negative predictive values of G-17/PGII/PGR for GC diagnosis were 83.3%/70.4%/79.6%, 51.8%/56.3%/47.8%, 53.8%/57.2%/49.9%, 10.7%/10.9%/9.6%, and 97.8%/96.5%/97.1%, respectively. The sensitivity, specificity, accuracy, and positive predictive and negative predictive values of PGII/G-17 vs. PGR/G-17 vs. PGR/PGII in the diagnosis of GC were 63.0% vs. 70.4% vs. 64.8%, 70.5% vs. 70.1% vs. 60.4%, 70.0% vs. 70.1% vs. 60.7%, 12.9% vs. 14.0% vs. 10.2%, and 96.5% vs. 97.2% vs. 96.1%, respectively.

Conclusion

The PGII and G-17 levels in patients with gastric IN and GC were significantly increased, while the serum PGR level was significantly decreased. Serological detection is effective for screening GC. The combination of different markers can improve the diagnostic efficiency. The highest diagnostic accuracy was G-17 combined with PGR, and the best cutoff values were G − 17 > 3.89 pmol/L and PGR < 14.14.

[99mTc]Tc-DGA1, a Promising CCK2R-Antagonist-Based Tracer for Tumor Diagnosis with Single-Photon Emission Computed Tomography

Radiolabeled gastrin analogues have been proposed for theranostics of cholecystokinin subtype 2 receptor (CCK₂R)-positive cancer. Peptide radioligands based on other receptor antagonists have displayed superior pharmacokinetics and higher biosafety than agonists. Here, we present DGA1, a derivative of the nonpeptidic CCK₂R antagonist Z-360 carrying an acyclic tetraamine, for [^99mTc]Tc labeling. Preclinical comparison of [^99mTc]Tc-DGA1 with [^99mTc]Tc-DG2 (CCK₂R-agonist reference) was conducted in HEK293-CCK₂R/CCK_2i4svR cells and mice models, qualifying [^99mTc]Tc-DGA1 for further study in patients with CCK₂R-positive tumors and single-photon emission computed tomography/CT.

Can Proximal Gastrectomy with Double-Tract Reconstruction Replace Total Gastrectomy? A Propensity Score Matching Analysis

BACKGROUND

This retrospective cohort study compared proximal gastrectomy (PG) with double-tract reconstruction (DTR) versus total gastrectomy (TG) with Roux-en-Y reconstruction in terms of clinical outcomes.

METHODS

All consecutive patients with upper early gastric cancer (EGC) who underwent PG-DTR or TG in 2008-2016 were selected. TG patients who matched PG-DTR patients in age, sex, body mass index, clinical stage, and ASA score were selected by propensity score matching. Groups were compared in terms of clinicopathological characteristics, clinical outcomes, early (≤ 30 days), late (> 30 days), and severe (Clavien-Dindo grade ≥ III) postoperative complications, 1-year reflux morbidity, recurrence, and mortality.

RESULTS

Of 322 patients, 52 underwent PG-DTR. A matching TG group of 52 patients was selected. The PG-DTR group had smaller tumors (p = 0.02), smaller proximal and distal resection margins (p = 0.01, p < 0.01), and fewer retrieved lymph nodes (p < 0.01). PG-DTR associated with shorter times to diet and hospital stay (both p = 0.02). Groups did not differ in early (11.3 vs. 19.2%, p = 0.19), late (1.9 vs. 5.7%, p = 0.31), or severe complication rates (7.7 vs. 13.5%, p = 0.34). At 1 year, the groups did not differ in reflux symptoms (Visick score) or endoscopic esophagitis (Los Angeles Classification). There were no recurrences. Five-year overall survival rates were 100 and 81.6% (p = 0.02), respectively.

CONCLUSION

PG-DTR associated with better clinical outcomes and survival. Complication and reflux rates were similar. PG-DTR may be suitable for upper EGC.

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 cancer and gastrin: on the interaction of Helicobacter pylori gastritis and acid inhibitory induced hypergastrinemia

Gastric cancer, a disease with a reduced frequency for decades, now appears to be on the rise again in young Americans. The epidemiology of gastric cancer differs between tumors in the cardia and those of the more distal parts of the stomach. The tumors are divided into the intestinal type showing glandular growth pattern and the diffuse type with a different pattern. The latter often expresses neuroendocrine and more specifically ECL-cell markers suggesting that they originate from the ECL cell, the target cell for the antral hormone, gastrin. Helicobacter pylori gastritis is accepted as the major cause of gastric cancer, but only after having induced oxyntic atrophy which reduces gastric acid secretion and thus induces hypoacidity leading to hypergastrinemia. Long-term hypergastrinemia is known to induce malignant neoplasia in the stomach of animals as well as man. Recently treatment with proton pump inhibitor after Helicobacter pylori eradication in patients with gastroesophageal reflux disease, has been reported to predispose to gastric cancer. Since profound acid inhibition is a well-known cause of gastric neoplasia, it is to be expected that Helicobacter pylori infection and profound acid inhibition has an additive or possibly potentiating effect on the development of gastric cancer.

Neuroendocrine neoplasms of gastrointestinal tract and secondary primary synchronous tumors: A systematic review of case reports. Casualty or causality?

BACKGROUND

Neuroendocrine neoplasms (NENs) can arise in most of the epithelial organs of the body and are not a rare condition in the gastrointestinal tract (GIT). The presence of NENs in GIT associated with other secondary primary malignancies (SPM) has been considered an exotic event. This study aims to describe the case reports of NENs accompanied by synchronous primary tumors.

METHODS AND FINDINGS

We performed a systematic literature search of the databases Scopus, PubMed, Scielo and LILACS to identify case reports that described the presence of NENs in GIT with SPM. 78 case reports were included. The mean of age of the cases was 60.2 years. 60% were male. 95.4% were NENs G1. 17 cases of NENs had metastasis. 80% of SPM were recognized in the GIT (36% in stomach, 27% in large intestine, 11.2% in small intestine, and 5.6% in esophagus). The most common type of SPM was adenocarcinoma (49.4%), followed by GIST (13.5%), other NENs in different GIT segment (7.9%), lymphoma (6.8%), and squamous cell carcinoma (4.5%). The most common tumor in GIT was adenocarcinoma (97.6%) and the presence of adenocarcinoma in the same segment of GIT was found in 68.4% of the cases. Association between adenocarcinomas and NENs in GIT (p:<0.0001) and adenocarcinoma and tumor in the same segment of GIT location were observed (p<0.001).

CONCLUSION

These results demonstrate that NENs with SPM are not a rare condition. Several theories have been proposed to explain this association; one of these is the ability of NENs to generate synchronous tumors by autocrine and paracrine effect. We observed an association between adenocarcinomas and NENs in the same segment of GIT.

Gastrin and Gastric Cancer

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

Gastrin activates autophagy and increases migration and survival of gastric adenocarcinoma cells

BACKGROUND

The peptide hormone gastrin exerts a growth-promoting effect in both normal and malignant gastrointestinal tissue. Gastrin mediates its effect via the cholecystokinin 2 receptor (CCKBR/CCK2R). Although a substantial part of the gastric adenocarcinomas express gastrin and CCKBR, the role of gastrin in tumor development is not completely understood. Autophagy has been implicated in mechanisms governing cytoprotection, tumor growth, and contributes to chemoresistance. This study explores the role of autophagy in response to gastrin in gastric adenocarcinoma cell lines.

METHODS

Immunoblotting, survival assays and the xCELLigence system were used to study gastrin induced autophagy. Chemical inhibitors of autophagy were utilized to assess the role of this process in the regulation of cellular responses induced by gastrin. Further, knockdown studies using siRNA and immunoblotting were performed to explore the signaling pathways that activate autophagy in response to gastrin treatment.

RESULTS

We demonstrate that gastrin increases the expression of the autophagy markers MAP1LC3B-II and SQSTM1 in gastric adenocarcinoma cells. Gastrin induces autophagy via activation of the STK11-PRKAA2-ULK1 and that this signaling pathway is involved in increased migration and cell survival. Furthermore, gastrin mediated increase in survival of cells treated with cisplatin is partially dependent on induced autophagy.

CONCLUSION

This study reveals a novel role of gastrin in the regulation of autophagy. It also opens up new avenues in the treatment of gastric cancer by targeting CCKBR mediated signaling and/or autophagy in combination with conventional cytostatic drugs.

Fluorescent chemical probes for accurate tumor diagnosis and targeting therapy

This review focuses on small molecular ligand-targeted fluorescent imaging probes and fluorescent theranostics, including their design strategies and applications in clinical tumor treatment.

Insights into gastric neuroendocrine tumors burden

Type 1 gastric neuroendocrine tumors (gNETs) are usually small lesions, restricted to mucosal and sub-mucosal layers of corpus and fundus, with low aggressive behavior, for the majority of cases. Nevertheless, some cases present aggressive behavior. The increasing incidence of gNETs brings together a new relevant problem: how to identify potentially aggressive type 1 gNETs. The challenging problem seems to be finding out signs or features able to predict potentially aggressive cases, allowing a tailored approach, since the involved societies dedicated to provide guidelines for management of these neoplasms apparently failed in producing staging systems able to accurately predict prognosis of these tumors. Additionally, it is also important to try to find out explanations for increasing incidence, as well as to identify potential targets aiming to reach better control of this neoplasia. Here, we discuss potential pathways implicated in aggressive behavior, as well as new strategies to improve clinical management of these tumors.

Assessment of cholecystokinin 2 receptor (CCK2R) in neoplastic tissue

The expression of cholecystokinin 2 receptor (CCK2R, CCKBR or gastrin receptor) has been reported on a diverse range of cancers such as colorectal, liver, lung, pancreatic, ovarian, stomach, thyroid and numerous neuroendocrine/carcinoid tumors. Some cancers of the colorectum, lung, pancreas and thyroid have been shown to overexpress CCK2R in relation to normal matched tissues of the same organ. This reported overexpression has led to the development of a number of CCK2R-ligand targeted imaging and therapeutic agents. However, no comprehensive study comparing the expression of CCK2R in multiple cancers to multiple normal tissues has been performed. Herein, we report the immunohistochemical analysis of cancer samples from gastrointestinal stromal tumor (GIST), hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, and thyroid cancer against multiple normal tissue samples from esophagus, liver, lung, pancreas, stomach, spleen and thyroid. These results show that CCK2R expression is present in nearly all cancer and normal samples tested and that none of the cancer samples had expression that was statistically greater than that of all of the normal samples.

Small Molecules for Active Targeting in Cancer

For the purpose of this review, active targeting in cancer research encompasses strategies wherein a ligand for a cell surface receptor expressed on tumor cells is used to deliver a cytotoxic or imaging cargo. This area of research is more than two decades old, but in those 20 and more years, how many receptors have been studied extensively? What kinds of the ligands are used for active targeting? Are they mostly naturally occurring molecules such as folic acid, or synthetic substances developed in campaigns for medicinal chemistry efforts? This review outlines the most important receptor or ligand combinations that have been used in active targeting to answer these questions, and therefore to address the most important one of all: is research in active targeting affording diminishing returns, or is this an area for which the potential far exceeds progress made so far?

Selective Tumor Targeting of Desacetyl Vinblastine Hydrazide and Tubulysin B via Conjugation to a Cholecystokinin 2 Receptor (CCK2R) Ligand

As the delivery of selectively targeted cytotoxic agents via antibodies or small molecule ligands to malignancies has begun to show promise in the clinic, the need to identify and validate additional cellular targets for specific therapeutic delivery is critical. Although a multitude of cancers have been targeted using the folate receptor, PSMA, bombesin receptor, somatostatin receptor, LHRH, and α_vβ₃, there is a notable lack of specific small molecule ligand/receptor pairs to cellular targets found within cancers of the GI tract. Because of the selective GI tract expression of the cholecystokinin 2 receptor (CCK2R), we undertook the creation of conjugates that would deliver microtubule-disrupting drugs to malignancies through the specific targeting of CCK2R via a high affinity small molecule ligand. The cytotoxic activity of these conjugates were shown to be receptor mediated in vitro and in vivo with xenograft mouse models exhibiting delayed growth or regression of tumors that expressed CCK2R. Overall, this work demonstrates that ligands to CCK2R can be used to create selectively targeted therapeutic conjugates.

Hypergastrinemia

Gastrin is an important hormone of the digestive system, which assists gastric acid secretion. It may be pathologically elevated in conditions such as Zollinger-Ellison syndrome, or due to common medications such as proton pump inhibitors. In this review we provide an overview of the pathophysiology and medical causes of hypergastrinemia, diagnostic testing and clinical consequences of chronic hypergastrinemia.

Evaluation of a nonpeptidic ligand for imaging of cholecystokinin 2 receptor-expressing cancers

Tumor-specific targeting ligands were recently exploited to deliver both imaging and therapeutic agents selectively to cancer tissues in vivo. Because the cholecystokinin 2 receptor (CCK2R) is overexpressed in various human cancers (e.g., lung, medullary thyroid, pancreatic, colon, and gastrointestinal stromal tumors) but displays limited expression in normal tissues, natural ligands of CCK2R were recently explored for use in the imaging of CCK2R-expressing cancers. Unfortunately, the results from these studies revealed not only that the peptidic CCK2R ligands were unstable in vivo but also that the ligands that mediated good uptake by tumor tissues also promoted a high level of retention of the radioimaging agent in the kidneys, probably because of capture of the conjugates by peptide-scavenging receptors. In an effort to reduce the normal organ retention of CCK2R-targeted drugs, we synthesized a nonpeptidic ligand of CCK2R and examined its specificity for CCK2R both in vitro and in vivo.

METHODS

Nonpeptidic agonists and antagonists of CCK2R described in the literature were evaluated for their affinities and specificities for CCK2R. Z-360, a benzodiazepine-derived CCK2R antagonist with subnanomolar affinity, was selected for complexation to (99m)Tc via multiple spacers. After synthesis and purification, 4 complexes with different physicochemical properties were evaluated for binding to CCK2R-transfected HEK 293 cells. The best conjugate, termed CRL-3-(99m)Tc, was injected into mice bearing CCK2R tumor xenografts and examined by γ scintigraphy and SPECT/CT. The uptake of the conjugate in various organs was also quantified by tissue resection and γ counting.

RESULTS

CRL-3-(99m)Tc was shown to bind with low nanomolar affinity to CCK2R in vitro and was localized to tumor tissues in athymic nu/nu mice implanted with CCK2R-expressing tumors. At 4 h after injection, tumor uptake was measured at 12.0 ± 2.0 percentage injected dose per gram of tissue.

CONCLUSION

Because the uptake of CRL-3-(99m)Tc by nonmalignant tissues was negligible and retention in the kidneys was only transient, we suggest that CRL-3-(99m)Tc may be a useful radioimaging agent for the detection, sizing, and monitoring of CCK2R-expressing tumors.

Cholecystokinin and pancreatic cancer: the chicken or the egg?

The gastrointestinal peptide cholecystokinin (CCK) causes the release of pancreatic digestive enzymes and growth of the normal pancreas. Exogenous CCK administration has been used in animal models to study pancreatitis and also as a promoter of carcinogen-induced or Kras-driven pancreatic cancer. Defining CCK receptors in normal human pancreas has been problematic because of its retroperitoneal location, high concentrations of pancreatic proteases, and endogenous RNase. Most studies indicate that the predominant receptor in human pancreas is the CCK-B type, and CCK-A is the predominant form in rodent pancreas. In pancreatic cancer cells and tumors, the role of CCK is better established because receptors are often overexpressed by these cancer cells and stimulation of such receptors promotes growth. Furthermore, in established cancer, endogenous production of CCK and/or gastrin occurs and their actions stimulate the synthesis of more receptors plus growth by an autocrine mechanism. Initially it was thought that the mechanism by which CCK served to potentiate carcinogenesis was by interplay with inflammation in the pancreatic microenvironment. But with the recent findings of CCK receptors on early PanIN (pancreatic intraepithelial neoplasia) lesions and on stellate cells, the question has been raised that perhaps CCK actions are not the result of cancer but an early driving promoter of cancer. This review will summarize what is known regarding CCK, its receptors, and pancreatic cancer, and also what is unknown and requires further investigation to determine which comes first, the chicken or the egg, "CCK or the cancer."

Evaluation of a cholecystokinin 2 receptor-targeted near-infrared dye for fluorescence-guided surgery of cancer

Surgical resection of malignant disease remains one of the most effective tools for treating cancer. Tumor-targeted near-infrared dyes have the potential to improve contrast between normal and malignant tissues, thereby enabling surgeons to more quantitatively resect malignant disease. Because the cholecystokinin 2 receptor (CCK2R and its tumor-specific splice variant CCK2i4svR) is overexpressed in cancers of the lungs, colon, thyroid, pancreas, and stomach, but absent or inaccessible to parenterally administered drugs in most normal tissues, we have undertaken to design a targeting ligand that can deliver attached near-infrared dyes to CCK2R+ tumors. We report here the synthesis and biological characterization of a CCK2R-targeted conjugate of the near-infrared dye, LS-288 (CRL-LS288). We demonstrate that CRL-LS288 binds selectively to CCK2R+ cancer cells with low nanomolar affinity (Kd = 7 × 10(-9) M). We further show that CRL-LS288 localizes primarily to CCK2R-expressing HEK 293 murine tumor xenografts and that dye uptake in these xenografts is significantly reduced when CCK2R are blocked by preinjection of excess ligand (CRL) or when mice are implanted with CCK2R-negative tumors. Because CRL-LS288 is also found to reveal the locations of distant tumor metastases, we suggest that CRL-LS288 has the potential to facilitate intraoperative identification of malignant disease during a variety of cancer debulking surgeries.

Influence of d-glutamine and d-glutamic acid sequences in optical peptide probes targeted against the cholecystokinin-2/gastrin-receptor on binding affinity, specificity and pharmacokinetic properties

Background

Image-based diagnosis of tumours can be advanced and improved by targeted strategies addressing malignant molecular structures. A promising molecular target is the cholecystokinin-2-receptor (CCK2R) which can be targeted by high-affinity peptides called minigastrins. Here we present how the imaging properties of minigastrins tagged with near-infrared fluorescence (NIRF) dyes can be modulated by the introduction of different spacer sequences. We identify interactions of different probe variants with regard to target affinity, specificity and pharmacokinetic properties to optimize early detection of CCK2R-expressing tumours under clinical conditions.

Methods

Two minigastrin probes with the same near-infrared hemicyanine fluorescence dye (DY-754) for signalling and the same CCK2R-binding peptide A-Y-G-W-M/Nle-N-F-amide but different spacers were designed as follows: ‘QE’ with three alternating d-glutamines and d-glutamic acids and ‘bivQ’ with two minigastrins, each preceded by three d-glutamines. They were tested for affinity and specificity in vitro on CCK2R-expressing and CCK2R-non-expressing cells. In vivo imaging was conducted with subcutaneous tumour-bearing nude mice after i.v. probe injection (54 to 108 nmol/kg) and under competitive conditions with non-fluorescent minigastrin (n = 5/group). We also assessed probe biodistribution as well as NIRF distribution in tumour sections.

Results

Both probes showed high affinity and specificity to CCK2R-expressing cells in vitro. In vivo tumour-to-background contrasts (tumour/background ratios (TBRs) of around 6) enabled identification of CCK2R-expressing tumours by both probes with low accumulation in CCK2R-negative tumours (TBR of around 2). Specificity of the in vivo accumulation, revealed by competition, was higher for QE. Besides renal retention, probe uptake into organs was very low.

Conclusion

The properties of optical minigastrin probes can be specifically modified by the introduction of spacer sequences. A spacer of six hydrophilic amino acids increases affinity. A mix of d-glutamic and d-glutamine acids increased target-to-background contrast. Multimerization could not increase affinity but supposedly lowered stability. The probe QE is a promising candidate for clinical evaluation in terms of diagnosis of CCK2R-expressing tumours.

Association between CagA/ERK signaling pathway and gastric cancer

Cytotoxin-associated gene A (CagA) of Helicobacter pylori is the first identified bacterial oncoprotein that plays a critical role in gastric carcinogenesis. Upon delivery into gastric epithelial cells via type IV secretion, CagA can interfere with a number of host signaling pathways. Extracellular signal-regulated kinase (ERK) signaling pathway is a hub in cellular signal transduction, through which CagA elicits a series of cellular events including cell proliferation, apoptosis, scatter and metastasis, all of which are associated with gastric carcinogenesis. Here we perform a review of the association between CagA/ERK signaling pathway and gastric cancer.

Characterization of gastrins and their receptor in solid human gastric adenocarcinomas

OBJECTIVE

The gastrin and the gastrin/CCK-B receptor genes are co-expressed in several carcinomas. The primary translational product, progastrin, however, is processed to several peptides of which only those that are α-amidated at their C-terminus are receptor ligands. So far, characterization of the progastrin-derived peptides in gastric cancer has not been reported. The authors therefore examined the molecular nature of gastrin and its receptor in human gastric carcinomas.

MATERIALS AND METHODS

Twenty patients with adenocarcinoma underwent partial or total gastrectomy. In samples from each carcinoma, gastrin peptides were characterized, using a library of sequence-specific immunoassays. Expression was also demonstrated by immunohistochemistry. In addition, the gastrin and gastrin/CCK-B receptor gene expression was quantitated using real-time PCR, and the receptor protein demonstrated by western blotting.

RESULTS

α-Amidated gastrins were detectable in 16 of 20 carcinomas (median concentration 2.1 pmol/g tissue; range 0-386 pmol/g tissue). The tissue concentrations correlated closely to the gastrin mRNA contents (r = 0.75, p < 0.0001). Moreover, progastrin and non-amidated processing intermediates, including glycine-extended gastrins, were detected in 19 carcinomas. Immunohistochemistry corroborated gastrin expression in carcinoma cells. Chromatography revealed extensive progastrin processing with α-amidated gastrin-34 and -17 (tyrosyl-sulfated as well as non-sulfated) as major products. Finally, gastrin/CCK-B receptor mRNA and protein were detected in all tumors.

CONCLUSIONS

The results show that the elements for a local loop of α-amidated gastrins and their receptor are detectable in 80% of human gastric adenocarcinomas. Therefore, the results support the contention that locally expressed gastrin may be involved in the tumorigenesis of gastric adenocarcinomas.

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.

Cholecystokinin and gastrin receptors targeting in gastrointestinal cancer

Cholecystokinin and Gastrin are amongst the first gastrointestinal hormone discovered. In addition to classical actions (contraction of gallbladder, growth and secretion in the stomach and pancreas), these also act as growth stimulants for gastrointestinal malignancies and cell lines. Growth of these tumours is inhibited by antagonists of the cholecystokinin and gastrin receptors. These receptors provides most promising approach in clinical oncology and several specific radiolabelled ligands have been synthesized for specific tumour targeting and therapy of tumours overexpressing these receptors. Therefore, definition of the molecular structure of the receptor involved in the autocrine/paracrine loop may contribute to novel therapies for gastrointestinal cancer. Hence, this review tries to focus on the role and distribution of these hormones and their receptors in gastrointestinal cancer with a brief talk about the clinical trial using available agonist and antagonist in gastrointestinal cancers.

Operating room to bench for gastric cancer

Gastric cancer is the most common cancer in Korea, with an age-standardized rate of 61.2 in males and 23.9 in females (in 2007), one of the highest in the world. Using a large gastric tissue depository and the extensive clinical experience gained from gastric cancer surgery, we work as a 'translational researcher' to apply basic research tools and results to the clinical field. We are also interested in providing answers to the questions in the operating room using the methods of basic research. I would like to introduce our research activities in this review paper.

Human gastrin mRNA expression up-regulated by Helicobacter pylori CagA through MEK/ERK and JAK2-signaling pathways in gastric cancer cells

BACKGROUND

Helicobacter pylori-cytotoxin-associated protein A (CagA) and gastrin are believed to play an important role in gastric carcinogenesis, but their interaction has been incompletely clear.

METHODS

We constructed a eukaryotic expression vector pcDNA3.1/cagA and a luciferase reporter vector pGL/gastrin promoter, and then co-transfected them into gastric cancer AGS and SGC-7901 cells. The two kinds of gastric cancer cells were, respectively, infected with cagA-positive H. pylori NCTC11637, and then the gastrin promoter activity and gastrin mRNA level were detected with a Dual-Luciferase reporter assay system and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. Next, after the MEK/ERK and JAK2-signaling pathway inhibitors, U0126 and AG490, were used to treat the two cell lines, or the ERK1 and JAK2 genes were knocked down by siRNAs (small interference RNAs) in the two cell lines, the gastrin promoter activity and gastrin mRNA level were observed again.

RESULTS

The results indicated that CagA could activate the gastrin promoter and up-regulate gastrin mRNA expression in AGS and SGC-7901 cells, but these effects could be inhibited by the inhibitors U0126 and AG490, and the CagA-induced gastrin mRNA expression was down-regulated in the cells whose ERK1 or JAK2 gene was knocked down.

CONCLUSION

Gastrin promoter may be the transcriptional target of CagA, and CagA activates the gastrin promoter to up-regulate gastrin mRNA expression through the MEK/ERK and JAK1-signaling pathway in gastric cancer cells.

Expression profile of cholecystokinin type-A receptor in gallbladder cancer and gallstone disease

BACKGROUND

Regulatory peptide receptors have attracted the interest of oncologists as a new promising approach for cancer pathology, imaging and therapy. Although cholecystokinin (CCK) is a potent modulator of gallbladder contractility and plays a potential role in pancreatic carcinogenesis through CCK type-A receptor (CCKAR), its role in gallbladder cancer (GBC) is still unknown and immunohistochemical detection of CCKAR in the gallbladder has not yet been reported. This novel case-control study aimed to investigate the expression profile of CCKAR in GBC and gallstone disease (GSD).

METHODS

This study included 162 samples of gallbladder: 94 from GBC and 68 from GSD. Expression of CCKAR was analyzed by immunohistochemistry and immunoblotting. The results were statistically correlated with disease history including age, sex, presence of gallstone, stage and differentiation.

RESULTS

CCKAR was positive in 30/68 (44.1%) of GSD and 72/94 (76.6%) of GBC samples. Fifty-one of the 72 (70.8%) CCKAR-positive GBC samples showed over-expression. Interestingly, consistent results also appeared in the immunoblotting study.

CONCLUSIONS

CCKAR expression was significantly increased in GBC compared to GSD. Moreover, CCKAR expression was associated with the degree of tumor differentiation, i.e., less expression in poorly-differentiated tumors. Thus, it has future prognostic and therapeutic implications in the management of GBC.

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.

A combinatorial approach for the design of complementarity-determining region-derived peptidomimetics with in vitro anti-tumoral activity

The great success of therapeutic monoclonal antibodies has fueled research toward mimicry of their binding sites and the development of new strategies for peptide-based mimetics production. Here, we describe a new combinatorial approach for the production of peptidomimetics using the complementarity-determining regions (CDRs) from gastrin17 (pyroEGPWLEEEEEAYGWMDF-NH(2)) antibodies as starting material for cyclic peptide synthesis in a microarray format. Gastrin17 is a trophic factor in gastrointestinal tumors, including pancreatic cancer, which makes it an interesting target for development of therapeutic antibodies. Screening of microarrays containing bicyclic peptidomimetics identified a high number of gastrin binders. A strong correlation was observed between gastrin binding and overall charge of the peptidomimetic. Most of the best gastrin binders proceeded from CDRs containing charged residues. In contrast, CDRs from high affinity antibodies containing mostly neutral residues failed to yield good binders. Our experiments revealed essential differences in the mode of antigen binding between CDR-derived peptidomimetics (K(d) values in micromolar range) and the parental monoclonal antibodies (K(d) values in nanomolar range). However, chemically derived peptidomimetics from gastrin binders were very effective in gastrin neutralization studies using cell-based assays, yielding a neutralizing activity in pancreatic tumoral cell lines comparable with that of gastrin-specific monoclonal antibodies. These data support the use of combinatorial CDR-peptide microarrays as a tool for the development of a new generation of chemically synthesized cyclic peptidomimetics with functional activity.

Molecular aspects in the diagnosis of gastric cancer

BACKGROUND

Gastric cancer (GC) represents the second most common cause of cancer-related death worldwide. The prognosis remains poor, with limited treatment options. A better understanding of the initiation and progression of GC would enable the development of general screening strategies and individualized treatment modalities.

OBJECTIVE

The assessment of tools and molecular markers for the early detection and diagnosis of GC.

METHODS

Human clinical studies published within the past 5 years are reviewed. Also, significant previous data on markers in clinical use or on relevant animal or cell culture experiments are considered.

RESULTS/CONCLUSION

Serum-based screening strategies are not ready for routine application but represent an opportunity for the identification of individuals at high risk with the need for primary gastroscopy and further surveillance, which would ultimately improve survival and prognosis of GC. Infection with Helicobacter pylori represents the principal risk factor for gastric carcinogenesis. Bacterial virulence and host genetic factors contribute to individual susceptibility. Key molecular alterations in gastric carcinogenesis are related to intra- and extracellular cascades that regulate cell proliferation, tumor invasion and metastastic spread. For the development of effective prevention and treatment modalities, it is essential to unravel the basic mechanisms of gastric carcinogenesis.

The art of measuring gastrin in plasma: a dwindling diagnostic discipline?

The gastrointestinal hormone gastrin is measured in plasma in physiological, pathophysiological and diagnostic investigations. In the diagnosis of hypergastrinaemic diseases such as gastrinomas and gastric achlorhydria, measurement of gastrin concentrations in circulation is crucial. Gastrin circulates, however, not as a single peptide but as a mixture of peptides of different lengths and amino acid derivatizations. Moreover, in hypergastrinaemia the peptide pattern changes. Consequently, diagnostic gastrin measurements require immunoassays that recognize the pathological plasma patterns, which are characterized by a predominance of the large peptides (gastrin-34 and gastrin-71) and less, if any, of the shorter main form of gastrin in normal tissue, gastrin-17. Alternatively, and in specific cases, "processing-independent assays" (PIA) for progastrin may be considered, since hypersecreting gastrin cells also release substantial amounts of biosynthetic precursors and processing intermediates. Recently, gastrin kits that do not take the pathological plasma patterns into account have been marketed and may miss the diagnosis. Therefore, proper diagnosis of gastrinomas and other hypergastrinaemic diseases requires insight into cellular gastrin synthesis and peripheral metabolism, and also into the design of useful immunoassays. This review discusses the art of measuring gastrin in plasma with adequate diagnostic specificity.

Importance of gastrin in the pathogenesis and treatment of gastric tumors

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

A gastrin transcript expressed in gastrointestinal cancer cells contains an internal ribosome entry site

As the hormone gastrin promotes gastrointestinal (GI) cancer progression by triggering survival pathways, regulation of gastrin expression at the translational level was explored. Sequence within the 5' untranslated region of a gastrin transcript expressed in GI cancer cells was investigated, then cloned into a bicistronic vector upstream of firefly luciferase and transfected into a series of GI cancer cell lines. Firefly luciferase activity was measured relative to that of a cap-dependent Renilla luciferase. A gastrin transcript that was different from that described in Ensembl was expressed in GI cancer cells. Its transcription appears to be initiated within the region designated as the gene's first intron. In GI cancer cells transfected with the bicistronic construct, firefly luciferase activity increased 8-15-fold compared with the control vector, and there was a further induction of the signal (up to 25-fold) following exposure of the cells to genotoxic stress or hypoxia, suggesting that the sequence acts as an internal ribosome entry site. These data suggest that the gastrin transcript within GI cancer cells contains an internal ribosome entry site that may allow continued expression of gastrin peptides when normal translational mechanisms are inactive, such as in hypoxia, thereby promoting cancer cell survival.

Blockade of cholecystokinin-2 receptor and cyclooxygenase-2 synergistically induces cell apoptosis, and inhibits the proliferation of human gastric cancer cells in vitro

Gastrin and cyclooxygenase-2 (COX-2) play important roles in the carcinogenesis and progression of gastric cancer. However, it remains unknown whether the combination of cholecystokinin-2 (CCK-2) receptor antagonist plus COX-2 inhibitor exerts synergistic anti-tumor effects on human gastric cancer. Here, we demonstrated that the combination of AG-041R (a CCK-2 receptor antagonist) plus NS-398 (a selective COX-2 inhibitor) treatment had synergistic effects on proliferation inhibition, apoptosis induction, down-regulation of Bcl-2 and up-regulation of Bax expression in MKN-45 cells. These results indicate that simultaneous targeting of CCK-2 receptor and COX-2 may inhibit gastric cancer development more effectively than targeting either molecule alone.

Immunohistochemical study of enterochromaffin-like cell in human gastric mucosa

Enterochromaffin-like (ECL) cell has been identified as the histamine-containing argyrophil cell in rat gastric mucosa and vigorously studied. However, there are few reports of the distribution of ECL cell in human stomach. The aim of the present study was to determine the precise distribution of ECL cell by immunohistochemical staining of histidine decarboxylase (HDC) and gastrin-cholecystokinin B receptor (CCK-BR) in human stomach, and the correlation between their distribution and that of parietal cells. Thirty specimens of surgically resected stomach were used. Parietal cell, Grimelius-silver-positive cell, gastrin, HDC- and CCK-BR-immunoreactive cell were studied on continuous cell counting in the restricted field along the lamina muscularis from the oral to the anal ends. The percentage of HDC-immunoreactive cells of endocrine cells was smaller (15%) than that of a previous report (35%) in the fundic region. HDC- and CCK-BR-immunoreactive cells were found not only in the fundic region, but also in the intermediate and pyloric regions. In the pyloric region, HDC- and CCK-BR-immunoreactive cells were found mainly in the mucosa with intestinal metaplasia. Double-positive cells were also found, but only in small numbers. This suggests that ECL cell, or a cell sharing its function, is present in the pyloric region.

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.

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.

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.