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

Nonpeptidic Z360-Analogs Tagged with Trivalent Radiometals as Anti-CCK2R Cancer Theranostic Agents: A Preclinical Study

(1) Background: Theranostic approaches in the management of cholecystokinin subtype 2 receptor (CCK₂R)-positive tumors include radiolabeled gastrin and CCK motifs. Moving toward antagonist-based CCK₂R-radioligands instead, we herein present three analogs of the nonpeptidic CCK₂R-antagonist Z360, GAS1/2/3. Each was conjugated to a different chelator (DOTA, NODAGA or DOTAGA) for labeling with medically relevant trivalent radiometals (e.g., Ga-68, In-111, Lu-177) for potential use as anti-CCK₂R cancer agents; (2) Methods: The in vitro properties of the thee analogs were compared in stably transfected HEK293-CCK₂R cells. Biodistribution profiles were compared in SCID mice bearing twin HEK293-CCK₂R and wtHEK293 tumors; (3) Results: The GAS1/2/3 analogs displayed high CCK₂R-affinity (lower nM-range). The radioligands were fairly stable in vivo and selectively targeted the HEK293-CCK₂R, but not the CCK₂R-negative wtHEK293 tumors in mice. Their overall pharmacokinetic profile was found strongly dependent on the radiometal-chelate. Results could be visualized by SPECT/CT for the [¹¹¹In]In-analogs; (4) Conclusions: The present study highlighted the high impact of the radiometal-chelate on the end-pharmacokinetics of a new series of Z360-based radioligands, revealing candidates with promising properties for clinical translation. It also provided the impetus for the development of a new class of nonpeptidic radioligands for CCK₂R-targeted theranostics of human cancer.

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.

[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.

CCK2R antagonists: from SAR to clinical trials

The widespread involvement of the cholecystokinin-2/gastrin receptor (CCK₂R) in multiple (patho)physiological processes has propelled extensive searches for nonpeptide small-molecule CCK₂R antagonists. For the past three decades, considerable research has yielded numerous chemically heterogeneous compounds. None of these entered into the clinic, mainly because of inadequate biological effects. However, it appears that the ultimate goal of a clinically useful CCK₂R antagonist is now just around the corner, with the most promising compounds, netazepide and nastorazepide, now in Phase II clinical trials. Here, we illustrate the structure-activity relationships (SARs) of stablished CCK₂R antagonists of various structural classes, and the most recent proof-of-concept studies where new applicabilities of CCK₂R antagonists as visualizing agents are presented.

Targeting cholecystokinin-2 receptor for pancreatic cancer chemoprevention

Gastrin signaling mediated through cholecystokinin-2 receptor (CCK2R) and its downstream molecules is altered in pancreatic cancer. CCK2R antagonists, YF476 (netazepide) and JNJ-26070109, were tested systematically for their effect on pancreatic intraepithelial neoplasia (PanIN) progression to pancreatic ductal adenocarcinoma (PDAC) in Kras^G12D mice. After dose selection using wild-type mice, six-week-old p48^Cre/+ -LSL-Kras^G12D (22-24 per group) genetically engineered mice (GEM) were fed AIN-76A diets containing 0, 250, or 500 ppm JNJ-26070109 or YF-476 for 38 weeks. At termination, pancreata were collected, weighed, and evaluated for PanINs and PDAC. Results demonstrated that control-diet-fed mice showed 69% (males) and 33% (females) incidence of PDAC. Administration of low and high dose JNJ-26070109 inhibited the incidence of PDAC by 88% and 71% (P < .004) in male mice and by 100% and 24% (P > .05) in female mice, respectively. Low and high dose YF476 inhibited the incidence of PDAC by 74% (P < .02) and 69% (P < .02) in male mice and by 45% and 33% (P > .05) in female mice, respectively. Further, transcriptome analysis showed downregulation of Cldn1, Sstr1, Apod, Gkn1, Siglech, Cyp2c44, Bnc1, Fmo2, 623169, Kcne4, Slc27a6, Cma1, Rho GTPase activating protein 18, and Gpr85 genes in JNJ-26070109-treated mice compared with untreated mice. YF476-treated mouse pancreas showed downregulation of Riks, Zpbp, Ntf3, Lrrn4, Aass, Skint3, Kcnb1, Dgkb, Ddx60, and Aspn gene expressions compared with untreated mouse pancreas. Overall, JNJ-26070109 showed better chemopreventive efficacy than YF476. However, caution is recommended when selecting doses, as the agents appeared to exhibit gender-specific effects.

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.

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.

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.

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.

CCK-2/gastrin receptor signaling pathway is significant for gemcitabine-induced gene expression of VEGF in pancreatic carcinoma cells

AIMS

As activation and overexpression of the cholecystokinin-2 (CCK-2)/gastrin receptor can lead to carcinogenesis, it has been explored as a therapeutic target in pancreatic cancer. We demonstrated that Z-360, a CCK-2/gastrin receptor antagonist, combined with gemcitabine prolonged survival and reduced gemcitabine-induced vascular endothelial growth factor (VEGF) expression in a pancreatic carcinoma orthotopic xenograft mouse. In this study, we investigated the role of the CCK-2/gastrin signaling pathway on gemcitabine-induced VEGF expression in PANC-1 human pancreatic carcinoma cells.

MAIN METHODS

In PANC-1 cells treated with Z-360, anti-gastrin IgG or kinase inhibitors, the gene expression levels were analyzed by quantitative real-time RT-PCR, and the protein levels of Akt and phosphorylated Akt (p-Akt) in cellular extracts were measured by ELISA.

KEY FINDINGS

Gemcitabine-induced expression of VEGF and hypoxia-inducible factor-1 alpha (HIF-1 alpha) were suppressed by the treatment with an anti-gastrin antibody. In addition, VEGF and HIF-1 alpha gene expression was inhibited by treatment with an inhibitor of phosphatidylinositol 3-kinase (PI3K), which is involved in the downstream signaling pathway of the CCK-2/gastrin receptor, and was also suppressed by treatment with Z-360. Moreover, although Akt phosphorylation was increased by treatment with gemcitabine, this elevation was partially, but significantly, inhibited by an exposure of Z-360.

SIGNIFICANCE

Gemcitabine might induce gene expression of VEGF via the PI3K/Akt signaling pathway in the downstream of the CCK-2/gastrin receptor. The suppression of the CCK-2/gastrin signaling pathway by treatment with Z-360 could be a useful approach for potentiating prolonged survival of pancreatic cancer patients receiving gemcitabine therapy.

Z-360, a novel therapeutic agent for pancreatic cancer, prevents up-regulation of ephrin B1 gene expression and phosphorylation of NR2B via suppression of interleukin-1 β production in a cancer-induced pain model in mice

BACKGROUND

Z-360 is an orally active cholecystokinin-2 (CCK2)/gastrin receptor antagonist currently under development as a therapeutic drug for pancreatic cancer. It was previously reported that Z-360 treatment in combination with gemcitabine prolonged the survival period in a lethal pancreatic cancer xenograft model in mice. In a phase Ib/IIa clinical study, Z-360 treatment displayed a trend of reduced pain in patients with advanced pancreatic cancer in combination with gemcitabine including analgesics such as opioids. Here, we investigated the mechanism of analgesic action of Z-360 in a severe cancer-induced pain model in mice, which is considered to be opioid-resistant, by examining ephrin B1 gene expression, N-methyl-D-aspartate receptor NR2B subunit phosphorylation, and interleukin-1β (IL-1β) production.

RESULTS

In a mouse model of cancer-induced pain, ephrin B1 gene expression in dorsal root ganglia (DRGs) and the phosphorylation of NR2B in the spinal cord were induced. Z-360 treatment inhibited both ephrin B1 gene expression and the phosphorylation of NR2B. In addition, IL-1β production increased in the cancer-inoculated hind paw of mice, but could be suppressed by treatment with Z-360. Moreover, we observed that the CCK1 receptor antagonist devazepide similarly suppressed up-regulation of ephrin B1 gene expression and IL-1β production, and that the intraperitoneal injection of sulfated CCK-8 induced the production of IL-1β in the cancer-inoculated region.

CONCLUSIONS

We have identified a novel pain cascade, in which IL-1β production in cancer-inoculated regions induces ephrin B1 gene expression in DRGs and then ephrin B1 enhances the tyrosine phosphorylation of NR2B via Eph B receptor in the spinal cord. Notably, Z-360 relieves cancer-induced pain by preventing this pain cascade through the suppression of IL-1β production, likely via the blockade of CCK1 receptor. The pre-clinical results presented here support the analgesic action of Z-360 in pancreatic cancer patients with severe, opioid-resistant pain. Pre-clinical and clinical results have demonstrated that Z-360 combined with gemcitabine represents a promising pancreatic cancer therapy approach with characteristic analgesic effects in addition to the prolongation of survival.

Pharmacological evaluation of analgesic effects of the cholecystokinin2 receptor antagonist Z-360 in mouse models of formalin- and cancer-induced pain

Z-360, a novel cholecystokinin(2) (CCK(2)) receptor antagonist, has been developed as a therapeutic drug for pancreatic cancer and showed pain relief action in phase Ib/IIa clinical trial. This study was attempted to elucidate the analgesic efficacy of Z-360 in mice. Oral administration of Z-360 (30-300 mg/kg) showed a dose-dependent inhibitory effect on the late phase of nociceptive responses to formalin. YF476, another CCK(2) receptor antagonist, was without effects at 1 and 10 mg/kg. In contrast, the CCK(1) receptor antagonist devazepide inhibited the nociceptive responses to formalin. In a mouse model of cancer pain, significant anti-allodynic effect of Z-360 was observed after single and repeated oral administration of 100 and 300 mg/kg doses. Anti-allodynic effect was also observed after repeated administration of devazepide. Combined single treatment with morphine and Z-360 caused an increase inhibition of pain-related responses in the pain models produced by formalin and cancer. Although Z-360 has lower affinity for CCK(1) receptor than for CCK(2) receptor, Z-360 exhibited an inhibitory effect on sulfated CCK-8-induced gallbladder emptying, a CCK(1) receptor-mediated effect, at a dose of 100 mg/kg. These results suggest that Z-360 inhibits inflammatory and cancer pain probably through the blockade of CCK(1) receptors. Z-360 is expected to become a useful drug for the pancreatic cancer with analgesic effects as well as the prolongation of survival.

Z-360, a novel cholecystokinin-2/gastrin receptor antagonist, inhibits gemcitabine-induced expression of the vascular endothelial growth factor gene in human pancreatic cancer cells

Z-360 is a novel cholecystokinin (CCK)-2/gastrin receptor antagonist that is being developed for the treatment of pancreatic adenocarcinoma in combination with gemcitabine. A previous study shows that the co-administration of Z-360 with gemcitabine significantly prolonged the survival of mice with orthotopically implanted human pancreatic adenocarcinoma cell lines. To clarify the therapeutic effects of Z-360 in combined with gemcitabine, we analyzed gene expression. When gemcitabine was administered, CCK-2/gastrin receptor expression was induced in an orthotropic xenograft model; the result indicating that Z-360 could act on gemcitabine-sensitive cells. Both in vitro and in vivo studies showed that gemcitabine increased the expression of vascular endothelial growth factor A (VEGFA), a prognostic factor for survival in pancreatic cancer, while Z-360 suppressed this induction of VEGFA gene expression. These results help to explain how Z-360 prolongs survival when used in combination with gemcitabine.

Inactivating cholecystokinin-2 receptor inhibits progastrin-dependent colonic crypt fission, proliferation, and colorectal cancer in mice

Hyperproliferation of the colonic epithelium, leading to expansion of colonic crypt progenitors, is a recognized risk factor for colorectal cancer. Overexpression of progastrin, a nonamidated and incompletely processed product of the gastrin gene, has been shown to induce colonic hyperproliferation and promote colorectal cancer in mice, but the mechanism of pathogenesis has not been defined. Cholecystokinin-2 receptor (CCK2R) is the primary receptor for cholecystokinin (CCK) and amidated gastrin. Here, we show that Cck2r was expressed in murine colonic crypts and upregulated in the transgenic mice that overexpress human progastrin. Murine deletion of Cck2r abrogated progastrin-dependent increases in colonic proliferation, mucosal thickness, and beta-catenin and CD44 expression in the colon tumor. In addition, either deletion or antagonism of Cck2r resulted in the inhibition of progastrin-dependent increases in progenitors expressing doublecortin and CaM kinase-like-1 (DCAMKL1), stem cells expressing leucine rich repeat-containing G protein-coupled receptor 5 (LgR5), and colonic crypt fission. Furthermore, in the azoxymethane mouse model of colorectal carcinogenesis, Cck2r deletion in human progastrin-overexpressing mice resulted in markedly decreased aberrant crypt foci formation and substantially reduced tumor size and multiplicity. Taken together, these observations indicate that progastrin induces proliferative effects, primarily in colonic progenitor cells, through a CCK2R-dependent pathway. Moreover, our data suggest that CCK2R may be a potential target in the treatment or prevention of colorectal cancer.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effect of Z-360, a novel orally active CCK-2/gastrin receptor antagonist on tumor growth in human pancreatic adenocarcinoma cell lines in vivo and mode of action determinations in vitro

PURPOSE

Gastrin is known to enhance the growth of pancreatic carcinoma via the cholecystokinin (CCK)-2/gastrin receptor. We investigated the anti-tumor effect of Z-360 (calcium bis [(R)-(-)-3-[3-{5-cyclohexyl-1-(3,3-dimethyl-2-oxo-butyl)-2-oxo-2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepin-3-yl}ureido]benzoate]), a novel orally active CCK-2 receptor antagonist alone or combined with the chemotherapeutic agent, gemcitabine in human pancreatic adenocarcinoma cell lines.

RESULTS

Z-360 potently inhibited specific binding of [3H]CCK-8 to the human CCK-2 receptor, with a Ki value of 0.47 nmol/l, and showed antagonistic activity for this receptor. The anti-tumor effect of Z-360 alone or combined with gemcitabine was assessed using subcutaneous xenografts of MiaPaCa2 and PANC-1 and an orthotopic xenograft model (PANC-1). Oral administration of Z-360 significantly inhibited the growth of MiaPaCa2 (41.7% inhibition at 100 mg/kg, P<0.01). Combined administration of Z-360 and gemcitabine significantly inhibited subcutaneous PANC-1 tumor growth compared with either agent alone (27.1% inhibition compared to effect with gemcitabine, P<0.05), and significantly prolonged survival compared with the vehicle control (median survival of 49 days in vehicle compared to 57 days in the combination group, P<0.05). In vitro studies showed that Z-360 significantly inhibited gastrin-induced proliferation of human CCK-2 receptor-expressing cells, and also significantly reduced gastrin-induced PKB/Akt phosphorylation to the level of untreated controls.

CONCLUSION

In the present study, we have shown that Z-360 combined with gemcitabine can inhibit pancreatic tumor growth and prolong survival in a pancreatic carcinoma xenograft model, on a possible mode of action being the inhibition of gastrin-induced PKB/Akt phosphorylation through blockade of the CCK-2 receptor. Our results suggest that Z-360 may be a useful adjunct to gemcitabine for the treatment of pancreatic carcinoma and a therapeutic option for patients with advanced pancreatic cancer.