Differential expression of gastrin, cholecystokinin-A and cholecystokinin-B receptor mRNA in human pancreatic cancer cell lines

Advances in Immunotherapeutics in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) accounts for up to 95% of all pancreatic cancer cases and is the seventh-leading cause of cancer death. Poor prognosis is a result of late presentation, a lack of screening tests and the fact some patients develop resistance to chemotherapy and radiotherapy. Novel therapies like immunotherapeutics have been of recent interest in pancreatic cancer. However, this field remains in its infancy with much to unravel. Immunotherapy and other targeted therapies have yet to yield significant progress in treating PDAC, primarily due to our limited understanding of the disease immune mechanisms and its intricate interactions with the tumour microenvironment (TME). In this review we provide an overview of current novel immunotherapies which have been studied in the field of pancreatic cancer. We discuss their mechanisms, evidence available in pancreatic cancer as well as the limitations of such therapies. We showcase the potential role of combining novel therapies in PDAC, postulate their potential clinical implications and the hurdles associated with their use in PDAC. Therapies discussed with include programmed death checkpoint inhibitors, Cytotoxic T-lymphocyte-associated protein 4, Chimeric Antigen Receptor-T cell therapy, oncolytic viral therapy and vaccine therapies including KRAS vaccines, Telomerase vaccines, Gastrin Vaccines, Survivin-targeting vaccines, Heat-shock protein (HSP) peptide complex-based vaccines, MUC-1 targeting vaccines, Listeria based vaccines and Dendritic cell-based vaccines.

Advances in Targeted Therapy and Immunotherapy for Pancreatic Cancer

Pancreatic cancer is a highly aggressive malignancy with an overall 5-year survival rate of <6% due to therapeutic resistance and late-stage diagnosis. These statistics have not changed despite 50 years of research and therapeutic development. Pancreatic cancer is predicted to become the second leading cause of cancer mortality by the year 2030. Currently, the treatment options for pancreatic cancer are limited. This disease is usually diagnosed at a late stage, which prevents curative surgical resection. Chemotherapy is the most frequently used approach for pancreatic cancer treatment and has limited effects. In many other cancer types, targeted therapy and immunotherapy have made great progress and have been shown to be very promising prospects; these treatments also provide hope for pancreatic cancer. The need for research on targeted therapy and immunotherapy is pressing due to the poor prognosis of pancreatic cancer, and in recent years, there have been some breakthroughs for targeted therapy and immunotherapy in pancreatic cancer. This review summarizes the current preclinical and clinical studies of targeted therapy and immunotherapy for pancreatic cancer and ends by describing the challenges and outlook.

Pancreatic cancer: Update on immunotherapies and algenpantucel-L

Pancreatic adenocarcinoma is notoriously lethal, and despite improvements in systemic chemotherapy approaches bringing survival rates for metastatic disease to almost 1 year, by 2030 it is expected to become the second leading cause of cancer death. Pancreatic cancer (PC) prognosis has been associated with both the presence of intratumoral helper and cytotoxic T lymphocytes, as well as humoral immune responses to tumor associated antigens like mesothelin. It is well described that the PC microenvironment is characterized by a fibroinflammatory and immunosuppressive stroma. On these premises several immune-targeted strategies have been developed to harness the adaptable immune system with a goal of improving survival with little toxicity. Cancer vaccines involve the administration of tumor-associated antigens with the goal of inducing an endogenous anti-tumor response. Among several strategies discussed, we will focus on the algenpantucel-L (HyperAcute™ Pancreas) immunotherapy. Algenpantucel-L is a whole cell immunotherapy consisting of irradiated allogeneic PC cells genetically engineered to express the murine enzyme α(1,3)-galactosyltransferase (αGT), which ultimately leads to hyperacute rejection with complement- and antibody-dependent cytotoxicity. While phase III data in the adjuvant treatment of pancreatic cancer are pending, phase II results have been encouraging, particularly for patients who demonstrated humoral immunologic responses. Novel strategies using immune checkpoint inhibitors, costimulatory antibodies, and combinations with cancer vaccines may overcome immunotolerance and improve treatment success.

Pancreatic cancer: role of the immune system in cancer progression and vaccine-based immunotherapy

Pancreatic cancer (PC) is the 5th leading cause of cancer related death in the developed world with more than 260,000 deaths annually worldwide and with a dismal 5-year survival. Surgery is the only potential hope of cure for PC, but, unfortunately, only 20% PC patients is resectable at the time of diagnosis. Therapeutic research efforts have mainly focused on improvements in radio/ chemo treatments and to date, there are only a few chemotherapeutic agents that have shown to be effective against PC, including gemcitabine with or without abraxane as well as a combination of 5-FU, leucovorin, oxaliplatin and irinotecan (the so-called FOLFIRINOX regimen). The survival of patients treated with these regimens is marginal and hence we are in urgent need of novel therapeutic approaches to treat pancreatic cancer. The success of immunotherapeutic strategies in other cancers and various evidences that pancreatic adenocarcinoma elicits antitumor immune responses, suggest that immunotherapies can be a promising alternative treatment modality for this deadly disease. PC immunotherapy treatments include passive immunotherapeutic approaches, such as the use of effector cells generated in vitro, and active immunotherapeutic strategies, which goal is to stimulate an antitumor response in vivo, by means of vaccination. In this review, we describe the immune suppressive mechanisms of pancreatic cancer and discuss recent preclinical and clinical efforts toward PC immunotherapy, including passive approaches, such as the use of antibodies and active strategies (vaccination), with a special mention of most recent treatment with CRS-207 and GVAX.

Diagnosis of pernicious anemia and the risk of pancreatic cancer

OBJECTIVES

A number of studies have demonstrated a trophic effect of gastrin on pancreatic cancer cells in vitro. Pernicious anemia (PA) is a clinical condition characterized by chronic hypergastrinemia. The aim of this study was to determine if PA is a risk factor for pancreatic cancer.

METHODS

This study is a retrospective cohort study using The Health Improvement Network database, which contains comprehensive health information on 7.5 million patients in the United Kingdom from 1993 to 2009. All patients with PA in the study cohort were identified and composed of the exposed group. Each exposed patient was matched on practice site, sex, and age with up to 4 unexposed patients without PA. The outcome was incident pancreatic cancer. The hazard ratio and 95% confidence intervals were estimated using multivariable Cox regression analysis.

RESULTS

We identified 15,324 patients with PA and 55,094 unexposed patients. Mean follow-up time was similar between groups (exposed 4.31 [SD, 3.38] years, unexposed 4.63 [SD, 3.44] years). The multivariable adjusted hazard ratio for pancreatic cancer associated with PA was 1.16 (95% confidence interval, 0.77-1.76; P = 0.47).

CONCLUSIONS

There is no significant association between PA and the risk of pancreatic cancer.

Vaccine therapy for pancreatic cancer

Pancreatic cancer is a lethal disease and currently available therapies have significant limitations. Pancreatic cancer is thus an ideal setting for the development of novel treatment modalities such as immunotherapy. However, relevant obstacles must be overcome for immunotherapeutic regimens against pancreatic cancer to be successful. Vaccine therapy relies on the administration of biological preparations that include an antigen that (at least ideally) is specifically expressed by malignant cells, boosting the natural ability of the immune system to react against neoplastic cells. There are a number of ways to deliver anticancer vaccines. Potent vaccines stimulate antigen presentation by dendritic cells, hence driving the expansion of antigen-specific effector and memory T cells. Unlike vaccines given as a prophylaxis against infectious diseases, anticancer vaccines require the concurrent administration of agents that interfere with the natural predisposition of tumors to drive immunosuppression. The safety and efficacy of vaccines against pancreatic cancer are nowadays being tested in early phase clinical trials.

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.

An international multicenter randomized controlled trial of G17DT in patients with pancreatic cancer

OBJECTIVES

This study aimed to investigate G17DT, an immunogen producing neutralizing antibodies against the tumor growth factors amidated and glycine-extended forms of gastrin-17, in the treatment of pancreatic cancer.

METHODS

A randomized, double-blind, placebo-controlled, group-sequential multicenter trial of G17DT in patients with advanced pancreatic cancer unsuitable for or unwilling to take chemotherapy. Inclusion criteria were a Karnofsky performance score of 60 or higher and a life expectancy of more than 2 months. Patients received G17DT or placebo emulsion at weeks 0, 1, 3, 24, and 52. The primary end point was survival, and secondary end points were tolerability, Karnofsky performance.

RESULTS

A total of 154 patients were recruited: 79 G17DT and 75 placebo. A final analysis of the intention-to-treat population, using a proportional hazards model, stratifying by disease stage and adjusting for interim analysis, gave a hazard ratio for mortality of 0.75 (95% confidence interval, 0.51-1.10, P = 0.138; G17DT/placebo). A conventional analysis without adjustment for disease stage or interim analysis, censoring for chemotherapy and excluding protocol violators, gave median survival periods of 151 (G17DT) and 82 days (placebo) (log-rank test, P = 0.03).Patients developing anti-G17DT responses (73.8%) survived longer than nonresponders or those on placebo (median survival, 176 vs 63 vs 83; log-rank test, P = 0.003). G17DT was well tolerated.

Expression of multiple forms of 3'-end variant CCK2 receptor mRNAs in human pancreatic adenocarcinomas

Background

Two main types of receptors for gastrin and cholecystokinin (CCK) have been cloned and identified. CCK1 (CCK-A) receptors are expressed in the pancreas, the gallbladder, and parts of the brain, while CCK2 (CCK-B/gastrin) receptors (CCK2R) are expressed in gastric glands and in most of the brain. A splice variant of the CCK2R designated CCKRi4sv (CCK-C), which is constitutively expressed in human pancreatic cancer cells, has also been described. The purpose of the present investigation was to study CCK2R, CCK2i4svR, and gastrin mRNA expression in human pancreatic adenocarcinoma on the assumption that co-expression of CCK2R and gastrin or constitutive CCK2i4svR mRNA expression plays a pivotal role in the progression of pancreatic cancer.

Findings

PCR amplification using CCK2R specific primer-pairs, followed by ethidium-bromide stained agarose gel electrophoresis revealed the expression of wild-type CCK2R mRNA in 12 of 17 biopsy specimens. A CCK2R intron 4 specific nested PCR assay revealed that CCK2i4svR mRNA was expressed in only one of the biopsy specimen. The authenticity of PCR amplicons was confirmed by cloning of selected amplicons and DNA sequence analysis. Moreover, we found that hitherto undescribed multiple forms of 3'-end variant CCK2R mRNAs with various deletions in the retained intron 4 and exon 5, tentatively generating truncated proteins, were expressed in the pancreatic adenocarcinomas.

Conclusion

Cloning and DNA sequencing of selected amplicons revealed that CCK2R and multiple CCK2i4svR-like mRNAs are expressed in human pancreatic adenocarcinoma. The originally described CCK2i4svR mRNA was only expressed in one of 17 tumours and appears to be rarely expressed in pancreatic adenocarcinoma. We report that CCK2R- and gastrin mRNA co-expression may play a role in a portion, but not in all of these tumours, and that aberrant splicing takes places in these tissues generating multiple forms of 3'-end variant CCK2R mRNAs.

Inhibition of COX-2 and activation of peroxisome proliferator-activated receptor gamma synergistically inhibits proliferation and induces apoptosis of human pancreatic carcinoma cells

Although inhibition of cyclooxygenase-2 (COX-2) or activation of peroxisome proliferators-activated receptor gamma (PPAR-gamma) leads to growth inhibition in malignancies, the synergistic anti-tumor effects of combination of COX-2 inhibitor (NS-398) and PPAR-gamma agonist (rosiglitazone) on the human pancreatic cancer cells remains unknown. Here, we evaluated the effects of NS-398 and/or rosiglitazone on the cell proliferation and apoptosis in a pancreatic cancer cell line, SW1990. NS-398 and rosiglitazone decreased cell proliferation in a dose- and time-dependent manner. Proliferating cell nuclear antigen (PCNA) labeling index significantly decreased in the cells treated with either NS-398 or rosiglitazone. Both NS-398 and rosiglitazone alone induced apoptotic cell death of SW1990. The combination of NS-398 and rosiglitazone exerted synergistic effects on proliferation inhibition, and apoptosis induction in SW1990 cells, with down-regulation of Bcl-2 and up-regulation of Bax expression. Our results indicate that simultaneous targeting of COX-2 and PPAR-gamma inhibits pancreatic cancer development more effectively than targeting each molecule alone.

Cholecystokinin octapeptide improves cardiac function by activating cholecystokinin octapeptide receptor in endotoxic shock rats

AIM: To explore the effect of sulfated cholecystokinin octapeptide (sCCK-8) on cardiac functions and its receptor mechanism in endotoxic shock (ES) rats.

METHODS: The changes of the mean arterial pressure (MAP), heart rate (HR), the left ventricular pressure (LVP) and the maximal/minimum rate of LVP (±LVdp/dt_max)) were measured by using physiological record instrument in eight groups of rats. The expression of cholecystokinin-A receptor (CCK-AR) and cholecystokinin-B receptor (CCK-BR) mRNA of myocardium in ES rats was examined by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: (1) Low doses of sCCK-8 (0.4 μg/kg) caused tachycardia (441±27, normal control 391±22 s/min) and slight increase in MAP, LVP and ±LVdp/dt_max (16.96±1.79, 18.21±1.69 and +768.85±31.28/-565.04±27.71 kPa, respectively, all P<0.01), while medium doses (4.0 μg/kg) and high doses of sCCK-8 (40 μg/kg) elicited bradycardia and marked increase in MAP, LVP and ±LVdp/dt_max (17.29±1.63, 19.46±2.57 and +831.46±22.57/-606.08 ±31.32; 17.46±1.08, 19.83±2.91 and +914.52±35.95/-639.15±30.23 kPa, respectively, all P<0.01). Proglumide (1.0 mg/kg), a nonselective antagonist of CCK-receptor (CCK-R), significantly inhibited the pressor effects of sCCK-8 (15.96±1.38, 17.36±0.66 and +748.18±19.29/-512.12±14.39 kPa, respectively, all P<0.01), whilst reversing the bradycardiac responses. (2) High doses of LPS (8 mg/kg) elicited marked decrease in MAP, LVP and ±LVdp/dt_max. (7.16±0.59, 7.6±0.68 and +298.01±25.52/-166.96±19.25 kPa, respectively, all P<0.01). Pretreatment with sCCK-8 (40 μg/kg) could reverse the decline of cardiac functions (10.71±0.45, 11.7±1.26 and +446.04±67.18/-347.90±36.98 kPa, respectively, all P<0.01), while proglumide could cause further decline of cardiac function in ES rats (4.71±0.67, 5.58±1.25 and +226.48±15.84/-142.83±20.23 kPa, respectively, all P<0.01). (3) CCK-A/BR mRNAs were expressed in myocardium of control rats. Gene expression of CCK-AR and CCK-BR significantly increased in myocardium of ES rats. The increase of CCK-AR mRNA induced by LPS began at 0.5 h, peaked at 2 h, kept a high level at 6 h and declined at 12 h, respectively. Similar to CCK-AR mRNA, the expression of CCK-BR mRNA peaked at 2 h and kept a high level at 6 h, but it did not change at the first 0.5 h and was stable at a high level at 12 h.

CONCLUSION: The above results indicate that endogenous and exogenous sCCK-8 may significantly improve cardiac function and intractable hypotension of ES rats, which was likely related to high expression of CCK-A/BR in myocardium induced by LPS.

The functional significance of the cholecystokinin-C (CCK-C) receptor in human pancreatic cancer

OBJECTIVES

The aim of this study was to evaluate whether the CCK-C receptor, a splice variant of the CCK-B receptor, in human pancreatic cancer cells was associated with accelerated cancer cell growth.

METHODS

In vitro, BxPC-3 cells were transfected with the antisense cDNA for the CCK-C receptor and growth of transfected cells was compared with that of wild-type (WT) and empty vector (EV)-transfected cells; expression was confirmed by RT-PCR and immunocytochemistry. In vivo, athymic nude mice bearing human BxPC-3 pancreatic cancers were treated for 28 days with either an antisense oligonucleotide specific to the CCK-C receptor, the same nucleotide sequence arranged in a scrambled fashion (nucleotide control), or vehicle (control).

RESULTS

In culture, BxPC-3 cells transfected with the antisense cDNA for the CCK-C receptor were reduced in cell number 65% compared with WT and EV-transfected cell cultures at 6 days; this difference was statistically significant (P = 0.002). Transfected cells did not respond to exogenous gastrin with growth as did WT cells. Tumors of mice treated with the antisense oligonucleotide for CCK-C were 75% smaller in volume and 83% reduced in weight (P = 0.03) compared with the control tumors.

CONCLUSION

These studies indicate that the CCK-C receptor is functional and plays a crucial role in growth of human pancreatic cancer.

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

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

Gastrins, cholecystokinins and gastrointestinal cancer

The gastrointestinal peptide hormones gastrin and cholecystokinin (CCK) are well known for their ability to stimulate gastric acid secretion and pancreatic enzyme secretion, respectively. The suggestion that gastrin and CCK might also promote the development of cancers of the gastrointestinal tract has been controversial, but an increasing body of evidence now supports the view that the amidated and non-amidated forms of gastrin act as growth factors via different receptors in different regions of the gut. For example, animal experiments indicate that amidated gastrins are involved in cellular differentiation and repair in the gastric mucosa, and synergize with Helicobacter pylori infection in the development of gastric carcinoma. In contrast, non-amidated gastrins stimulate colonic mucosal growth, accelerate the early steps in colorectal carcinoma formation, and are elevated in the tumour and circulation of patients with colorectal cancer. Although human pancreatic carcinomas express CCK-1 and CCK-2 receptors, the role of gastrins and CCK in pancreatic carcinogenesis is yet to be established. Further investigation of the possible role of the CCK-2 receptor in gastric and pancreatic neoplasia, and of the hypothesis that gastrin precursors act as autocrine growth factors in colorectal carcinoma, is warranted. However, therapies aimed at the gastrins must be targeted to the relevant gastrin/gastrin receptor combination.

K-ras and B-raf gene mutations are not associated with gastrin- and CCK2-receptor mRNA expression in human colorectal tumour tissues

BACKGROUND

Colorectal cancer is a multistep process caused by genetic alterations in cell growth regulatory genes such as K-ras and B-raf. It has been assumed that mutations in the K-ras gene induce gastrin gene expression and that gastrin stimulates the growth of colorectal cancer in an autocrine fashion by coexpressing gastrin and cholecystokinin (CCK)2 receptors. The aim of this study was to examine a possible association of K-ras and B-raf gene mutations with gastrin and CCK2 receptor mRNA expression in human colon and rectum tumour biopsy specimens.

METHODS

K-ras and B-raf gene mutations as well as gastrin and CCK2 receptor mRNA expression in 50 colon and 46 rectum biopsies, respectively, were determined using molecular biology methods.

RESULTS

K-ras mutations occurred in 44% colon and 30% rectum and B-raf mutations in 16% colon and 4% rectum tumours, respectively. Gastrin mRNA was expressed in 64% colon and 61% rectum tumours, whereas CCK2 receptor mRNAs was expressed in 32% colon and 13% rectum tumours. K-ras or B-raf gene mutations and simultaneous gastrin mRNA expression was observed in 40% colon and 17% rectum tumours, respectively. Co-expression of gastrin and CCK2 receptor mRNA occurred in 20% colon and 9% rectal tumours.

CONCLUSIONS

The results do not support the hypothesis that K-ras and B-raf gene mutations have an impact on gastrin- and CCK-receptor mRNA expression in colorectal tumour tissues.

Involvement of cholecystokinin/gastrin-related peptides and their receptors in clinical gastrointestinal disorders

In this paper the possible roles of cholecystokinin (CCK), gastrin, or gastrin-related peptides and their receptors in human gastrointestinal diseases are reviewed. For CCK/CCK(A) receptors (CCK(A)-R), the evidence for their proposed involvement in diseases caused by impaired CCK release or CCK(A)-R mutations, pancreatic disorders (acute/chronic pancreatitis), gastrointestinal motility disorders (gallbladder disease, irritable bowel syndrome), pancreatic tumor growth and satiety disorders, is briefly reviewed. The evidence that has established the involvement of gastrin/CCK(B)-R in mediating the action of hypergastrinaemic disorders, mediating hypergastrinaemic effects on the gastric mucosa (ECL hyperplasia, carcinoids, parietal cell mass), and acid-peptic diseases, is reviewed. The evidence for their possible involvement in mediating growth of gastric and pancreatic tumours and possible involvement of gastrin-related peptides in colon cancers, is reviewed briefly.

Gastrin, somatostatin, G and D cells of gastric ulcer in rats

AIM: To investigate the relationship among gastrin, somatostatin, G and D cells in gastric ulcer and in its healing process in rats.

METHODS: Fourty-nine Wistar rats were divided into 7 groups. The gastric ulcer model was induced by acetic acid successfully. The gastrin and the somatostatin in rat plasma, gastric fluid and antral tissue were measured by radioimmunoassay (RIA). G and D cells in antral mucosa were analyzed with polyclonal antibody of gastrin and somatostatin by immunohistochemical method and Quantimet 500 image analysis system.

RESULTS: In gastric ulcer, the level of gastrin in plasma, gastric fluid, and antral tissue increased, that of somatostatin declined, and the disorder gradually recovered to the normal level in the healing process. Immunohistochemical technique of G and D cells in antral mucosa demonstrated that the number of G cells increased and that of D cells decreased, both areas of G and D cells declined, the ratio of number and area of G/D increased in gastric ulcer, and the disorder gradually recovered in the healing process.

CONCLUSION: In gastric ulcer, the increased gastrin secreted by G cells, the declined somatostatin secreted by D cells, and the disordered G/D cell ratio can lead to gastrointestinal dysfunction.