The Nonpeptide Agonist MK-5046 Functions As an Allosteric Agonist for the Bombesin Receptor Subtype-3.

Allosteric ligands of various G-protein-coupled receptors are being increasingly described and are providing important advances in the development of ligands with novel selectivity and efficacy. These unusual properties allow expanded opportunities for pharmacologic studies and treatment. Unfortunately, no allosteric ligands are yet described for the bombesin receptor family (BnRs), which are proposed to be involved in numerous physiologic/pathophysiological processes in both the central nervous system and peripheral tissues. In this study, we investigate the possibility that the bombesin receptor subtype-3 (BRS-3) specific nonpeptide receptor agonist MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-[[1-(trifluoromethyl)cyclopropyl]methyl]-1H-imidazol-2-yl)propan-2-ol] functions as a BRS-3 allosteric receptor ligand. We find that in BRS-3 cells, MK-5046 only partially inhibits iodine-125 radionuclide (125I)-Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3-dimethylamino) benzylamide N-methylammonium trifluoroacetate] binding and that both peptide-1 (a universal BnR-agonist) and MK-5046 activate phospholipase C; however, the specific BRS-3 peptide antagonist Bantag-1 inhibits the action of peptide-1 competitively, whereas for MK-5046 the inhibition is noncompetitive and yields a curvilinear Schild plot. Furthermore, MK-5046 shows other allosteric behaviors, including slowing dissociation of the BRS-3 receptor ligand 125I-Bantag-1, dose-inhibition curves being markedly affected by increasing ligand concentration, and MK-5046 leftward shifting the peptide-1 agonist dose-response curve. Lastly, receptor chimeric studies and site-directed mutagenesis provide evidence that MK-5046 and Bantag-1 have different binding sites determining their receptor high affinity/selectivity. These results provide evidence that MK-5046 is functioning as an allosteric agonist at the BRS-3 receptor, which is the first allosteric ligand described for this family of receptors. SIGNIFICANCE STATEMENT: G-protein-coupled receptor allosteric ligands providing higher selectivity, selective efficacy, and safety that cannot be obtained using usual orthosteric receptor-based strategies are being increasingly described, resulting in enhanced usefulness in exploring receptor function and in treatment. No allosteric ligands exist for any of the mammalian bombesin receptor (BnR) family. Here we provide evidence for the first such example of a BnR allosteric ligand by showing that MK-5046, a nonpeptide agonist for bombesin receptor subtype-3, is functioning as an allosteric agonist.

Validity of Secretin Stimulation Testing on Proton Pump Inhibitor Therapy for Diagnosis of Zollinger-Ellison Syndrome.

INTRODUCTION: Zollinger-Ellison syndrome (ZES) is characterized by gastrinoma-induced hypergastrinemia causing excessive gastric acid secretion. Secretin stimulation tests (SSTs) are required for diagnosis in the majority of patients. Two case reports suggest that proton pump inhibitors (PPIs) cause false SST results. Consequently, PPIs are discontinued to allow hyperchlorhydria to recur; however, uncontrolled acidity can cause life-threatening complications in those with underlying undiagnosed ZES. The aim of this study was to determine whether PPIs influence the validity of SSTs for the diagnosis of ZES. METHODS: A retrospective chart review was performed. Charts of patients who underwent SSTs were reviewed to determine whether they were performed on or off PPI and the test's accuracy by comparing the results with gold standard tests (diagnostic laboratory testing performed off PPI or surgical pathology consistent with gastrinoma). Sensitivity, specificity, and positive predictive value (PPV) of SST on PPI were calculated and results compared with SST off PPI using noninferiority analyses. RESULTS: Twenty-eight patients corresponding to 29 SSTs were performed on PPI, and 70 patients corresponding to 107 SSTs were performed off PPI. Most of them were female and white and had multiple endocrine neoplasia type 1. We found no false-positive or false-negative SSTs on PPI. Sensitivity, specificity, and PPV of SSTs on PPI were determined to be noninferior to SSTs off PPI (P ≤ 0.05 for all). DISCUSSION: In our cohort, SSTs on PPI compared with SSTs off PPI were noninferior for sensitivity, specificity, and PPV. These results suggest that PPI withdrawal before SSTs may not be necessary.

Multiple Endocrine Neoplasia Type 1 and the Pancreas: Diagnosis and Treatment of Functioning and Non-Functioning Pancreatic and Duodenal Neuroendocrine Neoplasia within the MEN1 Syndrome - An International Consensus Statement.

The better understanding of the biological behavior of multiple endocrine neoplasia type 1 (MEN1) organ manifestations and the increase in clinical experience warrant a revision of previously published guidelines. Duodenopancreatic neuroendocrine neoplasias (DP-NENs) are still the second most common manifestation in MEN1 and, besides NENs of the thymus, remain a leading cause of death. DP-NENs are thus of main interest in the effort to reevaluate recommendations for their diagnosis and treatment. Especially over the last 2 years, more clinical experience has documented the follow-up of treated and untreated (natural-course) DP-NENs. It was the aim of the international consortium of experts in endocrinology, genetics, radiology, surgery, gastroenterology, and oncology to systematically review the literature and to present a consensus statement based on the highest levels of evidence. Reviewing the literature published over the past decade, the focus was on the diagnosis of F- and NF-DP-NENs within the MEN1 syndrome in an effort to further standardize and improve treatment and follow-up, as well as to establish a "logbook" for the diagnosis and treatment of DP-NENs. This shall help further reduce complications and improve long-term treatment results in these rare tumors. The following international consensus statement builds upon the previously published guidelines of 2001 and 2012 and attempts to supplement the recommendations issued by various national and international societies.

Group II p21-activated kinase, PAK4, is needed for activation of focal adhesion kinases, MAPK, GSK3, and ß-catenin in rat pancreatic acinar cells.

PAK4 is the only member of the Group II p21-activated kinases (PAKs) present in rat pancreatic acinar cells and is activated by gastrointestinal hormones/neurotransmitters stimulating PLC/cAMP and by various pancreatic growth factors. However, little is known of the role of PAK4 activation in cellular signaling cascades in pancreatic acinar cells. In the present study, we examined the role of PAK4's participation in five different cholecystokinin-8 (CCK-8)-stimulated signaling pathways (PI3K/Akt, MAPK, focal adhesion kinase, GSK3, and ß-catenin), which mediate many of its physiological acinar-cell effects, as well as effects in pathophysiological conditions. To define PAK4's role, the effect of two different PAK4 inhibitors, PF-3758309 and LCH-7749944, was examined under experimental conditions that only inhibited PAK4 activation and not activation of the other pancreatic PAK, Group I PAK2. The inhibitors' effects on activation of these five signaling cascades by both physiological and pathophysiological concentrations of CCK, as well as by 12-O-tetradecanoylphobol-13-acetate (TPA), a PKC-activator, were examined. CCK/TPA activation of focal adhesion kinases(PYK2/p125FAK) and the accompanying adapter proteins (paxillin/p130CAS), Mek1/2, and p44/42, but not c-Raf or other MAPKs (JNK/p38), were mediated by PAK4. Activation of PI3K/Akt/p70s6K was independent of PAK4, whereas GSK3 and ß-catenin stimulation was PAK4-dependent. These results, coupled with recent studies showing PAK4 is important in pancreatic fluid/electrolyte/enzyme secretion and acinar cell growth, show that PAK4 plays an important role in different cellular signaling cascades, which have been shown to mediate numerous physiological and pathophysiological processes in pancreatic acinar cells.NEW & NOTEWORTHY In pancreatic acinar cells, cholecystokinin (CCK) or 12-O-tetradecanoylphobol-13-acetate (TPA) activation of focal adhesion kinases (p125FAK,PYK2) and its accompanying adapter proteins, p130CAS/paxillin; Mek1/2, p44/42, GSK3, and ß-catenin are mediated by PAK4. PI3K/Akt/p70s6K, c-Raf, JNK, or p38 pathways are independent of PAK4 activation.

Development and Characterization of a Novel, High-Affinity, Specific, Radiolabeled Ligand for BRS-3 Receptors.

Bombesin (Bn) receptor subtype 3(BRS-3) is an orphan G-protein-coupled receptor of the Bn family, which does not bind any natural Bn peptide with high affinity. Receptor knockout studies show that the animals develop diabetes, obesity, altered temperature control, and other central nervous system (CNS)/endocrine/gastrointestinal changes. It is present in CNS, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology, as well as its receptor localization/pharmacology is largely unknown, in part due to the lack of a convenient, specific, direct radiolabeled ligand. This study was designed to address this problem and to develop and characterize a specific radiolabeled ligand for BRS-3. The peptide antagonist Bantag-1 had >10,000-fold selectivity for human BRS-3 (hBRS-3) over other mammalian Bn receptors (BnRs) [i.e., gastrin-releasing peptide receptor (GRPR) and neuromedin B receptor (NMBR)]. Using iodogen and basic conditions, it was radiolabeled to high specific activity (2200 Ci/mmol) and found to bind with high affinity/specificity to hBRS-3. Binding was saturable, rapid, and reversible. The ligand only interacted with known BRS-3 ligands, and not with other specific GRPR/NMBR ligands or ligands for unrelated receptors. The magnitude of 125I-Bantag-1 binding correlated with BRS-3 mRNA expression and the magnitude of activation of phospholipase C in lung cancer cells, as well as readily identifying BRS-3 in lung cancer cells and normal tissues, allowing the direct assessment of BRS-3 receptor pharmacology/numbers on cells containing BRS-3 with other BnRs, which is usually the case. This circumvents the need for subtraction assays, which are now frequently used to assess BRS-3 indirectly using radiolabeled pan-ligands, which interact with all BnRs.

Unmet Medical Needs in Metastatic Lung and Digestive Neuroendocrine Neoplasms.

Unmet medical needs are not infrequent in oncology, and these needs are usually of higher magnitude in rare cancers. The field of neuroendocrine neoplasms (NENs) has evolved rapidly during the last decade, and, currently, a new WHO classification is being implemented and several treatment options are available in the metastatic setting after the results of prospective phase III clinical trials. However, several questions are still unanswered, and decisions in our daily clinical practice should be made with limited evidence. In the 2016 meeting of the advisory board of the European Neuroendocrine Tumor Society (ENETS), the main unmet medical needs in the metastatic NENs setting were deeply discussed, and several proposals to try to solve them are presented in this article, including biomarkers, imaging, and therapy.

Unmet Needs in Functional and Nonfunctional Pancreatic Neuroendocrine Neoplasms.

Recently, the European Neuroendocrine Tumor Society (ENETS) held working sessions composed of members of the advisory board and other neuroendocrine neoplasm (NEN) experts to attempt to identify unmet needs in NENs in different locations or with advanced/poorly differentiated NENs. This report briefly summarizes the main proposed areas of unmet needs in patients with functional and nonfunctional pancreatic NENs.

Insights into Effects/Risks of Chronic Hypergastrinemia and Lifelong PPI Treatment in Man Based on Studies of Patients with Zollinger-Ellison Syndrome.

The use of proton pump inhibitors (PPIs) over the last 30 years has rapidly increased both in the United States and worldwide. PPIs are not only very widely used both for approved indications (peptic ulcer disease, gastroesophageal reflux disease (GERD), Helicobacter pylori eradication regimens, stress ulcer prevention), but are also one of the most frequently off-label used drugs (25-70% of total). An increasing number of patients with moderate to advanced gastroesophageal reflux disease are remaining on PPI indefinitely. Whereas numerous studies show PPIs remain effective and safe, most of these studies are <5 years of duration and little data exist for >10 years of treatment. Recently, based primarily on observational/epidemiological studies, there have been an increasing number of reports raising issues about safety and side-effects with very long-term chronic treatment. Some of these safety issues are related to the possible long-term effects of chronic hypergastrinemia, which occurs in all patients taking chronic PPIs, others are related to the hypo-/achlorhydria that frequently occurs with chronic PPI treatment, and in others the mechanisms are unclear. These issues have raised considerable controversy in large part because of lack of long-term PPI treatment data (>10-20 years). Zollinger-Ellison syndrome (ZES) is caused by ectopic secretion of gastrin from a neuroendocrine tumor resulting in severe acid hypersecretion requiring life-long antisecretory treatment with PPIs, which are the drugs of choice. Because in <30% of patients with ZES, a long-term cure is not possible, these patients have life-long hypergastrinemia and require life-long treatment with PPIs. Therefore, ZES patients have been proposed as a good model of the long-term effects of hypergastrinemia in man as well as the effects/side-effects of very long-term PPI treatment. In this article, the insights from studies on ZES into these controversial issues with pertinence to chronic PPI use in non-ZES patients is reviewed, primarily concentrating on data from the prospective long-term studies of ZES patients at NIH.

Prospective Evaluation of Results of Reoperation in Zollinger-Ellison Syndrome.

OBJECTIVE: To determine the role of reoperation in patients with persistent or recurrent Zollinger-Ellison Syndrome (ZES). BACKGROUND: Approximately, 0% to 60% of ZES patients are disease-free (DF) after an initial operation, but the tumor may recur. METHODS: A prospective database was queried. RESULTS: A total of 223 patients had an initial operation for possible cure of ZES and then were subsequently evaluated serially with cross sectional imaging-computed tomography, magnetic resonance imaging, ultrasound, more recently octreoscan-and functional studies for ZES activity. The mean age at first surgery was 49 years and with an 11-year mean follow-up 52 patients (23%) underwent reoperation when ZES recurred with imageable disease. Results in this group are analyzed in the current report. Reoperation occurred on a mean of 6 years after the initial surgery with a mean number of reoperations of 1 (range 1-5). After reoperation 18/52 patients were initially DF (35%); and after a mean follow-up of 8 years, 13/52 remained DF (25%). During follow-up, 9/52 reoperated patients (17%) died, of whom 7 patients died a disease-related death (13%). The overall survival from first surgery was 84% at 20 years and 68% at 30 years. Multiple endocrine neoplasia type 1 status did not affect survival, but DF interval and liver metastases did. CONCLUSIONS: These results demonstrate that a significant proportion of patients with ZES will develop resectable persistent or recurrent disease after an initial operation. These patients generally have prolonged survival after reoperation and 25% can be cured with repeat surgery, suggesting all ZES patients postresection should have systematic imaging, and if tumor recurs, advise repeat operation.

Utility of chromogranin B compared with chromogranin A as a biomarker in Japanese patients with pancreatic neuroendocrine tumors.

OBJECTIVE: Currently, serum chromogranin A is a well-established biomarker for pancreatic neuroendocrine tumors; however, other pancreatic diseases, oral use of a proton pump inhibitor and renal impairment can affect chromogranin A. Meanwhile, chromogranin B, belonging to the same granin family as chromogranin A, is not fully examined in these conditions. The present study aimed to evaluate the utility of chromogranin B as a pancreatic neuroendocrine tumor biomarker. METHODS: Serum chromogranin B levels were determined by radioimmunoassay and serum chromogranin A levels by enzyme-linked immunosorbent assay in pancreatic neuroendocrine tumor (n = 91) and other pancreatic conditions, and in healthy people (n = 104), to assess the relationships with clinical features. RESULTS: The diagnostic ability of chromogranin B was as good as chromogranin A. The area under the curve was 0.79 for chromogranin B (sensitivity/specificity: 72%/77%), and 0.78 for chromogranin A (sensitivity/specificity: 79%/64%). Chromogranin B was not affected by proton pump inhibitor use and age, which affected chromogranin A. The number of cases without liver metastases was larger in pancreatic neuroendocrine tumor patients with positive chromogranin B and negative chromogranin A. Though chromogranin A significantly elevated cases with proton pump inhibitor treatment and had positive correlation with age, chromogranin B did not have the tendencies. However, both chromogranin B and chromogranin A elevated in the case with renal impairment. In addition, the logistic regression analysis showed that chromogranin B was superior to chromogranin A in differentiation of pancreatic neuroendocrine tumor from other pancreatic diseases. CONCLUSIONS: Compared with chromogranin A, chromogranin B may be more useful during proton pump inhibitor treatment and can detect tumors without liver metastases. In addition, chromogranin B may be an excellent biomarker when differentiation of pancreatic neuroendocrine tumor from other pancreatic diseases is required.

Limited Parathyroidectomy in Multiple Endocrine Neoplasia Type 1-Associated Primary Hyperparathyroidism: A Setup for Failure.

BACKGROUND: Recently, some surgeons have suggested that minimally invasive parathyroidectomy guided by preoperative localizing studies of patients with multiple endocrine neoplasia type 1 (MEN1)-associated primary hyperparathyroidism (pHPT) provides an acceptable outcome while minimizing the risk of hypoparathyroidism. This study aimed to evaluate the outcome for MEN1 patients who underwent limited parathyroidectomy compared with subtotal parathyroidectomy. METHODS: The authors performed a retrospective analysis of 99 patients with MEN1-associated pHPT who underwent at least one parathyroid operation at their institution. Preoperative imaging studies, intraoperative findings, and clinical outcomes for patients were compared. RESULTS: A total of 99 patients underwent 146 operations. Persistent pHPT was significantly higher in patients whose initial operations involved removal of 1 or 2 glands (69 %) or 2.5 to 3 glands (20 %) compared with those who had 3.5 or more glands removed (6 %) (P < 0.01). Persistent pHPT occurred in 5 % of all operations that cumulatively removed 3.5 or more parathyroid glands compared with 40 % of operations that removed 3 or fewer glands (P < 0.01). The single largest parathyroid gland was correctly identified preoperatively in 69 % (22/32) of the patients. However, preoperative localizing studies missed enlarged contralateral parathyroid glands in 86 % (19/22) of these patients. Preoperative localizing studies missed the largest contralateral parathyroid gland in 16 % (5/32) of the patients. CONCLUSIONS: Limited parathyroidectomy in MEN1 is associated with a high failure rate and should not be performed. Preoperative identification of a single enlarged parathyroid gland in MEN1 is not reliable enough to justify unilateral neck exploration because additional enlarged contralateral parathyroid glands are frequently missed.

Long-term outcomes and prognostic factors in 78 Japanese patients with advanced pancreatic neuroendocrine neoplasms: a single-center retrospective study.

OBJECTIVE: Despite an increase in the number of Japanese patients with pancreatic neuroendocrine neoplasms, long-term outcomes and prognostic factors, especially for those with advanced disease, remain unclear. METHODS: We retrospectively reviewed the medical records of 78 patients with unresectable pancreatic neuroendocrine neoplasms treated at our hospital from January 1987 to March 2015. Survival analyses were performed using Kaplan-Meier methods. Prognostic significance of several clinicopathological factors were analyzed by univariate and multivariate analyses using a Cox regression model. RESULTS: Median overall survivals of pancreatic neuroendocrine tumor (n = 64) and pancreatic neuroendocrine carcinoma (n = 14) were 83.7 and 9.1 months, respectively (hazard ratio: 0.02, 95% confidence interval: 0.01-0.08, P < 0.001). Although no significant differences were observed using a Ki-67 cut-off value of 2% (hazard ratio: 0.46, 95% confidence interval: 0.16-1.13, P = 0.0989), a Ki-67 cut-off of 10% was a significant predictor in patients with pancreatic neuroendocrine tumor (hazard ratio: 9.95, 95% confidence interval, 3.01-32.97, P < 0.001). Treatment after the advent of targeted therapy (hazard ratio: 0.07, 95% confidence interval: 0.03-0.19, P < 0.001) and the presence of bone metastases (hazard ratio: 4.38, 95% confidence interval: 1.42-11.29, P = 0.013) were significant prognostic factors in patients with pancreatic neuroendocrine tumor evaluated by univariate analysis. Multivariate analysis also revealed that a Ki-67 index ≥10% (hazard ratio: 38.8, 95% confidence interval: 8.42-226.62, P < 0.001), approval of targeted therapy (hazard ratio: 0.02, 95% confidence interval: 0.00-0.11, P < 0.001) and bone metastases (hazard ratio: 5.56, 95% confidence interval: 1.10-24.00, P = 0.039) were independent prognostic factors. CONCLUSIONS: We elucidated the long-term outcomes and prognostic factors in Japanese patients with advanced pancreatic neuroendocrine neoplasms.

When should a liver resection be performed in patients with liver metastases from neuroendocrine tumours? A systematic review with practice recommendations.

AIM: To determine the benefits and risks of hepatic resection versus non-resectional liver-directed treatments in patients with potentially resectable neuroendocrine liver metastases. METHODS: A systematic review identified 1594 reports which alluded to a possible liver resection for neuroendocrine tumour metastases, of which 38 reports (all retrospective), comprising 3425 patients, were relevant. RESULTS: Thirty studies reported resection alone, and 16 studies reported overall survival (OS). Only two studies addressed quality-of-life (QoL) issues. Five-year overall survival was reported at 41-100%, whereas 5-year progression-free survival (PFS) was 5-54%. We identified no robust evidence that a liver resection was superior to any other liver-directed therapies in improving OS or PFS. There was no evidence to support the use of a R2 resection (debulking), with or without tumour ablation, to improve either OS or QoL. There was little evidence to guide sequencing of surgery for patients presenting in Stage IV with resectable disease, and none to support a resection of asymptomatic primary tumours in the presence of non-resectable liver metastases. CONCLUSION: Low-level recommendations are offered to assist in the management of patients with neuroendocrine liver metastases, along with recommendations for future studies.

Gastrointestinal hormones stimulate growth of Foregut Neuroendocrine Tumors by transactivating the EGF receptor.

Foregut neuroendocrine tumors [NETs] usually pursuit a benign course, but some show aggressive behavior. The treatment of patients with advanced NETs is marginally effective and new approaches are needed. In other tumors, transactivation of the EGF receptor (EGFR) by growth factors, gastrointestinal (GI) hormones and lipids can stimulate growth, which has led to new treatments. Recent studies show a direct correlation between NET malignancy and EGFR expression, EGFR inhibition decreases basal NET growth and an autocrine growth effect exerted by GI hormones, for some NETs. To determine if GI hormones can stimulate NET growth by inducing transactivation of EGFR, we examined the ability of EGF, TGFα and various GI hormones to stimulate growth of the human foregut carcinoid,BON, the somatostatinoma QGP-1 and the rat islet tumor,Rin-14B-cell lines. The EGFR tyrosine-kinase inhibitor, AG1478 strongly inhibited EGF and the GI hormones stimulated cell growth, both in BON and QGP-1 cells. In all the three neuroendocrine cell lines studied, we found EGF, TGFα and the other growth-stimulating GI hormones increased Tyr(1068) EGFR phosphorylation. In BON cells, both the GI hormones neurotensin and a bombesin analogue caused a time- and dose-dependent increase in EGFR phosphorylation, which was strongly inhibited by AG1478. Moreover, we found this stimulated phosphorylation was dependent on Src kinases, PKCs, matrix metalloproteinase activation and the generation of reactive oxygen species. These results raise the possibility that disruption of this signaling cascade by either EGFR inhibition alone or combined with receptor antagonists may be a novel therapeutic approach for treatment of foregut NETs/PETs.

PSCs and GLP-1R: occurrence in normal pancreas, acute/chronic pancreatitis and effect of their activation by a GLP-1R agonist.

There is increasing concern about the development of pancreatitis in patients with diabetes mellitus who received long-term glucagon-like peptide-1 (GLP-1) analog treatment. Its pathogenesis is unknown. The effects of GLP-1 agonists on pancreatic endocrine cells are well studied; however, there is little information on effects on other pancreatic tissues that might be involved in inflammatory processes. Pancreatic stellate cells (PSCs) can have an important role in pancreatitis, secreting various inflammatory cytokines/chemokines, as well as collagen. In this study, we investigated GLP-1R occurrence in normal pancreas, acute pancreatitis (AP)/chronic pancreatitis (CP), and the effects of GLP-1 analog on normal PSCs, their ability to stimulate inflammatory mediator secretion or proliferation. GLP-1 receptor (GLP-1R) expression/localization in normal pancreas and pancreatitis (AP/CP) tissues were evaluated with histological/immunohistochemical analysis. PSCs were isolated from male Wistar rats. GLP-1R expression and effects of GLP-1 analog on activated PSCs was examined with real-time PCR, MTS assays and western blotting. In normal pancreas, pancreatic ß cells expressed GLP-1R, with only low expression in acinar cells, whereas in AP or CP, acinar cells, ductal cells and activated PSCs expressed GLP-1R. With activation of normal PSCs, GLP-1R is markedly increased, as is multiple other incretin-related receptors. The GLP-1 analog, liraglutide, did not induce inflammatory genes expression in activated PSCs, but induced proliferation. Liraglutide activated multiple signaling cascades in PSCs, and the extracellular signal-regulated kinase pathway mediated the PSCs proliferation. GLP-1Rs are expressed in normal pancreas and there is marked enhanced expression in AP/CP. GLP-1-agonist induced cell proliferation of activated PSCs without increasing release of inflammatory mediators. These results suggest chronic treatment with GLP-1R agonists could lead to proliferation/chronic activation of PSCs, which may lead to important effects in the pancreas.

Serum chromogranin A is a useful marker for Japanese patients with pancreatic neuroendocrine tumors.

Although chromogranin A (CGA) is a useful marker for pancreatic neuroendocrine tumors (pNET) in the West, its usefulness in Japanese populations is unclear. To assess this, we evaluated the serum CGA levels in 189 patients with various pancreatic diseases, including proven pNET (n = 69), pancreatic cancer (PC) (n = 50), chronic pancreatitis (CP) (n = 50) and autoimmune pancreatitis (AIP) (n = 20), and 112 normal controls (controls) using an ELISA kit. The mean CGA level of patients with pNET was significantly higher than any of the other groups (407.8 ± 984.6 ng/mL [pNET] vs 91.8 ± 101.8 ng/mL [PC], 93.6 ± 57.5 ng/mL [CP], 69.9 ± 52.4 ng/mL [AIP] and 62.5 ± 48.3 ng/mL [controls]). Limiting the analysis to patients not using proton pump inhibitors (PPI), the CGA level of patients with PC or CP was not significantly different compared with the controls. Discriminant analysis revealed that the best cut-off value of CGA to distinguish patients with pNET from the controls was 78.7 ng/mL, with a sensitivity and specificity of 53.6% and 78.6%, respectively. In patients with pNET, significant factors associating with elevated CGA levels were tumor classification, tumor size, and the presence of liver metastases in univariate analysis as well as PPI use and the presence of liver metastases in multivariate analysis. We show that CGA is a useful marker for diagnosing pNET in Japanese populations and for distinguishing patients with pNET from patients with other pancreatic diseases. The increased use of CGA in Japan will likely be a helpful tool in managing these patients, as found in the West.

ERK pathway and sheddases play an essential role in ethanol-induced CX3CL1 release in pancreatic stellate cells.

The clinical course of chronic pancreatitis (CP) worsens with drinking, and pancreatic stellate cells (PSCs) have an important role in the pathogenesis of alcoholic CP. Chemokines recruit inflammatory cells, resulting in chronic pancreatic inflammation. Although serum levels of fractalkine (CX3CL1) are significantly elevated in patients with alcoholic CP, the mechanism of this elevation remains unclear. This study aims to determine the effects of cytokines, pathogen-associated molecular patterns (PAMPs), and ethanol and its metabolites on CX3CL1 secretion by PSCs. Male Wistar/Bonn Kobori (WBN/Kob) rats aged 15 to 20 weeks were used as rodent models of CP in vivo. PSCs were isolated from 6-week-old male Wistar rats. The effects of cytokines, PAMPs, and ethanol and its metabolites on chemokine production and activation of signaling pathways in PSCs in vitro were examined by real-time reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and enzyme-linked immunosorbent assay. Expression of CX3CL1 and matrix metalloprotease (MMP)-2 was increased in the pancreas of WBN/Kob rats. The rat PSCs expressed CX3CL1, MMP-2, and a disintegrin and metalloprotease domain (ADAM) 17. Cytokines and PAMPs induced CX3CL1 release and activated extracellular signal-regulated kinase (ERK), MMP-9, and ADAM17. CX3CL1 release was suppressed by specific inhibitors of ERK, MMP, and ADAM, and ERK was associated with CX3CL1 transcription. Ethanol and phorbol myristate acetate synergistically increased CX3CL1 release. Real-time PCR and western blotting confirmed the synergistic activation of ERK and ADAM17. Ethanol synergistically increased CX3CL1 release via ERK and ADAM17 activation in PSCs. In conclusion, we demonstrated for the first time that ethanol synergistically increased CX3CL1 release from PSCs at least in part through activation of ERK mitogen-activated protein kinase and ADAM17. This might be one of the mechanisms of serum CX3CL1 elevation and disease progression in patients with alcoholic CP.

Comparative pharmacology of bombesin receptor subtype-3, nonpeptide agonist MK-5046, a universal peptide agonist, and peptide antagonist Bantag-1 for human bombesin receptors.

Bombesin-receptor-subtype-3 (BRS-3) is an orphan G-protein-coupled receptor of the bombesin (Bn) family whose natural ligand is unknown and which does not bind any natural Bn-peptide with high affinity. It is present in the central nervous system, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology is largely unknown because of the lack of selective ligands. Recently, MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-{[1-(trifluoromethyl)cyclopropyl]methyl}-1H-imidazol-2-yl)propan-2-ol] and Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3-dimethylamino) benzylamide N-methylammonium trifluoroacetate], a nonpeptide agonist and a peptide antagonist, respectively, for BRS-3 have been described, but there have been limited studies on their pharmacology. We studied MK-5046 and Bantag-1 interactions with human Bn-receptors-human bombesin receptor subtype-3 (hBRS-3), gastrin-releasing peptide receptor (GRP-R), and neuromedin B receptor (NMB-R)-and compared them with the nonselective, peptide-agonist [d-Tyr6,ßAla11,Phe13,Nle14]Bn-(6-14) (peptide #1). Receptor activation was detected by activation of phospholipase C (PLC), mitogen-activated protein kinase (MAPK), focal adhesion kinase (FAK), paxillin, and Akt. In hBRS-3 cells, the relative affinities were Bantag-1 (1.3 nM) > peptide #1 (2 nM) > MK-5046 (37-160 nM) > GRP, NMB (>10 µM), and the binding-dose-inhibition curves were broad (>4 logs), with Hill coefficients differing significantly from unity. Curve-fitting demonstrated high-affinity (MK-5046, Ki = 0.08 nM) and low-affinity (MK-5046, Ki = 11-29 nM) binding sites. For PLC activation in hBRS-3 cells, the relative potencies were MK-5046 (0.02 nM) > peptide #1 (6 nM) > GRP, NMB, Bantag-1 (>10 µM), and MK-5046 had a biphasic dose response, whereas peptide #1 was monophasic. Bantag-1 was a specific hBRS-3-antagonist. In hBRS-3 cells, MK-5046 was a full agonist for activation of MAPK, FAK, Akt, and paxillin; however, it was a partial agonist for phospholipase A2 (PLA2) activation. The kinetics of activation/duration of action for PLC/MAPK activation of MK-5046 and peptide #1 differed, with peptide #1 causing more rapid stimulation; however, MK-5046 had more prolonged activity. Our study finds that MK-5046 and Bantag-1 have high affinity/selectivity for hBRS-3. The nonpeptide MK-5046 and peptide #1 agonists differ markedly in their receptor coupling, ability to activate different signaling cascades, and kinetics/duration of action. These results show that their hBRS-3 receptor activation is not always concordant and could lead to markedly different cellular responses.

Zollinger-Ellison syndrome: recent advances and controversies.

PURPOSE OF REVIEW: To review the recent advances and current controversies in patients with Zollinger-Ellison syndrome (ZES). RECENT FINDINGS: Recent advances in the management of ZES include: improved understanding of the pathogenesis of gastrinoma and pancreatic neuroendocrine tumors, new prognostic classification systems, new diagnostic algorithms, more sensitive localization studies, new treatment strategies including improved control of gastric acid secretion and role for surgery, and new approaches to patients with advanced disease. Controversies include: the best approach to a patient with hypergastrinemia suspected of possibly having ZES, the appropriate gastrin assay to use, the role of surgery in patients with ZES, especially those with multiple endocrine neoplasia type 1, and the precise order of therapeutic modalities in the treatment of patients with advanced disease. SUMMARY: This review updates clinicians regarding important advances and controversies required to optimally diagnose and manage patients with ZES.

Utility of intraoperative parathyroid hormone monitoring in patients with multiple endocrine neoplasia type 1-associated primary hyperparathyroidism undergoing initial parathyroidectomy.

BACKGROUND: Intraoperative parathyroid hormone monitoring (IOPTH) is a widely used adjunct for primary hyperparathyroidism (pHPT). However, the benefit of IOPTH in familial pHPT, such as in multiple endocrine neoplasia type I (MEN1), remains unclear. METHODS: We performed a retrospective analysis of 52 patients with MEN1-associated pHPT undergoing initial parathyroidectomy with IOPTH monitoring at our institution. Parathyroid hormone (PTH) levels were measured before skin incision and 10 min after resection of the last parathyroid gland. Variables analyzed included percent drop of PTH from baseline and the final PTH level compared to the normal reference range (RR). RESULTS: A total of 52 patients underwent initial subtotal parathyroidectomy with IOPTH. An IOPTH decrease cutoff of ≥75 % from baseline had the highest biochemical cure rate (87 %). In the remaining 13 % who met this cutoff, all had persistent pHPT, with ≥90 % drop of PTH from baseline. The remaining patients, who did not meet the ≥75 % cutoff, were cured. Follow-up was available for three of four patients with final IOPTH levels above the RR: one had persistent pHPT, two had hypoparathyroidism (50 %). When a postresection PTH level was within the RR, 88 % of patients were cured. While considered cured from pHPT, 7 % of patients in this group developed permanent hypoparathyroidism. When the final PTH level dropped below the RR, 28 % developed permanent hypoparathyroidism. CONCLUSIONS: A cutoff in IOPTH decrease of ≥75 % from baseline has the highest biochemically cure rate in patients with pHPT associated with MEN1. However, a 75 % cutoff in IOPTH decrease does not exclude persistent pHPT. The absolute IOPTH value does not accurately predict postoperative hypoparathyroidism.