Publications by authors named "Herbert A Schmid"

34 Publications

Somatostatin analogue pasireotide (SOM230) inhibits catecholamine secretion in human pheochromocytoma cells.

Cancer Lett 2021 Oct 9. Epub 2021 Oct 9.

Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, F-67000, Strasbourg, France. Electronic address:

Increasingly common, neuroendocrine tumors (NETs) are regarded nowadays as neoplasms potentially causing debilitating symptoms and life-threatening medical conditions. Pheochromocytoma is a NET that develops from chromaffin cells of the adrenal medulla, and is responsible for an excessive secretion of catecholamines. Consequently, patients have an increased risk for clinical symptoms such as hypertension, elevated stroke risk and various cardiovascular complications. Somatostatin analogues are among the main anti-secretory medical drugs used in current clinical practice in patient with NETs. However, their impact on pheochromocytoma-associated catecholamine hypersecretion remains incompletely explored. This study investigated the potential efficacy of octreotide and pasireotide (SOM230) on human tumor cells directly cultured from freshly resected pheochromocytomas using an implemented catecholamine secretion measurement by carbon fiber amperometry. SOM230 treatment efficiently inhibited nicotine-induced catecholamine secretion both in bovine chromaffin cells and in human tumor cells whereas octreotide had no effect. Moreover, SOM230 specifically decreased the number of exocytic events by impairing the stimulation-evoked calcium influx as well as the nicotinic receptor-activated inward current in human pheochromocytoma cells. Altogether, our findings indicate that SOM230 acts as an inhibitor of catecholamine secretion through a mechanism involving the nicotinic receptor and might be considered as a potential anti-secretory treatment for patients with pheochromocytoma.
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http://dx.doi.org/10.1016/j.canlet.2021.10.009DOI Listing
October 2021

Pharmacologic Normalization of Pancreatic Cancer-Associated Fibroblast Secretome Impairs Prometastatic Cross-Talk With Macrophages.

Cell Mol Gastroenterol Hepatol 2021 20;11(5):1405-1436. Epub 2021 Jan 20.

Centre de Recherches en Cancérologie de Toulouse (CRCT), Université de Toulouse, INSERM Unité Mixte de Recherche UMR-1037, CNRS Equipe de Recherche Labellisée ERL5294, Equipe de Recherche Labellisée "Ligue Contre le Cancer" & "LabEx Toucan", Toulouse, France. Electronic address:

Background & Aims: Cancer-associated fibroblasts (CAFs) from pancreatic adenocarcinoma (PDA) present high protein synthesis rates. CAFs express the G-protein-coupled somatostatin receptor sst1. The sst1 agonist SOM230 blocks CAF protumoral features in vitro and in immunocompromised mice. We have explored here the therapeutic potential of SOM230, and underlying mechanisms, in immunocompetent models of murine PDA mimicking the heavy fibrotic and immunosuppressive stroma observed in patient tumors.

Methods: Large-scale mass spectrometry analyses were performed on media conditioned from 9 patient PDA-derived CAF primary cultures. Spontaneous transgenic and experimental (orthotopic co-graft of tumor cells plus CAFs) PDA-bearing mice were longitudinally ultrasound-monitored for tumor and metastatic progression. Histopathology and flow cytometry analyses were performed on primary tumors and metastases. Stromal signatures were functionally validated through bioinformatics using several published, and 1 original, PDA database.

Results: Proteomics on the CAF secretome showed that SOM230 controls stromal activities including inflammatory responses. Among the identified secreted proteins, we validated that colony-stimulating factor 1 (CSF-1) (a macrophage growth factor) was reduced by SOM230 in the tumor and plasma of PDA-harboring mice, alongside intratumor stromal normalization (reduced CAF and macrophage activities), and dramatic metastasis reduction. In transgenic mice, these SOM230 benefits alleviate the chemotherapy-induced (gemcitabine) immunosuppressive stroma reshaping. Mechanistically, SOM230 acts in vivo on CAFs through sst1 to disrupt prometastatic CAF production of CSF-1 and cross-talk with macrophages. We found that in patients, stromal CSF-1 was associated with aggressive PDA forms.

Conclusions: We propose SOM230 as an antimetastatic therapy in PDA for its capacity to remodel the fibrotic and immunosuppressive myeloid stroma. This pharmacotherapy should benefit PDA patients treated with chemotherapies.
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http://dx.doi.org/10.1016/j.jcmgh.2021.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8024982PMC
January 2021

Radiotherapy and pasireotide treatment of a growth hormone producing pituitary tumor in a diabetic dog.

Can Vet J 2018 10;59(10):1089-1093

Southfields Veterinary Specialists, formerly VRCC, Laindon, United Kingdom (Zublena, Tamborini, North, Lobacz); SeersCroft, North Norsham, United Kingdom (Andrew); University Veterinary Hospital, Dublin, Ireland (Mooney); Department of Clinical Science and Services, The Royal Veterinary College, Herts, United Kingdom (Woolhead, Covey, Church, Niessen); Novartis Institutes for BioMedical Research, Oncology Research, Novartis Pharma AG, Basel, Switzerland (Schmid).

An 8-year-old castrated male border terrier dog was diagnosed with acromegaly resulting from a growth hormone secreting pituitary tumor. Sixteen daily fractions of radiation therapy were delivered followed, approximately 1 year later, by administration of pasireotide. The aforementioned treatment was considered effective and should be further evaluated in similar cases.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135304PMC
October 2018

Pasireotide treatment does not modify hyperglycemic and corticosterone acute restraint stress responses in rats.

Stress 2018 07 17;21(4):370-375. Epub 2018 Apr 17.

c Department of Neuroendocrinology , Barrow Pituitary Center, Barrow Neurological Institute , Phoenix , AZ, USA.

Pasireotide is a new-generation somatostatin analog that acts through binding to multiple somatostatin receptor subtypes. Studies have shown that pasireotide induces hyperglycemia, reduces glucocorticoid secretion, alters neurotransmission, and potentially affects stress responses typically manifested as hyperglycemia and increased corticosterone secretion. This study specifically aimed to evaluate whether pasireotide treatment modifies glucose and costicosterone secretion in response to acute restraint stress. Male Holtzman rats of 150-200 g were treated with pasireotide (10 µg/kg/day) twice-daily for two weeks or vehicle for the same period. Blood samples were collected at baseline and after 5, 10, 30, and 60 min of restraint stress. The three experimental groups comprised of vehicle + restraint (VEHR), pasireotide + restraint (PASR), and pasireotide + saline (PASNR). Following pasireotide treatment, no significant differences in baseline glucose and corticosterone levels were observed among the three groups. During restraint, hyperglycemia was observed at 10 min (p < .01 for both comparisons), peaked at 30 min (p < .01 for both comparisons) and showed higher 60 min areas under glucose curves in the VEHR and PASR stressed groups when compared to the non-stressed PASNR group (p < .05 for both comparisons). Restraint also increased corticosterone secretion in the VEHR and PASR stressed groups at 5 min (p < .01 for both comparisons), and peaked at 30 min (p < .01 for both comparisons) with corresponding higher 60 min areas under corticosterone curves when compared to the non-stressed PASNR group (p < .01 for both comparisons). In conclusion, pasireotide treatment does not modify hyperglycemic- and corticosterone-restraint stress responses, thus preserving acute stress regulation.
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http://dx.doi.org/10.1080/10253890.2018.1451838DOI Listing
July 2018

Ectopic expression of in pancreatic δ cells results in β-like cell neogenesis.

J Cell Biol 2017 12 12;216(12):4299-4311. Epub 2017 Oct 12.

Université Côte d'Azur, Institut National de la Santé et de la Recherche Medicale, Centre National de la Recherche Scientifique, Institut Biologie Valrose, Nice, France

The recent demonstration that pancreatic α cells can be continuously regenerated and converted into β-like cells upon ectopic expression of opened new avenues of research in the endocrine cell differentiation and diabetes fields. To determine whether such plasticity was also shared by δ cells, we generated and characterized transgenic animals that express specifically in somatostatin-expressing cells. We demonstrate that the ectopic expression of in δ cells is sufficient to induce their conversion into functional β-like cells. Importantly, this conversion induces compensatory mechanisms involving the reactivation of endocrine developmental processes that result in dramatic β-like cell hyperplasia. Importantly, these β-like cells are functional and can partly reverse the consequences of chemically induced diabetes.
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http://dx.doi.org/10.1083/jcb.201704044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5716283PMC
December 2017

Octreotide and pasireotide (dis)similarly inhibit pituitary tumor cells in vitro.

J Endocrinol 2016 Nov 1;231(2):135-145. Epub 2016 Sep 1.

Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)Córdoba, Spain

Somatostatin analogs (SSA) are the mainstay of pharmacological treatment for pituitary adenomas. However, some patients escape from therapy with octreotide, a somatostatin receptor 2 (sst2)-preferring SSA, and pasireotide, a novel multi-sst-preferring SSA, may help to overcome this problem. It has been proposed that correspondence between sst1-sst5 expression pattern and SSA-binding profile could predict patient's response. To explore the cellular/molecular features associated with octreotide/pasireotide response, we performed a parallel comparison of their in vitro effects, evaluating sst1-sst5 expression, intracellular Ca signaling ([Ca]), hormone secretion and cell viability, in a series of 85 pituitary samples. Somatotropinomas expressed sst5>sst2, yet octreotide reduced [Ca] more efficiently than pasireotide, while both SSA similarly decreased growth hormone release/expression and viability. Corticotropinomas predominantly expressed sst5, but displayed limited response to pasireotide, while octreotide reduced functional endpoints. Non-functioning adenomas preferentially expressed sst3 but, surprisingly, both SSA increased cell viability. Prolactinomas mainly expressed sst1 but were virtually unresponsive to SSA. Finally, both SSA decreased [Ca] in normal pituitaries. In conclusion, both SSA act in vitro on pituitary adenomas exerting both similar and distinct effects; however, no evident correspondence was found with the sst1-sst5 profile. Thus, it seems plausible that additional factors, besides the simple abundance of a given sst, critically influence the SSA response.
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http://dx.doi.org/10.1530/JOE-16-0332DOI Listing
November 2016

Pasireotide Therapy of Multiple Endocrine Neoplasia Type 1-Associated Neuroendocrine Tumors in Female Mice Deleted for an Men1 Allele Improves Survival and Reduces Tumor Progression.

Endocrinology 2016 05 18;157(5):1789-98. Epub 2016 Mar 18.

Academic Endocrine Unit (G.V.W., M.S., B.S.S., K.E.L., R.V.T.), Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Churchill Hospital, Oxford, OX3 7LJ, United Kingdom; Nuffield Department of Surgical Sciences (G.V.W., B.S.S.), University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom; Department of Endocrinology (A.B.G.), OCDEM, Churchill Hospital, Oxford, OX3 7LJ, United Kingdom; and Novartis Pharma AG (H.A.S.), Novartis Institutes for Biomedical Research, Oncology, CH-4057 Basel, Switzerland.

Pasireotide, a somatostatin analog, is reported to have anti-proliferative effects in neuroendocrine tumors (NETs). We therefore assessed the efficacy of pasireotide for treating pancreatic and pituitary NETs that develop in a mouse model of multiple endocrine neoplasia type 1 (MEN1). Men1(+/-) mice were treated from age 12 mo with 40 mg/kg pasireotide long-acting release formulation, or PBS, intramuscularly monthly for 9 mo. The Men1(+/-) mice had magnetic resonance imaging at 12 and 21 mo, and from 20 mo oral 5-bromo-2-deoxyuridine for 1 mo, to assess tumor development and proliferation, respectively. NETs were collected at age 21 mo, and proliferation and apoptosis assessed by immunohistochemistry and TUNEL assays, respectively. Pasireotide-treated Men1(+/-) mice had increased survival (pasireotide, 80.9% vs PBS, 65.2%; P < .05), with fewer mice developing pancreatic NETs (pasireotide, 86.9% vs PBS, 96.9%; P < .05) and smaller increases in pituitary NET volumes (pre-treated vs post-treated, 0.803 ± 0.058 mm(3) vs 2.872 ± 0.728 mm(3) [pasireotide] compared with 0.844 ± 0.066 mm(3) vs 8.847 ±1.948 mm(3) [PBS]; P < .01). In addition, pasireotide-treated mice had fewer pancreatic NETs compared with PBS-treated mice (2.36 ± 0.25 vs 3.72 ± 0.32, respectively; P < .001), with decreased proliferation in pancreatic NETs (pasireotide, 0.35 ± 0.03% vs PBS, 0.78 ± 0.08%; P < .0001) and pituitary NETs (pasireotide, 0.73 ±0.07% vs PBS, 1.81 ± 0.15%; P < .0001), but increased apoptosis in pancreatic NETs (pasireotide, 0.42 ± 0.05% vs PBS, 0.19 ± 0.03%; P < .001) and pituitary NETs (pasireotide, 14.75 ± 1.58% vs PBS, 2.35 ± 0.44%; P < .001). Thus, pasireotide increased survival and inhibited pancreatic and pituitary NET growth, thereby indicating its potential as an anti-proliferative and pro-apoptotic therapy.
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http://dx.doi.org/10.1210/en.2015-1965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870877PMC
May 2016

Effect of pasireotide on glucose- and growth hormone-related biomarkers in patients with inadequately controlled acromegaly.

Endocrine 2016 Jul 23;53(1):210-9. Epub 2016 Feb 23.

Northwest Pituitary Center, Oregon Health & Science University, Portland, OR, USA.

The purpose of this study was to gain more insight into the mechanism of action of pasireotide in patients who completed the PAOLA study. PAOLA was a 24-week, Phase III, randomized, three-arm study of pasireotide LAR 40 and 60 mg versus octreotide LAR 30 mg or lanreotide Autogel 120 mg in patients with inadequately controlled acromegaly. The current work was a planned exploratory objective of the PAOLA study that evaluated changes in levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1), IGF-binding proteins (IGFBP-2, IGFBP-3), glycated haemoglobin (HbA1c) and fasting plasma glucose (FPG) in each treatment arm. Responders to pasireotide LAR (mean GH levels <2.5 μg/L and normal IGF-1 levels at 24 weeks) had lower GH and IGF-1 levels at baseline (GH 5.1 ng/mL, IGF-1 519 ng/mL) than non-responders (GH 7.9 ng/mL, IGF-1 672 ng/mL). Frequency of hyperglycaemia after pasireotide treatment was similar in responders and non-responders and depended more on the baseline FPG level. 47 % of all patients treated with pasireotide LAR (40 or 60 mg) did not receive antidiabetic medication at any time during this study. This is the first study to evaluate the treatment effect of pasireotide on key hormonal and glycaemic biomarkers and to identify potential predictors of pasireotide-associated hyperglycaemia. Pre-treatment glucose status may be predictive of the development of pasireotide-associated hyperglycaemia. A large subset of patients with acromegaly does not experience major disturbances in glucose homeostasis while receiving pasireotide LAR.
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http://dx.doi.org/10.1007/s12020-016-0895-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4901125PMC
July 2016

Somatostatin receptor activation is involved in the control of daily torpor in a seasonal mammal.

Am J Physiol Regul Integr Comp Physiol 2015 Sep 8;309(6):R668-74. Epub 2015 Jul 8.

Rowett Institute for Nutrition and Health, Aberdeen, United Kingdom; and.

Siberian hamsters (Phodopus sungorus) show spontaneous daily torpor only after ∼2 mo in winter-like short photoperiods (SP). Although some SP-induced hormonal changes have been demonstrated to be necessary for the occurrence of seasonal torpor, the whole set of preconditions is still unknown. Recent findings provide evidence that the hypothalamic pituitary growth axis is involved in endocrine responses to SP exposure in the photoperiodic hamsters. To examine whether suppression of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) secretion affects the incidence of daily torpor, we used two somatostatin receptor agonists, pasireotide (SOM230) and octreotide, with different affinity profiles for receptor subtypes. Pasireotide strikingly increased the torpor frequency in male hamsters compared with sham-treated controls, and torpor duration was often increased, which in some cases exceeded 12 h. In contrast, administration of octreotide reduced the body weight of SP hamsters but had only a marginal effect on torpor frequency in males and no effect in females. Together with measured concentrations of circulating IGF-1, the present results strongly suggest that reduced activity of the GH/IGF-1 axis is not critical for stimulation of torpor expression but activation of specific somatostatin receptors is critical. This putative role for certain somatostatin receptor subtypes in torpor induction provides a promising new approach to unravel the endocrine mechanisms of torpor regulation.
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http://dx.doi.org/10.1152/ajpregu.00191.2015DOI Listing
September 2015

Osilodrostat (LCI699), a potent 11β-hydroxylase inhibitor, administered in combination with the multireceptor-targeted somatostatin analog pasireotide: A 13-week study in rats.

Toxicol Appl Pharmacol 2015 Aug 14;286(3):224-33. Epub 2015 May 14.

Preclinical Safety, Novartis Institutes for BioMedical Research, East Hanover, NJ, USA.

The somatostatin analog pasireotide and the 11β-hydroxylase inhibitor osilodrostat (LCI699) reduce cortisol levels by distinct mechanisms of action. There exists a scientific rationale to investigate the clinical efficacy of these two agents in combination. This manuscript reports the results of a toxicology study in rats, evaluating different doses of osilodrostat and pasireotide alone and in combination. Sixty male and 60 female rats were randomized into single-sex groups to receive daily doses of pasireotide (0.3mg/kg/day, subcutaneously), osilodrostat (20mg/kg/day, orally), osilodrostat/pasireotide in combination (low dose, 1.5/0.03mg/kg/day; mid-dose, 5/0.1mg/kg/day; or high dose, 20/0.3mg/kg/day), or vehicle for 13weeks. Mean body-weight gains from baseline to Week 13 were significantly lower in the pasireotide-alone and combined-treatment groups compared to controls, and were significantly higher in female rats receiving osilodrostat monotherapy. Osilodrostat and pasireotide monotherapies were associated with significant changes in the histology and mean weights of the pituitary and adrenal glands, liver, and ovary/oviduct. Osilodrostat alone was associated with adrenocortical hypertrophy and hepatocellular hypertrophy. In combination, osilodrostat/pasireotide did not exacerbate any target organ changes and ameliorated the liver and adrenal gland changes observed with monotherapy. Cmax and AUC0-24h of osilodrostat and pasireotide increased in an approximately dose-proportional manner. In conclusion, the pasireotide and osilodrostat combination did not exacerbate changes in target organ weight or toxicity compared with either monotherapy, and had an acceptable safety profile; addition of pasireotide to the osilodrostat regimen may attenuate potential adrenal gland hyperactivation and hepatocellular hypertrophy, which are potential side effects of osilodrostat monotherapy.
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http://dx.doi.org/10.1016/j.taap.2015.05.004DOI Listing
August 2015

SOM230: a new therapeutic modality for Cushing's disease.

Chimia (Aarau) 2014 ;68(7-8):483-4

Global Discovery Chemistry Novartis Institutes of Biomedical Research CH-4002 Basel, Switzerland.

A rational drug design approach involving transposition of functional groups from SRIF into a reduced size cyclohexapeptide template has led to the discovery of SOM230, a novel, stable cyclohexapeptide somatostatin mimic which exhibits unique high affinity binding to human somatostatin receptors (sst1-5). This unique receptor subtype binding profile, in particular the exceptional high affinity binding to sst5, led to SOM230 being approved by EMEA and FDA in 2012 as the first effective pituitary directed therapeutic modality for Cushing's disease.
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http://dx.doi.org/10.2533/chimia.2014.483DOI Listing
May 2015

Lung volume quantified by MRI reflects extracellular-matrix deposition and altered pulmonary function in bleomycin models of fibrosis: effects of SOM230.

Am J Physiol Lung Cell Mol Physiol 2014 Jun 11;306(12):L1064-77. Epub 2014 Apr 11.

Novartis Institutes for BioMedical Research, Analytical Sciences and Imaging, Basel, Switzerland;

Idiopathic pulmonary fibrosis is a progressive and lethal disease, characterized by loss of lung elasticity and alveolar surface area, secondary to alveolar epithelial cell injury, reactive inflammation, proliferation of fibroblasts, and deposition of extracellular matrix. The effects of oropharyngeal aspiration of bleomycin in Sprague-Dawley rats and C57BL/6 mice, as well as of intratracheal administration of ovalbumin to actively sensitized Brown Norway rats on total lung volume as assessed noninvasively by magnetic resonance imaging (MRI) were investigated here. Lung injury and volume were quantified by using nongated or respiratory-gated MRI acquisitions [ultrashort echo time (UTE) or gradient-echo techniques]. Lung function of bleomycin-challenged rats was examined additionally using a flexiVent system. Postmortem analyses included histology of collagen and hydroxyproline assays. Bleomycin induced an increase of MRI-assessed total lung volume, lung dry and wet weights, and hydroxyproline content as well as collagen amount. In bleomycin-treated rats, gated MRI showed an increased volume of the lung in the inspiratory and expiratory phases of the respiratory cycle and a temporary decrease of tidal volume. Decreased dynamic lung compliance was found in bleomycin-challenged rats. Bleomycin-induced increase of MRI-detected lung volume was consistent with tissue deposition during fibrotic processes resulting in decreased lung elasticity, whereas influences by edema or emphysema could be excluded. In ovalbumin-challenged rats, total lung volume quantified by MRI remained unchanged. The somatostatin analog, SOM230, was shown to have therapeutic effects on established bleomycin-induced fibrosis in rats. This work suggests MRI-detected total lung volume as readout for tissue-deposition in small rodent bleomycin models of pulmonary fibrosis.
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http://dx.doi.org/10.1152/ajplung.00027.2014DOI Listing
June 2014

Evaluation of somatostatin receptor subtype expression in human neuroendocrine tumors using two sets of new monoclonal antibodies.

Regul Pept 2013 Nov 1;187:35-41. Epub 2013 Nov 1.

Novartis Pharma AG, CH-4057 Basel, Switzerland. Electronic address:

Introduction: The expression and reliable detection of somatostatin receptor subtypes (SSTR1-5) is a prerequisite for the successful use of somatostatin analogs in neuroendocrine tumors (NETs). Two sets of monoclonal antibodies (mAbs) against human SSTR1, 2A, 3 and 5 have recently been developed by two independent laboratories using rabbit and mouse hybridomas. Our aim was to evaluate the usefulness of both sets of mAbs for detection of SSTRs in NET samples as they are routinely collected in clinical practice.

Methods: Mouse and rabbit mAbs were characterized in SSTR1, 2A, 3 and 5-transfected HEK293 cells and human archival samples of pancreatic tissue and NET. Comparative analysis of mAbs was also conducted by immunostaining of a tissue microarray composed of 75 cores of NET.

Results: Immunohistochemical analysis of HEK293 cells showed that both rabbit and mouse mAbs specifically detect their cognate receptor subtype, with mild cytoplasmic cross-reactivity observed for rabbit mAbs. Both sets of mAbs labeled normal pancreatic islets and showed similar patterns of immunoreactivity in NET controls. Direct comparison of mAb sets using a NET tissue microarray revealed strong correlation between rabbit and mouse mAbs against SSTR1 and 5, and moderate correlation for SSTR3. The rabbit mAb against SSTR2A showed higher affinity for its cognate receptor than the corresponding mouse mAb, resulting in a more reliable detection of this SSTR.

Conclusions: mAbs from both sets are reliable tools for the detection of SSTR1, 3 and 5, whereas the rabbit mAb against SSTR2A is recommended for use in routine clinical testing due to its superior binding affinity.
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http://dx.doi.org/10.1016/j.regpep.2013.10.007DOI Listing
November 2013

Pasireotide (SOM230) is effective for the treatment of pancreatic neuroendocrine tumors (PNETs) in a multiple endocrine neoplasia type 1 (MEN1) conditional knockout mouse model.

Surgery 2012 Dec 24;152(6):1068-77. Epub 2012 Oct 24.

Department of Surgery, Albert Einstein College of Medicine, New York, NY 10467, USA.

Background: Pasireotide (SOM230), a long-acting somatostatin analogue (LAR), has improved agonist activity at somatostatin receptors. We tested the effect of SOM230 on insulin secretion, serum glucose concentrations, tumor growth, and survival using an MEN1 transgenic mouse model.

Methods: Eight 12-month-old conditional Men1 knockout mice with insulinoma were assessed. The treatment (n = 4) and control groups (n = 4) received monthly subcutaneous injections of SOM230 or PBS. Serum insulin and glucose levels were determined by enzyme-linked immunosorbent assay and enzymatic colorimetric assay, respectively. Tumor activity, growth, and apoptosis were determined by microPET/CT scan and histologic analysis.

Results: On day 7, there was a decrease in serum insulin levels from 1.06 ± 0.28 μg/L to 0.37 ± 0.17 μg/L (P = .0128) and a significant increase in serum glucose from 4.2 ± 0.45 mmol/L to 7.12 ± 1.06 mmol/L (P = .0075) in the treatment group but no change in the control group. Tumor size was less in the treatment group (2,098 ± 388 μm(2)) compared with the control group (7,067 ± 955 μm(2); P = .0024). Furthermore, apoptosis was increased in the treatment group (6.9 ± 1.23%) compared with the control group (0.29 ± 0.103%; P = .002).

Conclusion: SOM230 demonstrates antisecretory, antiproliferative, and proapoptotic activity in our MEN1 model of insulinoma. Further studies of the effects of SOM230 in PNET patients with MEN1 mutations are warranted.
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http://dx.doi.org/10.1016/j.surg.2012.08.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732168PMC
December 2012

Monoclonal antibodies against the human somatostatin receptor subtypes 1-5: development and immunohistochemical application in neuroendocrine tumors.

Neuroendocrinology 2012 13;95(3):232-47. Epub 2011 Dec 13.

Novartis Institutes for BioMedical Research, Basel, Switzerland.

Background: Activation of somatostatin receptors (sstr1-5) by somatostatin and its analogues exerts an inhibitory effect on hormone secretion and provides the basis for the treatment of a range of endocrine diseases such as acromegaly, Cushing's disease and neuroendocrine tumors (NET). The lack of well-characterized commercially available sstr subtype-specific antibodies prevents routine identification of the sstr expression profile in patients.

Methods: We generated and characterized new mouse monoclonal antibodies (mAbs) targeting the five human sstr subtypes using ELISA and immunohistochemistry, and tested their suitability in formalin-fixed and paraffin-embedded (FFPE) human tissues and archival samples of normal pancreatic tissue and NET.

Results: All mAbs were highly specific with no cross-reactivity. The sstr1-5 immunoreactivity in gastrointestinal NET (n=67) was correlated with clinicopathologic data. With the exception of sstr3, NET were highly positive for all receptor subtypes (42, 63, 6, 32 and 65% of tumors were positive for sstr1, sstr2a, sstr3, sstr4 and sstr5, respectively). sstr1, sstr2a and sstr5 were present at the plasma membrane and in the cytoplasm of tumor cells, whereas sstr3 and sstr4 were almost exclusively cytoplasmic. Immunoreactivity of sstr1, sstr2a and sstr4 tended to decrease as tumor aggressiveness increased. sstr5 showed an opposite pattern, with higher staining in well-differentiated carcinomas compared with well-differentiated tumors. sstr5 immunoreactivity was correlated with the presence of metastases and angioinvasion, suggesting a possible association with more aggressive behavior.

Conclusion: Determination of the sstr1-5 by immunohistochemistry using subtype-specific mAbs is feasible in FFPE tissue and may provide a tool for routine clinical practice.
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http://dx.doi.org/10.1159/000330616DOI Listing
September 2012

Effects of somatostatin analogs on glucose homeostasis in rats.

J Endocrinol 2012 Jan 10;212(1):49-60. Epub 2011 Oct 10.

Novartis Pharma AG, Novartis Institutes for Biomedical Research, Oncology, CH-4057 Basel, Switzerland.

Pasireotide (SOM230) is a multireceptor-targeted somatostatin analog with high binding affinity for sstr(1,2,3) and sstr(5). The effects of pasireotide and octreotide on blood glucose, insulin, and glucagon levels in rats were evaluated alone and in combination. Single-dose s.c. pasireotide acutely elevated plasma glucose, whereas single-dose s.c. octreotide had no or a small hypoglycemic effect. Glucose elevation with s.c. pasireotide was transient with tachyphylaxis after repeated or continuous administration. Pasireotide and octreotide caused similar inhibitory effects on insulin secretion, whereas pasireotide had a weaker inhibitory effect on glucagon secretion than octreotide. Continuous infusion of pasireotide or injection of pasireotide long-acting release (LAR) resulted in only small and transient elevations of plasma glucose. Based on these results, and differences in the sstr binding affinity of pasireotide vs octreotide, it was hypothesized that the sstr(5) vs sstr(2) receptor activation ratio is the main driver of hyperglycemia after pasireotide. The results also suggest that stronger activation of sstr(2) may counteract the hyperglycemic effect. Indeed, co-administration of octreotide, which has a high affinity for sstr(2), with a hyperglycemic dose of pasireotide did not cause significant changes in plasma glucose levels. In conclusion, although pasireotide and octreotide inhibited insulin to a similar degree, only pasireotide administration was associated with hyperglycemia. The strong glucagon inhibitory effect exhibited by octreotide but not pasireotide may explain this observation. The lack of hyperglycemia during co-administration of pasireotide and octreotide may be explained by the greater activation of sstr(2) compared with pasireotide alone, causing the insulin-glucagon balance to shift within the normoglycemic range. Extrapolation of these data to humans must account for species differences in islet cell sstr expression.
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http://dx.doi.org/10.1530/JOE-11-0224DOI Listing
January 2012

Somatostatin receptors in non-neuroendocrine malignancies: the potential role of somatostatin analogs in solid tumors.

Future Oncol 2011 Jul;7(7):895-913

Novartis Pharma AG, Forum 1, Novartis Campus, CH-4056 Basel, Switzerland.

Somatostatin receptors (sstrs) are G-protein-coupled receptors that mediate various physiological effects when activated by the neuropeptide somatostatin or its synthetic analogs. In addition to the well-documented antisecretory effects of sstr(2)-preferential somatostatin analogs octreotide and lanreotide, ligand binding to sstr initiates an inhibitory action on tumor growth. This effect may result from both indirect actions (suppression of growth factors and growth-promoting hormones [e.g., GH/IGF-1 axis] and inhibition of angiogenesis) and direct actions (activation of antigrowth activities [e.g., apoptosis]). As solid tumor cells express multiple sstrs, there is a rationale to evaluate the potential antitumor effects of pasireotide (SOM230), a multireceptor-targeted somatostatin analog with high binding affinity for sstr(1-3) and sstr(5). Pasireotide reduces systemic IGF-1 levels more potently than currently available somatostatin analogs and has been well tolerated in clinical trials.
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http://dx.doi.org/10.2217/fon.11.66DOI Listing
July 2011

Preclinical evaluation of Som230 as a radiation mitigator in a mouse model: postexposure time window and mechanisms of action.

Radiat Res 2011 Jun 29;175(6):728-35. Epub 2011 Apr 29.

Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.

The somatostatin analog SOM230 has potent radioprophylactic and radiation mitigating properties that are unrelated to cytoprotection but appear to be due to suppression of secretion of pancreatic enzymes into the intestinal lumen. To determine the maximal postirradiation time window for administration, male CD2F1 mice were exposed to 8.5-11 Gy total-body radiation; SOM230 (0.5, 2 or 5 mg/kg) or vehicle was given by twice daily subcutaneous injections for 14 days, beginning 24-72 h after irradiation, and 30-day animal survival was recorded. The contribution of the gut to systemic cytokine levels was estimated by analyzing plasma samples obtained simultaneously from the portal vein and carotid artery. The effect of SOM230 on cell trypsin secretion was assessed in vitro and intestinal proteolytic activity was measured in vivo. SOM230 was associated with a 40-60% absolute improvement in overall postirradiation survival when treatment was started 48 h after irradiation and even exhibited a statistically significant survival benefit when started at 72 h. SOM230 ameliorated the radiation-induced decrease in chemokine (C-X-C motif) ligand 9 (CXCL9). SOM230 inhibited pancreatic acinar cell trypsin secretion in vitro in a dose-dependent fashion and reduced intraluminal and intestinal tissue proteolytic activity in vivo. SOM230 is an excellent radiation mitigator with a postirradiation time window in excess of 48 h. The mechanism likely involves preservation of intestinal barrier function due to decreased secretion of pancreatic enzymes into the bowel lumen.
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http://dx.doi.org/10.1667/rr2507.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118638PMC
June 2011

Effect of SOM230 (pasireotide) on corticotropic cells: action in dogs with Cushing's disease.

Neuroendocrinology 2011 28;94(2):124-36. Epub 2011 Apr 28.

Unidad de Endocrinología, Hospital Escuela, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Buenos Aires, Argentina.

SOM230 (pasireotide) is a multiligand somatostatin (SRIF) analog able to bind to somatostatin receptor (SSTR) subtypes 1, 2, 3 and 5, and trigger antisecretory and antiproliferative signaling cascades. Canines have become in vivo models to test the pharmacological treatment of corticotropinomas because they frequently develop Cushing's disease in a spontaneous manner, due to adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. Different levels of expression of SSTR2 and SSTR5 have been shown in both mouse AtT20 cells and canine tumoral corticotropinoma cells. The objective of this study was to evaluate whether SOM230 controls both tumor cell growth and hormone synthesis, therefore controlling the disease. SOM230 was tested in dogs suffering from Cushing's disease (10 animals were treated continuously during 6 months, and another 10 were treated with 3 cycles consisting of 2 months of treatment followed by a 2-month rest period). A significant decrease in ACTH, urinary cortisol creatinine ratio, adenoma size (magnetic nuclear resonance) and improvement of clinical signs were obtained, without side effects. AtT20 cells treated with SOM230 suppressed pro-opiomelanocortin (POMC) promoter activity through SSTR2, via the G(i) α-subunit, and reduced Nur77/Nurr1 transcriptional activity. We conclude that SOM230, in addition to its well-described antisecretory effects, inhibits, as shown in AtT20 cells, ACTH synthesis at the POMC transcriptional level, an effect mediated mainly through SSTR2, and limits tumor growth. The controlled Cushing's disease in the dogs that received the treatment indicates that SOM230 has a potential therapeutic use in humans suffering from Cushing's disease.
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http://dx.doi.org/10.1159/000327429DOI Listing
January 2012

The somatostatin analog SOM230 (pasireotide) ameliorates injury of the intestinal mucosa and increases survival after total-body irradiation by inhibiting exocrine pancreatic secretion.

Radiat Res 2009 Jun;171(6):698-707

Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.

Somatostatin analogs ameliorate intestinal injury after localized irradiation. This study investigated whether SOM230, a novel, metabolically stable analog with broad receptor affinity, reduces intestinal injury and lethality in mice exposed to total-body irradiation (TBI). Male CD2F1 mice were exposed to 7-15 Gy TBI. Twice-daily administration of SOM230 (1, 4 or 10 mg/kg per day) or vehicle was started either 2 days before or 4 h after TBI and continued for either 14 or 21 days. Parameters of intestinal and hematopoietic radiation injury, bacterial translocation, and circulating cytokine levels were assessed. Animal survival was monitored for up to 30 days. SOM230 increased survival (P < 0.001) and prolonged survival time (P < 0.001) whether administration was initiated before or after TBI. There was no benefit from administration for 21 compared to 14 days. The survival benefit of SOM230 was completely reversed by co-administration of pancreatic enzymes (P = 0.009). Consistent with the presumed non-cytoprotective mechanism of action, SOM230 did not influence hematopoietic injury or intestinal crypt lethality. However, SOM230 preserved mucosal surface area (P < 0.001) and reduced bacterial translocation in a dose-dependent manner (P < 0.001). Circulating IL-12 levels were reduced in SOM230-treated mice (P = 0.007). No toxicity from SOM230 was observed. SOM230 enhances animal survival whether administration begins before or after TBI; i.e., it is effective both as a protector and as a mitigator. The mechanism likely involves reduction of intraluminal pancreatic enzymes. Because of its efficacy and favorable safety profile, SOM230 is a promising countermeasure against radiation and should undergo further development.
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http://dx.doi.org/10.1667/RR1685.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2742953PMC
June 2009

Differential effects of octreotide and pasireotide on somatostatin receptor internalization and trafficking in vitro.

J Clin Endocrinol Metab 2009 Feb 11;94(2):654-61. Epub 2008 Nov 11.

Department of Pharmacology and Toxicology, Otto-von-Guericke-University, Magdeburg, Germany.

Objective: The clinically used somatostatin analogs, octreotide and lanreotide, act primarily by binding to somatostatin receptor 2 (sst2). In contrast, the novel multireceptor ligand pasireotide (SOM230) binds with high affinity to somatostatin receptor subtypes sst1, sst2, sst3, and sst5. SOM230 is currently under clinical evaluation for treatment of acromegaly, Cushing's disease, and octreotide-resistant carcinoid tumors. However, the effects of SOM230 on internalization and postendosomal sorting of individual human somatostatin receptor subtypes have not been determined so far.

Results: Here we show that SOM230 was less potent than octreotide in inducing internalization and signaling of sst2 receptors expressed in human embryonic kidney cells. In contrast, SOM230 was more potent than octreotide in inducing internalization and signaling of sst3 and sst5 receptors. Both SOM230 and octreotide stimulated a rapid down-regulation of sst3 but not of sst2 or sst5 receptors. SOM230 and octreotide profoundly differed in their patterns of sst2-stimulated beta-arrestin mobilization. Whereas octreotide-mediated receptor activation led to the formation of stable complexes facilitating the internalization of sst2 and beta-arrestin-2 into the same endocytic vesicles, SOM230-mediated receptor activation led to the formation of unstable complexes that dissociated at or near the plasma membrane. Consequently, sst2 receptors recycled rapidly to the plasma membrane after endocytosis in SOM230-treated cells, but not in octreotide-treated cells.

Conclusion: We show that SOM230 modulates somatostatin receptor trafficking in a manner clearly distinct from octreotide and somatostatin. These findings may provide an explanation for the differential regulation of somatostatin receptor responsiveness during long-term administration of stable somatostatin analogs.
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http://dx.doi.org/10.1210/jc.2008-1919DOI Listing
February 2009

Improving oral bioavailability of peptides by multiple N-methylation: somatostatin analogues.

Angew Chem Int Ed Engl 2008 ;47(14):2595-9

CIPS at Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747-Garching, Germany.

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http://dx.doi.org/10.1002/anie.200705797DOI Listing
April 2008

Pasireotide (SOM230): development, mechanism of action and potential applications.

Authors:
Herbert A Schmid

Mol Cell Endocrinol 2008 May 19;286(1-2):69-74. Epub 2007 Sep 19.

Novartis Institutes for BioMedical Research, Oncology Research, Novartis Pharma AG, Basel, Switzerland.

Pasireotide (SOM230) is a multi-receptor ligand somatostatin analogue with high binding affinity for somatostatin receptor subtypes sst(1,2,3) and sst(5). Pasireotide potently suppresses GH, IGF-I and ACTH secretion, indicating potential efficacy in acromegaly and Cushing's disease. The prolonged inhibition of hormone secretion by pasireotide in animal models and expression of multiple sst receptors in carcinoid tumors suggests that pasireotide may have clinical advantages over octreotide in patients with carcinoid tumors. Direct and indirect antitumor activity has been observed in vitro with pasireotide, including sst receptor-mediated apoptosis and antiangiogenesis, suggesting a possible role for pasireotide in antineoplastic therapy. In summary, preclinical evidence, as well as preliminary results from clinical studies suggests that pasireotide is a promising new treatment for patients with symptoms of metastatic carcinoid tumors refractory or resistant to octreotide, de novo or persistent acromegaly, and that pasireotide has the potential to be the first directed medical therapy for Cushing's disease.
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http://dx.doi.org/10.1016/j.mce.2007.09.006DOI Listing
May 2008

SOM230, a new somatostatin analogue, is highly effective in the therapy of growth hormone/prolactin-secreting pituitary adenomas.

Clin Cancer Res 2007 May;13(9):2738-44

Istituto di Endocrinologia ed Oncologia Sperimentale del CNR e/o Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università di Napoli Federico II, Naples, Italy.

Purpose: We have previously shown that transgenic mice ubiquitously overexpressing the HMGA2 gene develop growth hormone/prolactin-secreting pituitary adenomas. This animal model has been used to evaluate the therapeutic efficacy of SOM230, a somatostatin analogue with high affinity for the somatostatin receptor subtypes 1, 2, 3, and 5, on the growth of the pituitary adenomas.

Experimental Design: Four groups of 3- and 9-month-old HMGA2 transgenic mice were treated for 3 months with a continuous s.c. injection of two different dosages of SOM230 (5 or 50 microg/kg/h), one dose of octreotide, corresponding to that used in human therapy, and a placebo, respectively. The development of the tumor before and after therapy was monitored by magnetic resonance imaging of the pituitary region and evaluation of the serum prolactin levels.

Results: The highest dose of SOM230 induced a drastic regression of the tumor, whereas octreotide was not able to induce any significant tumor regression, although tumor progression was significantly slowed down. No significant differences were observed between the animals treated with the lowest dose of SOM230 and those receiving placebo.

Conclusions: These results clearly support the efficacy of the SOM230 treatment in human pituitary adenomas secreting prolactin based on the dramatic tumor shrinkage and fall in prolactin levels. This beneficial effect could be of crucial clinical usefulness in patients bearing tumors resistant to dopaminergic drugs.
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http://dx.doi.org/10.1158/1078-0432.CCR-06-2505DOI Listing
May 2007

Pasireotide, a multiple somatostatin receptor subtypes ligand, reduces cell viability in non-functioning pituitary adenomas by inhibiting vascular endothelial growth factor secretion.

Endocr Relat Cancer 2007 Mar;14(1):91-102

Section of Endocrinology, Department of Biomedical Sciences and Advanced Therapies, University of Ferrara, Via Savonarola 9, 44100 Ferrara, Italy.

Somatostatin (SRIF) analogs have been employed in medical therapy of non-functioning pituitary adenomas (NFA), with contrasting results. Previous evidence showed that SRIF can exert its antiproliferative effects by reducing vascular endothelial growth factor (VEGF) secretion and action, and that VEGF expression may be related to pituitary tumor growth. The aim of our study was to clarify the possible effects of a multireceptor SRIF ligand on VEGF secretion and cell proliferation in human NFA primary cultures. We assessed the expression of SRIF receptors (SSTR1-5), the in vitro effects on VEGF secretion, and on cell viability of SRIF and of the stable SRIF analog pasireotide (SOM230), which activates SSTR1, 2, 3, and 5. Twenty-five NFA were examined by RT-PCR for expression of alpha-subunit, SSTR, VEGF, and VEGF receptors 1 (VEGF-R1) and 2 (VEGF-R2). Primary cultures were tested with SRIF and with pasireotide. All NFA samples expressed alpha-sub, VEGF and VEGFR-1 and 2, while SSTR expression pattern was highly variable. Two different groups were identified according to VEGF secretion inhibition by SRIF. VEGF secretion and cell viability were reduced by SRIF and pasireotide in the 'responder' group, but not in the 'non-responder' group, including NFA expressing SSTR5. SRIF and pasireotide completely blocked forskolin-induced VEGF secretion. In addition, SRIF and pasireotide completely abrogated the promoting effects of VEGF on NFA cell viability. Our data demonstrate that pasireotide can inhibit NFA cell viability by inhibiting VEGF secretion, and suggest that the multireceptor-SSTR agonist pasireotide might be useful in medical therapy of selected NFA.
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http://dx.doi.org/10.1677/ERC-06-0026DOI Listing
March 2007

SOM230 inhibits insulin-like growth factor-I action in mammary gland development by pituitary independent mechanism: mediated through somatostatin subtype receptor 3?

Mol Endocrinol 2006 Feb 13;20(2):426-36. Epub 2005 Oct 13.

Neuroendocrine Unit, New York University School of Medicine, New York, New York 10016, USA.

Somatostatin analogs (SAs) treat acromegaly by lowering pituitary GH secretion, which, in turn, lowers systemic IGF-I. The profound systemic effect is often greater than expected in the face of only partial GH suppression. Here we report that the SA SOM230 can also act by a nonpituitary-mediated inhibition of IGF-I action. SOM230 inhibited mammary development in intact and hypophysectomized female rats, a process requiring IGF-I. IGF-I overcame this inhibition. SOM230 also inhibited other actions of IGF-I (inhibition of apoptosis, phosphorylation of insulin receptor substrate-1, and cell division). SOM230 did not reduce IGF-I mRNA abundance in mammary gland but did stimulate IGF binding protein 5 (IGFBP5). IGFBP5 was 3.75 times higher in mammary epithelium of SOM230 than in placebo animals (P < 0.001). Administration of IGFBP-5 also inhibited GH-induced mammary development (P < 0.001). Measurement of sstr(1-5) (somatostatin subtype receptor) by real-time RT-PCR revealed that the mammary glands had an abundance of sstr(3) and lower amounts of sstr(4) and sstr(5) but no sstr(1) or sstr(2.) That mammary development was also inhibited to a lesser degree than SOM230 by octreotide, whose main action is through sstr(2), strongly suggests that sstr(3) is at least in part mediating the effects of the SAs. We conclude that 1) SAs inhibit IGF-I action in the mammary gland through a novel nonpituitary mechanism; 2) IGFBP-5, here shown to inhibit pubertal mammary development, might mediate the effect; and 3) Measurement of available sstr receptors in the mammary gland suggests that sstr(3) mediates the SA activity, but sstr(5) is also a possible mediator.
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http://dx.doi.org/10.1210/me.2005-0283DOI Listing
February 2006

Regulation of ghrelin secretion by somatostatin analogs in rats.

Eur J Endocrinol 2005 Jun;152(6):887-94

Novartis Institutes for Biomedical Research, Basel, Switzerland.

Objective: Ghrelin is a hormone present in the plasma in two forms: octanoylated and des-octanoylated ghrelin. In pathophysiological conditions such as Prader-Willi syndrome and ghrelinoma, elevated ghrelin plasma levels are associated with pathological obesity. Clinical studies have shown that somatostatin downregulates ghrelin plasma levels in healthy volunteers. The aim of this study was to investigate the effects of two somatostatin analogues, SOM230 and octreotide, on ghrelin secretion in rats.

Methods: Ghrelin secretion was either unstimulated or stimulated by overnight fasting. Treatment with SOM230 and octreotide was either acute (s.c. injection 1 h before blood sampling) or prolonged (continuous s.c. infusion via 14-day osmotic minipumps).

Results: Acute treatment with octreotide dose-dependently inhibited unstimulated and stimulated secretion of total and active ghrelin. SOM230 (30 microg/kg) inhibited active ghrelin in fasted rats. Lower doses had no effect. After 7 days of treatment, active ghrelin was strongly inhibited by both compounds in fasted animals, with a stronger effect for octreotide. Lower inhibition was achieved in fed rats. After 14 days, the inhibition with octreotide in fasted rats was lower and SOM230 had no effect. Somatostatin receptor expression analysis in the rat glandular stomach revealed a predominant sst(1) and sst(2) expression, low expression of sst(3) and sst(4), and hardly detectable sst(5) mRNA expression.

Conclusions: Somatostatin analogues may be useful for the inhibition of physiologically elevated ghrelin plasma levels. This inhibition appears to be mediated by sst(2) receptors in the rat, and desensitizes after 14 days of treatment.
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http://dx.doi.org/10.1530/eje.1.01914DOI Listing
June 2005

Binding and functional properties of the novel somatostatin analogue KE 108 at native mouse somatostatin receptors.

Neuropharmacology 2005 May;48(6):881-93

Dipartimento di Fisiologia e Biochimica G. Moruzzi, Università di Pisa, 56127 Pisa, Italy.

Clinically used somatostatin (SRIF) analogs, octreotide and lanreotide, act primarily by binding to SRIF receptor subtype 2 (sst2). In contrast, the recently described multiligand SOM230 binds with high affinity to sst(1-3) and sst5 and KE 108 is characterised as a high affinity ligand for all five SRIF receptors. In tumoural mouse corticotrophs (AtT-20 cells) and in mouse hippocampus, binding and functional features of KE 108 were examined and compared to SRIF-14, octreotide and SOM230. In AtT-20 cells, KE 108 bound with high affinity at [125I]LTT-SRIF-28-labelled sites similarly to SRIF-14, octreotide and SOM230. At the functional level, all four ligands increased guanosine-5'-O-(3-[35S]thio)-triphosphate binding and decreased cAMP accumulation or intracellular Ca2+ concentration through G(i/o) proteins. In hippocampal slices, KE 108, octreotide and SOM230 also bound with high affinity at [125I]LTT-SRIF-28-labelled sites similarly to SRIF-14, but KE 108, octreotide or SOM230 did not influence spontaneous epileptiform activity which was, in contrast, inhibited by SRIF-14. In conclusion, this study demonstrates that KE 108 has high affinity for native mouse SRIF receptors. Functionally, KE 108 mediates SRIF action at sst(2/5) in corticotrophs whereas it does not mimic the SRIF-induced inhibition of hippocampal excitation suggesting that the high potency and efficacy of a synthetic ligand to all known SRIF receptors may not reproduce entirely the effects of the natural SRIF.
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http://dx.doi.org/10.1016/j.neuropharm.2004.12.019DOI Listing
May 2005

Distinct functional properties of native somatostatin receptor subtype 5 compared with subtype 2 in the regulation of ACTH release by corticotroph tumor cells.

Am J Physiol Endocrinol Metab 2005 Aug 15;289(2):E278-87. Epub 2005 Mar 15.

Dept. of Internal Medicine, section Endocrinology, Erasmus MC, 3015 GE Rotterdam, The Netherlands.

In a series of human corticotroph adenomas, we recently found predominant mRNA expression of somatostatin (SS) receptor subtype 5 (sst5). After 72 h, the multiligand SS analog SOM230, which has a very high sst5 binding affinity, but not Octreotide (OCT), significantly inhibited basal ACTH release. To further explore the role of sst5 in the regulation of ACTH release, we conducted additional studies with mouse AtT-20 cells. SOM230 showed a 7-fold higher ligand binding affinity and a 19-fold higher potency in stimulating guanosine 5'-O-(3-thiotriphosphate) binding in AtT-20 cell membranes compared with OCT. SOM230 potently suppressed CRH-induced ACTH release, which was not affected by 48-h dexamethasone (DEX) pretreatment. However, DEX attenuated the inhibitory effects of OCT on ACTH release, whereas it increased the inhibitory potency of BIM-23268, an sst5-specific analog, on ACTH release. Quantitative PCR analysis showed that DEX lowered sst(2A+2B) mRNA expression significantly after 24 and 48 h, whereas sst5 mRNA levels were not significantly affected by DEX treatment. Moreover, Scatchard analyses showed that DEX suppressed maximum binding capacity (B(max)) by 72% when 125I-Tyr3-labeled OCT was used as radioligand, whereas B(max) declined only by 17% when AtT-20 cells were treated with [125I-Tyr11]SS-14. These data suggest that the sst5 protein, compared with sst2, is more resistant to glucocorticoids. Finally, after SS analog preincubation, compared with OCT both SOM230 and BIM-23268 showed a significantly higher inhibitory effect on CRH-induced ACTH release. In conclusion, our data support the concept that the sst5 receptor might be a target for new therapeutic agents to treat Cushing's disease.
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http://dx.doi.org/10.1152/ajpendo.00004.2005DOI Listing
August 2005
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