251
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Hypoxia effects on proangiogenic factors in human umbilical vein endothelial cells: functional role of the peptide somatostatin. Naunyn Schmiedebergs Arch Pharmacol 2011; 383:593-612. [DOI: 10.1007/s00210-011-0625-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 03/23/2011] [Indexed: 12/15/2022]
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252
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Strosberg JR, Cheema A, Kvols LK. A Review of Systemic and Liver-Directed Therapies for Metastatic Neuroendocrine Tumors of the Gastroenteropancreatic Tract. Cancer Control 2011; 18:127-137. [DOI: 10.1177/107327481101800207] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
Affiliation(s)
- Jonathan R. Strosberg
- Department of Gastrointestinal Oncology at the H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida
| | - Asima Cheema
- Department of Gastrointestinal Oncology at the H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida
| | - Larry K. Kvols
- Department of Gastrointestinal Oncology at the H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida
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253
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Abstract
Somatostatin analogs (SA) are widely used in acromegaly, either as first-line or adjuvant treatment after surgery. First-line treatment with these drugs is generally used in the patients with macroadenomas or in those with clinical conditions so severe as to prevent unsafe reactions during anesthesia. Generally, the response to SA takes into account both control of GH and IGF-I excess, with consequent improvement of clinical symptoms directly related to GH and IGF-I excess, and tumor shrinkage. This latter effect is more prominent in the patients treated first-line and bearing large macroadenomas, but it is also observed in patients with microadenomas, even with little clinical implication. Predictors of response are patients' gender, age, initial GH and IGF-I levels, and tumor mass, as well as adequate expression of somatostatin receptor types 2 and 5, those with the highest affinity for octreotide and lanreotide. Only sporadic cases of somatostatin receptor gene mutation or impaired signaling pathways have been described in GH-secreting tumors so far. The response to SA also depends on treatment duration and dosage of the drug used, so that a definition of resistance based on short-term treatments using low doses of long-acting SA is limited. Current data suggest that response to these drugs is better analyzed taking together biochemical and tumoral effects because only the absence of both responses might be considered as a poor response or resistance. This latter evidence seems to occur in 25% of treated patients after 12 months of currently available long-acting SA.
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Affiliation(s)
- Annamaria Colao
- Department of Clinical and Molecular Endocrinology and Oncology, University “Federico II,” Naples, Italy.
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254
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Recent trends and observations in the design of high-quality screening collections. Future Med Chem 2011; 3:751-66. [DOI: 10.4155/fmc.11.15] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The design of a high-quality screening collection is of utmost importance for the early drug-discovery process and provides, in combination with high-quality assay systems, the foundation of future discoveries. Herein, we review recent trends and observations to successfully expand the access to bioactive chemical space, including the feedback from hit assessment interviews of high-throughput screening campaigns; recent successes with chemogenomics target family approaches, the identification of new relevant target/domain families, diversity-oriented synthesis and new emerging compound classes, and non-classical approaches, such as fragment-based screening and DNA-encoded chemical libraries. The role of in silico library design approaches are emphasized.
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255
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Guitot K, Larregola M, Pradhan TK, Vasse JL, Lavielle S, Bertus P, Szymoniak J, Lequin O, Karoyan P. The Combination of Prolinoamino Acids and Cyclopropylamino Acids Leads to Fully Functionalized, Stable β-Turns in Water. Chembiochem 2011; 12:1039-42. [DOI: 10.1002/cbic.201000707] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Indexed: 12/17/2022]
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256
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Wolkenberg SE, Zhao Z, Thut C, Maxwell JW, McDonald TP, Kinose F, Reilly M, Lindsley CW, Hartman GD. Design, Synthesis, and Evaluation of Novel 3,6-Diaryl-4-aminoalkoxyquinolines as Selective Agonists of Somatostatin Receptor Subtype 2. J Med Chem 2011; 54:2351-8. [PMID: 21395312 DOI: 10.1021/jm101501b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Scott E. Wolkenberg
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Zhijian Zhao
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Catherine Thut
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Jill W. Maxwell
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Terrence P. McDonald
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Fumi Kinose
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Michael Reilly
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - Craig W. Lindsley
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
| | - George D. Hartman
- Departments of †Medicinal Chemistry, ‡Ophthalmics Research, and §Drug Metabolism, Merck Research Laboratories, Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486, United States
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257
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Ghosh M, Schonbrunn A. Differential temporal and spatial regulation of somatostatin receptor phosphorylation and dephosphorylation. J Biol Chem 2011; 286:13561-73. [PMID: 21343287 DOI: 10.1074/jbc.m110.215723] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The G(i)-coupled somatostatin 2A receptor (sst2A) mediates many of the neuromodulatory and neuroendocrine actions of somatostatin (SS) and is targeted by the SS analogs used to treat neuroendocrine tumors. As for other G protein-coupled receptors, agonists stimulate sst2A receptor phosphorylation on multiple residues, and phosphorylation at different sites has distinct effects on receptor internalization and uncoupling. To elucidate the spatial and temporal regulation of sst2A receptor phosphorylation, we examined agonist-stimulated phosphorylation of multiple receptor GPCR kinase sites using phospho-site-specific antibodies. SS increased receptor phosphorylation sequentially, first on Ser-341/343 and then on Thr-353/354, followed by receptor internalization. Reversal of receptor phosphorylation was determined by the duration of prior agonist exposure. In acutely stimulated cells, in which most receptors remained on the cell surface, dephosphorylation occurred only on Thr-353/354. In contrast, both Ser-341/343 and Thr-353/354 were rapidly dephosphorylated when cells were stimulated long enough to allow receptor internalization before agonist removal. Consistent with these observations, dephosphorylation of Thr-353/354 was not affected by either hypertonic sucrose or dynasore, which prevent receptor internalization, whereas dephosphorylation of Ser-341/343 was completely blocked. An okadaic acid- and fostriecin-sensitive phosphatase catalyzed the dephosphorylation of Thr-353/354 both intracellularly and at the cell surface. In contrast, dephosphorylation of Ser-341/343 was insensitive to these inhibitors. Our results show that the phosphorylation and dephosphorylation of neighboring GPCR kinase sites in the sst2A receptor are subject to differential spatial and temporal regulation. Thus, the pattern of receptor phosphorylation is determined by the duration of agonist stimulation and compartment-specific enzymatic activity.
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Affiliation(s)
- Madhumita Ghosh
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas 77225, USA
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258
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Robertson CR, Flynn SP, White HS, Bulaj G. Anticonvulsant neuropeptides as drug leads for neurological diseases. Nat Prod Rep 2011; 28:741-62. [PMID: 21340067 DOI: 10.1039/c0np00048e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Anticonvulsant neuropeptides are best known for their ability to suppress seizures and modulate pain pathways. Galanin, neuropeptide Y, somatostatin, neurotensin, dynorphin, among others, have been validated as potential first-in-class anti-epileptic or/and analgesic compounds in animal models of epilepsy and pain, but their therapeutic potential extends to other neurological indications, including neurodegenerative and psychatric disorders. Disease-modifying properties of neuropeptides make them even more attractive templates for developing new-generation neurotherapeutics. Arguably, efforts to transform this class of neuropeptides into drugs have been limited compared to those for other bioactive peptides. Key challenges in developing neuropeptide-based anticonvulsants are: to engineer optimal receptor-subtype selectivity, to improve metabolic stability and to enhance their bioavailability, including penetration across the blood–brain barrier (BBB). Here, we summarize advances toward developing systemically active and CNS-penetrant neuropeptide analogs. Two main objectives of this review are: (1) to provide an overview of structural and pharmacological properties for selected anticonvulsant neuropeptides and their analogs and (2) to encourage broader efforts to convert these endogenous natural products into drug leads for pain, epilepsy and other neurological diseases.
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Affiliation(s)
- Charles R Robertson
- College of Pharmacy, Department of Medicinal Chemistry, 421 Wakara Way, STE. 360 Salt Lake City, UT 84108, USA
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259
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Nagel F, Doll C, Pöll F, Kliewer A, Schröder H, Schulz S. Structural determinants of agonist-selective signaling at the sst(2A) somatostatin receptor. Mol Endocrinol 2011; 25:859-66. [PMID: 21330405 DOI: 10.1210/me.2010-0407] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The clinically used somatostatin (SS-14) analogs octreotide and pasireotide (SOM230) stimulate distinct species-specific patterns of sst(2A) somatostatin receptor phosphorylation and internalization. Like SS-14, octreotide promotes the phosphorylation of at least six carboxyl-terminal serine and threonine residues, namely S341, S343, T353, T354, T356, and T359, which in turn leads to a robust endocytosis of both rat and human sst(2A) receptors. Unlike SS-14, pasireotide fails to induce any substantial phosphorylation or internalization of the rat sst(2A) receptor. Nevertheless, pasireotide is able to stimulate a selective phosphorylation of S341 and S343 of the human sst(2A) receptor followed by a clearly detectable receptor sequestration. Here, we show that transplantation of amino acids 1-180 of the human sst(2A) receptor to the rat sst(2A) receptor facilitates pasireotide-induced internalization. Conversely, construction of a rat-human sst(2A) chimera conferred resistance to pasireotide-induced internalization. We then created a series of site-directed mutants leading to the identification of amino acids 27, 30, 163, and 164 that when exchanged to their human counterparts facilitated pasireotide-driven S341/S343 phosphorylation and internalization of the rat sst(2A) receptor. Exchange of these amino acids to their rat counterparts completely blocked the pasireotide-mediated internalization of the human sst(2A) receptor. Notably, octreotide and SS-14 stimulated a full phosphorylation and internalization of all mutant sst(2A) receptors tested. Together, these findings suggest that pasireotide activates the sst(2A) receptor via a molecular switch that is structurally and functionally distinct from that turned on during octreotide-driven sst(2A) activation.
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Affiliation(s)
- Falko Nagel
- Department of Pharmacology and Toxicology, University Hospital Jena, Friedrich Schiller University, Drackendorfer Strasse 1, D-07747 Jena, Germany
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260
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Yim CB, van der Wildt B, Dijkgraaf I, Joosten L, Eek A, Versluis C, Rijkers DTS, Boerman OC, Liskamp RMJ. Spacer effects on in vivo properties of DOTA-conjugated dimeric [Tyr3]octreotate peptides synthesized by a "Cu(I)-click" and "sulfo-click" ligation method. Chembiochem 2011; 12:750-60. [PMID: 21328514 DOI: 10.1002/cbic.201000639] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Indexed: 12/11/2022]
Abstract
We report on the SSTR2-binding properties of a series of four dimeric [Tyr3]octreotate analogues with different spacer lengths (nine, 19, 41, and 57 atoms) between the peptides. Two analogues (9 and 57 atoms) were selected as precursors for the design, synthesis, and biological evaluation of DOTA-conjugated dimeric [Tyr3]octreotate analogues for tumor targeting. These compounds were synthesized by using a two-stage click ligation procedure: a Cu(I) -catalyzed 1,3-dipolar cycloaddition ("copper-click" reaction) and a thio acid/sulfonyl azide amidation ("sulfo-click" reaction). The IC(50) values of these DOTA-conjugated [Tyr3]octreotate analogues were comparable, and internalization studies showed that the nine-atom (111) In-DOTA-labeled [Tyr3]octreotate dimer had rapid and high receptor binding. Biodistribution studies with BALB/c nude mice bearing subcutaneous AR42J tumors showed that the (111) In-labeled [Tyr3]octreotate dimer (nine atoms) had a high tumor uptake at 1 h p.i. (38.8 ± 8.3 % ID g(-1) ), and excellent tumor retention at 4 h p.i. (40.9 ± 2.5 % ID g(-1) ). However, the introduction of the extended hydrophilic 57 atoms spacer led to rapid clearance from the circulation; this limited tumor accumulation of the radiotracer (21.4 ± 4.9 % ID g(-1) at 1 h p.i.). These findings provide important insight on dimerization and spacer effects on the in vivo properties of DOTA-conjugated [Tyr3]octreotate dimers.
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Affiliation(s)
- Cheng-Bin Yim
- Division of Medicinal Chemistry and Chemical Biology, Utrecht Institute for Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Utrecht University, PO Box 80082, 3508 TB Utrecht, The Netherlands
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261
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Kuil J, Velders AH, van Leeuwen FWB. Multimodal tumor-targeting peptides functionalized with both a radio- and a fluorescent label. Bioconjug Chem 2011; 21:1709-19. [PMID: 20812730 DOI: 10.1021/bc100276j] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The use of monolabeled tumor-targeting peptides for molecular imaging is widespread. However, it is often desirable to use the same compound for different clinical applications, e.g., combined pre- and intraoperative tumor detection. On the basis of their detection sensitivity, the combination of radioactivity and fluorescence is probably the most valuable in multimodal molecular imaging. In this review, we compare multimodal peptide derivatives and discuss the influence of the diagnostic labels on receptor affinity and biodistribution. On the basis of the described constructs, we propose improvements for the design of future multimodal tumor-targeting peptide derivatives.
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Affiliation(s)
- Joeri Kuil
- Division of Diagnostic Oncology, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
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262
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Somatostatin Receptors in Lung Cancer: From Function to Molecular Imaging and Therapeutics. ACTA ACUST UNITED AC 2011; 10:69-76. [PMID: 25663834 DOI: 10.6058/jlc.2011.10.2.69] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Lung cancer is a deadly disease that is difficult to diagnose and even more difficult to treat effectively. Many pathways are known to affect tumor growth, and targeting these pathways provides the cornerstone by which cancer is treated. Somatostatin receptors (SSTR) are a family of G protein coupled receptors that signal to alter hormonal secretion, increase apoptosis, and decrease cellular proliferation. These receptors are expressed in many normal and malignant cells, including both small cell and non-small cell lung cancer. Synthetic analogs of SSTRs are commercially available, but their effects in lung cancer are still largely uncertain. Signaling pathway studies have shown that SSTRs signal through phosphotyrosine phosphatases to induce apoptosis as well as to decrease cell proliferation. Radiolabeled SSTR2 analogs are utilized for radiographic imaging of tumors, which, when combined with positron emission tomography-computed tomography (PET-CT) may improve detection of lung cancer. These radiolabeled SSTR2 analogs also hold promise for targeted chemotherapy as well as radiotherapy. In this review, we summarize what is known about SSTRs and focus our discussion on the knowledge as it relates to lung cancer biology, as well as discuss current and future uses of these receptors for imaging and therapy of lung cancer.
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263
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War SA, Somvanshi RK, Kumar U. Somatostatin receptor-3 mediated intracellular signaling and apoptosis is regulated by its cytoplasmic terminal. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:390-402. [PMID: 21194548 DOI: 10.1016/j.bbamcr.2010.12.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/25/2010] [Accepted: 12/13/2010] [Indexed: 12/25/2022]
Abstract
In the present study, we describe the role of cytoplasmic terminal (C-tail) domain in regulating coupling to adenylyl cyclase, signaling, and apoptosis in human embryonic kidney (HEK-293) cells transfected with wild type (wt)-hSSTR3 and C-tail deleted mutants. Cells transfected with wt-hSSTR3 and C-tail mutants show comparable membrane expression; however, display decreased expression in presence of agonist. wt-hSSTR3 exists as preformed homodimer at cell surface in basal conditions and decreases in response to agonist. Cells expressing C-tail mutants also show evidence of homodimerization with the same intensity as wt-hSSTR3. The agonist-dependent inhibition of cyclic adenosine monophosphate (cAMP) was lost in cells expressing C-tail mutants. Agonist treatment in cells expressing wt-hSSTR3 resulted in inhibition of cell proliferation, increased expression of PARP-1, and TUNEL positivity in proliferating cell nuclear antigen (PCNA)-positive cells. The agonist mediated increase in membrane expression of protein tyrosine phosphatase (PTP) seen with wt-hSSTR3 was diminished in C-tail mutants, which was accompanied with the loss of receptor's ability to induce apoptosis. Taken together, our data provide new insights into C-tail-dependent regulation of cell signaling and apoptosis by hSSTR3.
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Affiliation(s)
- Sajad A War
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, The University of British Columbia, Vancouver, BC V6T1Z3, Canada
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264
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Cakir M, Dworakowska D, Grossman A. Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 2--clinical implications. J Cell Mol Med 2010; 14:2585-91. [PMID: 20629988 PMCID: PMC4373478 DOI: 10.1111/j.1582-4934.2010.01125_1.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Accepted: 04/29/2010] [Indexed: 01/03/2023] Open
Abstract
Introduction
SSTR subtype tissue distribution and its relevance to tumour imaging and treatment
Conclusions
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Affiliation(s)
- Mehtap Cakir
- Selcuk University, Meram School of Medicine, Division of Endocrinology and Metabolism, Konya, Turkey.
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265
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Iida S, Miki Y, Ono K, Akahira JI, Suzuki T, Ishida K, Watanabe M, Sasano H. Novel classification based on immunohistochemistry combined with hierarchical clustering analysis in non-functioning neuroendocrine tumor patients. Cancer Sci 2010; 101:2278-85. [PMID: 20682006 PMCID: PMC11159394 DOI: 10.1111/j.1349-7006.2010.01657.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Somatostatin analogues ameliorated many symptoms caused by neuroendocrine tumors (NET), but their antitumor activities are limited especially in non-functioning cases. An overactivation of signaling pathways under receptor tyrosine-kinase (RTK) has been recently demonstrated in some NET patients, but its details have remained largely unknown. Therefore, in this study, we immunolocalized therapeutic factors and evaluated the data to study the clinical significance of the molecules in non-functioning Japanese gastrointestinal NET. Fifty-two NET cases were available for examination in this study and expression of somatostatin receptor (sstr) 1, 2A, 2B, 3 and 5, activated form of mammalian target of rapamycin (mTOR), eukaryotic initiation factor 4-binding protein 1 (4EBP1), ribosomal protein s6 (S6), extracellular signal-regulated kinase (ERK) and insulin-like growth factor 1 receptor (IGF-1R) was evaluated using immunohistochemistry. We then studied the correlation among the immunohistochemical results of the individual cases using hierarchical clustering analysis. Results of clustering analysis demonstrated that NET cases were basically classified into Cluster I and II. Cluster I was associated with higher expression of sstr1, 2B and 3 and Cluster II was characterized by an activation of the PI3K/Akt pathway and IGF-1R and higher proliferative status. Cluster II was further classified into Cluster IIa and IIb. Cluster IIa was associated with higher expression of sstr1 and 5 and higher proliferative status and Cluster IIb was characterized by ERK activation. Hierarchical clustering analysis of immunoreactivity of the therapeutic factors can classify NET cases into three distinctive groups and the medical treatment may be determined according to this novel classification method for non-functioning NET patients.
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Affiliation(s)
- Shinya Iida
- Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
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266
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Shupe T, Petersen BE. Potential applications for cell regulatory factors in liver progenitor cell therapy. Int J Biochem Cell Biol 2010; 43:214-21. [PMID: 20851776 DOI: 10.1016/j.biocel.2010.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 08/24/2010] [Accepted: 09/06/2010] [Indexed: 12/18/2022]
Abstract
Orthotopic liver transplant represent the state of the art treatment for terminal liver pathologies such as cirrhosis in adults and hemochromatosis in neonates. A limited supply of transplantable organs in relationship to the demand means that many patients will succumb to disease before an organ becomes available. One promising alternative to liver transplant is therapy based on the transplant of liver progenitor cells. These cells may be derived from the patient, expanded in vitro, and transplanted back to the diseased liver. Inborn metabolic disorders represent the most attractive target for liver progenitor cell therapy, as many of these disorders may be corrected by repopulation of only a portion of the liver by healthy cells. Another potential application for liver progenitor cell therapy is the seeding of bio-artificial liver matrix. These ex vivo bioreactors may someday be used to bridge critically ill patients to other treatments. Conferring a selective growth advantage to the progenitor cell population remains an obstacle to therapy development. Understanding the molecular signaling mechanisms and micro-environmental cues that govern liver progenitor cell phenotype may someday lead to strategies for providing this selective growth advantage. The discovery of a population of cells within the bone marrow possessing the ability to differentiate into hepatocytes may provide an easily accessible source of cells for liver therapies.
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Affiliation(s)
- Thomas Shupe
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida, College of Medicine, Gainesville, FL 32610-0275, USA.
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267
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Oberg KE, Reubi JC, Kwekkeboom DJ, Krenning EP. Role of somatostatins in gastroenteropancreatic neuroendocrine tumor development and therapy. Gastroenterology 2010; 139:742-53, 753.e1. [PMID: 20637207 DOI: 10.1053/j.gastro.2010.07.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 07/06/2010] [Accepted: 07/08/2010] [Indexed: 12/02/2022]
Abstract
The incidence and prevalence of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) have increased in the past 20 years. GEP-NETs are heterogeneous tumors, in terms of clinical and biological features, that originate from the pancreas or the intestinal tract. Some GEP-NETs grow very slowly, some grow rapidly and do not cause symptoms, and others cause hormone hypersecretion and associated symptoms. Most GEP-NETs overexpress receptors for somatostatins. Somatostatins inhibit the release of many hormones and other secretory proteins; their effects are mediated by G protein-coupled receptors that are expressed in a tissue-specific manner. Most GEP-NETs overexpress the somatostatin receptor SSTR2; somatostatin analogues are the best therapeutic option for functional neuroendocrine tumors because they reduce hormone-related symptoms and also have antitumor effects. Long-acting formulations of somatostatin analogues stabilize tumor growth over long periods. The development of radioactive analogues for imaging and peptide receptor radiotherapy has improved the management of GEP-NETs. Peptide receptor radiotherapy has significant antitumor effects, increasing overall survival times of patients with tumors that express a high density of SSTRs, particularly SSTR2 and SSTR5. The multi-receptor somatostatin analogue SOM230 (pasireotide) and chimeric molecules that bind SSTR2 and the dopamine receptor D2 are also being developed to treat patients with GEP-NETs. Combinations of radioactive labeled and unlabeled somatostatin analogues and therapeutics that inhibit other signaling pathways, such as mammalian target of rapamycin (mTOR) and vascular endothelial growth factor, might be the most effective therapeutics for GEP-NETs.
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Affiliation(s)
- Kjell E Oberg
- Department of Endocrine Oncology, University Hospital, Uppsala, Sweden.
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268
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Chen K, Conti PS. Target-specific delivery of peptide-based probes for PET imaging. Adv Drug Deliv Rev 2010; 62:1005-22. [PMID: 20851156 DOI: 10.1016/j.addr.2010.09.004] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 09/08/2010] [Accepted: 09/08/2010] [Indexed: 12/19/2022]
Abstract
Positron emission tomography (PET) is one of the most rapidly growing areas of medical imaging, with many applications in the clinical management of patients with various diseases. The principal goal of PET imaging is to visualize, characterize, and measure biological processes at the cellular, subcellular, and molecular level in living subjects with non-invasive procedures. PET imaging takes advantage of the traditional diagnostic imaging techniques and introduces positron-emitting probes to determine the expression of indicative molecular targets at different stages of disease. During the last decade, advances in molecular biology have revealed an increasing number of potential molecular targets, including peptide receptors and peptide-related biomolecules. With the help of sophisticated bioconjugation and radiolabeling techniques, numerous peptide-based agents have been developed and evaluated for delivery of PET radionuclides to the specific molecular targets in preclinical and clinical studies. As compared to macromolecules, such as proteins or antibodies, low-molecular-weight peptides have their distinctive advantages and predominantly demonstrate their favorable pharmacokinetics for in vivo PET applications. This review summarizes the criteria of peptide-based PET probes design, the selection of radioisotopes, labeling methods, and provides an overview of the current status and trends in the development of target-specific peptide-based probes with respect to their unique PET imaging applications.
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269
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Lee S, Xie J, Chen X. Peptides and peptide hormones for molecular imaging and disease diagnosis. Chem Rev 2010; 110:3087-111. [PMID: 20225899 DOI: 10.1021/cr900361p] [Citation(s) in RCA: 253] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Seulki Lee
- Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 31 Center Drive, Suite 1C14, Bethesda, Maryland 20892-2281, USA
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270
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Di Cianni A, Carotenuto A, Brancaccio D, Novellino E, Reubi JC, Beetschen K, Papini AM, Ginanneschi M. Novel Octreotide Dicarba-analogues with High Affinity and Different Selectivity for Somatostatin Receptors. J Med Chem 2010; 53:6188-97. [DOI: 10.1021/jm1005868] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Alessandra Di Cianni
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
| | - Alfonso Carotenuto
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Diego Brancaccio
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Ettore Novellino
- Department of Pharmaceutical Chemistry and Toxicology, University of Napoli, Via Domenico Montesano 49, I-80131 Napoli, Italy
| | - Jean Claude Reubi
- Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, CH-3010 Berne, Switzerland
| | - Karin Beetschen
- Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, CH-3010 Berne, Switzerland
| | - Anna Maria Papini
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
| | - Mauro Ginanneschi
- Laboratory of Peptides & Proteins, Chemistry & Biology, University of Firenze, Via della Lastruccia 13, I-50019 Sesto Fiorentino, Italy
- Department of Chemistry “Ugo Schiff”, University of Firenze, Via della Lastruccia 5-13, I-50019, Sesto Fiorentino, Italy
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271
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Sawai Y, Yamane T, Ikeuchi M, Kawaguchi S, Yamada M, Yamano M. Process for the Preparation of an Amorphous, Peptide-like Diabetes Drug: Approach to a Chromatography-Free Process. Org Process Res Dev 2010. [DOI: 10.1021/op100084r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yasuhiro Sawai
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
| | - Taihei Yamane
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
| | - Motoki Ikeuchi
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
| | - Shinji Kawaguchi
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
| | - Masatoshi Yamada
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
| | - Mitsuhisa Yamano
- Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan
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272
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Strosberg J, Kvols L. Antiproliferative effect of somatostatin analogs in gastroenteropancreatic neuroendocrine tumors. World J Gastroenterol 2010; 16:2963-70. [PMID: 20572298 PMCID: PMC2890935 DOI: 10.3748/wjg.v16.i24.2963] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Somatostatin analogs were initially developed for the control of hormonal syndromes associated with neuroendocrine tumors (NETs). In recent years, accumulating data has supported their role as antiproliferative agents, capable of stabilizing tumor growth in patients with metastatic neuroendocrine malignancies, including carcinoid and pancreatic endocrine tumors. A phase III, randomized, placebo-controlled trial has now demonstrated that octreotide long-acting repeatable (LAR) 30 mg can significantly prolong time to tumor progression among patients with metastatic midgut NETs regardless of functional status, chromogranin A level or age. In addition to significantly lengthening time to tumor progression in the overall study population, subset analysis suggests that patients with low tumor burden are most likely to experience disease stabilization with octreotide LAR 30 mg, supporting the early use of octreotide LAR in patients with metastatic disease. Further research efforts are underway to evaluate the use of somatostatin analogs as antiproliferative agents in other types of gastroenteropancreatic-NETs. Ongoing studies are also evaluating novel somatostatin analogs and somatostatin analogs in combination with other anti-tumor therapies.
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273
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Arnaldi G, Boscaro M. Pasireotide for the treatment of Cushing's disease. Expert Opin Investig Drugs 2010; 19:889-98. [DOI: 10.1517/13543784.2010.495943] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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274
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Ovadia O, Greenberg S, Laufer B, Gilon C, Hoffman A, Kessler H. Improvement of drug-like properties of peptides: the somatostatin paradigm. Expert Opin Drug Discov 2010; 5:655-71. [DOI: 10.1517/17460441.2010.493935] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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275
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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276
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Durán-Prado M, Saveanu A, Luque RM, Gahete MD, Gracia-Navarro F, Jaquet P, Dufour H, Malagón MM, Culler MD, Barlier A, Castaño JP. A potential inhibitory role for the new truncated variant of somatostatin receptor 5, sst5TMD4, in pituitary adenomas poorly responsive to somatostatin analogs. J Clin Endocrinol Metab 2010; 95:2497-502. [PMID: 20233783 DOI: 10.1210/jc.2009-2247] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
CONTEXT Somatostatin (SST) receptors, specially sst2 and sst5, provide a valuable target to inhibit excessive hormone release and cell growth in pituitary tumors by using SST analogs (SSAs). Unfortunately, an appreciable proportion of tumors fail to respond to SSA despite expressing high levels of one or more ssts. Recently we identified two novel truncated sst5 variants, sst5TMD5, and sst5TMD4, absent in normal pituitary but expressed in pituitary tumors. OBJECTIVE AND DESIGN We aimed at exploring the potential role of sst5TMD5 and sst5TMD4 in the poor response of some tumors to SSA in vivo and in vitro. Specifically, 25 somatotropinomas showing different responses to octreotide in vivo and sst2 (BIM-23197)- and sst5(BIM-23268)-selective compounds in vitro were screened for sst5TMD5/sst5TMD4 expression by real-time PCR. Relationships between ssts expression and in vivo and in vitro secretory response of the corresponding pituitary samples were assessed. RESULTS sst5TMD5 was absent in all samples analyzed. sst5TMD4 was found in 85% of tumors, and its expression was positively correlated to that of sst5 (R(2) = 0.79, P < 0.001). Expression of sst5TMD4 was negatively correlated with the ability of octreotide to reduce GH levels in vivo and partially negatively correlated with inhibition of GH secretion by an sst5 selective agonist (BIM-23268) in vitro. CONCLUSIONS These results indicate that sst5TMD4 is related to the reduced ability of octreotide at normalizing hormone secretion in poorly responsive tumors in vivo. Further studies will help to evaluate the potential use of sst5TMD4 expression in surgically removed pituitary adenomas as a predictor of the subsequent response of different pituitary tumors to SSA therapy.
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Affiliation(s)
- Mario Durán-Prado
- Department of Cell Biology, Physiology, and Immunology, University of Córdoba, E-14014 Córdoba, Spain
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277
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Abstract
Targeted molecular imaging techniques have become indispensable tools in modern diagnostics because they provide accurate and specific diagnosis of disease information. Conventional nonspecific contrast agents suffer from low targeting efficiency; thus, the use of molecularly targeted imaging probes is needed depending on different imaging modalities. Although recent technologies have yielded various strategies for designing smart probes, utilization of peptide-based probes has been most successful. Phage display technology and combinatorial peptide chemistry have profoundly impacted the pool of available targeting peptides for the efficient and specific delivery of imaging labels. To date, selected peptides that target a variety of disease-related receptors and biomarkers are in place. These targeting peptides can be coupled with the appropriate imaging moieties or nanoplatforms on demand with the help of sophisticated bioconjugation or radiolabeling techniques. This review article examines the current trends in peptide-based imaging probes developed for in vivo applications. We discuss the advantage of and challenges in developing peptide-based probes and summarize current systems with respect to their unique design strategies and applications.
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Affiliation(s)
- Seulki Lee
- Laboratory for Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, 31 Center Drive, Suite 1C14, Bethesda, Maryland 20892-2281, USA
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278
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Gougeon A, Delangle A, Arouche N, Stridsberg M, Gotteland JP, Loumaye E. Kit ligand and the somatostatin receptor antagonist, BIM-23627, stimulate in vitro resting follicle growth in the neonatal mouse ovary. Endocrinology 2010; 151:1299-309. [PMID: 20056831 DOI: 10.1210/en.2009-0762] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In the mammalian ovary, kit ligand (KL), coded by a cAMP-stimulatable gene, is a protein that promotes initiation of follicle growth. The neuropeptide somatostatin (SST) is a small peptide that inhibits cAMP generation in many cell types. Consequently, SST receptor agonists might alter KL production and subsequent follicle growth. The present study was undertaken to look for the existence of a functional SST system in the mouse ovary, to test the effects of the SST receptor 2 (SSTR-2) antagonist BIM-23627 on in vitro folliculogenesis, and to compare them with those of KL, which was demonstrated to stimulate follicle growth in the neonatal rat ovary. Pairs of ovaries from 5-d-old mice were incubated in vitro during 15 d in the presence of either KL or BIM-23627. For every mouse, one ovary was cultured in culture medium (control), and the other ovary was cultured in the presence of either KL or BIM-23627. After 5, 10, and 15 d culture, the ovaries were histologically assessed for the content of primordial, primary, and secondary follicles. The SSTR-2 and -5, but not SST, were identified at the transcriptional and translational (mainly in granulosa cells) levels. Both KL and BIM-23627 triggered a reduction of the percentages of primordial follicles and an increase of the percentages of primary and secondary follicles when compared with control ovaries from the same animal. In conclusion, extraovarian SST, acting through its receptors 2 and 5 present on granulosa cells, may be involved in mouse folliculogenesis by reducing recruitment of resting follicles.
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Affiliation(s)
- Alain Gougeon
- Inserm U865, Faculté de médecine Laennec, 7 rue Guillaume Paradin, 69372 Lyon Cedex 08, France.
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279
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Zamora V, Cabanne A, Salanova R, Bestani C, Domenichini E, Marmissolle F, Giacomi N, O'Connor J, Méndez G, Roca E. Immunohistochemical expression of somatostatin receptors in digestive endocrine tumours. Dig Liver Dis 2010; 42:220-5. [PMID: 19819769 DOI: 10.1016/j.dld.2009.07.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 06/30/2009] [Accepted: 07/28/2009] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Somatostatin receptors are expressed in a large number of human tumours. The somatostatin receptors types 1-5 expression in a series including 100 gastro-entero-pancreatic endocrine tumours were analysed. METHODS From a prospectively built database of patients with gastro-entero-pancreatic endocrine tumours referred from three institutions, 100 cases with clinical and pathological data were selected. Somatostatin receptors expression by immunohistochemistry with somatostatin receptor types 1-5 antibodies in tissue paraffin sections were studied and correlated with the histological diagnosis according to the WHO classification, location and functional status. RESULTS Of the 100 cases, 67 were gastrointestinal tumours, 25 pancreatic and 8 liver metastasis of unknown origin. Thirty-one of them were functioning tumours: 2 insulinomas, 5 gastrinomas, 1 glucagonoma and 23 carcinoids. Somatostatin receptors expression was observed in 94 tumours. The six negative cases were all non-functioning tumours. Somatostatin receptors 2a and 5 were highly expressed (86 and 62%, respectively), and surprisingly found even in poorly differentiated endocrine carcinomas. Somatostatin receptors expression was less frequent in pancreatic than in gastrointestinal tumours. Well-differentiated neoplasms had a higher density of somatostatin receptors. Only SSTR2a showed membrane staining. CONCLUSIONS Immunohistochemistry revealed that somatostatin receptors were highly expressed in both primary and metastatic gastro-entero-pancreatic endocrine tumours with heterogeneous staining distribution. It proved to be a reliable technique even in small tumour samples.
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Affiliation(s)
- V Zamora
- Gastroenterology Hospital "C. Bonorino Udaondo", Buenos Aires, Argentina
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280
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Luo R, Guo Y, Cao DY, Pickar JG, Li L, Wang J, Zhao Y. Local effects of octreotide on glutamate-evoked activation of Aδ and C afferent fibers in rat hairy skin. Brain Res 2010; 1322:50-8. [DOI: 10.1016/j.brainres.2010.01.058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 01/19/2010] [Accepted: 01/22/2010] [Indexed: 10/19/2022]
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281
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Troxler T, Hurth K, Schuh KH, Schoeffter P, Langenegger D, Enz A, Hoyer D. Decahydroisoquinoline derivatives as novel non-peptidic, potent and subtype-selective somatostatin sst3 receptor antagonists. Bioorg Med Chem Lett 2010; 20:1728-34. [DOI: 10.1016/j.bmcl.2010.01.063] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/06/2010] [Accepted: 01/07/2010] [Indexed: 01/11/2023]
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282
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Ben-Shlomo A, Melmed S. Pituitary somatostatin receptor signaling. Trends Endocrinol Metab 2010; 21:123-33. [PMID: 20149677 PMCID: PMC2834886 DOI: 10.1016/j.tem.2009.12.003] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 12/27/2022]
Abstract
Somatotropin-release inhibitory factor (SRIF) is a major regulator of pituitary function, mostly inhibiting hormone secretion and to a lesser extent pituitary cell growth. Five SRIF receptor subtypes (SSTR1-5) are ubiquitously expressed G-protein coupled receptors. In the pituitary, SSTR1, 2, 3 and 5 are expressed, with SSTR2 and SSTR5 predominating. As new SRIF analogs have recently been introduced for treatment of pituitary disease, we evaluate the current knowledge of cell-specific pituitary SRIF receptor signaling and highlight areas of future research for comprehensive understanding of these mechanisms. Elucidating pituitary SRIF receptor signaling enables understanding of pituitary hormone secretion and cell growth, and also encourages future therapeutic development for pituitary disorders.
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Affiliation(s)
- Anat Ben-Shlomo
- Pituitary Center, Department of Medicine, Cedars Sinai Medical Center, Los Angeles, California 90048, USA
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283
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Hurevich M, Tal-Gan Y, Klein S, Barda Y, Levitzki A, Gilon C. Novel method for the synthesis of urea backbone cyclic peptides using new Alloc-protected glycine building units. J Pept Sci 2010; 16:178-85. [DOI: 10.1002/psc.1218] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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284
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Msaouel P, Galanis E, Koutsilieris M. Somatostatin and somatostatin receptors: implications for neoplastic growth and cancer biology. Expert Opin Investig Drugs 2010; 18:1297-316. [PMID: 19678799 DOI: 10.1517/13543780903176399] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Somatostatin agonists (SM-As) are capable of achieving durable symptomatic relief and significant clinical responses in certain tumours. Herein, we review the diverse direct and indirect mechanisms of antineoplastic activity elicited by SM-As as well as the hurdles that complicate their use as monotherapies in a broader range of malignancies. Emphasis is placed on recent clinical attempts to neutralise the IGF-mediated survival factor effects in the bone metastasis microenvironment in advanced prostate cancer. The first clinical trials of this 'anti-survival factor manipulation' strategy utilised the ability of SM-As to suppress the growth hormone-dependent liver-derived IGF-I bioavailability in combination with other drugs, such as dexamethasone, zolendronate and oestrogens, acting systemically and at the bone metastasis microenvironment. These regimens restored androgen ablation responsiveness in stage D3 prostate cancer patients and successfully produced objective clinical responses while only mild toxicities were observed. Furthermore, we focus on the preclinical experimental data of a targeted SM-A coupled to the super-potent doxorubicin derivative AN-201. The resulting conjugate (AN-238) has shown increased antitumour potency with a favourable toxicity profile. The potential use of novel SM-As as anticancer drugs is discussed in relation to data suggesting other direct and indirect treatment approaches pertaining to the somatostatin system.
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Affiliation(s)
- Pavlos Msaouel
- National & Kapodistrian University of Athens, Medical School, Department of Experimental Physiology, 75 Micras Asias St, Goudi-Athens 11527, Greece
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285
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Jin QJ, Sun JJ, Fang XT, Zhang CL, Yang L, Chen DX, Shi XY, Du Y, Lan XY, Chen H. Molecular characterization and polymorphisms of the caprine Somatostatin (SST) and SST Receptor 1 (SSTR1) genes that are linked with growth traits. Mol Biol Rep 2010; 38:3129-35. [DOI: 10.1007/s11033-010-9983-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2009] [Accepted: 01/20/2010] [Indexed: 12/18/2022]
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286
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Pöll F, Lehmann D, Illing S, Ginj M, Jacobs S, Lupp A, Stumm R, Schulz S. Pasireotide and octreotide stimulate distinct patterns of sst2A somatostatin receptor phosphorylation. Mol Endocrinol 2010; 24:436-46. [PMID: 20051480 DOI: 10.1210/me.2009-0315] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Pasireotide (SOM230) is currently under clinical evaluation as a successor compound to octreotide for the treatment of acromegaly, Cushing's disease, and carcinoid tumors. Whereas octreotide acts primarily via the sst(2A) somatostatin receptor, pasireotide was designed to exhibit octreotide-like sst(2A) activity combined with enhanced binding to other somatostatin receptor subtypes. In the present study, we used phophosite-specific antibodies to examine agonist-induced phosphorylation of the rat sst(2A) receptor. We show that somatostatin and octreotide stimulate the complete phosphorylation of a cluster of four threonine residues within the cytoplasmic (353)TTETQRT(359) motif in a variety of cultured cell lines in vitro as well as in intact animals in vivo. This phosphorylation was mediated by G protein-coupled receptor kinases (GRK) 2 and 3 and followed by rapid cointernalization of the receptor and ss-arrestin into the same endocytic vesicles. In contrast, pasireotide failed to promote substantial phosphorylation and internalization of the rat sst(2A) receptor. In the presence of octreotide or SS-14, SOM230 showed partial agonist behavior, inhibiting phosphorylation, and internalization of sst(2A). Upon overexpression of GRK2 or GRK3, pasireotide stimulated selective phosphorylation of Thr356 and Thr359 but not of Thr353 or Thr354 within the (353)TTETQRT(359) motif. Pasireotide-mediated phosphorylation led to the formation of relatively unstable beta-arrestin-sst(2A) complexes that dissociated at or near the plasma membrane. Thus, octreotide and pasireotide are equally active in inducing classical G protein-dependent signaling via the sst(2A) somatostatin receptor. Yet, we find that they promote strikingly different patterns of sst(2A) receptor phosphorylation and, hence, stimulate functionally distinct pools of beta-arrestin.
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Affiliation(s)
- Florian Pöll
- Department of Pharmacology and Toxicology, Friedrich-Schiller-University, Drackendorfer Strasse 1, D-07747 Jena, Germany
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287
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Martino MCD, Hofland LJ, Lamberts SW. Somatostatin and Somatostatin Receptors: from Basic Concepts to Clinical Applications. PROGRESS IN BRAIN RESEARCH 2010; 182:255-80. [DOI: 10.1016/s0079-6123(10)82011-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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288
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Grant M, Kumar U. The role of G-proteins in the dimerisation of human somatostatin receptor types 2 and 5. ACTA ACUST UNITED AC 2010; 159:3-8. [DOI: 10.1016/j.regpep.2009.08.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 07/13/2009] [Accepted: 08/16/2009] [Indexed: 01/15/2023]
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289
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Seebach D, Widmer H, Capone S, Ernst R, Bremi T, Kieltsch I, Togni A, Monna D, Langenegger D, Hoyer D. NMR-Solution Structures and Affinities for the Human Somatostatin G-Protein-Coupled Receptors hsst1â5 of CF3 Derivatives of Sandostatin® (Octreotide). Helv Chim Acta 2009. [DOI: 10.1002/hlca.200900279] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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290
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Ye DZ, Kaestner KH. Foxa1 and Foxa2 control the differentiation of goblet and enteroendocrine L- and D-cells in mice. Gastroenterology 2009; 137:2052-62. [PMID: 19737569 PMCID: PMC2789913 DOI: 10.1053/j.gastro.2009.08.059] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 08/04/2009] [Accepted: 08/21/2009] [Indexed: 01/08/2023]
Abstract
BACKGROUND & AIMS The winged helix transcription factors Foxa1 and Foxa2 are expressed in all epithelia of the gastrointestinal tract from its embryonic origin into adulthood. In vitro studies have shown that Foxa1/a2 can transactivate the promoters of Mucin 2 (Muc2), which is expressed in goblet cells, and of preproglucagon, which is expressed in enteroendocrine cells. These findings suggest Foxa1/a2 as critical factors in the differentiation of gut epithelial cells. METHODS Mice with intestine-specific simultaneous deletion of Foxa1 and Foxa2 were derived using the Cre-loxP system and analyzed using histologic and molecular means. RESULTS Both Foxa1 and Foxa2 were deleted successfully in the epithelia of the small intestine and colon using Villin-Cre mice. Immunohistochemical staining showed that Foxa1/a2 mutants lack glucagon-like peptide-1- and peptide-2-expressing cells (L-cells), and have reduced numbers of somatostatin (D-cells) and peptide YY-expressing cells (L-cells). Preproglucagon, somatostatin, and peptide YY messenger RNA (mRNA) levels also were reduced significantly in Foxa1/a2 mutants. Thus, Foxa1 and Foxa2 are essential regulators of these enteroendocrine lineages in vivo. The mRNA levels of transcription factors Islet-1 and Pax6 were reduced significantly in the small intestine, showing that Foxa1 and Foxa2 impact on a transcription factor network in the enteroendocrine lineage. In addition, deletion of Foxa1/a2 caused a reduction in goblet cell number with altered expression of the secretory mucins Muc2, Mucin5b, Mucin5ac, and Mucin 6. CONCLUSIONS The winged helix factors Foxa1 and Foxa2 are essential members of the transcription factor network that govern secretory cell differentiation in the mammalian gastrointestinal tract.
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Affiliation(s)
| | - Klaus H. Kaestner
- Corresponding author, , Klaus H. Kaestner, PhD, Department of Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA, Phone: 215-898-8759, Fax: 215-573-5892
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291
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Hernández B, Carelli C, Coïc YM, De Coninck J, Ghomi M. Vibrational analysis of amino acids and short peptides in aqueous media. V. The effect of the disulfide bridge on the structural features of the peptide hormone somatostatin-14. J Phys Chem B 2009; 113:12796-803. [PMID: 19708669 DOI: 10.1021/jp904737v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
To emphasize the role played by the S-S bridge in the structural features of somatostatin-14 (SST-14), newly recorded CD and Raman spectra of this cyclic peptide and its open analogue obtained by Cys-->Ser substitution are presented. CD spectra of both peptides recorded in aqueous solutions in the 100-500 microM concentration range are strikingly similar. They reveal principally that random conformers constitute the major population in both peptides. Consequently, the S-S bridge has no structuring effect at submillimolar concentrations. In methanol, the CD spectrum of somatostatin-14 keeps globally the same spectral shape as that observed in water, whereas its open analogue presents a major population of helical conformers. Raman spectra recorded as a function of peptide concentration (5-20 mM) and also in the presence of 150 mM NaCl provide valuable conformational information. All Raman spectra present a mixture of random and beta-hairpin structures for both cyclic and open peptides. More importantly, the presence or the absence of the disulfide bridge does not seem to influence considerably different populations of secondary structures within this range of concentrations. CD and Raman data obtained in the submillimolar and millimolar ranges of concentrations, respectively, lead us to accept the idea that SST-14 monomers aggregate upon increasing concentration, thus stabilizing beta-hairpin conformations in solution. However, even at high concentrations, random conformers do not disappear. Raman spectra of SST-14 also reveal a concentration effect on the flexibility of the S-S linkage and consequently on that of its cyclic part. In conclusion, although the disulfide linkage does not seem to markedly influence the SST-14 conformational features in aqueous solutions, its presence seems to be necessary to ensure the flexibility of the cyclic part of this peptide and to maintain its closed structure in lower dielectric constant environments.
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Affiliation(s)
- Belén Hernández
- Groupe de Biophysique Moléculaire (GBM), UFR SMBH, Université Paris 13, 74 rue Marcel Cachin, 93017 Bobigny Cedex, France
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292
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Mothes C, Larregola M, Quancard J, Goasdoué N, Lavielle S, Chassaing G, Lequin O, Karoyan P. Prolinoamino Acids as Tools to Build Bifunctionalized, Stable β-Turns in Water. Chembiochem 2009; 11:55-8. [DOI: 10.1002/cbic.200900572] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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293
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Abstract
Dysregulated growth hormone (GH) hypersecretion is usually caused by a GH-secreting pituitary adenoma and leads to acromegaly - a disorder of disproportionate skeletal, tissue, and organ growth. High GH and IGF1 levels lead to comorbidities including arthritis, facial changes, prognathism, and glucose intolerance. If the condition is untreated, enhanced mortality due to cardiovascular, cerebrovascular, and pulmonary dysfunction is associated with a 30% decrease in life span. This Review discusses acromegaly pathogenesis and management options. The latter include surgery, radiation, and use of novel medications. Somatostatin receptor (SSTR) ligands inhibit GH release, control tumor growth, and attenuate peripheral GH action, while GH receptor antagonists block GH action and effectively lower IGF1 levels. Novel peptides, including SSTR ligands, exhibiting polyreceptor subtype affinities and chimeric dopaminergic-somatostatinergic properties are currently in clinical trials. Effective control of GH and IGF1 hypersecretion and ablation or stabilization of the pituitary tumor mass lead to improved comorbidities and lowering of mortality rates for this hormonal disorder.
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Affiliation(s)
- Shlomo Melmed
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
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294
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Barbieri F, Pattarozzi A, Gatti M, Aiello C, Quintero A, Lunardi G, Bajetto A, Ferrari A, Culler MD, Florio T. Differential efficacy of SSTR1, -2, and -5 agonists in the inhibition of C6 glioma growth in nude mice. Am J Physiol Endocrinol Metab 2009; 297:E1078-88. [PMID: 19706788 DOI: 10.1152/ajpendo.00292.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Somatostatin receptors (SSTR1-5) mediate antiproliferative effects. In C6 rat glioma cells, somatostatin is cytostatic in vitro via phosphotyrosine phosphatase-dependent inhibition of ERK1/2 activity mediated by SSTR1, -2, and -5. Here we analyzed the effects of SSTR activation on C6 glioma growth in vivo and the intracellular mechanisms involved, comparing somatostatin effects with selective agonists for SSTR1, -2, and -5 (BIM-23745, BIM-23120, BIM-23206) or receptor biselective compounds (SSTR1 and -2, BIM-23704; and SSTR2 and -5, BIM-23190). Nude mice subcutaneously xenografted with C6 cells were treated with somatostatin, SSTR agonists (50 μg, twice/day), or vehicle. Tumor growth was evaluated every 3 days for 19 days. The intracellular pathways responsible of SSTR effects in vivo were evaluated measuring Ki-67, phospho-ERK1/2, and p27(kip1) expression by immunohistochemistry in sections from explanted tumors. Somatostatin and SSTR1, -2, and -5 agonists strongly inhibited in vivo C6 tumor growth, intratumoral neovessel formation, Ki-67 expression, and ERK1/2 phosphorylation and induced upregulation of p27(Kip1), whereas only a modest activation of caspase-3 was observed. Somatostatin (acting on SSTR1, -2, and -5) displayed the highest efficacy; SSTR5 selective agonist showed a stronger effect than SSTR1 agonist, and SSTR2 agonist was less effective. On the other hand, SSTR1 and -2 agonists maximally reduced tumor neovascularization. The combined activation of SSTR1 and -2 showed a synergistic activity, reaching a higher efficacy than BIM-23206, whereas the simultaneous activation of SSTR2 and -5 resulted in a response resembling SSTR5 effects. Thus the simultaneous activation of different SSTRs inhibits glioma cell proliferation in vivo through both direct cytotostatic and antiangiogenic effects.
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Affiliation(s)
- Federica Barbieri
- Laboratory of Pharmacology, Dept. of Oncology, Biology, and Genetics, Univ. of Genoa, Viale Benedetto XV, 2, 16132 Genoa, Italy
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295
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Engin E, Treit D. Anxiolytic and antidepressant actions of somatostatin: the role of sst2 and sst3 receptors. Psychopharmacology (Berl) 2009; 206:281-9. [PMID: 19609508 DOI: 10.1007/s00213-009-1605-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 06/26/2009] [Indexed: 12/21/2022]
Abstract
RATIONALE AND OBJECTIVES Somatostatin is a cyclic polypeptide that inhibits the release of a variety of regulatory hormones (e.g., growth hormone, insulin, glucagon, and thyrotropin). Somatostatin is also widely distributed within the central nervous system (CNS), acting both as a neurotransmitter and as a neuromodulator. Recently, we showed that intracerebroventricular (i.c.v.) administration of somatostatin reduced anxiety-like and depression-like behaviors in animal models. The somatostatin receptor subtypes that are involved in these behavioral effects, however, have not been investigated. In the CNS, the neurotransmitter actions of somatostatin are mediated through five G-protein coupled receptors (sst1 to sst5). MATERIALS AND METHODS We examined the behavioral effects of i.c.v. microinfusions of different doses of selective agonists of each of the five somatostatin receptor subtypes. Their behavioral effects were assessed in the elevated plus-maze and the forced swim apparatus, rodent models of anxiolytic and antidepressant drug effects, respectively. RESULTS Anxiety-like behavior was reduced following i.c.v. infusions of a selective sst2 receptor agonist, but not after infusions of the other four receptor agonists. An antidepressant-like effect was observed following infusions of either sst2 or sst3 agonists. CONCLUSIONS The results add to our nascent understanding of the role of somatostatin in anxiety- and depression-like behavior and suggest a clinical role for somatostatin agonists for the simultaneous treatment of anxiety and depression, which are often comorbid.
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Affiliation(s)
- Elif Engin
- Department of Psychology, Centre for Neuroscience, University of Alberta, Edmonton, T6G 2E9, AB, Canada
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296
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Thrombospondin-1 is a critical effector of oncosuppressive activity of sst2 somatostatin receptor on pancreatic cancer. Proc Natl Acad Sci U S A 2009; 106:17769-74. [PMID: 19805200 DOI: 10.1073/pnas.0908674106] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The somatostatin receptor subtype 2 (sst2) behaves as a tumor suppressor when expressed and stimulated by its ligand somatostatin in pancreatic cancer. We reveal a mechanism underlying oncosuppressive action of sst2, whereby this inhibitory receptor upregulates the expression of the secreted angioinhibitory factor thrombospondin-1 (TSP-1), as demonstrated in exocrine BxPC-3 and endocrine BON pancreatic cancer cells. The sst2-dependent upregulation of TSP-1 occurs through the inhibition of the PI3K pathway. It depends on transcriptional and translational events, involving a previously undescribed IRES in the 5'-UTR of TSP-1 mRNA. Chick chorioallantoic membrane was used as an in vivo model to demonstrate that TSP-1 is a critical effector of the inhibitory role of sst2 on the neoangiogenesis and oncogenesis induced by pancreatic cancer cells. TSP-1 reduced in vitro tubulogenesis of endothelial cells when grown in conditioned medium from pancreatic cancer cells expressing sst2, as compared to those expressing the control vector. TSP-1 inhibited tumor cell-induced neoangiogenesis by directly sequestering the proangiogenic factor VEGF, and inactivating the angiogenesis initiated by VEGFR2 phosphorylation in endothelial cells. Using human pancreatic tissue-microarrays, the expression of both sst2 and TSP-1 was shown to be correlated during the pancreatic neoplastic program. Both proteins are nearly undetectable in normal exocrine pancreas and in most invasive cancer lesions, but their expression is strikingly upregulated in most preinvasive cancer-adjacent lesions. The upregulation of both sst2 and TSP-1 tumor suppressors may function as an early negative feedback to restrain pancreatic carcinogenesis.
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297
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Synthesis of chemically modified bioactive peptides: recent advances, challenges and developments for medicinal chemistry. Future Med Chem 2009; 1:1289-310. [DOI: 10.4155/fmc.09.97] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Although not complying with Lipinski’s rule, peptides are to an increasing extent being developed into new active pharmaceutical ingredients. This is mainly due to novel application routes, formulations and chemical modifications, which confer on the peptides improved uptake and increased metabolic stability. A brief survey of currently approved peptide drugs and the present scope of the application of peptides as drugs is provided. Cyclic peptides are emerging as an interesting class of peptides with conformational rigidity and homogeneity, high receptor affinity and selectivity, increased metabolic stability and – in special cases – even oral availability. Challenges and new methodology for the synthesis of cyclic peptides are outlined and an overview of approaches toward the design of peptide conformation and peptide modification by nonproteinogenic building blocks is given.
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298
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Theodoropoulou M, Tichomirowa MA, Sievers C, Yassouridis A, Arzberger T, Hougrand O, Deprez M, Daly AF, Petrossians P, Pagotto U, Beckers A, Stalla GK. Tumor ZAC1 expression is associated with the response to somatostatin analog therapy in patients with acromegaly. Int J Cancer 2009; 125:2122-6. [PMID: 19637311 DOI: 10.1002/ijc.24602] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Somatostatin analogs (SSA) with their potent antisecretory and antiproliferative effects are the main medical treatment option for patients with neuroendocrine tumors, such as gastroenteropancreatic and acromegaly-associated growth hormone secreting pituitary tumors. Although a good portion of acromegalic patients gets normalized after SSA treatment, strict hormonal control is not achieved in a sizeable proportion of these patients. The reasons for this incomplete response to SSA treatment are unclear. We have found that the tumor suppressor ZAC1 (LOT1/PLAGL1) is essential for the antiproliferative effect of SSA in pituitary tumor cells. The aim of the present retrospective cohort study was to determine whether ZAC1 immunoreactivity in archival somatotrophinoma tissue derived from 45 patients with acromegaly routinely pretreated with SSA before surgery, was associated with response to SSA (normalization of GH, IGF-I and presence of tumor shrinkage). All tumors displayed ZAC1 immunoreactivity [weak (+; n = 15), moderate (++; n = 16) and strong (+++; n = 14)]. A significant positive correlation was found between strong ZAC1 immunoreactivity and IGF-I normalization and presence of tumor shrinkage after SSA treatment, which was not affected by age at diagnosis, gender or duration of SSA treatment. These in vivo data combined with the antiproliferative properties of ZAC1/Zac1 provide evidence of a mechanistic role for this transcription factor on SSA induced tumor shrinkage and hormone normalization.
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Affiliation(s)
- Marily Theodoropoulou
- Department of Endocrinology, Max Planck Institute of Psychiatry, 80804 Munich, Germany.
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299
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Varecza Z, Elekes K, László T, Perkecz A, Pintér E, Sándor Z, Szolcsányi J, Keszthelyi D, Szabó A, Sándor K, Molnár TF, Szántó Z, Pongrácz JE, Helyes Z. Expression of the somatostatin receptor subtype 4 in intact and inflamed pulmonary tissues. J Histochem Cytochem 2009; 57:1127-37. [PMID: 19687471 DOI: 10.1369/jhc.2009.953919] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Somatostatin released from capsaicin-sensitive sensory nerves of the lung during endotoxin-induced murine pneumonitis inhibits inflammation and hyperresponsiveness, presumably via somatostatin receptor subtype 4 (sst(4)). The goal of the present study was to identify sst(4) receptors in mouse and human lungs and to reveal its inflammation-induced alterations with real-time quantitative PCR, Western blot, and immunohistochemistry. In non-inflamed mouse and human lungs, mRNA expression and immunolocalization of sst(4) are very similar. They are present on bronchial epithelial, vascular endothelial, and smooth-muscle cells. The sst(4) receptor protein in the mouse lung significantly increases 24 hr after intranasal endotoxin administration as well as in response to 3 months of whole-body cigarette smoke exposure, owing to the infiltrating sst(4)-positive mononuclear cells and neutrophils. In the chronically inflamed human lung, the large number of activated macrophages markedly elevate sst(4) mRNA levels, although there is no change in acute purulent pneumonia, in which granulocytes accumulate. Despite mouse granulocytes, human neutrophils do not show sst(4) immunopositivity. We provide the first evidence for the expression, localization, and inflammation-induced alterations of sst(4) receptors in murine and human lungs. Inasmuch as tissue distribution of this receptor is highly similar, extrapolation of murine experimental results to human conditions might be possible.
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Affiliation(s)
- Zoltán Varecza
- Department of Immunology and Biotechnology, University of Pécs, Pécs, Hungary
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300
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Jian K, Barhoumi R, Ko ML, Ko GYP. Inhibitory effect of somatostatin-14 on L-type voltage-gated calcium channels in cultured cone photoreceptors requires intracellular calcium. J Neurophysiol 2009; 102:1801-10. [PMID: 19605612 DOI: 10.1152/jn.00354.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The inhibitory effects of somatostatin have been well documented for many physiological processes. The action of somatostatin is through G-protein-coupled receptor-mediated second-messenger signaling, which in turn affects other downstream targets including ion channels. In the retina, somatostatin is released from a specific class of amacrine cells. Here we report that there was a circadian phase-dependent effect of somatostatin-14 (SS14) on the L-type voltage-gated calcium channels (L-VGCCs) in cultured chicken cone photoreceptors, and our study reveals that this process is dependent on intracellular calcium stores. Application of 500 nM SS14 for 2 h caused a decrease in L-VGCC currents only during the subjective night but not the subjective day. We then explored the cellular mechanisms underlying the circadian phase-dependent effect of SS14. The inhibitory effect of SS14 on L-VGCCs was mediated through the pertussis-toxin-sensitive G-protein-dependent somatostatin receptor 2 (sst2). Activation of sst2 by SS14 further activated downstream signaling involving phospholipase C and intracellular calcium stores. Mobilization of intracellular Ca2+ was required for somatostatin induced inhibition of photoreceptor L-VGCCs, suggesting that somatostatin plays an important role in the modulation of photoreceptor physiology.
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Affiliation(s)
- Kuihuan Jian
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4458 TAMU, College Station, TX 77843-4458, USA
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