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Milewska-Kranc A, Ćwikła JB, Kolasinska-Ćwikła A. The Role of Receptor-Ligand Interaction in Somatostatin Signaling Pathways: Implications for Neuroendocrine Tumors. Cancers (Basel) 2023; 16:116. [PMID: 38201544 PMCID: PMC10778465 DOI: 10.3390/cancers16010116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024] Open
Abstract
Neuroendocrine tumors (NETs) arise from neuroendocrine cells and manifest in diverse organs. Key players in their regulation are somatostatin and its receptors (SSTR1-SSTR5). Understanding receptor-ligand interactions and signaling pathways is vital for elucidating their role in tumor development and therapeutic potential. This review highlights SSTR characteristics, localization, and expression in tissues, impacting physiological functions. Mechanisms of somatostatin and synthetic analogue binding to SSTRs, their selectivity, and their affinity were analyzed. Upon activation, somatostatin initiates intricate intracellular signaling, involving cAMP, PLC, and MAP kinases and influencing growth, differentiation, survival, and hormone secretion in NETs. This review explores SSTR expression in different tumor types, examining receptor activation effects on cancer cells. SSTRs' significance as therapeutic targets is discussed. Additionally, somatostatin and analogues' role in hormone secretion regulation, tumor growth, and survival is emphasized, presenting relevant therapeutic examples. In conclusion, this review advances the knowledge of receptor-ligand interactions and signaling pathways in somatostatin receptors, with potential for improved neuroendocrine tumor treatments.
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Affiliation(s)
| | - Jarosław B. Ćwikła
- School of Medicine, University of Warmia and Mazury, Aleja Warszawska 30, 10-082 Olsztyn, Poland
- Diagnostic Therapeutic Center–Gammed, Lelechowska 5, 02-351 Warsaw, Poland
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Costanzi E, Simioni C, Conti I, Laface I, Varano G, Brenna C, Neri LM. Two neuroendocrine G protein-coupled receptor molecules, somatostatin and melatonin: Physiology of signal transduction and therapeutic perspectives. J Cell Physiol 2020; 236:2505-2518. [PMID: 32989768 DOI: 10.1002/jcp.30062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/04/2020] [Accepted: 09/10/2020] [Indexed: 12/15/2022]
Abstract
Recent studies have shown that G protein-coupled receptors (GPCRs), the largest signal-conveying receptor family, are targets for mutations occurring frequently in different cancer types. GPCR alterations associated with cancer development represent significant challenges for the discovery and the advancement of targeted therapeutics. Among the different molecules that can activate GPCRs, we focused on two molecules that exert their biological actions regulating many typical features of tumorigenesis such as cellular proliferation, survival, and invasion: somatostatin and melatonin. The modulation of signaling pathways, that involves these two molecules, opens an interesting scenario for cancer therapy, with the opportunity to act at different molecular levels. Therefore, the aim of this review is the analysis of the biological activity and the therapeutic potential of somatostatin and melatonin, displaying a high affinity for GPCRs, that interfere with cancer development and maintenance.
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Affiliation(s)
- Eva Costanzi
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Carolina Simioni
- Department of Medical Sciences, University of Ferrara, Ferrara, Italy.,Laboratory for Technologies of Advanced Therapies (LTTA)-Electron Microscopy Center, University of Ferrara, Ferrara, Italy
| | - Ilaria Conti
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Ilaria Laface
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Gabriele Varano
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Cinzia Brenna
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Luca M Neri
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy.,Laboratory for Technologies of Advanced Therapies (LTTA)-Electron Microscopy Center, University of Ferrara, Ferrara, Italy
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Biological and Biochemical Basis of the Differential Efficacy of First and Second Generation Somatostatin Receptor Ligands in Neuroendocrine Neoplasms. Int J Mol Sci 2019; 20:ijms20163940. [PMID: 31412614 PMCID: PMC6720449 DOI: 10.3390/ijms20163940] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/1970] [Revised: 08/05/2019] [Accepted: 08/08/2019] [Indexed: 02/07/2023] Open
Abstract
Endogenous somatostatin shows anti-secretory effects in both physiological and pathological settings, as well as inhibitory activity on cell growth. Since somatostatin is not suitable for clinical practice, researchers developed synthetic somatostatin receptor ligands (SRLs) to overcome this limitation. Currently, SRLs represent pivotal tools in the treatment algorithm of neuroendocrine tumors (NETs). Octreotide and lanreotide are the first-generation SRLs developed and show a preferential binding affinity to somatostatin receptor (SST) subtype 2, while pasireotide, which is a second-generation SRL, has high affinity for multiple SSTs (SST5 > SST2 > SST3 > SST1). A number of studies demonstrated that first-generation and second-generation SRLs show distinct functional properties, besides the mere receptor affinity. Therefore, the aim of the present review is to critically review the current evidence on the biological effects of SRLs in pituitary adenomas and neuroendocrine tumors, by mainly focusing on the differences between first-generation and second-generation ligands.
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Klironomos S, Notas G, Sfakianaki O, Kiagiadaki F, Xidakis C, Kouroumalis E. Octreotide modulates the effects on fibrosis of TNF-α, TGF-β and PDGF in activated rat hepatic stellate cells. ACTA ACUST UNITED AC 2013; 188:5-12. [PMID: 24291170 DOI: 10.1016/j.regpep.2013.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 11/12/2013] [Accepted: 11/19/2013] [Indexed: 12/11/2022]
Abstract
BACKGROUND AND AIMS Somatostatin and its analogs may influence hepatic fibrosis interfering through several mechanisms. The aim of this study was to investigate the effect of octreotide on cytokine activated hepatic stellate cells (HSC). METHODS Primary HSCs were isolated from rats and were cultured on plastic for activation. Expression of somatostatin receptors (SSTR) was investigated in cultured HSCs by immunofluorescence and western blot. The effect of octreotide on cellular proliferation was studied with the MTT assay and western blot for α1-procollagen (α1-PROC) production in TNFα, TGF-β1 or PDGF treated HSCs. Phosphotyrosine (PTP) and phosphoserine-phosphothreonine (STP) phosphatases inhibition was performed with sodium orthovanadate and okadaic acid respectively. RESULTS Activated HSC express SSTR subtypes 1, 2A, 2B, 3 and 4 and their expression is enhanced by further HSC activation. Octreotide did not have an effect on HSC proliferation but inhibited plastic induced α1-PROC production. Interestingly, it enhanced PDGF-induced HSC proliferation but inhibited PDGF and TGFβ1 dependent expression of α1-PROC, while an opposite effect was observed in TNFα-induced cell proliferation and collagen production. PTP inhibition reversed the inhibitory effect of octreotide on α1-PROC, but potentiated its effect on PDGF and TGFβ1 dependent α1-PROC production. Finally, STP inhibition profoundly inhibited α1-PROC expression in all cases suggesting that both STP and PTP phosphatases are important regulators of pro-fibrotic mechanisms. CONCLUSIONS The net effect of octreotide on HSCs and therefore liver fibrosis is subject to the cytokine microenvironment of these cells. This effect is modulated by PTPs and STPs inhibition. Especially in the case of STPs their profibrotic effects could be an interesting new therapeutic target in liver fibrosis.
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Affiliation(s)
- Stefanos Klironomos
- Liver Research Laboratory, Medical School, University of Crete, Voutes 71003 Crete, Greece
| | - George Notas
- Liver Research Laboratory, Medical School, University of Crete, Voutes 71003 Crete, Greece; Laboratory of Experimental Endocrinology, Medical School, University of Crete, Voutes 71003 Crete, Greece
| | - Ourania Sfakianaki
- Liver Research Laboratory, Medical School, University of Crete, Voutes 71003 Crete, Greece
| | - Foteini Kiagiadaki
- Laboratory of Experimental Endocrinology, Medical School, University of Crete, Voutes 71003 Crete, Greece
| | - Costas Xidakis
- Liver Research Laboratory, Medical School, University of Crete, Voutes 71003 Crete, Greece
| | - Elias Kouroumalis
- Liver Research Laboratory, Medical School, University of Crete, Voutes 71003 Crete, Greece.
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Theodoropoulou M, Stalla GK. Somatostatin receptors: from signaling to clinical practice. Front Neuroendocrinol 2013; 34:228-52. [PMID: 23872332 DOI: 10.1016/j.yfrne.2013.07.005] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 06/13/2013] [Accepted: 07/12/2013] [Indexed: 02/08/2023]
Abstract
Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.
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Affiliation(s)
- Marily Theodoropoulou
- Department of Endocrinology, Max Planck Institute of Psychiatry, Kraepelinstrasse 10, 80804 Munich, Germany.
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Peptide receptor targeting in cancer: the somatostatin paradigm. INTERNATIONAL JOURNAL OF PEPTIDES 2013; 2013:926295. [PMID: 23476673 PMCID: PMC3582104 DOI: 10.1155/2013/926295] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 12/10/2012] [Accepted: 12/28/2012] [Indexed: 02/06/2023]
Abstract
Peptide receptors involved in pathophysiological processes represent promising therapeutic targets. Neuropeptide somatostatin (SST) is produced by specialized cells in a large number of human organs and tissues. SST primarily acts as inhibitor of endocrine and exocrine secretion via the activation of five G-protein-coupled receptors, named sst1–5, while in central nervous system, SST acts as a neurotransmitter/neuromodulator, regulating locomotory and cognitive functions. Critical points of SST/SST receptor biology, such as signaling pathways of individual receptor subtypes, homo- and heterodimerization, trafficking, and cross-talk with growth factor receptors, have been extensively studied, although functions associated with several pathological conditions, including cancer, are still not completely unraveled. Importantly, SST exerts antiproliferative and antiangiogenic effects on cancer cells in vitro, and on experimental tumors in vivo. Moreover, SST agonists are clinically effective as antitumor agents for pituitary adenomas and gastro-pancreatic neuroendocrine tumors. However, SST receptors being expressed by tumor cells of various tumor histotypes, their pharmacological use is potentially extendible to other cancer types, although to date no significant results have been obtained. In this paper the most recent findings on the expression and functional roles of SST and SST receptors in tumor cells are discussed.
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Somnay Y, Chen H, Kunnimalaiyaan M. Synergistic effect of pasireotide and teriflunomide in carcinoids in vitro. Neuroendocrinology 2013; 97:183-92. [PMID: 22965070 PMCID: PMC3546174 DOI: 10.1159/000341810] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 07/09/2012] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIM Somatostatin (SST) analogs are mainstay for controlling tumor proliferation and hormone secretion in carcinoid patients. Recent data suggest that extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation may potentiate the anti-tumor effects of SST analogs in carcinoids. Additionally, ERK1/2 phosphorylating agents have been shown to suppress biomarker expression in carcinoids. Thus, Raf-1/MEK/ERK1/2 pathway activating drugs may be synergistic with SST analogs such as pasireotide (SOM230), which may be more effective than others in its class given its elevated receptor affinity and broader binding spectrum. Here, we investigate the effects of SOM230 in combination with teriflunomide (TFN), a Raf-1 activator, in a human carcinoid cell line. METHODS Human pancreatic carcinoid cells (BON) were incubated in TFN, SOM230 or a combination. Cell proliferation was measured using a rapid colorimetric assay. Western analysis was performed to analyze expression levels of achaete-scute complex-like 1 (ASCL1), chromogranin A (CgA), phosphorylated and total ERK1/2, and markers for apoptosis. RESULTS Combination treatment with SOM230 and TFN reduced cell growth beyond the additive effect of either drug alone. Combination indices (CI) fell below 1, thus quantifiably verifying synergy between both drugs as per the Chou-Talalay CI scale. Combined treatment also reduced ASCL1 and CgA expression beyond the additive effect of either drug alone. Furthermore, it increased levels of phosphorylated ERK1/2, cleaved poly(ADP)-ribose polymerase and caspase-3, and reduced levels of anti-apoptotic biomarkers. Elevated phosphorylated ERK1/2 expression following combination therapy may underlie the synergistic interaction between the two drugs. CONCLUSION Since efficacy is achieved at lower doses, combination therapy may palliate symptoms at low toxicity levels. Because each drug has already been evaluated in clinical trials, combinatorial drug trials are warranted.
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Affiliation(s)
- Yash Somnay
- University of Wisconsin School of Medicine and Public Health, Endocrine Surgery Research Laboratories, Department of Surgery, Madison, USA
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Fang WB, Jokar I, Zou A, Lambert D, Dendukuri P, Cheng N. CCL2/CCR2 chemokine signaling coordinates survival and motility of breast cancer cells through Smad3 protein- and p42/44 mitogen-activated protein kinase (MAPK)-dependent mechanisms. J Biol Chem 2012; 287:36593-608. [PMID: 22927430 PMCID: PMC3476325 DOI: 10.1074/jbc.m112.365999] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 07/30/2012] [Indexed: 12/24/2022] Open
Abstract
Increased cell motility and survival are important hallmarks of metastatic tumor cells. However, the mechanisms that regulate the interplay between these cellular processes remain poorly understood. In these studies, we demonstrate that CCL2, a chemokine well known for regulating immune cell migration, plays an important role in signaling to breast cancer cells. We report that in a panel of mouse and human breast cancer cell lines CCL2 enhanced cell migration and survival associated with increased phosphorylation of Smad3 and p42/44MAPK proteins. The G protein-coupled receptor CCR2 was found to be elevated in breast cancers, correlating with CCL2 expression. RNA interference of CCR2 expression in breast cancer cells significantly inhibited CCL2-induced migration, survival, and phosphorylation of Smad3 and p42/44MAPK proteins. Disruption of Smad3 expression in mammary carcinoma cells blocked CCL2-induced cell survival and migration and partially reduced p42/44MAPK phosphorylation. Ablation of MAPK phosphorylation in Smad3-deficient cells with the MEK inhibitor U0126 further reduced cell survival but not migration. These data indicate that Smad3 signaling through MEK-p42/44MAPK regulates CCL2-induced cell motility and survival, whereas CCL2 induction of MEK-p42/44MAPK signaling independent of Smad3 functions as an alternative mechanism for cell survival. Furthermore, we show that CCL2-induced Smad3 signaling through MEK-p42/44MAPK regulates expression and activity of Rho GTPase to mediate CCL2-induced breast cancer cell motility and survival. With these studies, we characterize an important role for CCL2/CCR2 chemokine signaling in regulating the intrinsic relationships between breast cancer cell motility and survival with implications on the metastatic process.
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Affiliation(s)
- Wei Bin Fang
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
| | - Iman Jokar
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
| | - An Zou
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
| | - Diana Lambert
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
| | - Prasanthi Dendukuri
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
| | - Nikki Cheng
- From the Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160
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Kumar U. Cross-talk and modulation of signaling between somatostatin and growth factor receptors. Endocrine 2011; 40:168-80. [PMID: 21870170 DOI: 10.1007/s12020-011-9524-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 08/11/2011] [Indexed: 12/19/2022]
Abstract
The process of homo- and/or heterodimerization of G-protein coupled receptors (GPCRs) and receptor tyrosine kinase (RTK) families are crucial for implicating the fundamental properties of receptor proteins including receptor expression, trafficking, and desensitization as well as signal transduction. The members of GPCR and RTK family constitute largest cell surface receptor proteins and regulate physiological functions of cells in response to external and internal stimuli. Notably, GPCRs and RTKs play major role in regulation of several key cellular functions which are associated with several pathological conditions including cancer biology, neurodegenerative and cardiovascular diseases. The focus of this review is to highlight the recent findings on the possible cross-talk between somatostatin receptors (members of GPCR family) and growth factor receptors like epidermal growth factor receptors (members of RTK family). Furthermore, functional consequences of such an interaction in modulation of signaling pathways linked to pathological conditions specifically in cancer are discussed.
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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Hasskarl J, Kaufmann M, Schmid HA. Somatostatin receptors in non-neuroendocrine malignancies: the potential role of somatostatin analogs in solid tumors. Future Oncol 2011; 7:895-913. [PMID: 21732759 DOI: 10.2217/fon.11.66] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
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 sstr2-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 sstr1–3 and sstr5. 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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Affiliation(s)
| | - Martina Kaufmann
- Novartis Pharma AG, Forum 1, Novartis Campus, CH-4056 Basel, Switzerland
| | - Herbert A Schmid
- Novartis Pharma AG, Forum 1, Novartis Campus, CH-4056 Basel, Switzerland
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Cakir M, Dworakowska D, Grossman A. Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 1--molecular pathways. J Cell Mol Med 2011; 14:2570-84. [PMID: 20629989 PMCID: PMC4373477 DOI: 10.1111/j.1582-4934.2010.01125.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Neuroendocrine tumours (NETs) may occur at many sites in the body although the majority occur within the gastroenteropancreatic axis. Non-gastroenteropancreatic NETs encompass phaeochromocytomas and paragangliomas, medullary thyroid carcinoma, anterior pituitary tumour, broncho-pulmonary NETs and parathyroid tumours. Like most endocrine tumours, NETs also express somatostatin (SST) receptors (subtypes 1–5) whose ligand SST is known to inhibit endocrine and exocrine secretions and have anti-tumour effects. In the light of this knowledge, the idea of using SST analogues in the treatment of NETs has become increasingly popular and new studies have centred upon the development of new SST analogues. We attempt to review SST receptor (SSTR) biology primarily in neuroendocrine tissues, focusing on pituitary tumours. A full data search was performed through PubMed over the years 2000–2009 with keywords ‘somatostatin, molecular biology, somatostatin receptors, somatostatin signalling, NET, pituitary’ and all relevant publications have been included, together with selected publications prior to that date. SSTR signalling in non-neuroendocrine solid tumours is beyond the scope of this review. SST is a potent anti-proliferative and anti-secretory agent for some NETs. The successful therapeutic use of SST analogues in the treatment of these tumours depends on a thorough understanding of the diverse effects of SSTR subtypes in different tissues and cell types. Further studies will focus on critical points of SSTR biology such as homo- and heterodimerization of SSTRs and the differences between post-receptor signalling pathways of SSTR subtypes.
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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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Kharmate G, Rajput PS, Watt HL, Somvanshi RK, Chaudhari N, Qiu X, Kumar U. Role of somatostatin receptor 1 and 5 on epidermal growth factor receptor mediated signaling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1172-89. [DOI: 10.1016/j.bbamcr.2011.03.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 02/28/2011] [Accepted: 03/09/2011] [Indexed: 12/19/2022]
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Kharmate G, Rajput PS, Watt HL, Somvanshi RK, Chaudhari N, Qiu X, Kumar U. Dissociation of epidermal growth factor receptor and ErbB2 heterodimers in the presence of somatostatin receptor 5 modulate signaling pathways. Endocrinology 2011; 152:931-45. [PMID: 21190959 DOI: 10.1210/en.2010-0940] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Epidermal growth factor through the stimulation of epidermal growth factor receptor (EGFR) plays a critical role in the activation of MAPKs and phosphatidylinositol-3-protein kinase/AKT cell survival pathways attributed in many pathological conditions. At the cellular level, such functions involve EGFR overactivation and phosphorylation. In the present study, we describe that human embryonic kidney-293 cells transfected with somatostatin (SST) receptor 5 (SSTR5) exhibit inhibition of EGFR phosphorylation and modulate MAPK and phosphatidylinositol-3-protein kinase/AKT cell survival signaling. Furthermore, suppression of EGFR by using small interference RNA and an antagonist (AG1478) potentiates the SST effect via activation of SSTR5 on signaling molecules. In wild-type human embryonic kidney-293 cells, EGFR/ErbB2 exists as constitutive heterodimers. The presence of SSTR5 leads to the dissociation of the heteromeric complex of EGFR/ErbB2 and display preferential heterodimerization between SSTR5 and EGFR in an agonist-dependent manner. These findings highlight a new undiscovered mechanism and potential role of SSTR5 to attenuate the EGFR-mediated signaling pathways involved in tumorigenesis. Our data indicate that the activation and/or overexpression of SST receptors along with the inhibition of EGFR will serve as an important therapeutic approach in the treatment of ErbB-positive tumors.
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Affiliation(s)
- Geetanjali Kharmate
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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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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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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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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17
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Liu CH, Wu KW. Synergistic effects of basic fibroblast growth factor and insulin on Chinese hamster ovary cells under serum-free conditions. J Biosci Bioeng 2009; 107:312-7. [DOI: 10.1016/j.jbiosc.2009.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 11/06/2009] [Indexed: 11/25/2022]
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18
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Somatostatin receptors 1 and 5 heterodimerize with epidermal growth factor receptor: agonist-dependent modulation of the downstream MAPK signalling pathway in breast cancer cells. Cell Signal 2008; 21:428-39. [PMID: 19070659 DOI: 10.1016/j.cellsig.2008.11.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 11/13/2008] [Accepted: 11/15/2008] [Indexed: 12/22/2022]
Abstract
The role of somatostatin (SST) and epidermal growth factor (EGF) in breast cancer is undisputed; however, the molecular mechanisms underlying their antiproliferative or proliferative effects are not well understood. We initially confirmed that breast tumour tissues express all five somatostatin receptors (SSTR1-5) and four epidermal growth factor receptors (ErbB1-4). Subsequently, to gain insight into the function of SSTRs and ErbBs in oestrogen receptor (ER)-positive (MCF-7) or ERalpha-negative (MDA-MB-231) breast cancer cells, we defined SSTR1, SSTR5 and ErbB1 mRNA and protein expression in these two tumour cell lines. Consistent with previous studies showing SSTR1/SSTR5 heterodimerization and having seen cell-specific and ligand-selective alterations in receptor expression, we next elucidated whether SSTR1 and SSTR5 functionally interact with ErbB1 using pbFRET analysis. We subsequently determined the effects of SST and EGF either alone, or in combination, on selected downstream signalling molecules such as erk1/2, p38 and JNK. Here, we showed that both SST and EGF influenced erk1/2 phosphorylation and that SST modulated the effects of EGF in a cell-specific manner. We also demonstrated agonist-, time and cell-dependent regulation of p38 phosphorylation. We further investigated modulation of Grb2, SOS, Shc, SH-PTP1 and SH-PTP2. ErbB1 adaptor proteins known to play a role in MAPK activation, Shc, Grb2 and SOS, changed in an agonist- and cell-specific manner whereas, SH-PTP1 and SH-PTP2, adaptor proteins reported to interact with SSTRs, translocated from the cytosol to membrane in a cell-specific manner following SST and/or EGF treatment. Although several previous studies have shown crosstalk between RTKs and GPCRs, there are no reports describing SSTR (GPCR) modulation of ErbBs (RTK) in breast cancer. To the best of our knowledge, this is the first report describing crosstalk/interactions between SSTRs and ErbBs.
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Li M, Wang X, Li W, Li F, Yang H, Wang H, Brunicardi FC, Chen C, Yao Q, Fisher WE. Somatostatin receptor-1 induces cell cycle arrest and inhibits tumor growth in pancreatic cancer. Cancer Sci 2008; 99:2218-23. [PMID: 18823376 DOI: 10.1111/j.1349-7006.2008.00940.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Functional somatostatin receptors (SSTR) are lost in human pancreatic cancer. Transfection of SSTR-1 inhibited pancreatic cancer cell proliferation in vitro. We hypothesize that stable transfection of SSTR-1 may inhibit pancreatic cancer growth in vivo possibly through cell cycle arrest. In this study, we examined the expression of SSTR-1 mRNA in human pancreatic cancer tissue specimens, and investigated the effect of SSTR-1 overexpression on cell proliferation, cell cycle, and tumor growth in a subcutaneous nude mouse model. We found that SSTR-1 mRNA was downregulated in the majority of pancreatic cancer tissue specimens. Transfection of SSTR-1 caused cell cycle arrest at the G(0)/G(1) growth phase, with a corresponding decline of cells in the S (mitotic) phase. The overexpression of SSTR-1 significantly inhibited subcutaneous tumor size by 71% and 43% (n = 5, P < 0.05, Student's t-test), and inhibited tumor weight by 69% and 47% (n = 5, P < 0.05, Student's t-test), in Panc-SSTR-1 and MIA-SSTR-1 groups, respectively, indicating the potent inhibitory effect of SSTR-1 on pancreatic cancer growth. Our data demonstrate that overexpression of SSTR-1 significantly inhibits pancreatic cancer growth possibly through cell cycle arrest. This study suggests that gene therapy with SSTR-1 may be a potential adjuvant treatment for pancreatic cancer.
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Affiliation(s)
- Min Li
- Michael E DeBakey Department of Surgery, Molecular Surgeon Research Center, Baylor College of Medicine, Houston, Texas, USA.
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20
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Florio T. Somatostatin/somatostatin receptor signalling: phosphotyrosine phosphatases. Mol Cell Endocrinol 2008; 286:40-8. [PMID: 17913342 DOI: 10.1016/j.mce.2007.08.012] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 07/27/2007] [Accepted: 08/25/2007] [Indexed: 01/06/2023]
Abstract
Activation of phosphotyrosine phosphatases (PTPs) by somatostatin receptor (SSTR) represents one of the main intracellular mechanisms involved in the antiproliferative effect of somatostatin (SST) and analogues. Since their molecular cloning, the role of PTPs is emerging as a major regulator of different cell functions including cell proliferation, differentiation, cell to cell interactions, cell matrix adhesion and cell migration. It was demonstrated that PTPs possess high substrate specificity and their activity is tightly regulated. Importantly, different G protein-coupled receptors transduce their biological activities through PTPs. PTPs were identified as down-stream effectors of SSTRs to transduce antiproliferative signals, and so far, three family members (SHP-1, SHP-2 and DEP-1/PTPeta) have been identified as selective SSTR intracellular effectors. Here, the molecular mechanisms leading SSTRs to regulate PTP activity are discussed, focusing on recent data showing a close interplay between PTPs and tyrosine kinases to transduce tumoral cell growth arrest following SST analogs administration.
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Affiliation(s)
- Tullio Florio
- Department of Oncology, Biology and Genetics, University of Genova, Genova, Italy.
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21
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Watt HL, Kharmate G, Kumar U. Biology of somatostatin in breast cancer. Mol Cell Endocrinol 2008; 286:251-61. [PMID: 18308465 DOI: 10.1016/j.mce.2008.01.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Revised: 01/02/2008] [Accepted: 01/15/2008] [Indexed: 01/29/2023]
Abstract
The biological effects of the neuropeptide somatostatin (SST) are mediated via a family of five somatostatin receptors (SSTRs) belonging to a family of G-protein-coupled receptors (GPCRs). SSTR regulate the secretion of hormones, growth factors, neurotransmission and cell growth in receptor-specific manner. In addition, SST plays an inhibitory role in several mammary cancer models. These effects are mediated both indirectly through inhibition of hormones and growth factors which promote tumor growth as well as directly via SSTRs present on tumor cells to inhibit mitogenic signaling of growth factor receptor kinases leading to growth arrest and induction of apoptosis. Here, we present an overview on the role of SST and its analogs in breast cancer.
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Affiliation(s)
- Heather L Watt
- Department of Medicine, Royal Victoria Hospital, McGill University, Canada
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22
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Bocci G, Culler MD, Fioravanti A, Orlandi P, Fasciani A, Colucci R, Taylor JE, Sadat D, Danesi R, Del Tacca M. In vitro antiangiogenic activity of selective somatostatin subtype-1 receptor agonists. Eur J Clin Invest 2007; 37:700-8. [PMID: 17696959 DOI: 10.1111/j.1365-2362.2007.01848.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Endothelial cells of human blood vessels (arteries and veins) show high levels of somatostatin subtype-1 receptor (sst(1)). The aim of the present study is to investigate the inhibitory effects of novel somatostatin analogs, highly selective for human sst(1), on in vitro angiogenesis and their modulation of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) expression. MATERIALS AND METHODS Somatostatin analogs BIM-23745 and BIM-23926 were tested for their ability to prevent proliferation and migration of human endothelial HMEC-1 cells, to modulate VEGF and VEGFR-2 expression and to inhibit sprouting of microvessels from cultured human placental vessel explants in fibrin matrix for 28 days. RESULTS The somatostatin sst(1 )receptor-selective agonists, BIM-23745 and BIM-23926 showed a suppression of endothelial proliferation (e.g. 10(-6) M BIM-23475, 40.0 +/- 2.1% vs. 100% of controls; 10(-7) M BIM-23926, 55.3 +/- 3.3% vs. 100% of controls), migration (e.g. 10(-7) M BIM-23475, 35.0 +/- 1.56% vs. 100% of controls; 10(-7) M BIM-23926, 53.7 +/- 1.77% vs. 100% of controls) and microvessel sprouting (e.g. 10(-8) M BIM-23475, 42.8 +/- 5.6% vs. 100% of controls; 10(-7) M BIM-23926, 17.2 +/- 11.8% vs. 100% of controls). A small but significant percentage of cells exposed to BIM-23745 and BIM-23926 for 24 h and for 72 h presented typical apoptotic morphology. Moreover, both the analogs significantly inhibit VEGF and VEGFR-2 gene expression in endothelial cells grown for 144 h in a fibrin matrix and the VEGF secretion in conditioned media. CONCLUSIONS The inhibition of endothelial activities suggests potential therapeutic utility for administration of somatostatin sst(1 )receptor-selective agonists in the proliferative diseases involving angiogenesis.
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Affiliation(s)
- G Bocci
- University of Pisa, Pisa, Italy.
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23
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Ludvigsen E. Somatostatin receptor expression and biological functions in endocrine pancreatic cells: review based on a doctoral thesis. Ups J Med Sci 2007; 112:1-20. [PMID: 17578804 DOI: 10.3109/2000-1967-091] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Type 1 diabetes is resulting from the selective destruction of insulin-producing betacells within the pancreatic islets. Somatostatin acts as an inhibitor of hormone secretion through specific receptors (sst1-5). All ssts were expressed in normal rat and mouse pancreatic islets, although the expression intensity and the co-expression pattern varied between ssts as well as between species. This may reflect a difference in response to somatostatin in islet cells of the two species. The Non-Obese Diabetic (NOD) mouse model is an experimental model of type 1 diabetes, with insulitis accompanied by spontaneous hyperglycaemia. Pancreatic specimens from NOD mice at different age and stage of disease were stained for ssts. The islet cells of diabetic NOD mice showed increased islet expression of sst2-5 compared to normoglycemic NOD mice. The increase in sst2-5 expression in the islets cells may suggest either a contributing factor in the process leading to diabetes, or a defense response against ongoing beta-cell destruction. Somatostatin analogues were tested on a human endocrine pancreatic tumour cell line and cultured pancreatic islets. Somatostatin analogues had an effect on cAMP accumulation, chromogranin A secretion and MAP kinase activity in the cell line. Treatment of rat pancreatic islets with somatostatin analogues with selective receptor affinity was not sufficient to induce an inhibition of insulin and glucagon secretion. However, a combination of selective analogues or non-selective analogues via costimulation of receptors can cause inhibition of hormone production. For insulin and glucagon, combinations of sst2 + sst5 and sst1 + sst2, respectively, showed a biological effect. In summary, knowledge of islet cell ssts expression and the effect of somatostatin analogues with high affinity to ssts may be valuable in the future attempts to influence beta-cell function in type 1 diabetes mellitus, since down-regulation of beta-cell function may promote survival of these cells during the autoimmune attack.
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Affiliation(s)
- Eva Ludvigsen
- Department of Medical Cell Biology, Uppsala universitet.
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24
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Watt HL, Kumar U. Colocalization of somatostatin receptors and epidermal growth factor receptors in breast cancer cells. Cancer Cell Int 2006; 6:5. [PMID: 16519802 PMCID: PMC1479379 DOI: 10.1186/1475-2867-6-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 03/06/2006] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Somatostatin receptor (SSTR) expression is positively correlated with tumor size and inversely correlated with epidermal growth factor receptor (ErbB) levels and tumor differentiation. In the present study, we compared SSTR1-5 and ErbB1-4 mRNA and protein expression in two breast cancer cell lines: MCF-7 (ER+) and MDA-MB-231 (ERalpha-). RESULTS All five SSTRs and four ErbBs were variably expressed as both cell surface and cytoplasmic proteins. In both cell lines, SSTR4 and SSTR1 were highly expressed, followed by SSTR2 and SSTR5 with SSTR3 being the least expressed subtype, at the protein level. ErbBs were variably expressed with ErbB1 as the predominant subtype in both cell lines. ErbB1 is followed by ErbB3, ErbB2 and ErbB4 in MCF-7 at both the protein and mRNA levels. In MDA-MB-231 cells, ErbB1 is followed by ErbB2, ErbB4 and ErbB3. Our results indicate significant correlations at the level of mRNA and protein expression in a cell and receptor-specific manner. Using indirect immunofluorescence, we found that, in MCF-7 cells, SSTR5 was the most prominent subtype coexpressed with ErbBs followed by SSTR3, SSTR4, SSTR1 and SSTR2, respectively. In MDA-MB-231 cells, SSTR1 colocalized strongly with ErbBs followed by SSTR5, SSTR4, SSTR3 and SSTR2. ErbBs displayed higher levels of colocalization amongst themselves in MCF-7 cells than in MDA-MB-231 cells. CONCLUSION These findings may explain the poor response to endocrine therapy in ER-cancer. Differential distribution of SSTR subtypes with ErbBs in breast cancer cells in a receptor-specific manner may be considered as a novel diagnosis for breast tumors.
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Affiliation(s)
- Heather L Watt
- Fraser Laboratories For Diabetes Research, Department of Medicine, Royal Victoria Hospital, McGill University, Montreal, Quebec, H3A 1A1, Canada
| | - Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, The University of British Columbia, Vancouver, BC, Canada
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Theodoropoulou M, Zhang J, Laupheimer S, Paez-Pereda M, Erneux C, Florio T, Pagotto U, Stalla GK. Octreotide, a Somatostatin Analogue, Mediates Its Antiproliferative Action in Pituitary Tumor Cells by Altering Phosphatidylinositol 3-Kinase Signaling and Inducing Zac1 Expression. Cancer Res 2006; 66:1576-82. [PMID: 16452215 DOI: 10.1158/0008-5472.can-05-1189] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Somatostatin limits cell growth by inhibiting the proliferative activity of growth factor receptors. In this study, it is shown that in pituitary tumor cells, the somatostatin analogue octreotide produces its antiproliferative action by inducing the expression the tumor suppressor gene Zac1. ZAC/Zac1 induces cell cycle arrest and apoptosis and is highly expressed in normal pituitary, mammary, and ovarian glands but is down-regulated in pituitary, breast, and ovarian tumors. Knocking down Zac1 by RNA interference abolished the antiproliferative effect of octreotide in pituitary tumor cells, indicating that Zac1 is necessary for the action of octreotide. The effect of octreotide on Zac1 expression was pertussis toxin sensitive and was abolished after transfection with a dominant negative vector for SHP-1. Zac1 is a target of the phosphatidylinositol 3-kinase (PI3K) survival pathway. Octreotide treatment decreased the tyrosine phosphorylation levels of the PI3K regulatory subunit p85, induced dephosphorylation of phosphoinositide-dependent kinase 1 (PDK1) and Akt, and activated glycogen synthase kinase 3beta (GSKbeta). Therefore, in pituitary tumor cells, somatostatin analogues produce their antiproliferative action by acting on the PI3K/Akt signaling pathway and increasing Zac1 gene expression.
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Affiliation(s)
- Marily Theodoropoulou
- Department of Endocrinology, Max Planck Institute of Psychiatry, Kraepelinstrasse 10, D-80804 Munich, Germany.
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26
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Carrere N, Vernejoul F, Souque A, Asnacios A, Vaysse N, Pradayrol L, Susini C, Buscail L, Cordelier P. Characterization of the Bystander Effect of Somatostatin Receptor sst2 After In Vivo Gene Transfer into Human Pancreatic Cancer Cells. Hum Gene Ther 2005; 16:1175-93. [PMID: 16218779 DOI: 10.1089/hum.2005.16.1175] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Pancreatic cancer is one of the most aggressive and devastating human malignancies. The present study was conducted to determine whether in vivo sst2 gene transfer into human pancreatic tumors would impair tumor progression, and to characterize sst2 antitumoral bystander mechanisms. sst2 administration, using the synthetic vector PEI, strongly inhibited tumor progression of human pancreatic adenocarcinoma, in vivo. sst2 gene transfer induced intratumoral production of its ligand somatostatin. Disruption of this autocrine loop by RNA interference completely reversed sst2 antitumoral activity. Mice depleted of natural killer (NK) cells did not hamper sst2 tumor growth inhibition. However, microvessel density and vascular endothelial growth factor (VEGF) expression were markedly reduced in sst2-transfected tumors, whereas sst3 somatostatin receptor was upregulated. Depleting somatostatin by RNA interference completely abolished the sst2 inhibitory effect on VEGF expression and tumor angiogenesis, and sst2-induced sst3 expression in peripheral tumor vessels. We conclude that in vivo sst2 gene transfer elicited intratumoral somatostatin production and strongly impaired human pancreatic tumor growth. NK cells were not involved in this antitumoral bystander effect. VEGF and tumor vascularization were identified as novel targets for sst2-mediated antitumoral bystander effect. sst3 somatostatin receptor was upregulated in sst2-transfected tumors. Therefore, in vivo gene delivery of sst2 receptor to target the angiogenic process in pancreatic ductal adenocarcinoma might be a new therapeutic approach for treatment of pancreatic cancer in patients with unresectable disease.
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Affiliation(s)
- Nicolas Carrere
- INSERM U531, Institut Louis Bugnard, IFR31, CHU Rangueil, 31432 Toulouse, France
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27
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Carrere N, Vernejoul F, Souque A, Asnacios A, Vaysse N, Pradayrol L, Susini C, Buscail L, Cordelier P. Characterization of the Bystander Effect of Somatostatin Receptor sst2 After In Vivo Gene Transfer into Human Pancreatic Cancer Cells. Hum Gene Ther 2005. [DOI: 10.1089/hum.2005.16.ft-120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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28
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Adams RL, Adams IP, Lindow SW, Zhong W, Atkin SL. Somatostatin receptors 2 and 5 are preferentially expressed in proliferating endothelium. Br J Cancer 2005; 92:1493-8. [PMID: 15812556 PMCID: PMC2362009 DOI: 10.1038/sj.bjc.6602503] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Angiogenesis is characterised by activation, migration and proliferation of endothelial cells and is central to the pathology of cancer, cardiovascular disease and chronic inflammation. Somatostatin is an inhibitory polypeptide that acts through five receptors (sst 1, 2, 3, 4, 5). Sst has previously been reported in endothelium, but their role remains obscure. Here, we report the expression of sst in human umbilical vein endothelial cells (HUVECs) in vitro, during proliferation and quiescence. A protocol for culturing proliferating and quiescent HUVECs was established, and verified by analysing cell cycle distribution in propidium-iodide-stained samples using flow cytometry. Sst mRNA was then quantified in nine proliferating and quiescent HUVEC lines using quantitative reverse transcriptase–polymerase chain reaction. Sst 2 and 5 were preferentially expressed in proliferating HUVECs. All samples were negative for sst 4. Sst 1 and 3 expression and cell cycle progression were unrelated. Immunostaining for sst 2 and 5 showed positivity in proliferating but not quiescent cells, confirming sst 2 and 5 protein expression. Inhibition of proliferating cells with somatostatin analogues Octreotide and SOM230, which have sst 5 activity, was found (Octreotide 10−10–10−6 M: 48.5–70.2% inhibition; SOM230 10−9–10−6 M: 44.9–65.4% inhibition) in a dose-dependent manner, suggesting that sst 5 may have functional activity in proliferation. Dynamic changes in sst 2 and 5 expression during the cell cycle and the inhibition of proliferation with specific analogues suggest that these receptors may have a role in angiogenesis.
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Affiliation(s)
- R L Adams
- Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical School, Hull HU6 7RX, UK
| | - I P Adams
- Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical School, Hull HU6 7RX, UK
| | - S W Lindow
- Department of Obstetrics and Gynecology, Hull Women and Children's Hospital, Hull HU3 2JZ, UK
| | - W Zhong
- Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical School, Hull HU6 7RX, UK
| | - S L Atkin
- Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical School, Hull HU6 7RX, UK
- The Michael White Diabetes Centre, 220-236, Anlaby Road, Hull HU3 2RW, UK. E-mail:
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Ludvigsen E, Stridsberg M, Taylor JE, Culler MD, Oberg K, Janson ET. Subtype selective interactions of somatostatin and somatostatin analogs with sst1, sst2, and sst5 in BON-1 cells. Med Oncol 2005; 21:285-95. [PMID: 15456957 DOI: 10.1385/mo:21:3:285] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 03/24/2004] [Indexed: 01/02/2023]
Abstract
Somatostatin is a polypeptide hormone acting as an inhibitor of pituitary, pancreatic, and gastrointestinal secretion through specific membrane receptors of which five subtypes have been cloned (sst(1-5)). Somatostatin analogs are used in the clinic to treat patients with excessive hormone production due to a neuroendocrine tumor. The aim of this study was to investigate the biological activity of three new somatostatin receptor subtype selective analogs (BIM-23926, sst(1)-selective; BIM-23120, sst(2)-selective; and BIM-23206, sst(5)-selective) in the human neuroendocrine tumor cell line, BON-1, which expresses sst(1), sst(2), and sst(5) natively. Somatostatin-14 and octreotide were used as reference substances. Forskolin-induced cAMP accumulation and chromogranin A (CgA) secretion were inhibited by BIM-23120, BIM-23206, and somatostatin-14 in a dose-dependent manner. Cholecystokinin (CCK-8) stimulated activation of mitogen-activated protein (MAP) kinase was inhibited by BIM-23120 and BIM-23206, while BIM-23926 stimulated the activity. Selective BIM analogs showed a more efficient inhibitory effect on cAMP accumulation, CgA secretion, and MAP kinase activity than octreotide in BON-1 cells. This may be explained by the differences in affinity of the ligand to the receptor or by interaction between different sst subtypes. We conclude that increasing knowledge about sst physiology and expression in malignant disease indicates a need for new analogs that can be incorporated into the therapeutic arsenal.
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Affiliation(s)
- Eva Ludvigsen
- Department of Medical Sciences, University Hospital, 751 85 Uppsala, Sweden
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Maunoury V, Wacrenier A, Malamut G, Desreumaux P. [Results of treatment with COX-2 inhibitors and lanreotide in a patient with Menetrier's hypertrophic gastropathy]. ACTA ACUST UNITED AC 2004; 28:407-8. [PMID: 15146161 DOI: 10.1016/s0399-8320(04)94946-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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31
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Adams RL, Adams IP, Lindow SW, Atkin SL. Inhibition of endothelial proliferation by the somatostatin analogue SOM230. Clin Endocrinol (Oxf) 2004; 61:431-6. [PMID: 15473874 DOI: 10.1111/j.1365-2265.2004.02098.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Somatostatin (SST) modulates exocrine and endocrine secretion, proliferation and apoptosis via five G protein-linked receptors (SSTRs 1-5). Long-acting SST analogues such as Octreotide, and the new analogue SOM230, have been developed for the treatment of neuroendocrine tumours. Octreotide has previously been reported to inhibit endothelial proliferation. We wished to determine if SOM230 is a more potent inhibitor of endothelial cell proliferation than Octreotide. DESIGN We have determined the expression of SSTRs in proliferating human umbilical vein endothelial cells (HUVECs) in vitro, and determined their response to the somatostatin analogues SOM230 and Octreotide, following vascular endothelial growth factor (VEGF) stimulation. MEASUREMENTS Quantitative RT-PCR and western blotting were used to determine the expression of SSTRs 1-5 in proliferating HUVECs. These cells were grown in media containing 200 pg/ml VEGF and treated with 10(-11) to 10(-6) M Octreotide or SOM230. The WST-1 assay was then used to determine the effects of these analogues on HUVEC proliferation. RESULTS Using quantitative RT-PCR and western blotting, HUVECs were found to express SSTRs 1, 2 and 5. SSTRs 3 and 4 were not detected. Using the WST-1 assay, SOM230 was found to significantly inhibit proliferation by up to 46.0% +/- 9.4% (10(-6)-10(-7) M; P < 0.05), whereas in parallel studies Octreotide failed to inhibit HUVEC proliferation. CONCLUSIONS The pan SST analogue SOM230 inhibits proliferation of HUVECs, which are unaffected by Octreotide. SOM230 may thus represent a suitable candidate drug for antiangiogenic therapy.
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Affiliation(s)
- Robyn L Adams
- Endocrinology Research Group, Division of Academic Medicine, University of Hull Postgraduate Medical Institute, UK.
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32
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Arena S, Pattarozzi A, Corsaro A, Schettini G, Florio T. Somatostatin receptor subtype-dependent regulation of nitric oxide release: involvement of different intracellular pathways. Mol Endocrinol 2004; 19:255-67. [PMID: 15388796 DOI: 10.1210/me.2004-0280] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We reported previously that, in addition to direct effects, somatostatin (SST) affects tumor growth inhibiting the tumoral neoangiogenesis, via an interference with NO synthesis. Here, we analyzed the effects of SST on nitric oxide (NO) production induced by different agonists [basic fibroblast growth factor (bFGF), insulin, cholecystokinin (CCK)] and the intracellular signaling involved, using Chinese hamster ovary-k1 cells stably transfected with individual SSTR1-SSTR4. bFGF and insulin induced endothelial nitric oxide synthase activity via the generation of ceramide or the Akt-dependent phosphorylation of endothelial nitric oxide synthase, respectively. CCK regulates neuronal nitric oxide synthase activity in a Ca++-dependent manner. SST inhibited NO production stimulated by bFGF through SST receptor 1 (SSTR1), SSTR2, and SSTR3 and by CCK through SSTR2 and SSTR3. In all the cell lines, SST treatment did not modify NO synthesis induced by insulin. SSTR4 activation was not effective on any of the stimuli tested. The effects on bFGF-induced NO production were downstream from receptor phosphorylation and ceramide synthesis. SSTR2 and -3 on CCK activity were related to the inhibition of intracellular Ca++ mobilization, whereas the lack of effects on insulin was paralleled by the absence of SST activity on Akt phosphorylation. These data, identifying for the first time a selective receptor subtype-inhibitory role of SST on NO generation, may open new perspectives in the use of SST agonists to control tumoral angiogenesis.
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Affiliation(s)
- Sara Arena
- Section of Pharacology, Department of Oncology, Biology and Genetics, University of Genova, and Pharmacology and Neuroscience, National Institute for Cancer Research (IST), 16132 Genova, Italy
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N/A, 王 承. N/A. Shijie Huaren Xiaohua Zazhi 2004; 12:184-189. [DOI: 10.11569/wcjd.v12.i1.184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/05/2023] Open
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D'Alessio A, Califano D, Incoronato M, Santelli G, Florio T, Schettini G, Carlomagno MS, Cerchia L, de Franciscis V. The tyrosine phosphatase Shp-2 mediates intracellular signaling initiated by Ret mutants. Endocrinology 2003; 144:4298-305. [PMID: 12959980 DOI: 10.1210/en.2003-0620] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Src homology 2-containing tyrosine phosphatase, Shp-2, is a crucial enzyme that mediates intracellular signaling and is implicated in cell proliferation and differentiation. Here we investigated the involvement of the Shp-2 tyrosine phosphatase in determining the downstream signaling pathways initiated by the Ret oncogene, carrying either the cysteine 634 to tyrosine or the methionine 918 to threonine substitutions. These mutations convert the receptor tyrosine kinase, Ret, into a dominant transforming protein and induce constitutive activation of its intrinsic tyrosine kinase activity leading to congenital and sporadic cancers in neuroendocrine organs. Using the PC12, rat pheochromocytoma cell line, as model system, we show that Shp-2 mediates immediate-early gene expression if induced by either of the mutant alleles. Furthermore, we show that Shp-2 activity is required for RetM918T-induced Akt activation. The results indicate that Shp-2 is a downstream mediator of the mutated receptors RetC634Y and RetM918T, thus suggesting that it may act as a limiting factor in Ret-associated endocrine tumors, in the neoplastic syndromes multiple endocrine neoplasia types 2A and 2B.
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Affiliation(s)
- A D'Alessio
- Oncologia Sperimentale E, Istituto Nazionale Tumori, Fondazione G. Pascale, 80131 Naples, Italy
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35
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Stirnweiss J, Hartrodt B, Greksch G, Stürzebecher U, Böhmer FD, Neubert K, Liebmann C. Tyr-c[D-Orn-Tyr(Bzl)-Pro-Gly]: a novel antiproliferative acting somatostatin receptor agonist with mu-opioid receptor-sensitizing properties. Br J Pharmacol 2003; 140:13-22. [PMID: 12967930 PMCID: PMC1574013 DOI: 10.1038/sj.bjp.0705416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
(1) Here, we introduce a beta-casomorphin-5-derived cyclic pentapeptide, cCD-2 (Tyr-cyclo[d-Orn-Tyr(Bzl)-Pro-Gly]), which inhibits the cell growth of a variety of human cancer cell lines. (2) This opioid-derived peptide possesses only low affinity for mu-receptors, but enhances the agonist binding to mu-receptors in vitro and potentiates the analgesic effect of morphin in vivo. The molecular mechanism of mu-receptor sensitization by cCD-2 is not yet known. (3) The antiproliferative effect of cCD-2 is independent of mu-, delta-, and kappa-receptors. (4) Using SH-SY5Y cells as model, we can demonstrate that cCD-2 specifically binds to somatostatin receptors and stimulates the activity of protein tyrosine phosphatases, which are early downstream targets of SST receptors. (5) In SH-SY5Y cells, cCD-2 specifically increases the activity of the cytosolic PTP SHP-2, stimulates the activity of mitogen-activated protein kinase (MAPK), and elevates the expression of the cyclin-dependent kinase inhibitor p21 (WAF1/Cip1), suggesting the involvement of SSTR1 receptor subtype in cCD-2 action in this cell type. (6) In COS-7 cells, for comparison, we found a stimulation of SHP-2 as well as SHP-1 in response to cCD-2. The activation of SHP-1, which is attributed to the SSTR2 receptor and negatively regulates the EGF receptor, corresponds with the ability of cCD-2 to inhibit the EGF-induced MAPK activation in COS-7 cells. (7) Our results show that in SH-SY5Y cells cCD-2 inhibits cell growth via the SSTR1 receptor-signalling pathway but may, in other cells, also use other SSTR subtypes and their signalling mechanisms. (8) cCD-2 represents a novel type of opioid-derived antiproliferative SST receptor agonist, which possesses low mu-receptor affinity but may induce mu-receptor sensitization and is structurally different from the hitherto known SST receptor agonists.
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MESH Headings
- Cell Division/drug effects
- Cell Division/physiology
- Cell Line, Tumor
- Dose-Response Relationship, Drug
- Endorphins/chemistry
- Endorphins/metabolism
- Endorphins/pharmacology
- Growth Inhibitors/chemistry
- Growth Inhibitors/metabolism
- Growth Inhibitors/pharmacology
- Humans
- Narcotic Antagonists/pharmacology
- Pain Measurement/drug effects
- Pain Measurement/methods
- Peptide Fragments/chemistry
- Peptide Fragments/metabolism
- Peptide Fragments/pharmacology
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Receptors, Somatostatin/agonists
- Receptors, Somatostatin/metabolism
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Affiliation(s)
- Jörg Stirnweiss
- Institute of Biochemistry and Biophysics, Biological and Pharmaceutical Faculty, Friedrich-Schiller-University Jena, Philosophenweg 12, Jena D-07743, Germany
| | - Bianka Hartrodt
- Department of Biochemistry and Biotechnology, Institute of Biochemistry, University of Halle, Halle D-06120, Germany
| | - Gisela Greksch
- Institute of Pharmacology and Toxicology, Faculty of Medicine, University of Magdeburg, Magdeburg D-39120, Germany
| | - Uta Stürzebecher
- Institute of Biochemistry and Biophysics, Biological and Pharmaceutical Faculty, Friedrich-Schiller-University Jena, Philosophenweg 12, Jena D-07743, Germany
| | - Frank-D Böhmer
- Institute of Molecular Cell Biology, Medical Faculty, Friedrich-Schiller-University Jena, Jena D-07747, Germany
| | - Klaus Neubert
- Department of Biochemistry and Biotechnology, Institute of Biochemistry, University of Halle, Halle D-06120, Germany
| | - Claus Liebmann
- Institute of Biochemistry and Biophysics, Biological and Pharmaceutical Faculty, Friedrich-Schiller-University Jena, Philosophenweg 12, Jena D-07743, Germany
- Author for correspondence:
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Lin CY, Varma MG, Joubel A, Madabushi S, Lichtarge O, Barber DL. Conserved motifs in somatostatin, D2-dopamine, and alpha 2B-adrenergic receptors for inhibiting the Na-H exchanger, NHE1. J Biol Chem 2003; 278:15128-35. [PMID: 12566440 DOI: 10.1074/jbc.m212315200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor subtypes within families of G protein-coupled receptors that are activated by similar ligands can regulate distinct intracellular effectors. We identified conserved motifs within intracellular domains 2 and 3 of selective subtypes of several G protein-coupled receptor families that confer coupling to the Na-H exchanger, NHE1. A T(s,p)V motif within intracellular domain 2 and a QQ(r) motif within intracellular domain 3 are shared by the somatostatin receptor subtypes SSTR1, -3, and -4, which couple to the inhibition of NHE1, but not by SSTR2 and -5, which do not signal to NHE1. Only the collective substitution of cognate SSTR2 residues with these two motifs conferred the ability of mutant SSTR2 to inhibit NHE1. Both motifs are present in D(2)-dopamine receptors, which inhibit NHE1, and in alpha(2B)-adrenergic receptors, which couple to the inhibition of NHE1, but not in alpha(2A)-adrenergic receptors, which do not regulate NHE1. These findings indicate that motifs shared by different subfamilies of G protein-coupled receptors, but not necessarily by receptor subtypes within a subfamily, can confer coupling to a common effector.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Conserved Sequence
- Membrane Proteins
- Rats
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/metabolism
- Receptors, Dopamine D2/chemistry
- Receptors, Dopamine D2/metabolism
- Receptors, Somatostatin/chemistry
- Receptors, Somatostatin/metabolism
- Sequence Alignment
- Signal Transduction
- Sodium-Hydrogen Exchangers/antagonists & inhibitors
- Sodium-Hydrogen Exchangers/metabolism
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Affiliation(s)
- Chin-Yu Lin
- University of California, San Francisco, San Francisco, California 94143, USA
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Levy-Nissenbaum O, Sagi-Assif O, Witz IP. Characterization of the dual-specificity phosphatasePYST2 and its transcripts. Genes Chromosomes Cancer 2003; 39:37-47. [PMID: 14603440 DOI: 10.1002/gcc.10295] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PYST2 is a member of a structurally homologous subfamily of MAP kinase phosphatases. A computer-based analysis of the PYST2 locus revealed that it harbors two alternative open reading frames promoted by two conserved promoter regions. Using Northern blot analysis and reverse transcription-polymerase chain reaction followed by sequencing and alignment of the products, we confirmed the existence of two mRNAs that were transcribed from this genomic region. Western blot analysis indicated that these transcripts were translated. Functional bioinformatic analysis of both transcripts revealed that exon 2 exists in only one of the PYST2 transcripts, designated PYST2-L, and has the consensus elements of the phosphatase catalytic domain (PCD). We found that the translation from the PYST2-L transcript starts 46 codons upstream from the (already-known) PYST2 5' sequence. Furthermore, the existence of three PYST2-L transcripts was indicated. These transcripts differ only in their 5' untranslated regions (5'UTRs). Unlike PYST2-L, the other mRNA (PYST2-S) is devoid of any known PCD. Analysis of the predicted Pyst2-S protein revealed the presence of the vertebrate metallothionein signature I, the mammalian defensin, and the zinc-containing alcohol dehydrogenase motifs. These motifs might confer on this protein the ability to sense changes in the cellular environment. From these and previous results, we speculate that Pyst2-S may function as a negative regulator of Pyst2-L.
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Affiliation(s)
- Orlev Levy-Nissenbaum
- Department of Cell Research and Immunology, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Burdon D, Patel R, Challiss RAJ, Blank JL. Growth inhibition by the muscarinic M(3) acetylcholine receptor: evidence for p21(Cip1/Waf1) involvement in G(1) arrest. Biochem J 2002; 367:549-59. [PMID: 12126481 PMCID: PMC1222904 DOI: 10.1042/bj20020446] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2002] [Revised: 07/04/2002] [Accepted: 07/18/2002] [Indexed: 12/30/2022]
Abstract
We have assessed the growth response of Chinese-hamster ovary (CHO) cells to activation of recombinantly expressed G-protein-coupled muscarinic M(2) or M(3) acetylcholine receptors (AChRs). We show that activation of these receptors leads to divergent growth responses: M(2) AChR activation causes an increase in DNA synthesis, whereas M(3) AChR activation causes a dramatic decrease in DNA synthesis. We have characterized the M(3) AChR-mediated growth inhibition and show that it involves a G(1) phase cell-cycle arrest. Further analysis of this arrest indicates that it involves an increase in expression of the cyclin-dependent kinase (CDK) inhibitor, p21(Cip1/Waf1) (where Cip1 is CDK-interacting protein 1 and Waf1 is wild-type p53-associated fragment 1), in response to M(3) AChR activation. This increase in protein expression leads to an increase in p21(Cip1/Waf1) association with CDK2, a decrease in CDK2 activity and an accumulation of hypophosphorylated retinoblastoma protein. The increased p21(Cip1/Waf1) expression is due, at least in part, to an increase in p21(Cip1/Waf1) mRNA, and receptor-mediated changes in phosphorylation of c-Jun provide a mechanism to account for this p21(Cip1/Waf1) transcriptional regulation. Evaluation of the extracellular signal-regulated protein kinase and c-Jun N-terminal kinase activities has shown striking differences in the profiles of activation of these mitogen-activated protein kinases by the M(2) and M(3) AChRs, and their potential involvement in mediating growth arrest by the M(3) AChR is discussed.
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Affiliation(s)
- Drew Burdon
- Department of Cell Physiology and Pharmacology, University of Leicester School of Medicine, Medical Sciences Building, University Road, P.O. Box 138, Leicester LE1 9HN, U.K
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39
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Richard M, Veilleux P, Rouleau M, Paquin R, Beaulieu AD. The expression pattern of the ITIM‐bearing lectin CLECSF6 in neutrophils suggests a key role in the control of inflammation. J Leukoc Biol 2002. [DOI: 10.1189/jlb.71.5.871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Manon Richard
- Laboratoire de Recherche sur l’Arthrite et l’Inflammation, Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université Laval, Sainte‐Foy, Québec, Canada
| | - Patricia Veilleux
- Laboratoire de Recherche sur l’Arthrite et l’Inflammation, Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université Laval, Sainte‐Foy, Québec, Canada
| | - Michèle Rouleau
- Laboratoire de Recherche sur l’Arthrite et l’Inflammation, Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université Laval, Sainte‐Foy, Québec, Canada
| | - Robert Paquin
- Laboratoire de Recherche sur l’Arthrite et l’Inflammation, Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université Laval, Sainte‐Foy, Québec, Canada
| | - André D. Beaulieu
- Laboratoire de Recherche sur l’Arthrite et l’Inflammation, Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université Laval, Sainte‐Foy, Québec, Canada
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40
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Kowluru A, Morgan NG. GTP-binding proteins in cell survival and demise: the emerging picture in the pancreatic beta-cell. Biochem Pharmacol 2002; 63:1027-35. [PMID: 11931834 DOI: 10.1016/s0006-2952(02)00849-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is widely believed that guanine nucleotide-binding regulatory proteins (G-proteins) play central roles as "molecular switches" in a variety of cellular processes ranging from signal transduction to protein and vesicle trafficking. To achieve these regulatory functions, G-proteins form complexes with a wide range of effector molecules whose activities are altered upon interaction with the G-protein. These effector molecules can be either soluble or membrane bound, and it is likely that some are localized to secretory granules where they direct the movement, docking, and fusion of granules during exocytosis. The effector molecules regulated by G-proteins are diverse and include phospholipases, protein kinases, protein phosphatases, ion channels, adenylate cyclases, cytoskeletal elements, as well as secretory vesicle and plasma membrane-associated fusion-proteins. The majority of studies performed in the pancreatic beta-cell have focused on the role of G-proteins in the regulation of insulin secretion, whereas very little attention has been focused on their potential involvement in other cellular processes. Such studies have identified and implicated both heterotrimeric (comprising alpha, beta, and gamma subunits) and monomeric (low molecular mass) G-proteins in the regulation of insulin secretion, but intriguing recent evidence has also begun to emerge which favors the view that they may be involved in the maintenance of beta-cell viability. In the present commentary, we will review this evidence and discuss the current understanding of the role of G-proteins in the life and death of the beta-cell.
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Affiliation(s)
- Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, College of Pharmacy and Allied Health Professions, Wayne State University, 619 Shapero Hall, Detroit, MI 48202, USA.
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41
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Komatsuzaki K, Terashita K, Kinane TB, Nishimoto I. Somatostatin type V receptor activates c-Jun N-terminal kinases via Galpha(12) family G proteins. Biochem Biophys Res Commun 2001; 289:1211-7. [PMID: 11741322 DOI: 10.1006/bbrc.2001.6085] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Somatostatin is a neurotransmitter with diverse effects including anti-proliferation in a wide range of normal and neoplastic cells, and occasionally growth stimulatory and neurotrophic actions. Stress-activated protein kinase or c-Jun N-terminal kinase (SAPK/JNK) can also induce growth arrest and occasionally growth stimulation. However, the relationship between somatostatin and SAPK/JNK is less clear. Here we report that the binding of somatostatin to the somatostatin receptor type V (SSTR5) upregulates SAPK/JNK activity. We also show that this activation is mediated by Galpha(12) and Galpha(13). This study demonstrates that SSTR5 is the heptahelical receptor that activates SAPK/JNK via the G(12) family G proteins.
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Affiliation(s)
- K Komatsuzaki
- Department of Pediatrics, Pediatric Pulmonary Service, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, USA
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42
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Lu HT, Salamon H, Horuk R. The biology and physiology of somatostatin receptors. Expert Opin Ther Targets 2001; 5:613-623. [PMID: 12540287 DOI: 10.1517/14728222.5.5.613] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The biology and therapeutic application of somatostatin and its receptors are reviewed. The focus is on recent literature and patents, especially with regard to the specific function of each somatostatin receptor subtype. Detailed mechanisms mediating the effects of somatostatin and its analogues remain to be elucidated. Nevertheless, progress is being made towards a clear picture of the cellular signalling and physiological changes regulated by somatostatin and its receptors.
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Affiliation(s)
- Hong-Tao Lu
- Berlex Biosciences, Department of Immunology, 15049 San Pablo Ave, Richmond, California 94804, USA.
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