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Kumar U. Somatostatin and Somatostatin Receptors in Tumour Biology. Int J Mol Sci 2023; 25:436. [PMID: 38203605 PMCID: PMC10779198 DOI: 10.3390/ijms25010436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 12/24/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that 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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Sosa LDV, Picech F, Perez P, Gutierrez S, Leal RB, De Paul A, Torres A, Petiti JP. Regulation of FGF2-induced proliferation by inhibitory GPCR in normal pituitary cells. Front Endocrinol (Lausanne) 2023; 14:1183151. [PMID: 37576961 PMCID: PMC10414184 DOI: 10.3389/fendo.2023.1183151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 07/13/2023] [Indexed: 08/15/2023] Open
Abstract
Introduction Intracellular communication is essential for the maintenance of the anterior pituitary gland plasticity. The aim of this study was to evaluate whether GPCR-Gαi modulates basic fibroblast growth factor (FGF2)-induced proliferative activity in normal pituitary cell populations. Methods Anterior pituitary primary cell cultures from Wistar female rats were treated with FGF2 (10ng/mL) or somatostatin analog (SSTa, 100nM) alone or co-incubated with or without the inhibitors of GPCR-Gαi, pertussis toxin (PTX, 500nM), MEK inhibitor (U0126, 100µM) or PI3K inhibitor (LY 294002, 10 μM). Results FGF2 increased and SSTa decreased the lactotroph and somatotroph BrdU uptak2e (p<0.05) whereas the FGF2-induced S-phase entry was prevented by SSTa co-incubation in both cell types, with these effects being reverted by PTX, U0126 or LY294002 pre-incubation. The inhibition of lactotroph and somatotroph mitosis was associated with a downregulation of c-Jun expression, a decrease of phosphorylated (p) ERK and pAKT. Furthermore, SSTa was observed to inhibit the S-phase entry induced by FGF2, resulting in a further increase in the number of cells in the G1 phase and a concomitant reduction in the number of cells in the S phases (p< 0.05), effects related to a decrease of cyclin D1 expression and an increase in the expression of the cell cycle inhibitors p27 and p21. Discussion In summary, the GPCR-Gαi activated by SSTa blocked the pro-proliferative effect of FGF2 in normal pituitary cells via a MEK-dependent mechanism, which acts as a mediator of both anti and pro-mitogenic signals, that may regulate the principal effectors of the G1 to S-phase transition.
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Affiliation(s)
- Liliana del V. Sosa
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Florencia Picech
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Pablo Perez
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Silvina Gutierrez
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Rodrigo Bainy Leal
- Universidade Federal de Santa Catarina, Florianópolis, Departamento de Bioquímica e Programa de Pós-graduação em Bioquímica, Centro de Ciências Biológicas, Santa Catarina, Brazil
| | - Ana De Paul
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Alicia Torres
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Juan Pablo Petiti
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
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Luo D, Ratnayake R, Atanasova KR, Paul VJ, Luesch H. Targeted and functional genomics approaches to the mechanism of action of lagunamide D, a mitochondrial cytotoxin from marine cyanobacteria. Biochem Pharmacol 2023; 213:115608. [PMID: 37201874 PMCID: PMC10353561 DOI: 10.1016/j.bcp.2023.115608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 05/20/2023]
Abstract
Lagunamide D, a cyanobacterial cyclodepsipeptide, exhibits potent antiproliferative activity against HCT116 colorectal cancer cells (IC50 5.1 nM), which were used to probe the mechanism of action. Measurements of metabolic activity, mitochondrial membrane potential, caspase 3/7 activity and cell viability indicate the rapid action of lagunamide D on mitochondrial function and downstream cytotoxic effects in HCT116 cells. Lagunamide D preferentially targets the G1 cell cycle population and arrests cells in G2/M phase at high concentration (32 nM). Transcriptomics and subsequent Ingenuity Pathway Analysis identified networks related to mitochondrial functions. Lagunamide D induced mitochondrial network redistribution at 10 nM, suggesting a mechanism shared with the structurally related aurilide family, previously reported to target mitochondrial prohibitin 1 (PHB1). Knockdown and chemical inhibition of ATP1A1 sensitized the cells to lagunamide D, as also known for aurilide B. We interrogated potential mechanisms behind this synergistic effect between lagunamide D and ATP1A1 knockdown by using pharmacological inhibitors and extended the functional analysis to a global level by performing a chemogenomic screen with a siRNA library targeting the human druggable genome, revealing targets that modulate susceptibility to lagunamide D. In addition to mitochondrial targets, the screen revealed hits involved in the ubiquitin/proteasome pathway, suggesting lagunamide D might exert its effects by additionally affecting proteostasis. Our analysis illuminated cellular processes of lagunamide D that can be modulated in parallel to mitochondrial functions. The identification of potential synergistic drug combinations that can alleviate undesirable toxicity may open possibilities to resurrect this class of compounds for anticancer therapy.
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Affiliation(s)
- Danmeng Luo
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States; Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, Gainesville, FL 32610, United States
| | - Ranjala Ratnayake
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States; Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, Gainesville, FL 32610, United States
| | - Kalina R Atanasova
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States; Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, Gainesville, FL 32610, United States
| | - Valerie J Paul
- Smithsonian Marine Station, Fort Pierce, FL 34949, United States
| | - Hendrik Luesch
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States; Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, Gainesville, FL 32610, United States.
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Tamura YO, Sugama J, Abe SI, Shimizu Y, Hirose H, Watanabe M. Selective somatostatin receptor 5 inhibition improves hepatic insulin sensitivity. Pharmacol Res Perspect 2023; 11:e01043. [PMID: 36585794 PMCID: PMC9803904 DOI: 10.1002/prp2.1043] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 11/21/2022] [Accepted: 12/08/2022] [Indexed: 01/01/2023] Open
Abstract
Diabetes is a metabolic disorder with an increasing global prevalence. Somatostatin (SST), a peptide hormone, regulates hormone secretion via five SST receptor (SSTR) subtypes (SSTR1-5) in a tissue-specific manner. As SSTR5 is expressed in pancreatic β-cells and intestinal L-cells, studies have suggested that SSTR5 regulates glucose tolerance through insulin and incretin secretion, thereby having a prominent role in diabetes. Moreover, SSTR5 knockout (KO) mice display enhanced insulin sensitivity; however, the underlying mechanism has not been clarified. Therefore, in this study, we investigate the effect of SSTR5 blockade on insulin resistance and the target organ using SSTR5 KO mice and a selective SSTR5 antagonist (compound-1). High-fat diet (HFD)-fed SSTR5 KO mice exhibited significantly lower homeostasis model assessment of insulin resistance (HOMA-IR) than HFD-fed wild-type mice. Two-week oral administration of compound-1 dose-dependently and significantly reduced changes in the levels of glycosylated hemoglobin (GHb), plasma glucose, plasma insulin, and HOMA-IR in male KK-Ay /Ta Jcl mice (KK-Ay mice), a model of obese type 2 diabetes with severe insulin resistance. Additionally, compound-1 significantly increased the glucose infusion rate while decreasing hepatic glucose production in male KK-Ay mice, as evidenced by hyperinsulinemic-euglycemic clamp analyses. In addition, compound-1 ameliorated the insulin-induced Akt phosphorylation suppression by octreotide in the liver of male C57BL/6J mice. Collectively, our results demonstrate that selective SSTR5 inhibition can improve insulin sensitivity by enhancing liver insulin action; thus, selective SSTR5 antagonists represent potentially novel therapeutic agents for type 2 diabetes.
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Affiliation(s)
- Yumiko Okano Tamura
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Jun Sugama
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Shin-Ichi Abe
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Yuji Shimizu
- Biomolecular Research Laboratories, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Hideki Hirose
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
| | - Masanori Watanabe
- Cardiovascular and Metabolic Drug Discovery Unit, Takeda Pharmaceutical Company Limited, Fujisawa, Japan
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Vitali E, Palagano E, Schiavone ML, Mantovani G, Sobacchi C, Mazziotti G, Lania A. Direct effects of octreotide on osteoblast cell proliferation and function. J Endocrinol Invest 2022; 45:1045-1057. [PMID: 35020172 DOI: 10.1007/s40618-022-01740-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 01/03/2022] [Indexed: 12/11/2022]
Abstract
PURPOSE Octreotide (OCT) is a first-generation somatostatin analog (SSA) used in the treatment of acromegaly and neuroendocrine tumors (NETs). In both diseases, OCT interacts with somatostatin receptors 2 and 5 (SSTR2 and SSTR5), inhibiting hormone hypersecretion and cell proliferation. Skeletal health is an important clinical concern in acromegaly and NETs, since acromegalic osteopathy and NET bone metastasis occur in a remarkable number of patients. While OCT's effect on NET and pituitary cells has been extensively investigated, its direct action on bone cells remains unknown. METHODS Here, we investigated OCT direct effects on cell proliferation, differentiation, mineralization, and chemoattractant capacity of murine primary osteoblasts and osteoblast cell line MC3T3-E1. RESULTS OCT inhibited osteoblasts and MC3T3-E1 cell proliferation (- 30 ± 16%, and - 22 ± 4%, both p < 0.05 vs control) and increased MC3T3-E1 cell apoptosis (+ 76 ± 32%, p < 0.05 vs control). The anti-proliferative action of OCT was mediated by SSTR2 and SSTR5 in MC3T3-E1, while its pro-apoptotic effect was abrogated in SSTR2-silenced cells. The analysis of genes related to the early and late phases of osteoblast differentiation showed that OCT did not affect Alp, Runx2, Bglap, Spp1, and Sost levels in MC3T3-E1 cells. Similarly, OCT did not affect ALP activity, mineralization, and osteoclastogenic induction. Finally, Vegfa expression decreased in OCT-treated MC3T3-E1 cells and OCT inhibited pancreatic NET cell migration toward the osteoblast-conditioned medium. CONCLUSION This study provides the first evidence of the direct action of OCT on osteoblasts which may have clinically relevant implications for the management of skeletal health in subjects with acromegaly and metastatic NETs.
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Affiliation(s)
- E Vitali
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090, Pieve Emanuele, MI, Italy
- Laboratory of Cellular and Molecular Endocrinology, IRCCS Humanitas Research Hospital, Rozzano, MI, Italy
| | - E Palagano
- National Research Council, Institute of Biosciences and BioResources (CNR-IBBR), Via Madonna del Piano-Polo Scientifico CNR 10, 50019, Sesto Fiorentino, FI, Italy
| | - M L Schiavone
- IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, MI, Italy
| | - G Mantovani
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
- Endocrinology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - C Sobacchi
- IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089, Rozzano, MI, Italy
- National Research Council, Institute of Genetic and Biomedical Research (CNR-IRGB), Via Fantoli 16/15, 20138, Milan, Italy
| | - G Mazziotti
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090, Pieve Emanuele, MI, Italy.
- Endocrinology, Diabetology and Andrology Unit, IRCCS Humanitas Research Hospital, Rozzano, MI, Italy.
| | - A Lania
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090, Pieve Emanuele, MI, Italy
- Endocrinology, Diabetology and Andrology Unit, IRCCS Humanitas Research Hospital, Rozzano, MI, Italy
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Ramnarine VR, Alshalalfa M, Mo F, Nabavi N, Erho N, Takhar M, Shukin R, Brahmbhatt S, Gawronski A, Kobelev M, Nouri M, Lin D, Tsai H, Lotan TL, Karnes RJ, Rubin MA, Zoubeidi A, Gleave ME, Sahinalp C, Wyatt AW, Volik SV, Beltran H, Davicioni E, Wang Y, Collins CC. The long noncoding RNA landscape of neuroendocrine prostate cancer and its clinical implications. Gigascience 2018; 7:4994835. [PMID: 29757368 PMCID: PMC6007253 DOI: 10.1093/gigascience/giy050] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 05/01/2018] [Indexed: 01/29/2023] Open
Abstract
Background Treatment-induced neuroendocrine prostate cancer (tNEPC) is an aggressive variant of late-stage metastatic castrate-resistant prostate cancer that commonly arises through neuroendocrine transdifferentiation (NEtD). Treatment options are limited, ineffective, and, for most patients, result in death in less than a year. We previously developed a first-in-field patient-derived xenograft (PDX) model of NEtD. Longitudinal deep transcriptome profiling of this model enabled monitoring of dynamic transcriptional changes during NEtD and in the context of androgen deprivation. Long non-coding RNA (lncRNA) are implicated in cancer where they can control gene regulation. Until now, the expression of lncRNAs during NEtD and their clinical associations were unexplored. Results We implemented a next-generation sequence analysis pipeline that can detect transcripts at low expression levels and built a genome-wide catalogue (n = 37,749) of lncRNAs. We applied this pipeline to 927 clinical samples and our high-fidelity NEtD model LTL331 and identified 821 lncRNAs in NEPC. Among these are 122 lncRNAs that robustly distinguish NEPC from prostate adenocarcinoma (AD) patient tumours. The highest expressed lncRNAs within this signature are H19, LINC00617, and SSTR5-AS1. Another 742 are associated with the NEtD process and fall into four distinct patterns of expression (NEtD lncRNA Class I, II, III, and IV) in our PDX model and clinical samples. Each class has significant (z-scores >2) and unique enrichment for transcription factor binding site (TFBS) motifs in their sequences. Enriched TFBS include (1) TP53 and BRN1 in Class I, (2) ELF5, SPIC, and HOXD1 in Class II, (3) SPDEF in Class III, (4) HSF1 and FOXA1 in Class IV, and (5) TWIST1 when merging Class III with IV. Common TFBS in all NEtD lncRNA were also identified and include E2F, REST, PAX5, PAX9, and STAF. Interrogation of the top deregulated candidates (n = 100) in radical prostatectomy adenocarcinoma samples with long-term follow-up (median 18 years) revealed significant clinicopathological associations. Specifically, we identified 25 that are associated with rapid metastasis following androgen deprivation therapy (ADT). Two of these lncRNAs (SSTR5-AS1 and LINC00514) stratified patients undergoing ADT based on patient outcome. Discussion To date, a comprehensive characterization of the dynamic landscape of lncRNAs during the NEtD process has not been performed. A temporal analysis of the PDX-based NEtD model has for the first time provided this dynamic landscape. TFBS analysis identified NEPC-related TF motifs present within the NEtD lncRNA sequences, suggesting functional roles for these lncRNAs in NEPC pathogenesis. Furthermore, select NEtD lncRNAs appear to be associated with metastasis and patients receiving ADT. Treatment-related metastasis is a clinical consequence of NEPC tumours. Top candidate lncRNAs FENDRR, H19, LINC00514, LINC00617, and SSTR5-AS1 identified in this study are implicated in the development of NEPC. We present here for the first time a genome-wide catalogue of NEtD lncRNAs that characterize the transdifferentiation process and a robust NEPC lncRNA patient expression signature. To accomplish this, we carried out the largest integrative study that applied a PDX NEtD model to clinical samples. These NEtD and NEPC lncRNAs are strong candidates for clinical biomarkers and therapeutic targets and warrant further investigation.
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Affiliation(s)
- Varune Rohan Ramnarine
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | | | - Fan Mo
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Noushin Nabavi
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | | | | | - Robert Shukin
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Sonal Brahmbhatt
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Alexander Gawronski
- Department of Computer Science, Simon Fraser University, Burnaby, BC, Canada
| | - Maxim Kobelev
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Mannan Nouri
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Dong Lin
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada.,Department of Experimental Therapeutics, BC Cancer Agency, Vancouver, BC, Canada
| | - Harrison Tsai
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Tamara L Lotan
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - R Jefferey Karnes
- Department of Urology, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Mark A Rubin
- Department of Pathology and Laboratory Medicine, Weill Cornell Cancer Center, Weill Cornell Medical College, New York, NY, USA
| | - Amina Zoubeidi
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Martin E Gleave
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Cenk Sahinalp
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada.,Department of Computer Science, Indiana University, Bloomington, IN, USA
| | - Alexander W Wyatt
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Stanislav V Volik
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Himisha Beltran
- Department of Medicine, Weill Cornell Cancer Center, Weill Cornell Medical College, New York, NY, USA
| | | | - Yuzhuo Wang
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada.,Department of Experimental Therapeutics, BC Cancer Agency, Vancouver, BC, Canada
| | - Colin C Collins
- Vancouver Prostate Centre & Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
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Dong H, Wei Y, Xie C, Zhu X, Sun C, Fu Q, Pan L, Wu M, Guo Y, Sun J, Shen H, Ye J. Structural and functional analysis of two novel somatostatin receptors identified from topmouth culter (Erythroculter ilishaeformis). Comp Biochem Physiol C Toxicol Pharmacol 2018; 210:18-29. [PMID: 29698686 DOI: 10.1016/j.cbpc.2018.04.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/18/2018] [Accepted: 04/20/2018] [Indexed: 12/14/2022]
Abstract
In the present study, we cloned and characterized two somatostatin (SS) receptors (SSTRs) from topmouth culter (Erythroculter ilishaeformis) designated as EISSTR6 and EISSTR7. Analysis of EISSTR6 and EISSTR7 signature motifs, 3D structures, and homology with the known members of the SSTR family indicated that the novel receptors had high similarity to the SSTRs of other vertebrates. EISSTR6 and EISSTR7 mRNA expression was detected in 17 topmouth culter tissues, and the highest level was observed in the pituitary. Luciferase reporter assay revealed that SS14 significantly inhibited forskolin-stimulated pCRE-luc promoter activity in HEK293 cells transiently expressing EISSTR6 and EISSTR7, indicating that the receptors can be activated by SS14. We also identified phosphorylation sites important for the functional activity of EISSTR6 and EISSTR7 by mutating Ser23, 43, 107, 196, 311 and Ser7, 29, 61, 222, 225 residues, respectively, to Ala, which significantly reduced the inhibitory effects of SS14 on the CRE promoter mediated by EISSTR6 and EISSTR7. Furthermore, treatment of juvenile topmouth culters with microcystin-LR or 17β-estradiol significantly affected EISSTR6 and EISSTR7 transcription in the brain, liver and spleen, suggesting that these receptors may be involved in the pathogenic mechanisms induced by endocrine disruptors. Our findings should contribute to the understanding of the structure-function relationship and evolution of the SSTR family.
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Affiliation(s)
- Haiyan Dong
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China; National-local Joint Engineering Laboratory of Aquatic Animal Genetic Breeding and Nutrition (Zhejiang), Zhejiang Provincial Key Laboratory of Aquatic Resources Conservation and Development, Key Laboratory of Aquatic Animal Genetic Breeding and Nutrition of Chinese Academy of Fishery Sciences, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China.
| | - Yunhai Wei
- Department of Gastrointestinal Surgery, the Central Hospital of Huzhou, 198 Hongqi Road, Huzhou, Zhejiang 313000, PR China
| | - Chao Xie
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Xiaoxuan Zhu
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Chao Sun
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Qianwen Fu
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Lei Pan
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Mengting Wu
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Yinghan Guo
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Jianwei Sun
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Hong Shen
- Department of Basic Medical Science, Huzhou University, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China
| | - Jinyun Ye
- National-local Joint Engineering Laboratory of Aquatic Animal Genetic Breeding and Nutrition (Zhejiang), Zhejiang Provincial Key Laboratory of Aquatic Resources Conservation and Development, Key Laboratory of Aquatic Animal Genetic Breeding and Nutrition of Chinese Academy of Fishery Sciences, 759 Erhuan East Road, Huzhou, Zhejiang 313000, PR China.
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8
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Cambiaghi V, Vitali E, Morone D, Peverelli E, Spada A, Mantovani G, Lania AG. Identification of human somatostatin receptor 2 domains involved in internalization and signaling in QGP-1 pancreatic neuroendocrine tumor cell line. Endocrine 2017; 56:146-157. [PMID: 27406390 DOI: 10.1007/s12020-016-1026-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 06/16/2016] [Indexed: 01/14/2023]
Abstract
Somatostatin exerts inhibitory effects on hormone secretion and cell proliferation via five receptor subtypes (SST1-SST5), whose internalization is regulated by β-arrestins. The receptor domains involved in these effects have been only partially elucidated. The aim of the study is to characterize the molecular mechanism and determinants responsible for somatostatin receptor 2 internalization and signaling in pancreatic neuroendocrine QGP-1 cell line, focusing on the third intracellular loop and carboxyl terminal domains. We demonstrated that in cells transfected with somatostatin receptor 2 third intracellular loop mutant, no differences in β-arrestins recruitment and receptor internalization were observed after somatostatin receptor 2 activation in comparison with cells bearing wild-type somatostatin receptor 2. Conversely, the truncated somatostatin receptor 2 failed to recruit β-arrestins and to internalize after somatostatin receptor 2 agonist (BIM23120) incubation. Moreover, the inhibitory effect of BIM23120 on cell proliferation, cyclin D1 expression, P-ERK1/2 levels, apoptosis and vascular endothelial growth factor secretion was completely lost in cells transfected with either third intracellular loop or carboxyl terminal mutants. In conclusion, we demonstrated that somatostatin receptor 2 internalization requires intact carboxyl terminal while the effects of SS on cell proliferation, angiogenesis and apoptosis mediated by somatostatin receptor 2 need the integrity of both third intracellular loop and carboxyl terminal.
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Affiliation(s)
- Valeria Cambiaghi
- Laboratory of Cellular and Molecular Endocrinology, Humanitas Clinical and Research Center, Rozzano, Italy
| | - Eleonora Vitali
- Laboratory of Cellular and Molecular Endocrinology, Humanitas Clinical and Research Center, Rozzano, Italy
| | - Diego Morone
- Laboratory of Cellular and Molecular Endocrinology, Humanitas Clinical and Research Center, Rozzano, Italy
| | - Erika Peverelli
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Anna Spada
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Giovanna Mantovani
- Endocrine Unit, Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Andrea Gerardo Lania
- Endocrine Unit, Humanitas Clinical and Research Center, Rozzano, Italy.
- Humanitas University, School of Medicine, Rozzano, Italy.
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9
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War SA, Kim B, Kumar U. Human somatostatin receptor-3 distinctively induces apoptosis in MCF-7 and cell cycle arrest in MDA-MB-231 breast cancer cells. Mol Cell Endocrinol 2015; 413:129-44. [PMID: 26112183 DOI: 10.1016/j.mce.2015.06.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/12/2015] [Accepted: 06/17/2015] [Indexed: 12/29/2022]
Abstract
Somatostatin (SST) mediates cytostatic and pro-apoptotic effects through five somatostatin receptors (SSTR1-5). The modest clinical benefits of SST analogs in cancers of different origin such as breast cancer are attributed to diminished SSTRs expression at tumor sites. In the present study, SSTR3 was overexpressed in MCF-7 and MDA-MB-231, and analyzed for downstream signaling molecules associated with cytostatic and cytotoxic effect. Cells overexpressing SSTR3 displayed inhibition of EGF induced proliferation and enhanced antiproliferative effect of SSTR3-specific agonist in comparison to non-transfected cells. SSTR3 overexpression in MCF-7 cells (R3-MCF-7) constitutively enhanced TUNEL staining, PARP-1 and p27(Kip1) expression suggesting apoptosis and cell-cycle arrest. Conversely, R3-MB-231 cells with SSTR3 overexpression exerted cytostatic and were devoid of any cytotoxic effects. The expression of PTP-1C and the status of ERK1/2, p38 and PI3K phosphorylation was modulated in a cell-specific manner. These findings provide new insights in understanding the antiproliferative role of SSTR3 in breast tumor biology.
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Affiliation(s)
- Sajad A War
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Brian Kim
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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Abstract
OBJECTIVES Although the somatostatin analog octreotide (OCT) has been used for uncontrollable insulinoma, the mechanism involved is still unknown. The aim of this study was to elucidate the therapeutic effect of OCT for insulinoma. METHODS Mouse insulinoma cell line MIN6 cells were cultured with OCT to clarify its antiproliferative effects, the expression of somatostatin receptor subtypes, cell cycle, p27 expression, and cdc2 kinase activity. The changes of the messenger RNA expression profiles were examined by microarray analysis. Intraperitoneal OCT treatment was given to insulinoma model IT6 mice for 4 weeks. RESULTS MIN6 cells expressed somatostatin receptor 2A, 3, and 5 under the OCT treatment. Octreotide showed a dose-dependent antiproliferative effect on MIN6 cells but not on the other cell lines. p27 expression and cdc2 kinase activity in MIN6 cells became prominent with OCT treatment. At the messenger RNA level, several molecules in the mitogen-activated protein kinase signaling pathway were downregulated. The sizes of the individual tumors tended to be smaller in the OCT-treated group. p27 expression was seen in the tumor tissue, but no apoptotic marker was detected. CONCLUSION Octreotide acted through a cytostatic mechanism and could be an effective therapy for insulinoma.
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11
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Riaz H, Liang A, Khan MK, Dong P, Han L, Shahzad M, Chong Z, Ahmad S, Hua G, Yang L. Somatostatin and its receptors: functional regulation in the development of mice Sertoli cells. J Steroid Biochem Mol Biol 2013; 138:257-66. [PMID: 23831358 DOI: 10.1016/j.jsbmb.2013.06.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 06/13/2013] [Accepted: 06/17/2013] [Indexed: 01/02/2023]
Abstract
Recently, Sertoli cells have been ascertained as the target for the regulatory peptide somatostatin (SST). Therefore, the present study investigated the expression of somatostatin receptors, their age-related alterations and homologous regulation by in vitro treatment with SRIF14 on mice Sertoli cells; furthermore, it dealt with SRIF14 action on growth progression, apoptotic activity and related gene expressions in these cells. We found that mice Sertoli cells expressed all SST1-5 receptors with differential intensities. Age-related real-time PCR of all somatostatin receptors identified abundance of SSTR2 and SSTR5 mRNA level during Sertoli cell developmental period. Furthermore, higher level of these two receptors was independent of SRIF14, as treatment with SRIF14 failed to induce both receptor expressions when compared with control. Somatostatin treatment elicited a dose-dependent decrease in forskolin stimulated cAMP production. Low (100pM and 10nM) and high dosage (1μM) groups of SRIF14 significantly promoted apoptosis, while all treatment groups led to dose dependent cessation (P<0.05) of G1 phase of cell cycle as further validated by increase in casp3, decrease in bcl2, elevation of P21 (all by western blot) and decrease in Igf1 expressions, similarly, SST treatment caused a dose dependent suppression in the mRNA level of kitl gene, which is important in the regulation of spermatogenesis. These findings suggest that somatostatin and its receptors (SSTR2 and SSTR5) are important markers in the regulation and development of Sertoli cell; furthermore, it portrays physiological inhibitory role in Sertoli cell development by inducing apoptosis and cell cycle arrest.
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Affiliation(s)
- Hasan Riaz
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Education Ministry of China, Huazhong Agricultural University, Wuhan, Hubei 430070, People's Republic of China
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12
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The Concept of Divergent Targeting through the Activation and Inhibition of Receptors as a Novel Chemotherapeutic Strategy: Signaling Responses to Strong DNA-Reactive Combinatorial Mimicries. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:282050. [PMID: 22523681 PMCID: PMC3317223 DOI: 10.1155/2012/282050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Accepted: 12/13/2011] [Indexed: 10/28/2022]
Abstract
Recently, we reported the combination of multitargeted ErbB1 inhibitor-DNA damage combi-molecules with OCT in order to downregulate ErbB1 and activate SSTRs. Absence of translation to cell kill was believed to be partially due to insufficient ErbB1 blockage and DNA damage. In this study, we evaluated cell response to molecules that damage DNA more aggressively and induce stronger attenuation of ErbB1 phosphorylation. We used three cell lines expressing low levels (U87MG) or transfected to overexpress wildtype (U87/EGFR) or a variant (U87/EGFRvIII) of ErbB1. The results showed that Iressa ± HN2 and the combi-molecules, ZRBA4 and ZR2003, significantly blocked ErbB1 phosphorylation in U87MG cells. Addition of OCT significantly altered cell cycle distribution. Analysis of the DNA damage response pathway revealed strong upregulation of p53 by HN2 and the combi-molecules. Apoptosis was only induced by a 48 h exposure to HN2. All other treatments resulted in cell necrosis. This is in agreement with Akt-Bad pathway activation and survivin upregulation. Despite strong DNA damaging properties and downregulation of ErbB1 phosphorylation by these molecules, the strongest effect of SSTR activation was on cell cycle distribution. Therefore, any enhanced antiproliferative effects of combining ErbB1 inhibition with SSTR activation must be addressed in the context of cell cycle arrest.
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13
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Ciganoka D, Balcere I, Kapa I, Peculis R, Valtere A, Nikitina-Zake L, Lase I, Schiöth HB, Pirags V, Klovins J. Identification of somatostatin receptor type 5 gene polymorphisms associated with acromegaly. Eur J Endocrinol 2011; 165:517-25. [PMID: 21810856 PMCID: PMC3178914 DOI: 10.1530/eje-11-0416] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE The aim of this study was to characterize the genetic variance of somatostatin receptor 5 (SSTR5) and investigate the possible correlation of such variants with acromegaly risk and different disease characteristics. DESIGN AND METHODS The SSTR5 gene coding region and 2000 bp upstream region was sequenced in 48 patients with acromegaly and 96 control subjects. Further, three single nucleotide polymorphisms (SNPs) were analyzed in the same group of acromegaly patients and in an additional group of 475 age- and sex-matched controls. RESULTS In total, 19 SNPs were identified in the SSTR5 gene locus by direct sequencing. Three SNPs (rs34037914, rs169068, and rs642249) were significantly associated with the presence of acromegaly using the initial controls. The allele frequencies were significantly (P<0.01) different between the acromegaly patients and the additional large control group. rs34037914 and rs642249 remained significantly associated with acromegaly after Bonferroni correction and permutation tests (odds ratio (OR)=3.38; 95% confidence interval (CI), 1.78-6.42; P=0.00016 and OR=2.41; 95% CI, 1.41-4.13; P=0.0014 respectively). Haplotype reconstruction revealed two possible risk haplotypes determined by rs34037914 (633T) and rs642249 (1044A) alleles. Both haplotypes were found in significantly higher frequency in acromegaly patients compared with controls (P<0.001). In addition, the 663T allele was significantly associated with a younger age of acromegaly diagnosis (unstandardized regression coefficient β=-10.4; P=0.002), increased body mass index (β=4.1; P=0.004), higher number of adenoma resection (P<0.001) and lack of observable tumor shrinkage after somatostatin analog treatment (P=0.014). CONCLUSIONS Our results demonstrate a previously undetected strong association of two SSTR5 SNPs with acromegaly. The data also suggest a possible involvement of SSTR5 variants in decreased suppression of GH production and increased tumor proliferation.
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Affiliation(s)
- Darja Ciganoka
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
| | - Inga Balcere
- Department of EndocrinologyPauls Stradins Clinical University HospitalPilsonu Street 13, LV1002, RigaLatvia
| | - Ivo Kapa
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
| | - Raitis Peculis
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
| | - Andra Valtere
- Department of EndocrinologyRiga Eastern Clinical University HospitalRiga, Hipokrata Street, LV1038Latvia
| | - Liene Nikitina-Zake
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
| | - Ieva Lase
- Department of EndocrinologyPauls Stradins Clinical University HospitalPilsonu Street 13, LV1002, RigaLatvia
| | - Helgi B Schiöth
- Department of Neuroscience, Functional PharmacologyUppsala University, BMCPO Box 593, 751 24, UppsalaSweden
| | - Valdis Pirags
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
- Department of EndocrinologyPauls Stradins Clinical University HospitalPilsonu Street 13, LV1002, RigaLatvia
- Faculty of MedicineUniversity of LatviaSarlotes Street 1a, LV1001, RigaLatvia
| | - Janis Klovins
- Latvian Biomedical Research and Study CentreRatsupites Street 1, LV-1067, RigaLatvia
- Department of Neuroscience, Functional PharmacologyUppsala University, BMCPO Box 593, 751 24, UppsalaSweden
- (Correspondence should be addressed to J Klovins at Latvian Biomedical Research and Study Centre; )
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14
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Zhou G, Gingras MC, Liu SH, Li D, Li Z, Catania RL, Stehling KM, Li M, Paganelli G, Gibbs RA, DeMayo F, Fisher WE, Brunicardi FC. The hypofunctional effect of P335L single nucleotide polymorphism on SSTR5 function. World J Surg 2011; 35:1715-24. [PMID: 21249361 PMCID: PMC4137969 DOI: 10.1007/s00268-010-0939-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Somatostatin receptor subtype 5 (SSTR5) mediates the inhibitory effect of somatostatin on insulin expression/secretion and cell proliferation. A number of single nucleotide polymorphisms (SNPs) of SSTR5 have been identified, including P335L, a nonsynonymous SNP located in the protein C-terminal region and encrypted by the codon CCG (proline) or the codon CTG (leucine). In the present study we sought to determine the distribution of the SSTR5 P335L SNP in a cohort of pancreatic cancer patients and whether the P335L SNP affected cellular function of SSTR5 in human pancreatic cancer. METHODS The P335L germline genotype of 246 patients with pancreatic cancer (213 Caucasians, 16 Hispanics, and 17 African Americans) and 17 human pancreatic cell lines was determined with the TaqMan SNP Genotyping assay. Human SSTR5 leucine variant (L335) was generated by performing site-directed mutagenesis using SSTR5 proline variant (P335) as a template. Transient transfections were performed in HEK293, Mia PaCa-2, and β-TC-6 cells using Lipofectamine 2000. The expression of SSTR5 L335 was determined with a mouse monoclonal anti-SSTR5 L335 antibody generated in our laboratory. The cell proliferation rate was measured by performing MTS assays. Insulin concentration was measured by performing ELISA assays. RESULTS Genotyping of the patients' blood indicated that the frequency of the T allele (CT and TT genotypes) in codon 335 of SSTR5 in Caucasians, Hispanics, and African Americans was 52, 69, and 35%, respectively, which was race-dependent. Statistical analysis indicated that association between the frequency of the T allele and the existence of pancreatic cancer in each race missed significance perhaps due to limited sample size. In 17 tested human pancreatic cancer cell lines, 5 (Capan-2, HPAF-II, Panc03.27, Panc-1, and -3) were homozygous (TT genotype) and 9, including Mia PaCa-2, were heterozygous (CT genotype). Overexpression of SSTR5 L335 in Mia PaCa-2 cells enhanced cell proliferation compared to overexpression of SSTR5 P335. Overexpression of SSTR5 P335 enhanced the inhibitory effect of SSTR5 agonist RPL-1980 on cell proliferation of Mia PaCa-2 cells and glucose-stimulated insulin secretion from mouse insulinoma cells, while overexpression of SSTR5 L335 blocked the inhibitory effect of RPL-1980. Overexpression of SSTR5 L335 enhanced PDX-1 expression in Mia PaCa-2 cells. A specific monoclonal antibody was generated to detect SSTR5 P335L. CONCLUSION SSTR5 P335L SNP widely exists in the human population, in patients with pancreatic cancer, and is race-dependent. The SNP is also present in selected human pancreatic cancer cell lines. In contrast to SSTR5 P335, overexpression of the SSTR5 L335 variant resulted in cellular proliferation and PDX-1 overexpression in human pancreatic cancer cells. Its overexpression blocked the inhibitory effect of an SSTR5-specific analog on human pancreatic cancer cell proliferation and on glucose-stimulated insulin secretion from mouse insulinoma cells. These data suggest that SSTR5 P335L is a hypofunctional protein with a potentially harmful effect on function, as well as potential latent effect, and therefore it could affect the clinical response to somatostatin analog therapy for patients with pancreatic cancer.
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Affiliation(s)
- Guisheng Zhou
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Marie-Claude Gingras
- Human Genome Sequencing Center; Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Shi-He Liu
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Donghui Li
- Departments of Gastrointestinal Medical and Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas, 77030, USA
| | - Zhijun Li
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Robbi L. Catania
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Kelly M. Stehling
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Min Li
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Giovanni Paganelli
- Division of Nuclear Medicine, European Institute of Oncology, Via Ripamonti 435 20141, Milan, Italy
| | - Richard A Gibbs
- Human Genome Sequencing Center; Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - Franco DeMayo
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - William E. Fisher
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
| | - F. Charles Brunicardi
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030,USA
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15
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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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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: 1.5] [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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Profiling of somatostatin receptor subtype expression by quantitative PCR and correlation with clinicopathological features in pancreatic endocrine tumors. Pancreas 2010; 39:1147-54. [PMID: 20717067 DOI: 10.1097/mpa.0b013e3181e78120] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES Pancreatic endocrine tumor (PET) presents variable clinical features. Five subtypes of somatostatin receptor (SSTR) are involved in hormone secretion and cell proliferation. In this paper, we explore the correlation between the SSTR subtype messenger RNA (mRNA) expression and clinicopathological features of PET. METHODS Twenty-one cases of PET and 5 cases of pancreatic adenocarcinomas (AC) were studied. Using total RNA extracted from paraffin sections and fresh tissues, SSTR subtype mRNA was quantified by real-time polymerase chain reaction. The hormones and MIB1 index were examined using immunohistochemical techniques. RESULTS The mRNA levels of SSTR1, SSTR2, SSTR3, and SSTR5 were high in PET compared with AC, whereas the expression of SSTR4 was low in PET and AC. Levels of each subtype did not vary with histological grades. Somatostatin receptor 2 levels in functioning tumors were slightly low compared with nonfunctioning tumors. Four distinct groups of PET were identified by hierarchical cluster analysis, and two of these groups showed reduced SSTR5 with elevation of MIB1 index. CONCLUSIONS The study showed a heterogeneous expression profile of SSTR subtype mRNA and the association of reduction in SSTR5 with high proliferative activity. Such profiling of SSTR subtypes may provide useful information on tumor biology and treatment of PET.
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Abstract
Neuroendocrine Tumors — Laboratory DiagnosisNeuroendocrine tumors (NETs) are a heterogeneous group of neoplasms originating from endocrine cells, which are characterized by the presence of secretory granules as well as the ability to produce biogenic amines and polypeptide hormones. These tumors originate from endocrine glands such as the adrenal medulla, the pituitary, and the parathyroids, as well as endocrine islets within the thyroid or the pancreas, and dispersed endocrine cells in the respiratory and gastrointestinal tract. The clinical behavior of NETs is extremely variable; they may be functioning or not functioning, ranging from very slow-growing tumors (well-differentiated NETs), which are the majority, to highly aggressive and very malignant tumors (poorly differentiated NETs). Classically, NETs of the gastrointestinal tract are classified into 2 main groups: (1) carcinoids and (2) endocrine pancreatic tumors (EPTs). Most neuroendocrine tumors produce and secrete a multitude of peptide hormones and amines. Some of these substances cause a specific clinical syndrome: carcinoid, Zollinger-Ellison, hyperglycemic, glucagonoma and WDHA syndrome. Specific markers for these syndromes are basal and/or stimulated levels of urinary 5-HIAA, serum or plasma gastrin, insulin, glucagon and vasoactive intestinal polypeptide, respectively. Some carcinoid tumors and about one third of endocrine pancreatic tumors do not present any clinical symptoms and are called ‘nonfunctioning’ tumors. Therefore, general tumor markers such as chromogranin A, pancreatic polypeptide, serum neuron-specific enolase and subunits of glycoprotein hormones have been used for screening purposes in patients without distinct clinical hormone-related symptoms. Among these general tumor markers chromogranin A, although its precise function is not yet established, has been shown to be a very sensitive and specific serum marker for various types of neuroendocrine tumors. This is because it may also be elevated in many cases of less well-differentiated tumors of neuroendocrine origin that do not secrete known hormones. At the moment, chromogranin A is considered the best general neuroendocrine serum or plasma marker available both for diagnosis and therapeutic evaluation, and is increased in 50-100% of patients with various neuroendocrine tumors. Chromogranin A serum or plasma levels reflect tumor load, and it may be an independent marker of prognosis in patients with midgut carcinoids.
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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: 1.1] [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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Peverelli E, Lania AG, Mantovani G, Beck-Peccoz P, Spada A. Characterization of intracellular signaling mediated by human somatostatin receptor 5: role of the DRY motif and the third intracellular loop. Endocrinology 2009; 150:3169-76. [PMID: 19342453 PMCID: PMC2703549 DOI: 10.1210/en.2008-1785] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Somatostatin (SST) exerts inhibitory effects on hormone secretion and cell proliferation by interacting with five different receptors (SST1-SST5) linked to multiple cellular effectors. The receptor structural domains involved in these effects have been only partially elucidated. The aim of the study was to investigate the molecular determinants mediating the interaction of the human SST5 with intracellular signaling in the pituitary cell line GH3, focusing on the BBXXB domain in the third intracellular loop and the DRY motif in the second intracellular loop. We analyzed the effects of the SST5 agonist BIM23206 on cAMP accumulation, intracellular calcium, GH secretion, cell proliferation, and ERK1/2 phosphorylation in cells expressing either wild-type SST5 or mutant receptors, in particular the naturally occurring mutant R240W in the BBXXB domain and the D136A and R137A mutants in the DRY motif. We found that residues D136 and R137 were critical for SST5 signaling because their substitutions abolished all the intracellular responses. Conversely, third intracellular loop mutations resulted in receptor that inhibited intracellular cAMP levels similar to the wild-type (50 +/- 9 vs. 53 +/- 12% inhibition) but failed to mediate the other responses elicited by wild-type SST5, i.e. reduction of intracellular calcium levels as well as inhibition of ERK1/2. These events resulted in an absent inhibition of GH release and an impaired reduction of cell proliferation (38 +/- 7 vs. 76 +/- 6% inhibition in wild type, P < 0.05). These data indicate that different regions of SST5 are required for the activation of different signaling pathways.
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Affiliation(s)
- Erika Peverelli
- Department of Medical Sciences, Fondazione Ospedale Maggiore Policlinico Mangiagalli e Regina Elena IRCCS, University of Milan, 20122 Milan, Italy
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Barbieri F, Pattarozzi A, Gatti M, Porcile C, Bajetto A, Ferrari A, Culler MD, Florio T. Somatostatin receptors 1, 2, and 5 cooperate in the somatostatin inhibition of C6 glioma cell proliferation in vitro via a phosphotyrosine phosphatase-eta-dependent inhibition of extracellularly regulated kinase-1/2. Endocrinology 2008; 149:4736-46. [PMID: 18566118 DOI: 10.1210/en.2007-1762] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Somatostatin inhibits cell proliferation through the activation of five receptors (SSTR1-5) expressed in normal and cancer cells. We analyzed the role of individual SSTRs in the antiproliferative activity of somatostatin in C6 rat glioma cells. Somatostatin dose-dependently inhibited C6 proliferation, an effect mimicked, with different efficacy or potency, by BIM-23745, BIM-23120, BIM-23206 (agonists for SSTR1, -2, and -5) and octreotide. The activation of SSTR3 was ineffective, although all SSTRs are functionally active, as demonstrated by the inhibition of cAMP production. All SSTRs induced cytostatic effects through the activation of the phosphotyrosine phosphatase PTPeta and the inhibition of ERK1/2. For possible synergism between SSTR subtypes, we tested the effects of the combined treatment with two agonists (SSTR1+2 or SSTR2+5) or bifunctional compounds. The simultaneous activation of SSTR1 and SSTR2 slightly increased the efficacy of the individual compounds with an IC50 in between the single receptor activation. SSTR2+5 activation displayed a pattern of response superimposable to that of the SSTR5 agonist alone (low potency and higher efficacy, as compared with BIM-23120). The simultaneous activation of SSTR1, -2, and -5 resulted in a response similar to somatostatin. In conclusion, the cytostatic effects of somatostatin in C6 cells are mediated by the SSTR1, -2, and -5 through the same intracellular pathway: activation of PTPeta and inhibition of ERK1/2 activity. Somatostatin is more effective than the individual agonists. The combined activation of SSTR1 and -2 shows a partial synergism as far as antiproliferative activity, whereas SSTR2 and -5 activation results in a response resembling the SSTR5 effects.
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Affiliation(s)
- Federica Barbieri
- Laboratory pf Pharmacology, Department of Oncology, Biology, and Genetics, University of Genova, Viale Benedetto XV, 2, 16132 Genova, Italy
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The Effect of Transforming Growth Factor β on Human Neuroendocrine Tumor BON Cell Proliferation and Differentiation Is Mediated through Somatostatin Signaling. Mol Cancer Res 2008; 6:1029-42. [DOI: 10.1158/1541-7786.mcr-07-2073] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Alexandraki KI, Grossman AB. Pituitary-targeted medical therapy of Cushing's disease. Expert Opin Investig Drugs 2008; 17:669-77. [PMID: 18447593 DOI: 10.1517/13543784.17.5.669] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The goals of ideal medical therapy for Cushing's disease should be to target the aetiology of the disorder, as is the case for surgery, which is the current 'gold standard' treatment. However, no effective drug that directly and reliably targets the adrenocorticotropin-secreting pituitary adenoma has yet been found. OBJECTIVE To summarise pituitary-targeted medical treatment of Cushing's disease. METHODS Compounds with neuromodulatory properties and ligands of different nuclear hormone receptors involved in hypothalamo-pituitary regulation have been investigated. RESULTS The somatostatin analogue pasireotide and the dopamine agonist cabergoline, as well as their combination, show some therapeutic promise in the medical therapy of Cushing's disease. Other treatments such as retinoic acid analogues look promising and may be a possible option for further investigation. No other medical therapies seem to be reliably effective currently. CONCLUSION Since a percentage of patients treated with surgery are not cured, or improve and subsequently relapse, there is an urgent need for effective medical therapies for this disorder. At present, only cabergoline and pasireotide are under active investigation.
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Affiliation(s)
- Krystallenia I Alexandraki
- Professor of Neuroendocrinology St. Bartholomew's Hospital, Ashley Grossman FMedSci, London EC1A 7BE, UK
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Condon LT, Stafford ND, Bedford KJ, MacDonald AW, Atkin SL. The expression of somatostatin receptors 3, 4 and 5 in laryngeal pathology. Eur Arch Otorhinolaryngol 2007; 265 Suppl 1:S63-7. [DOI: 10.1007/s00405-007-0539-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 11/05/2007] [Indexed: 11/24/2022]
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Kumar U. Colocalization of somatostatin receptor subtypes (SSTR1-5) with somatostatin, NADPH-diaphorase (NADPH-d), and tyrosine hydroxylase in the rat hypothalamus. J Comp Neurol 2007; 504:185-205. [PMID: 17626271 DOI: 10.1002/cne.21444] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The hypothalamus is a major site of somatostatin (SST) production and action. SST is synthesized in several hypothalamic nuclei and involved in a variety of functions. Using SST receptor (SSTR)-specific antibodies, we localized SSTR subtypes in the rat hypothalamus. In addition, we also demonstrated SSTRs colocalization with SST, NADPH-diaphorase (NADPH-d), and tyrosine hydroxylase (TH). SSTR1 is strongly localized in neurons in all major hypothalamic nuclei as well as in nerve fibers in the zona externa of the median eminence and the ependyma of the third ventricle. SSTR2 is also well expressed in most regions but with a relatively lower abundance in comparison to SSTR1. In contrast, SSTR3 is localized primarily in the paraventricular nucleus, dorsomedial hypothalamic nucleus, arcuate nucleus, and median eminence. SSTR4-like immunoreactivity is mainly confined to the arcuate nucleus, ventromedial hypothalamic nucleus, median eminence, and ependymal cells of third ventricle, with the rare SSTR4-positive neuron in the paraventricular nucleus. SSTR5 is the least expressed subtype occurring only in few cells in the inner layer of the median eminence. Overall, SSTR1 is the predominant subtype, followed by SSTR2, 4, 3, and 5. Combined immunofluorescence, immunocytochemistry, and histochemistry were used to demonstrate SSTRs colocalization with SST, TH, and NADPH-d. SSTRs colocalization with SST, TH, and NADPH-d displays in a region and receptor specificity. Colocalization of SST and NADPH-d with SSTRs in hypothalamic regions was similar, suggesting that SST and NADPH-d producing cells are same. In contrast, TH was selectively coexpressed with SSTRs in the hypothalamus in a receptor-specific manner. Taken together, these data suggest that SSTRs may interact with NADPH-d and TH to exert a physiological role in concert within the hypothalamus.
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Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of British Columbia, Vancouver, Canada.
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Grzela T, Bialoszewska A, Brawura-Biskupski-Samaha R. Nuclear medicine in the treatment of neuroendocrine tumours--problems and perspectives. Eur J Nucl Med Mol Imaging 2006; 34:444-7. [PMID: 17136539 DOI: 10.1007/s00259-006-0300-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Radford IR, Lobachevsky PN. An enteroendocrine cell-based model for a quiescent intestinal stem cell niche. Cell Prolif 2006; 39:403-14. [PMID: 16987141 PMCID: PMC6496364 DOI: 10.1111/j.1365-2184.2006.00396.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have shown that the kinetics of conversion of intestinal crypt cell populations to a partially or wholly mutant phenotype are consistent with a model in which each crypt contains an infrequently dividing 'deep' stem cell that is the progenitor of several more frequently dividing 'proximate' stem cells. An assumption of our model is that each deep stem cell exists in a growth inhibitory niche. We have used information from the literature to develop a model for a quiescent intestinal stem cell niche. This niche is postulated to be primarily defined by an enteroendocrine cell type that maintains stem cell quiescence by secretion of growth inhibitory peptides such as somatostatin and guanylin/uroguanylin. Consistent with this model, there is evidence that the proteins postulated as defining a growth-inhibitory stem cell niche can act as intestinal tumour suppressors. Confirmation that a growth-inhibitory niche does exist would have important implications for our understanding of intestinal homeostasis and tumorigenesis.
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Abstract
The development of the endocrine pancreas is regulated by numerous transcription and growth factors. Somatostatin (SST) is present in many tissues and acts as a neurotransmitter and autocrine/paracrine/endocrine regulator in response to ions, nutrients, peptides, and hormones as well as neurotransmitters. In the pancreas, there is evidence that SST acts an inhibitory paracrine regulator of hormone secretion. Somatostatin receptors (SSTRs) are a family of 5 transmembrane G protein-coupled receptors, which are widely expressed in mammals including humans. SSTRs regulate multiple downstream signal transduction pathways that mediate inhibitory effects. These receptors also exhibit age- and tissue-specific expression patterns. Interactions of SST and SSTRs are not only important during normal pancreas development, but have also been implicated in many pancreatic diseases such as diabetes mellitus and pancreatic cancer. In this review article, we use evidence from recently published animal studies to present the critical roles of SST and SSTRs proteins in the development of the endocrine pancreas.
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Affiliation(s)
- Nikiforos Ballian
- The Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA
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Filopanti M, Ronchi C, Ballarè E, Bondioni S, Lania AG, Losa M, Gelmini S, Peri A, Orlando C, Beck-Peccoz P, Spada A. Analysis of somatostatin receptors 2 and 5 polymorphisms in patients with acromegaly. J Clin Endocrinol Metab 2005; 90:4824-8. [PMID: 15914528 DOI: 10.1210/jc.2005-0132] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVE The aim of the study was to investigate the possible correlation of single nucleotide polymorphisms in somatostatin receptor (SSTR)2 and SSTR5 genes with the responsiveness to somatostatin analogs in a cohort of acromegalic patients. STUDY DESIGN Three single nucleotide polymorphisms (a-83 g, c-57 g, and t80c) of SSTR2 and three (t-461c, c325t, and c1004t) of SSTR5 were analyzed in 66 acromegalic patients with different responsiveness to somatostatin analogs and 66 healthy controls. RESULTS Allele frequencies in patients and controls were similar. No association between SSTR2 genotypes and GH and IGF-I levels was found. When considering SSTR5 variants, patients homozygous or heterozygous for the substitution c1004 (P+) showed basal IGF-I levels significantly lower than patients homozygous for 1004t (P-). Moreover, serum GH levels were lower in patients with P+/T- haplotype (having c1004 allele and no t-461 allele) than in those with P-/T+. No correlation between SSTR2 and SSTR5 genotypes, responsiveness to somatostatin therapy, and mRNA expression in the removed adenomas (n = 10) was found. CONCLUSIONS These data suggest a role for SSTR5 t-461c and c1004t alleles in influencing GH and IGF-I levels in patients with acromegaly, whereas SSTR2 and SSTR5 variants seem to have a minor role in determining the responsiveness to somatostatin analogs.
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Affiliation(s)
- M Filopanti
- Institute of Endocrine Sciences, University of Milan, Ospedale Maggiore Policlinico Mangiagalli e Regina Elena, Istituto di Ricovero e Cura a Curattere Scientifico, Milan, Italy
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30
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Kumar U, Grigorakis SI, Watt HL, Sasi R, Snell L, Watson P, Chaudhari S. Somatostatin receptors in primary human breast cancer: quantitative analysis of mRNA for subtypes 1–5 and correlation with receptor protein expression and tumor pathology. Breast Cancer Res Treat 2005; 92:175-86. [PMID: 15986128 DOI: 10.1007/s10549-005-2414-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Somatostatin receptors (SSTRs) have been identified in most hormone-producing tumors as well as in breast cancer. In the present study, we determined SSTR1-5 expression in primary ductal NOS breast tumors through semi-quantitative RT-PCR and immunocytochemistry. The results from the analysis of 98 samples were correlated with several key histological markers and receptor expression. All five SSTR subtypes are variably expressed at the mRNA level in breast tumors with 91% of samples showing SSTR1, 98% SSTR2, 96% SSTR3, 76% SSTR4, and 54% SSTR5. SSTR1-5 are localized to both tumor cells and the surrounding peritumoral regions as detected by immunocytochemistry. Levels of SSTR mRNA, when corrected for beta-actin levels, were highest for SSTR3 followed by SSTR1, SSTR2, SSTR5, and SSTR4. Furthermore, there was good correlation between mRNA and protein expression with 84% for SSTR1, 79% for SSTR2, 89% for SSTR3, 68% for SSTR4, 68% for SSTR5, and 78% for all five receptors. SSTR1, 2 and 4 were correlated with ER levels whereas SSTR2 showed an additional correlation with PR levels. These correlations were independent of patient age and histological grade. Moreover, using immunocytochemistry, blood vessels exhibited receptor-specific localization for SSTR2 and SSTR5. Our results indicate significant correlations between mRNA and protein expression along with receptor-specific correlations with histological markers as well as ER and PR levels. Differential distribution of SSTR subtypes in tumors and receptor-specific expression in vascular structures may be considered as a novel diagnosis for breast tumors with receptor subtype agonists.
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MESH Headings
- Adult
- Aged
- Biomarkers, Tumor/metabolism
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Carcinoma, Ductal, Breast/genetics
- Carcinoma, Ductal, Breast/pathology
- Female
- Gene Expression
- Humans
- Immunohistochemistry
- In Vitro Techniques
- Middle Aged
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- RNA, Neoplasm/analysis
- Receptors, Estrogen/metabolism
- Receptors, Progesterone/metabolism
- Receptors, Somatostatin/genetics
- Receptors, Somatostatin/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- U Kumar
- Fraser Laboratories For Diabetes Research, Department of Medicine, McGill University, Royal Victoria Hospital, 687 Pine Avenue West, H3A 1A1 Montreal, Quebec, Canada.
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Madeo M, Giusi G, Aló R, Facciolo RM, Carelli A, Canonaco M. Different somatostatin receptor subtypes are operating in the brain of the teleost fish,Coris julis. ACTA ACUST UNITED AC 2005; 303:406-13. [PMID: 15828016 DOI: 10.1002/jez.a.184] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Characterization of somatostatinergic (sst) neuronal activity through the application of nonpeptidyl agonists L-779,976 and L-817,818 which are highly specific for the sst receptors (sstr) sstr(2) and sstr(5), respectively, shows for the first time that sstr2, 5-like subtypes are the two major sstr subtypes operating in the brain of the teleost sea wrasse, Coris julis. A somewhat high but heterogeneous distribution pattern (> 30 < 180 fmol/mg wet tissue weight) of neurons expressing sstr2, 5 was reported in the different diencephalic regions plus in mesencephalon and telencephalon while low values were obtained in the cerebellum. Application of the above nonpeptidyl agonists permitted us to identify sstr2-like as the predominant subtype in telencephalic areas such as the entopeduncular nucleus (E) and postcommissural nucleus of the ventral telencephalon (Vp) as well as in hypothalamic and thalamic areas. At the same time high levels of neurons expressing sstr5-like, that greatly overlap those of sstr2-like in the diencephalic areas such as the anteroventral part of the preoptic nucleus (NPOav), the dorsal habenular nucleus (NHd) and the ventrolateral thalamic nucleus (VL), indicate that sstr2-like is very likely not the only sstr subtype acting in this fish brain. The predominance of sstr5-like in other brain areas is confirmed by the high quantities of this subtype in mesencephalic areas such as the torus longitudinalis (TLo). Overall, the discriminately differing densities of neurons expressing both subtypes seem to point to this system as a key molecular basis accounting for the distinct neurophysiological and behavioral sst-dependent activities in Coris julis.
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Affiliation(s)
- Maria Madeo
- Comparative NeuroAnatomy Laboratory, Ecology Dept., University of Calabria, 87030 Rende (Cosenza), Italy
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Abstract
Somatostatin (SST) peptide is produced by various SST-secreting cells throughout the body and acts as a neurotransmitter or paracrine/autocrine regulator in response to ions, nutrients, peptides hormones and neurotransmitters. SST is also widely distributed in the periphery to regulate the inflammatory and immune cells in response to hormones, growth factors, cytokines and other secretive molecules. SST peptides are considered the most important physiologic regulator of the islet cell, gastrointestinal cell and immune cell functions, and the importance of SST production levels has been implicated in several diseases including diabetes. The expression of SST receptors has also been found in T lymphocytes and primary immunologic organs. Interaction of SST and its receptors is also involved in T-cell proliferation and thymocyte selection. SSTR gene-ablated mice developed diabetes with morphologic, physiologic and immunologic alterations in the endocrine pancreas. Increased levels of mononuclear cell infiltration of the islets are associated with the increased levels of antigen-presenting cells located in the islets and peripancreatic lymph nodes. Increased levels of SST were also found in antigen-presenting cells and are associated with a significant increase of CD8 expression levels on CD4(+)/CD8(+) immature thymocytes. These findings highlight the crucial role of this neuroendocrine peptide and its receptors in regulating autoimmune functions.
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Affiliation(s)
- Xaio-Ping Wang
- The Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA.
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Filopanti M, Ballarè E, Lania AG, Bondioni S, Verga U, Locatelli M, Zavanone LM, Losa M, Gelmini S, Peri A, Orlando C, Beck-Peccoz P, Spada A. Loss of heterozygosity at the SS receptor type 5 locus in human GH- and TSH-secreting pituitary adenomas. J Endocrinol Invest 2004; 27:937-42. [PMID: 15762041 DOI: 10.1007/bf03347536] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
SS receptor types 2 and 5 (sst2 and sst5) are involved in the control of secretion and proliferation of normal and tumoral somatotrophs and thyrotrophs. The mechanisms leading to reduced responsiveness to SS analogues in patients with pituitary tumors are poorly understood. The aim of the study was to verify the possible loss of heterozygosity (LOH) at the sst5 gene locus in somatotroph and thyrotroph adenomas by screening leukocyte and tumor DNA for two single nucleotide polymorphisms, i.e. C1004T leading to P335L change and T-461C in the 5'-upstream region. Among the 13 informative samples, 1 GH- and 1 TSH-secreting adenoma showed LOH at sst5 gene locus with the retention of Leu335 variant. By analyzing other polymorphic markers spanning from telomere to 16p13.3-13.2 boundaries, DNA deletion of at least 1 megabase was found in both tumors. LOH in thyrotroph adenoma was associated with unusual tumor aggressiveness that required a second surgery and resistance to SS analogs, while no obvious phenotype was identified in the case of the somatotroph adenoma. In conclusions, LOH at the sst5 gene locus is a rare phenomenon, occurring in about 10% of pituitary tumors, that seems to be associated with an aggressive phenotype, at least in thyrotroph adenomas. Further studies are required to confirm this association and to identify the genes, in addition to sst5, lost in these tumors.
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Affiliation(s)
- M Filopanti
- Institute of Endocrine Sciences, University of Milan, Ospedale Maggiore IRCCS, Italy
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Lahlou H, Guillermet J, Hortala M, Vernejoul F, Pyronnet S, Bousquet C, Susini C. Molecular signaling of somatostatin receptors. Ann N Y Acad Sci 2004; 1014:121-31. [PMID: 15153426 DOI: 10.1196/annals.1294.012] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Somatostatin is a neuropeptide family that is produced by neuroendocrine, inflammatory, and immune cells in response to different stimuli. Somatostatin acts as an endogenous inhibitory regulator of various cellular functions including secretions, motility, and proliferation. Its action is mediated by a family of G-protein-coupled receptors (called sst1-sst5) that are widely distributed in the brain and periphery. The five receptors bind the natural peptides with high affinity, but only sst2, sst5, and sst3 bind the short synthetic analogs used to treat acromegaly and neuroendocrine tumors. This review covers the current knowledge in somatostatin receptor biology and signaling.
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Affiliation(s)
- Hicham Lahlou
- INSERM U 531, IFR 31, CHU Rangueil, 31403 Toulouse Cedex 4, France
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Abstract
Neuroendocrine tumors (NETs) constitute a heterogeneous group of neoplasms that originate from endocrine glands such as the pituitary, the parathyroids, and the (neuroendocrine) adrenal, as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells dispersed between exocrine cells, such as endocrine cells of the digestive (gastroenteropancreatic) and respiratory tracts. Conventionally, NETs may present with a wide variety of functional or nonfunctional endocrine syndromes and may be familial and have other associated tumors. Assessment of specific or general tumor markers offers high sensitivity in establishing the diagnosis and can also have prognostic significance. Imaging modalities include endoscopic ultrasonography, computed tomography and magnetic resonance imaging, and particularly, scintigraphy with somatostatin analogs and metaiodobenzylguanidine. Successful treatment of disseminated NETs requires a multimodal approach; radical tumor surgery may be curative but is rarely possible. Well-differentiated and slow-growing gastroenteropancreatic tumors should be treated with somatostatin analogs or alpha-interferon, with chemotherapy being reserved for poorly differentiated and progressive tumors. Therapy with radionuclides may be used for tumors exhibiting uptake to a diagnostic scan, either after surgery to eradicate microscopic residual disease or later if conventional treatment or biotherapy fails. Maintenance of the quality of life should be a priority, particularly because patients with disseminated disease may experience prolonged survival.
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Affiliation(s)
- Gregory A Kaltsas
- Department of Endocrinology, St Bartholomew's Hospital, London EC1A 7BE, United Kingdom
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Pan Q, Li DG, Lu HM, Lu LY, Wang YQ, Xu QF. Antiproliferative and proapoptotic effects of somatostatin on activated hepatic stellate cells. World J Gastroenterol 2004; 10:1015-8. [PMID: 15052685 PMCID: PMC4717091 DOI: 10.3748/wjg.v10.i7.1015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To assess the effects of somatostatin on proliferation and apoptosis of activated rat hepatic stellate cells (HSCs).
METHODS: HSCs isolated from the livers of adult Sprague-Dawley rats (weighing 400-500 g) by in situ perfusion and purified by single-step density gradient centrifugation with Nycodenz, became activated after 10 days’ cultivation. Then the apoptotic rate of HSCs treated with different doses of somatostatin for 72 h, was assayed by acridine orange/ ethidium bromide fluorescent staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, transmission electron microscopy and flow cytometry, while the proliferation of HSCs was measured by MTT assay. Furthermore, the mechanisms of somatostatin were investigated by cytodynamic analysis.
RESULTS: Somatostatin at the concentration of 10-6-10-9 mol/L could decrease the proliferative rate, and promote the apoptosis of activated rat HSCs in a dose-dependent way. Its action was most significant when the concentration reached 10-6 mol/L or 10-7 mol/L (P < 0.05-0.01). An obvious cell-cycle arrest (G0/G1 arrest) was the important way for somatostatin to exert its action.
CONCLUSION: Antiproliferative and proapoptotic effects of low-dose somatostatin on activated rat HSCs can be obtained. These findings reveal its potential antifibrotic action.
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Affiliation(s)
- Qin Pan
- Department of Gastroenterology, Shanghai Second Medical University, Xinhua Hospital, 1665 KongJiang Rd., Shanghai 200092, China.
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Stafford ND, Condon LT, Rogers MJC, Helboe L, Crooks DA, Atkin SL. The immunohistochemical localisation of somatostatin receptors 1, 2, 3, and 5 in acoustic neuromas. J Clin Pathol 2004; 57:168-71. [PMID: 14747443 PMCID: PMC1770210 DOI: 10.1136/jcp.2003.007260] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIMS Acoustic neuroma is a benign tumour, which develops through an overproliferation of Schwann cells along the vestibular nerve. Somatostatin is a naturally occurring peptide, which exerts antiproliferative and antiangiogenic effects via five membrane bound receptor subtypes. The aim of this study was to determine whether somatostatin receptor subtypes (SSTRs) 1, 2, 3, and 5 are present in acoustic neuromas. METHODS The expression of SSTRs 1, 2, 3, and 5 was studied in both the Schwann cells and blood vessels of eight acoustic neuroma specimens, by means of immunohistochemistry using novel rabbit polyclonal antibodies raised against human SSTR 1, 2, and 5 subtype specific peptides, and a commercial anti-SSTR3 antibody. RESULTS SSTR2 was the most prevalent subtype in Schwann cells (seven of eight), with intermediate expression of SSTR3 (six of eight), and lower expression of SSTRs 1 and 5 (four of eight and five of eight, respectively). There was ubiquitous vascular expression of SSTR2, with no evidence of SSTR 1, 3, or 5 expression in blood vessels. CONCLUSION SSTRs 1, 2, 3, and 5 are differentially expressed in acoustic neuromas. Somatostatin analogues may have a therapeutic role in the management of this rare and challenging condition.
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Affiliation(s)
- N D Stafford
- Department of Otolaryngology-Head and Neck Surgery, Hull Royal Infirmary, Anlaby Road, Hull HU3 2JZ, UK.
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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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Møller LN, Stidsen CE, Hartmann B, Holst JJ. Somatostatin receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2003; 1616:1-84. [PMID: 14507421 DOI: 10.1016/s0005-2736(03)00235-9] [Citation(s) in RCA: 266] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In 1972, Brazeau et al. isolated somatostatin (somatotropin release-inhibiting factor, SRIF), a cyclic polypeptide with two biologically active isoforms (SRIF-14 and SRIF-28). This event prompted the successful quest for SRIF receptors. Then, nearly a quarter of a century later, it was announced that a neuropeptide, to be named cortistatin (CST), had been cloned, bearing strong resemblance to SRIF. Evidence of special CST receptors never emerged, however. CST rather competed with both SRIF isoforms for specific receptor binding. And binding to the known subtypes with affinities in the nanomolar range, it has therefore been acknowledged to be a third endogenous ligand at SRIF receptors. This review goes through mechanisms of signal transduction, pharmacology, and anatomical distribution of SRIF receptors. Structurally, SRIF receptors belong to the superfamily of G protein-coupled (GPC) receptors, sharing the characteristic seven-transmembrane-segment (STMS) topography. Years of intensive research have resulted in cloning of five receptor subtypes (sst(1)-sst(5)), one of which is represented by two splice variants (sst(2A) and sst(2B)). The individual subtypes, functionally coupled to the effectors of signal transduction, are differentially expressed throughout the mammalian organism, with corresponding differences in physiological impact. It is evident that receptor function, from a physiological point of view, cannot simply be reduced to the accumulated operations of individual receptors. Far from being isolated functional units, receptors co-operate. The total receptor apparatus of individual cell types is composed of different-ligand receptors (e.g. SRIF and non-SRIF receptors) and co-expressed receptor subtypes (e.g. sst(2) and sst(5) receptors) in characteristic proportions. In other words, levels of individual receptor subtypes are highly cell-specific and vary with the co-expression of different-ligand receptors. However, the question is how to quantify the relative contributions of individual receptor subtypes to the integration of transduced signals, ultimately the result of collective receptor activity. The generation of knock-out (KO) mice, intended as a means to define the contributions made by individual receptor subtypes, necessarily marks but an approximation. Furthermore, we must now take into account the stunning complexity of receptor co-operation indicated by the observation of receptor homo- and heterodimerisation, let alone oligomerisation. Theoretically, this phenomenon adds a novel series of functional megareceptors/super-receptors, with varied pharmacological profiles, to the catalogue of monomeric receptor subtypes isolated and cloned in the past. SRIF analogues include both peptides and non-peptides, receptor agonists and antagonists. Relatively long half lives, as compared to those of the endogenous ligands, have been paramount from the outset. Motivated by theoretical puzzles or the shortcomings of present-day diagnostics and therapy, investigators have also aimed to produce subtype-selective analogues. Several have become available.
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Affiliation(s)
- Lars Neisig Møller
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
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N/A. N/A. Shijie Huaren Xiaohua Zazhi 2003; 11:1581-1587. [DOI: 10.11569/wcjd.v11.i10.1581] [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: 02/07/2023] Open
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Abstract
Tumor angiogenesis is the proliferation of a network of blood vessels that penetrates into cancerous growths, supplying nutrients and oxygen and removing waste products. The process of angiogenesis plays an important role in many physiological and pathological conditions. Solid tumors depend on angiogenesis for growth and metastasis in a hostile environment. In the prevascular phase, the tumor is rarely larger than 2 to 3 mm3 and may contain a million or more cells. Up to this size, tumor cells can obtain the necessary oxygen and nutrient supplies required for growth and survival by simple passive diffusion. The properties of tumors to release and induce several angiogenic and anti-angiogenic factors which play crucial roles in regulating endothelial cell (EC) proliferation, migration, apoptosis or survival, cell-cell and cell-matrix adhesion through different intracellular signaling are thought to be the essential mechanisms during tumor-induced angiogenesis. Tumor angiogenesis actually starts with tumor cells releasing molecules that send signals to surrounding normal host tissue. This signaling activates certain genes in the host tissue that, in turn, make proteins to encourage growth of new blood vessels. In this review, we focus the mechanisms of tumor-induced angiogenesis, with an emphasis on the regulatory role of several angiogenic and anti-angiogenic agents during the angiogenic process in tumors. Advances in understanding the mechanisms of tumor angiogenesis have led to the development of several most effective anti-angiogenic and anti-metastatic therapeutic agents and also have provided several techniques for the regulation of cancer's angiogenic switch. The suggestion is made that standard cytotoxic chemotherapy and angiogenesis inhibitors used in combination may produce complementary therapeutic benefits in the treatment of cancer.
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Affiliation(s)
- Manoj Kumar Gupta
- Department of Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, Hubei, China.
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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: 1.1] [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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Abstract
Since the discovery of somatostatin (SST) over three decades ago, its ubiquitous distribution and manifold functions are still being documented. SST is synthesized in the hypothalamus and transported to the anterior pituitary gland where it tonicaly inhibits GH and TSH secretion as well as being responsible for GH pulsatile release. Several internal feedback loops, sleep, exercise, and chemical agents control and influence SST release. SST also impacts the function of a wide variety of cells and organ systems throughout the body. Knowledge of the structures of the SSTs has resulted in recognition of the essential four core conserved residues responsible for their actions. The SSTs act through six separate SST cell surface receptors (SSTRs), members of the family of G protein-coupled receptors. Receptor ligand binding (SST/SSTR) results in cellular activities specific for each receptor, or receptor combinations, and their tissue/cell localization. Understanding the structure/function relationship of the SSTs and their receptors, including the internalization of SST/SSTR complexes, has facilitated the development of a variety of novel pharmacologic agents for the diagnosis and treatment of neuroendocrine tumors and unfolding new applications.
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Affiliation(s)
- Philip Barnett
- Pituitary Center, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA.
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Hofland LJ, Lamberts SWJ. The pathophysiological consequences of somatostatin receptor internalization and resistance. Endocr Rev 2003; 24:28-47. [PMID: 12588807 DOI: 10.1210/er.2000-0001] [Citation(s) in RCA: 308] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Somatostatin receptors expressed on tumor cells form the rationale for somatostatin analog treatment of patients with somatostatin receptor-positive neuroendocrine tumors. Nevertheless, although somatostatin analogs effectively control hormonal hypersecretion by GH-secreting pituitary adenomas, islet cell tumors, and carcinoid tumors, significant differences are observed among patients with respect to the efficacy of treatment. This may be related to a differential expression of somatostatin receptor subtypes among tumors. In addition, the property of somatostatin receptor subtypes to undergo agonist-induced internalization has important consequences for visualizing, as well as for therapy, of receptor-positive tumors using radioisotope- or chemotherapeutic-compound-coupled somatostatin analogs. This review covers the pathophysiological role of somatostatin receptor subtypes in determining the efficacy of treatment of patients with somatostatin receptor-positive tumors using somatostatin analogs, as well as the preclinical and clinical consequences of agonist-induced receptor internalization for somatostatin receptor-targeted radio- and chemotherapy. Herein, the development and potential role of novel somatostatin analogs is discussed.
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Affiliation(s)
- Leo J Hofland
- Department of Internal Medicine, Erasmus Medical Center, 3015 GD Rotterdam, The Netherlands.
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Fisher WE, Wu Y, Amaya F, Berger DH. Somatostatin receptor subtype 2 gene therapy inhibits pancreatic cancer in vitro. J Surg Res 2002; 105:58-64. [PMID: 12069503 DOI: 10.1006/jsre.2002.6450] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Most human pancreatic adenocarcinoma cells do not express somatostatin receptors and somatostatin does not inhibit the growth of these cancers. We have demonstrated previously that somatostatin inhibits the growth of pancreatic cancers expressing somatostatin receptor subtype 2 (SSR2) but not receptor-negative cancers. SSR2 expression may be an important tumor suppressor pathway that is lost in human pancreatic cancer. We hypothesized that SSR2 gene transfer would restore the growth inhibitory response of human pancreatic cancer to somatostatin. METHODS We created adenoviral constructs containing the SSR2 or Lac-Z gene and transfected somatostatin receptor-negative human pancreatic cancer cells (Panc-1). Presence of functional cell surface SSR2 protein was assessed by whole-cell competitive binding assays. Parental cells, Lac-Z-transfected, and SSR2-transfected cells were cultured in the presence and absence of somatostatin. The rate of cell growth was determined by direct cell counting using a hemacytometer (n = 8 wells/group). Cells were analyzed for expression of tumor suppressor proteins by Western blot. RESULTS Panc-1 cells transfected with the SSR2 transgene demonstrated high-affinity specific binding of (125)I-somatostatin at physiologic concentrations. Expression of somatostatin receptors caused 60% inhibition of cell growth compared with the Lac-Z virus-treated controls (P < 0.05 by Kruskal-Wallis/Bonferroni). There was no additional inhibition of cell proliferation with exogenous somatostatin. Furthermore, addition of somatostatin ligand antibody did not diminish the effect of SSR2 expression on cell proliferation. Western blot analysis revealed an upregulation of the cyclin-dependent kinase inhibitor p27 in the SSR2-transfected cells. CONCLUSIONS Expression of SSR2 by human pancreatic cancer causes significant slowing of cell division by a mechanism independent of somatostatin. The mechanism may involve upregulation of known tumor suppressor proteins. Restoration of SSR2 gene expression deserves further study as a potential gene therapy strategy in human pancreatic cancer.
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Affiliation(s)
- William E Fisher
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030, USA.
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Arnold R, Wied M, Behr TH. Somatostatin analogues in the treatment of endocrine tumors of the gastrointestinal tract. Expert Opin Pharmacother 2002; 3:643-56. [PMID: 12472080 DOI: 10.1517/14656566.3.6.643] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Somatostatin and its long-acting analogues have been introduced for the treatment of endocrine tumours of the gastrointestinal tract as they have been shown to effectively control symptoms resulting from excessive hormone release in patients with carcinoid, Verner-Morrison and glucagonoma syndromes. This beneficial effect is due to the presence of somatostatin receptors in high densities on the majority of endocrine tumours. The symptomatic effect is less pronounced in insulinomas, since 30 - 50% of these tumours lack or express only a few somatostatin receptors. With respect to symptomatic control, somatostatin receptor subtypes 2 and 5 are the most important and the currently available long-acting analogues octreotide and lanreotide bind preferentially to these receptor subtypes. Long-term studies have shown that somatostatin analogues are safe and that the most important adverse advent is the development of gallstones. The antiproliferative potency of somatostatin and its analogues in vitro and in experimental tumour models prompted a number of studies in patients with metastatic endocrine tumours that are generally unresponsive to conventional chemotherapeutic protocols. Stabilisation of tumour growth lasting for months to a few years was the most favourable result, occurring in 30 - 70% of patients. However, definite proof of antiproliferative potency in man is still pending since placebo-controlled studies are not available. Radioligand therapy based on 111Indium, 90Yttrium and 177Lutetium coupled to somatostatin analogues via bifunctional chelators is currently under investigation with promising data concerning long-lasting control of symptoms and tumour growth from Phase I trials.
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Affiliation(s)
- R Arnold
- Department of Internal Medicine, Division of Gastroenterology and Endocrinology, Philips University, Marburg, Germany
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Wood WM, Sarapura VD, Dowding JM, Woodmansee WW, Haakinson DJ, Gordon DF, Ridgway EC. Early gene expression changes preceding thyroid hormone-induced involution of a thyrotrope tumor. Endocrinology 2002; 143:347-59. [PMID: 11796486 DOI: 10.1210/endo.143.2.8636] [Citation(s) in RCA: 20] [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: 11/19/2022]
Abstract
Treatment with thyroid hormone (TH) results in shrinkage of a thyrotropic tumor grown in a hypothyroid host. We used microarray and Northern analysis to assess the changes in gene expression that preceded tumor involution. Of the 1,176 genes on the microarray, 7 were up-regulated, whereas 40 were decreased by TH. Many of these were neuroendocrine in nature and related to growth or apoptosis. When we examined transcripts for cell cycle regulators only cyclin-dependent kinase 2, cyclin A and p57 were down-regulated, whereas p15 was induced by TH. Retinoblastoma protein, c-myc, and mdm2 were unchanged, but E2F1 was down-regulated. TH also decreased expression of brain-derived neurotrophic factor, its receptor trkB, and the receptor for TRH. These, in addition to two other genes, neuronatin and PB cadherin, which were up- and down-regulated, respectively, showed a more rapid response to TH than the cell cycle regulators and may represent direct targets of TH. Finally, p19ARF was dramatically induced by TH, and although this protein can stabilize p53 by sequestering mdm2, we found no increase in p53 protein up to 48 h of treatment. In summary, we have described early changes in the expression of genes that may play a role in TH-induced growth arrest of a thyrotropic tumor. These include repression of specific growth factor and receptors and cell cycle genes as well as induction of other factors associated with growth arrest and apoptosis.
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Affiliation(s)
- William M Wood
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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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: 0.6] [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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Goddard I, Bauer S, Gougeon A, Lopez F, Giannetti N, Susini C, Benahmed M, Krantic S. Somatostatin inhibits stem cell factor messenger RNA expression by Sertoli cells and stem cell factor-induced DNA synthesis in isolated seminiferous tubules. Biol Reprod 2001; 65:1732-42. [PMID: 11717135 DOI: 10.1095/biolreprod65.6.1732] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Immature porcine Sertoli cells have been reported to be targets for the regulatory peptide somatostatin (SRIF), which inhibits the basal and FSH-induced proliferation of Sertoli cells through a decrease of cAMP production. In the present study, we show that SRIF inhibits both basal and FSH-stimulated expression of the stem cell factor (SCF), a Sertoli cell-specific gene. The SRIF-mediated inhibition of forskolin-triggered, but not of 8-bromoadenosine-cAMP-triggered, SCF mRNA expression demonstrates the involvement of adenylyl cyclase in underlying peptide actions. Moreover, these effects require functional coupling of specific plasma membrane receptors to adenylyl cyclase via inhibitory G proteins, because pertussis toxin prevents SRIF-mediated inhibition of SCF mRNA expression. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot assays suggest the involvement of sst2 receptors in SRIF actions on Sertoli cells. The biological relevance of these data is supported by an SRIF-mediated decrease in SCF-induced incorporation of [(3)H]thymidine in isolated seminiferous tubules. In situ hybridization and confocal microscopy show that, in seminiferous tubules only, spermatogonia display both c-kit and sst2 receptors. Taken together, these results suggest that SCF-stimulated DNA synthesis can be inhibited by SRIF in spermatogonia, but not in Sertoli and peritubular cells. Combined RT-PCR and immunohistochemical approaches point toward spermatogonia and Leydig cells as the source of testicular SRIF. These data argue in favor of paracrine/autocrine SRIF actions in testis.
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Affiliation(s)
- I Goddard
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 407, Faculté de Médecine Lyon Sud, F-69921 Oullins, France
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Steták A, Csermely P, Ullrich A, Kéri G. Physical and functional interactions between protein tyrosine phosphatase alpha, PI 3-kinase, and PKCdelta. Biochem Biophys Res Commun 2001; 288:564-72. [PMID: 11676480 DOI: 10.1006/bbrc.2001.5811] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The somatostatin analogue, TT-232 inhibits cell proliferation and induces apoptosis in a variety of tumor cells both in vivo and in vitro. While the early transient activation of Erk/MAPK was found to be important for the induction of cell cycle arrest, the signaling pathway leading to the activation of Erk/MAPK had not been fully established. Here we present evidence that activation of the Erk/MAPK pathway by TT-232 involves PI 3-kinase, PKCdelta and the protein tyrosine phosphatase alpha (PTPalpha). We show a physical interaction of PI 3-kinase and PKCdelta with PTPalpha and show that the tyrosine phosphatase plays a role in the activation of MAPK. In this process, PTPalpha Ser-180 and Ser-204 phosphorylation is critical for the induction of phosphatase activity, which is required for dephosphorylation of pp60(c-src). Taken together, we demonstrate the physical and functional association between PI 3-kinase, PKCdelta and PTPalpha in a signaling complex that mediates the antitumor activity of the somatostatin analogue TT-232.
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Affiliation(s)
- A Steták
- Department of Medical Chemistry, Peptide Biochemistry Research Group, Semmelweis University, Budapest, H-1088, Hungary.
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