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Bhat SZ, Salvatori R. Current role of pasireotide in the treatment of acromegaly. Best Pract Res Clin Endocrinol Metab 2024; 38:101875. [PMID: 38290866 DOI: 10.1016/j.beem.2024.101875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
"First-generation" somatostatin receptor agonists (SSTRAs) octreotide and lanreotide are the most commonly used first-line pharmacological therapy for patients with acromegaly. A subset of patients respond only partially or not at all to the first-generation SSTRA, necessitating the use of additional pharmacological agents or other modes of therapy. Pasireotide is a "second-generation" SSTRA that has multi-receptor activity. Prospective studies have shown promise in the use of pasireotide in patients with poor response to first-generation SSTRA. Here we elucidate the molecular pathways of resistance to first-generation SSTRA, the mechanism of action, pre-clinical and clinical evidence of the use of pasireotide in patients having incomplete / lack of response to first-generation SSTRA. We also discuss the clinical, pathological, and radiological markers predicting response to pasireotide, and the difference in side-effect profiles of pasireotide, compared to first-generation SSTRA.
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Affiliation(s)
- Salman Zahoor Bhat
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Tidal Health Endocrinology, Salisbury, MD, USA.
| | - Roberto Salvatori
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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Tatsi A, Maina T, Waser B, Krenning EP, de Jong M, Reubi JC, Cordopatis P, Nock BA. Bis(Disulfide)-Bridged Somatostatin-14 Analogs and Their [ 111In]In-Radioligands: Synthesis and Preclinical Profile. Int J Mol Sci 2024; 25:1921. [PMID: 38339198 PMCID: PMC10856354 DOI: 10.3390/ijms25031921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/25/2024] [Accepted: 01/27/2024] [Indexed: 02/12/2024] Open
Abstract
The overexpression of one or more somatostatin receptors (SST1-5R) in human tumors has provided an opportunity for diagnosis and therapy with somatostatin-like radionuclide carriers. The application of "pansomatostatin" analogs is expected to broaden the clinical indications and upgrade the diagnostic/therapeutic efficacy of currently applied SST2R-prefering radioligands. In pursuit of this goal, we now introduce two bicyclic somatostatin-14 (SS14) analogs, AT5S (DOTA-Ala1-Gly2-c[Cys3-Lys4-Asn5-c[Cys6-Phe7-DTrp8-Lys9-Thr10-Cys11]-Thr12-Ser13-Cys14]) and AT6S (DOTA-Ala1-Gly2-c[Cys3-Lys4-c[Cys5-Phe6-Phe7-DTrp8-Lys9-Thr10-Phe11-Cys12]-Ser13-Cys14]), suitable for labeling with trivalent radiometals and designed to sustain in vivo degradation. Both AT5S and AT6S and the respective [111In]In-AT5S and [111In]In-AT6S were evaluated in a series of in vitro assays, while radioligand stability and biodistribution were studied in mice. The 8/12-mer bicyclic AT6S showed expanded affinity for all SST1-5R and agonistic properties at the SST2R, whereas AT5S lost all affinity to SST1-5R. Both [111In]In-AT5S and [111In]In-AT6S remained stable in the peripheral blood of mice, while [111In]In-AT6S displayed low, but specific uptake in AR4-2J tumors and higher uptake in HEK293-SST3R tumors in mice. In summary, high radioligand stability was acquired by the two disulfide bridges introduced into the SS14 motif, but only the 8/12-mer ring AT6S retained a pansomatostatin profile. In consequence, [111In]In-AT6S targeted SST2R-/SST3R-positive xenografts in mice. These results call for further research on pansomatostatin-like radioligands for cancer theranostics.
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Affiliation(s)
- Aikaterini Tatsi
- Molecular Radiopharmacy, INRaSTES, NCSR “Demokritos”, GR-15341 Athens, Greece or (A.T.); (B.A.N.)
- Department of Pharmacy, University of Patras, GR-26500 Patras, Greece
| | - Theodosia Maina
- Molecular Radiopharmacy, INRaSTES, NCSR “Demokritos”, GR-15341 Athens, Greece or (A.T.); (B.A.N.)
| | - Beatrice Waser
- Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland; (B.W.); (J.C.R.)
| | - Eric P. Krenning
- Cyclotron Rotterdam BV, Erasmus MC, 3015 Rotterdam, The Netherlands;
| | - Marion de Jong
- Department of Radiology and Nuclear Medicine, Erasmus MC, 3015 Rotterdam, The Netherlands
| | - Jean Claude Reubi
- Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland; (B.W.); (J.C.R.)
| | - Paul Cordopatis
- Department of Pharmacy, University of Patras, GR-26500 Patras, Greece
| | - Berthold A. Nock
- Molecular Radiopharmacy, INRaSTES, NCSR “Demokritos”, GR-15341 Athens, Greece or (A.T.); (B.A.N.)
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Gao F, Zhang Y, Chen M, Song Z, Dong R, Qiu S, Shen C, Huang X, Geng H, Cheng W, Hu J. 18F-labeled somatostatin analogs for somatostatin receptors (SSTRs) targeted PET imaging of neuroendocrine tumors (NETs). Eur J Pharm Sci 2024; 193:106671. [PMID: 38104907 DOI: 10.1016/j.ejps.2023.106671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 12/08/2023] [Accepted: 12/11/2023] [Indexed: 12/19/2023]
Abstract
PURPOSE A novel 18F-radiolabeled somatostatin analogue, [Al18F]NODA-MPAA-HTA, was synthesized and evaluated for positron emission tomography (PET) imaging of Neuroendocrine tumors (NETs). [Al18F]NODA-MPAA-HTA was designed and synthesized by conjugating 18F nuclide with a modified KE108 peptide, a somatostatin analog with high affinity for all five subtypes of somatostatin receptors (SSTR 1-5), through coupling a bifunctional chelator (NODA) to target somatostatin receptor (SSTR) positive tumors. METHODS The amino group of KE108 peptide, a SSTRs-targeting pharmacophore, was conjugated with the carboxyl group of NODA by a condensation reaction to obtain the labeling precursor of [Al18F]NODA-MPAA-HTA, in which its precursor was obtained through Fmoc solid-phase methods. A novel methodology for Al18F labeling of chelating agent-biomolecule conjugates was used to synthesize [Al18F]NODA-MPAA-HTA. In vitro stabilities of [Al18F]NODA-MPAA-HTA were evaluated by incubating it in saline or bovine serum for 2 h. Ex vivo biodistribution and in vivo imaging of [Al18F]NODA-MPAA-HTA were further investigated to evaluate its SSTRs targeting ability and feasibility for the diagnosis of NETs using PET imaging. RESULTS [Al18F]NODA-MPAA-HTA was synthesized using a one-step 18F-AlF labeling procedure resulting in moderate radiochemical yield (60-80 %, non-decay corrected) and high radiochemical purity (>95 %). It exhibited good hydrophilicity and excellent stability in vitro, with a molar activity of 122 GBq/μmol. At 30 min and 60 min, the uptake of [Al18F] NODA-MPAA-HTA by HEK293-SSTR2 cells was 5.47 ± 0.97 %/105 cells and 12.11 ± 0.32 %/105 cells, respectively. The affinity of [Al18F]NODA-MPAA-HTA for SSTR2 was determined to be 8.77 ± 1.14 nM. In micro-PET imaging of HEK293-SSTR2 tumor-bearing mice, [Al18F]NODA-MPAA-HTA showed high tumor uptake of radioactivity and a high tumor-to-muscle ratio. Biodistribution results confirmed that radioactivity uptake in the tumor was significantly higher than that in the muscle by more than five-fold (P<0.001). Furthermore, the relatively low bone uptake of [Al18F]NODA-MPAA-HTA suggested that defluorination did not occur in vivo. These preliminary results provide experimental evidence for further study of Al18F-labeled somatostatin analogues as tumor probes for PET imaging of NETs. CONCLUSION Fluorine-18 is widely used as a radionuclide for the production of radiopharmaceuticals for positron emission tomography (PET). Due to its short half-life (T1/2,109.8 min), its ease of production will facilitate the widespread dissemination of this radiopharmaceutical. A high-quality [Al18F]NODA-MPAA-HTA was synthesized with satisfactory yield. This radiopharmaceutical demonstrated higher tumor uptake and better tumor-to-muscle contrast, resulting to excellent image quality. These findings suggest that the novel 18F-labeled somatostatin analogue, [Al18F]NODA-MPAA-HTA, is a promising tool for PET imaging of NETs.
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Affiliation(s)
- Fei Gao
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - Yunhan Zhang
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China; Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, China
| | - MengYi Chen
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - ZhiHao Song
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - RuiLin Dong
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - ShanShan Qiu
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - Chen Shen
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - XiaoYan Huang
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - Hao Geng
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China
| | - Weihua Cheng
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China.
| | - Ji Hu
- HTA Co., Ltd., CAEA Center of Excellence on Nuclear Technology Applications for Engineering and Industrialization of Radiopharmaceuticals, CNNC Engineering Research Center of Radiopharmaceuticals, Beijing, China.
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Comparison of the Anti-Tumour Activity of the Somatostatin Receptor (SST) Antagonist [177Lu]Lu-Satoreotide Tetraxetan and the Agonist [177Lu]Lu-DOTA-TATE in Mice Bearing AR42J SST2-Positive Tumours. Pharmaceuticals (Basel) 2022; 15:ph15091085. [PMID: 36145306 PMCID: PMC9506113 DOI: 10.3390/ph15091085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/23/2022] [Accepted: 08/25/2022] [Indexed: 11/16/2022] Open
Abstract
Limited experiments have compared the treatment effects of repetitive cycles of radiolabelled somatostatin (SST) analogues. In vitro and in vivo experiments were conducted in an AR42J cancer cell model, comparing the antagonist [177Lu]Lu-satoreotide tetraxetan with the agonist [177Lu]Lu-DOTA-TATE in terms of their binding properties, biodistribution, anti-tumour activity and toxicity. Histopathological and immunohistochemical examinations were performed at different timepoints. In the in vitro assays, [177Lu]Lu-satoreotide tetraxetan recognised twice as many SST2 binding sites as [177Lu]Lu-DOTA-TATE. In mice treated once a week for four consecutive weeks, [177Lu]Lu-satoreotide tetraxetan (15 MBq) revealed a significantly greater median time taken to reach a tumour volume of 850 mm3 (68 days) compared to [177Lu]Lu-DOTA-TATE at 15 MBq (43 days) or 30 MBq (48 days). This was associated with a higher tumour uptake, enhanced DNA damage and no or mild effects on body weight, haematological toxicity, or renal toxicity with [177Lu]Lu-satoreotide tetraxetan (15 MBq). At the end of the study, complete tumour senescence was noted in 20% of animals treated with [177Lu]Lu-satoreotide tetraxetan, in 13% of those treated with [177Lu]Lu-DOTA-TATE at 30 MBq, and in none of those treated with [177Lu]Lu-DOTA-TATE at 15 MBq. In conclusion, repeated administrations of [177Lu]Lu-satoreotide tetraxetan were able to potentiate peptide receptor radionuclide therapy with a higher tumour uptake, longer median survival, and enhanced DNA damage, with a favourable efficacy/safety profile compared to [177Lu]Lu-DOTA-TATE.
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Octreotide and Pasireotide Combination Treatment in Somatotroph Tumor Cells: Predominant Role of SST 2 in Mediating Ligand Effects. Cancers (Basel) 2021; 13:cancers13081816. [PMID: 33920241 PMCID: PMC8069349 DOI: 10.3390/cancers13081816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 04/08/2021] [Indexed: 12/16/2022] Open
Abstract
Simple Summary First-generation somatostatin receptor ligands, such as octreotide, are the first-line medical therapy in acromegaly. Octreotide shows preferential binding for somatostatin receptor subtype 2 (SST2), while the second-generation ligand, pasireotide, has high affinity for multiple SSTs. We aimed to elucidate whether pasireotide acts via other receptors than SST2 in somatotroph tumors, and to investigate the potential role of the combination therapy octreotide plus pasireotide. We found that octreotide and pasireotide are superimposable in reducing GH secretion in cultured somatotroph tumor cells, as well as in inhibiting cell proliferation and intracellular pathway activity in rat GH4C1 cells (a model of somatotroph tumors). We did not find any additive/synergistic effect for the combination treatment. Furthermore, we observed that co-incubation with a SST2-selective antagonist reversed the inhibitory effect of both compounds. Therefore, the two drugs act mainly via SST2 in somatotroph tumor cells, and their combination is not superior to single agent treatment. Abstract First-generation somatostatin receptor ligands (fg-SRLs), such as octreotide (OCT), represent the first-line medical therapy in acromegaly. Fg-SRLs show a preferential binding affinity for somatostatin receptor subtype-2 (SST2), while the second-generation ligand, pasireotide (PAS), has high affinity for multiple SSTs (SST5 > SST2 > SST3 > SST1). Whether PAS acts via SST2 in somatotroph tumors, or through other SSTs (e.g., SST5), is a matter of debate. In this light, the combined treatment OCT+PAS could result in additive/synergistic effects. We evaluated the efficacy of OCT and PAS (alone and in combination) on growth hormone (GH) secretion in primary cultures from human somatotroph tumors, as well as on cell proliferation, intracellular signaling and receptor trafficking in the rat GH4C1 cell line. The results confirmed the superimposable efficacy of OCT and PAS in reducing GH secretion (primary cultures), cell proliferation, cAMP accumulation and intracellular [Ca2+] increase (GH4C1 cells), without any additive effect observed for OCT+PAS. In GH4C1 cells, co-incubation with a SST2-selective antagonist reversed the inhibitory effect of OCT and PAS on cell proliferation and cAMP accumulation, while both compounds resulted in a robust internalization of SST2 (but not SST5). In conclusion, OCT and PAS seem to act mainly through SST2 in somatotroph tumor cells in vitro, without inducing any additive/synergistic effect when tested in combination.
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Carr HS, Chang JT, Frost JA. The PDZ Domain Protein SYNJ2BP Regulates GRK-Dependent Sst2A Phosphorylation and Downstream MAPK Signaling. Endocrinology 2021; 162:6031468. [PMID: 33313679 PMCID: PMC7799432 DOI: 10.1210/endocr/bqaa229] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Indexed: 11/19/2022]
Abstract
The somatostatin receptor 2A (SST2) is a G-protein-coupled receptor (GPCR) that is expressed in neuroendocrine tissues within the gastrointestinal tract and brain, and is commonly overexpressed in many neuroendocrine tumors. Moreover, SST2 agonists are used clinically as the primary pharmacological treatment to suppress excess hormone secretion in a variety of neuroendocrine tumors. Despite its wide clinical use, mechanisms controlling the trafficking and signaling of SST2 are not fully understood. SST2 contains a C-terminal post-synaptic density 95, Drosophila discs large, zona-occludens 1 (PDZ) domain-binding motif that has been shown to interact with 3 different PDZ domain-containing proteins. However, the consequences of these interactions are not well understood, nor is it known whether additional PDZ domain proteins interact with SST2. Through unbiased screening we have identified 10 additional PDZ domain proteins that interact with SST2. We chose one of these, SYNJ2BP, for further study. We observed that SYNJ2BP interacted with SST2 in an agonist-dependent manner, and that this required the PDZ binding site of SST2. Importantly, overexpression of SYNJ2BP enhanced ligand-stimulated receptor internalization. Mechanistically, SYNJ2BP interacted with G-protein-coupled receptor kinase 2 (GRK2) and promoted GRK-dependent phosphorylation of the receptor after somatostatin stimulation. Interaction with GRK2 required the C-terminus of SYNJ2BP. Binding to SYNJ2BP did not affect the ability of SST2 to suppress 3',5'-cyclic adenosine 5'-monophosphate production, but was required for optimal agonist-stimulated extracellularly regulated kinase 1/2 activation. These data indicated that SYNJ2BP is an SST2-interacting protein that modulates agonist-stimulated receptor regulation and downstream signaling.
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Affiliation(s)
- Heather S Carr
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Jeffrey T Chang
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Jeffrey A Frost
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, USA
- Correspondence: Jeffrey A. Frost, PhD, Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin St, Houston, TX 77030, USA.
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Gatto F, Arvigo M, Ferone D. Somatostatin receptor expression and patients' response to targeted medical treatment in pituitary tumors: evidences and controversies. J Endocrinol Invest 2020; 43:1543-1553. [PMID: 32557353 DOI: 10.1007/s40618-020-01335-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 06/11/2020] [Indexed: 12/23/2022]
Abstract
BACKGROUND Somatostatin receptors (SSTs) are widely co-expressed in pituitary tumors. SST2 and SST5 are the most represented SST subtypes. First-generation somatostatin receptor ligands (SRLs) mainly target SST2, while pasireotide, a multi-receptor ligand, shows high binding affinity for both SST5 and SST2. Therefore, SRLs are routinely used as medical treatment for GH-, TSH-, and ACTH-secreting pituitary tumors. METHODS Critical revision of literature data correlating SST expression with patients' response to SRLs. RESULTS SST2 expression in somatroph tumors directly correlates with GH and IGF-1 decrease after first-generation SRL treatment. SST2 immunohistochemistry represents a valuable tool to predict biochemical response to first-generation SRLs in acromegalic patients. Pasireotide seems to exert its biological effects via SST2 in unselected patients. However, in those subjects resistant to first-generation SRLs, harbouring tumors with negligible SST2 expression, pasireotide can act throughout SST5. More than somatotroph tumors, TSH-omas represent the paradigm of tumors showing a satisfactory response to SRLs. This is probably due to the high SST2 expression observed in nearly 100% of cases, as well as to the balanced amount of SST5. In corticotroph tumors, pasireotide mainly act via SST5, although there is a need for translational studies correlating its efficacy with SST expression in this peculiar tumor histotype. CONCLUSIONS The assumption "more target receptor, more drug efficacy" is not straightforward for SRLs. The complex pathophysiology of SSTs, and the technical challenges faced to translate research findings into clinical practice, still need our full commitment to make receptor evaluation a worthwhile procedure for individualizing treatment decisions.
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Affiliation(s)
- F Gatto
- Endocrinology Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi, 10, 16132, Genoa, Italy.
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties (DIMI), Centre of Excellence for Biomedical Research (CEBR), University of Genoa, Genoa, Italy.
| | - M Arvigo
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties (DIMI), Centre of Excellence for Biomedical Research (CEBR), University of Genoa, Genoa, Italy
| | - D Ferone
- Endocrinology Unit, IRCCS Ospedale Policlinico San Martino, Largo R. Benzi, 10, 16132, Genoa, Italy
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties (DIMI), Centre of Excellence for Biomedical Research (CEBR), University of Genoa, Genoa, Italy
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Structural modifications of amino acid sequences of radiolabeled peptides for targeted tumor imaging. Bioorg Chem 2020; 99:103802. [DOI: 10.1016/j.bioorg.2020.103802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 03/19/2020] [Accepted: 03/25/2020] [Indexed: 12/18/2022]
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Xiang Q, Li JJ, Li CY, Tian RB, Li XH. Somatostatin Type 2 Receptor Antibody Enhances Mechanical Hyperalgesia in the Dorsal Root Ganglion Neurons after Sciatic Nerve-pinch Injury: Evidence of Behavioral Studies and Bax Protein Expression. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2019; 18:791-797. [PMID: 31686636 DOI: 10.2174/1871527318666191101094412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 09/16/2019] [Accepted: 10/22/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Our previous study has indicated that somatostatin potently inhibits neuropathic pain through the activation of its type 2 receptor (SSTR2) in mouse dorsal root ganglion and spinal cord. However, the underlying mechanism of this activation has not been elucidated clearly. OBJECTIVE The aim of this study is to perform the pharmacological studies on the basis of sciatic nerve-pinch mice model and explore the underlying mechanism involving SSTR2. METHODS On the basis of a sciatic nerve-pinch injury model, we aimed at comparing the painful behavior and dorsal root ganglion neurons neurochemical changes after the SSTR2 antibody (anti- SSTR2;5μl,1μg/ml) administration in the mouse. RESULTS After pinch nerve injury, we found that the mechanical hyperalgesia and severely painful behavior (autotomy) were detected after the application of SSTR2 antibody (anti-SSTR2; 5μl, 1μg/ml) on the pinch-injured nerve. The up-regulated phosphorylated ERK (p-ERK) expression and the apoptotic marker (i.e., Bax) were significantly decreased in DRGs after anti-SSTR2 treatment. CONCLUSION The current data suggested that inhibitory changes in proteins from the apoptotic pathway in anti-SSTR2-treated groups might be taking place to overcome the protein deficits caused by SSTR2 antibody and supported the new therapeutic intervention with SSTR2 antagonist for neuronal degeneration following nerve injury.
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Affiliation(s)
- Qiong Xiang
- Institute of Medicine, Medical Research Center, Jishou University, Hunan, China
| | - Jing-Jing Li
- Institute of Medicine, Medical Research Center, Jishou University, Hunan, China
| | - Chun-Yan Li
- Institute of Medicine, Medical Research Center, Jishou University, Hunan, China
| | - Rong-Bo Tian
- Institute of Medicine, Medical Research Center, Jishou University, Hunan, China
| | - Xian-Hui Li
- Institute of Medicine, Medical Research Center, Jishou University, Hunan, China
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Biological and Biochemical Basis of the Differential Efficacy of First and Second Generation Somatostatin Receptor Ligands in Neuroendocrine Neoplasms. Int J Mol Sci 2019; 20:ijms20163940. [PMID: 31412614 PMCID: PMC6720449 DOI: 10.3390/ijms20163940] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/1970] [Revised: 08/05/2019] [Accepted: 08/08/2019] [Indexed: 02/07/2023] Open
Abstract
Endogenous somatostatin shows anti-secretory effects in both physiological and pathological settings, as well as inhibitory activity on cell growth. Since somatostatin is not suitable for clinical practice, researchers developed synthetic somatostatin receptor ligands (SRLs) to overcome this limitation. Currently, SRLs represent pivotal tools in the treatment algorithm of neuroendocrine tumors (NETs). Octreotide and lanreotide are the first-generation SRLs developed and show a preferential binding affinity to somatostatin receptor (SST) subtype 2, while pasireotide, which is a second-generation SRL, has high affinity for multiple SSTs (SST5 > SST2 > SST3 > SST1). A number of studies demonstrated that first-generation and second-generation SRLs show distinct functional properties, besides the mere receptor affinity. Therefore, the aim of the present review is to critically review the current evidence on the biological effects of SRLs in pituitary adenomas and neuroendocrine tumors, by mainly focusing on the differences between first-generation and second-generation ligands.
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Olsen C, Memarzadeh K, Ulu A, Carr HS, Bean AJ, Frost JA. Regulation of Somatostatin Receptor 2 Trafficking by C-Tail Motifs and the Retromer. Endocrinology 2019; 160:1031-1043. [PMID: 30822353 PMCID: PMC6462214 DOI: 10.1210/en.2018-00865] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 02/25/2019] [Indexed: 12/15/2022]
Abstract
The Gi-coupled somatostatin receptor 2 (SST2) is a G protein-coupled receptor (GPCR) that mediates many of somatostatin's neuroendocrine actions. Upon stimulation, SST2 is rapidly internalized and transported to early endosomes before being recycled to the plasma membrane. However, little is known about the intracellular itinerary of SST2 after it moves to the early endosomal compartment or the cytoplasmic proteins that regulate its trafficking. As postsynaptic density protein/discs large 1/zonula occludens-1 (PDZ) domain interactions often regulate the trafficking and signaling potential of GPCRs, we examined the role of the SST2 PDZ ligand and additional C-terminal residues in controlling its intracellular trafficking. We determined that SST2 can recycle to the plasma membrane via multiple pathways, including a LAMP1/Rab7-positive late endosome to the trans-Golgi network (TGN) pathway. Trafficking from the late endosome to the TGN is often regulated by the retromer complex of endosomal coat proteins, and disrupting the retromer components sorting nexins 1/2 inhibits the budding of SST2 from late endosomes. Moreover, trafficking through the late endosomal/TGN pathway is dependent on an intact PDZ ligand and C-terminal tail, as truncating either the 3 or 10 C-terminal amino acids of SST2 alters the pathway through which it recycles to the plasma membrane. Moreover, addition of these amino acids to a heterologous receptor is sufficient to redirect it from a degradation pathway to a recycling itinerary. Our results demonstrate that endosomal trafficking of SST2 is dependent on numerous regulatory mechanisms controlled by its C terminus and the retromer machinery.
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Affiliation(s)
- Courtney Olsen
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
| | - Kimiya Memarzadeh
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas
| | - Arzu Ulu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Heather S Carr
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Andrew J Bean
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, Texas
- Department of Pediatrics, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Jeffrey A Frost
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
- MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas
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12
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Muhammad A, Coopmans EC, Gatto F, Franck SE, Janssen JAMJL, van der Lely AJ, Hofland LJ, Neggers SJCMM. Pasireotide Responsiveness in Acromegaly Is Mainly Driven by Somatostatin Receptor Subtype 2 Expression. J Clin Endocrinol Metab 2019; 104:915-924. [PMID: 30346538 DOI: 10.1210/jc.2018-01524] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 10/16/2018] [Indexed: 02/06/2023]
Abstract
BACKGROUND The response to first-generation somatostatin receptor ligands (SRLs) treatment in acromegaly correlates with expression of somatostatin receptor subtype 2 (SSTR2). However, pasireotide shows the highest binding affinity for SSTR subtype 5 (SSTR5). It has been suggested that in acromegaly, SSTR5 expression is better at predicting the response to pasireotide long-acting release (PAS-LAR) treatment than SSTR2 expression. AIM To investigate in patients with active acromegaly whether response to SRL treatment correlates to PAS-LAR treatment and to what extent SSTR2 and SSTR5 expression are correlated to the response to PAS-LAR treatment. METHODS We included 52 patients from a cohort that initially received SRL treatment, followed by SRL and pegvisomant combination treatment, and finally PAS-LAR treatment. The long-term response to PAS-LAR was evaluated using a PAS-LAR score. In 14 out of 52 patients, somatotroph adenoma tissue samples were available to evaluate SSTR2 and SSTR5 expression using a previously validated immunoreactivity score (IRS). RESULTS The percentage IGF-I (times the upper limit of normal) reduction, which was observed after SRL treatment, correlated with PAS-LAR response score during follow-up (r = 0.40; P = 0.003; n = 52). After exclusion of SRL-pretreated patients, SSTR2 IRS was positively correlated to PAS-LAR score (r = 0.58; P = 0.039; n = 9), whereas SSTR5 IRS showed no relation (r = 0.35; P = 0.36; n = 9). CONCLUSIONS In a cohort of patients partially responsive to SRLs, the IGF-I-lowering effects of PAS-LAR treatment correlated with the effect of SRL treatment and seemed to be mainly driven by SSTR2 expression instead of SSTR5.
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Affiliation(s)
- Ammar Muhammad
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Eva C Coopmans
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Federico Gatto
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties, Ospedale Policlinico San Martino, Genova, Italy
| | - Sanne E Franck
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Joseph A M J L Janssen
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Aart Jan van der Lely
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Leo J Hofland
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Sebastian J C M M Neggers
- Department of Medicine, Endocrinology Section, Pituitary Center Rotterdam, Erasmus University Medical Center, Rotterdam, Netherlands
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13
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Gatto F, Arvigo M, Amarù J, Campana C, Cocchiara F, Graziani G, Bruzzone E, Giusti M, Boschetti M, Ferone D. Cell specific interaction of pasireotide: review of preclinical studies in somatotroph and corticotroph pituitary cells. Pituitary 2019; 22:89-99. [PMID: 30483918 DOI: 10.1007/s11102-018-0926-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Pasireotide is a second-generation somatostatin (SRIF) receptor ligand (SRL), approved for medical treatment of acromegaly and Cushing's disease (CD). The molecule is a stable cyclohexapeptide synthetized based on SRIF structure. Differently from first-generation SRLs (e.g. octreotide), preferentially binding somatostatin receptor (SST) subtype 2 (SST2), pasireotide has high affinity for multiple SSTs (SST5 > SST2 > SST3 > SST1). Interestingly, early preclinical studies demonstrated that pasireotide shows distinct functional properties compared to SRIF and first-generation SRLs when binding SSTs. METHODS We aimed to highlight the differential receptor-targeted action of pasireotide in the treatment of somatotroph and corticotroph adenomas, throughout the critical revision of preclinical studies carried out on acromegaly and CD models. RESULTS Different authors demonstrated that the antisecretory effect of pasireotide in somatotroph adenoma cell cultures is comparable to that of the SST2-preferential agonist octreotide. Some reports even show a direct correlation between SST2 mRNA expression and GH reduction after pasireotide treatment, thus laying for a predominant role of SST2 in driving pasireotide efficacy in somatotropinomas in vitro. On the other hand, the inhibitory effect of pasireotide on ACTH secretion in corticotropinoma cells seems to be mainly mediated by SST5. Indeed, most reports show a higher potency and efficacy of pasireotide compared to SST2 preferential agonists, while functional studies confirm the pivotal role of SST5 targeting in corticotroph cells. CONCLUSIONS The analysis of preclinical studies carried out in somatotroph and corticoph adenomas points out that pasireotide shows a cell-specific activity, exerting its biological effects via different SSTs in the different adenoma histotypes.
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Affiliation(s)
- Federico Gatto
- Endocrinology Unit, Department of Internal Medicine, Policlinico San Martino, 16132, Genoa, Italy.
| | | | | | | | | | | | | | - Massimo Giusti
- Endocrinology Unit, Department of Internal Medicine, Policlinico San Martino, 16132, Genoa, Italy
- University of Genoa, Genoa, Italy
| | - Mara Boschetti
- Endocrinology Unit, Department of Internal Medicine, Policlinico San Martino, 16132, Genoa, Italy
- University of Genoa, Genoa, Italy
| | - Diego Ferone
- Endocrinology Unit, Department of Internal Medicine, Policlinico San Martino, 16132, Genoa, Italy
- University of Genoa, Genoa, Italy
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14
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Ribeiro-Oliveira A, Schweizer JROL, Amaral PHS, Bizzi MF, Silveira WCD, Espirito-Santo DTA, Zille G, Soares BS, Schmid HA, Yuen KCJ. Pasireotide treatment does not modify hyperglycemic and corticosterone acute restraint stress responses in rats. Stress 2018; 21:370-375. [PMID: 29661114 DOI: 10.1080/10253890.2018.1451838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Abstract
Pasireotide is a new-generation somatostatin analog that acts through binding to multiple somatostatin receptor subtypes. Studies have shown that pasireotide induces hyperglycemia, reduces glucocorticoid secretion, alters neurotransmission, and potentially affects stress responses typically manifested as hyperglycemia and increased corticosterone secretion. This study specifically aimed to evaluate whether pasireotide treatment modifies glucose and costicosterone secretion in response to acute restraint stress. Male Holtzman rats of 150-200 g were treated with pasireotide (10 µg/kg/day) twice-daily for two weeks or vehicle for the same period. Blood samples were collected at baseline and after 5, 10, 30, and 60 min of restraint stress. The three experimental groups comprised of vehicle + restraint (VEHR), pasireotide + restraint (PASR), and pasireotide + saline (PASNR). Following pasireotide treatment, no significant differences in baseline glucose and corticosterone levels were observed among the three groups. During restraint, hyperglycemia was observed at 10 min (p < .01 for both comparisons), peaked at 30 min (p < .01 for both comparisons) and showed higher 60 min areas under glucose curves in the VEHR and PASR stressed groups when compared to the non-stressed PASNR group (p < .05 for both comparisons). Restraint also increased corticosterone secretion in the VEHR and PASR stressed groups at 5 min (p < .01 for both comparisons), and peaked at 30 min (p < .01 for both comparisons) with corresponding higher 60 min areas under corticosterone curves when compared to the non-stressed PASNR group (p < .01 for both comparisons). In conclusion, pasireotide treatment does not modify hyperglycemic- and corticosterone-restraint stress responses, thus preserving acute stress regulation.
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Affiliation(s)
- Antônio Ribeiro-Oliveira
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Junia R O L Schweizer
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Pedro H S Amaral
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Mariana F Bizzi
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Warley Cezar da Silveira
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Daniel T A Espirito-Santo
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Giancarlo Zille
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Beatriz S Soares
- a Department of Internal Medicine, Laboratory of Endocrinology, School of Medicine , Federal University of Minas Gerais , Belo Horizonte , MG , Brazil
| | - Herbert A Schmid
- b Department of Oncology Research , Novartis Institutes for BioMedical Research, Novartis Pharma AG , Basel , Switzerland
| | - Kevin C J Yuen
- c Department of Neuroendocrinology , Barrow Pituitary Center, Barrow Neurological Institute , Phoenix , AZ, USA
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15
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Rodriguez M, Frost JA, Schonbrunn A. Real-Time Signaling Assays Demonstrate Somatostatin Agonist Bias for Ion Channel Regulation in Somatotroph Tumor Cells. J Endocr Soc 2018; 2:779-793. [PMID: 30151433 PMCID: PMC6106105 DOI: 10.1210/js.2018-00115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 06/11/2018] [Indexed: 11/19/2022] Open
Abstract
Acromegaly is a neuroendocrine disorder caused by excess secretion of GH by somatotroph tumor cells. It is often treated with somatostatin receptor (SSTR) 2 agonists, which suppress GH secretion. SOM230 is a somatostatin analogue that targets multiple SSTRs and was recently approved for patients with treatment-resistant acromegaly. Previous reports indicate that SOM230 may function as a biased agonist, suggesting that its ability to selectively activate SSTR-dependent signaling events may contribute to its therapeutic efficacy. To better understand how SOM230 modulates Sstr2A function, which is the most commonly expressed SSTR in somatotrophs, we used real-time assays to study SOM230-dependent signaling in rat pituitary tumor cells. We observed that SOM230 suppressed cAMP production in a Gαi-dependent manner, similar to conventional Sstr2A agonists. However, it did not cause receptor internalization as would be expected for an Sstr2A agonist. Surprisingly, SOM230 did not cause membrane hyperpolarization, which is an important mechanism by which Sstr2a activation suppresses intracellular calcium (Ca2+) accumulation and GH secretion. In fact, SOM230 inhibited the ability of conventional somatostatin analogues to control membrane potential. However, SOM230 still inhibited intracellular Ca2+ accumulation in a novel, Gβγ-dependent manner. These studies show that SOM230 exhibits strong agonist bias in regulating signaling pathways downstream of Sstr2A that control GH secretion.
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Affiliation(s)
- Melissa Rodriguez
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Jeffrey A Frost
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
| | - Agnes Schonbrunn
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas
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16
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Tarasco E, Seebeck P, Pfundstein S, Daly AF, Eugster PJ, Harris AG, Grouzmann E, Lutz TA, Boyle CN. Effect of AP102, a subtype 2 and 5 specific somatostatin analog, on glucose metabolism in rats. Endocrine 2017; 58:124-133. [PMID: 28822091 DOI: 10.1007/s12020-017-1386-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/26/2017] [Indexed: 12/19/2022]
Abstract
PURPOSE Somatostatin analogs are widely used to treat conditions associated with hormonal hypersecretion such as acromegaly and metastatic neuroendocrine tumors. First generation somatostatin analogs, such as octreotide and lanreotide, have high affinity for somatostatin receptor subtype 2 (SSTR2), but have incomplete efficacy in many patients. Pasireotide targets multiple SSTRs, having the highest affinity for SSTR5, but causes hyperglycemia and diabetes mellitus in preclinical and clinical studies. AP102 is a new somatostatin analogs with high affinity at both SSTR2 and SSTR5. We aimed to characterize the effects of AP102 vs. pasireotide on random and dynamic glucose levels, glucoregulatory hormone concentrations and growth axis measures in healthy Sprague-Dawley rats. METHODS Three doses of each compound were evaluated under acute conditions (1, 10, and 30 µg/kg s.c.), and two doses during a chronic (4-week) infusion (3 and 10 µg/kg/h s.c.). RESULTS Neither acute nor chronic AP102 administration altered blood glucose concentrations or dynamic responses following an intraperitoneal glucose tolerance test. In contrast, acute and chronic pasireotide dosing increased random and post-intraperitoneal glucose tolerance test blood glucose measures, compared to vehicle-treated controls. Both AP102 and pasireotide acutely suppressed growth hormone levels, although insulin-like growth factor-1 and somatic growth was suppressed to a greater extent with pasireotide. CONCLUSIONS AP102 is a new dual SSTR2/SSTR5-specific somatostatin analog that acutely reduces growth hormone but does not cause hyperglycemia during acute or chronic administration in a healthy rat model. Further studies in diabetic animals and in humans are necessary to determine the potential utility of AP102 in the clinical setting.
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Affiliation(s)
- Erika Tarasco
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland
- Zurich Centre for Integrative Human Physiology, University of Zurich, 8057, Zurich, Switzerland
| | - Petra Seebeck
- Zurich Integrative Rodent Physiology (ZIRP), University of Zurich, 8057, Zurich, Switzerland
| | - Svende Pfundstein
- Zurich Integrative Rodent Physiology (ZIRP), University of Zurich, 8057, Zurich, Switzerland
| | - Adrian F Daly
- Department of Endocrinology, Centre Hospitalier Universitaire de Liège, University of Liège, Liège, Belgium
| | - Philippe J Eugster
- Laboratoire des Catecholamines et Peptides, Service de Biomédecine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Alan G Harris
- Department of Endocrinology, Centre Hospitalier Universitaire de Liège, University of Liège, Liège, Belgium
| | - Eric Grouzmann
- Laboratoire des Catecholamines et Peptides, Service de Biomédecine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Thomas A Lutz
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland
- Zurich Centre for Integrative Human Physiology, University of Zurich, 8057, Zurich, Switzerland
| | - Christina N Boyle
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, 8057, Zurich, Switzerland.
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17
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Carmona-Bayonas A, Jiménez-Fonseca P, Custodio A, Grande E, Capdevila J, López C, Teule A, Garcia-Carbonero R. Optimizing Somatostatin Analog Use in Well or Moderately Differentiated Gastroenteropancreatic Neuroendocrine Tumors. Curr Oncol Rep 2017; 19:72. [PMID: 28920153 DOI: 10.1007/s11912-017-0633-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Somatostatin analogues, aiming to control tumor secretion or growth, constitute the most attractive therapeutic option for patients with well-differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs). The objective of this article is to provide a comprehensive review of the current state-of-the-art knowledge gaps and potential opportunities for future development and optimization of this therapeutic modality. METHOD A contextualized systematic review with a narrative component was conducted using PubMed, The Cochrane Library, EMBASE, and Google Scholar. Titles were screened, and non-English, duplicate, or irrelevant entries were excluded. Selection criteria for articles included the following: publication in English between 1995 and 2016, patients with GEP-NETs, analysis of efficacy, safety, practical management considerations, predictive factors, and/or strategies for overcoming resistance, concerning somatostatin analogs. RESULTS Ninety-seven studies out of 2771 screened publications met the inclusion criteria (16 randomized clinical trials, 27 phase II trials, 3 phase I trials, 3 subgroup analyses of clinical trials, 1 open-label extension of a randomized trial, 1 phase IV trial, 32 observational studies, and 14 basic research articles). The nature and scope of literature was diverse with most articles dedicated to drug efficacy or indications of use (n = 49), pharmacological issues (n = 8), assessment or predictors of response (n = 4), practical management (n = 11), combination therapy or other means to overcome resistance (n = 19), receptors and signaling pathways (n = 3), and subgroup analyses (n = 3). CONCLUSION In this appraisal, we have found some practical aspects that can help to the optimization of somatostatin analog (SSA) therapy in patients with well-differentiated GEP-NETs. We have also identified areas of uncertainty in an effort to guide clinical research in the coming years.
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Affiliation(s)
- Alberto Carmona-Bayonas
- Department of Hematology and Medical Oncology, Morales Meseguer University Hospital, Calle Marqués de los Vélez, s/n, CP 30008, Murcia, Spain.
| | | | - Ana Custodio
- Department of Medical Oncology, La Paz University Hospital, Madrid, Spain
| | - Enrique Grande
- Department of Medical Oncology, Ramón y Cajal University Hospital, Madrid, Spain
| | - Jaume Capdevila
- Department of Medical Oncology, Vall D'Hebrón University Hospital, Vall D'Hebrón Institute of Oncology (VHIO), Universitat Autònoma de Barcelona, center affiliated with the Red Temática de Investigación Cooperativa en Cáncer (RTICC), Instituto Carlos III, Spanish Ministry of Science and Innovation, Barcelona, Spain
| | - Carlos López
- Department of Medical Oncology, Marqués de Valdecilla University Hospital, Santander, Spain
| | - Alex Teule
- Department of Medical Oncology, Institut Català d'Oncologia, L'Hospitalet de Llobregat, center affiliated with the Red Temática de Investigación Cooperativa en Cáncer (RTICC), Instituto Carlos III, Spanish Ministry of Science and Innovation, Barcelona, Spain
| | - Rocío Garcia-Carbonero
- Department of Medical Oncology, Doce de Octubre University Hospital, center affiliated with the Red Temática de Investigación Cooperativa en Cáncer (RTICC), Instituto Carlos III, Spanish Ministry of Science and Innovation, Madrid, Spain
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18
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Graillon T, Romano D, Defilles C, Lisbonis C, Saveanu A, Figarella-Branger D, Roche PH, Fuentes S, Chinot O, Dufour H, Barlier A. Pasireotide is more effective than octreotide, alone or combined with everolimus on human meningioma in vitro. Oncotarget 2017; 8:55361-55373. [PMID: 28903425 PMCID: PMC5589664 DOI: 10.18632/oncotarget.19517] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 07/12/2017] [Indexed: 12/18/2022] Open
Abstract
Pasireotide is a somatostatin analog (SSA) that targets somatostatin receptor subtype 1 (SST1), SST2, SST3, and SST5 with a high affinity. Pasireotide has a better antisecretory effect in acromegaly, Cushing's disease, and neuroendocrine tumors than octreotide. In this study, we compared the effects of pasireotide to those of octreotide in vitro on meningioma primary cell cultures, both alone and in combination with the mTOR inhibitor everolimus. Significant mRNA expression levels of SST1, SST2, and SST5 were observed in 40.5%, 100%, and 35% of meningioma samples, respectively. Pasireotide had a significantly stronger inhibitory effect on cell proliferation than octreotide. The effect of pasireotide, but not of octreotide, was significantly stronger in the group expressing the highest level of SST1 mRNA. Combined treatment with pasireotide and everolimus induced a higher reduction in cell viability than that with octreotide plus everolimus. Moreover, pasireotide decreased Akt phosphorylation and reversed everolimus-induced Akt hyperphosphorylation to a higher degree than octreotide. Using 4E-BP1 siRNA (si4E-BP), we demonstrated that 4E-BP1 protein silencing significantly reversed the response to everolimus, both alone and in combination with SSAs. Moreover, si4E-BP completely reversed the inhibition of cyclin D1 expression level and the increase in p27kip1 induced by SSAs, both alone and in combination with everolimus. Our results strongly support the need for further studies on the combination of pasireotide and everolimus in medical therapy for meningiomas.
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Affiliation(s)
- Thomas Graillon
- Aix Marseille Univ, CNRS CRN2M UMR7286, Marseille, France.,APHM, La Timone Hospital, Department of Neurosurgery, Marseille, France
| | - David Romano
- Aix Marseille Univ, CNRS CRN2M UMR7286, Marseille, France
| | | | | | - Alexandru Saveanu
- Aix Marseille Univ, CNRS CRN2M UMR7286, Marseille, France.,APHM, La Conception Hospital, Molecular Biology Laboratory, Marseille, France
| | - Dominique Figarella-Branger
- APHM, La Timone Hospital, Department of Anatomopathology and Neuropathology, Marseille, France.,Aix Marseille Univ, INSERM, CRO2 UMR911, Marseille, France
| | | | - Stéphane Fuentes
- APHM, La Timone Hospital, Department of Neurosurgery, Marseille, France
| | - Olivier Chinot
- Aix Marseille Univ, INSERM, CRO2 UMR911, Marseille, France.,APHM, La Timone Hospital, Department of Neuro-oncology, Marseille, France
| | - Henry Dufour
- Aix Marseille Univ, CNRS CRN2M UMR7286, Marseille, France.,APHM, La Timone Hospital, Department of Neurosurgery, Marseille, France
| | - Anne Barlier
- Aix Marseille Univ, CNRS CRN2M UMR7286, Marseille, France.,APHM, La Conception Hospital, Molecular Biology Laboratory, Marseille, France
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19
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Tulipano G, Faggi L, Schulz S, Spinello M, Giustina A. Effects of pasireotide (SOM230) on protein turnover and p70S6 kinase-S6 ribosomal protein signaling pathway in rat skeletal muscle cells. Endocrine 2017; 57:179-182. [PMID: 28120181 DOI: 10.1007/s12020-017-1235-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 01/13/2017] [Indexed: 11/24/2022]
Affiliation(s)
- Giovanni Tulipano
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
| | - Lara Faggi
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Stefan Schulz
- Pharmacology and Toxicology, Jena University Germany, Jena, Germany
| | | | - Andrea Giustina
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
- Endocrine Service, University of Brescia, Brescia, Italy
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20
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Gatto F, Florio T. Does pasireotide directly modulate skeletal muscle metabolism? Endocrine 2017; 57:6-8. [PMID: 28386722 DOI: 10.1007/s12020-017-1291-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 03/22/2017] [Indexed: 10/19/2022]
Affiliation(s)
- Federico Gatto
- Department of Internal Medicine and Center of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Tullio Florio
- Department of Internal Medicine and Center of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy.
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21
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Gatto F, Feelders RA, Franck SE, van Koetsveld PM, Dogan F, Kros JM, Neggers SJCMM, van der Lely AJ, Lamberts SWJ, Ferone D, Hofland LJ. In Vitro Head-to-Head Comparison Between Octreotide and Pasireotide in GH-Secreting Pituitary Adenomas. J Clin Endocrinol Metab 2017; 102:2009-2018. [PMID: 28323931 DOI: 10.1210/jc.2017-00135] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 03/08/2017] [Indexed: 11/19/2022]
Abstract
CONTEXT First-generation somatostatin analogs (SSAs), such as octreotide (OCT), are the first line medical therapy for acromegaly. Pasireotide (PAS), a newly developed SSA, has shown promising results in the treatment of acromegaly. OBJECTIVE To compare the antisecretory effect of OCT and PAS in primary cultures of growth hormone (GH)-secreting pituitary adenomas (GH-omas). To correlate responses with the adenoma somatostatin receptor (SSTR) profile. DESIGN The effect of OCT and PAS on GH (and PRL) secretion was tested in 33 GH-oma cultures. SSTR expression was evaluated in adenoma samples. SETTING AND PATIENTS Patients with acromegaly referred to the Erasmus Medical Center (Rotterdam, The Netherlands). INTERVENTIONS OCT and PAS treatment for 72 hours (10 nM). MAIN OUTCOME MEASURES GH (and PRL) concentrations in cell culture media. SSTR expression in adenoma samples. RESULTS The overall effect of OCT (-36.8%) and PAS (-37.1%) on GH secretion was superimposable. We identified three adenoma groups: PAS+ (PAS more effective than OCT), n = 6; PAS = OCT, n = 22; and OCT+ (OCT more effective than PAS), n = 5. PAS+ adenomas showed lower somatostatin receptor subtype (sst)2 messenger RNA (mRNA) and sst2/sst5 mRNA ratio, compared with the other groups (P < 0.05). PAS inhibited PRL hypersecretion more than OCT (P < 0.01). CONCLUSIONS Overall, OCT and PAS equally reduced GH secretion in vitro. Adenomas with lower sst2 mRNA expression and lower sst2/sst5 mRNA ratio were better responders to PAS compared with OCT. SSTR evaluation in GH-omas may become a tool for tailored SSA treatment in acromegaly.
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Affiliation(s)
- Federico Gatto
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Richard A Feelders
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
- Pituitary Center Rotterdam, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Sanne E Franck
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Peter M van Koetsveld
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Fadime Dogan
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Johan M Kros
- Pituitary Center Rotterdam, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
- Department of Pathology, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Sebastian J C M M Neggers
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
- Pituitary Center Rotterdam, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Aart-Jan van der Lely
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
- Pituitary Center Rotterdam, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Steven W J Lamberts
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Diego Ferone
- Section of Endocrinology, Department of Internal Medicine and Medical Specialties, Center of Excellence for Biomedical Research, University of Genova, Genova 16126, Italy
| | - Leo J Hofland
- Division of Endocrinology, Department of Internal Medicine, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
- Pituitary Center Rotterdam, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands
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22
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Abstract
First-generation somatostatin receptors ligands (SRL) are the mainstay in the medical treatment of acromegaly, however the percentage of patients controlled with these drugs significantly varies in the different studies. Many factors are involved in the resistance to SRL. In this review, we update the physiology of somatostatin and its receptors (sst), the use of SRL in the treatment of acromegaly and the factors involved in the response to these drugs. The SRL act through interaction with the sst, which up to now have been characterized as five subtypes. The first-generation SRL, octreotide and lanreotide, are considered sst2 specific and have biochemical response rates varying from 20 to 70%. Tumor volume reduction can be found in 36-75% of patients. Several factors may determine the response to these drugs, such as sst, AIP, E-cadherin, ZAC1, filamin A and β-arrestin expression in the somatotropinomas. In patients resistant to first-generation SRL, alternative medical treatment options include: SRL high dose regimens, SRL in combination with cabergoline or pegvisomant, or the use of pasireotide. Pasireotide is a next-generation SRL with a broader pattern of interaction with sst. In the light of the recent increase of treatment options in acromegaly and the deeper knowledge of the determinants of response to the current first-line therapy, a shift from a trial-and-error treatment to a personalized one could be possible.
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Affiliation(s)
- Monica R Gadelha
- Neuroendocrinology Research Center/Endocrinology Section, Medical School and Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Rua Prof. Rodolpho Paulo Rocco, 9th floor, Ilha do Fundão, Rio de Janeiro, 21941-913, Brazil.
- Neuroendocrinology Section and Molecular Genetics Laboratory, Secretaria Estadual de Saúde do Rio de Janeiro, Instituto Estadual do Cérebro Paulo Niemeyer, Rio de Janeiro, Brazil.
| | - Luiz Eduardo Wildemberg
- Neuroendocrinology Research Center/Endocrinology Section, Medical School and Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Rua Prof. Rodolpho Paulo Rocco, 9th floor, Ilha do Fundão, Rio de Janeiro, 21941-913, Brazil
- Neuroendocrinology Section and Molecular Genetics Laboratory, Secretaria Estadual de Saúde do Rio de Janeiro, Instituto Estadual do Cérebro Paulo Niemeyer, Rio de Janeiro, Brazil
| | - Marcello D Bronstein
- Neuroendocrine Unit, Division of Endocrinology and Metabolism, Hospital das Clinicas, University of Sao Paulo Medical School, São Paulo, Brazil
| | - Federico Gatto
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Diego Ferone
- Endocrinology Unit, Department of Internal Medicine and Medical Specialties and Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
- IRCCS AOU San Martino-IST Genoa, Genoa, Italy
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23
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Abstract
PURPOSE Pasireotide is the only pituitary targeted medication registered for the treatment of Cushing's disease. Drug efficacy data are largely based on a major prospective study in which the vast majority of patients had microadenomas. The purpose of this study was to summarize results of pasireotide treatment of ACTH secreting macroadenomas from our center. METHODS Retrospective review of data extracted from clinical files. RESULTS Three patients presented with large and invasive macroadenomas that required several surgical interventions and radiotherapy treatments. Patient 1 is a 57 year-old male who developed an extreme (27-fold) paradoxical response of urinary free cortisol (UFC) levels as measured 2 weeks after pasireotide institution, which increased further (71-fold) in response to dose increment but decreased to baseline levels after treatment interruption. Patient 2 is a 44 year old woman with a long standing (26 years) ACTH-secreting carcinoma metastatic to bone and after bilateral adrenalectomy. After an initial excellent response to pasireotide treatment, ACTH levels escaped suppression and a further rebound was noted 6 weeks after treatment interruption. Patient 3 is a 53 year old man that after escape from temozolomide therapy was started on pasireotide and rapidly responded by almost normalizing UFC excretion after 4 weeks, but returned to baseline UFC levels after four additional weeks of treatment. CONCLUSIONS We describe as yet unreported atypical responses to pasireotide treatment in patients with aggressive ACTH-secreting tumors. Increased vigilance is recommended during pasireotide treatment of such patients.
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Affiliation(s)
- Yona Greenman
- Institute of Endocrinology, Metabolism and Hypertension, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, 6 Weizmann Street, 64239, Tel Aviv, Israel.
| | - Naftali Stern
- Institute of Endocrinology, Metabolism and Hypertension, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, 6 Weizmann Street, 64239, Tel Aviv, Israel
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24
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Gatto F, Biermasz NR, Feelders RA, Kros JM, Dogan F, van der Lely AJ, Neggers SJCMM, Lamberts SWJ, Pereira AM, Ferone D, Hofland LJ. Low beta-arrestin expression correlates with the responsiveness to long-term somatostatin analog treatment in acromegaly. Eur J Endocrinol 2016; 174:651-62. [PMID: 26888629 DOI: 10.1530/eje-15-0391] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 02/17/2016] [Indexed: 12/18/2022]
Abstract
OBJECTIVE The high expression of somatostatin receptor subtype 2 (SSTR2 also known as sst2) usually present in growth hormone (GH)-secreting adenomas is the rationale for therapy with somatostatin analogs (SSAs) in acromegaly. Although SSTR2 expression is a good predictor for biochemical response to SSA treatment, we still face tumors resistant to SSAs despite high SSTR2 expression. Recently, beta-arrestins (β-arrestins) have been highlighted as key players in the regulation of SSTR2 function. DESIGN To investigate whether β-arrestins might be useful predictors of responsiveness to long-term SSA treatment in acromegaly, we retrospectively evaluated 35 patients with acromegaly who underwent adenomectomy in two referral centers in The Netherlands. METHODS β-arrestin mRNA levels were evaluated in adenoma samples, together with SSTR2 (and SSTR5) mRNA and protein expression. Biochemical response to long-term SSA treatment (median 12 months) was assessed in 32 patients. RESULTS β-arrestin 1 and 2 mRNA was significantly lower in adenoma tissues from patients who achieved insulin-like growth factor 1 normalization (P = 0.024 and P = 0.047) and complete biochemical control (P = 0.047 and P = 0.039). The SSTR2 mRNA was higher in SSA responder patients compared with the resistant ones (P = 0.026). This difference was more evident when analyzing the SSTR2/β-arrestin 1 and SSTR2/β-arrestin 2 ratio (P = 0.011 and P = 0.010). β-arrestin 1 and 2 expression showed a significant trend of higher median values from full responders, partial responders to resistant patients (P = 0.045 and P = 0.021, respectively). Interestingly, SSTR2 protein expression showed a strong inverse correlation with both β-arrestin 1 and 2 mRNA (ρ = -0.69, P = 0.0011 and ρ = -0.67, P = 0.0016). CONCLUSIONS Low β-arrestin expression and high SSTR2/β-arrestin ratio correlate with the responsiveness to long-term treatment with SSAs in patients with acromegaly.
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Affiliation(s)
- Federico Gatto
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands
| | - Nienke R Biermasz
- Department of MedicineDivision of Endocrinology and Center for Endocrine Tumors, Leiden University Medical Center, Leiden, The Netherlands
| | - Richard A Feelders
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands Pituitary Center RotterdamErasmus MC, Rotterdam, The Netherlands
| | - Johan M Kros
- PathologyErasmus MC, Rotterdam, The Netherlands Pituitary Center RotterdamErasmus MC, Rotterdam, The Netherlands
| | - Fadime Dogan
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands
| | - Aart-Jan van der Lely
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands Pituitary Center RotterdamErasmus MC, Rotterdam, The Netherlands
| | - Sebastian J C M M Neggers
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands Pituitary Center RotterdamErasmus MC, Rotterdam, The Netherlands
| | - Steven W J Lamberts
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands
| | - Alberto M Pereira
- Department of MedicineDivision of Endocrinology and Center for Endocrine Tumors, Leiden University Medical Center, Leiden, The Netherlands
| | - Diego Ferone
- EndocrinologyDepartment of Internal Medicine and Medical Specialties (DIMI) and Center of Excellence for Biomedical Research (CEBR), IRCCS AOU San Martino-IST, University of Genoa, Genoa, Italy
| | - Leo J Hofland
- Department of Internal MedicineDivision Endocrinology, Erasmus MC, Rotterdam, The Netherlands Pituitary Center RotterdamErasmus MC, Rotterdam, The Netherlands
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25
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Berardi R, Morgese F, Torniai M, Savini A, Partelli S, Rinaldi S, Caramanti M, Ferrini C, Falconi M, Cascinu S. Medical treatment for gastro-entero-pancreatic neuroendocrine tumours. World J Gastrointest Oncol 2016; 8:389-401. [PMID: 27096034 PMCID: PMC4824717 DOI: 10.4251/wjgo.v8.i4.389] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 02/16/2016] [Indexed: 02/05/2023] Open
Abstract
Gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs) represents a various family of rare tumours. Surgery is the first choice in GEP-NENs patients with localized disease whilst in the metastatic setting many other treatment options are available. Somatostatin analogues are indicated for symptoms control in functioning tumours. Furthermore they may be effective to inhibit tumour progression. GEP-NENs pathogenesis has been extensively studied in the last years therefore several driver mutations pathway genes have been identified as crucial factors in their tumourigenesis. GEP-NENs can over-express vascular endothelial growth factor (VEGF), basic-fibroblastic growth factor, transforming growth factor (TGF-α and -β), platelet derived growth factor (PDGF), insulin-like growth factor-1 (IGF-1) and their receptors PDGF receptor, IGF-1 receptor, epidermal growth factor receptor, VEGF receptor, and c-kit (stem cell factor receptor) that can be considered as potential targets. The availability of new targeted agents, such as everolimus and sunitinib that are effective in advanced and metastatic pancreatic neuroendocrine tumours, has provided new treatment opportunities. Many trials combing new drugs are ongoing.
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26
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Abstract
INTRODUCTION In nearly all cases, acromegaly is caused by excess GH from a pituitary adenoma, resulting in elevated circulating levels of GH and, subsequently, IGF-1. Treatment goals are to eliminate morbidity and restore the increased mortality to normal rates. Therapeutic strategies aim to minimize tumor mass and normalize GH and IGF-1 levels. Somatostatin analogues are the medical treatment of choice in acromegaly, as first-line or post-surgical therapy, and have proven efficacy in pituitary tumor volume reduction (TVR). METHODS Here we review the effects of somatostatin analogue therapy on pituitary tumor volume in patients with acromegaly. RESULTS TVR with somatostatin analogues may be mediated by direct anti-proliferative effects via activation of somatostatin receptors, or by indirect effects, such as angiogenesis inhibition, and is more pronounced when they are administered as first-line therapy. Various studies of first-line treatment with octreotide LAR have shown significant TVR in ≥73% of patients. First-line treatment with lanreotide Autogel has shown evidence of TVR, although more studies are needed. In a recent randomized, double-blind, 12-month trial in 358 medical-treatment-naïve acromegaly patients, significant TVR was achieved by 81% of patients administered pasireotide LAR and 77% administered octreotide LAR. Pre-operative somatostatin analogue therapy may also induce TVR and improve post-operative disease control compared with surgery alone. TVR is progressive with prolonged treatment, and decreased IGF-1 levels may be its best predictor, followed by age and degree of GH decrease. However, TVR does not always correlate with degree of biochemical control. CONCLUSION Somatostatin analogues (first- or second-line treatment) are the mainstay of medical therapy and, as first-line medical therapy, are associated with significant pituitary TVR in most patients.
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Affiliation(s)
- Annamaria Colao
- Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia, Università Federico II di Napoli, via S Pansini 5, 80131, Naples, Italy.
| | - Renata S Auriemma
- Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia, Università Federico II di Napoli, via S Pansini 5, 80131, Naples, Italy
| | - Rosario Pivonello
- Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia, Università Federico II di Napoli, via S Pansini 5, 80131, Naples, Italy
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27
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Samson SL. Pasireotide in Acromegaly: An Overview of Current Mechanistic and Clinical Data. Neuroendocrinology 2015; 102:8-17. [PMID: 25792118 DOI: 10.1159/000381460] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/04/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND Acromegaly is an insidious neuroendocrine disorder caused by hypersecretion of growth hormone (GH) by a somatotroph adenoma. Somatostatin receptor ligands (SRLs) are recommended as first-line medical therapy in patients for whom surgery has failed or is contraindicated. There are 5 known somatostatin receptor subtypes (SSTRs), 2 of which, i.e. SSTR2 and SSTR5, are expressed by a majority of somatotroph adenomas. The currently available SRLs, i.e. octreotide and lanreotide, primarily bind to SSTR2. Pasireotide (SOM230) is a new multireceptor-targeted SRL which has a broader binding profile and an increased affinity for SSTR1, 2, 3, and 5. METHODS PubMed searches were performed to identify all of the available published English language data on pasireotide with regard to the mechanism of action, in vitro effects, and clinical data. RESULTS Preclinical studies have demonstrated that pasireotide has a broader range of functional activity than octreotide. Recently, the efficacy of pasireotide in attenuating GH and insulin-like growth factor 1 (IGF-1) levels in patients with acromegaly has been evaluated in phase III clinical trials. Pasireotide demonstrated superiority over octreotide in achieving biochemical control (i.e. GH ≤2.5 µg/l and age- and sex-matched IGF-1 normalization) in patients with acromegaly, as well as significant efficacy in treating patients who were previously inadequately controlled on the maximum allowed doses of octreotide and lanreotide. Pasireotide-induced hyperglycemia was the most concerning adverse event but was reversible upon discontinuation of pasireotide. CONCLUSION The clinical data support pasireotide as a promising new therapy for the treatment of acromegaly, and the long-acting formulation was recently approved in the US and Europe for the treatment of acromegaly.
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Affiliation(s)
- Susan L Samson
- The Pituitary Center at Baylor St. Luke's Medical Center, Division of Endocrinology, Department of Medicine, Baylor College of Medicine, Houston, Tex., USA
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28
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Thompson GL, Canals M, Poole DP. Biological redundancy of endogenous GPCR ligands in the gut and the potential for endogenous functional selectivity. Front Pharmacol 2014; 5:262. [PMID: 25506328 PMCID: PMC4246669 DOI: 10.3389/fphar.2014.00262] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 11/12/2014] [Indexed: 01/27/2023] Open
Abstract
This review focuses on the existence and function of multiple endogenous agonists of the somatostatin and opioid receptors with an emphasis on their expression in the gastrointestinal tract. These agonists generally arise from the proteolytic cleavage of prepropeptides during peptide maturation or from degradation of peptides by extracellular or intracellular endopeptidases. In other examples, endogenous peptide agonists for the same G protein-coupled receptors can be products of distinct genes but contain high sequence homology. This apparent biological redundancy has recently been challenged by the realization that different ligands may engender distinct receptor conformations linked to different intracellular signaling profiles and, as such the existence of distinct ligands may underlie mechanisms to finely tune physiological responses. We propose that further characterization of signaling pathways activated by these endogenous ligands will provide invaluable insight into the mechanisms governing biased agonism. Moreover, these ligands may prove useful in the design of novel therapeutic tools to target distinct signaling pathways, thereby favoring desirable effects and limiting detrimental on-target effects. Finally we will discuss the limitations of this area of research and we will highlight the difficulties that need to be addressed when examining endogenous bias in tissues and in animals.
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Affiliation(s)
- Georgina L Thompson
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences Parkville, VIC, Australia
| | - Meritxell Canals
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences Parkville, VIC, Australia
| | - Daniel P Poole
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences Parkville, VIC, Australia ; Department of Anatomy and Neuroscience, The University of Melbourne Parkville, VIC, Australia
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29
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Neveu C, Dulin F, Lefranc B, Galas L, Calbrix C, Bureau R, Rault S, Chuquet J, Boutin JA, Guilhaudis L, Ségalas-Milazzo I, Vaudry D, Vaudry H, Santos JSDO, Leprince J. Molecular basis of agonist docking in a human GPR103 homology model by site-directed mutagenesis and structure-activity relationship studies. Br J Pharmacol 2014; 171:4425-39. [PMID: 24913445 DOI: 10.1111/bph.12808] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 04/04/2014] [Accepted: 05/15/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND AND PURPOSE The neuropeptide 26RFa and its cognate receptor GPR103 are involved in the control of food intake and bone mineralization. Here, we have tested, experimentally, the predicted ligand-receptor interactions by site-directed mutagenesis of GPR103 and designed point-substituted 26RFa analogues. EXPERIMENTAL APPROACH Using the X-ray structure of the β2 -adrenoceptor, a 3-D molecular model of GPR103 has been built. The bioactive C-terminal octapeptide 26RFa(19-26) , KGGFSFRF-NH2 , was docked in this GPR103 model and the ligand-receptor complex was submitted to energy minimization. KEY RESULTS In the most stable complex, the Phe-Arg-Phe-NH2 part was oriented inside the receptor cavity, whereas the N-terminal Lys residue remained outside. A strong intermolecular interaction was predicted between the Arg(25) residue of 26RFa and the Gln(125) residue located in the third transmembrane helix of GPR103. To confirm this interaction experimentally, we tested the ability of 26RFa and Arg-modified 26RFa analogues to activate the wild-type and the Q125A mutant receptors transiently expressed in CHO cells. 26RFa (10(-6) M) enhanced [Ca(2+) ]i in wild-type GPR103-transfected cells, but failed to increase [Ca(2+) ]i in Q125A mutant receptor-expressing cells. Moreover, asymmetric dimethylation of the side chain of arginine led to a 26RFa analogue, [ADMA(25) ]26RFa(20-26) , that was unable to activate the wild-type GPR103, but antagonized 26RFa-evoked [Ca(2+) ]i increase. CONCLUSION AND IMPLICATIONS Altogether, these data provide strong evidence for a functional interaction between the Arg(25) residue of 26RFa and the Gln(125) residue of GPR103 upon ligand-receptor activation, which can be exploited for the rational design of potent GPR103 agonists and antagonists.
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Affiliation(s)
- C Neveu
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Neurotrophic Factors and Neuronal Differentiation Team, Institute for Research and Innovation in Biomedicine (IRIB); Cell Imaging Platform of Normandy (PRIMACEN), IRIB; Normandie Univ, France
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30
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Maina T, Cescato R, Waser B, Tatsi A, Kaloudi A, Krenning EP, de Jong M, Nock BA, Reubi JC. [111In-DOTA]LTT-SS28, a First Pansomatostatin Radioligand for in Vivo Targeting of Somatostatin Receptor-Positive Tumors. J Med Chem 2014; 57:6564-71. [DOI: 10.1021/jm500581d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Theodosia Maina
- Molecular
Radiopharmacy, INRASTES, National Center for Scientific Research “Demokritos”, GR-153 10 Athens, Greece
| | - Renzo Cescato
- Cell
Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
| | - Beatrice Waser
- Cell
Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
| | - Aikaterini Tatsi
- Molecular
Radiopharmacy, INRASTES, National Center for Scientific Research “Demokritos”, GR-153 10 Athens, Greece
| | - Aikaterini Kaloudi
- Molecular
Radiopharmacy, INRASTES, National Center for Scientific Research “Demokritos”, GR-153 10 Athens, Greece
| | - Eric P. Krenning
- Department
of Nuclear Medicine, Erasmus MC, 3015 CE Rotterdam, The Netherlands
| | - Marion de Jong
- Department
of Nuclear Medicine, Erasmus MC, 3015 CE Rotterdam, The Netherlands
- Department
of Radiology, Erasmus MC, 3015 CE Rotterdam, The Netherlands
| | - Berthold A. Nock
- Molecular
Radiopharmacy, INRASTES, National Center for Scientific Research “Demokritos”, GR-153 10 Athens, Greece
| | - Jean Claude Reubi
- Cell
Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
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31
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Prasad V, Bodei L, Kidd M, Modlin IM. Whither peptide receptor radionuclide therapy for neuroendocrine tumors: an Einsteinian view of the facts and myths. Eur J Nucl Med Mol Imaging 2014; 41:1825-30. [DOI: 10.1007/s00259-014-2780-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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32
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Schulz S, Lehmann A, Kliewer A, Nagel F. Fine-tuning somatostatin receptor signalling by agonist-selective phosphorylation and dephosphorylation: IUPHAR Review 5. Br J Pharmacol 2014; 171:1591-9. [PMID: 24328848 PMCID: PMC3966740 DOI: 10.1111/bph.12551] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 10/08/2013] [Accepted: 10/31/2013] [Indexed: 12/28/2022] Open
Abstract
The biological actions of somatostatin are mediated by a family of five GPCRs, named sst1 to sst5 . Somatostatin receptors exhibit equally high-binding affinities to their natural ligand somatostatin-14 and largely overlapping distributions. The overexpression of somatostatin receptors in human tumours is the molecular basis for diagnostic and therapeutic application of the stable somatostatin analogues octreotide, lanreotide and pasireotide. The efficiency of somatostatin receptor signalling is tightly regulated and ultimately limited by the coordinated phosphorylation and dephosphorylation of intracellular carboxyl-terminal serine and threonine residues. Here, we review and discuss recent progress in the generation and application of phosphosite-specific antibodies for human sst2 and sst5 receptors. These phosphosite-specific antibodies are unique tools to monitor the spatial and temporal dynamics of receptors phosphorylation and dephosphorylation. Using a combined approach of phosphosite-specific antibodies and siRNA knock-down screening, relevant kinases and phosphatases were identified. Emerging evidence suggests distinct mechanisms of agonist-selective fine-tuning for individual somatostatin receptors. The recently uncovered differences in phosphorylation and dephosphorylation of these receptors may hence be of physiological significance in mediating responses to acute, persistent or repeated stimuli in a variety of target tissues.
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Affiliation(s)
- Stefan Schulz
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-UniversityJena, Germany
| | - Andreas Lehmann
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-UniversityJena, Germany
| | - Andrea Kliewer
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-UniversityJena, Germany
| | - Falko Nagel
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-UniversityJena, Germany
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33
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Chalabi M, Duluc C, Caron P, Vezzosi D, Guillermet-Guibert J, Pyronnet S, Bousquet C. Somatostatin analogs: does pharmacology impact antitumor efficacy? Trends Endocrinol Metab 2014; 25:115-27. [PMID: 24405892 DOI: 10.1016/j.tem.2013.11.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 11/05/2013] [Accepted: 11/15/2013] [Indexed: 01/17/2023]
Abstract
Somatostatin is an endogenous inhibitor of secretion and cell proliferation. These features render somatostatin a logical candidate for the management of neuroendocrine tumors that express somatostatin receptors. Synthetic somatostatin analogs (SSAs) have longer half-lives than somatostatin, but have similar activities, and are used for the treatment of these types of disorders. Interest has focused on novel multireceptor analogs with broader affinity to several of the five somatostatin receptors, thereby presenting putatively higher antitumor activities. Recent evidence indicates that SSAs cannot be considered mimics of native somatostatin in regulating signaling pathways downstream of receptors. Here we review this knowledge, discuss the concept of biased agonism, and highlight what considerations need to be taken into account for the optimal clinical use of SSAs.
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Affiliation(s)
- Mounira Chalabi
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France
| | - Camille Duluc
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France
| | - Philippe Caron
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France; Service d'Endocrinologie et Maladies Métaboliques, Pôle Cardio-Vasculaire et Métabolique, Centre Hospitalier Universitaire (CHU) Larrey, 31059 Toulouse, France
| | - Delphine Vezzosi
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France; Service d'Endocrinologie et Maladies Métaboliques, Pôle Cardio-Vasculaire et Métabolique, Centre Hospitalier Universitaire (CHU) Larrey, 31059 Toulouse, France
| | - Julie Guillermet-Guibert
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France
| | - Stéphane Pyronnet
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France
| | - Corinne Bousquet
- Institut National de la Santé et de la Recherche Médicale (INSERM), Unité Mixte de Recherche (UMR) 1037, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer (TOUCAN), 31432 Toulouse, France; Université Toulouse III Paul Sabatier, 31062 Toulouse, France.
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Tatsi A, Maina T, Cescato R, Waser B, Krenning EP, de Jong M, Cordopatis P, Reubi JC, Nock BA. [DOTA]Somatostatin-14 analogs and their (111)In-radioligands: effects of decreasing ring-size on sst1-5 profile, stability and tumor targeting. Eur J Med Chem 2013; 73:30-7. [PMID: 24378707 DOI: 10.1016/j.ejmech.2013.12.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 11/27/2013] [Accepted: 12/08/2013] [Indexed: 12/23/2022]
Abstract
Multiple somatostatin receptor (sst)-subtype expression has been manifested in several human tumors. Hence, the availability of radiopeptides retaining the full pansomatostatin profile of the native hormone (SS14) is expected to increase the sensitivity and broaden the clinical indications of currently applied sst2-preferring cyclic octapeptide radioligands, like OctreoScan(®) ([(111)In-DTPA]octreotide). On the other hand, SS14 has been excluded from clinical use due to its rapid in vivo degradation. We herein present a small library of seven novel cyclic SS14-mimics carrying at their N-terminus the universal chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) for stable binding of medically useful radiometals, like (111)In. By decreasing the number of amino acids composing the ring in their structure from 12 up to 6 AA, we induced important changes in key-biological parameters in vitro and in vivo. In particular, we observed unexpected changes and even total loss of sst1-5-affinity (6AA-ring), as well as weaker sst2-internalization efficacy as the ring size decreased. In contrast, in vivo stability increased with decreasing ring size, reaching its maximum in the 6AA-ring analogs. Interestingly, only the 12AA- and 9AA-ring members of this series showed sst2-specific uptake in AR4-2J tumors in mice revealing the prominent role of ring size on the biological response of tested SS14-derived radioligands.
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Affiliation(s)
- Aikaterini Tatsi
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, GR-153 10 Athens, Greece; Department of Radiology, Erasmus MC, 3015 GD, Rotterdam, The Netherlands
| | - Theodosia Maina
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, GR-153 10 Athens, Greece
| | - Renzo Cescato
- Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
| | - Beatrice Waser
- Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
| | - Eric P Krenning
- Department of Nuclear Medicine, Erasmus MC, 3015 GD, Rotterdam, The Netherlands
| | - Marion de Jong
- Department of Nuclear Medicine, Erasmus MC, 3015 GD, Rotterdam, The Netherlands; Department of Radiology, Erasmus MC, 3015 GD, Rotterdam, The Netherlands
| | - Paul Cordopatis
- Department of Pharmacy, University of Patras, GR-26500 Patras, Greece
| | - Jean-Claude Reubi
- Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland
| | - Berthold A Nock
- Molecular Radiopharmacy, INRASTES, NCSR "Demokritos", Ag. Paraskevi Attikis, GR-153 10 Athens, Greece.
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Reubi JC, Schonbrunn A. Illuminating somatostatin analog action at neuroendocrine tumor receptors. Trends Pharmacol Sci 2013; 34:676-88. [PMID: 24183675 DOI: 10.1016/j.tips.2013.10.001] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/26/2013] [Accepted: 10/03/2013] [Indexed: 02/08/2023]
Abstract
Somatostatin analogs for the diagnosis and therapy of neuroendocrine tumors (NETs) have been used in clinical applications for more than two decades. Five somatostatin receptor subtypes have been identified and molecular mechanisms of somatostatin receptor signaling and regulation have been elucidated. These advances increased understanding of the biological role of each somatostatin receptor subtype, their distribution in NETs, as well as agonist-specific regulation of receptor signaling, internalization, and phosphorylation, particularly for the sst2 receptor subtype, which is the primary target of current somatostatin analog therapy for NETs. Various hypotheses exist to explain differences in patient responsiveness to somatostatin analog inhibition of tumor secretion and growth as well as differences in the development of tumor resistance to therapy. In addition, we now have a better understanding of the action of both first generation (octreotide, lanreotide, Octreoscan) and second generation (pasireotide) FDA-approved somatostatin analogs, including the biased agonistic character of some agonists. The increased understanding of somatostatin receptor pharmacology provides new opportunities to design more sophisticated assays to aid the future development of somatostatin analogs with increased efficacy.
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Affiliation(s)
- Jean Claude Reubi
- Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, Switzerland.
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Veenstra MJ, de Herder WW, Feelders RA, Hofland LJ. Targeting the somatostatin receptor in pituitary and neuroendocrine tumors. Expert Opin Ther Targets 2013; 17:1329-43. [DOI: 10.1517/14728222.2013.830711] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Lesma G, Cecchi R, Cagnotto A, Gobbi M, Meneghetti F, Musolino M, Sacchetti A, Silvani A. Tetrahydro-β-carboline-based spirocyclic lactam as type II' β-turn: application to the synthesis and biological evaluation of somatostatine mimetics. J Org Chem 2013; 78:2600-10. [PMID: 23409740 DOI: 10.1021/jo302737j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The synthesis of novel spirocyclic lactams, embodying D-tryptophan (Trp) amino acid as the central core and acting as peptidomimetics, is presented. It relies on the strategic combination of Seebach's self-reproduction of chirality chemistry and Pictet-Spengler condensation as key steps. Investigation of the conformational behavior by molecular modeling, X-ray crystallography, and NMR and IR spectroscopies suggests very stable and highly predictable type II' β-turn conformations for all compounds. Relying on this feature, we also pursued their application to two potential mimetics of the hormone somatostatin, a pharmaceutically relevant natural peptide, which contains a Trp-based type II' β-turn pharmacophore.
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Affiliation(s)
- Giordano Lesma
- Dipartimento di Chimica, Università degli Studi di Milano, via C. Golgi 19, 20133 Milano, Italy
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Somnay Y, Chen H, Kunnimalaiyaan M. Synergistic effect of pasireotide and teriflunomide in carcinoids in vitro. Neuroendocrinology 2013; 97:183-92. [PMID: 22965070 PMCID: PMC3546174 DOI: 10.1159/000341810] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 07/09/2012] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIM Somatostatin (SST) analogs are mainstay for controlling tumor proliferation and hormone secretion in carcinoid patients. Recent data suggest that extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation may potentiate the anti-tumor effects of SST analogs in carcinoids. Additionally, ERK1/2 phosphorylating agents have been shown to suppress biomarker expression in carcinoids. Thus, Raf-1/MEK/ERK1/2 pathway activating drugs may be synergistic with SST analogs such as pasireotide (SOM230), which may be more effective than others in its class given its elevated receptor affinity and broader binding spectrum. Here, we investigate the effects of SOM230 in combination with teriflunomide (TFN), a Raf-1 activator, in a human carcinoid cell line. METHODS Human pancreatic carcinoid cells (BON) were incubated in TFN, SOM230 or a combination. Cell proliferation was measured using a rapid colorimetric assay. Western analysis was performed to analyze expression levels of achaete-scute complex-like 1 (ASCL1), chromogranin A (CgA), phosphorylated and total ERK1/2, and markers for apoptosis. RESULTS Combination treatment with SOM230 and TFN reduced cell growth beyond the additive effect of either drug alone. Combination indices (CI) fell below 1, thus quantifiably verifying synergy between both drugs as per the Chou-Talalay CI scale. Combined treatment also reduced ASCL1 and CgA expression beyond the additive effect of either drug alone. Furthermore, it increased levels of phosphorylated ERK1/2, cleaved poly(ADP)-ribose polymerase and caspase-3, and reduced levels of anti-apoptotic biomarkers. Elevated phosphorylated ERK1/2 expression following combination therapy may underlie the synergistic interaction between the two drugs. CONCLUSION Since efficacy is achieved at lower doses, combination therapy may palliate symptoms at low toxicity levels. Because each drug has already been evaluated in clinical trials, combinatorial drug trials are warranted.
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Affiliation(s)
- Yash Somnay
- University of Wisconsin School of Medicine and Public Health, Endocrine Surgery Research Laboratories, Department of Surgery, Madison, USA
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Gigoux V, Fourmy D. Acting on Hormone Receptors with Minimal Side Effect on Cell Proliferation: A Timely Challenge Illustrated with GLP-1R and GPER. Front Endocrinol (Lausanne) 2013; 4:50. [PMID: 23641235 PMCID: PMC3638125 DOI: 10.3389/fendo.2013.00050] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 04/10/2013] [Indexed: 12/18/2022] Open
Abstract
G protein-coupled receptors (GPCRs) constitute a large family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and cellular responses. GPCR are involved in a wide variety of physiological processes, including in the neuroendocrine system. GPCR are also involved in many diseases and are the target of 30% of marketed medicinal drugs. Whereas the majority of the GPCR-targeting drugs have proved their therapeutic benefit, some of them were associated with undesired effects. We develop two examples of used drugs whose therapeutic benefits are tarnished by carcinogenesis risks. The chronic administration of glucagon-like peptide-1 (GLP-1) analogs widely used to treat type-2 diabetes was associated with an increased risk of pancreatic or thyroid cancers. The long-term treatment with the estrogen antagonist tamoxifen, developed to target breast cancer overexpressing estrogen receptors ER, presents agonist activity on the G protein-coupled estrogen receptor which is associated with an increased incidence of endometrial cancer and breast cancer resistance to hormonotherapy. We point out and discuss the need of pharmacological studies to understand and overcome the undesired effects associated with the chronic administration of GPCR ligands. In fact, biological effects triggered by GPCR often result from the activation of multiple intracellular signaling pathways. Deciphering which signaling networks are engaged following GPCR activation appears to be primordial to unveil their contribution in the physiological and physiopathological processes. The development of biased agonists to elucidate the role of the different signaling mechanisms mediated by GPCR activation will allow the generation of new therapeutic agents with improved efficacy and reduced side effects. In this regard, the identification of GLP-1R biased ligands promoting insulin secretion without inducing pro-tumoral effects would offer therapeutic benefit.
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Affiliation(s)
- Véronique Gigoux
- Université de Toulouse, Université Paul SabatierToulouse, France
- *Correspondence: Véronique Gigoux, CHU Rangueil – INSERM, Université de Toulouse, Université Paul Sabatier, EA4552, 1 Avenue Jean Poulhès, BP 84225, 31432 Toulouse Cedex 4, France. e-mail:
| | - Daniel Fourmy
- Université de Toulouse, Université Paul SabatierToulouse, France
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Forssell-Aronsson E, Spetz J, Ahlman H. Radionuclide therapy via SSTR: future aspects from experimental animal studies. Neuroendocrinology 2013; 97:86-98. [PMID: 22572526 DOI: 10.1159/000336086] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 12/11/2011] [Indexed: 12/24/2022]
Abstract
There is need for better therapeutic options for neuroendocrine tumours. The aim of this review was to summarize results of experimental animal studies and raise ideas for future radionuclide therapy based on high expression of somatostatin (SS) receptors by many neuroendocrine tumours. In summary, one of the major options is individualized treatment for each patient, including choice of SS analogues, radionuclides and treatment schedules. Other options are methods to increase the treatment effect on tumour tissue (increasing tumour uptake and retention by upregulation of receptor expression and avoiding saturation of receptor binding), methods to increase the tumour tissue response (by choice of radionuclides, SS analogues or combined therapies), and methods to reduce side effects (diminished uptake and retention in critical organs and reduced normal tissue response). Furthermore, combination therapy with other radiopharmaceuticals, cytotoxic drugs or radiosensitizers can be considered to enhance the effects of radiolabelled SS analogues.
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Affiliation(s)
- Eva Forssell-Aronsson
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Centre, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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Peverelli E, Busnelli M, Vitali E, Giardino E, Galés C, Lania AG, Beck-Peccoz P, Chini B, Mantovani G, Spada A. Specific roles of G(i) protein family members revealed by dissecting SST5 coupling in human pituitary cells. J Cell Sci 2012. [PMID: 23178946 DOI: 10.1242/jcs.116434] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite intensive investigation over the past 20 years, the specific role played by individual G(i) protein family members in mediating complex cellular effects is still largely unclear. Therefore, we investigated the role of specific G(i) proteins in mediating somatostatin (SS) effects in somatotroph cells. Because our previous data showed that SS receptor type 5 (SST5) carrying a spontaneous R240W mutation in the third intracellular loop had a similar ability to inhibit intracellular cAMP levels to the wild-type protein but failed to mediate inhibition of growth hormone (GH) release and cell proliferation, we used this model to check specific receptor-G-protein coupling by a bioluminescent resonance energy transfer analysis. In HEK293 cells, wild-type SST5 stimulated the activation of Gα(i1-3) and Gα(oA), B, whereas R240W SST5 maintained the ability to activate Gα(i1-3) and Gα(oB), but failed to activate the splicing variant Gα(oA). To investigate the role of the selective deficit in Gα(oA) coupling, we co-transfected human adenomatous somatotrophs with SST5 and a pertussis toxin (PTX)-resistant Gα(oA) (Gα(oA(PTX-r))) protein. In PTX-treated cells, Gα(oA(PTX-r)) rescued the ability of the selective SST5 analog BIM23206 to inhibit extracellular signal-related kinase 1/2 (ERK1/2) phosphorylation, GH secretion and intracellular cAMP levels. Moreover, we demonstrated that silencing of Gα(oA) completely abolished SST5-mediated inhibitory effects on GH secretion and ERK1/2 phosphorylation, but not on cAMP levels. In conclusion, by analysing the coupling specificity of human SST5 to individual Gα(i) and Gα(o) subunits, we identified a crucial role for Gα(oA) signalling in human pituitary cells.
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Affiliation(s)
- Erika Peverelli
- Endocrinology and Diabetology Unit, Department of Clinical Sciences and Community Health, University of Milan, Fondazione IRCCS Ca' Granda Policlinico, 20122-Milan, Italy
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Fani M, Braun F, Waser B, Beetschen K, Cescato R, Erchegyi J, Rivier JE, Weber WA, Maecke HR, Reubi JC. Unexpected Sensitivity of sst2 Antagonists to N-Terminal Radiometal Modifications. J Nucl Med 2012; 53:1481-9. [DOI: 10.2967/jnumed.112.102764] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Fani M, Maecke HR. Radiopharmaceutical development of radiolabelled peptides. Eur J Nucl Med Mol Imaging 2012; 39 Suppl 1:S11-30. [PMID: 22388624 DOI: 10.1007/s00259-011-2001-z] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Receptor targeting with radiolabelled peptides has become very important in nuclear medicine and oncology in the past few years. The overexpression of many peptide receptors in numerous cancers, compared to their relatively low density in physiological organs, represents the molecular basis for in vivo imaging and targeted radionuclide therapy with radiolabelled peptide-based probes. The prototypes are analogs of somatostatin which are routinely used in the clinic. More recent developments include somatostatin analogs with a broader receptor subtype profile or with antagonistic properties. Many other peptide families such as bombesin, cholecystokinin/gastrin, glucagon-like peptide-1 (GLP-1)/exendin, arginine-glycine-aspartic acid (RGD) etc. have been explored during the last few years and quite a number of potential radiolabelled probes have been derived from them. On the other hand, a variety of strategies and optimized protocols for efficient labelling of peptides with clinically relevant radionuclides such as (99m)Tc, M(3+) radiometals ((111)In, (86/90)Y, (177)Lu, (67/68)Ga), (64/67)Cu, (18)F or radioisotopes of iodine have been developed. The labelling approaches include direct labelling, the use of bifunctional chelators or prosthetic groups. The choice of the labelling approach is driven by the nature and the chemical properties of the radionuclide. Additionally, chemical strategies, including modification of the amino acid sequence and introduction of linkers/spacers with different characteristics, have been explored for the improvement of the overall performance of the radiopeptides, e.g. metabolic stability and pharmacokinetics. Herein, we discuss the development of peptides as radiopharmaceuticals starting from the choice of the labelling method and the conditions to the design and optimization of the peptide probe, as well as some recent developments, focusing on a selected list of peptide families, including somatostatin, bombesin, cholecystokinin/gastrin, GLP-1/exendin and RGD.
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Affiliation(s)
- Melpomeni Fani
- Department of Nuclear Medicine, University Hospital Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany.
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Tatsi A, Maina T, Cescato R, Waser B, Krenning EP, de Jong M, Cordopatis P, Reubi JC, Nock BA. [111In-DOTA]Somatostatin-14 analogs as potential pansomatostatin-like radiotracers - first results of a preclinical study. EJNMMI Res 2012; 2:25. [PMID: 22682002 PMCID: PMC3407795 DOI: 10.1186/2191-219x-2-25] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/09/2012] [Indexed: 02/04/2023] Open
Abstract
Background In this study, we report on the synthesis, radiolabeling, and biological evaluation of two new somatostatin-14 (SS14) analogs, modified with the universal chelator DOTA. We were interested to investigate if and to what extent such radiotracer prototypes may be useful for targeting sst1-5-expressing tumors in man but, most importantly, to outline potential drawbacks and benefits associated with their use. Methods AT1S and AT2S (DOTA-Ala1-Gly2-c[Cys3-Lys4-Asn5-Phe6-Phe7-Trp8/DTrp8-Lys9-Thr10-Phe11-Thr12-Ser13-Cys14-OH], respectively) were synthesized on the solid support and labeled with 111In. The sst1-5 affinity profile of AT1S/AT2S was determined by receptor autoradiography using [Leu8,dTrp22,125I-Tyr25]SS28 as radioligand. The ability of AT2S to stimulate sst2 or sst3 internalization was qualitatively analyzed by an immunofluorescence-based internalization assay using hsst2- or hsst3-expressing HEK293 cells. Furthermore, the internalization of the radioligands [111In]AT1S and [111In]AT2S was studied at 37 °C in AR4-2J cells endogenously expressing sst2. The in vivo stability of [111In]AT1S and [111In]AT2S was tested by high-performance liquid chromatography analysis of mouse blood collected 5 min after radioligand injection, and biodistribution was studied in normal mice. Selectively for [111In]AT2S, biodistribution was further studied in SCID mice bearing AR4-2J, HEK293-hsst2A+, -hsst3+ or -hsst5+ tumors. Results The new SS14-derived analogs were obtained by solid phase peptide synthesis and were easily labeled with 111In. Both SS14 conjugates, AT1S, and its DTrp8 counterpart, AT2S, showed a pansomatostatin affinity profile with the respective hsst1-5 IC50 values in the lower nanomolar range. In addition, AT2S behaved as an agonist for sst2 and sst3 since it stimulated receptor internalization. The 111In radioligands effectively and specifically internalized into rsst2A-expressing AR4-2J cells with [111In]AT2S internalizing faster than [111In]AT1S. Ex vivo mouse blood analysis revealed a rapid degradation of both radiopeptides in the bloodstream with the DTrp8 analog showing higher stability. Biodistribution results in healthy mice were consistent with these findings with only [111In]AT2S showing specific uptake in the sst2-rich pancreas. Biodistribution of [111In]AT2S in tumor-bearing mice revealed receptor-mediated uptake in the AR4-2J (1.82 ± 0.36 %ID/g - block 0.21 ± 0.17 %ID/g at 4 h post injection (pi)), the HEK293-hsst2A+ (1.49 ± 0.2 %ID/g - block 0.27 ± 0.20 %ID/g at 4 h pi), the HEK293-hsst3+ (1.24 ± 0.27 %ID/g - block 0.32 ± 0.06 %ID/g at 4 h pi), and the HEK293-hsst5+ tumors (0.41 ± 0.12 %ID/g - block 0.22 ± 0.006 %ID/g at 4 h pi). Radioactivity washed out from blood and background tissues via the kidneys. Conclusions This study has revealed that the native SS14 structure can indeed serve as a motif for the development of promising pansomatostatin-like radiotracers. Further peptide stabilization is required to increase in vivo stability and, consequently, to enhance in vivo delivery and tumor targeting.
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Affiliation(s)
- Aikaterini Tatsi
- Molecular Radiopharmacy, Institute of Radioisotopes - Radiodiagnostic Products, National Center for Scientific Research "Demokritos", 153 10 Ag, Paraskevi Attikis, Athens, GR-153 10, Greece.
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Abstract
Somatostatin (SS) and dopamine (DA) receptors have been highlighted as two critical regulators in the negative control of hormonal secretion in a wide group of human endocrine tumors. Both families of receptors belong to the superfamily of G protein-coupled receptors and share a number of structural and functional characteristics. Because of the generally reported high expression of somatostatin receptors (SSTRs) in neuroendocrine tumors (NET), somatostatin analogs (SSA) have a pronounced role in the medical therapy for this class of tumors, especially pituitary adenomas and well-differentiated gastroenteropancreatic NET (GEP NET). Moreover, NET express not only SSTR but also frequently dopamine receptors (DRs), and DA agonists targeting the D(2) receptor (D(2)) have been demonstrated to be effective in controlling hormone secretion and cell proliferation in in vivo and in vitro studies. The treatment with SSAs combined with DA agonists has already been demonstrated efficacious in a subgroup of patients with GH-secreting pituitary adenomas and few reported cases of carcinoids. The recent availability of new selective and universal SSA and DA agonists, as well as the chimeric SS/DA compounds, may shed new light on the potential role of SSTR and D(2) as combined targets for biotherapy in NET. This review provides an overview of the latest studies evaluating the expression of SSTR and DR in NET, focusing on their co-expression and the possible clinical implications of such co-expression. Moreover, the most recent insights in SSTR and D(2) pathophysiology and the future perspectives for treatment with SSA, DA agonists, and SS/DA chimeric compounds are discussed.
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Affiliation(s)
- Federico Gatto
- Division of Endocrinology, Department of Internal Medicine, Erasmus Medical Center, Room Ee530b, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
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Evaluation of copper-64-labeled somatostatin agonists and antagonist in SSTr2-transfected cell lines that are positive and negative for p53: implications for cancer therapy. Nucl Med Biol 2011; 39:187-97. [PMID: 22056254 DOI: 10.1016/j.nucmedbio.2011.08.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 08/10/2011] [Accepted: 08/14/2011] [Indexed: 12/19/2022]
Abstract
OBJECTIVES Radiolabeled somatostatin analogs have become important agents for molecular imaging and targeted radiotherapy of somatostatin receptor-positive tumors. Here we determine the effect of the tumor suppressor protein, p53, on trafficking (64)Cu to tumor cell nuclei from DOTA vs. CB-TE2A-conjugated agonist Y3-TATE and the antagonist (64)Cu-CB-TE2A-sst2-ANT in cell lines that are positive or negative for p53. METHODS Receptor binding, internalization, cyclic adenosine monophosphate (cAMP) and nuclear localization studies were performed with the somatostatin receptor subtype 2 (SSTr2) agonists, (64)Cu-CB-TE2A-Y3-TATE and (64)Cu-DOTA-Y3-TATE vs. antagonist, (64)Cu-CB-TE2A-sst2-ANT, in SSTr2-transfected p53 +/+ and -/- HCT116 colorectal carcinoma cells. RESULTS The antagonist, (64)Cu-CB-TE2A-sst2-ANT, bound 8-9-fold more SSTr2 binding sites than did the (64)Cu-labeled agonists. (64)Cu-CB-TE2A-Y3-TATE was more efficiently internalized than (64)Cu-DOTA-Y3-TATE, while (64)Cu-CB-TE2A-sst2-ANT showed lower yet significant levels of internalization. CB-TE2A-Y3-TATE acted as a full agonist, inhibiting cAMP production, whereas CB-TE2A-sst2-ANT showed no inhibition of cAMP production. The (64)Cu from agonists (64)Cu-DOTA-Y3-TATE and (64)Cu-CB-TE2A-Y3-TATE showed greater nuclear localization at 24 h in p53 +/+ vs. -/- cells; however, there was no difference in the levels of (64)Cu from the antagonist based on p53 status. Surprisingly, the DOTA and CB-TE2A-conjugated agonists showed similar nuclear localization in the p53 +/+ and -/- cells, suggesting no difference in (64)Cu release from these chelators in the HCT116 cell lines. CONCLUSION Based on these in vitro data, the agonist (64)Cu-CB-TE2A-Y3-TATE demonstrates the most promise as an agent for targeted radiotherapy in p53 positive, SSTr2-positive tumors.
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Cakir M, Dworakowska D, Grossman A. Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 1--molecular pathways. J Cell Mol Med 2011; 14:2570-84. [PMID: 20629989 PMCID: PMC4373477 DOI: 10.1111/j.1582-4934.2010.01125.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Neuroendocrine tumours (NETs) may occur at many sites in the body although the majority occur within the gastroenteropancreatic axis. Non-gastroenteropancreatic NETs encompass phaeochromocytomas and paragangliomas, medullary thyroid carcinoma, anterior pituitary tumour, broncho-pulmonary NETs and parathyroid tumours. Like most endocrine tumours, NETs also express somatostatin (SST) receptors (subtypes 1–5) whose ligand SST is known to inhibit endocrine and exocrine secretions and have anti-tumour effects. In the light of this knowledge, the idea of using SST analogues in the treatment of NETs has become increasingly popular and new studies have centred upon the development of new SST analogues. We attempt to review SST receptor (SSTR) biology primarily in neuroendocrine tissues, focusing on pituitary tumours. A full data search was performed through PubMed over the years 2000–2009 with keywords ‘somatostatin, molecular biology, somatostatin receptors, somatostatin signalling, NET, pituitary’ and all relevant publications have been included, together with selected publications prior to that date. SSTR signalling in non-neuroendocrine solid tumours is beyond the scope of this review. SST is a potent anti-proliferative and anti-secretory agent for some NETs. The successful therapeutic use of SST analogues in the treatment of these tumours depends on a thorough understanding of the diverse effects of SSTR subtypes in different tissues and cell types. Further studies will focus on critical points of SSTR biology such as homo- and heterodimerization of SSTRs and the differences between post-receptor signalling pathways of SSTR subtypes.
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Affiliation(s)
- Mehtap Cakir
- Selcuk University, Meram School of Medicine, Division of Endocrinology and Metabolism, Konya, Turkey.
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Maecke HR, Reubi JC. Somatostatin receptors as targets for nuclear medicine imaging and radionuclide treatment. J Nucl Med 2011; 52:841-4. [PMID: 21571797 DOI: 10.2967/jnumed.110.084236] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Radiolabeled peptides have been an important class of compounds in radiopharmaceutical sciences and nuclear medicine for more than 20 years. Despite strong research efforts, only somatostatin-based radiopeptides have a real impact on patient care, diagnostically and therapeutically. [(111)In-diethylenetriaminepentaacetic acid(0)]octreotide is commercially available for imaging. Imaging was highly improved by the introduction of PET radionuclides such as (68)Ga, (64)Cu, and (18)F. Two peptides are successfully used in targeted radionuclide therapy when bound to DOTA and labeled with (90)Y and (177)Lu.
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Affiliation(s)
- Helmut R Maecke
- Department of Nuclear Medicine, University Hospital Freiburg, Freiburg, Germany.
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Seebach D, Lukaszuk A, Patora-Komisarska K, Podwysocka D, Gardiner J, Ebert MO, Reubi JC, Cescato R, Waser B, Gmeiner P, Hübner H, Rougeot C. On the Terminal Homologation of Physiologically Active Peptides as a Means of Increasing Stability in Human Serum - Neurotensin, Opiorphin, B27-KK10 Epitope, NPY. Chem Biodivers 2011; 8:711-39. [DOI: 10.1002/cbdv.201100093] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Kao YJ, Ghosh M, Schonbrunn A. Ligand-dependent mechanisms of sst2A receptor trafficking: role of site-specific phosphorylation and receptor activation in the actions of biased somatostatin agonists. Mol Endocrinol 2011; 25:1040-54. [PMID: 21493671 DOI: 10.1210/me.2010-0398] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The somatostatin receptor subtype 2A (sst2A) mediates many of somatostatin's neuroendocrine actions and is the primary therapeutic target for the stable somatostatin analogs used to inhibit hormone secretion by pituitary and gastroenteropancreatic tumors. Two new multireceptor targeting somatostatin analogs currently under clinical investigation, the multisomatostatin receptor agonist cyclo-[diaminoethylcarbamoyl-HydroxyPro-Phenylglycine-D-Trp-Lys-(4-O-benzyl)Tyr-Phe] (SOM230) (Pasireotide) and pan-somatostatin receptor agonist Tyr-cyclo-[D-diaminobutyric acid-Arg-Phe-Phe-D-Trp-Lys-Thr-Phe] (KE108), behave as functionally selective ligands at the sst2A receptor, mimicking some of somatostatin's actions but antagonizing others. Further, SOM230 and KE108 are less able to induce receptor internalization than somatostatin, indicating that they exhibit functional selectivity for receptor regulation as well as signaling. Here, we identify agonist-specific differences in the molecular events regulating sst2A receptor endocytosis. SOM230 and KE108 were less potent and less effective than somatostatin at stimulating sst2A receptor phosphorylation at two pairs of residues, Ser341/343 and Thr353/354. Only the pattern of Thr353/354 phosphorylation correlated with receptor internalization, consistent with the known importance of Thr phosphorylation for sst2A receptor endocytosis. As expected, arrestin recruitment to membrane receptors was reduced with SOM230 and KE108. In addition, both receptor dephosphorylation and receptor recycling occurred more rapidly with SOM230 and KE108 than with somatostatin. Surprisingly, however, SOM230 and KE108 also altered sst2A internalization in a phosphorylation-independent manner, because these analogs were less effective than somatostatin at stimulating the endocytosis of a phosphorylation-negative receptor mutant. These results show that the decreased receptor internalization produced by SOM230 and KE108 compared with somatostatin result from phosphorylation-independent effects as well as reduced site-specific receptor phosphorylation and receptor-arrestin association.
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Affiliation(s)
- Yachu J Kao
- Department of Integrative Biology and Pharmacology, University of Texas, Health Science Center-Houston, Houston, Texas 77030, USA
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