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JCI Insight Feb 2021Somatostatin (SS) inhibits glucagon-like peptide-1 (GLP-1) secretion in a paracrine manner. We hypothesized that blocking somatostatin subtype receptor 2 (SSTR2) and 5...
Somatostatin (SS) inhibits glucagon-like peptide-1 (GLP-1) secretion in a paracrine manner. We hypothesized that blocking somatostatin subtype receptor 2 (SSTR2) and 5 (SSTR5) would improve glycemia by enhancing GLP-1 secretion. In the perfused mouse small intestine, the selective SSTR5 antagonist (SSTR5a) stimulated glucose-induced GLP-1 secretion to a larger degree than the SSTR2 antagonist (SSTR2a). In parallel, mice lacking the SSTR5R showed increased glucose-induced GLP-1 secretion. Both antagonists improved glycemia in vivo in a GLP-1 receptor-dependent (GLP-1R-dependent) manner, as the glycemic improvements were absent in mice with impaired GLP-1R signaling and in mice treated with a GLP-1R-specific antagonist. SSTR5a had no direct effect on insulin secretion in the perfused pancreas, whereas SSTR2a increased insulin secretion in a GLP-1R-independent manner. Adding a dipeptidyl peptidase 4 inhibitor (DPP-4i) in vivo resulted in additive effects on glycemia. However, when glucose was administered intraperitoneally, the antagonist was incapable of lowering blood glucose. Oral administration of SSTR5a, but not SSTR2a, lowered blood glucose in diet-induced obese mice. In summary, we demonstrate that selective SSTR antagonists can improve glucose control primarily through the intestinal GLP-1 system in mice.
Topics: Animals; Blood Glucose; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Female; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Hypoglycemic Agents; Insulin; Insulin Secretion; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Obese; Receptors, Somatostatin
PubMed: 33434183
DOI: 10.1172/jci.insight.143228 -
Nuclear Medicine Review. Central &... 2016Detection of neuroendocrine neoplasms (NENs) and monitoring of their response to therapy is still challenging due to huge heterogeneity of that group of tumors.... (Review)
Review
Detection of neuroendocrine neoplasms (NENs) and monitoring of their response to therapy is still challenging due to huge heterogeneity of that group of tumors. Actually, NENs visualization is mainly based on molecular imaging while in the past it was relied on less effective structural imaging including CT and MRI. Molecular imaging techniques in combination with structural imaging (hybrid imaging), especially in patients with well-differentiated NENs, in addition to morphological provide the functional information about tumor which benefits in a more accurate patient management, including more sensitive visualization of primary tumors, more precise staging and better therapy follow-up. Overexpression of somatostatin receptors (SSTR) on NENs' cell membrane was a basis for development of somatostatin receptor scintigraphy (SRS) using single photon emission tomography SPECT, which is today a well-established standard in molecular imaging of NENs, and further imaging improvement in the field of positron emission tomography (PET). Use of hybrid imaging (SPECT/CT, PET/CT) increased sensitivity of examination, mainly resulting in better detection of small lesions. Generally, somatostatin receptor imaging with PET/CT is an emerging technique, although still with limited access, but due to several advantages over SSTR SPECT/CT, should be used if available. It is worth mentioning, that both SSTR PET/CT and SSTR SPECT/CT have some limitations, such as relatively low detection rate of benign insulinomas, poorly differentiated GEP-NETs and liver metastases. For that reason further improvement of NETs imaging is necessary. The most promising new tracers' families are based on SSTR antagonists, 64Cu-radiolabeled ligands and glucagon-like peptide-1 receptor (GLP-1R) imaging. Finally, in case of poor-differentiated neuroendocrine cancers 18F-FDG PET/CT may be beneficial in comparison with molecular imaging based on somatostatin receptor modalities.
Topics: Humans; Molecular Imaging; Neuroendocrine Tumors; Radionuclide Imaging; Receptors, Somatostatin
PubMed: 27479789
DOI: 10.5603/NMR.2016.0023 -
Frontiers in Endocrinology 2021Medical treatment for acromegaly commonly involves receiving intramuscular or deep subcutaneous injections of somatostatin receptor ligands (SRLs) in most patients. In... (Randomized Controlled Trial)
Randomized Controlled Trial
Medical treatment for acromegaly commonly involves receiving intramuscular or deep subcutaneous injections of somatostatin receptor ligands (SRLs) in most patients. In addition to side effects of treatment, acromegaly patients often still experience disease symptoms even when therapy is successful in controlling GH and IGF-1 levels. Symptoms and side effects can negatively impact patients' health-related quality of life. In this study, we examine the disease- and treatment-related burden associated with SRL injections as reported through the use of the Acromegaly Treatment Satisfaction Questionnaire (Acro-TSQ ) and clinician-reported symptom severity through the Acromegaly Index of Severity (AIS). Patients included in this analysis were enrolled in a randomized phase 3 study, were biochemically-controlled (an IGF-1 < 1.3 × the upper limit of normal [ULN] and average GH < 2.5 ng/ml) and receiving SRL injections for ≥6 months with a stable dose of either long-acting octreotide or lanreotide monotherapy for ≥4 months. The sample (N = 91) was 65% female, 91% Caucasian, with a mean [standard deviation (SD)] age of 53 (1) years. Two-thirds of patients reported that they still experience acromegaly symptoms; 82% of these said they experience symptoms all of the time. Three-fourths experienced gastrointestinal (GI) side effects after injections, and 77% experienced treatment-related injection site reactions (ISRs). Patients commonly reported that these interfered with their daily life, leisure, and work activities. Those with higher symptom severity, as measured by the AIS, scored significantly worse on several Acro-TSQ domains: Symptom Interference, GI Interference, Treatment Satisfaction, and Emotional Reaction. Despite being biochemically controlled with injectable SRLs, most patients reported experiencing acromegaly symptoms that interfere with daily life, leisure, and work. GI side effects and ISRs were also common. This study highlights the significant disease burden that still persists for patients with acromegaly that have achieved biochemical control with the use of injectable SRLs.
Topics: Acromegaly; Cost of Illness; Female; Gastrointestinal Diseases; Humans; Injections; Ligands; Male; Middle Aged; Receptors, Somatostatin
PubMed: 33790860
DOI: 10.3389/fendo.2021.627711 -
European Journal of Endocrinology Sep 2022The aim of this study was to develop an open-source and reproducible digital quantitative analysis (DIA) of somatostatin receptor subtype 2a (SST2) staining in...
OBJECTIVE
The aim of this study was to develop an open-source and reproducible digital quantitative analysis (DIA) of somatostatin receptor subtype 2a (SST2) staining in formalin-fixed paraffin-embedded tissues of pancreatic neuroendocrine tumors (panNETs) and growth hormone (GH)-secreting pituitary adenomas (GHomas).
DESIGN
SST2 immunostaining of 18 panNETs and 39 GHomas was assessed using a novel DIA protocol and compared with a widely used semi-quantitative immunoreactivity score (IRS).
METHODS
The DIA software calculates the staining intensity/area and the percentage of positive cells (%PC). Four representative images were selected for each sample by two independent selectors (S1 and S2), with the analysis performed by two independent analyzers (A1 and A2). Agreement between observers was calculated using the concordance correlation coefficient (CCC).
RESULTS
In panNETs, the CCC ranged 0.935-0.977 for intensity/area and 0.942-0.983 for %PC. In GHomas, the CCC ranged 0.963-0.997 for intensity/area and 0.979-0.990 for %PC. In both panNETs and GHomas, the DIA staining intensity was strongly correlated with the IRS (Spearman rho: 0.916-0.969, P < 0.001), as well as the DIA %PC with the IRS %PC (Spearman rh: 0.826-0.881, P < 0.001). In GHomas, the biochemical response to somatostatin receptor ligands correlated with SST2 expression, evaluated both as DIA intensity/area (Spearman rho: -0.448 to -0.527, P = 0.007-0.004) and DIA %PC (Spearman rho: -0.558 to -0.644, P ≤ 0.001).
CONCLUSIONS
The DIA has an excellent inter-observer agreement and showed a strong correlation with the widely used semi-quantitative IRS. The DIA protocol is an open-source, highly reproducible tool and provides a reliable quantitative evaluation of SST2 immunohistochemistry.
Topics: Adenoma; Growth Hormone-Secreting Pituitary Adenoma; Humans; Immunohistochemistry; Receptors, Somatostatin
PubMed: 35895707
DOI: 10.1530/EJE-22-0339 -
Theranostics 2018More than 25 years after the first peptide receptor radionuclide therapy (PRRT), the concept of somatostatin receptor (SSTR)-directed imaging and therapy for... (Review)
Review
More than 25 years after the first peptide receptor radionuclide therapy (PRRT), the concept of somatostatin receptor (SSTR)-directed imaging and therapy for neuroendocrine tumors (NET) is seeing rapidly increasing use. To maximize the full potential of its theranostic promise, efforts in recent years have expanded recommendations in current guidelines and included the evaluation of novel theranostic radiotracers for imaging and treatment of NET. Moreover, the introduction of standardized reporting framework systems may harmonize PET reading, address pitfalls in interpreting SSTR-PET/CT scans and guide the treating physician in selecting PRRT candidates. Notably, the concept of PRRT has also been applied beyond oncology, for treatment of inflammatory conditions like sarcoidosis. Future perspectives may include the efficacy evaluation of PRRT compared to other common treatment options for NET, novel strategies for closer monitoring of potential side effects, the introduction of novel radiotracers with beneficial pharmacodynamic and kinetic properties or the use of supervised machine learning approaches for outcome prediction. This article reviews how the SSTR-directed theranostic concept is currently applied and also reflects on recent developments that hold promise for the future of theranostics in this context.
Topics: Animals; Humans; Neuroendocrine Tumors; Radiopharmaceuticals; Receptors, Somatostatin; Theranostic Nanomedicine
PubMed: 30613284
DOI: 10.7150/thno.30357 -
The Journal of Histochemistry and... Aug 2008Somatostatin mediates inhibitory functions through five G protein-coupled somatostatin receptors (sst1-5). We used immunohistochemistry, immunofluorescence, and RT-PCR...
Somatostatin mediates inhibitory functions through five G protein-coupled somatostatin receptors (sst1-5). We used immunohistochemistry, immunofluorescence, and RT-PCR to determine the presence of somatostatin receptors sst1, sst2A, sst2B, sst3, sst4, and sst5 in normal and IgA nephropathy human kidney. All somatostatin receptors were detected in the thin tubules (distal convoluted tubules and loops of Henle) and thick tubules (proximal convoluted tubules) in the tissue sections from nephrectomy and biopsy samples. Immunopositive sst1 and sst4 staining was more condensed in the cytoplasm of tubular epithelial cells. In normal kidney tissue sections, podocytes and mesangial cells in the glomeruli stained for sst1, sst2B, sst4 and sst5, and stained weakly for sst3. In IgA kidney tissue, the expression of somatostatin receptors was significantly increased with particular immmunopositive staining for sst1, sst2B, sst4, and sst5 within glomeruli. In the epithelial cells, the staining for sst2B and sst4 in proximal tubules and sst1, sst2B, and sst5 in distal tubules was increased. The mRNA expression of sst1-5 was also detected by RT-PCR. Somatostatin and all five receptor subtypes were ubiquitously distributed in normal kidney and IgA nephropathy. The increased expression of somatostatin receptors in IgA nephropathy kidney might be the potential pathogenesis of inflammatory renal disease.
Topics: Glomerulonephritis, IGA; Humans; Immunohistochemistry; Kidney; RNA, Messenger; Receptors, Somatostatin; Reverse Transcriptase Polymerase Chain Reaction; Somatostatin
PubMed: 18443363
DOI: 10.1369/jhc.2008.950998 -
Journal of Nuclear Medicine : Official... Jul 2011Somatostatin-based radiolabeled peptides have been successfully introduced into the clinic for targeted imaging and radionuclide therapy of somatostatin receptor...
UNLABELLED
Somatostatin-based radiolabeled peptides have been successfully introduced into the clinic for targeted imaging and radionuclide therapy of somatostatin receptor (sst)-positive tumors, especially of subtype 2 (sst2). The clinically used peptides are exclusively agonists. Recently, we showed that radiolabeled antagonists may be preferable to agonists because they showed better pharmacokinetics, including higher tumor uptake. Factors determining the performance of radioantagonists have only scarcely been studied. Here, we report on the development and evaluation of four (64)Cu or (68)Ga radioantagonists for PET of sst2-positive tumors.
METHODS
The novel antagonist p-Cl-Phe-cyclo(D-Cys-Tyr-D-4-amino-Phe(carbamoyl)-Lys-Thr-Cys)D-Tyr-NH(2) (LM3) was coupled to 3 macrocyclic chelators, namely 4,11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (CB-TE2A), 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), and DOTA. (64/nat)Cu- and (68/nat)Ga-NODAGA-LM3 were prepared at room temperature, and (64/nat)Cu-CB-TE2A-LM3 and (68/nat)Ga-DOTA-LM3 were prepared at 95°C. Binding affinity and antagonistic properties were determined with receptor autoradiography and immunofluorescence microscopy using human embryonic kidney (HEK)-sst2 cells. In vitro internalization and dissociation was evaluated using the same cell line. Biodistribution and small-animal PET studies were performed with HEK-sst2 xenografts.
RESULTS
All metallopeptides demonstrated antagonistic properties. The affinities depend on chelator and radiometal and vary about 10-fold; (68/nat)Ga-NODAGA-LM3 has the lowest half maximal inhibitory concentration (1.3 ± 0.3 nmol/L). The biodistribution studies show impressive tumor uptake at 1 h after injection, particularly of (64)Cu- and (68)Ga-NODAGA-LM3 (∼40 percentage injected dose per gram of tissue [%ID/g]), which were proven to be specific. Background clearance was fast and the tumor washout relatively slow for (64)Cu-NODAGA-LM3 (∼15 %ID/g, 24 h after injection) and almost negligible for (64)Cu-CB-TE2A-LM3 (26.9 ± 3.3 %ID/g and 21.6 ± 2.1 %ID/g, 4 and 24 h after injection, respectively). Tumor-to-normal-tissue ratios were significantly higher for (64)Cu-NODAGA-LM3 than for (64)Cu-CB-TE2A-LM3 (tumor-to-kidney, 12.8 ± 3.6 and 1.7 ± 0.3, respectively; tumor-to-muscle, 1,342 ± 115 and 75.2 ± 8.5, respectively, at 24 h, P < 0.001). Small-animal PET shows clear tumor localization and high image contrast, especially for (64)Cu- and (68)Ga-NODAGA-LM3.
CONCLUSION
This article demonstrates the strong dependence of the affinity and pharmacokinetics of the somatostatin-based radioantagonists on the chelator and radiometal. (64)Cu- and (68)Ga-NODAGA-LM3 and (64)Cu-CB-TE2A-LM3 are promising candidates for clinical translation because of their favorable pharmacokinetics and the high image contrast on PET scans.
Topics: Amino Acid Sequence; Animals; Chelating Agents; Copper Radioisotopes; Female; Gallium Radioisotopes; HEK293 Cells; Humans; Hydrophobic and Hydrophilic Interactions; Mice; Neoplasms; Positron-Emission Tomography; Protein Transport; Radiochemistry; Receptors, Somatostatin; Somatostatin
PubMed: 21680701
DOI: 10.2967/jnumed.111.087999 -
Oncotarget Sep 2016The truncated somatostatin receptor sst5TMD4 is associated with poor prognosis in breast cancer and increases breast cancer cell malignancy. Here, we examined the...
The truncated somatostatin receptor sst5TMD4 stimulates the angiogenic process and is associated to lymphatic metastasis and disease-free survival in breast cancer patients.
The truncated somatostatin receptor sst5TMD4 is associated with poor prognosis in breast cancer and increases breast cancer cell malignancy. Here, we examined the cellular/molecular mechanisms underlying this association, aiming to identify new molecular tools to improve diagnosis, prognosis or therapy. A gene expression array comparing sst5TMD4 stably-transfected MCF-7 cells and their controls (empty-plasmid) revealed the existence of profound alterations in the expression of genes involved in key tumoral processes, such as cell survival or angiogenesis. Moreover, sst5TMD4-overexpressing MCF-7 and MDA-MB-231 cells demonstrated increased expression/production of pro-angiogenic factors and enhanced capacity to form mammospheres. Consistently, sst5TMD4-expressing MCF-7 cells induced xenografted tumors with higher VEGF levels and elevated number of blood vessels. Importantly, sst5TMD4 was expressed in a subset of breast cancers, where it correlated with angiogenic markers, lymphatic metastasis, and reduced disease-free survival. These results, coupled to our previous data, support a relevant role of sst5TMD4 in the angiogenic process and reinforce the role of sst5TMD4 in breast cancer malignancy and metastatic potential, supporting its possible utility to develop new molecular biomarkers and drug therapies for these tumors.
Topics: Adult; Aged; Animals; Biomarkers, Tumor; Breast Neoplasms; Cell Line, Tumor; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Humans; Kaplan-Meier Estimate; Lymphatic Metastasis; MCF-7 Cells; Mice, Nude; Middle Aged; Mutation; Neovascularization, Pathologic; Receptors, Somatostatin; Transplantation, Heterologous
PubMed: 27507050
DOI: 10.18632/oncotarget.11076 -
Journal of Nuclear Medicine : Official... Dec 2020
Topics: Gallium Radioisotopes; Humans; Indium Radioisotopes; Neuroendocrine Tumors; Radionuclide Imaging; Receptors, Somatostatin
PubMed: 33293432
DOI: 10.2967/jnumed.120.251934 -
Neuroendocrinology 2015The expression of somatostatin receptors (SSTRs) and dopamine receptor 2 (DR2) in neuroendocrine tumors is of clinical importance as somatostatin analogues and dopamine...
OBJECTIVE
The expression of somatostatin receptors (SSTRs) and dopamine receptor 2 (DR2) in neuroendocrine tumors is of clinical importance as somatostatin analogues and dopamine agonists can be used for their localization and/or treatment. The objective of this study is to examine the expression of the five SSTR subtypes and DR2 in lung carcinoids (LCs).
METHODS
We conducted a retrospective study of 119 LCs from 106 patients [typical carcinoids (TCs): n = 100, and atypical carcinoids (ACs): n = 19]. The expression of all five SSTR subtypes and DR2 was evaluated immunohistochemically and correlated to clinicopathological data. In a subgroup of cases, receptor expression was further analyzed using semiquantitative RT-PCR.
RESULTS
SSTR2A was the SSTR subtype most frequently expressed immunohistochemically (72%), followed by SSTR1 (63%), SSTR5 (40%), and SSTR3 (20%), whereas SSTR4 was negative. DR2 was expressed in 74% and co-expressed with SSTR1 in 56%, with SSTR2A in 59%, with SSTR3 in 19%, and with SSTR5 in 37% of the tumors. Receptor expression was not related to the histological subtype, tumor aggressiveness (disease extent/grading) or functionality; however, DR2 was expressed more frequently in ACs than TCs (95 vs. 70%, p = 0.017). In a subset of patients, RT-PCR findings highly suggested that the expression of SSTR2A, SSTR3, DR2, and to a lesser extent that of SSTR1 and SSTR5 is the outcome of increased gene transcription.
CONCLUSIONS
The high and variable immunohistochemical expression of the majority of SSTRs along with their co-expression with DR2 in LCs provides a rationale for their possible treatment with agents that target these receptors.
Topics: Carcinoid Tumor; Female; Humans; Lung Neoplasms; Male; Middle Aged; Neoplasm Proteins; Receptors, Dopamine D2; Receptors, Somatostatin; Retrospective Studies
PubMed: 25765100
DOI: 10.1159/000381061