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Companion Animals Models of Human Disease
Published in Rebecca A. Krimins, Learning from Disease in Pets, 2020
The prevalence of GH (growth hormone)-secreting pituitary tumors in domestic cats (Felis catus) is ten-fold greater than in humans. The predominant inhibitory receptors of GH-secreting pituitary tumors are somatostatin receptors (SSTRs) and D2 dopamine receptors (DRD2). The expression of these receptors is associated with the response to somatostatin analog and dopamine agonist treatment in human patients with acromegaly. A study in cats evaluated pathological features of pituitaries from domestic cats with acromegaly, pituitary receptor expression, and investigated correlates with clinical data, including pituitary volume, time since diagnosis of diabetes, insulin requirement, and serum IGF1 concentration. Loss of reticulin structure was identified in 15 of 21 pituitaries, of which 10 of 15 exhibited acinar hyperplasia. SSTR1, SSTR2, SSTR5, and DRD2 mRNA were identified in the feline pituitary, whereas SSTR3 and SSTR4 were not. Expression of SSTR1, SSTR2, and SSTR5 was greater in acromegalic cats compared with controls. A negative correlation was identified between DRD2 mRNA expression and pituitary volume(24,25).
Neuroendocrine tumours
Published in Anju Sahdev, Sarah J. Vinnicombe, Husband & Reznek's Imaging in Oncology, 2020
Sairah R Khan, Kathryn L Wallitt, Adil Al-Nahhas, Tara D Barwick
Functional receptor imaging of NETs relies on the fact that many tumours express high levels of somatostatin receptors on their cell membranes, which can then be targeted with radiolabelled receptor ligands, both for diagnosis as well as for peptide receptor radionuclide therapy (PRRT). Of the five human somatostatin receptors (SSTR1–5), SSTR2 is the most commonly expressed on NET cell membranes (24).
Radiolabeled Agents for Molecular Imaging and/or Therapy
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Dimitrios Psimadas, Eirini A. Fragogeorgi
Somatostatin (SST) is a cyclic peptide hormone that is expressed in the central and peripheral nervous systems and is present in two forms: SST-14 consisting of 14 amino acids and SST-28 consisting of 28 amino acids. SST inhibits the release of hormones such as growth hormone, glucagon, and insulin by binding to five different G-coupled SST cell membrane receptors (sstr1–5), which recognize the ligand and generate a transmembrane signal. The resulting hormone–receptor complexes have the ability to be internalized. Neuroendocrine tumors frequently express a high density of sstr, with the sstr2 subtype generally showing the highest density (Weckbecker et al. 2003).
Drug treatment strategies for secondary diabetes in patients with acromegaly
Published in Expert Opinion on Pharmacotherapy, 2020
Sylvère Störmann, Jochen Schopohl
As surgical removal of the pituitary adenoma in acromegaly is not always successful or a surgical approach is not practicable (either from a technical standpoint or due to patient preference), pharmacological treatment options play an important role in the therapeutic landscape of acromegaly [74]. Somatostatin analogues (SSA) are synthetic somatostatin receptor ligands (SRL) that are structurally similar to somatostatin [86]. Somatostatin is a naturally occurring peptide that binds to several types of receptors (SSTR1 through SSTR5) that are widely distributed to varying extent on cells throughout the body [87]. Neuroendocrine pancreatic cells in particular express different subtypes of SSTR. SSA on the other hand have varying binding affinity to the SSTR subtypes. This explains why the effects of somatostatin and its analogues on glucose homeostasis differ one from another. Since their commercialization in the 1980s, SSA have become the cornerstone of medical acromegaly treatment as reflected by guidelines and consensus statements [74,88,89].
New insights into targeting hepatic cystogenesis in autosomal dominant polycystic liver and kidney disease
Published in Expert Opinion on Therapeutic Targets, 2020
Thijs R. M. Barten, Lucas H. P. Bernts, Joost P. H. Drenth, Tom J. G. Gevers
One of these alternatives, the more recently developed SA pasireotide (high affinity for SSTR1, SSTR2, SSTR 3, and SSTR5), was found to be more effective in reducing hepato-renal cystogenesis than octreotide in rodent models. In this study, polycystic kidney (PCK) rats (a rodent model used for PLD) and polycystic kidney disease (Pkd2) mice (rodent models for ADPKD) were sacrificed 6 weeks after treatment with octreotide or pasireotide. Several indices for both hepatic and renal cystogenesis showed a statistically significant decrease in rodents treated with pasireotide compared to octreotide and controls, indicating that pasireotide was more potent than octreotide in reducing cyst burden [32].
Identification and imaging of miR-155 in the early screening of lung cancer by targeted delivery of octreotide-conjugated chitosan-molecular beacon nanoparticles
Published in Drug Delivery, 2018
Hai-Zhen Zhu, Jing Hou, Yi Guo, Xin Liu, Fei-Long Jiang, Guang-Peng Chen, Xiu-Feng Pang, Jian-Guo Sun, Zheng-Tang Chen
At present, the main challenge for cancer diagnosis and treatment is to enable anticancer drugs or imaging agents that specifically target tumor cells. The somatostatin receptors (SSTRs) are expressed in many tumor tissues and metastatic lesions, such as lung cancer, breast cancer, pancreatic cancer. Five subtypes of somatostatin receptors SSTRs, namely SSTR1-5, and SSTR2 expression are seen in most of these tumors (Shahbaz et al., 2015; Kharmate et al., 2013). Artificially synthesized somatostatin analog (SSTA) such as octreotide (OCT) could specifically bind to SSTR2 to achieve the purpose of targeting tumor cells with SSTR2 expression (Ju et al., 2018; Shen et al., 2017).