Reassessment of SST4 Somatostatin Receptor Expression Using SST4-eGFP Knockin Mice and the Novel Rabbit Monoclonal Anti-Human SST4 Antibody 7H49L61

GND
112354025
ORCID
0000-0003-0141-7310
Affiliation
Institute of Pharmacology and Toxicology, Jena University Hospital, D-07747 Jena, Germany;(B.E.);(R.S.);(J.G.);(S.S.)
Lupp, Amelie;
GND
1251345433
Affiliation
Institute of Pharmacology and Toxicology, Jena University Hospital, D-07747 Jena, Germany;(B.E.);(R.S.);(J.G.);(S.S.)
Ehms, Blanca;
GND
123252490
Affiliation
Institute of Pharmacology and Toxicology, Jena University Hospital, D-07747 Jena, Germany;(B.E.);(R.S.);(J.G.);(S.S.)
Stumm, Ralf;
GND
1251345778
Affiliation
Institute of Pharmacology and Toxicology, Jena University Hospital, D-07747 Jena, Germany;(B.E.);(R.S.);(J.G.);(S.S.)
Göckeritz, Johannes;
Affiliation
Institute of Neuropathology, University Hospital, Otto-von-Guericke-University, 39120 Magdeburg, Germany;
Mawrin, Christian;
GND
120334615
ORCID
0000-0002-5997-8885
Affiliation
Institute of Pharmacology and Toxicology, Jena University Hospital, D-07747 Jena, Germany;(B.E.);(R.S.);(J.G.);(S.S.)
Schulz, Stefan

Among the five somatostatin receptors (SST1–SST5), SST4 is the least characterized, which is in part due to the lack of specific monoclonal antibodies. We generated a knockin mouse model that expresses a carboxyl-terminal SST4-eGFP fusion protein. In addition, we extensively characterized the novel rabbit monoclonal anti-human SST4 antibody 7H49L61 using transfected cells and receptor-expressing tissues. 7H49L61 was then subjected to immunohistochemical staining of a series of formalin-fixed, paraffin-embedded normal and neoplastic human tissues. Characterization of SST4-eGFP mice revealed prominent SST4 expression in cortical pyramidal cells and trigeminal ganglion cells. In the human cortex, 7H49L61 disclosed a virtually identical staining pattern. Specificity of 7H49L61 was demonstrated by detection of a broad band migrating at 50–60 kDa in immunoblots. Tissue immunostaining was abolished by preadsorption of 7H49L61 with its immunizing peptide. In the subsequent immunohistochemical study, 7H49L61 yielded a predominant plasma membrane staining in adrenal cortex, exocrine pancreas, and placenta. SST4 was also found in glioblastomas, parathyroid adenomas, gastric and pancreatic adenocarcinomas, pheochromocytomas, and lymphomas. Altogether, we provide the first unequivocal localization of SST4 in normal and neoplastic human tissues. The monoclonal antibody 7H49L61 may also prove of great value for identifying SST4-expressing tumors during routine histopathological examinations.

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