Reevaluation of sst1 somatostatin receptor expression in human normal and neoplastic tissues using the novel rabbit monoclonal antibody UMB-7

Background: The somatostatin receptor 1 (sst(1)) is widely distributed throughout the body and is also present in neoplastic tissues. However, little is known about its precise tissue distribution, regulation and function, which may in part be due to the lack of specific monoclonal anti-sst(1) antibodies. Methods: We have characterized the novel rabbit monoclonal anti-human sst(1) antibody UMB-7 using sst(1)-expressing cells and human pituitary samples. The antibody was then used for immunohistochemical staining of a large panel of formalin-fixed, paraffin-embedded human tissues. Results: Western blot analyses of BON-1 cells and human pituitary revealed a broad band migrating at a molecular weight of 45,000-60,000. After enzymatic deglycosylation the size of this band decreased to a molecular weight of 45,000. UMB-7 yielded an efficient immunostaining of distinct cell populations in the human tissue samples with a predominance of plasma membrane staining, which was completely abolished by preadsorption of UMB-7 with its immunizing peptide. The sst(1) receptor was detected in anterior pituitary, pancreatic islets, distal tubules, enteric ganglion cells and nerve fibers, chief cells of the gastric mucosa, macrophages and mast cells. In addition, sst(1) was observed in pituitary adenomas, gastrointestinal neuroendocrine tumors and pheochromocytoma as well as in pancreatic adenocarcinomas, gastric carcinomas, urinary bladder carcinomas and sarcomas. Conclusions: UMB-7 may prove of great value in the identification of sst(1)-expressing tumors during routine histopathological examinations. This may open up new routes for diagnostic and therapeutic intervention. (C) 2013 Elsevier B.V. All rights reserved.