title: Reassessment of sst2 somatostatin receptor expression in human normal and neoplastic tissues using the novel rabbit monoclonal antibody UMB-1.
abstract: OBJECTIVE
  The overexpression of somatostatin receptor 2 (sst2) in neuroendocrine tumors is the molecular basis for diagnostic and therapeutic application of the stable somatostatin analog octreotide. Recent evidence has shown that the immunocytochemical evaluation of sst2A status is of value for predicting response to octreotide therapy and disease prognosis. However, due to the lack of monoclonal and limited availability of specific polyclonal anti-sst2A antibodies, only very few patients can currently benefit from in vitro sst2 evaluation.
  
  
  METHODS
  In the present study, we extensively characterized the novel rabbit monoclonal anti-sst2A antibody (clone UMB-1) using tissues from sst2-deficient mice and their wild-type littermates. UMB-1 was then subjected to a comparative study of immunohistochemistry on a series of histological specimens from formalin-fixed, paraffin-embedded human tumors and adjacent normal tissues.
  
  
  RESULTS
  Immunoprecipitation experiments unequivocally demonstrated that UMB-1 selectively detected its cognate sst2A and did not cross-react with other proteins present in crude tissue homogenates. The UMB-1 monoclonal antibody, when compared with currently available polyclonal antisera, yielded several times more effective immunohistochemical staining of fixed-embedded tissues with a predominance of plasma membrane staining and very low cytoplasmic signal even without heat-based antigen retrieval. In addition, dual immunofluorescence revealed for the first time that the sst2A is present on not only gastrin-containing but also ghrelin-containing cells in human gastric mucosa.
  
  
  CONCLUSIONS
  Thus, the rabbit monoclonal antibody UMB-1 may prove of great value in the assessment of sst2A status in human neuroendocrine tumors during routine histopathological examination.
authors.affiliation: Department of Pharmacology and Toxicology, Friedrich-Schiller-University, Nonnenplan 4, 07743 Jena, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fischer
authors.forename: Christian
authors.initials: C
authors.lastname: Doll
authors.forename: Stefan
authors.initials: S
authors.lastname: Jacobs
authors.forename: Angela
authors.initials: A
authors.lastname: Kolodziej
authors.forename: Ralf
authors.initials: R
authors.lastname: Stumm
authors.forename: Stefan
authors.initials: S
authors.lastname: Schulz
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011817:Rabbits; D017481:Receptors, Somatostatin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D012016:Reference Values
chemical_list: D000911:Antibodies, Monoclonal; D017481:Receptors, Somatostatin; C106140:somatostatin receptor sst2A; C093733:somatostatin receptor 2