title: Monoclonal antibodies against the human somatostatin receptor subtypes 1-5: development and immunohistochemical application in neuroendocrine tumors.
abstract: BACKGROUND
  Activation of somatostatin receptors (sstr1-5) by somatostatin and its analogues exerts an inhibitory effect on hormone secretion and provides the basis for the treatment of a range of endocrine diseases such as acromegaly, Cushing's disease and neuroendocrine tumors (NET). The lack of well-characterized commercially available sstr subtype-specific antibodies prevents routine identification of the sstr expression profile in patients.
  
  
  METHODS
  We generated and characterized new mouse monoclonal antibodies (mAbs) targeting the five human sstr subtypes using ELISA and immunohistochemistry, and tested their suitability in formalin-fixed and paraffin-embedded (FFPE) human tissues and archival samples of normal pancreatic tissue and NET.
  
  
  RESULTS
  All mAbs were highly specific with no cross-reactivity. The sstr1-5 immunoreactivity in gastrointestinal NET (n=67) was correlated with clinicopathologic data. With the exception of sstr3, NET were highly positive for all receptor subtypes (42, 63, 6, 32 and 65% of tumors were positive for sstr1, sstr2a, sstr3, sstr4 and sstr5, respectively). sstr1, sstr2a and sstr5 were present at the plasma membrane and in the cytoplasm of tumor cells, whereas sstr3 and sstr4 were almost exclusively cytoplasmic. Immunoreactivity of sstr1, sstr2a and sstr4 tended to decrease as tumor aggressiveness increased. sstr5 showed an opposite pattern, with higher staining in well-differentiated carcinomas compared with well-differentiated tumors. sstr5 immunoreactivity was correlated with the presence of metastases and angioinvasion, suggesting a possible association with more aggressive behavior.
  
  
  CONCLUSIONS
  Determination of the sstr1-5 by immunohistochemistry using subtype-specific mAbs is feasible in FFPE tissue and may provide a tool for routine clinical practice.
authors.affiliation: Novartis Institutes for BioMedical Research, Basel, Switzerland. herbert.schmid@novartis.com
authors.forename: Herbert A
authors.initials: HA
authors.lastname: Schmid
authors.forename: Chiara
authors.initials: C
authors.lastname: Lambertini
authors.forename: Harmke H
authors.initials: HH
authors.lastname: van Vugt
authors.forename: Patrizia
authors.initials: P
authors.lastname: Barzaghi-Rinaudo
authors.forename: Judith
authors.initials: J
authors.lastname: Schäfer
authors.forename: Rainer
authors.initials: R
authors.lastname: Hillenbrand
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Sailer
authors.forename: Martina
authors.initials: M
authors.lastname: Kaufmann
authors.forename: Paolo
authors.initials: P
authors.lastname: Nuciforo
mesh_terms: D000328:Adult; D000818:Animals; D000911:Antibodies, Monoclonal; D029681:Arabidopsis Proteins / Q000378:metabolism; D002461:Cell Line, Transformed; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D019751:Intramolecular Transferases / Q000378:metabolism; D008297:Male; D051379:Mice; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis / Q000378:metabolism*; D011485:Protein Binding; D017481:Receptors, Somatostatin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D029681:Arabidopsis Proteins; D017481:Receptors, Somatostatin; C103631:somatostatin receptor 3; C098681:somatostatin receptor subtype-4; C101130:somatostatin receptor type 1; C094573:somatostatin receptor 5; C093733:somatostatin receptor 2; D019751:Intramolecular Transferases; C568454:marneral synthase, Arabidopsis