title: GLP-1 receptor expression in human tumors and human normal tissues: potential for in vivo targeting.
abstract: Peptide hormone receptors overexpressed in human tumors, such as somatostatin receptors, can be used for in vivo targeting for diagnostic and therapeutic purposes. A novel promising candidate in this field is the GLP-1 receptor, which was recently shown to be massively overexpressed in gut and lung neuroendocrine tumors--in particular, in insulinomas. Anticipating a major development of GLP-1 receptor targeting in nuclear medicine, our aim was to evaluate in vitro the GLP-1 receptor expression in a large variety of other tumors and to compare it with that in nonneoplastic tissues.
  
  
  METHODS
  The GLP-1 receptor protein expression was qualitatively and quantitatively investigated in a broad spectrum of human tumors (n=419) and nonneoplastic human tissues (n=209) with receptor autoradiography using (125)I-GLP-1(7-36)amide. Pharmacologic competition experiments were performed to provide proof of specificity of the procedure.
  
  
  RESULTS
  GLP-1 receptors were expressed in various endocrine tumors, with particularly high amounts in pheochromocytomas, as well as in brain tumors and embryonic tumors but not in carcinomas or lymphomas. In nonneoplastic tissues, GLP-1 receptors were present in generally low amounts in specific tissue compartments of several organs--namely, pancreas, intestine, lung, kidney, breast, and brain; no receptors were identified in lymph nodes, spleen, liver, or the adrenal gland. The rank order of potencies for receptor binding--namely, GLP-1(7-36)amide = exendin-4 >> GLP-2 = glucagon(1-29)--provided proof of specific GLP-1 receptor identification.
  
  
  CONCLUSIONS
  The GLP-1 receptors may represent a novel molecular target for in vivo scintigraphy and targeted radiotherapy for a variety of GLP-1 receptor-expressing tumors. For GLP-1 receptor scintigraphy, a low-background signal can be expected, on the basis of the low receptor expression in the normal tissues surrounding tumors.
authors.affiliation: Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Bern, Bern, Switzerland.
authors.forename: Meike
authors.initials: M
authors.lastname: Körner
authors.forename: Martin
authors.initials: M
authors.lastname: Stöckli
authors.forename: Beatrice
authors.initials: B
authors.lastname: Waser
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Reubi
mesh_terms: D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D016503:Drug Delivery Systems / Q000379:methods*; D005240:Feasibility Studies; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D051379:Mice; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D018027:Receptors, Glucagon / Q000378:metabolism*; D012016:Reference Values
chemical_list: C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D019275:Radiopharmaceuticals; D018027:Receptors, Glucagon