title: Targeting dopamine receptors subtype 2 (D2DR) in pheochromocytomas: head-to-head comparison between in vitro and in vivo findings.
abstract: BACKGROUND
  Dopamine subtype 2 receptors (D2DRs) are overexpressed in pheochromocytomas (PHEOs). D2DR-expressing tumors can be visualized by iodine-123 labeled iodobenzamide (¹²³I-IBZM) single-photon emission computed tomography (SPECT).
  
  
  OBJECTIVE
  The hypothesis of this study was that D2DR high expression in PHEOs would allow in vivo visualization through ¹²³I-IBZM SPECT. The present prospective pilot study aims to evaluate the performance of ¹²³I-IBZM SPECT in PHEOs and to correlate the tumor uptake with D2DR expression in tumor samples after surgery. SETTING, MATERIALS, AND METHODS: Ten unrelated patients with PHEOs were evaluated, prior to adrenalectomy, with ¹²³I-IBZM SPECT (whole body scan at 4 and 24 h after the injection; and SPECT centered on the abdomen at 24 h). D2DR mRNA and protein expressions were evaluated in all tumors by quantitative real-time RT-PCR and immunohistochemistry, respectively.
  
  
  METHODS
  Intensity of tumoral uptake of ¹²³I-IBZM was measured.
  
  
  RESULTS
  All PHEOs express D2DR mRNA (ranging from 2.1 to 14.7 copy/copy β-glucuronidase) and protein (immunostaining score: moderate or strong in 9 of 10 cases). However, none of the patients (0%) showed an increased tumor uptake of ¹²³I-IBZM.
  
  
  CONCLUSIONS
  These results suggest that ¹²³I-IBZM is not a useful radiopharmaceutical in the detection and characterization of PHEOs despite D2DR expression. Our findings and data from the related literature may support different hypotheses to explain the failure of D2DR targeting by ¹²³I-IBZM.
authors.affiliation: Unité Mixte de Recherche 7286, CRN2M, Centre National de la Recherche Scientifique, Aix-Marseille Université, Faculté de Médecine, Secteur Nord, CS80011, 51 Boulevard Pierre Dramard, 13344 Marseille, Cedex 15, France. alexandru.saveanu@univ-amu.fr.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Saveanu
authors.forename: Frederic
authors.initials: F
authors.lastname: Sebag
authors.forename: Benjamin
authors.initials: B
authors.lastname: Guillet
authors.forename: Cendrine
authors.initials: C
authors.lastname: Archange
authors.forename: Wassim
authors.initials: W
authors.lastname: Essamet
authors.forename: Anne
authors.initials: A
authors.lastname: Barlier
authors.forename: Fausto F
authors.initials: FF
authors.lastname: Palazzo
authors.forename: David
authors.initials: D
authors.lastname: Taïeb
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D000311:Adrenal Glands / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D000328:Adult; D002462:Cell Membrane / Q000378:metabolism / Q000473:pathology; D003593:Cytoplasm / Q000378:metabolism / Q000473:pathology; D018492:Dopamine Antagonists / Q000493:pharmacokinetics; D065127:Dopamine D2 Receptor Antagonists; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007462:Iodobenzenes / Q000493:pharmacokinetics; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010673:Pheochromocytoma / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D010865:Pilot Projects; D012333:RNA, Messenger / Q000378:metabolism; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution; D051598:Whole Body Imaging
chemical_list: C581293:DRD2 protein, human; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007462:Iodobenzenes; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; D017448:Receptors, Dopamine D2; C426805:idobenzamide