title: Positron-emission tomography (PET) imaging agents for diagnosis of human prostate cancer: agonist vs. antagonist ligands.
abstract: OBJECTIVE
  The present study adds scientific support to the growing debate regarding the superiority of radiolabeled bombesin-based antagonist peptides over agonists for molecular imaging and therapy of human tumors overexpressing the gastrin-releasing peptide receptor (GRPR) and describes a detailed in vitro and in vivo comparison of 64Cu-NODAGA-6-Ahx-BBN(7-14)NH2 agonist and 64Cu-NODAGA-6-Ahx-DPhe6-BBN(6-13)NHEt antagonist ligands.
  
  
  METHODS
  Conjugates were synthesized by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and characterized by electrospray ionization-mass spectroscopy. The conjugates were radiolabeled with 64Cu.
  
  
  RESULTS
  In vitro and in vivo data support the hypothesis for targeting of the GRPR by these tracer molecules. Maximum-intensity micro Positron Emission Tomography (microPET) imaging studies show the agonist ligand to provide high-quality, high-contrast images with very impressive tumor uptake and background clearance, with virtually no residual gastrointestinal or renal-urinary radioactivity.
  
  
  CONCLUSIONS
  Based on microPET imaging experiments, we conclude the agonist peptide ligand to be a superior molecular imaging agent for targeting GRPR.
authors: Department of Radiology, University of Missouri School of Medicine, and Harry S. Truman Memorial Veterans' Hospital, One Hospital Drive, Columbia, MO 65211, USA.
authors: Prasant K
authors: PK
authors: Nanda
authors: Brieanne E
authors: BE
authors: Wienhoff
authors: Tammy L
authors: TL
authors: Rold
authors: Gary L
authors: GL
authors: Sieckman
authors: Ashley F
authors: AF
authors: Szczodroski
authors: Timothy J
authors: TJ
authors: Hoffman
authors: Buck E
authors: BE
authors: Rogers
authors: Charles J
authors: CJ
authors: Smith
mesh_terms: D003287:Contrast Media; D006801:Humans; D008024:Ligands; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000175:diagnosis*
chemical_list: D003287:Contrast Media; D008024:Ligands