title: (89)Zr-labeled paramagnetic octreotide-liposomes for PET-MR imaging of cancer.
abstract: OBJECTIVE
  Dual-modality PET/MR platforms add a new dimension to patient diagnosis with high resolution, functional, and anatomical imaging. The full potential of this emerging hybrid modality could be realized by using a corresponding dual-modality probe. Here, we report pegylated liposome (LP) formulations, housing a MR T(1) contrast agent (Gd) and the positron-emitting (89)Zr (half-life: 3.27 days), for simultaneous PET and MR tumor imaging capabilities.
  
  
  METHODS
  (89)Zr oxophilicity was unexpectedly found advantageous for direct radiolabeling of preformed paramagnetic LPs. LPs were conjugated with octreotide to selectively target neuroendocrine tumors via human somatostatin receptor subtype 2 (SSTr2). (89)Zr-Gd-LPs and octreotide-conjugated homolog were physically, chemically and biologically characterized.
  
  
  RESULTS
  (89)Zr-LPs showed reasonable stability over serum proteins and chelator challenges for proof-of-concept in vitro and in vivo investigations. Nuclear and paramagnetic tracking quantified superior SSTr2-recognition of octreotide-LP compared to controls.
  
  
  CONCLUSIONS
  This study demonstrated SSTr2-targeting specificity along with direct chelator-free (89)Zr-labeling of LPs and dual PET/MR imaging properties.
authors.affiliation: Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 16, New York, New York, 10065, USA.
authors.forename: Diane S
authors.initials: DS
authors.lastname: Abou
authors.forename: Daniel L J
authors.initials: DL
authors.lastname: Thorek
authors.forename: Nicholas N
authors.initials: NN
authors.lastname: Ramos
authors.forename: Martijn W H
authors.initials: MW
authors.lastname: Pinkse
authors.forename: Hubert T
authors.initials: HT
authors.lastname: Wolterbeek
authors.forename: Sean D
authors.initials: SD
authors.lastname: Carlin
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Beattie
authors.forename: Jason S
authors.initials: JS
authors.lastname: Lewis
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000737:chemistry; D005682:Gadolinium / Q000737:chemistry; D006801:Humans; D007554:Isotopes / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008279:Magnetic Resonance Imaging / Q000379:methods; D051379:Mice; D018358:Neuroendocrine Tumors / Q000175:diagnosis*; D015282:Octreotide / Q000737:chemistry; D049268:Positron-Emission Tomography / Q000379:methods; D017481:Receptors, Somatostatin / Q000032:analysis; D015040:Zirconium / Q000737:chemistry
chemical_list: D003287:Contrast Media; D007554:Isotopes; D008081:Liposomes; D017481:Receptors, Somatostatin; C574734:SSTR2 protein, human; C492049:Sstr2 protein, mouse; D005682:Gadolinium; D015040:Zirconium; D015282:Octreotide