title: Gallium-68-labeled anti-HER2 single-chain Fv fragment: development and in vivo monitoring of HER2 expression.
abstract: OBJECTIVE
  We aimed to develop a gallium-68 (Ga-68)-labeled single-chain variable fragment (scFv) targeting the human epidermal growth factor receptor 2 (HER2) to rapidly and noninvasively evaluate the status of HER2 expression.
  
  
  METHODS
  Anti-HER2 scFv was labeled with Ga-68 by using deferoxamine (Df) as a bifunctional chelate. Biodistribution of [(68)Ga]Df-anti-HER2 scFv was examined with tumor-bearing mice and positron emission tomography (PET) imaging was performed. The changes in HER2 expression after anti-HER2 therapy were monitored by PET imaging.
  
  
  RESULTS
  [(68)Ga]Df-anti-HER2 scFv was obtained with high radiochemical yield after only a 5-min reaction at room temperature. The probe showed high accumulation in HER2-positive xenografts and the intratumoral distribution of radioactivity coincided with HER2-positive regions. Furthermore, [(68)Ga]Df-anti-HER2 scFv helped visualize HER2-positive xenografts and monitor the changes in HER2 expression after anti-HER2 therapy.
  
  
  CONCLUSIONS
  [(68)Ga]Df-anti-HER2 scFv could be a promising probe to evaluate HER2 status by in vivo PET imaging, unless trastuzumab is prescribed as part of the therapy.
authors.affiliation: Radioisotopes Research Laboratory, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Ueda
authors.forename: Hayato
authors.initials: H
authors.lastname: Hisada
authors.forename: Takashi
authors.initials: T
authors.lastname: Temma
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kimura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ono
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakamoto
authors.forename: Kaori
authors.initials: K
authors.lastname: Togashi
authors.forename: Hideo
authors.initials: H
authors.lastname: Saji
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000737:chemistry; D003676:Deferoxamine / Q000737:chemistry; D005260:Female; D005708:Gallium / Q000737:chemistry; D005710:Gallium Radioisotopes / Q000737:chemistry*; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000737:chemistry; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D057127:Single-Chain Antibodies / Q000737:chemistry*; D014018:Tissue Distribution
chemical_list: D002614:Chelating Agents; D003676:Deferoxamine; D005708:Gallium; D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals; D018719:Erb-b2 Receptor Tyrosine Kinases; D057127:Single-Chain Antibodies; C508053:ERBB2 protein, human