title: PET with the 89Zr-labeled transforming growth factor-β antibody fresolimumab in tumor models.
abstract: Transforming growth factor-β (TGF-β) promotes cancer invasion and metastasis and is therefore a potential drug target for cancer treatment. Fresolimumab, which neutralizes all mammalian active isoforms of TGF-β, was radiolabeled with (89)Zr for PET to analyze TGF-β expression, antibody tumor uptake, and organ distribution.
  
  
  METHODS
  (89)Zr was conjugated to fresolimumab using the chelator N-succinyldesferrioxamine-B-tetrafluorphenol. (89)Zr-fresolimumab was analyzed for conjugation ratio, aggregation, radiochemical purity, stability, and immunoreactivity. (89)Zr-fresolimumab tumor uptake and organ distribution were assessed using 3 protein doses (10, 50, and 100 μg) and compared with (111)In-IgG in a human TGF-β-transfected Chinese hamster ovary xenograft model, human breast cancer MDA-MB-231 xenograft, and metastatic model. Latent and active TGF-β1 expression was analyzed in tissue homogenates with enzyme-linked immunosorbent assay.
  
  
  RESULTS
  (89)Zr was labeled to fresolimumab with high specific activity (>1 GBq/mg), high yield, and high purity. In vitro validation of (89)Zr-fresolimumab showed a fully preserved immunoreactivity and long (>1 wk) stability in solution and in human serum. In vivo validation showed an (89)Zr-fresolimumab distribution similar to IgG in most organs, except for a higher uptake in the liver in all mice and higher kidney uptake in the 10-μg group. (89)Zr-fresolimumab induced no toxicity in mice; it accumulated in primary tumors and metastases in a manner similar to IgG. Both latent and active TGF-β was detected in tumor homogenates, whereas only latent TGF-β could be detected in liver homogenates. Remarkably high (89)Zr-fresolimumab uptake was seen in sites of tumor ulceration and in scar tissue, processes in which TGF-β is known to be highly active.
  
  
  CONCLUSIONS
  Fresolimumab tumor uptake and organ distribution can be visualized and quantified with (89)Zr-fresolimumab PET. This technique will be used to guide further clinical development of fresolimumab and could possibly identify patients most likely to benefit.
authors.affiliation: Department of Medical Oncology, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Thijs H
authors.initials: TH
authors.lastname: Oude Munnink
authors.forename: Marlous E A
authors.initials: ME
authors.lastname: Arjaans
authors.forename: Hetty
authors.initials: H
authors.lastname: Timmer-Bosscha
authors.forename: Carolina P
authors.initials: CP
authors.lastname: Schröder
authors.forename: Jan W
authors.initials: JW
authors.lastname: Hesselink
authors.forename: Silke R
authors.initials: SR
authors.lastname: Vedelaar
authors.forename: Annemiek M E
authors.initials: AM
authors.lastname: Walenkamp
authors.forename: Michael
authors.initials: M
authors.lastname: Reiss
authors.forename: Richard C
authors.initials: RC
authors.lastname: Gregory
authors.forename: Marjolijn N
authors.initials: MN
authors.lastname: Lub-de Hooge
authors.forename: Elisabeth G E
authors.initials: EG
authors.lastname: de Vries
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000493:pharmacokinetics; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016466:CHO Cells; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D006224:Cricetinae; D003412:Cricetulus; D004195:Disease Models, Animal; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007553:Isotope Labeling; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D011868:Radioisotopes; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015040:Zirconium
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D011868:Radioisotopes; D016212:Transforming Growth Factor beta; C560928:fresolimumab; D015040:Zirconium