Evaluation of the radiocobalt-labeled [MMA-DOTA-Cys61]-Z HER2:2395(-Cys) affibody molecule for targeting of HER2-expressing tumors.
OBJECTIVE
Imaging using positron emission tomography (PET) in the field of nuclear medicine is becoming increasingly important. The aim of this study was to develop a method for labeling of affibody molecules with radiocobalt for PET applications.


METHODS
The human epidermal growth factor receptors type 2 (HER2) binding affibody molecule DOTA-Z(2395)-C was radiolabeled with (57)Co (used as a surrogate of (55)Co). The binding specificity and cellular processing of the labeled compound was studied in vitro followed by in vivo characterization in normal and tumor-bearing mice. Furthermore, a comparative biodistribution study was performed with a (111)In-labeled counterpart.


RESULTS
DOTA-Z(2395)-C was successfully labeled with radiocobalt with nearly quantitative yield. The compound displayed good retention on cells over time and high tumor accumulation of radioactivity in animal studies. Imaging studies showed clear visualization of HER2-positive tumors. Furthermore, the radiocobalt label provided better tumor-to-organ ratios than (111)In.


CONCLUSIONS
Radiocobalt is a promising label for affibody molecules for future PET applications.
Wållberg
Helena
H
Affibody AB, Bromma, Sweden.
Ahlgren
Sara
S
Widström
Charles
C
Orlova
Anna
A
D000818:Animals; D045744:Cell Line, Tumor; D003037:Cobalt Radioisotopes; D015902:Gamma Cameras; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
D003037:Cobalt Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C508053:ERBB2 protein, human