PT - JOURNAL ARTICLE AU - Vladimir Tolmachev AU - Zohreh Varasteh AU - Hadis Honarvar AU - Seyed Jalal Hosseinimehr AU - Olof Eriksson AU - Per Jonasson AU - Fredrik Y. Frejd AU - Lars Abrahmsen AU - Anna Orlova TI - Imaging of Platelet-Derived Growth Factor Receptor β Expression in Glioblastoma Xenografts Using Affibody Molecule <sup>111</sup>In-DOTA-Z09591 AID - 10.2967/jnumed.113.121814 DP - 2014 Feb 01 TA - Journal of Nuclear Medicine PG - 294--300 VI - 55 IP - 2 4099 - http://jnm.snmjournals.org/content/55/2/294.short 4100 - http://jnm.snmjournals.org/content/55/2/294.full SO - J Nucl Med2014 Feb 01; 55 AB - The overexpression and excessive signaling of platelet-derived growth factor receptor β (PDGFRβ) has been detected in cancers, atherosclerosis, and a variety of fibrotic diseases. Radionuclide in vivo visualization of PDGFRβ expression might help to select PDGFRβ targeting treatment for these diseases. The goal of this study was to evaluate the feasibility of in vivo radionuclide imaging of PDGFRβ expression using an Affibody molecule, a small nonimmunoglobulin affinity protein. Methods: The PDGFRβ-binding Z09591 Affibody molecule was site-specifically conjugated with a maleimido derivative of DOTA and labeled with 111In. Targeting of the PDGFRβ-expressing U-87 MG glioblastoma cell line using 111In-DOTA-Z09591 was evaluated in vitro and in vivo. Results: DOTA-Z09591 was stably labeled with 111In with preserved specific binding to PDGFRβ-expressing cells in vitro. The dissociation constant for 111In-DOTA-Z09591 binding to U-87 MG cells was determined to be 92 ± 10 pM. In mice bearing U-87 MG xenografts, the tumor uptake of 111In-DOTA-Z09591 was 7.2 ± 2.4 percentage injected dose per gram and the tumor-to-blood ratio was 28 ± 14 at 2 h after injection. In vivo receptor saturation experiments demonstrated that targeting of U-87 MG xenografts in mice was PDGFRβ-specific. U-87 MG xenografts were clearly visualized using small-animal SPECT/CT at 3 h after injection. Conclusion: This study demonstrates the feasibility of in vivo visualization of PDGFRβ-expressing xenografts using an Affibody molecule. Further development of radiolabeled Affibody molecules might provide a useful clinical imaging tool for PDGFRβ expression during various pathologic conditions.