Imaging of Protein Synthesis: In Vitro and In Vivo Evaluation of 44Sc-DOTA-Puromycin

The purpose of this study was to investigate whether Sc-44-labeled puromycin can be utilized for imaging of protein synthesis in vivo. For micro-positron emission tomographic (mu PET) studies, 20-25 MBq of [Sc-44]-DOTA-puromycin was administered to tumor-bearing rats, and animals were scanned for 1 h dynamically. Results were further validated by dissecting organs and tissues of the animals after the measurement and in vitro blocking experiments using puromycin or cycloheximide to block protein synthesis. mu PET images of tumor-bearing rats showed significant tumor uptake of [Sc-44]-DOTA-puromycin and a clear-cut tumor visualization. In both blocking experiments, cellular uptake of [Sc-44]-DOTA-puromycin ([Sc-44]-DOTA-Pur) could be suppressed by blocking protein synthesis. We report for the first time successful mu PET imaging with Sc-44 obtained from a Ti-44/Sc-44 generator, as well as noninvasive mu PET imaging of ribosomal activity, respectively protein synthesis, with a puromycin-based radiopharmaceutical and the direct correlation between cellular uptake of [Sc-44]-DOTA-Pur and protein synthesis.