PET Imaging of FSHR Expression in Tumors with 68Ga-Labeled FSH1 Peptide

FSHR is an appealing target for cancer theranostics. Radiolabeled FSH1 and its derivatives have shown potential to in vivo detect FSHR expression. However, moderate labeling yields (~50% nondecay-corrected) may partially limit their wide use. 68Ga is an excellent PET nuclide due to availability, nearly quantitative reaction, and short physical half-life. In this study, 68Ga labeled FSH1 peptide was developed for imaging of FSHR in cancers. In vitro studies and MicroPET imaging were performed in PC-3 prostate tumor model. [68Ga] Ga-NOTA-MAL-FSH1 can be produced within 20 min with yield and the radiochemical purity was greater than 95%. It showed that [68Ga] Ga-NOTA-MAL-FSH1 possessed FSHR binding affinities. The tracer was stable in PBS and human serum for at least 2 hours. MicroPET imaging revealed that the PC-3 xenografts were clearly visualized and the tumor uptakes were , , and % ID/g at 0.5, 1 h, and 2 h postinjection. The corresponding tumor to blood and tumor to muscle ratios were , , and and , , and , respectively. FSHR binding specificity was also demonstrated by reduced tumor uptake of [68Ga] Ga-NOTA-MAL-FSH1 after coinjecting excess unlabeled FSH1 peptide. The favorable characters of [68Ga] Ga-NOTA-MAL-FSH1 such as convenient synthesis and specific tumor uptake warrant its further investigation for FSHR expression imaging.