Preliminary study of a novel FAP-targeted ligand ⁶⁸Ga-DOTA-FL in colon cancer imaging using small-animal PET/CT

Purpose This study explored the feasibility of (68)gallium (Ga)-labeled novel fibroblast activation protein (FAP)-targeted ligand for tumor imaging through small-animal PET/CT (positron emission computed tomography/computed tomography).Methods The FAP-ligand (FL) was created by adding the chelating group dodecane tetraacetic acid (DOTA) and labeling with Ga-68. The MC38 cell line was used to establish a C57BL/6 mice colon cancer model. The radioactivity distribution of labeled Ga-68-DOTA-FL across various organs of the mouse model was examined ex-vivo. In addition, Ga-68-DOTA-FL tumor-targeted imaging in vivo was performed using small-animal PET/CT. Finally, western blotting and immunofluorescence imaging of MC38 cells and xenotransplant tumor tissues were conducted.Results The radiolabeling rate and radiochemical purity of Ga-68-DOTA-FL were above 95%. Both western blotting and immunofluorescence imaging revealed FAP expression in the tumor tissues, but not in the MC38 cells. Small-animal PET/CT imaging indicated that the tumor imaging was clearest at 30 min after Ga-68-DOTA-FL treatment. Examination of the radioactivity distribution in vitro revealed that at 30 min after the Ga-68-DOTA-FL treatment, the target/non-target ratio for tumor and muscle tissue was 4.0 +/- 0.3 (n = 3).Conclusions Ga-68-DOTA-FL can be used for the specific tumor imaging in mouse models, which might provide a novel alternative for FAP-targeted tumor imaging.