The biodistribution and pretargeting radioimmunoimaging of the fusion protein of anti-CEA single-chain antibody and core-streptavidin in human rectocolonic tumor bearing nude mice

ObjectiveTo investigate the biodistribution and two-step pretargeting radioimmunoimaging of the fusion protein of anti-carcinoembryonic antigen (CEA) single-chain antibody (ScFv) and core-streptavidin in human rectocolonic tumor bearing nude mice. MethodsBefore the injection of 153Sm-biotin, the fusion protein of ScFv-core-streptavidin was pretargeted for 24 h (200 μg every nude mouse), 24 h later 153Sm-biotin was injected. The uptake of radioactivity in tumor and normal tissues in 20 nude mice was measured at 1,4,8 and 24 h and the other 3 nude mice was scanned at 8 and 24 h after peritoneal injection of 153Sm-biotin. ResultsTBThe tumor to blood ratio ( tumor/blood) reached 0.49, 1.21, 1.56 and 3.09 at 1, 4, 8 and 24 h respectively. Radioactivity concentration peaked at 8 h in tumor site and demonstrated a 'hot' area, with significant decreasing its background at 24 h. ConclusionThe fusion protein can elevate the tumor/blood ratio, shorten pretargeting and imaging process and also improve image quality.