125I-F56 Peptide as Radioanalysis Agent Targeting VEGFR1 in Mice Xenografted with Human Gastric Tumor.

125I-Radiolabeled F56 peptide was designed as a radioactive analogue of F56 (peptide WHSDMEWWYLLG) to bind with VEGFR1 receptor. It was synthesized in high radiochemical yield and specific activity. The in vitro stability of 125I-F56 was tested, and the bioactivity of 125I-F56 was confirmed by both cell uptake and binding affinity measurement in VEGFR1 positive BGC-823 cells. The time-radioactivity relationship and biodistribution of 125I-F56 tracer were conducted using nude mice bearing human gastric carcinoma BGC-823, by noninvasive micro-SPECT/CT imaging. The tracer's tumor uptake was further confirmed by autoradiography and HE stain of 125I-F56 in tumor tissues ex vivo. Those results demonstrated that 125I-F56 holds great potential as a diagnostic agent in both molecular imaging and radioanalysis probe for gastric cancer.