Experimental study of affinity of radioiodine labeling APRPGY peptide for tumor angiogenesis

The purpose is to investigate the characteristics of APRPGY peptide labeled with radioiodine homing to tumor angiogenesis. The preparation of radioiodinated APRPGY was carried out by Ch-T method. Radiochemical purity was determined by the paper chromatographic system. Biodistribution studies were accomplished using wound healing model and tumor bearing model ICR mice. At 5, 10, 30, 60, 120 and 240 min after radiopharmaceutical administration (174 kBq/200 μL of 131I-APRPGY), the animals were sacrificed. Blood samples and other interested tissues were collected, weighted and counted (n=6 animals each time). The percent injected dose per gram of organ (%ID/g) and the ratio of tumor/muscle for each animal were calculated. The radiochemical purity of the 131I-APRPGY was above 95%. The biodistribution of the radiolabeled peptide showed higher levels in both blood and kidneys than in other tissues. In all other organs, the radioactivity was rapidly excreted mainly by kidneys. The accumulation of radioactivity in the tumor was 6.7%ID/g at 10 min and decreased within 240 min to 2.1 %ID/g. The ratios of tumor/muscle of 131I-APRPGY were 2.1, 6.2, 3.3, 3.5 and 3.2 at 5, 10, 60, 120 and 240 min, respectively. In would healing model, the radios of would-healing tissue/muscle were 0.8, 1.3, 1.8, 1.9 and 1.4 at 10, 30, 60, 120 and 240 min, respectively. The high specific tumor uptake and predominantly renal excretion make 131I-APRPGY a potential candidate for tumor angiogenesis imaging. This peptide is therefore worthy of further investigation. (authors)