Development of 68Ga-Glycopeptide as an Imaging Probe for Tumor Angiogenesis

Objective. This study was aimed to study tissue distribution and tumor imaging potential of68Ga-glycopeptide (GP) in tumor-bearing rodents by PET.Methods. GP was synthesized by conjugating glutamate peptide and chitosan. GP was labeled with68Ga chloride for in vitro and in vivo studies. Computer outlined region of interest (counts per pixel) of the tumor and muscle (at the symmetric site) was used to determine tumor-to-muscle count density ratios. To ascertain the feasibility of68Ga-GP in tumor imaging in large animals, PET/CT imaging of68Ga-GP and18F-FDG were conducted in New Zealand white rabbits bearing VX2 tumors. Standard uptake value of tumors were determined by PET up to 45 min. To determine blood clearance and half-life of68Ga-GP, blood samples were collected from 10 seconds to 20 min.Results. Radiochemical purity of68Ga-GP determined by instant thin-layer chromatography was >95%. Tumor uptake values (SUV) for68Ga-GP and18F-FDG in New Zealand white rabbits bearing VX2 tumors were 3.25 versus 7.04. PET images in tumor-bearing rats and rabbits confirmed that68Ga-GP could assess tumor uptake. From blood clearance curve, the half-life of68Ga-GP was 1.84 hr.ConclusionOur data indicate that it is feasible to use68Ga-GP to assess tumor angiogenesis.