Radiolocalization of pancreatic carcinoma xenografts in nude mice with radiolabeled chimeric Fab fragments of anti-carcinoembryonic antigen monoclonal antibody A10

Recombinant mouse-human chimeric Fab fragments of anti-carcinoembryonic antigen monoclonal antibody (MAb) A10 react with various GI carcinomas. We tested radiolocalization of pancreatic carcinoma xenografts in nude mice using radiolabeled chimeric A10 Fab fragments, comparing them with murine Fab fragments and parental MAb. For mice injected with chimeric A10 Fab fragments, we obtained significantly higher uptake in tumors than in normal tissues at 24 and 48 h after injection. In addition, tumor/normal tissues labeling ratios for chimeric A10 Fab fragment were significantly greater than those for murine MAb at 24 h postinfusion. However, no significant difference in biodistribution was observed between chimeric and murine Fab fragments. In autoradiography imaging studies, we obtained clearer tumor detection without visible uptake in normal organs for chimeric Fab fragments than for murine MAb. These results suggest that chimeric Fab fragments of A10 could be a potentially useful candidate for radioimmunodetection of pancreatic carcinomas.