[Radioimmunodetection of 188Re-labeled anti-carcinoembryonic antigen chimeric antibody in nude mice bearing human colon carcinoma].

Background & Objective: Carcinoembryonic antigen(CEA), is highly expressed in many kinds of carcinomas, especially in colon carcinoma. Anti-CEA antibodies have great application in diagnosis and therapy of the patients with colon carcinoma. This study was designed to investigate the biodistribution and radioimmunodetection in nude mice bearing human colon carcinoma using 188Re-labeled anti-CEA chimeric antibody.
Methods: CEA chimeric antibody and its parent McAb C50 were labeled with 188Re by a stannous chloride reduction method. The radiochemical purity of them were determined by ITLC. The biodistribution and whole body gamma scintigraphy imaging of 188Re-CEA chimeric antibody in nude mice bearing human colon carcinoma were fulfilled. The effect of radioimmunoimage between these two antibodies was compared.
Results: 188Re-CEA chimeric antibody showed high radiochemical purity of more than 95%. The specific reactivity of 188Re-CEA chimeric antibody was 356 MBq/mg. Immunoreactivity of 188Re-CEA chimeric antibody was 61% as determined by ELISA. Tumor/kidney ratio (0.75) and tumor/blood ratio(0.99) of 188Re-CEA chimeric antibody were observed in 24 h; compared to the orther organs, the ration is over 1.78. Tumor/kidney ratio (1.02) and tumor/blood ratio (1.12) of 188Re-CEA chimeric antibody were observed in 48 h; compared to the other organs more than 2.08. High uptake of 188Re-CEA chimeric antibody was observed in 20 hours after injection. The radioimmunodetection effect of these two antibodies was approximately same.
Conclusions: 188Re-CEA chimeric antibody showed high specific tumor uptake and could fast display clear image in the nude mice bearing human colon carcinoma. Comparing with McAb C50, CEA chimeric antibody has good effect in clinic because of reducing of immunogenicity.