Distribution of Mixture of Anti-CEA and Anti-CA 19-9 F(ab')₂Antibodies in Human Tumor Xenograft

Abstract

The in vivo localization of a mixture of radioiodinated monoclonal antibody F(ab')z fragments of CEA and CA 19-9 was investigated in human colon cancer xenograft in nude mice. Scintigrams were taken 3 and 5 days after injection of 131I-labeled fragments in mice bearing transplanted tumor. Mice were killed afterward and the radioactivity in each tissue was analysed. Whole body scintigraphy clearly demonstrated selective localization of radioactivity over transplanted tumor without background subtraction with tumor:nontumor ratio of upto 3:1. Though' absolute count in tumor of day 5 was lower than that of day 3, tumor to nontumor tissue ratio of day 5 was higher than that of day 3. Fragment of both monoclonal antibodies preferentially localized in tumor tissue compared with normal mouse IgG, as determined by differential tissue counting of radioactivity, The tumor to blood ratio for specific antibodies was much greater than that for normal IgG after injection. It is concluded that a radioactively labeled mixture of anti-CEA and anti-CA 19-9 antibodies is accumulated by colon carcinoma and that radioimmunodetection using gamma camera seemed to be useful for the detection of human tumor.