Localization of human colorectal carcinoma xenografts in mice using radiolabeled monoclonal antibody to carcinoembryonic antigen.

A mouse IgG1 monoclonal antibody (MAbC27) with high affinity for human carcinoembryonic antigen (CEA) has been used in vitro and in vivo for study of human colorectal carcinoma (CRC). After introduction to tumor-bearing mice, the distribution of radiolabeled MAbC27 and its F(ab')2 fragments was analyzed by direct measurement of radioactivity in the tumor and in normal organs as well as by whole-body scanning. Radiolabeled MAbC27 and its F(ab')2 were used successfully in localizing tumor xenografts in mice 40 and 20 hr after inoculation, respectively. A tumor as small as 60 mg (4.2 mm in diameter) was visualized by labeled F(ab')2. Circulating CEA, up to 200 micrograms per mouse did not prevent successful tumor imaging. This study indicates that the MAbC27 is highly useful in detection and localization of CRC in mice.