Suppression of the growth of human colorectal carcinoma cells (LS174T) by radiolabeled monoclonal antibody (131I-MAbC27) in tissue culture and nude mice.

A monoclonal antibody against carcinoembryonic antigen (CEA), MAbC27, and its F(ab')2 fragments were prepared and labeled with 131I. They effectively suppressed the growth of a human colorectal carcinoma cell line, LS174T, both in culture medium and in inoculated nude mice, whereas 131I-labeled normal mouse immunoglobulin or 131I itself did not have similar effects. Intravenous injection of 131I-MAbC27 or 131I-MAbF(ab')2 following inoculation of carcinoma cells suppressed their growth in vivo. The suppression effect was even more effective when intact antibody rather than its F(ab')2 fragments was used, especially when the treatment was repeated. This study indicates that radiolabeled MAbC27 may be used as a therapeutic agent in CEA-secreting human colorectal carcinomas.