The comparative distribution of monoclonal antibodies to CEA in colorectal xenografts.

The in vivo distribution of three different, parenterally administered, monoclonal antibodies to CEA was studied in MAWI human colorectal tumour xenografts. By the use of conventional autoradiography, more antibody was generally detected within necrotic areas, extracellular spaces and stromal connective tissue than within tumour cells. However, some peripheral tumour cell groups markedly accumulated anti-CEA. The number of such groups involved and the degree to which antibody was internalised varied widely with the antibody studied. Immunoperoxidase staining of the same preparations showed that antibody accumulation did not necessarily correspond to CEA-positivity. These findings are compared with results of previous work with polyclonal anti-CEA, and discussed in relation to the use of anti-CEA's as carriers to deliver cytotoxic agents into colorectal tumours.