The distribution of parenterally administered antibody to CEA in colorectal xenografts. Preliminary findings.

Autoradiography was used to identify the distribution of parenterally administered anti-CEA in human colorectal tumours xenografted to nude mice. Four xenograft lines were studied: three mucinous adenocarcinomas of various degrees of differentiation and one undifferentiated tumour. 125Iodine-labelled, affinity purified goat anti-CEA was given intravenously to xenograft-bearing mice, who were killed at intervals thereafter up to 7 days. Autoradiograms were prepared by both conventional methods and the Appleton 'diffusible compound' technique which is designed to avoid possible translocation and extraction of labelled antibody tracer during tissue processing. Control experiments were done using a non-specific goat gamma-globulin. By combining autoradiography with a PAP-immunoperoxidase method of demonstrating CEA, anti-CEA was found to be preferentially retained at extracellular sites of CEA-positive material within viable tumour areas. Cell surface retention was not observed. At all times following administration more antibody was detected within necrotic areas, extracellular spaces and stromal connective tissue than within the tumour cell compartment. These preliminary results are discussed in relation to the possibility of using anti-CEA as a carrier to deliver chemotherapeutic agents into colorectal tumours. The suitability of diffusible compound and conventional autoradiography for studies of this nature are also examined.