The spatial distribution of parenterally administered monoclonal antibodies against CEA in a human colorectal tumour xenograft.

A recently developed experimental model consisting of athymic rats carrying human colonic tumours from the cell line LS 174 T in both hind legs was used. 125I-labelled anti-carcinoembryonic (anti-CEA) monoclonal antibodies were injected either intra-arterially after a bolus injection of mannitol, or intra-peritoneally with or without mannitol. On the fourth day the rats were killed and pieces from the tumours and various organs were measured in a well scintillation counter. Tumour pieces were then submitted to autoradiography and immunohistochemistry for examination of the antibody distribution at the cellular level. In all examined tumours injected with anti-CEA antibodies, most of the antibodies were located in the periphery close to fibrovascular septa. It appears, in addition to the specificity of the antibody for the CEA, that the tumour vascular permeability and anatomy are of utmost importance for tumour targeting in this experimental model with the particular antibody used.