Murine colon adenocarcinoma: immunobiology of metastases.

Orthotopic transplantation of MCA-39 murine colonic tumor cells into the submucosa of the cecum results in the growth of a "primary" tumor that metastasizes to the liver. This model system parallels the sequence of events that can occur with human colon carcinoma and provides a means of evaluating the role of the immune system in hepatic metastases formation. Temporal studies of the specific antitumor response detected by a micro-leukocyte adherence inhibition (LAI) assay revealed two patterns of sensitization as the "primary" tumor grew and hepatic metastases developed. The systemic antitumor response was monophasic and disappeared prior to the formation of hepatic metastases. In contrast, the local and regional antitumor response was biphasic. The breakdown in the local and regional response may play a permissive role in the formation of hepatic metastasis.