CEA expression of colorectal adenocarcinomas is correlated with their resistance against LAK-cell lysis

We have investigated the in vitro interaction of LAK cells with 20 different human tumor cell lines freshly isolated from colorectal carcinoma (CRC) specimens. Three steps of LAK cell/tumor cell interaction, namely adherence, infiltration and lysis, have been studied. All are important for the cytotoxic effect of LAK cells against solid tumors: LAK-cell adherence was studied on tumor-cell monolayer cultures, the infiltration capacity of LAK cells using tumor-cell spheroids and the resulting cytotoxic effects of LAK cells against CRC cells grown as spheroids or monolayers. Finally, we correlated the degree of lysis of the CRC cells with their carcinoembryonic antigen (CEA) production, the secretion of which varied in a broad range from not detectable to 2,800 ng/day in culture medium. Cytotoxicity experiments showed a good correlation between CEA expression of CRC cells and their resistance against allogeneic LAK cells. Spheroids of CEA-producing cells prevented LAK-cell infiltration resulting in high resistance against LAK-cell lysis. Adhesion of LAK cells on monolayers of CEA-expressing CRC cells was minimal. Our results indicate that CEA expression may be an escape mechanism protecting colon carcinoma cells from an attack by cytotoxic cells.