In vitro expression of suppressogenic and enhancing activities in human colon cancer cells.

The presence of immunoregulatory factors in a human colon cancer cell line, LS174T, was exhibited in mitogenic and immunogenic assays. The simultaneous presence of stimulatory and suppressive factors in the spent media of LS174T colon cancer cells was shown. Opposing suppressive and stimulatory activities were extractable from viable tumor cells and found in 3 M KCl extracts fractionated by isoelectric focusing. Suppressogenic activity was demonstrated in concanavalin A and phytohemagglutinin mitogenesis in both human and murine lymphocytes; the blastogenesis of mixed lymphocyte culture reactions was suppressed, while responses of immune cells were not. Naive lymphocytes were stimulated or not affected by the same spent media. The factors appeared to require cell viability for optimal expression and were not species specific. These results further illustrate the complexity of tumor cell-host cell interactions and emphasize the need for in vitro assays to measure, characterize, and exploit the factors.