ACTIVATION BY INTERFERON-GAMMA OF EXPRESSION OF ICAM-1 AND MHC CLASS-II ANTIGENS IN TUMOR-CELLS FROM COLORECTAL CARCINOMAS

Aims-To determine whether lack of MHC class IP antigen and intercellul ar adhesion molecule-1 (ICAM-1) expression in some tumours is due to t he inability of the tumour cells to respond to the cytokine interferon -gamma (IFN-gamma), an important activator of these surface molecules. Methods-Cells from 40 colorectal tumours which did not constitutively express class II MHC antigens or ICAM-1 were kept in short term cultu re after disaggregation for a few days to two weeks without significan t loss of viability. These were treated with IFN-gamma. Expression of class II MHC antigens and ICAM-1 was determined using immunohistologic al techniques. Results-There was clear induction in vitro of both MHC class II antigens and ICAM-1 in cells from eight of the tumours, with between 50 and 80% of the tumour cells in the cultures staining positi vely. The staining was apparent within 24 hours, appeared maximal at a bout three days, and declined thereafter. There were no obvious differ ences in cell. morphology or viability between the cultures which were inducible and those which were not, nor were there obvious difference s between the tumours from which they were derived. Conclusions-Expres sion of MHC class II antigens and ICAM-1 may be induced by IFN-gamma i n a small proportion of colorectal tumours which do not constitutively express these antigens, showing that only a minority of tumours are c apable of responding to this cytokine.