The membrane antigens of human colorectal cancer cells: demonstration with monoclonal antibodies of heterogeneity within and between tumours and of anomalous expression of HLA-DR.

The membrane antigens of fifteen colorectal tumours were studied using a number of monoclonal antibodies and the immunoperoxidase technique on frozen sections. With this approach we could easily demonstrate differences in the membrane structure of the cancer cells within the tumour mass of given patients and also readily demonstrate differences between tumours that were indistinguishable by histological and other standard criteria. An unexpected finding was the patchy expression of HLA-DR antigens on cancer cells, in spite of the absence of HLA-DR on normal colorectal epithelium. These findings have interesting theoretical and clinical implications.