Loss of HLA-A,B,C and de novo expression of HLA-D in colorectal cancer.

One hundred primary colorectal carcinomas and 19 metastases were studied for the expression of HLA-A,B,C and HLA-D antigens using monoclonal antibodies (MAbs) against framework determinants and a sensitive immunoperoxidase technique on frozen sections. With MAb W6/32, 65 tumors were intensely stained for HLA-A,B,C; 22 showed a reduced staining intensity, in 5 carcinomas a minor or major subset of the tumor cells lacked HLA-A,B,C, and in 8 cases all tumor cells were unreactive. The loss of HLA-A,B,C was inversely correlated with the degree of differentiation. No relation was found to type, stage and site of the tumor, or to age and sex of the patients. With MAb 2.06, 58 tumors were HLA-D negative, 20 exhibited small positive foci, 19 showed a patchy staining pattern, and 3 were homogeneously HLA-D positive. There was no apparent correlation between HLA-D expression and any of the clinico-pathological features mentioned, nor was it related to the loss of HLA-A,B,C. About half of the metastases displayed the same staining pattern for HLA-A,B,C and -D as the respective primary tumors. The remainder differed from the primary carcinoma by gain or loss of HLA antigens.