An evaluation of leucocyte adherence inhibition microassay using colorectal cancer cell lines

The leucocyte adherence inhibition (LAI) microassay using crude extracts from colorectal cancer cell lines (M-7609 and S-7512) was evaluated as a test of immunological antitumor reactivity in colorectal cancer patients. The optimal antigen concentration for differentiating cancer patients from control subjects was 0.05 mg/ml protein. The cut-off values of LAI index for determining reactive and nonreactive cases was -0.20. The numbers of colorectal cancer patients reactive against antigens M (derived from M-7609), S (derived from S-7512) and M + S were 9 of 19, 9 of 12 of 18, respectively, whereas against control antigens K (derived from K-7610, pulmonary cancer), SF (derived from cultured fibroblastic cells) and T (derived from fresh colorectal cancer tissue), they were only 1 of 18, 1 of 17, and 3 of 15, respectively. The mean LA indices of the Dukes A and B group, and of the Dukes C and recurrent cancer group were -0.28 and -0.24, but that of a tumor-free postoperative group, another malignant disease group and a group of healthy individuals were -0.04, -0.05, and -0.03, respectively. Judging from these results, LAI microassay using cultured human cancer cell lines as tumor antigen sources is suitable as a test for evaluating the antitumor immunmoreactivity of colorectal cancer patients.