Monoclonal antibody detection of a circulating tumor-associated antigen. I. Presence of antigen in sera of patients with colorectal, gastric, and pancreatic carcinoma.

Hybridoma-secreted monoclonal anti-colorectal carcinoma antibodies 19-9, 52a, and C4 14 bind specifically to cells of colorectal, gastric, and pancreatic carcinoma in tissue culture. The assay for the detection of antigen in human sera is based on the inhibition of binding of monoclonal antibodies to target preparations of colorectal carcinoma cells. Binding of monoclonal antibody 52a was inhibited more than 12% by 163 of 255 sera from patients from various stages of carcinoma of colon and rectum, by 45 of 49 sera from patients with pancreatic carcinoma, and by 8 of 11 sera from patients with gastric carcinoma. By contrast, only 7 of 89 sera from patients with other malignancies and 2 of 108 sera from healthy donors inhibited binding of this monoclonal antibody by more than 12%. These studies show the potential usefulness of monoclonal antibodies in the diagnosis of human malignancy.