Detection of tumor antibodies in patients with gastrointestinal carcinomas by a solid-phase radioimmunoassay.

Metastatic tumors from livers of 5 patients with gastrointestinal carcinomas and from the liver of 1 patient with malignant breast carcinoma were extracted with 3 M KCl; similar extracts were prepared from normal human colon and liver and from human fetal gut. The extracts were depleted of serum globulins by passage through reverse immunoadsorbent columns consisting of rabbit antibodies to the F(ab)2 fragment of human IgG and were then coupled to CNBr-activated paper disks. These "antigen" disks were used in a radioimmunoassay, with the aid of 125I-labeled rabbit antihuman F(ab')2 antibodies for the assay of circulating tumor antibodies produced by cancer patients. Statistical evaluation of the results with plasma samples from 47 patients with colorectal carcinomas and from 7 patients with other gastrointestinal disorders (polyps, villous papilloma, diverticulitis, and Crohn's disease) indicated that a significant number of patients had antibodies to cross-reactive tumor antigen(s). The cross-reactive tumor antigen(s) involved in the reaction was not detected in extracts of the gastrointestinal tract from 12-week human fetuses and did not cross-react with carcinoembryonic antigen.