The isolation of colon cancer organ specific neoantigen by the use of the leukocyte adherence inhibition assay and monoclonal antibodies.

The LAI reactivity of a colon organ specific neoantigen (OSN) was recovered from the urine of advanced colon cancer patients. In this study three physico-chemical steps were employed; precipitation by 80% ammonium sulfate, ion exchange, and molecular sieve chromatography. Each isolate was tested for activity and specificity by the direct tube leukocyte adherence inhibition (LAI) assay employing leukocytes from colon and breast cancer patients. The OSN enriched isolate was then used to generate monoclonal antibodies (Mab). Hybridomas were screened by ELISA. One hybridoma designated Bac 18.1 reacted preferentially with colon OSN and not with the urine from normals or patients with breast cancer. Affinity purification of colon OSN was achieved and it was shown to consist of a single band in SDS-PAGE with an apparent molecular weight of 30,000. The eluted polypeptide was specifically reactive in ELISA as well as in the LAI assay.