Colon-specific antigen-p (CSAp). II. Further characterization in colorectal and pancreatic cancer.

The physicochemical and immunological characteristics of colon-specific antigen-p (CSAp) in plasma and in colorectal and pancreatic tumors were investigated. CSAp in the plasma of a rectal cancer patient and in a colonic carcinoma xenografted in hamsters (GW-39 tumor) appeared to have similar chromatographic properties, being of a molecular size of 4 million or more. The activities of CSAp in both plasma and tumor were similarly destroyed by treatment with a thiol reagent. Finally, identical immunological reactions in radioimmunoassay and gel diffusion tests were obtained between the CSAp's in patient plasma and in GW-39 tumor tissue. Also CSAp in human pancreatic cancers xenografted in nude mice showed a precipitin line of complete identity with CSAp extracted from GW-39 human colonic carcinoma transplants. Thus, the CSAp's found in colorectal cancer patient plasma, in colonic carcinoma, and in pancreatic cancer tissues appear to be immunologically identical.