Human kappa-casein as a tumor marker: purification and properties

To test the efficacy of kappa-casein as a marker of human malignancy, a protein human milk, ostensibly kappa-casein, has been purified and serum levels determined, by RIA, in normal subjects, breast cancer patients, and lactating women. The results do not support claims by other workers for this protein. Concurrent physicochemical characterization of the protein has shown that it is probably lactoferrin and this result casts some doubt on the earlier studies as it is a major, non-beta component of the casein fraction. It also indicates that caution should be exercised when homology between proteins is used as a guide to identity.