Immunochemical characterization of murine B16 melanoma-associated antigens and their detection in sera of tumor-bearing hosts by radioimmunoassay.

Radioimmunoassay, using radiolabeled melanoma-associated antigens (MAA), rabbit anti-B16 melanoma serum and Staphylococcus aureus Cowan I, was developed for the detection of MAA in tumor tissues as well as in sera of B16 melanoma-bearing C57BL/6 mice. MAA were partially purified from 3 M KC1 extract of murine B16 melanoma tissue by affinity column chromatography using anti-B16 serum and concanavalin A. The content of MAA was high in B16 melanoma extract, much less in allogeneic Harding Passey melanoma, and very small in fetal and normal tissues including skin and brain. The amount of circulating MAA released from the tumor into the blood of B16 tumor-bearing C57BL-6 mice was linearly proportional to the size (cube root of weight) of the growing tumor, providing a rational basis for immunodiagnosis of malignant melanoma. Immunochemical data suggest that MAA which are extractable with 3M KC1 from B16 melanoma are glycoproteins with molecular weights of 54,000, 68,000 and 94,000 daltons.