[Isolation of soluble tumor-associated antigens of human malignant melanoma]

Experiments were started with an animal model: Tumor antigens could be solubilized from fibrosarcomas of inbred guinea pigs by extraction with physiological saline. Extracts were fractionated by ammoniumsulfate precipitation, gel filtration, ion exchange chromatography, and polyacrylamide electrophoresis. Skin tests and leucocyte migration assays could detect antigenic activity in a number of fractions different with respect to size and charge. A less heterogeneous antigen could be extracted with phenol-water from guinea pig fibrosarcomas. Tumor associated antigens could be demonstrated in phenol-water extracts of human melanoma by leucocyte migration tests. Weak migration reactions were found with leucocytes from melanoma patients, not with leucocytes from controls. The frequency of positive results was similar in patients with and without metastases. No antibodies against antigens of phenol-water extracts could be detected in sera from melanoma patients. No antibodies against tumor associated substances could be demonstrated after immunization of rabbits with phenol-water extracts. Antigens extracted by phenol-water seem to be weak immunogens. Radioactive antigens were extracted from membranes of labelled cell cultures of human melanoma. Antigenic activity was assayed by double immune precipitation followed by sodium-dodecylsulfate-polyacrylamide-electrophoresis. Yields from available cell quantities were too small for further purification and clinical studies.