Membrane associated antigens of human malignant melanoma. I. Internal labeling, detergent solubilization and characterization by homologous antisera and polyacrylamide gel electrophoresis.

Cultured melanoma cells were labeled with 3H-leucine over a period of 1-3 days. The labeled cells were mechanically disrupted and a preparation of "extranuclear membranes" was obtained by differential centrifugation. The membrane fragments were solubilized by the nonionic detergent NP-40 and the soluble material was double precipitated with antisera from melanoma patients and anti-human immunoglobulin sera. Because of the small quantitative differences of precipitated radiolabeled material between control and melanoma patients' sera, the precipitates were further analyzed on SDS-containing polyacrylamide gels. The labeled profiles of experimental and control gels now revealed clearcut differences usually seen in 2-3 characteristic peaks in the molecular weight range from 130,000-330,000.