Detection of tumor‐associated antigen in human melanoma cell line supernatants

Spent tissue culture medium (CDM‐S) removed from a single cell line of human malignant melanoma grown in serum‐free CDM, contained tumor‐associated antigenic activity. Antibodies to CDM‐S measured by complement fixation were detected in 44% (31/70) melanoma, 55% (15/27) sarcoma, 63% (24/38) carcinoma and 15% (11/72) normal sera. Delayed cutaneous hypersensitivity reactions (DCHR) were demonstrated in 4/5 melanoma patients at a 500 μg dose, 3/5 at a 100 μg dose and in 1/7 carcinoma patients at the 500 μg dose. One ml of CDM‐S was shown to contain antigen equivalent to that obtained from the membranes of 2.9 × 10 7 tissue‐cultured melanoma cells. After purification, 84% (16/19) sera from melanoma patients, 66% (12/18) from sarcoma and carcinoma patients and 8% (2/26) from normal controls were positive to the antigen by complement fixation.