Tumour-associated antigens in culture medium of malignant melanoma cell strains

Summary The presence of melanoma-associated antigens naturally shed from cultured melanoma cells in spent culture medium was investigated by means of a leukocyte migration test and culture medium from four melanoma and two control cell strains.Leukocytes from 29/64 melanoma patients showed a positive reaction with spent culture medium from at least one melanoma cell strain, whereas leukocytes from only 4/25 patients with other cancers and 1/30 normal donors reacted. On the other hand, leukocytes from only 8/51 melanoma patients reacted with control culture medium. Only melanoma patients' leukocytes reacted with two or more of the melanoma cell strains used. Culture media from two melanoma cell strains were more reactive (25.3% and 29.4% positive tests with melanoma patients' leukocytes) than others (12.5% and 17.2% positive tests); this may represent either a qualitative difference (i.e., different antigens) or a quantitative one (i.e., different levels of antigen expression according to tissue culture conditions). Both inhibition and stimulation of migration were observed, but with one exception, on a given occasion, leukocytes from the same donor always reacted in the same way (i.e., either inhibition or stimulation). Migration stimulation was observed mainly with melanoma patients' leukocytes, and more especially when leukocytes were sampled from patients within a few weeks from tumour removal; migration stimulation may thus reflect a particular state of sensitization in patients.From the evidence obtained in these studies, it is concluded that spent culture medium from melanoma cell strains contains melanoma-associated antigen (s) that is (are) reactive in the leukocyte migration test and that this may contribute to the study of specific antitumour reactivity in patients and to the study and purification of tumour-associated antigens by providing an homogeneous source of antigens spontaneously released from tumour cells in conditions close to natural ones.