Brief Communieofion: Differentiation of Melanocytes in Cultures of Primary Malignant

SUMMARY-The dedifferentiation of cultured primary human malignant melanocytes was not accompanied by disappearance of 5-S-cysteinyldopa formation. The addition of conditioned medium from undifferenti'ated fibroblast-Hke cells brought about the reappearance of pigmented melanocytes and the in-crease of the metabolite in the cells and culture medium. The presence of 5-S-cysteinyldopa in cultured cells indicated the melanocytic origin of undifferentiated cells, and the increase of this metabolite was characteristic of differentiation.-J Natl Cancer Inst 55: 1327-1328, 1975. The melanocytes of human primary malignant mela-nomas dedifferentiate and later differentiate sponta-neously in cell cultures (1). The differentiation may be induced by addition of culture medium obtained from cell lines that have differentiated spontaneously (2)