Proliferation and morphology of melanoma cells and benign human melanocytes under varying culture conditions.

In order to enable a direct comparison of gene expression in human melanoma cells and in normal human melanocytes, culture conditions were investigated under which both cell populations can be grown in vitro. Five of 13 melanoma cell lines tested could be cultured to confluence in a melanocyte medium containing fetal calf serum, 12-O-tetradecanoylphorbol-13-acetate and stimulators of cyclic adenosine monophosphate, whereas none could be grown to confluence in a serum-free hormone-supplemented melanocyte medium containing basic fibroblast growth factor and other mitogens. In both melanocyte media the melanoma cells showed signs of increased morphological differentiation with dendrite formation. Normal human melanocytes could be grown in melanoma cell medium for a few days, after which the cultured cells showed a less differentiated phenotype. Since morphological changes may reflect variations in gene expression, we suggest that comparative studies on gene expression of benign and malignant melanocytes should also include thorough investigation under identical culture conditions.