The establishment and the characteristics of five cell lines derived from either hard palate primary or metastatic malignant melanoma have already been reported. In this paper, the relationship between melanization and tyrosinase activity of these five cell lines is reported.
The MMN9 and MMN13 cells remained melanotic and continued to produce melanin granules. The MMN12 cells became amelanotic and developed multipolar neuroblast-like processes. The PMP cells were amelanotic but contained many melanin accumulations. It was suspected that the PMP cells contained pheomelanin. The MAA cells were amelanotic and tyrosinase activity was zero after 6 days of culture. Biochemical and morphological characteristics were strikingly changed by addition of 1% fetal bovine serum (FBS) to the culture medium. This phenomenon appeared to demonstrate the so called “contrary of growth and differentiation”. With GIT and 1% FBS culture medium, the melanin content tended to increase. It was considered that FBS contained some control factors that induce melanin production in culture.
