GLUCOCORTICOID STIMULATES MELANOGENESIS AND TYROSINASE GENE-EXPRESSION IN B16 MELANOMA-CELLS

Effects of dexamethasone on melanogenesis and tyrosinase mRNA levels were determined in B16/F10 melanoma cells. Melanin content of B16 cells increased in a dose-dependent manner by the addition of dexamethasone to the culture medium. After 72 hr exposure, dexamethasone (10(-6) M) produced a 2.4-fold increase in melanin content. Northern blot analysis revealed that tyrosinase mRNA level also increased by the addition of dexamethasone to the culture medium. After 24 hr exposure, dexamethasone (10(-6) M) caused a 1.8-fold increase in tyrosinase mRNA levels. A tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA) decreased tyrosinase mRNA level at 30 nM concentration. Dexamethasone antagonized this TPA-mediated decrease in tyrosinase mRNA. It is suggested that glucocorticoids are involved in the regulation of tyrosinase activity at the transcriptional level.