The international journal of biochemistry & cell biology
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Int. J. Biochem. Cell Biol. · Oct 2001
Transforming growth factor beta1 mediates hypopigmentation of B16 mouse melanoma cells by inhibition of melanin formation and melanosome maturation.
Transforming growth factor-beta1 (TGFbeta1) downregulates tyrosinase in B16 melanoma cells by decreasing gene expression and the intracellular half-life of the enzyme, but does not block tyrosinase stimulation by alpha-melanocyte stimulating hormone (alphaMSH). In the presence of both agents, the enzymatic activity is intermediate between the one of cells treated with either agent alone. Here we show that TGFbeta1 equally inhibits the melanogenic activities of melan-a melanocytes and B16 melanoma cells, thus validating the B16 model. ⋯ TGFbeta1 increased the percentage of stage III melanosomes. This trend was even more marked in cells treated with alphaMSH and TGFbeta1. The accumulation of incompletely melanized melanosomes is consistent with the inhibition of melanin formation activity by TGFbeta1 and with its hypopigmenting effect.