Regulation of melanin synthesis by the TGF-β family in B16 melanoma cells

Effects of representative members of the transforming growth factor-beta (TGF-beta) family, TGF-beta 1, activin A and BMP-2, on melanin content and expression of pigment-producing enzymes were examined in B16 melanoma cells. Treatment with TGF-beta 1 or activin A but not with BMP-2 significantly decreased melanin content and expression of Tyrosinase and Tyrp-1, suggesting an inhibitory effect of TGF-beta 1 and activin A on melanin synthesis. TGF-beta 1 completely inhibited melanin synthesis induced by alpha-melanin stimulating hormone (alpha-MSH), whereas activin A only slightly did. As compared with parental B16 cells, the inhibitory effects of TGF-beta 1 and activin A on melanin content were relative smaller in B16 F10 cells, a subline of B16 cells that contain more pigment. The present study indicates that in addition to TGF-beta, activin negatively regulates melanogenesis in the absence of alpha-MSH, but that the activity in the presence of alpha-MSH was slightly different between TGF-beta and activin.