Lincomycin abrogates dexamethasone-enhanced melanogenesis in B16 melanoma cells

The effects of lincosamide, and interference between the effects of glucocorticoid and lincosamide, on melanogenesis were determined in B16 melanoma cells. Cells were treated for 4 days with lincomycin (LM) and/or dexamethasone (DX) at equimolar concentrations ranging from 10(-9) M to 10(-5) M, or at various concentrations of DX with 10(-6) M LM. Effects on proliferation, tyrosinase activity, melanin biosynthesis, and levels of mRNA for tyrosinase, tyrosinase-related protein 1 (TRP1), and tyrosinase-related protein 2 (TRP2) were examined. Treatment with LM or LM + DX stimulated proliferation of melanoma cells with minimal cytotoxicity, while DX did not influence cell proliferation either alone or in combination with LM. Treatment with LM alone increased tyrosinase activity slightly and reduced melanin content in a dose-dependent manner. However, LM counteracted the pronounced increase in tyrosinase elicited by DX and also abrogated the dose-dependent increase in melanin content elicited by DX, Treatment with LM alone did not affect mRNA levels for tyrosinase, TRP1, or TRP2. Furthermore, LM abrogated the DX-induced up-regulation of mRNAs for tyrosinase and the down-regulation of TRP1 mRNA. These results suggest that LM inhibits melanogenesis post-transcriptionally and abrogates glucocorticoid-induced melanogenesis at the transcriptional level in B16 melanoma cells.