Saikosaponin b(2) induces differentiation without growth inhibition in cultured B16 melanoma cells

Treatment with 5 mu M of saikosaponin (SS) b(2) for 30 days was found to in duce differentiation of B16 melanoma cells, with potentiation of expression s of melanogenesis and tyrosinase. To explore the mechanism of this effect, we observed the cell growth, cell cycle and morphology, and found that SSb 2 did not affect any of these parameters. That is, SSb2 induced the differe ntiation of B16 melanoma cells without growth inhibition or cytotoxicity un der conditions of low dose and long-term treatment. Phorbol ester, a protei n kinase C (PKC) activator, markedly inhibited the expressions of melanogen esis and tyrosinase in both the control B16 melanoma cells and the long-ter m treated B16 melanoma cells. Down-regulation of the PKC activity may be in volved in the effects of SSb2.