SPC induces MITF downregulation in Mel-Ab cells. (A) After serum starvation for 24 h, Mel-Ab cells were treated with 0-10 μM SPC for 3 h. Whole cell lysates were analyzed by Western blotting with antibodies against MITF-M and actin (loading control). (B) B16/F10 cells were transfected with 2 μg of luciferase reporter plasmid plus 1 μg of the pSV-β-galactosidase control vector. After incubating with 10 μM SPC for 24 h, luciferase activity was assessed and normalized with respect to β-galactosidase activity. Results are expressed as percentages of the untreated control. Each determination was made in triplicate; the data shown represent means ± SD. ** P < 0.01 compared to the α-MSH-treated cells.