MITF and melanoma: MITF expression was significantly inhibited by 0.1 μM maytansine (60), toyocamycin (108) and colchicine (1), whereas its expression was significantly higher in melanoma cells treated with 0.1 μM streptonigrin (32) and 0.4 μM geldanamycin analog (72) for 24 h (Fig. 10B).