KIT and acute promyelocytic leukemia: In contrast, the aforementioned GLI1/2 inhibitor, arsenic trioxide (ATO; 4 μM) [34, 35], which is an FDA-approved drug for the treatment of acute promyelocytic leukemia, reduced KIT mRNA by 60.2% in GIST-T1 cells and 38.0% in the GIST882 line (n = 3/cell line/group; Figure 5A).