Arsenic trioxide (ATO) (IC50: 2.7 μM), approved by the FDA for acute promyelocytic leukemia (APL), targeted the Gli1 transcription factor and exhibited significant cytotoxicity in mice models of MB and Ewing sarcoma, supporting further pharmacological evaluation in Gli1-dependent malignancies (139). This evidence concerns the gene GLI1 and acute promyelocytic leukemia.