Like Zn2+, the arsenic ion coordinates to thiolate groups of cysteines, and ATO exerts its anti-APL effects by replacing Zn2+ with As3+ in the RING domain of promyelotic leukemia-retinoic acid receptor alpha (PML-RARα), a protein chimera with oncogenic function (Kaiming et al., 2018). This evidence concerns the gene RARA and acute promyelocytic leukemia.