Knock down of PIAS1 in NB4 cells, an APL cell line that recapitulates the effects elicited by ATO in primary APL cells (Roussel and Lanotte, 2001), significantly reduces the ability of ATO to degrade PML-RARA causing a significant resistance to ATO-induced apoptosis (Rabellino et al., 2012). This evidence concerns the gene PIAS1 and acute promyelocytic leukemia.