RARA and acute promyelocytic leukemia: All-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) were empirically identified to provoke a profound therapeutic response against APL, before the molecular pathogenesis of the disease was established (Huang et al., 1988; Borrow et al., 1990; de Thé et al., 1990; Sun et al., 1992) and unravelling intricacies of their mode of action toward PML-RARα is ongoing.