RARA and acute promyelocytic leukemia: ATRA and ATO targeted PML-RARA and induced its degradation via two totally different routes, so combination of ATRA and ATO cooperate in APL treatment, in which ATRA induced APL differentiation, and low-dose ATO induced differentiation while high-dose ATO induced apoptosis, and achieved excellent clinical responses in APL patients [15] (Fig. 1).