Clinically, treatment of APL patients and other cancer cells with arsenic trioxide (ATO) and/or all-trans-retinoic acid (ATRA) was shown to cause proteasomal degradation of PML–RARα and cPML to prevent their nucleocytoplasmic shuttling and reverse their tumorigenic effects [57–59]. This evidence concerns the gene RARA and acute promyelocytic leukemia.