Furthermore, fusion genes can be the targets of specific molecular therapy, the paradigmatic example being the use of all-trans retinoic acid (ATRA)/arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL) carrying the PML—RARA fusion which is key to APL leukemogenesis generated by t(15;17) [5]. The gene discussed is RARA; the disease is acute promyelocytic leukemia.