<;P>;PROBLEM TO BE SOLVED: To provide a drug for preventing and treating leukemia which can promote differentiation of leukocyte, can be administered for a long time, and can be effective also for a patient showing noticeable functional disorder of retinoic acid receptor. <;P>;SOLUTION: There is provided a fused protein containing a retinoic acid receptor &alpha; and a nuclear localization signal and/or cell membrane-permeable motif. <;P>;COPYRIGHT: (C)2011,JPO&INPIT