A Combination of Retinoic Acid and Proteasome Inhibitors for the Treatment of Leukemias Is Potentially Dangerous

To the Editor: Retinoic acid (RA) is used in the treatment of leukemias; however, the phenomenon of RA resistance is often the cause of relapse in some patients. In a recent report, Fanelli et al[1][1] showed, using an acute promyelocytic leukemia–derived cell line NB4, that the treatment of RA-