By using a murine leukemic model carrying both promyelocytic leukemia zinc finger/retinoic acid receptor-? (PLZF/RAR?) and RAR?/PLZF fusion genes, we discovered that 8-chlorophenylthio adenosine-3', 5'-cyclic monophosphate (8-CPT-cAMP) enhances cellular differentiation and improves gene trans-activation by ATRA in leukemic blasts.     ///    "Mechanistically, in combination with ATRA, 8-CPT-cAMP activates PKA, causing phosphorylation of PLZF/RAR? at Ser765 and resulting in increased dissociation of the silencing mediator for retinoic acid and thyroid hormone receptors/nuclear receptor corepressor from PLZF/RAR?. "