All-trans retinoic acid combined with 5-Aza-2'-deoxycitidine induces C/EBPα expression and growth inhibition in MLL-AF9-positive leukemic cells.

The present study tested whether all-trans retinoic acid (ATRA) and 5-Aza-2'-deoxycitidine (5-Aza) affect AML cell differentiation and growth in vitro by acting on the CCAAT/enhancer binding protein α (C/EBPα) and c-Myc axis. After exposure to a combination of these agents, cell differentiation and growth arrest were significantly higher in human and murine MLL-AF9-expressing cells than in MLL-AF4/AF5q31-expressing cells, which were partly associated with increased expression of C/EBPα, C/EBPε, and PU.1, and decreased expression of c-Myc. These findings indicate that MLL-AF9-expressing cells are more sensitive to ATRA and 5-Aza, indicating that different MLL fusion proteins possess different epigenetic properties associated with retinoic acid pathway inactivation.