Effect of ATRA and CEP-701 on in vitro growth and differentiation of representative samples. Cells were cultured in RPMI/10% FCS for 3 to 5 days with either nothing further added (Control), 1 μM ATRA, 50 nM CEP-701, or 1 μM ATRA+50 nM CEP-701, and then counted, used in an MTS assay, and immunophenotyped to determine the relative percentage of annexin V^–/PI^–, CD11b⁺, and DCFDA⁺ cells. (A) NB4 cells. (B) Blasts from an FLT3 WT APL patient. (C) Blasts from an FLT3 ITD⁺ APL patient.