Effect of the sequence on cell viability and apoptosis. MOLT4 cells were treated with vorinostat at 0.3 μM and idarubicin at 0.5 nM concomitantly or IDA was added 4 hours before vorinostat (Vor) (IDA, A; vorinostat, B) or after vorinostat (IDA, B; vorinostat, A) daily for 3 days. (A) Numbers on the y-axis represent the number of viable cells. (B) Numbers on the y-axis represent the percentage of apoptotic cells. Error bars indicate standard deviation.