Effects of idarubicin, vorinostat, or VPA in HL60 and MOLT4 cell viability. Cell viability was studied using trypan blue assays. Numbers on the y-axis represent the total number of viable cells. (A-B) HL60 and MOLT4 cells were treated with increasing concentrations of idarubicin (ida; 0.5-20 nM) daily for 3 days. Subsequently, both cell lines were treated with increasing concentrations of (C-D) vorinostat (Vor; 0.3-3 μM) or (E-F) VPA (0.25-3 mM) both daily for 3 days. Bars indicate the standard deviation.