4.4. Annexin V/PI Staining and Flow Cytometry Analysis

Following drug treatment, AML cells were stained with Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) (Beckman Coulter, Brea, CA, USA) and then subjected to flow cytometry analysis, as previously described [24,25]. Apoptotic events are displayed as mean percentage of Annexin V+/PI− (early apoptotic) and Annexin V+/PI+ (late apoptotic and/or dead) cells ± the standard error from one representative experiment. Combination index values (CI) were calculated using CompuSyn software (ComboSyn Inc. Paramus, NJ, USA). CI < 1, CI = 1, CI > 1 indicate synergistic, additive, and antagonistic effects, respectively.