Characterization of KP1019 and KP1339 apoptosis. a Loss of mitochondrial membrane potential after 24-h treatment was determined by 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining. Increase of the green fluorescent apoptotic populations of KB-3-1 cells at the drug concentrations indicated (cells in the lower right field) are indicated (30,000 events were analyzed in total per group). b Effects of 30-min pretreatment with the radical scavenger N-acetylcysteine (NAC) on the anticancer activity of KP1019, KP1339, and H2O2 (positive control) were analyzed after 72-h drug exposure by an EZ4U kit