Figure 3. Effects of the bromoalkyl phenytoin derivatives, PH2, PH3, and PH4, on activation of caspase-8, -9 and -3/7 in HL-60 and U937 cells. Representative histograms of HL-60 cells (A, B, C), obtained 24 h after application of DMSO only, and PH3; X axis: (A) fluorescence of Red-IETD-FMK, a caspase-8 inhibitor IETD-FMK conjugated to sulfo-rhodamine; (B) - fluorescence of Red-LEHD-FMK, a caspase-9 inhibitor LEHD-FMK conjugated to sulfo-rhodamine, (C) – fluorescence of CellEvent™ Caspase-3/7 Green Detection Reagent, a fluorogenic substrate for activated caspases-3/7. M1 – HL-60 cells without active caspase-8 (A), -9 (B) and -3/7 (C); M2 - cells with active caspase-8 (A), -9 (B) and -3/7 (C); The frequency of HL-60 (D, E, F) and U937 (G, H, I) cells with active caspase-8, -9 and -3/7 observed 24 h after after their exposure to the action of the tested phenytoin analogs. Values significantly different at p<0.05 according to the Tukey's multiple range test: *, **, *** between the groups of leukemia cells treated with PH2, PH3, and PH4, # compared to controls.