Caspase-3 inhibitor, Z-DEVD-fmk, partly inhibits NSC606985-induced proteolysis of PKCδ proteins and apoptosis in NB4 cells. NB4 cells were preincubated with 40 μM Z-DEVD-fmk for 1 hour and then treated with or without 25 nM NSC606985 for 12 hours. The active caspase-3 (A) and PKCδ proteins (B) were detected by Western blots. ΔPKCδ indicates cleaved 41-kDa fragment of PKCδ proteins. The annexin V (C) and mitochondrial ΔΨm (D) were measured on flow cytometry. The numbers in panels C and D indicate the percentages of annexin-V⁺/PI^- cells and low ΔΨm cells, respectively. The numbers are the mean ± SD of a triplicate experiment. ^**P < .01 and ^#P > .05 by the Student t test, compared with NSC606985 treatment alone.