NSC606985 induces mitochondrial transmembrane potential loss and caspase-3 activation in NB4 and U937 cells but not in K562 cells. (A-B) NB4 and U937 cells were treated with or without 25 nM and 50 nM NSC606985, respectively, for the indicated times, the mitochondrial ΔΨm (A) was measured on flow cytometry, and the active (Δ) caspase-3 and PARP proteins (B) were detected by Western blots. For the mitochondrial ΔΨm (A), abscissa and vertical axiles represent the fluorescent intensities of Rh123 and PI, respectively. The numbers below panels represent the mean ± SD of a triplicate experiment. [I] and [II] represent, respectively, percentage of Rh123^low/PI⁺ and Rh123^low/PI^- cells. (C) K562 cells were treated with or without NSC606985 at the indicated concentrations for 48 hours. The treatment with 100 μM etoposide for the shown hours was used as a positive control. PKCδ, Δcaspase-3, and PARP proteins were detected by Western blots. For Western blots, β-actin was used as an internal control. All experiments were repeated 3 times with similar results.