Rottlerin inhibits NSC606985-induced caspase-3 activation, mitochondrial transmembrane potential loss, and apoptosis. (A-B) After preincubated with 1 μM rottlerin for 1 hour, NB4 and U937 cells were treated with 25 nM and 50 nM NSC606985 for 12 and 36 hours, respectively. PKCδ (A), the active (Δ) caspase-3, and PARP proteins (B) were determined by Western blots. ΔPKCδ indicates cleaved 41-kDa catalytic fragment of PKCδ proteins. (C) NB4 cells (top row) and U937 cells (bottom row) were treated as described for panels A and B. The mitochondrial ΔΨm was measured on flow cytometry. The numbers (percentage of Rh123^low cells) represent the mean ± SD of a triplicate experiment. (D) NB4 cells were treated as described for panels A and B, and the histograms of nuclear DNA distribution are presented. The number in each panel indicates the percentage of sub-G₁ (Ap) cells. Similar results were obtained in U937 cells (data not shown). All experiments were repeated 3 times with similar results.