Effects of oridonin on AE fusion protein and the possible mechanisms. (A) In Kasumi-1 cells, oridonin causes a degradation of AE with generation of an approximately 70-kDa catabolic fragment. In this expression, Western blot assay was done using an anti-ETO antibody whose epitope maps at the C-terminal of ETO. Effects of oridonin on casp-3, PARP, casp-9, and cytoplasmic cyt C are also shown. In U937-A/E cells, oridonin treatment also causes degradation of AE (lower panel, using the anti-ETO antibody). (B) Effects of pan-caspase inhibitor on oridonin-induced apoptosis. (C) The presence of PA, which induces the expression of AE, enhances apoptotic effect of oridonin on U937-A/E cells, as revealed by reduction of viable cells upon oridonin treatment. (D) Pretreatment with pan-caspase inhibitor z-VAD.fmk (left panel) and casp-3 inhibitor z-DQMD-fmk (right panel) prevents AE from proteolysis. (E) Pretreatment with 3 proteasome inhibitors, PSI, Lact, and MG-132, cannot prevent oridonin-induced degradation of AE. Error bars represent SD of experiments.