Triptolide-induced cell death is mediated, at least in part, through XIAP down-regulation. (A) OCI-AML3 cells at a density of 0.2 × 106/mL were treated with various concentrations of triptolide for 24 hours in the presence or absence of the caspase inhibitor IDN-1965 (20 μM) or the proteasome inhibitor MG132 (0.2 μM). The XIAP protein level was determined by Western blot. (B) OCI-AML3 cells at a density of 0.2 × 106/mL were treated for 24 hours with various concentrations of triptolide. RNA was isolated, and the XIAP RNA level was determined by TaqMan RT-PCR. (C) U937neo and U937XIAP cells at a density of 0.2 × 106/mL were treated for 24 hours with various concentrations of triptolide. Cell death was determined by annexin V staining with PI.
