Triptolide activates p53 signaling and induces the expression of the p53 downstream target DR5. OCI-AML3 and U937 cells were treated with triptolide for 48 hours. DR5 (A) and p53 (B) levels were determined by Western blotting. OCI-AML3vec and OCI-AML3p53shRNA cells were treated with triptolide for 48 hours. p53 and DR5 protein levels (C) were measured by Western blotting.