Activation of p53 by the MDM2-specific inhibitor nutlin3a induces DR5 expression and sensitizes cells to TRAIL-induced cell death. OCI-AML3 cells were treated with nutlin3a, TRAIL, or nutlin3a plus TRAIL for 24 hours. p53 and DR5 protein levels were measured by Western blotting and cell death by annexin V/PI staining and flow cytometric analysis. N3a indicates nutlin3a; TR, TRAIL. Error bars represent SE.