MLN4924 induces stable disease regression in an AML xenograft model. (A) Administration of MLN4924 to mice bearing HL-60 xenografts leads to a dose-dependent reduction in disease burden. Mice received vehicle control, 10, 30, 60, or 90 mg/kg MLN4924 twice a day for 21 days. Tumor volume was measured by calipers. n = 10 per group; bars represent the mean ± SD. (B) Effect of MLN4924 treatment on NEDDylation of cullins in vivo. Mice were administered a single dose of MLN4924, and the levels of NEDDylated cullins were quantified at the indicated time points (n = 3). (C) Dose-dependent stabilization of phospho-IκBα after treatment with MLN4924. Mice were given a single dose of MLN4924, and the levels of phospho-IκBα were quantified at the indicated time points after drug administration. (D) Schematic representation of the proposed mechanism of MLN4924-induced apoptosis in AML cells. MLN4924 inhibits the activity of NAE, leading to the abrogation of cullin NEDDylation, the stabilization of NEDD8-regulated substrates, increased ROS production, and DNA damage, which culminates in apoptosis.