A single CX-5461 administration reduces the tumor burden in M/E leukemic mice. M/E p53WT AML was transplanted into recipient C57Bl/6 mice (A-E). (A) Mac-1⁺/GFP⁺ double-positive tumor cells within the BM (1.45 × 10⁷ ± 0.05 cells for vehicle vs 0.18 × 10⁷ ± 0.04 cells for CX-5461; ****P < .0001; n = 5) and (B) spleen weights were determined after 24 hours of CX-5461 treatment (40 mg/kg) (****P < .0001; n = 5). (C) Analysis of apoptotic cell death via TUNEL staining of femoral BM sections from mice treated for 12 hours and stained with hematoxylin and eosin (H&E). Sections shown are representative of n = 3. Scale bar represents 50 μm (D) Cell death was determined by examining the SubG1 DNA content in the BM 10 hours post-drug administration (12.2% ± 2.2 for CX-5461 vs 1.9% ± 0.3 for vehicle; *P = .0102; n = 5). (E) Total p53 protein induction in response to CX-5461 single-dose treatment in the BM of M/E leukemic mice (n = 5 per group). (F) Quantitation of cell-cycle distribution in the BM cells by BrdU incorporation 24 hours post–CX-5461 treatment (***P = .0005; n = 5). Graph represents mean ± SEM. M/E p53null AML was injected into recipient C57Bl/6 mice (G-J). (G) The total number of Mac1⁺/GFP⁺ double-positive tumor cells within the BM (3.2 × 10⁷ ± 0.2 cells for vehicle vs 3.1 × 10⁷ ± 0.3 cells for CX-5461 at 24 hours, and 3.9 × 10⁷ ± 0.5 cells for vehicle and 0.5 × 10⁷ ± 0.2 cells for CX-5461 at 72 hours; **P = .0053), and (H) spleen weights (*P = .0134; n = 4 to 6) were determined after CX-5461 administration (35 mg/kg). Graphs represent mean ± SEM. Cell death (I) was analyzed by determining SubG1 DNA content in the BM 10 hours post–CX-5461 treatment (n = 6). Quantitation of cell-cycle distribution (J) in the BM cell was analyzed by BrdU incorporation 24 hours post–CX-5461 administration (***P = .0007). Graphs represent mean ± SEM (n = 5). In all cases, an unpaired 2-tailed Student t test was used. n.s., not significant.