Rapid expansion and reduced apoptosis of Mll^PTD/WT LSK/SLAM⁺ cells under stresses. (A) A single dose (150 mg/kg) of 5-FU was administered intraperitoneally into Mll^PTD/WT or WT (6-8 mice per group). BM cells were collected at the mentioned time point. Absolute number of LSK (A) and LSK/SLAM⁺ (B) in WT and Mll^PTD/WT expressed as mean ± SD per million BM cells. *P < .05. (C) Fold change of LSK or LSK/SLAM⁺ between day 14 and day 0 in WT and Mll^PTD/WT mice. (D) Apoptosis was checked by annexin V staining. Data shown are the mean percentage ± SD of annexin V⁺/7 AAD⁻ and annexin V⁺/7 AAD⁺ (n = 4). *P < .05. (E) Cell-cycle analysis was performed with BrdU flow kit. Percentage of cycling cells (G₀/G₁ and S/G₂/M) are shown for LSK fraction at 10 days after 5-FU administration (2 experiments, n = 4). **P < .01. (F) Expression of Bcl-2 family protein in LSK fractions. BM cells were harvested 24 hours after 5-FU (150 mg/kg) intraperitoneal injection (F) or collected from primary 1:1 ratio competitive BMT recipients 2 months after transplantation (G). LSK cells were selected by using autoMACS. Western blots were done using the indicated antibodies (anti-Mcl1, anti-Bcl2, anti–Bcl-XL, anti-Bax, and antitubulin).