Effect of ITD-Flt3 and Survivin on expansion/differentiation of Lin^Neg cells. Absolute number and proportion of Lin^Pos cells in cultures of Lin^Neg cells derived from Survivin^flox/flox and Cre-ER Survivin^flox/flox cells transduced with wild-type (WT) or ITD-Flt3 (N51) are shown. After retrovirus transduction, Lin^Pos cells were depleted by magnetic-activated cell sorting (MACS) column (Miltenyi Biotec) and Lin^Neg cells were cultured with 50 ng/mL rmSCF and 10 ng/mL rmGM-CSF for 14 days in the presence of 1 μM 4OH-tamoxifen to induce Survivin deletion. The number and the proportion of GFP⁺ Lin^Pos cells were determined by cell enumeration and flow cytometry. The inset shows fold change in Lin^Pos cells in cultures of lineage-depleted control marrow cells expressing ITD-Flt3 versus wild-type Flt3 (▫) and fold change in Lin^Pos cells in cultures of lineage-depleted Cre-ER Survivin^flox/flox cells expressing ITD-Flt3 after Survivin deletion versus control Survivin^flox/flox cells expressing ITD-Flt3 (). Data are mean ± SEM of 2 experiments. *P < .05 compared with wild type Flt3; †P < .05 compared with Survivin^flox/flox.