Acute leukemia in Mll^PTD/WT:Flt3^ITD/ITD mice. (A) Only AML and B-cell leukemias developed in Mll^PTD/WT:Flt3^ITD/ITD mice. Nineteen mice were analyzed. (B) Mll^PTD/WT:Flt3^ITD/ITD mice with leukemia exhibited significant splenomegaly at time of death. (C) WBC counts (median ± SEM) for leukemic Mll^PTD/WT:Flt3^ITD/ITD and age-matched control genotypes at the time of death. (D) Mll^PTD/WT:Flt3^ITD/ITD mice died of AML with a significantly shorter latency than Mll^PTD/WT:Flt3^ITD/WT mice. (E) Copy number ratio of Mll-WT:Mll-PTD was calculated for age-matched nonleukemic 15- to 25-week-old Mll^PTD/WT:Flt3^ITD/WT and leukemic Mll^PTD/WT:Flt3^ITD/ITD mice. Results are representative of 2 age-matched cohorts of mice.