Some of the FLT3^ITD/ITD mice develop leukemia, which is transplantable. (A) Leukemia in an FLT3^ITD/ITD mouse. (i-ii) Liver with significant leukemic infiltration. (iii) Olfactory bulbs of the brain surrounded by infiltrating tumor cells in the meninges (arrowhead). (iv) Lymph node with architecture effaced by sheets of blasts and numerous aberrant mitotic figures (arrowheads). (v-vi) Vertebral BM replaced by sheets of leukemic blasts. (vii-ix) Wright-Giemsa stain of BM cytopsins demonstrates increased fraction of blasts in a leukemic FLT3^ITD/ITD mouse (viii) and its recipients after BM transplantation (ix) compared with a WT control (vii). Scale bars are as follows: iii, 200 μm; i,v, 100 μm; and ii,iv,vi, 10 μm. Image acquisition for hematoxylin and eosin stain is the same as described in Figure 2. Images for Wright-Giemsa stain were acquired using a Nikon Eclipse E600 microscope system with a Nikon 100×/0.90 NA oil objective (original magnification ×1000) and were photographed with a Nikon DMX 1200 digital camera with ACT-1 2.0 software (Nikon). (B) Flow cytometric analysis demonstrates increased immature fraction in representative leukemic FLT3^ITD/ITD mice. (C) B220⁺c-KIT⁺, but not B220⁺c-KIT⁻ cells, from FLT3^ITD/ITD leukemic mice are myelperoxidase positive. Mac-1⁺/Gr-1⁺ cells from a WT mouse were used as positive control. (D) Kaplan-Meier plot of the survival of recipients after the first (1°-Tp) and secondary (2°-Tp) transplantation of leukemic FLT3^ITD/ITD BM cells. (E) Flow cytometric analysis shows the accumulation of immature cells in BM from a representative recipient mouse transplanted with leukemic FLT3^ITD/ITD cells. Numbers indicate percentage of cells in whole BM.