Development and characterization of GRKO leukemia. (A-B) Leukemia development in GRKO B6 mice receiving Notch1-overexpressing Lin⁻Sca1⁺ GRKO BMCs. Shown are representative spleen and liver tissues from naive and leukemia B6 mice (A) and histology (H&E) of spleen, liver and bone marrow from a representative leukemia mouse (B). (C) B6 mice were injected with leukemia cells (ie, splenocytes from mice receiving Lin⁻Sca1⁺ GRKO BMCs), killed when moribund, and GFP⁺ leukemia cells in the spleen were assessed by flow cytometry. Left panel indicates that the spleen consists of predominantly GFP⁺ leukemia cells; right panel shows the expression of various cell surface markers on gated GFP⁺ leukemia cells. (D) Naive B6 mice (n = 4) were injected intravenously with 5 × 10⁶ cryopreserved GRKO leukemia cells and killed 2-3 weeks later for assessing leukemia development. Shown are percentages (mean ± SD) of GFP⁺ leukemia cells (left) and of CD25⁺ leukemia cells (right) in the indicated tissues.