Next, we performed fractionation by flow cytometry, isolating putative leukemia initiating cell populations (LKS + , GMP) from the BM and spleen (Kit + ) of leukemic mice and transplanted these cells along with 2 × 105 wildtype BM cells (“helper BM”) into lethally (1100 cGy) irradiated mice (Fig. 2B). Here, KIT is linked to leukemia.