MECOM and breast cancer: When 1 × 103 LK cells were transplanted, leukemia-initiating cells were found to be enriched in the Evi1-high fraction with the frequency of 1/62 cells (1.6%), indicative of high leukemogenicity, whereas Evi1-low cells even in LK fraction had no potential for CML-BC development (Figure 5a, Supplementary Table S4).