BCR and leukemia: Evi1-IRES-GFP allele models of CML in chronic phase (CML-CP), by retroviral overexpression of BCR–ABL and by crossing BCR–ABL transgenic mice, revealed that Evi1 is predominantly enriched in the stem cell fraction and associated with an enhanced proliferative as well as a leukemia-initiating capacity and that Evi1-high CML-CP cells exhibit resistance to TKIs.