Mouse models of CML were generated by transducing bone marrow stem and progenitor cells with retroviruses carrying BCR-ABL (chronic phase), or BCR-ABL and NUP98-HOXA9 (blast crisis phase) and transplanted into irradiated recipient mice. The development of CML was confirmed by flow cytometry and histopathology. For Msi2 knockdown experiments, lineage negative blast crisis CML cells were infected with Msi2 or control Luciferase shRNA retroviral constructs and leukemia incidence monitored. ChIP assays were performed using the myeloid leukemia cell line M1. DNA was crosslinked and immunoprecipitated with control or anti-HOXA9 antibodies and analyzed by PCR for regions of interest. CML patient samples were obtained from the Korean Leukemia Bank (Korea), the Hammersmith MRD Lab Sample Archive (United Kingdom), the Fred Hutchinson Cancer Research Center (United States) and the Singapore General Hospital (Singapore). Gene expression in human chronic and blast crisis CML was analyzed by PCR or by DNA microarrays.