MEIS1 and myeloid leukemia: All the MYC/HOXA9- and HOXA9/MEIS1-induced leukemias were positive to a myeloid marker Mac1 but negative to lymphoid marker B220 or CD3e (Figure 4—figure supplement 3A,B), indicating that both MYC/HOXA9- and HOXA9/MEIS1-combinations induced myeloid leukemia.