Cytoplasmic p27 promotes BCR-ABL1–induced leukemia. (A) BM cells from p27^−/− and p27^CK− mice were transduced with BCR-ABL1 retrovirus, sorted by FACS for GFP⁺/Lin⁻ cells and plated in methylcellulose in absence of cytokines. Myeloid colony formation of BCR-ABL1–transduced cells was assessed after 8 days. (B) Kaplan-Meier survival analysis of p27^+/+ mice transplanted with BCR-ABL1–transduced BM cells from p27^−/− and p27^CK− mice. (C) WBC and PLT counts and (D) spleen and liver weights of leukemic mice were compared according to genotype. (E) Lineage distributions of GFP⁺ cells in the BM and spleen of leukemic mice: granulocytes (Gr1⁺CD11b⁺), B cells (CD19⁺), T cells (CD3⁺), and LKS cells (Lin⁻c-Kit⁺Sca1⁺). Error bars represent standard deviation. (F) Representative histological sections of BM, liver, lung, and spleen from mice transplanted with BCR-ABL1–transduced BM cells from p27^−/− and p27^CK− mice. Scale bars represent 100 μm. In above experiments, **P < .010.