Effect of C/EBPα in CML-BC cells. (Top panel) Induction of granulocyte differentiation by constitutive expression of C/EBPα in CML-BC cells. Bone marrow CD34⁺ cells (A) or peripheral blood blasts (B) from 2 CML-BC patients were retrovirally transduced with the MigRI empty vector or with wild-type or mutant C/EBPα. After sorting, GFP-positive cells were cultured in the presence of IL-3 or G-CSF and were assessed (May-Grünwald/Giemsa staining of cytospins) for morphologic differentiation. (Bottom panel) Western blot analysis shows C/EBPα expression in untreated and STI571-treated cells of the 2 patients with CML-BC. GRB-2 levels were measured as control of equal loading.