CEBPB expression induces granulocytic differentiation of 32D-BCR/ABL cells. (A) May-Grünwald-Giemsa staining of cytospin from 32D-BCR/ABL transduced with the MigRI GFP ΔuORF C/EBPβ-ER^TAM retrovirus, induced or not with 4-HT and untreated or treated with G-CSF. (B) Gr-1 expression in MigRI GFP C/EBPβ-ER^TAM-transduced 32D-BCR/ABL cells. The percentage of Gr-1⁺ cells (assessed by immunostaining with a PE-conjugated anti–Gr-1 antibody) is expressed on the y-axis, whereas x values indicate length of treatment (in days). Values shown are the mean plus SD of 3 different experiments. (C) Western blot analysis of G-CSFR expression in transduced 32D-BCR/ABL cells. Cells were treated with 4-HT alone (lanes 1-4) or in combination with G-CSF (lanes 5-12). Equal loading was monitored by anti-GRB2 Western blotting. (D) MPO and CD33 antigen mRNA levels on total RNA from G-CSF–treated (3 days) 32Dcl3 cells as positive control (lane 1), MigRI GFP ΔuORF C/EBPβ-ER^TAM (lanes 2-5), or MigRI GFP-transduced (lanes 6-9) 32D-BCR/ABL cells before (lanes 2 and 6) and after (lanes 3-5 and 7-9) 4-HT treatment.