Effect of CEBPB expression on 32D-BCR/ABL cell proliferation. (A) Methylcellulose colonies (as ratio on plated cells, on the y-axis) from GFP-sorted 32D-BCR/ABL cells transduced with MigRI GFP or MigRI GFP WT-C/EBPβ-HA and plated in the presence of increasing concentration of WEHI-conditioned medium as source of IL-3 (on the x-axis). Values are the mean plus SD of 3 different experiments. (B) Proliferation in liquid culture of untreated or 4-HT–treated (250 nM) cells carrying the MigRI GFP or the MigRI GFP ΔuORF C/EBPβ-ER^TAM retrovirus; cell number (× 10³) is on the y-axis, day of treatment is on the x-axis.