C/EBPβ excision does not inhibit the development of Evi1-induced leukemia in vivo. (A) Schema of the BMT model using Mx-Cre;C/EBPβ^fl/fl mice and C/EBPβ^fl/fl mice. (B) Genotyping PCR of BM cells from Mx-Cre;C/EBPβ^fl/fl mice and C/EBPβ^fl/fl mice 3 days after retrovirus infection. Excision of C/EBPβ occurred without pI-pC injection. (C) Time courses of the percentage of donor chimerism in PB. Mx-Cre;C/EBPβ^fl/fl (n = 19) and C/EBPβ^fl/fl (n = 10). (D) The genomic DNA of PB derived from the recipient mice were analyzed for recombination events at 5 months (top panel) and 7 months (bottom panel) after the BMT. The intensity of the shortest band for the deleted allele was higher at 7 months than at 5 months. (E) The GFP-positive BM cells derived from the leukemic mice were sorted and analyzed for recombination events by genotyping PCR. (F) Kaplan-Meier analysis for the mice that had received the Evi1-transduced BM cells of the Mx-Cre;C/EBPβ^fl/fl mice (n = 19), C/EBPβ^fl/fl mice (n = 10), and wild-type mice (n = 21). (G) Schema of the second BMT model. LAP*, LAP, or LIP were transduced into the Evi1-induced leukemic cells derived from C/EBPβ^−/− cells by using retroviral infection. The double-positive cells (Evi1-GFP/C/EBPβ–Kusabira Orange) were sorted and then were transplanted into the recipient mice. (H) Left panels show flow cytometric data of C/EBPβ–deleted Evi1 (GFP) leukemia cells with forced expression of each C/EBPβ isoform (Kusabira Orange) or empty vector (Kusabira Orange). The double-positive cells were sorted and transplanted to recipient mice. Right panels show engraftment of the double-positive (Evi1+, LIP+, or mock+) transplanted cells but no engraftment of the LAP*- or LAP-expressing cells at 6 weeks after transplantation. (I) Survival curves of the second BMT recipient mice. LAP* (n = 3), LAP (n = 5), LIP (n = 5), and mock (n = 3). The triangles and circles on the curves are inserted to distinguish each curve but do not show the number of samples.