Introduction of BCR-ABL and BMI1 in human cord blood CD34⁺ cells induces lymphoid leukemia upon transplantation in NOD/SCID mice. (A) Cord blood CD34⁺ cells were transduced with MiGR1 and MiNR1 empty vector controls, with MiGR1 BMI1 or MiNR1 BCR-ABL vectors, or cotransduced with both vectors (BMI1/BCR-ABL). Efficiencies after 3 transduction rounds are shown. (B) Expression of BMI1, BCR-ABL, and phosphorylated STAT5 was analyzed by Western blotting of transduced CB CD34⁺ cells. A vertical line has been inserted to indicate a repositioned gel lane. (C) Transduced CB CD34⁺ cells were transplanted into sublethally irradiated NOD/SCID mice, and Kaplan-Meier survival curves are shown. BM of 2 mice was used for secondary transplantation into sublethally irradiated NOD/SCID mice in duplicate, and Kaplan-Meier survival curves of these mice are shown as well. (D) FACS analysis of BM of engrafted NOD/SCID mice at week 16. (E) Transduced CB CD34⁺ cells were transplanted into sublethally irradiated NOD/SCID mice, and the percentage of double-positive cells was evaluated directly after transduction and at later time points in the PB of the recipient mice. (F) FACS analysis of the spleen and the liver of the diseased mice showed infiltration of the organs with primitive CD34⁺ human cells. (G) May- Grünwald Giemsa staining of cytospins from BM and spleen of diseased mice.