Phenotype of pre-B ALL on Sox4 deletion in vivo. BCR-ABL1–transformed mouse pre-B ALL from bone marrow of Sox4^fl/fl mice were transduced with 4-hydroxy tamoxifen (4-OHT)–inducible Cre (Cre) or an empty vector control (EV). Two × 10⁶ leukemia cells were injected into NOD/SCID recipient mice in each group. Phenotypic changes on deletion of Sox4 were studied by flow cytometry after isolation of leukemia cells from killed animals and staining for c-kit, Sca-1, CD19, B220, IgM, Igκ, and Igλ light chains, CD21, CD23, CD43, IL2RA (CD25), IL7R (CD127), and AA4.1 (CD93). BCR-ABL1 transduced ALL cells from donor bone marrow of Sox4^fl/fl mice express CD45.2 but not CD45.1. Donor-derived leukemia cells can be identified as CD45.2⁺ cells after injection into CD45.1⁺ NOD/SCID recipient mice.