Bmi1 collaborates with inducible BCR-ABL to induce lymphoid BC in vivo. (A) Experimental setup. To model CML-BC–initiating cells, LSK cells were isolated from Ntg or Scl/p210 mice presenting with myeloproliferative disorder (MPD), transduced with Bmi1 or empty lentiviral vectors expressing EGFP, and serially transplanted into lethally irradiated primary, secondary, and tertiary recipient mice. (B) Representative flow cytometry (FACS) contour diagram showing the frequency of EGFP⁺FSC^hiB220^loCD19⁺CD43⁺IgM⁻ B-lymphoid blasts present in the peripheral blood, BM, spleen, and lymph nodes of Scl/p210;Bmi1 mice. (C) Cumulative survival using the Kaplan-Meier log-rank P test performed in Ntg;MOCK-, Ntg;Bmi1-, Scl/p210;MOCK-, and Scl/p210;Bmi1-transplanted primary, secondary, and tertiary recipient mice (P < .05, n = 6-12 mice per group; n = 2 independent experiments). (D) Histological evidence of leukemic cell infiltration into the BM (magnification 100×) and spleen (Magnification 100×) in Scl/p210;Bmi1 (DOX OFF) mice compared with Scl/p210;Bmi1 (DOX ON) mice. Inset pictures show tissue infiltration at higher magnification (400×) or cytospin preparation of immature lymphoblasts (magnification 1000×). (E) Representative FACS contour diagram showing the frequency of HSCs and MPPs gated on EGFP⁺ BM cells from Ntg;MOCK, Ntg;Bmi1, Scl/p210;MOCK, and Scl/p210;Bmi1 mice. (F) LAM-PCR amplifying lentiviral vector insertion sites in the BM and spleen of Scl/p210;Bmi1-transplanted primary, secondary, and tertiary recipient mice, demonstrating a predominantly monoclonal integration pattern. Negative control indicates mouse genomic DNA control. *Internal standard. Microphotographs were obtained with an Olympus CKX41, objectives ×10, ×40, and ×100. The images were acquired with a Moticam 2500 color camera (5.0 MPixal, USB2.0), Motich China Group Co Ltd, and processed using Motic Images Plus 2.0 software.