CDK6 advances p185^BCR-ABL–induced leukemia. (A) Top panel shows the percentages of B cells of fraction A-C in the BM (left panel) and fraction D-F in the spleens (right panel) of Cdk6^−/− mice compared with Cdk6^+/+ mice as analyzed by FACS (n = 3; fraction A: 2-tailed t test, P = .0379). In the bottom panel, dot blots indicate the percentages of gated CD43⁺/B220⁺ (first panel) and CD43⁺/B220⁺/CD19⁻/BP-1⁻ for fraction A, CD43⁺/B220⁺/CD19⁺/BP-1⁻ for fraction B, and CD43⁺/B220⁺/CD19⁺/BP-1⁺ for fraction C (second panel) in the BM and gated CD43⁻/B220⁺ (third panel) and CD43⁻/B220⁺/IgD⁻/IgM⁻ for fraction D, CD43⁻/B220⁺/IgD⁺/IgM⁻ for fraction E, and CD43⁻/B220⁺/IgD⁻/IgM⁻ for fraction F (fourth panel) in the spleens of Cdk6^−/− and Cdk6^+/+ mice. (B) [³H]-thymidine incorporation into fetal liver–derived Cdk6^+/+ and Cdk6^−/−p185^BCR-ABL–transformed cell lines was measured (n = 6; 2-tailed t test, P < .0001). (C) Cells (1 × 10⁵) of p185^BCR-ABL–transformed Cdk6^+/+ (n = 3) and Cdk6^−/− (n = 3) mice were plated and total cell numbers were determined after 48, 96, and 144 hours. (D) Injection of Cdk6^+/+ (n = 7), Cdk6^+/− (n = 23), and Cdk6^−/− (n = 16) newborn mice with a replication-deficient Ab-MuLV–encoding retrovirus resulted in B-lymphoid leukemia/lymphoma (mean survival 63 vs 62 vs 120 days in Cdk6^+/+, Cdk6^+/−, and Cdk6^−/− mice, respectively; P < .0001 for Cdk6^+/+ vs Cdk6^−/−). (E) The infiltration rates of CD19⁺/CD43⁺ cells in the spleens of diseased mice were analyzed by FACS (n = 6; 2-tailed t test, P = .103).