Impaired recovery of Cdk6^−/− mice after 5-FU treatment. (A) Cdk6^+/+ and Cdk6^−/− mice were repeatedly treated with 150 mg/kg 5-FU every 10 days (Figure 3B) or analyzed 8 days after a single dose of 5-FU (Figure 3C-E). (B) Four of 5 Cdk6^+/+ animals survived for 150 days, whereas all Cdk6^−/− animals died within 25 days (n = 5 per genotype; ***P < .001). (C) Eight days after 5-FU treatment, BM of Cdk6^+/+ and Cdk6^−/− mice was analyzed via FACS for the presence of LSKs and LSKCD150⁺CD48⁻ (A) cells. Gating strategy is shown in 1 representative FACS blot per genotype (left). Summary of statistical analyses of individual LSK subpopulations (right; n = 4 per genotype, *P < .05). (D) Cell-cycle distributions of fraction A cells were determined by a combined DAPI and Ki-67 staining. One representative FACS blot per genotype is shown (left). Summary of statistical analyses (right; n = 4 per genotype, **P < .01, ***P < .001). (E) Cdk6^+/+ and Cdk6^−/− mice were analyzed for lineage recovery (Gr1⁺Mac1⁺, CD19⁺, and Ter119⁺ cells) 8 days after 5-FU treatment (n = 4 per genotype; *P < .05). i.p., intraperitoneally.