Proliferation or spontaneous apoptosis are unchanged in preneoplastic B-lymphoid cells between Eμ-myc/Suz12^+/+ and Eμ-myc/Suz12^Plt8/+ mice. (A) Limiting dilution analysis of unfractionated bone marrow cells from preneoplastic Eμ-myc/Suz12^+/+ (n = 4) and Eμ-myc/Suz12^Plt8/+ (n = 3) mice. (B) Unfractionated bone marrow cells from preneoplastic Eμ-myc (n = 6) and Eμ-myc/Suz12^Plt8/+ (n = 7) mice were cultured in methylcellulose and scored 7 days later. Data represent means ± SEM. A 2-tailed Student t test was performed (*P < .05). (C) BrdU incorporation in Eμ-myc (n = 3) and Eμ-myc/Suz12^Plt8/+ (n = 3) cells 1 hour after BrdU injection (0.1 mg/mg body weight). The percentage of BrdU⁺ cells in bone marrow pro-B, pre-B, and sIg⁺ B cells and in splenic pre-B and sIg⁺ B cells was determined by FACS. Data represent means ± standard deviation. A 2-tailed Student t test was used to determine statistical significance. In vitro survival assay was performed on cells from preneoplastic Eμ-myc, Eμ-myc/Bmi1^+/−, and Eμ-myc/Suz12^Plt8/+ mice. FACS-purified bone marrow (D) pre-B and (E) sIg⁺ B cells were cultured under conditions of cytokine deprivation. Cell viability was measured by Annexin-V and propidium iodide staining using flow cytometry. Three-week-old nontransgenic wildtype (^+/+), Bmi1^+/−, and Suz12^Plt8/+mice were included as controls. Data represent means ± SEM at each time point. One-way analysis of variance followed by Tukey’s post hoc test was used to compare mice of the following genotypes: wildtype (^+/+), Bmi1^+/−, and Suz12^Plt8/+, either carrying the Eμ-myc transgene or the corresponding nontransgenic controls.