Bim contributes to DNA-damage response of Eμ-Myc lymphomas in vivo. (A) Eμ-Myc cell lines or Eμ-Myc cell lines lacking p53 were treated with etoposide (1 μg/mL) for 3 or 6 hours and assessed for the levels of BH3-only gene mRNA. Mean ± SEM from 3 independent experiments. (B) Eμ-Myc cell lines or Eμ-Myc cell lines lacking p53 were left untreated or treated with etoposide (1 μg/mL) in the presence of QVD-OPH (25μM) for 6 or 18 hours and assessed for the levels of BIM protein by Western blotting, with β-actin serving as a loading control. (C) Cell lines derived from independent Eμ-Myc lymphomas of the indicated genotypes (lacking Bik, Bad, Bim, Bid, Bmf, or p53) were treated with etoposide (0.2 μg/mL) for the indicated times in vitro and cell death was assessed by flow cytometry. Mean ± SEM from 3-7 independent cell lines per genotype, with each cell line analyzed in at least 3 independent experiments. No significant differences were noted, except for the Eμ-Myc/p53^−/− cell lines. (D-E) Response of Eμ-Myc lymphomas to CTX in vivo, shown as Kaplan-Meier survival curves. Mice were transplanted with Eμ-Myc lymphoma cells (d0) and treated, once spleens were palpable, from around d12. Pre-B (D) or B-cell (E) Eμ-Myc and Eμ-Myc/Bim^−/− lymphomas were treated with 200 or 300 mg/kg CTX. Data were pooled from 2-13 independent lymphomas of each genotype; 2-10 recipient mice per treatment per independent lymphoma (supplemental Table 1).