E2F and Myc-Induced Lymphoma Figure 3. E2F2 and E2F4 do not influence the viability of pretumorous B lineage cells or the incidence of p19Arf-Mdm2-p53 alterations in Myc-induced lymphomas. (A) Representative experiment assessing the viability of B lineage cells (small pre-B and more mature stages) isolated from pretumorous mice of the E2F2 cohort and cultured in the absence of cytokines. Flow cytometry was used to assess viability over time in culture, with B220+ cells negative for both activated caspase 3 and 7-AAD identified as viable. Error bars show standard deviations. (B) Representative experiment assessing the viability of B lineage cells (small pre-B and more mature stages) isolated from pretumorous mice of the E2F4 cohort and cultured in the absence of cytokines. Error bars show standard deviations. (C) Incidence of p53, p19ARF, and Mdm2 alterations in the lymphomas emerging from Em-Myc transgenic mice of the indicated E2F genotypes. p53 and p19ARF deletions were identified by Southern blotting, and p53, p19ARF, and Mdm2 overexpression by western blotting. As p19ARF overexpression can result from loss of p53 function, tumors were counted as having p19ARF overexpression only when independent of p53 mutation or deletion. Mdm2 overexpression was counted only if exclusive of defects in p53 or p19ARF. doi:10.1371/journal.pgen.1000640.g003 PLoS Genetics | www.plosgenetics.org 6 September 2009 | Volume 5 | Issue 9 | e1000640