RB/E2F1-induced apoptosis requires FOXO1. A. REF52 cells were stably integrated with shRNAs specific for AKT phosphorylation targets, infected with control or E2F1-expressing adenovirus, and measured for active caspase-3 levels (n = 3). B. U2OS cells were transfected with control or four individual FOXO1 siRNAs (n = 3), the deprived of serum, infected with adeno-E2F1, and measured for cleaved caspase-3 levels. C. Y79 cells transfected with control or FoxO1 siRNAs were infected with control or AdE2F1 and gene expression of BIM, TRP73, CDKN1B, (p27KIP1) and CDKN2A (p14ARF) was measured (n = 3). The fold induction by E2F1 is listed above each set. *, p < 0.05; **, p < 0.01; ***, p < 0.001. Error bars represent standard deviation from the mean.