IRF-4 inhibits proliferation in BCR/ABL⁺ B-lymphoblasts. (A) Retroviral constructs used to transduce RFP + IRF-4, RFP + IRF-8, and RFP genes. (B) Relative percentage of RFP-expressing cells for BCR/ABL⁺ B lymphoblast cultures derived from BM of moribund BCR/ABL BMT mice suffering from B-ALL like disease. Triplicates of cultures were infected with retroviruses depicted in (A) and RFP expression was determined by FACS analysis. The percentage of RFP-expressing cells for each time point was normalized to the initial percentage of infected cells determined at 3 days after infection. (C) Cell-cycle analysis of RFP positive cells from BM cultures infected with RFP, RFP + IRF-4, or RFP + IRF-8. Analysis of BrdU incorporation and 7-amino-actinomycin D (7-AAD) levels allowed distinction of cell-cycle phases G₁/G₀, G₂/M, S, and dying/dead cells (Ap). Percentage of cells in each phase is indicated within the gate.