While leukemogenesis correlates with the ability of Bcr-Abl-expressing cells to competitively expand within progenitor pools, based on increased leukemia rates alone we cannot distinguish whether or not cell autonomous effects of E2f1/E2f2 loss, such as accelerated mutagenesis or decreased apoptosis, are the major factors underlying increased leukemia rates. Here, E2F2 is linked to leukemia.