E/F; control mouse had an average of 8 CFCs/100,000 cells, while splenocytes of a littermate mouse with EWS-FLI1 induced leukemia of the same sex and age had significantly increased CFCs (an average of 563 CFCs/100,000 cells) suggesting that most of these CFCs are leukemic progenitors (Figure 3A). This evidence concerns the gene FLI1 and leukemia.