E–H. Cell cycle and apoptosis analysis of IFN-β treated v-abl-transformed cell lines, 2 and 9 days after IFN-β treatment, respectively. Deletion of Stat5 induces a cell cycle arrest (F) and apoptosis (H), while deletion of Stat3 has no significant effect on evaluated parameters (E, G). Numbers show percentages of cells in indicated cell cycle phases (E, F) or in different stages of apoptosis (G, H). Re-expression of Stat5 target genes (D-type cyclins, c-myc, bcl-xL or bcl-2) failed to rescue Stat5-deficiency (I).