Sox4 is required for pre-B ALL cell survival and proliferation. Effects of inducible activation of Cre or empty vector (EV) control in Sox4^fl/fl pre-B ALL cells was studied on viability/apoptosis (A), cell cycle regulation (B), and colony formation in methylcellulose (C). In panel A, Sox4^fl/fl was deleted in IL7-dependent normal pre-B cells (top) and BCR-ABL1–transformed ALL cells and viability changes were measured in both after 2 days of induction of Cre. In panel B, cells were stained with BrdU and 7AAD after 1 day of Sox4 deletion and percentages of cells in G₀/1, S and G₂/M phases of the cell cycle are indicated (n = 3; P = .008 for S phase) and shown in a bar graph (bottom). In panel C images for colonies in a serial replating assay are shown and quantitative analysis (right; n = 3).