Up-regulation of SOX4 in response to TKI treatment in Ph⁺ ALL. Ph⁺ ALL (BV173, SUP-B15, TOM1, and NALM1; supplemental Table 6) and murine pre-B ALL were treated with the tyrosine kinase inhibitor (TKI) Imatinib for 16 hours (IM; A). Based on gene expression analyses we identified SOX4 as a gene that is highly up-regulated. BCR-ABL1–transformed mouse pre-B ALL cells were treated with or without Imatinib (IM; 2μM) for 16 hours and mRNA levels of SOX4 were measured by quantitative RT-PCR (B). In panel C, 3 human Ph⁺ ALL cell lines were treated with or without Imatinib (IM; 2μM) for 16 hours and SOX4 protein levels were assayed by Western blot using β-actin as loading control.