(A) HEL erythroleukemia cells and ALL-SIL T acute lymphoblastic leukemia cells were treated with vehicle (DMSO), JQ1 (0.5 μM) or the indicated TKIs (1 μM) for 6 hours, after which cells were harvested and immunoblots were performed to STAT5 and phosphorylated STAT5. (B) ALL-SIL cells were infected with one of three shRNA constructs targeting BRD2 or GFP (as a control). Three days after puromycin selection, cells were harvested and immunoblots were performed with the indicated antibodies. (C) Cells were treated with vehicle, JQ1 (0.5 μM) or imatinib (1 μM) for 6 hours, after which cells were harvested and ChIP was performed. STAT5 and RNA polymerase II binding were analyzed relative to a known STAT5-negative binding region. (D) Comparison of CIS transcripts close to the transcriptional start site (designated as pre-CIS) and the mature form of CIS RNA level by quantitative RT-PCR (normalized to 18S RNA)