Figure 5. Inhibition of Brd2 increases sensitivity of leukemia cells to TKIs.

(A) HEL and (B) ALL-SIL cells were infected with lentiviral vectors containing distinct shRNAs targeting BRD2. After 4 days of selection in puromycin, cells were treated with TKIs as indicated. Cell viability was measured 72 hours after drug treatment. (C) Parental ALL-SIL cells or cells with Brd2 knock-down were treated with imatinib for 48 hours, after which apoptosis was quantitated by annexin V and PI staining followed by flow cytometry. (D) The indicated leukemia cell lines were treated for 72 hours with JQ1 or the indicated TKI, alone or in combination. Isobologram analysis was performed based on change in viable cell number after treatment. Data points below the line indicate synergy between the two agents. (E) ALL-SIL cells were treated with JQ1 (0.5 μM), imatinib (0.125 μM), or both for 48 hours, after which apoptosis was quantified by annexin V staining and flow cytometry. (F) ALL-SIL or DND41 T lymphocytic leukemia cells were infected with a vector expressing either GFP alone or GFP and constitutively activated STAT5a (caSTAT5a). Cells were then treated with JQ1 (0.25 μM), Jak inhibitor 1 (1 μM), or imatinib (0.125 μM), or the indicated combinations for 72 hours, and the fraction of GFP positive cells was quantified by flow cytometry and normalized to the vehicle (DMSO) control.