Cotreatment with JQ1 and PS or palbociclib is synergistically active in ibrutinib-resistant Mino/IR cells. (A) Representative immunoblots of basal protein expression in Mino vs Mino/IR cells. (B) Mino and Mino cells with acquired resistance to ibrutinib (Mino/IR) were treated with the indicated concentrations of JQ1 for 48 hours. The percent of Annexin V-positive apoptotic cells was determined by flow cytometry. (C) Immunoblot analyses of Mino and Mino/IR cells treated for 24 hours with JQ1, as indicated. The numbers beneath the bands represent densitometry analysis. (D-G) Mino/IR cells were treated with a fixed ratio of JQ1 and PS (D), or palbociclib (E), or ABT-737 (F), or ABT-199 (G) for 48 hours. The percent of apoptotic cells was determined by flow cytometry. Median dose effect and isobologram analyses were performed. CI values <1.0 indicates a synergistic interaction of the two agents in the combination. Doses of drugs, fractional effect, and CI values are provided in supplemental Figure 6B. n.s., not significant.