BAY 1143572 inhibits proliferation, induces apoptosis, and affects CDK9 signaling in HTLV-1⁻human T-ALL cell lines. (A) Viabilities of T-ALL cell lines (Jurkat, CCRF-CEM, and TALL-1) in the presence of different concentrations of BAY 1143572 for 72 hours were assessed. The IC₅₀ value for each line is indicated in each panel. The absolute IC₅₀ value for each line is also indicated in parentheses below the IC₅₀ value. (B) T-ALL cell lines were treated with various concentrations of BAY 1143572 for 72 hours. Apoptosis was then analyzed by Annexin V and PI (nuclear) staining and flow cytometry. BAY 1143572 concentrations are indicated above the panels, and the percentage of cells in each quadrant is indicated in or beside each quadrant. (C) Jurkat, CCRF-CEM, and TALL-1 cell lines were treated with the indicated concentrations of BAY 1143572 for 5 hours, protein extracts prepared, and western blotting performed. Blots were probed with antibodies to phospho-RNAPII (Ser2 of the CTD [Ser2]) phospho-RNAPII (Ser5), RNAPII (N-20), c-Myc, and Mcl-1. Actin was used as a loading control.