BAY 1143572 inhibits proliferation in primary ATL cells from patients. (A) The viabilities of primary ATL cells from 11 individual patients, in the presence of recombinant human IL-2 at a final concentration of 100 IU/mL and with different concentrations of BAY 1143572 for 24 hours, were assessed. Primary ATL cells were isolated from PBMCs (nos. 1-8, 10, 11) or the affected lymph node (no. 9) of ATL patients. The clinical subtype of each ATL patient is indicated above each panel. The IC₅₀ value for primary cells of each ATL patient is indicated in each panel and was determined by a cell proliferation assay. The absolute IC₅₀ value for each primary ATL cell line is also indicated in parentheses below the IC₅₀ value. (B) The viabilities of human CD4⁺ cells from PBMCs of 5 healthy volunteers, in the presence of recombinant human IL-2 at a final concentration of 100 IU/mL and with different concentrations of BAY 1143572 for 24 hours, were assessed. The IC₅₀ value for cells isolated from each healthy volunteer is indicated in each panel and was determined by a cell proliferation assay. The absolute IC₅₀ value for each CD4⁺ cell line is also indicated in parentheses below the IC₅₀ value. (C) Primary ATL cells from 5 individual patients, and (D) CD4⁺ cells obtained from 3 healthy volunteers were treated with the indicated concentrations of BAY 1143572 for 12 hours, and western blotting was performed. Blots were probed with antibodies to phospho-RNAPII (Ser2), phospho-RNAPII (Ser5), RNAPII (N-20), c-Myc, and Mcl-1. Actin was used as a loading control.