H1299 cells were treated with DMSO, sepantronium (20 nM), volasertib (40 nM), sepantronium and volasertib. Cell cycle distribution was analyzed at 24 h (A), 72 h (B). Confocal laser microscopy images were taken to show details of chromosomes and mitotic spindles (C). In (D), Western blot of cyclin B and survivin expression in H1299 cells treated for 24 hours at the same concentrations.