Fulvestrant resistant cell lines exhibit increased Aurora kinase B phosphorylation, and barasertib abolishes phosphorylation of Aurora kinase B and Histone-H3. A. Western blots showing total and phosphorylated (p) form of Aurora kinase B (Thr232) and Aurora kinase A (Thr288) in lysates from parental (T47D) and fulvestrant resistant (182R-1 and 182R-2) cells treated with barasertib (50 nM) or DMSO (control) for 4 hours. Heat shock protein 70 (Hsp70) was used as loading control. B. Parental and resistant cells were treated with barasertib (50 nM) or DMSO (control) for 24 hours before the cells were fixed and stained with phospho-Histone-H3 Ser10 antibody and propidium iodide prior analysis and flow cytometry performed using a FACsort flow cytometer. M-phase phospho-Histone-H3 Ser10 positive cells are encircled and the bold numbers indicate percentage of positive cells in each sample. Representative experiments are shown.