Barasertib causes growth arrest in the G2/M cells cycle phase. A. Parental (T47D) and fulvestrant resistant (182R-1 and 182R-1) cells treated with barasertib (50 nM) or DMSO (control) for 24–96 hours and subsequently stained with propidium iodide. Cell cycle phase distribution in the following phases are shown: G1 phase, S phase, G2/M phase, SubG1 and >4N (polyploid cells). B. Distribution of cells in G2/M, S, G1 and SubG1 phases and cells with DNA content above 4N are calculated by quantification of the phase fractions seen in A. Duration of barasertib treatment is indicated. Two individual experiments were performed and representative results are shown.