Aurora B is indispensable for MK precursor mitosis but is dispensable for polyploidization. (A) Effect of AZD1152-HQPA on cell proliferation. MK cultures were treated with AZD1152-HQPA at day 2 (D2) and at day 5 (D5). The cell number with or without inhibitor was counted at time points indicated (n = 3). (B) Effects of Aurora B inhibitor on MK polyploidization. MK cells were treated with AZD1152-HQPA at day 2 (D2) and at day 5 (D5), and after 72 hours the ploidy level was analyzed in the CD41⁺/CD42⁺ cell population. The mean ploidy was calculated from the number of cells of each ploidy class in 3 independent experiments. (C) The number of MKs obtained in each ploidy class after 72 hours of treatment with AZD1152-HQPA at day 2 and at day 5. (D) Effect of AZD1152-HQPA on MK differentiation. AZD1152-HQPA was added to the culture at day 2 or at day 5 for 72 hours. The percentage of mature MKs expressing CD41 and CD42 antigens was analyzed by flow cytometry. Dot plots are from a representative experiment (n = 3).