gms | German Medical Science

Objective: Inhibition of Aurora kinase B by RNA interference or small chemical compounds has been shown to block solid tumor growth in many different tumor entities even in gliomas. In this study we sought to elucidate the role of the tumor suppressor protein p53 in the cell cycle regulation and chromosomal segregation of U87-MG glioma cells treated with the specific Aurora B inhibitor Barasertib (AZD1152-HQPA).

Method: The tumor suppressor p53 was stably knocked down in U87-MG glioma cells by a retroviral vector encoding the small hairpin shRNA targeting p53. Cells were either incubated with Aurora B Inhibitor (AZD1152-HQPA) or DMSO and subjected to cell cycle analysis, apoptosis assays, Western blot analysis, flow cytometry and proliferation analysis.

Results: Aurora B inhibition resulted in wild type and p53-deficient (shp53) U87-MG cells in a significant increase in the amount of polyploid cells with defective mitosis compared to control cells (DMSO). However, an induction of p21waf/cip on the steady state protein level was only observed in U87-MG wild type cells expressing functional p53. Determination of proliferation by BrdU-incorporation analysis and clonal survival experiments indicated an impaired cell growth of wild type and p53-deficient U87-MG cells after Barasertib treatment. But even polyploid cells irrespective of p53 wt expression or p53-deficiency showed BrdU incorporation in cells having a DNA content >4N indicating further intrinsic cell cycle progression. SubG1 analysis revealed a twofold increase in the fraction of dead cells in those cells treated with Aurora B inhibitor compared to controls. Yet, western blot analysis showed no increase in cleaved caspase 3, suggesting that cell death caused by aurora B inhibition occurs rather by mitotic catastrophe than organized apoptosis.

Conclusions: Our results suggest that Aurora B inhibition severely affects proliferation and survival of glioma cells irrespective of p53 status. Therapies targeting Aurora B might represent a promising avenue for adjuvant local treatment of secondary and primary glioblastoma.