Abstract 5032: MK8745, an Aurora A kinase-specific inhibitor induces apoptosis in a p53-dependent manner

Abstract

Abstract Aurora kinases are mitotic serine/threonine protein kinases and are attractive novel targets for anticancer therapy. Many small molecule inhibitors are being developed and few are currently undergoing clinical trials. Aurora A kinase is essential for the successful mitotic transition. MK8745 is a novel and selective small molecule inhibitor of Aurora A kinase. Treatment of tumor cells with MK8745 (1 to 5 µM) resulted in accumulation of cells in mitosis with an increase in Aurora A expression. Despite this increase in Aurora A in the cells, dose dependent inhibition of Aurora A kinase activity was confirmed by an in vitro kinase assay using a PLK1, a specific substrate of Aurora A kinase. Also, treatment of HCT116 (p53−/−) cells ectopically overexpressing wild type p53 with MK8745 showed a decrease in phospho p53 (ser315), another known substrate of Aurora A. We then explored the mechanism by which MK8745 induces proliferation inhibition in cell lines of multiple lineages such as colon, melanoma, sarcoma and pancreatic according to p53 status. In general, the cell lines expressing wild type p53 showed a short delay in mitosis followed by cytokinesis with significant apoptosis (15%) upon exposure to MK8745. However, cell lines with null or mutant p53 underwent endoreduplication resulting in 60% polyploidy after a prolonged delay in mitosis with no apoptosis. This was further confirmed in the isogenic HCT-116 cell lines such that HCT p53−/− cells underwent polyploidy, whereas HCT p53 +/+ and the HCT p21 −/− cells underwent apoptosis. Under all of these conditions phospho histone H3 (Ser10) was not inhibited, indicating these phenotypic effects are a result of Aurora A inhibition and not Aurora B. P53 dependence for apoptosis was also confirmed in p53 null cells overexpressing wild type p53. Transient knock down of Aurora A kinase by specific SiRNA resulted in high levels of apoptosis and again showed p53 dependence. These results suggest that determining the p53 status may be important when using Aurora A kinase targeted therapies in the clinic. Further studies are underway to determine the role of p53 in the induction of apoptosis that results from inhibition of Aurora A kinase. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5032.