Abstract
Inhibition of Aurora kinase activity by small molecules is being actively investigated as a potential anti-cancer strategy. A successful therapeutic use of Aurora inhibitors relies on a comprehensive understanding of the effects of inactivating Aurora kinases on cell division, a challenging aim given the pleiotropic roles of those kinases during mitosis. Here we have used the Aurora-A inhibitor MLN8237, currently under phase-I/III clinical trials, in dose-response assays in U2OS human cancer cells synchronously proceeding towards mitosis. By following the behaviour and fate of single Aurora-inhibited cells in mitosis by live microscopy, we show that MLN8237 treatment affects multiple processes that are differentially sensitive to the loss of Aurora-A function. A role of Aurora-A in controlling the orientation of cell division emerges. MLN8237 treatment, even in high doses, fails to induce efficient elimination of dividing cells, or of their progeny, while inducing significant aneuploidy in daughter cells. The results of single-cell analyses show a complex cellular response to MLN8237 and evidence that its effects are strongly dose-dependent: these issues deserve consideration in the light of the design of strategies to kill cancer cells via inhibition of Aurora kinases.
Highlights
The Aurora-A kinase is a major regulator of cell division and operates in distinct processes required for spindle assembly: in human cells it regulates separation and maturation of centrosomes at mitotic entry, mitotic microtubule (MT) nucleation [1,2,3] and the integrity of spindle poles [2, 4, 5]
We set up a protocol by pre-synchronizing U2OS cells at the G1/S transition by thymidine treatment, releasing from arrest into G2 and mitosis (Figure 1A)
We have used the MLN8237 small molecule inhibitor to investigate mitotic roles of the Aurora-A kinase in osteosarcoma U2OS cells; this molecule is under clinical trial in several cancer types including osteosarcoma
Summary
The Aurora-A kinase is a major regulator of cell division and operates in distinct processes required for spindle assembly: in human cells it regulates separation and maturation of centrosomes at mitotic entry, mitotic microtubule (MT) nucleation [1,2,3] and the integrity of spindle poles [2, 4, 5]. The highly homologous Aurora-B kinase operates in control of the fidelity of chromosome segregation, by regulating chromosome condensation, correction of improper attachments between MTs and kinetochores, spindle checkpoint function, cytokinesis and abscission [8]. Aurora kinases are often abnormally expressed in tumor cells and are being investigated as targets of anti-mitotic compounds for cancer therapy [9, 10]. A few of those molecules discriminate Aurora-A vs Aurora-B and may prove useful both in clinical studies for comparing the efficacy of anti-tumor responses and for dissecting the functions of Aurora kinases in mammalian cells
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