In Vitro Screen for Inhibitors of Aurora-A

Target Discovery and Apoptosis Team

Section: Cancer Research UK Cancer Therapeutics Unit

The Aurora-A gene encodes a centrosome-associated serine/threonine kinase. Aurora-A is a member of a family of Aurora kinases that includes Aurora B and STK13. In somatic cells Aurora-A mRNA, protein and kinase activity levels are cell cycle-regulated and peak during mitosis. The Aurora-A gene has been found to be amplified in more than 50% of primary colorectal cancers and 12% of primary breast tumours, as well as in breast, ovarian, colon and prostate cell lines. The evidence to date suggests that inhibition of Aurora-A could result in anti-tumour effects. Further support for this hypothesis comes from the use of Aurora-A antisense oligonucleotides and RNAi, both of which result in cell arrest at G2/M phase of the cell cycle. Thus, Aurora-A represents an attractive target for anticancer drug discovery.

The availability of a robust and selective small molecule inhibitor of Aurora-A kinase would provide lead molecules for clinical drug development, and in addition may also be a useful tool for identification of the Aurora-A role in regulation of mitosis and tumour development. We have developed a new enzymatic assay for identification of Aurora-A small molecule inhibitors based on the Scintillation Proximity Assay (SPA). The assay has proved to be extremely sensitive, fast and simple. The SPA assay was used successfully for screening of approximately 70,000 compounds for Aurora-A inhibition. Initial hits obtained by the high throughput screening of the Centre for Cancer Therapeutics’ collection of compounds were evaluated. Overall, we will be looking for directional Structure-Activity Relationship (SAR) regarding potency against the enzyme.

In addition, in collaboration with the Section of Structural Biology (ICR), suitable chemical leads will be optimised using structural information from co-crystallisation studies with Aurora-A. The ultimate goal of this exploratory chemistry phase is to select at least two structural templates for lead optimisation. Finally, our lab is focusing in identification of specific biomarkers for Aurora-A inhibition to use as lead optimisation and clinical endpoints.