3-Hydroxyflavone inhibits endogenous Aurora B and induces growth inhibition of cancer cell line

The Aurora kinases play a critical role in mitosis and have been suggested as promising targets for cancer therapy due to their frequent overexpression in a variety of tumors. Compared with established inhibitors of cell division such as the anti-tubulins, novel agents target mitotic enzymes and show similar efficacy but with fewer side effects. Several small-molecule inhibitors of Aurora kinases have been developed as anticancer agents, some of which have progressed to early clinical evaluation. Here we identified 3-hydroxyflavone as a novel Aurora B inhibitor through high throughput screening. 3-Hydroxyflavone showed potent inhibition to Aurora B with the IC₅₀ on a nanomolar basis in the enzyme-based kinase activity assay. In the cell-based western blotting analysis, 3-hydroxyflavone dramatically decreased the phosphorylation level of Histone H3 on the site of serine 10, demonstrating the potent endogenous Aurora B activity inhibition in cell level. The followed cell image analysis provided the consist result. To make it clear whether 3-hydroxyflavone inhibited Aurora B by direct binding or not, SPR analysis was carried out to measure the affinity of interaction between Aurora B protein and 3-hydroxyflavone and the result proved the binding with high affinity. Usually Aurora activity suppression induced cancer cell proliferation inhibition. Colony formation and cell viability with/without treatment of 3-hydroxyflavone were measured using CCK-8. The growth suppression under 3-hydroxyflavone present and the growth recovery after being released gave strong evidence that presence of 3-hydroxyflavone efficiently inhibited the fast growth of cancer cells.