Flavonoids as RTK inhibitors and potential anticancer agents

Tyrosine kinase receptors (RTKs) play a crucial role in the regulation of the cell division cycle. Currently more than 50 RTKs divided into several subfamilies have been described. The inhibition of these enzymes has emerged as an important research-area. Compounds able to inhibit the activity of these enzymes are expected to display antiproliferative properties. Flavonoids are representative of various small molecules acting as RTK inhibitors. These naturally occurring compounds are able to bind to the ATP-binding site of several kinases. The most plausible current hypothesis explaining the action of these substances on kinases is that the chromenone moiety of the flavonoid acts as a mimetic of the adenine moiety of ATP, the receptor co-factor. In this review, we report recent results on the activity of natural and synthetic derivatives of flavonoids as inhibitors of RTKs. Mechanistic aspects, the therapeutic usefulness, and the potential clinical use are discussed.