Chrysin inhibits expression of hypoxia-inducible factor-1 alpha through reducing hypoxia-inducible factor-1 alpha stability and inhibiting its protein synthesis

Chrysin is a natural flavonoid and has been shown recently to have anticancer effects. However, the mechanisms that chrysin inhibits cancers are not well known. In this study, we investigated the effects of chrysin on expression of hypoxia-inducible factor-1 alpha (HIF-1 alpha) and vascular endothelial growth factor in human prostate cancer DU145 cells. Chrysin inhibited insulin-induced expression of HIF-1 alpha by reducing its stability. Chrysin increases ubiquitination and degradation of HIF-1 alpha by increasing its prolyl hydroxylation. In addition, chrysin interfered with interaction between HIF-1 alpha and heat shock protein 90. Chrysin was also found to inhibit HIF-1 alpha expression through AKT signaling. Inhibition of HIF-1 alpha by chrysin resulted in abrogation of vascular endothelial growth factor expression. Finally, we showed that chrysin inhibited DU145 xenograft-induced angiogenesis in nude mice. Taken together, these results suggest that chrysin is a potent inhibitor of HIF-1 alpha and provide a new sight into the mechanisms of chrysin against cancers.