Inhibition of HIF-1 alpha and VEGF expression by the chemopreventive bioflavonoid apigenin is accompanied by Akt inhibition in human prostate carcinoma PC3-M cells

Mol Carcinog. 2008 Sep;47(9):686-700. doi: 10.1002/mc.20421.


Progression of cancer leads to hypoxic solid tumors that mount specific cell signaling responses to low oxygen conditions. An important objective of anti-cancer therapy is the development of new drugs that suppress hypoxic responses in solid tumors. Apigenin is a natural flavone that has been shown to have chemopreventive and/or anti-cancer properties against a number of tumor types. However, the mechanisms underlying apigenin's chemopreventive properties are not yet completely understood. In this study, we have investigated the effects of apigenin on expression of hypoxia-inducible factor-1 (HIF-1) in human metastatic prostate PC3-M cancer cells. We found that hypoxia induced a time-dependent increase in the level of HIF-1alpha subunit protein in PC3-M cells, and treatment with apigenin markedly decreased HIF-1alpha expression under both normoxic and hypoxic conditions. Further, apigenin prevented the activation of the HIF-1 downstream target gene vascular endothelial growth factor (VEGF). We then showed that apigenin inhibited expression of HIF-1alpha by reducing stability of the protein as well as by reducing the level of HIF-1alpha mRNA. We also found that apigenin inhibited Akt and GSK-3beta phosphorylation in PC3-M cells. Further experiments demonstrated that constitutively active Akt blunted the effect of apigenin on HIF-1alpha expression. Taken together, our results identify apigenin as a bioflavonoid that inhibits hypoxia-activated pathways linked to cancer progression in human prostate cancer, in particular the PI3K/Akt/GSK-3 pathway. Further studies on the mechanism of action of apigenin will likely provide new insight into its applicability for pharmacologic targeting of HIF-1alpha for cancer therapeutic or chemopreventive purposes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apigenin / pharmacology*
  • Cell Hypoxia
  • Cell Line, Tumor
  • Flavonoids / pharmacology*
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / antagonists & inhibitors
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics*
  • Male
  • Neoplasm Metastasis
  • Prostatic Neoplasms / pathology*
  • Vascular Endothelial Growth Factor A / antagonists & inhibitors
  • Vascular Endothelial Growth Factor A / genetics*


  • Flavonoids
  • HIF1A protein, human
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Vascular Endothelial Growth Factor A
  • Apigenin