Androgens stimulate hypoxia-inducible factor 1 activation via autocrine loop of tyrosine kinase receptor/phosphatidylinositol 3'-kinase/protein kinase B in prostate cancer cells.
OBJECTIVE
Androgen deprivation is implicated in reducing neoangiogenesis in prostate cancer (PCA). Androgens regulate the expression of the vascular endothelial growth factor (VEGF); hypoxia stimulates VEGF expression through the activation of the transcriptional factor, hypoxia-inducible factor 1 (HIF-1). We tested the hypothesis that an effect of androgens on VEGF expression is regulated directly by HIF-1 and HIF-2, and antiandrogens block HIF function.


METHODS
Androgen and antiandrogen effects were evaluated on HIF-1alpha protein and HIF-1 transcriptional activation in human PCA cells.


RESULTS
Dihydrotestosterone (DHT) activates HIF-1alpha nuclear protein expression in LNCaP cells but not in androgen receptor-negative PC-3 cells. HIF-1alpha expression is correlated with the transactivation of a hypoxia-responsive element-driven reporter gene and with the production of VEGF protein. The effect of DHT on HIF-1 was blocked by nonsteroidal antiandrogens, flutamide and bicalutamide. DHT does not affect HIF-1alpha mRNA levels but regulates HIF-1alpha protein expression through a translation-dependent pathway. PC-3 cells when incubated with increasing amounts of conditioned medium from LNCaP cells treated with DHT experienced a dose-dependent increase in HIF-1alpha. This induction was not seen either when LNCaP cells were treated with flutamide or conditioned medium were pretreated with antibody to the epidermal growth factor (EGF). HIF-1 activation by DHT was blocked by LY294002, a potent inhibitor of the phosphatidylinositol 3'-kinase signaling pathway, whereas HIF-1 activation by EGF, as ligand, was not inhibited by flutamide. In contrast, HIF-2alpha protein was not affected by androgens or antiandrogens.


CONCLUSIONS
Androgens activate HIF-1, driving VEGF expression in androgen-sensitive LNCaP cells. This regulation is mediated through an autocrine loop involving EGF/phosphatidylinositol 3'-kinase/protein kinase B, which in turn activate HIF-1alpha and HIF-1-regulated gene expression. Therapeutic actions of antiandrogens in PCA include inhibition of HIF-1 function.
Mabjeesh
Nicola J
NJ
Winship Cancer Institute, Department of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Willard
Margaret T
MT
Frederickson
Carrie E
CE
Zhong
Hua
H
Simons
Jonathan W
JW
D000728:Androgens / Q000378:metabolism*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D013196:Dihydrotestosterone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005485:Flutamide / Q000494:pharmacology; D017930:Genes, Reporter; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D008297:Male; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000378:metabolism*; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D012313:RNA / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D000728:Androgens; D002867:Chromones; D017077:Culture Media, Conditioned; D004268:DNA-Binding Proteins; D013196:Dihydrotestosterone; D004791:Enzyme Inhibitors; D005485:Flutamide; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D009025:Morpholines; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D017430:Prostate-Specific Antigen; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D012313:RNA; D020794:Receptor Protein-Tyrosine Kinases; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C497442:HIF1A protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one