Endothelin-1 inhibits prolyl hydroxylase domain 2 to activate hypoxia-inducible factor-1alpha in melanoma cells.

Abstract

BACKGROUND:

The endothelin B receptor (ET(B)R) promotes tumorigenesis and melanoma progression through activation by endothelin (ET)-1, thus representing a promising therapeutic target. The stability of hypoxia-inducible factor (HIF)-1alpha is essential for melanomagenesis and progression, and is controlled by site-specific hydroxylation carried out by HIF-prolyl hydroxylase domain (PHD) and subsequent proteosomal degradation.

PRINCIPAL FINDINGS:

Here we found that in melanoma cells ET-1, ET-2, and ET-3 through ET(B)R, enhance the expression and activity of HIF-1alpha and HIF-2alpha that in turn regulate the expression of vascular endothelial growth factor (VEGF) in response to ETs or hypoxia. Under normoxic conditions, ET-1 controls HIF-alpha stability by inhibiting its degradation, as determined by impaired degradation of a reporter gene containing the HIF-1alpha oxygen-dependent degradation domain encompassing the PHD-targeted prolines. In particular, ETs through ET(B)R markedly decrease PHD2 mRNA and protein levels and promoter activity. In addition, activation of phosphatidylinositol 3-kinase (PI3K)-dependent integrin linked kinase (ILK)-AKT-mammalian target of rapamycin (mTOR) pathway is required for ET(B)R-mediated PHD2 inhibition, HIF-1alpha, HIF-2alpha, and VEGF expression. At functional level, PHD2 knockdown does not further increase ETs-induced in vitro tube formation of endothelial cells and melanoma cell invasiveness, demonstrating that these processes are regulated in a PHD2-dependent manner. In human primary and metastatic melanoma tissues as well as in cell lines, that express high levels of HIF-1alpha, ET(B)R expression is associated with low PHD2 levels. In melanoma xenografts, ET(B)R blockade by ET(B)R antagonist results in a concomitant reduction of tumor growth, angiogenesis, HIF-1alpha, and HIF-2alpha expression, and an increase in PHD2 levels.

CONCLUSIONS:

In this study we identified the underlying mechanism by which ET-1, through the regulation of PHD2, controls HIF-1alpha stability and thereby regulates angiogenesis and melanoma cell invasion. These results further indicate that targeting ET(B)R may represent a potential therapeutic treatment of melanoma by impairing HIF-1alpha stability.

• Authors: Francesca Spinella, Laura Rosanò, Martina Del Duca, Valeriana Di Castro, Maria Rita Nicotra, Pier Giorgio Natali, Anna Bagnato
• Journal: PloS one (PLoS One) Vol. 5 Issue 6 Pg. e11241 (Jun 21 2010) ISSN: 1932-6203 [Electronic] United States
• PMID: 20574527 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Basic Helix-Loop-Helix Transcription Factors
• Endothelin B Receptor Antagonists
• Endothelin-1
• HIF1A protein, human
• Hypoxia-Inducible Factor 1, alpha Subunit
• Receptor, Endothelin B
• endothelial PAS domain-containing protein 1
• EGLN1 protein, human
• Procollagen-Proline Dioxygenase
• Hypoxia-Inducible Factor-Proline Dioxygenases
• integrin-linked kinase
• Protein Serine-Threonine Kinases
• Proto-Oncogene Proteins c-akt

Topics

• Animals
• Basic Helix-Loop-Helix Transcription Factors (metabolism)
• Cell Line, Tumor
• Endothelin B Receptor Antagonists
• Endothelin-1 (metabolism, pharmacology, therapeutic use)
• Female
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Hydroxylation (drug effects)
• Hypoxia-Inducible Factor 1, alpha Subunit (chemistry, metabolism)
• Hypoxia-Inducible Factor-Proline Dioxygenases
• Male
• Melanoma (blood supply, genetics, metabolism, pathology)
• Mice
• Neoplasm Invasiveness (pathology)
• Neovascularization, Pathologic (drug therapy)
• Phosphatidylinositol 3-Kinases (metabolism)
• Procollagen-Proline Dioxygenase (antagonists & inhibitors, genetics, metabolism)
• Promoter Regions, Genetic (genetics)
• Protein Serine-Threonine Kinases (metabolism)
• Protein Stability (drug effects)
• Proto-Oncogene Proteins c-akt (metabolism)
• Receptor, Endothelin B (metabolism)
• Signal Transduction (drug effects)
• Substrate Specificity