HIF-1alpha and HIF-2alpha are differentially regulated in vivo in neuroblastoma: high HIF-1alpha correlates negatively to advanced clinical stage and tumor vascularization.
OBJECTIVE
Hypoxia is considered to be a major driving force behind tumor angiogenesis. The stabilization and activation at hypoxia of the hypoxia-inducible factors HIF-1alpha and HIF-2alpha and the concomitant induction of expression of vascular endothelial growth factor (VEGF) and other proangiogenic factors provide a molecular frame for hypoxia-driven tumor angiogenesis. This study has investigated how HIF and VEGF protein levels relate to each other with regard to vascularization, tumor stage, and overall survival in neuroblastoma.


METHODS
Tissue cores taken from tumor specimens representing 93 children with neuroblastoma were arranged on a microarray and stained for HIF-1alpha, HIF-2alpha, VEGF, and CD31 proteins. Both fraction of positive cells and staining intensity were evaluated and protein levels were correlated with each other and with clinical variables.


RESULTS
Although high levels of both HIF-1alpha (P < 0.001) and HIF-2alpha (P < 0.001) correlated positively to VEGF expression, they did not fully correlate with each other. Moreover, HIF-1alpha (P = 0.002) and VEGF (P < 0.001), but not HIF-2alpha, correlated negatively to vascularization as determined by CD31 staining abundance. VEGF expression or degree of vascularization did not correlate with tumor stage or overall survival. High HIF-1alpha levels correlated with low tumor stage (P < 0.001) and were associated with a favorable patient prognosis (P = 0.08).


CONCLUSIONS
The discordant results on expression of HIF-1alpha and HIF-2alpha suggest that these two proteins are differentially regulated in vivo, thus reflecting distinctive protein expression/stabilization mechanisms. The association between HIF-1alpha and favorable outcome stresses the importance of discriminating HIF-2alpha from HIF-1alpha expression and has implications for using HIFs as treatment targets.
Noguera
Rosa
R
Department of Pathology, University of Valencia, Medical School, Valencia, Spain.
Fredlund
Erik
E
Piqueras
Marta
M
Pietras
Alexander
A
Beckman
Siv
S
Navarro
Samuel
S
Påhlman
Sven
S
D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002675:Child, Preschool; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007223:Infant; D008297:Male; D008954:Models, Biological; D009369:Neoplasms / Q000098:blood supply / Q000473:pathology*; D009389:Neovascularization, Pathologic; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D016896:Treatment Outcome; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1