Inhibition of hypoxia inducible factor-1alpha (HIF-1alpha) decreases vascular endothelial growth factor (VEGF) secretion and tumor growth in malignant gliomas.
BACKGROUND
Hypoxia inducible factor-1alpha (HIF-1alpha) regulates vascular endothelial growth factor (VEGF), the presumed principal mediator of angiogenesis in malignant gliomas, under normal physiologic conditions. We examined the effect of HIF-1alpha on VEGF secretion, tumor growth, and angiogenesis in malignant gliomas.


METHODS
We examined 175 human gliomas for expression of HIF-1alpha and its downstream-regulated proteins. HIF-1alpha expression and VEGF secretion in glioma cell lines under normoxia and hypoxia were examined using ELISA and Western blot. Malignant glioma cell lines were transfected with dominant-negative HIF-1alpha (DN-HIF-1alpha) expression vector or siRNA constructs against the HIF-1alpha gene. Growth studies were conducted on cells with the highest VEGF/HIF-1alpha inhibition isolated from stable transfected cell lines. MIB-1-labeling index and microvascular density (MVD) measurements were performed on the in vivo tumors.


RESULTS
HIF-1 expression correlates with malignant glioma phenotype and was not confined to perinecrotic, pseudopalisading cells. VEGF and HIF-1 expression was high in glioma cell lines even under normoxia, and increased after exposure to hypoxia or growth factor stimulation. Cells transfected with DN-HIF-1alpha or HIF-1alpha siRNA demonstrated decreased HIF-1alpha and VEGF secretion. In vivo but not in vitro growth decreased in response to VEGF and HIF-1 inhibition. HIF-1 siRNA studies showed decreased VEGF secretion and in vitro and in vivo growth of glioma cell lines. MVD was unchanged but MIB-1 proliferation index decreased for both types of HIF-1 inhibition.


CONCLUSIONS
VEGF and HIF-1alpha are elevated in malignant gliomas. HIF-1alpha inhibition results in VEGF secretion inhibition. HIF-1alpha expression affects glioma tumor growth, suggesting clinical applications for malignant glioma treatment.
Jensen
Randy L
RL
Department of Neurosurgery, University of Utah, Salt Lake City, Utah 84132-2303, USA. randy.jensen@hsc.utah.edu
Ragel
Brian T
BT
Whang
Kum
K
Gillespie
David
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D020868:Gene Silencing; D005910:Glioma / Q000098:blood supply / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000378:metabolism; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019394:Ki-67 Antigen; D042461:Vascular Endothelial Growth Factor A