Hypoxic Induction of the Regulator of G-Protein Signalling 4 Gene Is Mediated by the Hypoxia-Inducible Factor Pathway
Hemangioblastomas, the most frequent manifestation of the hereditary von Hippel-Lindau disease (VHL), are highly vascularized tumors of the central nervous system. In previous studies, the endothelial-specific mitogen vascular endothelial growth factor (VEGF) was shown to be up-regulated in the stromal cells, the putative neoplastic cells in hemangioblastomas. Therefore, it was suggested that secretion of VEGF by stromal cells is the pathogenetic cause of the vascular lesions in hemangioblastomas. The novel basic helix loop helix transcription factor HRF/HIF-2alpha is a candidate regulator of VEGF expression during development. We therefore investigated expression of HRF/HIF-2alpha in hemangioblastomas and found the overexpression of VEGF mRNA in stromal cells to be highly correlated with elevated expression levels of HRF/HIF-2alpha mRNA. This finding is suggestive for a role of HRF in VEGF-dependent vascular growth in hemangioblastomas and could provide a link between transcriptional activation of the VEGF gene and loss of function of the VHL gene product.