P01.06HIF-1 AND HIF-2 AS POSIBLE NEW TARGETS IN THE TREATMENT OF VON HIPPEL-LINDAU DISEASE HEMANGIOBLASTOMAS

BACKGROUND: Von Hippel-Lindau disease (VHL)is a genetic condition predisposing to the development of multiple specific tumors, mainly CNS and retinal hemangioblastomas and clear cell renal cancer (CCRC). Protein pVHL, codified by VHL gene, is an important component of the functional complex responsible for degrading hypoxia inducible factors (HIF1alpha and HIF2alpha). In hypoxic condition, or in absence of functional protein VHL, an accumulation of HIF results, and thus an activation of gene transcription related to angiogenesis, and cell proliferation and survival. A number of works supports a role of unregulated amplification of HIF activity and of proteins codified by HIF-inducible genes as oncogenic, promoting the development of some tumors as CCRC, in VHL patients. Their role is still unknown in the appearance of hemangioblastomas, as there is no information about the level of synthesis and transcription of HIF proteins in these tumors. The main objective of our study is to determine the levels of proteins HIF-1alpha and HIF-2alpha and the eventual associated VEGF variation. MATERIAL AND METHODS: Tissue from nine hemangioblastomas (cerebellar, spinal cord, brainstem, brain) resected from VHL patients was obtained immediately after each tumor resection, and cultured for growing. Six primary cultures were obtained, and analyzed by Flow Cytometry for cell population component evaluation and by Western-Blot in order to measure the levels of proteins HIF-1alpha, HIF-2alpha and of VEGF. RESULTS: Cellular characterization of the 6 primary cultures obtained from 9 hemangioblastomas has shown they are composed of stromal cells (more than 50% CD99 + cells), endothelial cells (15% CD34+ cells), and pericytes (30% NG2+ cells). In the study, 25-40% of stromal cells, 3-15% of endothelial cells, and 5-30% of pericytes had increased levels of HIF-1alpha and HIF-2alpha. Furthermore, Western-Blot assay showed a very high concentration of VEGF in hemangioblastoma cells, 2 to 4 times more than in cell lines characterized by over-expression of VEGF (lines derived from colon cancer and from retinal pigmentary epithelium). No correlation of HIF expression in culture and cell proliferation in the original tumor (Mib-1) has been found. CONCLUSIONS: Our results show that proteins HIF-1alpha and HIF-2alpha are over-expressed in hemangioblastomas from VHL patients, suggesting a role of these proteins in the development and growth of these tumors. The results support the exploration of possible treatments directed to inactivate HIF1alpha and HIF-2alpha proteins as new targets, in order to control de proliferation of hemangioblastomas in these patients.