Knock down of HIF-1α in glioma cells reduces migration in vitro and invasion in vivo and impairs their ability to form tumor spheres

Background: Glioblastoma (GBM) is the most common and malignant primary intracranial human neoplasm. GBMs are characterized by the presence of extensive areas of necrosis and hypoxia. Hypoxia and its master regulator, hypoxia inducible factor 1 (HIF-1) play a key role in glioma invasion. Results: To further elucidate the functional role of HIF-1 alpha in glioma cell migration in vitro and in invasion in vivo, we used a shRNA approach to knock down HIF-1 alpha expression complemented with genome-wide expression profiling, performed in both normoxic and hypoxic conditions. Our data show that knock down of HIF-1 alpha in glioma cells significantly impairs their migration in vitro as well as their ability to invade into the brain parenchyma in vivo. Next, we assessed the role that HIF-1 alpha plays in maintaining the characteristics of cancer stem cells (CSCs). By using the tumor sphere forming assay, we demonstrate that HIF-1 alpha plays a role in the survival and self-renewal potential of CSCs. Finally, expression profiling experiments in glioma cells provided detailed insight into a broad range of specific biological pathways and processes downstream of HIF-1 alpha. We discuss the role of these processes in the migratory and invasive properties, as well as the stem cell biology of glioblastomas Conclusions: Our data show that knock down of HIF-1a in human and murine glioma cells impairs their migration in vitro and their invasion in vivo. In addition, our data suggest that HIF-1 alpha plays a role in the survival and self-renewal potential of CSCs and identify genes that might further elucidate the role of HIF-1 alpha in tumor migration, invasion and stem cell biology.