UCSF

Glioblastoma continues to rank among the most lethal primary human tumors. Despite treatment with the most rigorous surgical, chemotherapeutic, and radiation regimens, the median survival is just 12-15 months after diagnosis for patients with glioblastoma. One feature of glioblastoma associated with poor prognosis is the degree of hypoxia and expression levels of hypoxia-inducible factor-1 α (HIF-1α). HIF-1α expression allows metabolic adaptation to low oxygen availability, partly through upregulation of vascular endothelial growth factor (VEGF) and increased tumor angiogenesis. In this study, we demonstrate an induced level of astrocyte-elevated gene-1 (AEG-1) in high-grade as compared to low-grade astrocytomas and association of AEG-1 with necrotic areas in glioblastoma. AEG-1 was recently demonstrated to be an oncogene that can induce angiogenesis in glioblastoma. Results from in vitro studies show that AEG-1 is induced by hypoxia in a HIF-1α-dependent manner and that PI3K inhibition abrogates AEG-1 induction during hypoxia. Furthermore, we show that AEG-1 is induced by glucose deprivation and that prevention of intracellular reactive oxygen species (ROS) accumulation prevents this induction. Additionally, AEG-1 knockdown results in increased, whereas AEG-1 overexpression results in decreased, ROS production and glucose deprivation-induced cytotoxicity, indicating that AEG-1 induction is necessary for cells to survive this type of stress. Moreover, AEG-1 modulates the expression of glycolytic enzymes in glioblastoma cells in vitro and in vivo and regulates the expression of these enzymes as well as glycolytic flux during metabolic stress, such as glucose deprivation. The AEG-1-induced glycolytic profile in glioblastoma cells is also modulated by glycolytic inhibition. Studies in nude mice demonstrate that AEG-1 knockdown reduces the growth of glioblastoma xenografts and also promotes chemosensitivity to glycolytic inhibition in vitro. These findings identify a novel role for AEG-1 in the regulation of glycolysis in glioblastoma and indicate that anti-glycolytic therapies may be useful in treating malignancies that demonstrate AEG-1-overexpression.