EPAS1 and glioblastoma: To determine the relative contribution of HIF1α and HIF2α to glioma cell migration, U87 GBM cells were transfected with hemagglutinin-tagged HIF α-subunit constructs with or without siRNA to a HIF α-subunit and then placed under 1% or 21% oxygen saturation for 24 hours (Fig. 6).