HIF1A and glioblastoma: Importantly, the findings presented herein establish that BIRC3 is a mediator of hypoxia-mediated survival adaptation in GBM, where: (i) hypoxia induces BIRC3 in a HIF-1α-dependent fashion; (ii) hypoxic regions of GBM xenografts have overlapping expression of HIF-1α and BIRC3; (iii) BIRC3 is a direct transcription target of HIF-1α; and (iv) BIRC3 contributes to hypoxia-mediated resistance to RT though mechanisms involving inhibition of caspase activation.