HIF1A and glioblastoma: To determine whether HIF is required for hypoxia-induced GPT2 expression in GBM cells, we performed qRT-PCR in parental, HIF-1α KO, HIF-2α KO, HIF-1α, and HIF-2α DKO U251MG cells exposed to 20% or 1% O2 for 24 h.