HIF1A and central nervous system cancer: Similarly, for Rt-glioma cells infected with a Dox-inducible Egln3 construct, the presence of 1μg/mL Dox (6hrs) up-regulated the expression of Egln3 protein and caused ≈50% decreases in Hif-2α protein levels after a 6hr exposure to hypoxic conditions without significantly altering Hif-1α expression (Figure 5B).