A The CGGA database showed that both HIF1α and HIF2α were highly expressed in GBM. B Primary GBM tissues showed high levels of HIF1α and HIF2α expression using immunohistochemistry detection. C GBM cells exposed to 21% O2 and 1% O2 for 72 h showed that there was a much higher expression of HIF1α and HIF2α in cells cultured in 1% O2 than in cells cultured in 21% O2. D, E GBM cells cultured in 21% O2 and 1% O2 demonstrated that both HIF1α and HIF2α were highly expressed in 1% O2, while there was almost no HIF1α and HIF2α expression under 21% O2 conditions. P values were determined by the independent samples t test.