We implanted these cells into mouse brains and found that the tumour volumes and weights of the HIF1α-ko or HIF2α-ko individually group were lower than those in the empty vector control group, but the tumour volumes of the dual HIF1α and HIF2α knockout group were significantly large, with the largest tumour weight and shortest survival time among all the groups (Fig. 3A–E). This evidence concerns the gene EPAS1 and neoplasm.