IDH1 and central nervous system cancer: We determined HIF‐1α levels in an immortalized human astrocyte (IHA) cell line where expression of IDHmut mimicked the glioma CpG island methylator phenotype (G‐CIMP) observed in most IDH mutant gliomas.[10] Hypoxia rapidly increased the level of HIF‐1α, which reached a peak at 24 h (Figure 1D).