HIF1A and central nervous system cancer: Hyperosmotic inducible factor 1α (HIF1α) is a hypoxia marker that greatly influences malignant transformation and tumor metastasis.66 circDENND2A, derived from the DENND2A gene, is highly expressed in HIF1α-associated glioma cells and facilitates tumor cell aggressiveness by competitive binding to miR-625-5p.67 Further, Jiang et al. recently discovered that circRNA ARF1 (cARF1) upregulates ISL2 by sponging miR-342-3p in GSCs.