Previous studies reported that hypoxic BMSC-derived exosomal miRNAs promote metastasis of lung cancer cells26; hypoxic cancer cell exosomal circ0048117 facilitates M2 macrophage polarization in esophageal squamous cell carcinoma27; hypoxia-induced exosomal circRNA promotes metastasis of colorectal cancer via targeting GEF-H1/RhoA axis28; hypoxia-associated circDENND2A promotes glioma aggressiveness by sponging miR-625-5p29. The gene discussed is ARHGEF2; the disease is central nervous system cancer.