CXCR4 and central nervous system cancer: We found that circFGFR1 regulates CXCR4 expression in glioma cells through sponging to hsa-miR-224-5p, which is hsa-miR-381-3p in NSCLC cell according to Zhang et al.'s work [17], further reflecting the cell or tissue-specific interaction between circRNAs and miRNAs.