CXCR4 and cancer: Taken together, our results demonstrate that circFGFR1 expression is upregulated in glioma cells, and the elevated circFGFR1 level is responsible for the exasperating malignant behaviors in glioma cells, including invasion, migration, and proliferation, via increasing CXCR4 level, a critical oncogene in several cancers, by sponging to hsa-miR-224-5p.