Moreover, FUS which was able to help back-splicing process of circEZH2 could be upregulated transcriptionally via KLF5 thus leading to FUS/circEZH2/KLF5/CXCR4 positive feedback loop, which potentially serving as a biomarker for BC metastasis and a target for biological BC therapy. This evidence concerns the gene CXCR4 and breast cancer.