CXCR4 and neoplasm: According to the results, they successfully realize monitoring the process of chemokine scavenging by CXCR7 through dual luciferase imaging and quantify the effect of CXCR7 on tumor growth and metastasis of CXCR4-expressing breast cancer cells, which provides a useful imaging method for quantification the role of tumor chemokines and evaluation of tumor development.