CXC-chemokine receptor 4 (CXCR4) is the only known CXCL12 receptor, and the biological axis system formed by the two plays an important role in targeted metastasis of various malignancies including breast cancer, prostate cancer, hepatocellular carcinoma, and neuroblastoma [44, 45]. The gene discussed is CXCR4; the disease is prostate carcinoma.