The axis CXCR4–CXCL12 plays an important role in tumorigenicity, proliferation, metastasis, and angiogenesis in cancer [7–11], and CXCR4 expression affects prognosis in melanoma [12], colon cancer [13], lung cancer [14], renal cell carcinoma, and [15, 16] osteosarcoma [17–19]. The gene discussed is CXCR4; the disease is renal cell carcinoma.