CXCR4 and renal cell carcinoma: Even though CXCR4 nuclear localization has been described in RCC [16], breast cancer [10], prostate cancer [15], and colon cancer [29], there are debates as to whether this localization is associated with poor prognosis [12, 29–31], and the biological function of the subcellular localization of CXCR4 is unclear.