CXCR4 and prostate cancer: The overexpression of CXCR4 or CXCL12γ, an isoform of CXCL12 found in CD44+/CD133+ prostate CSCs, suggests that one mechanism by which the CXCR4/CXCL12 axis promotes metastasis in prostate cancer is the maintenance of stemness in CSCs [148,149].