CXCR4 and cancer: CXCL12/CXCR4 axis is involved in tumor development favoring adaptation, survival and proliferation of cancer cells and CSCs in the tumor environment (Scotton et al., 2002; Zhou et al., 2002; Marchesi et al., 2004) and increasing dissemination of CXCR4-expressing tumor cells in response to CXCL12 gradients (Zlotnik et al., 2011) as CXCL12 is markedly expressed in most common sites of metastasis (liver, brain and bone).