Under such conditions, CXCL12- and CXCR4-mediated signaling elevated a large number of pro-cancerous characteristics and functions in breast cancer: tumor cell proliferation and invasion, generation of CSCs and angiogenesis (through attraction of endothelial progenitor cells), as well as tumor growth and metastasis in vivo (86, 176–180). Here, CXCR4 is linked to breast cancer.