In mice of breast cancer induced by the 4T1.2 breast cancer cell line which has been shown to highly metastasize to the lung, the CXCL12-CXCR7 axis mediated metastasis of breast cancer cells by activating proinflammatory STAT3 signaling and angiogenic marker vascular cell-adhesion molecule-1, accelerating breast cancer progression. Here, CXCL12 is linked to breast cancer.