In this study, a positive correlation (correlation coefficient of 0.52) was shown between CXCL12 and CXCR4 (Supplementary Figure 7) Recent studies have shown that VCAM1 is aberrantly expressed in breast cancer cells and mediates prometastatic tumor-stromal interactions that are unique to lung and bone microenvironments28, 29. Here, CXCL12 is linked to breast cancer.