Strikingly, Priceet al. 25 used real-timein vivo microscopy of bone marrow in a breast cancer xenograft model to show that the CXCL2/CXCR4 interaction tethers BCCs to the bone marrow microenvironment and that CXCR4 inhibition releases micrometastasis into the circulation, therefore preventing metastatic progression. Here, CXCR4 is linked to breast carcinoma.