By recreating a vascularized osteo-cell conditioned microenvironment, using bone marrow derived mesenchymal stem cells (hBM-MSCs) and endothelial cells (HUVECs), the authors identified molecular pathways critical for the extravasation of breast cancer cells, involving the breast cancer cell surface receptor CXCR2 and the bone-secreted chemokine CXCL5 [46]. Here, CXCL5 is linked to breast cancer.