CXCR4 and cancer: Additionally, other studies [9] emphasize the role of the bone microenvironment in which the stromal cell-derived factor (SDF)-1, a chemoattractant released by mesenchymal cells, recruits circulating cancer cells, particularly from epithelial tumors like breast and prostate cancers, bearing CXCR4 (C-X-C chemokine receptor type 4).