CXCR4 and neoplasm: ,11,12 Because the CXCR4/CXCL12 axis plays multiple pleiotropic roles in the progression of ovarian cancer, including stimulation of angiogenesis,13 immune suppression by the fibroblast activation protein (FAP)+ cancer-associated fibroblasts (CAFs),14 recruitment of endothelial progenitor cells,15 as well as accumulation of CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs)16 and regulatory T (Treg) cells,17 modulation of this axis impacts immune mechanisms of tumor destruction.18