CXCR4 and ovarian cancer: Because the CXCL12/CXCR4 axis plays multiple pleiotropic roles in the progression of ovarian cancer, including stimulation of vascular endothelial growth factor (VEGF)-mediated angiogenesis,16 intratumoral recruitment of endothelial progenitor cells,17 as well as accumulation of CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs)18 and T regulatory cells (Tregs),19 modulation of this axis affects innate and adaptive immune mechanisms of tumor destruction by increasing T lymphocyte infiltration as well as recently reported responses to checkpoint blockers.20