CXCR4 and ovarian carcinoma: In a recent study, it was shown that PGE-2 attracts MDSC into the ascites microenvironment of ovarian cancer patients by inducing expression of functional CXCR4 in cancer-associated MDSCs, and plays a role in the production of its ligand CXCL12, thus ensuring MDSC migration (Obermajer et al., 2011).