PTGS2 and breast carcinoma: In a preclinical tumor model using 4T1 mammary carcinoma cells, EP2-deficient mice showed decreased tumor growth and MDSC infiltration; similarly, wild-type mice treated with COX2 inhibitor showed reduced primary tumor growth and delayed MDSC accumulation.22 In cancer therapy, EP receptor antagonists and COX2 inhibitors may attenuate the accumulation of MDSCs and their contribution in tumor growth.