PTGS2 and breast carcinoma: Indeed, blocking COX-2 activity using a potent, selective pharmacological inhibitor, celecoxib inhibited TGFβ mediated tumorigenesis and enrichment of the primary breast cancer stem cells, CD24lowCD44high and ALDH+ populations.62 In agreement with our PPI network and gene expression profiles findings, the gene expression and functional analyses of the disseminated breast cancer cells identified the PTGS2 and EGFR ligands as mediators of extravasation that enhance the invasion of breast cancer cells into the lung and the brain tissues through crossing the blood-brain barriers.65