We had earlier reported that overexpression of cyclooxygenase-2 (COX-2) in breast cancer cells – resulting in increased prostaglandin E2 (PGE2) levels in the tumor milieu – promotes metastasis by multiple mechanisms including stimulation of tumor cell migration [29,30], invasiveness [31], tumor-associated angiogenesis [29], and lymphangiogenesis [32-34] caused by an upregulation of VEGF-C secretion via prostaglandin EP1/EP4 receptors [27,32,33]. This evidence concerns the gene PTGS2 and breast cancer.