When studied in non-immune experimental systems, PGE2 and TGF-β commonly displayed antagonism, as illustrated by PGE2 inhibition of TGF-β-induced collagen synthesis in lung fibroblasts, epithelial–mesenchymal transition in breast cancer or TGF-β-induced differentiation of myofibroblasts (26–28, 80). This evidence concerns the gene TGFB1 and breast cancer.