LEFTY2 and cancer: Indeed, modified fibroblasts, the so-called “cancer associated fibroblasts” (CAFs), modulate extracellular matrix degradation3 and regulate proliferation of the epithelial cancer cells within the primary tumor site, via the production of numerous growth factors and cytokines, including HGF, EGF, IGFs, IGFBPs, b-FGF and TGF-β4.