HGF and carcinoma: Tissue-resident fibroblasts in distinct carcinomas are recruited and activated through the stimulation of different modulators [34], including transforming growth factor (TGF)-β [35], hepatocyte growth factor (HGF) [36], platelet-derived growth factor (PDGF) [37], fibroblast growth factor 2 (FGF-2) [37], stromal-derived factor-1 (SDF-1) [38] and reactive oxygen species (ROS) [39, 40].