IL6 and neoplasm: CAFs are activated in the tumor tissues and secrete various cytokines, such as vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF), interleukin-6 (IL-6), transforming growth factor beta (TGF-β), hepatocyte growth factor (HGF), fibroblast-secreted protein-1 (FSP-1), and stroma-derived factor-1 (SDF-1) [21].