TGFB1 and cholangiocarcinoma: Chronic inflammation of the bile duct due to the presence of liver flukes is closely associated also with the development of CCA, because it causes biliary epithelial cells to produce various cytokines and growth factors including interleukin-6, -8 (IL-6, -8), transforming growth factor-β (TGF-β), tumor necrosis factor-α (TNF-α), platelet-derived growth factor and epithelial growth factor [12].