Cancer-associated fibroblasts (CAFs), the main resource of the tumor stroma, are normally recruited and activated persistently by cholangiocarcinoma cells, in response to the activation of stromal cell derived factor 1 (SDF1), transforming growth factor β (TGF-β) and extracellular matrix (ECM) proteins5-7. Here, TGFB1 is linked to cholangiocarcinoma.