TGFB1 and cancer: Activation of the EMT process is comprehensively involved in chemoresistance through a variety of signaling pathways that induce EMT, and several of these signaling pathways have been shown to control both the intrinsic and acquired chemoresistance of GCB in different cancer types, with a majority of them described in pancreatic cancer, including overactivation of the WNT/β-catenin signaling, Notch signaling, hedgehog signaling and TGF-β signaling pathways [14,18,20].