TGFB1 and cholangiocarcinoma: In conclusion, our study elucidates a novel regulatory mechanism wherein AMDHD1 impedes the ubiquitin-mediated degradation of SMAD4 and collaboratively enhances the phosphorylation of SMAD2/3, which activates TGF-β signaling pathway and lead to the suppression of growth and metastasis in CCA cells.