TGFβ-induced circLTBP2 predicts a poor prognosis in intrahepatic cholangiocarcinoma and mediates gemcitabine resistance by sponging miR-338-3p

•CircLTBP2 is induced by TGFβ in CCA cells, and its expression in CCA tumour tissues predicts a poor prognosis.•CircLTBP2 could serve as a diagnostic biomarker differentiating iCCA from HCC.•CircLTBP2 promotes cell proliferation, migration, and resistance to gemcitabine-mediated apoptosis.•CircLTBP2 exerts pro-tumoural actions by sponging miR-338-3p.•CircLTBP2 is detected in liquid biopsies and predicts a poor prognosis.