Potentiating BSEP-mediated bile acid efflux reverses first-line tyrosine kinase inhibitor resistance in hepatocellular carcinoma.

Tyrosine kinase inhibitor (TKI) resistance limits therapy for hepatocellular carcinoma (HCC). Integrating RNA-seq and public cohort data, we found consistent downregulation of the bile salt export pump (BSEP/ABCB11) in TKI-resistant HCC associated with poorer prognosis and reduced clinical response. Functional in vitro and xenograft studies, using BSEP overexpression/knockdown and TKI-resistant cell lines plus targeted metabolomics, showed BSEP expression deficiency leads to intracellular accumulation of primary conjugated bile acids (BAs)-especially glycocholic acid (GCA)-which activates EGFR signaling and drives resistance; restoring BSEP enhances BA efflux and resensitizes cells and tumors to TKIs. Mechanistic assays revealed that ursodeoxycholic acid (UDCA) upregulated BSEP and reversed resistance via an FXR-independent mechanism: UDCA directly binds cortactin (CTTN), reduces its PRMT1-dependent mono-methylation, and promotes CTTN degradation via chaperone-mediated autophagy (CMA), thereby enabling YY1 nuclear translocation and transcriptional activation of BSEP. Clinical specimen analyses corroborated an inverse BSEP-CTTN relationship and UDCA modulation. These findings identify impaired BSEP-mediated BA efflux and GCA accumulation as metabolic features of TKI resistance and support targeting the CTTN/YY1/BSEP axis, including UDCA, to overcome resistance.