Serum bile acids (BAs) emerge as risk factors for cancer, but their roles in colorectal cancer (CRC) remain unclear. We show that glycocholic acid (GCA), a primary BA, is elevated in the serum of CRC patients. In a mouse CRC model, GCA promotes tumor programmed death-ligand 1 (PD-L1) expression in tumors, suppressing CD8⁺ T cell-mediated antitumor immunity and facilitating tumor growth. Mechanistically, GCA inhibits the BA receptor farnesoid X receptor (FXR), a transcriptional repressor for SRY-box transcription factor 14 (SOX14). Loss of FXR repression upregulates SOX14-mediated expression of zinc finger DHHC-type palmitoyl transferase 9 (DHHC9), thereby reducing PD-L1 palmitoylation and stabilization. Silencing SOX14 or DHHC9, or activating FXR, synergizes with anti-PD-1 therapy, reducing tumor growth in GCA-treated mice. These findings uncover a mechanism that GCA remodels the tumor microenvironment to mediate CRC resistance to immunotherapy, highlighting therapeutic opportunities targeting the FXR-PD-L1 axis in CRC patients with elevated serum GCA.
Zhao et al. (Sat,) studied this question.