Liver cancer chronically exposed to palmitate acquires ferroptosis resistance via the downregulation of glutamine-driven hepcidin expression.

[BACKGROUND] Immune checkpoint blockade (ICB) has revolutionized treatment of hepatocellular carcinoma (HCC), but its efficacy remains limited. Recent studies demonstrate that resistance to ferroptosis is a significant barrier to the success of ICB.

[METHODS] Ferroptosis was assessed by measuring C11-BODIPY fluorescence and 4-hydroxynonenal (4-HNE) staining. Epigenetic regulation of hepcidin under fatty acid-rich conditions in HCC cells was investigated through chromatin immunoprecipitation and histone methylation analyses. Clinical relevance was evaluated using ICB response datasets and analyses of tumor tissues from HCC patients.

[RESULTS] We demonstrate that prolonged exposure to high palmitate concentrations induces ferroptosis resistance in HCC cells by altering glutamine availability. Mechanistically, chronic exposure to palmitate and high-fat diet-feeding reduced glutamine-derived α-KG concentrations in HCC cells, leading to a H3K27me3-mediated reduction in hepcidin and depletion of the intracellular labile iron pool, thereby promoting resistance to anti-programmed death-ligand 1 (anti-PD-L1)-induced ferroptosis. This resistance was reversed by the EZH2 inhibitor tazemetostat, which epigenetically restored hepcidin expression in both in vitro and in vivo models. Notably, tumor tissues from HCC patients exhibited high FFA levels, along with low levels of glutamine, hepcidin, and iron, which correlated with shorter overall survival. H3K27me3-mediated suppression of hepcidin was further confirmed in patient cohorts.

[CONCLUSION] Our study uncovers a previously unrecognized type of palmitate-induced metabolic reprogramming that confers resistance to ICB-induced ferroptosis on HCC, and propose a therapeutic strategy to overcome ferroptosis resistance under free fatty acid-rich conditions.