PPARα activation overcomes fibroinflammatory liver microenvironment-associated anti-PD-1 resistance in hepatocellular carcinoma by mediating GSDME-dependent pyroptosis.

The fibroinflammatory liver microenvironment (FILM), characterized by collagen-rich stroma and immunosuppressive inflammation, is prevalent in hepatocellular carcinoma (HCC) and correlates with poor response to programmed cell death protein 1 (PD-1) blockade. Here, we show that FILM suppresses gasdermin E (GSDME)-dependent pyroptosis and promotes immune suppression and anti-PD-1 resistance. Mechanistically, FILM-associated cancer-associated fibroblasts recruit and polarize macrophages toward a nitric oxide synthase 2 (NOS2)⁺ inflammatory phenotype. NOS2+ macrophage-derived nitric oxide induces SP1 S-nitrosylation, impairs SP1 binding to the peroxisome proliferator-activated receptor alpha (PPARA) promoter and transcriptionally represses PPARA in HCC cells. PPARα downregulation reduces pyruvate dehydrogenase kinase 4 (PDK4) expression, mitochondrial reactive oxygen species production, caspase-3 activation and GSDME cleavage. Conversely, ligand activation of tumor intrinsic PPARα restores the PDK4-ROS-caspase-3-GSDME axis, enhances dendritic cell and CD8⁺ T cell activation, and sensitizes HCC to anti-PD-1 therapy. The clinically approved PPARα agonist fenofibrate enhances anti-PD-1 efficacy in HCC models in male mice and is associated with improved clinical benefit in a retrospective cohort of patients with HCC. We propose a FILM-NOS2-SP1-PPARα-PDK4 axis that controls pyroptotic immunogenicity and immunotherapy response, supporting PPARα activation as a strategy to overcome FILM-associated immune resistance in HCC.