Cancer-Associated Fibroblasts Promote Tumor Immunosuppression in Hepatocellular Carcinoma via the NNMT-ANGPTL4 Axis.

[BACKGROUND & AIMS] Cancer-associated fibroblasts (CAFs) drive immunosuppression in hepatocellular carcinoma (HCC). However, their metabolic regulation remains poorly defined. We investigated the role of nicotinamide N-methyltransferase (NNMT) in CAFs.

[APPROACH & RESULTS] High NNMT expression in CAF tissues was confirmed by western blotting and immunofluorescence staining. Primary CAFs from HCC patients, single-cell RNA-seq (GSE149614), patient-derived organoids (PDOs), and fibroblast-specific NNMT-knockout mice were integrated by metabolomic analyses. NNMT in CAFs binds EZH2 and impedes its nuclear translocation, thereby reducing H3K27me3 enrichment at the promoter of angiopoietin-like 4 (ANGPTL4) to increase ANGPTL4 secretion. Secreted ANGPTL4 engages GLUT1 in HCC cells, activating aerobic glycolysis and increasing histone H3K18la levels. This epigenetic reprogramming transcriptionally upregulates PD-L1 expression, thereby facilitating tumor immune evasion. Additionally, CAF-derived ANGPTL4 promotes angiogenesis in HCC. Therapeutically, targeting the NNMT-ANGPTL4 axis restored CD8 T-cell activity and synergized with anti-PD-L1 therapy in both patient-derived xenografts (PDXs) and fibroblast-specific NNMT-knockout murine models.

[CONCLUSION] We identified an NNMT-ANGPTL4-driven metabolic-epigenetic cascade in CAFs that induces PD-L1-mediated immune evasion, providing a therapeutic strategy to overcome resistance to immunotherapy in patients with HCC.