FMO2+cancer-associated fibroblasts sensitize anti-PD-1 therapy in patients with hepatocellular carcinoma

Background The efficacy of immune checkpoint inhibitors (ICIs) for hepatocellular carcinoma (HCC) is limited by heterogeneity in individual responses to therapy. The heterogeneous phenotypes and crucial roles of cancer-associated fibroblasts (CAFs) in immunotherapy resistance remain largely unclear. Methods A specific CAF subset was identified by integrating comprehensive single-cell RNA sequencing, spatial transcriptomics and transcriptome profiling of patients with HCC with different responses to antiprogrammed cell death protein 1 (anti-PD-1) therapy. Mouse orthotopic HCC models and a coculture system were constructed, and cytometry by time-of-flight analysis was performed to investigate the functions and mechanisms of specific CAFs in the immune context of HCC. Results We identified a distinct flavin-containing monooxygenase 2 (FMO2) + CAF subset associated with a favorable response to anti-PD-1 therapy and better clinical outcomes. FMO2 + CAFs increase anti-PD-1 treatment efficacy by promoting tertiary lymphoid structure formation and increasing the infiltration of CD8 + T cells and M1-like macrophages through the C-C motif chemokine ligand 19 (CCL19)-C-C motif chemokine receptor 7 axis. Mechanistically, FMO2 promotes nuclear factor kappa B/p65-mediated CCL19 expression by competitively binding to glycogen synthase 1 (GYS1) with praja ring finger ubiquitin ligase 1 (PJA1), thereby suppressing the PJA1-mediated proteasomal degradation of GYS1. CCL19 treatment potentiated the therapeutic efficacy of anti-PD-1 therapy in mouse orthotopic HCC models. A favorable immunotherapy response was observed in patients with HCC with high serum levels of CCL19. Conclusions We identified a novel FMO2 + CAF subset that serves as a critical regulator of microenvironmental immune properties and a predictive biomarker of the immunotherapy response in patients with HCC. CCL19 in combination with anti-PD-1 therapy may constitute a novel therapeutic strategy for HCC.