Targeted inhibition of Nrf2 potentiates antitumor immunity and enhances the efficacy of immunotherapy in hepatocellular carcinoma.

BACKGROUND: Immune checkpoint inhibitors (ICIs) and chimeric antigen receptor T-cell (CAR-T) immunotherapies have revolutionized the treatment of hepatocellular carcinoma (HCC). However, the frequent emergence of treatment resistance significantly limits the clinical efficacy of HCC immunotherapy. The molecular mechanisms underlying therapy resistance remain poorly understood. METHODS: To delineate the immune impact of nuclear factor erythroid 2-related factor 2 (Nrf2) inhibition, we integrated allograft tumor models with bulk and single-cell RNA sequencing analyses. Biochemical assays were performed to investigate the mechanisms underlying Nrf2 inhibition in immune resistance. The combined activity of Nrf2 inhibition with anti-programmed death-1 (PD-1) antibody and CAR-T cell therapy was also explored in vivo. RESULTS: We show that brusatol (BRU), a specific inhibitor of Nrf2, an emerging regulator of the tumor immune microenvironment, potentiates antitumor immunity in HCC mouse models. Mechanistically, inhibition of Nrf2 downregulates surface programmed death ligand-1 (PD-L1) expression via transcriptional repression in tumor cells, while upregulating major histocompatibility complex (MHC)-I expression via nuclear factor kappa-light-chain-enhancer of activated B cells activation. Inhibition of Nrf2 in tumor cells enhances the activation of immune-related signaling pathways and promotes CD8(+) T-cell infiltration into tumor tissues. Furthermore, inhibition of Nrf2 with BRU significantly enhances the efficacy of PD-1 antibody and CAR-T cells against HCC in vivo, indicating that therapeutic targeting of Nrf2 in HCC cells sensitizes them to ICIs and CAR-T immunotherapies. CONCLUSIONS: Our findings offer a novel strategy to enhance HCC immunotherapy by blocking Nrf2, which has the potential to address the low response rates observed with current HCC immunotherapies.