HMOX1+ macrophages determine immunosuppressive microenvironment and immunotherapy efficacy in hepatocellular carcinoma.

BACKGROUND: HCC is a notably immunosuppressive malignancy with limited therapeutic options and poor prognosis. Macrophages, as major immune cell populations within the tumor microenvironment, significantly influence disease progression and therapy efficacy. We aim to identify pivotal macrophage subsets associated with HCC progression and resistance to immunotherapy. METHODS: Immunotherapy-associated macrophage-specific marker genes were identified by single-cell RNA-sequencing analysis and transcriptome analysis. The clinical relevance of macrophages with heme oxygenase 1 (HMOX1) positive was assessed in HCC patients by immunofluorescence. The immune microenvironment of HCC and the functional phenotype of HMOX1+ macrophages were explored using cytometry by time-of-flight (CyTOF). RESULTS: Single-cell RNA-sequencing analyses revealed that HMOX1 was predominantly expressed in intratumoral macrophages within the HCC microenvironment. Intratumoral HMOX1+ macrophages abundance was associated with worse prognosis and immunotherapy efficacy in patients with HCC. CyTOF analysis showed that the HCC microenvironment with high infiltration of HMOX1+ macrophages was characterized by high infiltration of CD4+ regulatory T cells (Tregs) and high expression of programmed death-1 (PD-1) in CD8+ T cells. Besides, HMOX1+ macrophages exhibited an immunosuppressive functional state. Pharmacological inhibition of HMOX1 by Znpp enhanced the therapeutic efficacy of anti-PD-1 antibody in the HCC mouse model. CONCLUSIONS: Macrophage-specific HMOX1 serves as a novel biomarker for predicting the efficacy of immunotherapy, and targeting HMOX1 has the potential to enhance the efficacy of anti-PD-1 therapy in HCC patients.