Abstract 2186: Deciphering the regulation and function of lipid associated macrophages in immunotherapy resistance of hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is a significant global health concern, ranking as the sixth leading cause of cancer-related deaths worldwide. While immune-checkpoint blockade (ICB) has revolutionized cancer treatment, its effectiveness is limited by the immunosuppressive tumor microenvironment (TME) and the diverse etiologies of HCC, resulting in response rates below 30%. We have previously identified key transcriptional and epigenetic regulators that promote immune exclusion and myeloid-mediated immunosuppression underlying ICB resistance in preclinical models (Gut 2018, 2020, 2023, Sci Transl Med 2021). Identifying the central nodes of TME landscapes from ICB-resistant patients is instrumental for developing precise immunotherapy strategies and improving clinical outcomes. Methods: We performed single-cell RNA sequencing (scRNA-seq), single-cell Assay for Transposase-Accessible Chromatin using sequencing (scATAC-seq), and spatial transcriptomics to investigate the TME of HCC patients resistant to ICBs (NCT05873244) and treatment naïve-patients as controls. Results: Our multi-omics analysis revealed a subcluster of tumor-associated macrophages (TAMs) that express high levels of lipid-associated genes. In our syngeneic and orthotopic ICB-resistant mouse models, which recapitulate human immune-excluded HCCs, we also found a subset of lipid-associated macrophages (LAMs) is enriched in concordance with the clinical data. Bioinformatics analysis of the open chromatin regions uncovered a transcription factor (TF) that is significantly up-regulated in the TAMs in ICB-resistant HCCs compared to the treatment-naïve tumors. Moreover, chromatin immunoprecipitation-sequencing showed that this TF occupancy in THP-1 cells was enriched in phagocytosis. Conclusions: Our study provides insights into how this TF drives macrophage lipid phagocytosis to promote ICB resistance of HCC. This investigation elucidates the underlying epigenetic and transcriptional changes and identifies potential therapeutic targets for ICB resistance. Our findings may offer valuable insights into the molecular dysregulation of TAM within the immunosuppressive myeloid landscape, forming the basis for developing new strategies against the immunometabolic axis to avert ICB resistance. Acknowledgment: This study is supported by the General Research Fund (14120621 and 14119023) and the Li Ka Shing Foundation. Citation Format: Xiaohang Long, Stephen Lam Chan, Siyuan Huang, Joaquim Si Long Vong, Xiaoyu Zhan, Yalin Tu, Joseph, JY Sung, Alfred Sze Lok Cheng. Deciphering the regulation and function of lipid associated macrophages in immunotherapy resistance of hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2186.