Abstract 2662: Deciphering the cellular and molecular determinants of immunotherapy resistance in NASH-associated hepatocellular carcinoma by single-cell analysis

Abstract Introduction: Non-alcoholic steatohepatitis (NASH) has emerged as a prominent risk and the most rapidly increasing aetiology of hepatocellular carcinoma (HCC). Despite the effectiveness of immune checkpoint blockade (ICB), like anti-programmed cell death-ligand 1 (anti-PD-L1) antibodies, in a subset of HCC patients, NASH has been shown to impair the anti-tumor immunity in ICB-treated HCC. We aim to elucidate the mechanisms responsible for ICB resistance in NASH-HCC at single-cell resolution. Methods: Orthotopic NASH-HCC mouse models were generated by orthotopically injecting liver cancer cell line into NASH liver induced by methionine-and choline-deficient diet (MCD) or choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). Multi-color flow cytometry and single-cell RNA-sequencing (scRNA-seq) were utilized to dissect the liver and tumor immune microenvironment upon anti-PD-L1 treatment. Results: Anti-PD-L1 treatment failed to alleviate tumor burden in NASH mice, indicating that orthotopic NASH-HCC mouse models were resistant to ICB therapy. Compared to the control liver, multi-color flow cytometry demonstrated that CD11b+F4/80+CD206+M2 macrophages accumulated in NASH liver and further increased in liver and tumor upon anti-PD-L1 treatment. Tumor-infiltrating M2 macrophages exhibited the most significant and robust correlation with tumor weight among all immune cell types. Moreover, PD-1 expression on tumor-infiltrating CD8+ T cells positively correlated with tumor weight and intratumoral M2 macrophages. Furthermore, scRNA-seq analysis identified a NASH-specific tumor-infiltrating monocyte subcluster, which may differentiate into an ‘M2-like’ macrophage subtype upon anti-PD-L1 treatment as demonstrated by cell trajectory analysis. Conclusion: Our study provides insights into the significance of monocyte/macrophage reprogramming in ICB resistance in NASH-HCC. Further investigation is conducted to identify the molecular mechanisms during monocyte-macrophage differentiation and explore potential targeted strategies to overcome ICB resistance in NASH-HCC. Acknowledgment: This study is supported by the General Research Fund (14120621 and 14119023), the Collaborative Research Fund (C4045-18W), the Li Ka Shing Foundation and CUHK Strategic Seed Funding for Collaborative Research Scheme. Keywords: hepatocellular carcinoma, single-cell RNA-sequencing, anti-PD-L1, macrophages. Citation Format: Lingyun Zhang, Yiling Zhang, Wenshu Tang, Zhewen Xiong, Xiaoyu Liu, Zhixian Liang, Yuk Wah Tsang, Weiqin Yang, Xiaohang Long, Alfred Sze Lok Cheng. Deciphering the cellular and molecular determinants of immunotherapy resistance in NASH-associated hepatocellular carcinoma by single-cell analysis abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2662.