Abstract 1424: Epigenetic activation of tumoral IFNγresponse and pyroptosis overcomes immunotherapy resistance in hepatocellular carcinoma

Abstract Background: Immune checkpoint blockade (ICB) therapies by antibodies have revolutionized the treatment paradigm for a variety of cancers. Although subsets of people exhibit durable responses, resistance and relapse are common in hepatocellular carcinoma (HCC). We therefore aim to delineate the mechanism underlying the failure of ICB therapy in HCC, and more importantly to identify ICB-sensitizing therapeutic approaches. Methods: ICB-resistant orthotopic-grafted murine models were established via a serial selection of HCC cells in ICB-treated mice. Integrated multi-omics analysis (single-cell RNA-seq, single-cell ATAC-seq and ChIP-seq) were applied to decode the mechanisms underlying the ICB resistance and an epigenetic-mediated ICB response. Results: We successfully established the ICB-resistant murine models of HCC, in which tumor intrinsic interferon-gamma (IFNγ) response was most significantly suppressed and characterized by a “cold” tumor microenvironment with decreased lymphocyte activation and intratumoral infiltration. On the other hand, single cell RNA-seq analysis of human HCC biopsies revealed that patients with HDAC1/2/3-high HCC exhibit poor survival upon ICB therapy. Notably, we found that a novel specific HDAC1/2/3 inhibitor CXD101 synergized with PD- (L) 1 antibody to induce immunogenic cell death, eradicate tumor and prolong survival in our ICB-resistant mouse models, which was accompanied by enhanced intratumoral infiltration, activation and anti-tumor memory formation of cytotoxic lymphocytes. Mechanistically, CXD101 combined with PD- (L) 1 inhibition synergistically reactivated tumor IFNγ pathway via enhancing chromatin accessibility of downstream genes associated with antigen presentation and lymphocytes recruitment. Moreover, the activated immune system induced tumor cell pyroptosis, further igniting antitumor immunity and ICB response. Conclusions: Our findings suggest that corruption of tumor intrinsic IFNγ signaling may confer ICB resistance upon ICB therapy, which can be rectified by class I HDAC inhibitor mediated IFNγ response and tumor cell pyroptosis. Based on these findings, we have commenced a Phase II clinical study of a new epigenetic immunotherapy (CXD101 plus anti-PD-1) for HCC patients resisting anti-PD- (L) 1 alone. This project is supported by the CRF (C4045-18W), GRF (14115820), TRS (T11-706/18-N), Li Ka Shing Foundation, CUHK Strategic Seed Funding for Collaborative Research Scheme. We also acknowledge support (funding and study medications) by Celleron Therapeutics. Citation Format: Yalin Tu, Haoran Wu, Chengpeng Zhong, Zhewen Xiong, Jing Wang, Patrick Pak-Chun Wong, Weiqin Yang, Jiahuan Lu, Zhixian Liang, Shufen Chen, Lingyun Zhang, Siyun Chen, Jingying Zhou, Ka-Fai To, Joseph Jao-Yiu Sung, Stephen Lam Chan, David Kerr, Nick La Thangue, Alfred Sze-Lok Cheng. Epigenetic activation of tumoral IFNγresponse and pyroptosis overcomes immunotherapy resistance in hepatocellular carcinoma 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 1424.