Abstract 6041: Targeting the NuRD component, CHD4, impairs Foxp3+ Treg cell production and function and promotes anti-tumor immunity

Abstract Chromatin remodeling enzymes, which reposition nucleosomes throughout the genome to regulate transcription and other processes, include 4 families: chromodomain helicase DNA-binding (CHD), switch/sucrose non-fermentable (SWI/SNF), imitation switch (ISWI), and inositol requiring 80 (INO80). CHD4, a ubiquitous and abundant chromatin remodeling enzyme essential for normal development across a range of tissues, and that is overexpressed in various cancers, is a core member of the nucleosome remodeling and deacetylase (NuRD) complex. Though originally described as a transcriptional repressor, the NuRD complex is now regarded as able to ‘fine-tune’ gene expression, acting as both an activator and a repressor of transcription. CHD4 is important to the development of lymphocytes but has not been studied in the context of Foxp3+ T-regulatory (Treg) cells. Our work involved genetic deletion of Foxp3 in Treg cells and use of a pharmacologic inhibitor of CHD4 (CHD4i) in studies with WT mice. In basic studies, Foxp3 co-immunoprecipitated with CHD4 and deletion of CHD4 led to decreased Foxp3+ Treg production in the thymus. In the periphery, CHD4-/- Tregs showed decreased Foxp3 expression and suppressive function in vitro and in vivo, with resultant severe autoimmunity and death by 3 weeks of life. These events were associated with an absence of CNS2 demethylation in the Foxp3 locus and hierarchical clustering map for differentially expressed genes included cytokines and chemokines, leukocyte antigens, transcription factors and genes associated with apoptosis, as well as enrichment of genes associated with regulation of the cell cycle and DNA damage and repair. Thereafter, a DEL screen involving cell target engagement led to discovery of a compound CH41, binding to the CHD4 chromodomain. CH41 impaired Treg suppressive function in vitro and when used in syngeneic tumor models led to inhibition of tumor growth in lung and liver carcinoma models but was ineffective in immunodeficient mice. Efficacy was associated with increased CD4 (IL-2) and CD8 (IFN-g) infiltration and effector cytokine production. Importantly, neither WT tumor bearing mice nor their immunodeficient partners developed evidence of autoimmunity under CHD4i therapy, consistent with our previous data that tumor-associated Tregs have distinctive properties rendering them especially susceptible to immunotherapy versus their peripheral counterparts. We conclude that CHD4 targeting has interesting immunologic effects that include preferentially inhibiting Treg vs. conventional T cell responses, leading to significantly increased anti-tumor immunity. Citation Format: Wayne W. Hancock, Yan Xiong, Liqing Wang, Martina Minisini, Fanhua Kong, Eros di Giorgio, Tatiana Akimova, Ivan Babic, Elmar Nurmemmedov. Targeting the NuRD component, CHD4, impairs Foxp3+ Treg cell production and function and promotes anti-tumor immunity [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 6041.