Abstract 2880: Inhibition of HDAC6 and HDAC11 has opposite effects on inflammation and the modulation of the functional phenotype of macrophages in the tumor microenvironment
Authors: Suresh Manasa , Coulibaly Hawa , Li Xintang , Quiceno-Torres David , Gajendran Nithya , Tan Karen , Hepp Matias , Musunuri Karthik , Noonepalle Satish , Villagra Alejandro 
Published: April 2023

Abstract
Introduction: Pan-histone deacetylase (HDAC) inhibitors have been used as anti-cancer agents due to their cytotoxicity. However, studies from our group have reported that intervention of class-specific HDAC inhibitors can differentially affect immune-related pathways in macrophages and influence their pro- or anti-inflammatory phenotype and function. For example, specific HDAC6 inhibitors demonstrated promising anti-tumor effects by suppressing tumor-promoting M2 macrophages in the tumor microenvironment (TME). In contrast, inhibition of HDAC11 promoted the anti-inflammatory phenotype of macrophages. Besides the divergent roles and distinct signaling pathways, a comprehensive study on the effect of HDCA6 and HDAC11 inhibition on macrophage phenotype and the implications on TME and inflammation is warranted.
Objective: To determine the effect of HDAC6 and HDAC11 inhibition on the phenotype and function of macrophages in the context of the TME.
Methods: Bone marrow-derived macrophages (BMDMs) isolated from C57BL/6 mice were pre-treated with HDAC6 (NexturastatA) or HDAC11 (FT895) inhibitors prior to polarizing them to M1 and M2 phenotypes. Similarly, BMDMs were isolated from total knockouts (KO) of HDAC6 and HDAC11 mice. The changes in gene expression were identified by RNA-seq analysis. Furthermore, single-cell secretome analysis on Isoplexis platform was performed from human and mice BMDMs on a panel of cytokines and chemokines.
Results: Transcriptomic analysis revealed that HDAC6 inhibition in M1 polarized BMDMs sustained inflammatory gene signature while suppressing the tumor-promoting and anti-inflammatory genes in M2 macrophages. This supported our previous reports where HDAC6i increased M1/M2 ratio in murine melanoma models. In contrast, HDAC11 inhibition in M2 macrophages upregulated classical M2 markers, whereas M1-associated gene signature was minimally affected. These results were recapitulated in HDAC6KO and HDAC11KO macrophages, suggesting a high specificity of the inhibitors. Further validation at protein level by single-cell secretome analysis indicated that HDAC11 inhibition in M2 polarized BMDMs increased secretion of growth factors such as Egf and Pdgf and of anti-inflammatory cytokines such as Il10 and Il13. On the contrary, HDAC6 inhibition upregulated inflammatory cytokines such as Ifng and Tnf and T-cell recruiting chemokine Cxcl10 in the M1 phenotype.
Conclusions:Transcriptomics and single-cell secretome analyses of macrophages indicate that HDAC6 and HDAC11 affects macrophage function in diametrically opposite directions. Therefore, our study underscores the importance of class-selective inhibition of HDACs over pan-HDAC inhibitors and the potential use of selective HDAC inhibitors as a therapeutic option to control macrophage phenotype in cancer and other conditions.
Citation Format: Manasa Suresh, Hawa Coulibaly, Xintang Li, David Quiceno-Torres, Nithya Gajendran, Karen Tan, Matias Hepp, Karthik Musunuri, Satish Noonepalle, Alejandro Villagra. Inhibition of HDAC6 and HDAC11 has opposite effects on inflammation and the modulation of the functional phenotype of macrophages in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2880.