HDAC2-SP1 orchestrated M2-like macrophage phenotype drives lung cancer growth – novel intervention strategy

Tumor-associated macrophages (TAMs), including anti-tumor M1-like TAMs and pro-tumor M2-like TAMs, are transcriptionally dynamic innate immune cells with diverse roles in lung cancer development. Epigenetic regulators are key controllers of macrophage fate in the spatially heterogeneous tumor microenvironment. Here, we demonstrate that the spatial proximity of histone deacetylase 2 (HDAC2) – overexpressing M2-like macrophages to tumor cells significantly correlates with poor overall survival of lung cancer patients. Suppression of HDAC2 in TAMs altered macrophage polarization, migration, and associated signaling pathways related to interleukin, chemokine, cytokine, and T cell activation. In various co-culture systems of TAMs and cancer cells, suppressing HDAC2 in TAMs results in reduced proliferation and migration and increased apoptosis of cancer cell lines and primary lung cancer cells, as well as attenuated endothelial cell tube length. HDAC2 regulates the pro-tumor macrophage phenotype via acetylation of histone H3 and transcription factor SP1. Myeloidcell–specificc deletion of Hdac2 (Hdac2f/fLysmCre) and pharmacological inhibition of class I HDACs in four different murine lung cancer models (intravenous, intratracheal, tumor relapse, and KrasLA2-driven) induced M2-like to M1-like macrophage phenotypic switching, altered infiltration of CD4 and CD8 T cells and retarded tumor growth and tumor microenvironmental angiogenesis. ThuTAM-specific HDAC2 expression may provide a novel strategy for lung cancer stratification and therapy. Overall design: To understand effect of HDAC2 inactivation in macrophages from tumor-bearing mice, LLC1 cells were intravenously injected in Hdac2fl/fl and Hdac2fl/fLysMCre mice, followed by harvesting of bone marrow at day 20 to generate bone marrow derived macrophages (BMDMs)