Tumor-associated macrophage-derived lactate remodels glioblastoma immune microenvironment through regulation of NHEJ repair by KU70 lactylation

Glioblastoma (GBM) is a malignancy with a complex tumor microenvironment (TME) dominated by glioblastoma stem cells (GSCs) and infiltrated by tumor-associated macrophages (TAMs), and exhibits aberrant metabolic pathways. Lactate is a critical glycolytic metabolite that promotes tumor progression; however, the mechanisms of lactate transportation and lactylation in the tumor microenvironment (TME) of GBM remain elusive. Here, we found that the lactate metabolic signature was highly expressed in TAMs and tumor cells. Moreover, TAMs provide lactate to GSCs, promoting GSC proliferation and inducing lactylation of the non-homologous end joining (NHEJ) protein KU70 at the residue K317. TAM-derived lactate-mediated KU70 lactylation inhibits cGAS- type I interferon signaling, remodeling the immunosuppressive microenvironment through reduced cytotoxic CD8+ T cell infiltration, promoting the malignant progression of GBM. Combinatorial targeting of lactate transport and immune checkpoints demonstrated additive therapeutic benefit in immunocompetent orthotopic xenograft models. This study unveils TAM-derived lactate and lactylation as a critical regulator of NHEJ and create immunosuppressive microenvironment, linking the TME to DNA damage response in GBM and opening novel avenues for developing combinatorial therapy for GBM. Comparative gene expression profiling analysis of RNA-seq data for MES28 cell and its KD and rescued derivatives (shMCT1/shKU70/KU70-WT/KU70-MU).