Lactate Reprograms Glioblastoma Immunity through CBX3-regulated Histone Lactylation [RNA-seq]
Glioblastoma (GBM), an aggressive brain malignancy with a cellular hierarchy dominated by GBM stem cells (GSCs), evades anti-tumor immunity through mechanisms that remain incompletely understood. Like most cancers, GBMs undergo metabolic reprogramming towards glycolysis to generate lactate. Here, we show that lactate production by patient-derived GSCs and microglia induces tumor cell epigenetic reprogramming through histone lactylation, an activating modification that leads to immunosuppressive transcriptional programs and suppression of microglial phagocytosis via transcriptional upregulation of CD47, a “don't eat me” signal, in GBM cells. Leveraging these findings, pharmacologic targeting of lactate production augments efficacy of anti-CD47 therapy. Mechanistically, lactylated histone interacts with the heterochromatin component chromobox protein homolog 3 (CBX3). Although CBX3 does not possess direct lactyltransferase activity, CBX3 binds histone acetyltransferase (HAT) P300 to induce increased P300 substrate specificity toward lactyl-coA and a transcriptional shift toward an immunosuppressive cytokine profile. Targeting CBX3 inhibits tumor growth by both tumor cell-intrinsic mechanisms and increased tumor cell phagocytosis. Collectively, these results suggest that lactate mediates a metabolism-induced epigenetic reprogramming in GBM that contributes to CD47-dependent immune evasion, which can be leveraged to augment efficacy of immune-oncology therapies. Overall design: To investigate the role of lactate-regulated hsitone lactylation in GBM cells, GSC23 and CW468 were treated with 10 mM sodium lactylate for 48 hours. To reveal the role of CBX3 in GBM cells, we established CBX3 knockdown cell lines in GSC23 and CW468 by using shRNA