GSE192714
Enhancer decommissioning by MLL4 ablation elicits dsRNA-interferon signaling and GSDMD-mediated pyroptosis to potentiate anti-tumor immunity
Transcriptional enhancers instruct spatiotemporal gene expression and their dysfunction has long been known as one of the primary mechanisms that drive tumorigenesis and confer malignant tumor cell behaviors. However, it is largely unknown about whether tumor cell enhancer regulation plays a role in tumor immune evasion and anti-tumor immune response. Here, we demonstrate that tumor cell deletion of Mll3 and Mll4, two members of COMPASS family for enhancer H3K4 mono-methylation, increases tumor cell immunogenicity and promotes anti-tumor immune response. Loss of Mll4 potentiates therapeutic response to anti-Pd1 blockade in the murine melanoma model. Mechanistically, Mll4 loss leads to the widespread decrease of epigenetic signatures at both typical and super-enhancers, including the super-enhancer for Ago2 subunit of RNA-induced silencing complex (RISC) and the enhancers for DNA methyltransferases Dnmt3a and Dnmt1. Downregulation of Ago2 expression leads to double-stranded RNA (dsRNAs) stress to elicit interferon response while decreased expression of Dnmt3a and Dnmt1 derepresses Gsdmd and inflammatory caspases to trigger Gsdmd-mediated pyroptosis in Mll4-deficient tumor cells. Notably, transcriptional induction of interferon signaling and Gsdmd-mediated tumor cell pyroptotic death is crucial for the increased anti-tumor immunity and the improved immunotherapeutic efficacy in Mll4-deficient tumors. These findings reveal an important immune regulatory role of tumor cell enhancer regulation and provide molecular insights into the immunotherapeutic vulnerabilities of tumors bearing MLL3/MLL4 deficiency or loss of function mutations. Overall design: RNA-seq of wild-type, Mll4-knockout or Mll3-knockout B16-F10 cells. ChIP-seq of H3K27 acetylation or H3K4 monomethylation for wild-type or Mll4-knockout B16-F10 cells.