Blocking immunosuppressive neutrophils deters pY696-EZH2-driven brain metastases

In brain metastatic cells, enhancer of zeste homologue 2 (EZH2) is highly expressed and phosphorylated at tyrosine-696 (pY696-EZH2) by nuclear-localized Src tyrosine kinase. Phosphorylation of EZH2 at Y696 changes its binding preference from histone H3 to RNA polymerase II, which consequently switches EZH2’s function from a methyltransferase to a transcription factor that increases c-Jun expression. c-Jun upregulates pro-tumorigenic inflammatory cytokines, including granulocyte-colony stimulating factor (G-CSF), which recruits Arg1-positive and PD-L1-positive immunosuppressive neutrophils into the brain to drive metastasis outgrowth. We examined Pol II binding in samples with differential EZH2 activity (wild-type EZH2, EZH2 knockout, and re-expression of mutant EZH2) using ChIPseq.