Epigenetic pattern after EZH1,2 inhibition in lymohoma cells

Although global H3K27me3 reprogramming is a hallmark of cancer, no effective therapeutic strategy for H3K27me3-high malignancies harboring EZH2WT/WT has yet been established. We explored epigenome and transcriptome in EZH2WT/WT aggressive lymphomas, and found that mutual interference and compensatory function of co-expressed EZH1 and EZH2 rearrange their own genome-wide distribution, thereby establishing restricted chromatin and gene expression signatures. Direct comparison of leading compounds introduced potency and a mechanism-of-action of the EZH1/2 dual-inhibitor (valemetostat). The synthetic lethality was observed in all lymphoma models and primary adult T-cell leukemia–lymphoma (ATL) cells. Opposing actions of EZH1/2-polycomb and SWI/SNF complexes are required for facultative heterochromatin formation. Inactivation of chromatin-associated genes (ARID1A, SMARCA4/BRG1, SMARCB1/SNF5, KDM6A/UTX, BAP1, KMT2D/MLL2) and oncovirus infection (HTLV-1, EBV) trigger EZH1/2 perturbation and H3K27me3 deposition. Our study provides the mechanism-based rationale for chemical dual-targeting of EZH1/2 in cancer epigenome. We explored epigenome (EZH1/2 occupancies and histone modifications) in aggressive lymphoma samples and cell lines treated with EZH1/2 inhibitors by using ChIP-on-chip platform