Mi-2β promotes immune evasion in melanoma by activating EZH2 methylation

Recent development of new immune checkpoint inhibitors has been particularly successfully in cancer treatment, but still the majority patients fail to benefit. Converting resistant tumors to immunotherapy sensitivity will provide a significant improvement in patient outcome. Here we identify Mi-2β as a key melanoma-intrinsic effector regulating the adaptive anti-tumor immune response. Genetically engineered mouse melanoma studies indicate that loss of Mi-2β rescued the immune response to immunotherapy in vivo. Mechanistically, ATAC-seq indicate that Mi-2β controlled the accessibility of IFN-γ-stimulated genes (ISGs). Mi-2β bound to EZH2 and promote K510 methylation of EZH2 and subsequently activate the trimethylation of H3K27 to inhibit the transcription of ISGs. Finally, we develop an Mi-2β-targeted inhibitor, Z36-MP5, which targeted inhibition of Mi-2β ATPase activity and recovered ISG transcription. Consequently, Z36-MP5 efficiently induce a response to immunotherapy in otherwise resistant melanomas. Our work provides a potential therapeutic strategy to convert immunotherapy resistant melanomas to sensitive ones. Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) indicate that Mi-2β controlled the accessibility of IFN-γ-stimulated genes (ISGs). Mi-2β bound to EZH2 and promote K510 methylation of EZH2 and subsequently activate the trimethylation of H3K27 to inhibit the transcription of ISGs.