Abstract
Loss of MHC class I (MHC-I) antigen presentation in cancer cells can elicit immunotherapy resistance. A genome-wide CRISPR/Cas9 screen identified an evolutionarily conserved function of polycomb repressive complex 2 (PRC2) that mediates coordinated transcriptional silencing of the MHC-I antigen processing pathway (MHC-I APP), promoting evasion of T cell-mediated immunity. MHC-I APP gene promoters in MHC-I low cancers harbor bivalent activating H3K4me3 and repressive H3K27me3 histone modifications, silencing basal MHC-I expression and restricting cytokine-induced upregulation. Bivalent chromatin at MHC-I APP genes is a normal developmental process active in embryonic stem cells and maintained during neural progenitor differentiation. This physiological MHC-I silencing highlights a conserved mechanism by which cancers arising from these primitive tissues exploit PRC2 activity to enable immune evasion.
Keywords:
EZH2; MHC class I; antigen presentation; bivalency; cancer; epigenetic repression; histone methyltransferase; immune evasion; immunotherapy; polycomb.
Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antigen Presentation / drug effects
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Antigen Presentation / immunology
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Antineoplastic Agents, Immunological / pharmacology
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Antineoplastic Agents, Immunological / therapeutic use
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Antineoplastic Combined Chemotherapy Protocols / pharmacology*
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Antineoplastic Combined Chemotherapy Protocols / therapeutic use
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Cell Line, Tumor
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DNA Methylation / immunology
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Down-Regulation / drug effects
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Down-Regulation / genetics
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Down-Regulation / immunology
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Drug Resistance, Neoplasm / genetics
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Epigenetic Repression / drug effects
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Epigenetic Repression / immunology
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Female
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Gene Expression Regulation, Neoplastic / drug effects
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Gene Expression Regulation, Neoplastic / immunology*
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Histocompatibility Antigens Class I / genetics*
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Histocompatibility Antigens Class I / immunology
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Histocompatibility Antigens Class I / metabolism
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Histone Code / drug effects
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Humans
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Mice
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Middle Aged
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Neoplasms / drug therapy
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Neoplasms / genetics
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Neoplasms / immunology*
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Neoplasms / pathology
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Polycomb Repressive Complex 2 / antagonists & inhibitors
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Polycomb Repressive Complex 2 / metabolism*
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T-Lymphocytes / immunology
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Tumor Escape / drug effects
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Tumor Escape / genetics*
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Xenograft Model Antitumor Assays
Substances
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Antineoplastic Agents, Immunological
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Histocompatibility Antigens Class I
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Polycomb Repressive Complex 2