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Selective inhibition of EZH2 by a small molecule inhibitor regulates microglia gene expression essential for inflammation

ABSTRACT: Impressive studies have been well documented that Enhancer of zeste homolog 2 (EZH2) could have a role in inflammation as well as a wide range of malignancies; however, the underlying mechanisms remain largely unaddressed. Microglial activation is a key process in the production and release of numerous pro-inflammatory mediators that plays an important role in central nervous system (CNS) inflammation and neurodegeneration. Therefore, our aim was to investigate whether inhibition of EZH2 with selective small molecule inhibitors EPZ-6438 protects against neonatal microglia activation. First, we find that BV-2 microglia, LPS can rapidly increase EZH2 mRNA level and subsequently we performed gene expression profiles and networks in resting, EPZ-6438, LPS and LPS+EPZ-6438 challenged BV-2 microglia by transcriptome RNA sequencing and bioinformatic analyses. By examining RNA sequencing we identified EPZ-6438 target genes and co-regulated modules that were critical in inflammation. We also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and the transcription of key inflammatory mediators. Furthermore, we showed that EPZ-6438 controls important inflammatory genes targets by modulating interferon regulatory factor (IRF) 1, IRF8, Signal transducer and activator of transcription (STAT) 1 levels at their promoter site. Our unprecedented findings demonstrate that pharmacological interventions built upon EZH2 inhibition by EPZ-6438 could be a useful therapeutic application in neuroinflammatory diseases associated with microglia activation.

ORGANISM(S): Mus musculus

PROVIDER: GSE94144 | GEO | 2017/06/02

SECONDARY ACCESSION(S): PRJNA369082

REPOSITORIES: GEO

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Project description:Mutations within the catalytic domain of the histone methyltransferase (HMT) EZH2 have been identified in subsets of Non-Hodgkin Lymphoma (NHL) patients. These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We previously reported the discovery of a potent, selective, S-adenosyl-methionine-competitive and orally bioavailable small molecule inhibitor of EZH2, EPZ-6438. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration- and time-dependent manner in both EZH2 wild type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) led to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of xenograft-bearing mice with EPZ-6438 leads to dose-dependent tumor growth inhibition and eradication of genetically altered NHL with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 day after stopping compound treatment in two EZH2 mutant xenograft models. These data confirm the dependency of mutant NHL on EZH2 activity and portend the utility of EZH2-targeted drugs for the treatment of these genetically defined cancers. To identify potential biomarker and gain mechanistic insights in EPZ6438 treated lymphoma, lymphoma cell lines with or without EZH2 Y641 mutation were treated with EPZ6438 at Lowest Cytotoxic Concentration (LCC) and 10xLCC. Transcriptomes were profiled on Affemetrix U133 Plus2 chips. Differentially expressed genes and pathways upon compound treatment were anayzed. Lymphoma cell lines WSU-DLCL2, SU-DHL6, Pfeiffer, and Karpas422 were treated by EPZ6438 for 2 days, 4 days and 6 days. Treatment doses are LCC and 10xLCC of each cell lines. KARPAS_422, SUDHL6, and WSU_DLCL2 have the EZH2 Y641 mutation. PFEIFFER does not have the EZH2 Y641 mutation.

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Selective inhibition of EZH2 by a small molecule inhibitor regulates microglia gene expression essential for inflammation

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