Six Years (2012-2018) of Researches on Catalytic EZH2 Inhibitors: The Boom of the 2-Pyridone Compounds

EZH2-associated tumor malignancy: A prominent target for cancer treatment

The discussion in this review centers around the significant relationships between EZH2 and the initiation, progression, metastasis, metabolism, drug resistance, and immune regulation of cancer. Polycomb group (PcG) proteins, which encompass two primary Polycomb repressor complexes (PRC1 and PRC2), have been categorized. PRC2 consists mainly of four subunits, namely EZH2, EED, SUZ12, and RbAp46/48. As the crucial catalytic component within the PRC2 complex, EZH2 plays a pivotal role in controlling a wide range of biological processes. Overexpression/mutations of EZH2 have been detected in a wide variety of tumors. Several mechanisms of EZH regulation have been identified, including regulation EZH2 mRNA by miRNAs, LncRNAs, accessibility to DNA via DNA-binding proteins, post-translational modifications, and transcriptional regulation. EZH2 signaling triggers cancer progression and may intervene with anti-tumor immunity; therefore it has charmed attention as an effective therapeutic target in cancer therapy. Numerous nucleic acid-based therapies have been used in the modification of EZH2. In addition to gene therapy approaches, pharmaceutical compounds can be used to target the EZH2 signaling pathway in the treatment of cancer. EZH2-associated tumor cells and immune cells enhance the effects of the immune response in a variety of human malignancies. The combination of epigenetic modifying agents, such as anti-EZH2 compounds with immunotherapy, could potentially be efficacious even in the context of immunosuppressive tumors. Summary, understanding the mechanisms underlying resistance to EZH2 inhibitors may facilitate the development of novel drugs to prevent or treat relapse in treated patients.

Dual-target EZH2 inhibitor: latest advances in medicinal chemistry

Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, plays a crucial role in tumor progression by regulating gene expression. EZH2 inhibitors have emerged as promising anti-tumor agents due to their potential in cancer treatment strategies. However, single-target inhibitors often face limitations such as drug resistance and side effects. Dual-target inhibitors, exemplified by EZH1/2 inhibitor HH-2853(28), offer enhanced efficacy and reduced adverse effects. This review highlights recent advancements in dual inhibitors targeting EZH2 and other proteins like BRD4, PARP1, and EHMT2, emphasizing rational design, structure-activity relationships, and safety profiles, suggesting their potential in clinical applications.

A new strategy for overcoming drug resistance in liver cancer: Epigenetic regulation

Drug resistance in hepatocellular carcinoma has posed significant obstacles to effective treatment. Recent evidence indicates that, in addition to traditional gene mutations, epigenetic recoding plays a crucial role in HCC drug resistance. Unlike irreversible gene mutations, epigenetic changes are reversible, offering a promising avenue for preventing and overcoming drug resistance in liver cancer. This review focuses on various epigenetic modifications relevant to drug resistance in HCC and their underlying mechanisms. Additionally, we introduce current clinical epigenetic drugs and clinical trials of these drugs as regulators of drug resistance in other solid tumors. Although there is no clinical study to prevent the occurrence of drug resistance in liver cancer, the development of liquid biopsy and other technologies has provided a bridge to achieve this goal.

Metal-Free Cascade Formation of C-C and C-N Bond for the Construction of 3-Cyano-2-Pyridones with Insecticidal Properties

A straightforward and efficient methodology has been developed for the synthesis of 3-cyano-2-pyridones via the C-C and C-N bond formation processes. A total of 51 diverse 3-cyano-2-pyridone derivatives were obtained in moderate to excellent yields. This reaction featured advantages such as a metal-free process, wide functional group tolerance, simple operation, and mild conditions. A plausible mechanism for the reaction was proposed. 3-cyano-2-pyridones as ricinine analogues for insecticidal properties were evaluated, and the compound 3ci (LC50 = 2.206 mg/mL) showed the best insecticidal property.

Enzyme-independent role of EZH2 in regulating cell cycle progression via the SKP2-KIP/CIP pathway

While EZH2 enzymatic activity is well-known, emerging evidence suggests that EZH2 can exert functions in a methyltransferase-independent manner. In this study, we have uncovered a novel mechanism by which EZH2 positively regulates the expression of SKP2, a critical protein involved in cell cycle progression. We demonstrate that depletion of EZH2 significantly reduces SKP2 protein levels in several cell types, while treatment with EPZ-6438, an EZH2 enzymatic inhibitor, has no effect on SKP2 protein levels. Consistently, EZH2 depletion leads to cell cycle arrest, accompanied by elevated expression of CIP/KIP family proteins, including p21, p27, and p57, whereas EPZ-6438 treatment does not modulate their levels. We also provide evidence that EZH2 knockdown, but not enzymatic inhibition, suppresses SKP2 mRNA expression, underscoring the transcriptional regulation of SKP2 by EZH2 in a methyltransferase-independent manner. Supporting this, analysis of the Cancer Genome Atlas database reveals a close association between EZH2 and SKP2 expression in human malignancies. Moreover, EZH2 depletion but not enzymatic inhibition positively regulates the expression of major epithelial-mesenchymal transition (EMT) regulators, such as ZEB1 and SNAIL1, in transformed cells. Our findings shed light on a novel mechanism by which EZH2 exerts regulatory effects on cell proliferation and differentiation through its methyltransferase-independent function, specifically by modulating SKP2 expression.

EZH2: The roles in targeted therapy and mechanisms of resistance in breast cancer

Drug resistance presents a formidable challenge in the realm of breast cancer therapy. Accumulating evidence suggests that enhancer of zeste homolog 2 (EZH2), a component of the polycomb repressive complex 2 (PRC2), may serve as a key regulator in controlling drug resistance. EZH2 overexpression has been observed in breast cancer and many other malignancies, showing a strong correlation with poor outcomes. This review aims to summarize the mechanisms by which EZH2 regulates drug resistance, with a specific focus on breast cancer, in order to provide a comprehensive understanding of the underlying molecular processes. Additionally, we will discuss the current strategies and outcomes of targeting EZH2 using both single agents and combination therapies, with the goal of offering improved guidance for the clinical treatment of breast cancer patients who have developed drug resistance.

Epigenetic modification in liver fibrosis: Promising therapeutic direction with significant challenges ahead

Liver fibrosis, characterized by scar tissue formation, can ultimately result in liver failure. It's a major cause of morbidity and mortality globally, often associated with chronic liver diseases like hepatitis or alcoholic and non-alcoholic fatty liver diseases. However, current treatment options are limited, highlighting the urgent need for the development of new therapies. As a reversible regulatory mechanism, epigenetic modification is implicated in many biological processes, including liver fibrosis. Exploring the epigenetic mechanisms involved in liver fibrosis could provide valuable insights into developing new treatments for chronic liver diseases, although the current evidence is still controversial. This review provides a comprehensive summary of the regulatory mechanisms and critical targets of epigenetic modifications, including DNA methylation, histone modification, and RNA modification, in liver fibrotic diseases. The potential cooperation of different epigenetic modifications in promoting fibrogenesis was also highlighted. Finally, available agonists or inhibitors regulating these epigenetic mechanisms and their potential application in preventing liver fibrosis were discussed. In summary, elucidating specific druggable epigenetic targets and developing more selective and specific candidate medicines may represent a promising approach with bright prospects for the treatment of chronic liver diseases.

Approaching the catalytic mechanism of protein lysine methyltransferases by biochemical and simulation techniques

Protein lysine methyltransferases (PKMTs) transfer up to three methyl groups to the side chains of lysine residues in proteins and fulfill important regulatory functions by controlling protein stability, localization and protein/protein interactions. The methylation reactions are highly regulated, and aberrant methylation of proteins is associated with several types of diseases including neurologic disorders, cardiovascular diseases, and various types of cancer. This review describes novel insights into the catalytic machinery of various PKMTs achieved by the combined application of biochemical experiments and simulation approaches during the last years, focusing on clinically relevant and well-studied enzymes of this group like DOT1L, SMYD1-3, SET7/9, G9a/GLP, SETD2, SUV420H2, NSD1/2, different MLLs and EZH2. Biochemical experiments have unraveled many mechanistic features of PKMTs concerning their substrate and product specificity, processivity and the effects of somatic mutations observed in PKMTs in cancer cells. Structural data additionally provided information about the substrate recognition, enzyme-substrate complex formation, and allowed for simulations of the substrate peptide interaction and mechanism of PKMTs with atomistic resolution by molecular dynamics and hybrid quantum mechanics/molecular mechanics methods. These simulation technologies uncovered important mechanistic details of the PKMT reaction mechanism including the processes responsible for the deprotonation of the target lysine residue, essential conformational changes of the PKMT upon substrate binding, but also rationalized regulatory principles like PKMT autoinhibition. Further developments are discussed that could bring us closer to a mechanistic understanding of catalysis of this important class of enzymes in the near future. The results described here illustrate the power of the investigation of enzyme mechanisms by the combined application of biochemical experiments and simulation technologies.

The Interplay Between HIF-1α and EZH2 in Lung Cancer and Dual-Targeted Drug Therapy

Interactions between oncogenic proteins contribute to the phenotype and drug resistance. Here, EZH2 (enhancer of zest homolog 2) is identified as a crucial factor that mediates HIF-1 (hypoxia-inducible factor) inhibitor resistance. Mechanistically, targeting HIF-1 enhanced the activity of EZH2 through transcription activation of SUZ12 (suppressor of zest 12 protein homolog). Conversely, inhibiting EZH2 increased HIF-1α transcription, but not the transcription of other HIF family members. Additionally, the negative feedback regulation between EZH2 and HIF-1α is confirmed in lung cancer patient tissues and a database of cell lines. Moreover, molecular prediction showed that a newly screened dual-target compound, DYB-03, forms multiple hydrogen bonds with HIF-1α and EZH2 to effectively inhibit the activity of both targets. Subsequent studies revealed that DYB-03 could better inhibit migration, invasion, and angiogenesis of lung cancer cells and HUVECs in vitro and in vivo compared to single agent. DYB-03 showed promising antitumor activity in a xenograft tumor model by promoting apoptosis and inhibiting angiogenesis, which could be almost abolished by the deletion of HIF-1α and EZH2. Notably, DYB-03 could reverse 2-ME2 and GSK126-resistance in lung cancer. These findings clarified the molecular mechanism of cross-regulation of HIF-1α and EZH2, and the potential of DYB-03 for clinical combination target therapy.

EZH2 as a potential therapeutic target for gastrointestinal cancers

Gastrointestinal (GI) cancers continue to be a major cause of mortality and morbidity globally. Understanding the molecular pathways associated with cancer progression and severity is essential for creating effective cancer treatments. In cancer research, there is a notable emphasis on Enhancer of zeste homolog 2 (EZH2), a key player in gene expression influenced by its irregular expression and capacity to attach to promoters and alter methylation status. This review explores the impact of EZH2 signaling on various GI cancers, such as colorectal, gastric, pancreatic, hepatocellular, esophageal, and cholangiocarcinoma. The primary function of EZH2 signaling is to facilitate the accelerated progression of cancer cells. Additionally, EZH2 has the capacity to modulate the reaction of GI cancers to chemotherapy and radiotherapy. Numerous pathways, including long non-coding RNAs and microRNAs, serve as upstream regulators of EZH2 in these types of cancer. EZH2's enzymatic activity enables it to attach to target gene promoters, resulting in methylation that modifies their expression. EZH2 could be considered as an independent prognostic factor, with increased expression correlating with a worse disease prognosis. Additionally, a range of gene therapies including small interfering RNA, and anti-tumor agents are being explored to target EZH2 for cancer treatment. This comprehensive review underscores the current insights into EZH2 signaling in gastrointestinal cancers and examines the prospect of therapies targeting EZH2 to enhance patient outcomes.

Discovery of dihydropyridinone derivative as a covalent EZH2 degrader

EZH2 is overexpressed in multiple types of cancer and high expression level of EZH2 correlates with poor prognosis. Besides the regulation of H3K27 trimethylation, EZH2 itself regulates its downstream proteins in a PRC2- and methylation-independent way. Starting from an approved EZH2 inhibitor EPZ-6438, we used covalent drug design and medicinal chemistry approaches to discover a novel covalent EZH2 degrader 38, which forms a covalent bond with EZH2 Cys663 and showed strong biochemical activities against EZH2 WT and mutants. Compound 38 exhibited potent antiproliferation effects against both B-cell lymphoma and TNBC cell lines by reducing the levels of H3K27me3 and EZH2. The mass spectrometry, washout and competition experiments confirmed the covalent binding of 38 to EZH2. This study demonstrates that covalent EZH2 degraders could provide an opportunity for the development of promising new drug candidates.

Down-regulation of EZH2 genes targeting RUNX3 affects proliferation, invasion, and metastasis of human colon cancer cells by Wnt/β-catenin signaling pathway

In order to detect the effect of EZH2 genes on proliferation, migration, invasion, and apoptosis of colon carcinoma cell strains HCT116 and HT29 by the Wnt/β-catenin signaling pathway, qRT-PCR was applied to measure relative expressions of EZH2, RUNX3, CEA, CA199, MMP-9, VEGF, β-catenin, and CyclinD1 in each group; Western-blot was employed with the intention of exploring relative expressions of these proteins in vivo and in vitro; monoclonal proliferation experiments and CCK-8 assay was adopted so as to check cell proliferation; the effect on cell migration was investigated via Transwell assay and cell scratch wound assay; flow cytometry was applied with a view to determining the effect on cell apoptosis. Transfected HCT116 cells are injected subcutaneously into nude mice. In colon cell strains HCT-116 and HT29, contrasted to the si-NC group, the RUNX3 expression was prominently up-regulated in the si-EZH2 group. Besides, expressions of CEA, CA199, MMP-9, and VEGF were significantly reduced; down-regulation of EZH2 genes remarkably inhibited cell proliferation, invasion and migration when facilitating apoptosis; down-regulation of EZH2 genes also significantly reduced expressions of essential proteins β-catenin and CyclinD1 on the Wnt pathway. The subcutaneous tumor body of nude mice was reduced. EZH2-OE is the opposite trend to si-EZH2; The EZH2 gene may target regulatory RUNX3 regulation via that Wnt/β-catenin signaling pathway, hence affecting colon carcinoma cell proliferation, invasion, migration, and apoptosis. Therefore, EZH2 may become a promising target for the clinical therapy of colon carcinoma.

Regioselective [2 + 1] photocycloaddition of 2-pyridones with diazo compounds

Herein, we report a novel regioselective [2 + 1] cyclization reaction of 2-pyridones with carbenes generated in situ via visible light irradiation, without the requirement for catalysts or additives. The diverse functional groups of 2-pyridones and diazo compounds exhibit good tolerance, enabling the rapid synthesis of highly valuable cyclopropanated dihydro-2-pyridone scaffolds with exceptional regio- and stereoselectivity. Furthermore, DFT calculations provide a comprehensive explanation for the regio- and stereoselectivity observed in the reaction.

Virus-Like Nanotherapeutic for Spatiotemporally Enhancing Antigen Presentation and Cross-Presentation toward Potential Personalized Immunotherapy

One of the major causes of immunotherapy resistance is the loss of major histocompatibility complex class I (MHC-I) molecules in tumor cells or the downregulation of the class I antigen presentation pathway. In this study, a novel virus-like nanotherapeutic (siRNA@HCM) is developed via encapsulating nanosized siRNA nanoparticles in a hybrid membrane comprising a personalized tumor cell membrane and a universal 293T membrane expressing the mutant vesicular stomatitis virus glycoprotein (mVSV-G). Upon intravenous administration, siRNA@HCM accumulates at the tumor site and provides two potent driving forces for antitumor immunity. First, mVSV-G induces the fusion of siRNA@HCM with tumor cell membranes and directly injects siRNAs into the cytoplasm, significantly improving tumor intrinsic MHC-I antigen presentation. Moreover, mVSV-G can promote the maturation of dendritic cells, thereby achieving highly efficient antigen cross-presentation. The results demonstrate that spatiotemporally enhancing tumor intrinsic antigen presentation and cross-presentation via siRNA@HCM can achieve satisfactory antitumor efficacy and excellent biocompatibility. Immune infiltration analysis shows that siRNA@HCM treatment turns cold tumors into hot tumors. In addition, it significantly promotes the therapeutic effect of programmed death-1 inhibitor. In summary, virus-like nanotherapeutics present a promising approach to enhance the antitumor immune response, with distinct advantages for potential personalized therapy and clinical applications.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

EZH2 can be used as a therapeutic agent for inhibiting endothelial dysfunction

Enhancer of zeste homolog 2 (EZH2) is a catalytic subunit of polycomb repressor complex 2 and plays important roles in endothelial cell homeostasis. EZH2 functionally methylates lysine 27 of histone H3 and represses gene expression through chromatin compaction. EZH2 mediates the effects of environmental stimuli by regulating endothelial functions, such as angiogenesis, endothelial barrier integrity, inflammatory signaling, and endothelial mesenchymal transition. Numerous studies have been conducted to determine the significance of EZH2 in endothelial function. The aim of this review is to provide a concise summary of the roles EZH2 plays in endothelial function and elucidate its therapeutic potential in cardiovascular diseases.

Single Inhibitors versus Dual Inhibitors: Role of HDAC in Cancer

Due to the multimodal character of cancer, inhibition of two targets simultaneously by a single molecule is a beneficial and effective approach against cancer. Histone deacetylase (HDAC) was widely investigated as a novel category of anticancer drug targets due to its crucial role in various biological processes like cell-proliferation, metastasis, and apoptosis. Numerous HDAC inhibitors such as vorinostat and panobinostat are clinically approved but have limited usage due to their low efficacy, nonselectivity, drug resistance, and toxicity. Therefore, HDACs with a dual targeting ability have attracted great attention. The strategy of combining a HDAC inhibitor with other antitumor agents has been proved advantageous for combating the nonselectivity and drug resistivity problems associated with single-target drugs. Henceforth, we have highlighted dual-targeting inhibitors to target HDAC along with topoisomerase, receptor tyrosine kinase inhibitors, and the zeste homolog 2 enzyme. Our Review mainly focuses on the impact of the substituent effect along with the linker variation of well-known HDAC-inhibitor-conjugated anticancer drugs.

Recent advances in EZH2-based dual inhibitors in the treatment of cancers

The enhancer of zeste homolog 2 (EZH2) protein is the catalytic subunit of one of the histone methyltransferases. EZH2 catalyzes the trimethylation of lysine 27 of histone H3 (H3K27me3) and further alters downstream target levels. EZH2 is upregulated in cancer tissues, wherein its levels correlate strongly with cancer genesis, progression, metastasis, and invasion. Consequently, it has emerged as a novel anticancer therapeutic target. Nonetheless, developing EZH2 inhibitors (EZH2i) has encountered numerous difficulties, such as pre-clinical drug resistance and poor therapeutic effect. The EZH2i synergistically suppresses cancers when used in combination with additional antitumor drugs, such as PARP inhibitors, HDAC inhibitors, BRD4 inhibitors, EZH1 inhibitors, and EHMT2 inhibitors. Typically, the use of dual inhibitors of two different targets mediated by one individual molecule has been recognized as the preferred approach for overcoming the limitations of EZH2 monotherapy. The present review discusses the theoretical basis for designing EZH2-based dual-target inhibitors, and also describes some in vitro and in vivo analysis results.

High Throughput Fluorescence-Based In Vitro Experimental Platform for the Identification of Effective Therapies to Overcome Tumour Microenvironment-Mediated Drug Resistance in AML

The interactions between Acute Myeloid Leukaemia (AML) leukemic stem cells and the bone marrow (BM) microenvironment play a critical role during AML progression and resistance to drug treatments. Therefore, the identification of novel therapies requires drug-screening methods using in vitro co-culture models that closely recreate the cytoprotective BM setting. We have developed a new fluorescence-based in vitro co-culture system scalable to high throughput for measuring the concomitant effect of drugs on AML cells and the cytoprotective BM microenvironment. eGFP-expressing AML cells are co-cultured in direct contact with mCherry-expressing BM stromal cells for the accurate assessment of proliferation, viability, and signaling in both cell types. This model identified several efficacious compounds that overcome BM stroma-mediated drug resistance against daunorubicin, including the chromosome region maintenance 1 (CRM1/XPO1) inhibitor KPT-330. In silico analysis of genes co-expressed with CRM1, combined with in vitro experiments using our new methodology, also indicates that the combination of KPT-330 with the AURKA pharmacological inhibitor alisertib circumvents the cytoprotection of AML cells mediated by the BM stroma. This new experimental model and analysis provide a more precise screening method for developing improved therapeutics targeting AML cells within the cytoprotective BM microenvironment.

EZH2: An Accomplice of Gastric Cancer

Gastric cancer is the fifth most common cancer and the third leading cause of cancer deaths worldwide. Understanding the factors influencing the therapeutic effects in gastric cancer patients and the molecular mechanism behind gastric cancer is still facing challenges. In addition to genetic alterations and environmental factors, it has been demonstrated that epigenetic mechanisms can also induce the occurrence and progression of gastric cancer. Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of the polycomb repressor complex 2 (PRC2), which trimethylates histone 3 at Lys-27 and regulates the expression of downstream target genes through epigenetic mechanisms. It has been found that EZH2 is overexpressed in the stomach, which promotes the progression of gastric cancer through multiple pathways. In addition, targeted inhibition of EZH2 expression can effectively delay the progression of gastric cancer and improve its resistance to chemotherapeutic agents. Given the many effects of EZH2 in gastric cancer, there are no studies to comprehensively describe this mechanism. Therefore, in this review, we first introduce EZH2 and clarify the mechanisms of abnormal expression of EZH2 in cancer. Secondly, we summarize the role of EZH2 in gastric cancer, which includes the association of the EZH2 gene with genetic susceptibility to GC, the correlation of the EZH2 gene with gastric carcinogenesis and invasive metastasis, the resistance to chemotherapeutic drugs of gastric cancer mediated by EZH2 and the high expression of EZH2 leading to poor prognosis of gastric cancer patients. Finally, we also clarify some of the current statuses of drug development regarding targeted inhibition of EZH2/PRC2 activity.

Facile synthesis of 6-organyl-4-(trifluoromethyl)pyridin-2(1H)-ones and their polyfluoroalkyl-containing analogs

The three-component cyclization of 3-polyfluoroalkyl-3-oxopropanoates and methyl ketones with ammonium acetate affords 6-organyl-4-(polyfluoroalkyl)pyridin-2(1H)-ones (organyl is alkyl, aryl, or hetaryl). The synthesized pyridones were evaluated for antifungal, antibacterial, and analgesic activity.

Identification of EZH2 as Cancer Stem Cell Marker in Clear Cell Renal Cell Carcinoma and the Anti-Tumor Effect of Epigallocatechin-3-Gallate (EGCG)

The aim of the study was to develop a new therapeutic strategy to target cancer stem cells (CSCs) in clear cell renal cell carcinoma (ccRCC) and to identify typical CSC markers to improve therapy effectiveness. It was found that the corrected-mRNA expression-based stemness index was upregulated in kidney renal clear cell carcinoma (KIRC) tissues compared to non-tumor tissue and increased with higher tumor stage and grade. EZH2 was identified as a CSC marker and prognosis factor for KIRC patients. The expression of EZH2 was associated with several activated tumor-infiltrating immune cells. High expression of EZH2 was enriched in immune-related pathways, low expression was related to several metabolic pathways. Epigallocatechin-3-gallate (EGCG) was identified as the most potent suppressor of EZH2, was able to inhibit viability, migration, and invasion, and to increase the apoptosis rate of ccRCC CSCs. KIF11, VEGF, and MMP2 were identified as predictive EGCG target genes, suggesting a potential mechanism of how EZH2 might regulate invasiveness and migration. The percentages of FoxP3+ Treg cells in the peripheral blood mononuclear cells of ccRCC patients decreased significantly when cultured with spheres pretreated with EGCG plus sunitinib compared to spheres without treatment. Our findings provide new insights into the treatment options of ccRCC based on targeting CSCs.

Emerging role of EZH2 in rheumatic diseases: A comprehensive review

Enhancer of zeste homolog 2 (EZH2) is a histone methylated enzyme. It trimethylates histone 3 lysine 27 (H3K27) to regulate epigenetic processes. Recently, studies showed excessive expression of EZH2 in rheumatic diseases, such as systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, and systemic sclerosis. Moreover, epigenetic modification of EZH2 regulates differentiation and proliferation of different immune cells. Therefore, in this review, we comprehensively discuss the role of EZH2 in rheumatic diseases. Collection of the evidence may provide a basis for further understanding the role of EZH2 and give potential for targeting these diseases.

Chemical biology and pharmacology of histone lysine methylation inhibitors

Histone lysine methylation is a post-translational modification that plays a key role in the epigenetic regulation of a broad spectrum of biological processes. Moreover, the dysregulation of histone lysine methyltransferases (KMTs) has been implicated in the pathogenesis of several diseases particularly cancer. Due to their pathobiological importance, KMTs have garnered immense attention over the last decade as attractive therapeutic targets. These endeavors have culminated in tens of chemical probes that have been used to interrogate many aspects of histone lysine methylation. Besides, over a dozen inhibitors have been advanced to clinical trials, including the EZH2 inhibitor tazemetostat approved for the treatment of follicular lymphoma and advanced epithelioid sarcoma. In this Review, we highlight the chemical biology and pharmacology of KMT inhibitors and targeted protein degraders focusing on the clinical development of EZH1/2, DOT1L, Menin-MLL, and WDR5-MLL inhibitors. We also briefly discuss the pharmacologic targeting of other KMTs.

Histone Lysine Methylation Modification and Its Role in Vascular Calcification

Histone methylation is an epigenetic change mediated by histone methyltransferase, and has been connected to the beginning and progression of several diseases. The most common ailments that affect the elderly are cardiovascular and cerebrovascular disorders. They are the leading causes of death, and their incidence is linked to vascular calcification (VC). The key mechanism of VC is the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like phenotypes, which is a highly adjustable process involving a variety of complex pathophysiological processes, such as metabolic abnormalities, apoptosis, oxidative stress and signalling pathways. Many researchers have investigated the mechanism of VC and related targets for the prevention and treatment of cardiovascular and cerebrovascular diseases. Their findings revealed that histone lysine methylation modification may play a key role in the various stages of VC. As a result, a thorough examination of the role and mechanism of lysine methylation modification in physiological and pathological states is critical, not only for identifying specific molecular markers of VC and new therapeutic targets, but also for directing the development of new related drugs. Finally, we provide this review to discover the association between histone methylation modification and VC, as well as diverse approaches with which to investigate the pathophysiology of VC and prospective treatment possibilities.

The Role and Mechanism of Lysine Methyltransferase and Arginine Methyltransferase in Kidney Diseases

Methylation can occur in both histones and non-histones. Key lysine and arginine methyltransferases under investigation for renal disease treatment include enhancer of zeste homolog 2 (EZH2), G9a, disruptor of telomeric silencing 1-like protein (DOT1L), and protein arginine methyltransferases (PRMT) 1 and 5. Recent studies have shown that methyltransferases expression and activity are also increased in several animal models of kidney injury, such as acute kidney injury(AKI), obstructive nephropathy, diabetic nephropathy and lupus nephritis. The inhibition of most methyltransferases can attenuate kidney injury, while the role of methyltransferase in different animal models remains controversial. In this article, we summarize the role and mechanism of lysine methyltransferase and arginine methyltransferase in various kidney diseases and highlight methyltransferase as a potential therapeutic target for kidney diseases.

Dual Inhibition of H3K9me2 and H3K27me3 Promotes Tumor Cell Senescence without Triggering the Secretion of SASP

Chemotherapy remains the most common cancer treatment. Although chemotherapeutic drugs induce tumor cell senescence, they are often associated with post-therapy tumor recurrence by inducing the senescence-associated secretory phenotype (SASP). Therefore, it is important to identify effective strategies to induce tumor cell senescence without triggering SASP. In this study, we used the small molecule inhibitors, UNC0642 (G9a inhibitor) and UNC1999 (EZH2 inhibitor) alone or in combination, to inhibit H3K9 and H3K27 methylation in different cancer cells. Dual inhibition of H3K9me2 and H3K27me3 in highly metastatic tumor cells had a stronger pro-senescence effect than either inhibitor alone and did not trigger SASP in tumor cells. Dual inhibition of H3K9me2 and H3K27me3 suppressed the formation of cytosolic chromatin fragments, which inhibited the cGAS-STING-SASP pathway. Collectively, these data suggested that dual inhibition of H3K9 and H3K27 methylation induced senescence of highly metastatic tumor cells without triggering SASP by inhibiting the cGAS-STING-SASP pathway, providing a new mechanism for the epigenetics-based therapy targeting H3K9 and H3K27 methylation.

GSK-126 Protects CA1 Neurons from H3K27me3-Mediated Apoptosis in Cerebral Ischemia

Epigenetics, including histone modifications, play a significant role in central nervous system diseases, but the underlying mechanism remains to be elucidated. The aim of this study was to evaluate the role of H3K27me3 in regulating transcriptomic and pathogenic mechanisms following global ischemic stroke. Here, we found that in vivo ischemic/reperfusion (I/R) injury induced marked upregulation of H3K27me3 in the hippocampus. The administration of GSK-126 to rat brains decreased the levels of H3K27me3 in the hippocampus and reduced neuronal apoptosis after experimental stroke. Furthermore, ChIP-seq data demonstrated that the primary role of GSK-126 in the ischemic brain is to reduce H3K27me3 enrichment, mediating negative regulation of the execution phase of apoptosis and the MAPK signaling pathway. Further study suggested that the protective role of GSK-126 in ischemic rats was antagonized by U0126, an inhibitor of ERK1/2. Collectively, we demonstrated the potential of H3K27me3 as a novel stroke therapeutic target, and GSK-126 exerted a neuroprotective function in ischemic brain injury, which might be associated with activation of the MAPK/ERK pathway.

An overview of the development of EED inhibitors to disable the PRC2 function

Polycomb repressive complex 2 (PRC2) catalyzes the methylation of histone H3 lysine 27 (H3K27) and the enrichment of its catalytic product H3K27me3 is responsible for the silencing of tumor suppressor genes and the blocking of transcripts related to immunity and cell terminal differentiation. Aberrations of PRC2 components, such as mutation and overexpression, have been observed in various cancers, which makes PRC2 a potential therapeutic target for cancer. Up to now, targeting the enhancer of zeste homolog 2 (EZH2), the catalytic subunit of PRC2, represents the main strategy in the development of PRC2 inhibitors. Although significant progress has been made, new problems also emerge, e.g. the drug resistance caused by secondary mutations. In recent years, more and more efforts have shifted to another new strategy - targeting embryonic ectoderm development (EED) to disrupt its major interactions with other components, which are necessary to the PRC2 function, and some promising results have been obtained. This review summarizes the recent development of EED inhibitors as possible chemotherapy for cancer treatment, which could help accelerate future related research work.

Fascinating Transformation of SAM-Competitive Protein Methyltransferase Inhibitors from Nucleoside Analogues to Non-Nucleoside Analogues

The abnormal expression of protein methyltransferase (PMT) has been linked with many diseases such as diabetes, neurological disorders, and cancer. S-Adenyl-l-methionine (SAM) is a universal methyl donor and gets converted to S-adenyl-l-homocysteine (SAH), an endogenous competitive inhibitor of SAM. Initially developed SAM/SAH mimetic nucleoside analogues were pan methyltransferase inhibitors. The gradual understanding achieved through ligand-receptor interaction paved the way for various rational approaches of drug design leading to potent and selective nucleoside inhibitors. The present perspective is based on the systematic evolution of selective SAM-competitive heterocyclic non-nucleoside inhibitors from nucleoside inhibitors. This fascinating transition has resolved several issues inherent to nucleoside analogues such as poor pharmacokinetics leading to poor in vivo efficacy. The perspective has brought together various concepts and strategies of drug design that contributed to this rational transition. We firmly believe that the strategies described herein will serve as a template for the future development of drugs in general.

Transition-Metal-, Additive-, and Solvent-Free [3 + 3] Annulation of RCF2-Imidoyl Sulfoxonium Ylides with Cyclopropenones to Give Multifunctionalized CF3-Pyridones

An efficient and practical strategy was developed to synthesize 1,3,4-triaryl-6-trifluoromethylpyridones from CF₃-imidoyl sulfoxonium ylides and cyclopropenones in good to excellent yields. This stepwise [3 + 3] annulation reaction was carried out under transition-metal-, additive-, and solvent-free conditions, generating 1 equiv of dimethyl sulfoxide as byproduct and tolerating a series of functional groups.

EZH2 as a new therapeutic target in brain tumors: Molecular landscape, therapeutic targeting and future prospects

Brain tumors are responsible for high mortality and morbidity worldwide. The brain tumor treatment depends on identification of molecular pathways involved in progression and malignancy. Enhancer of zeste homolog 2 (EZH2) has obtained much attention in recent years in field of cancer therapy due to its aberrant expression and capacity in modulating expression of genes by binding to their promoter and affecting methylation status. The present review focuses on EZH2 signaling in brain tumors including glioma, glioblastoma, astrocytoma, ependymomas, medulloblastoma and brain rhabdoid tumors. EZH2 signaling mainly participates in increasing proliferation and invasion of cancer cells. However, in medulloblastoma, EZH2 demonstrates tumor-suppressor activity. Furthermore, EZH2 can regulate response of brain tumors to chemotherapy and radiotherapy. Various molecular pathways can function as upstream mediators of EZH2 in brain tumors including lncRNAs and miRNAs. Owing to its enzymatic activity, EZH2 can bind to promoter of target genes to induce methylation and affects their expression. EZH2 can be considered as an independent prognostic factor in brain tumors that its upregulation provides undesirable prognosis. Both anti-tumor agents and gene therapies such as siRNA have been developed for targeting EZH2 in cancer therapy.

A Review on the Therapeutic Role of TKIs in Case of CML in Combination With Epigenetic Drugs

Chronic myeloid leukemia is a malignancy of bone marrow that affects white blood cells. There is strong evidence that disease progression, treatment responses, and overall clinical outcomes of CML patients are influenced by the accumulation of other genetic and epigenetic abnormalities, rather than only the BCR/ABL1 oncoprotein. Both genetic and epigenetic factors influence the efficacy of CML treatment strategies. Targeted medicines known as tyrosine-kinase inhibitors have dramatically improved long-term survival rates in CML patients during the previous 2 decades. When compared to earlier chemotherapy treatments, these drugs have revolutionized CML treatment and allowed most people to live longer lives. Although epigenetic inhibitors' activity is disrupted in many cancers, including CML, but when combined with TKI, they may offer potential therapeutic strategies for the treatment of CML cells. The epigenetics of tyrosine kinase inhibitors and resistance to them is being studied, with a particular focus on imatinib, which is used to treat CML. In addition, the use of epigenetic drugs in conjunction with TKIs has been discussed. Resistance to TKIs is still a problem in curing the disease, necessitating the development of new therapies. This study focused on epigenetic pathways involved in CML pathogenesis and tumor cell resistance to TKIs, both of which contribute to leukemic clone breakout and proliferation.

Small-Molecule Inhibitors Overcome Epigenetic Reprogramming for Cancer Therapy

Cancer treatment is a significant challenge for the global health system, although various pharmacological and therapeutic discoveries have been made. It has been widely established that cancer is associated with epigenetic modification, which is reversible and becomes an attractive target for drug development. Adding chemical groups to the DNA backbone and modifying histone proteins impart distinct characteristics on chromatin architecture. This process is mediated by various enzymes modifying chromatin structures to achieve the diversity of epigenetic space and the intricacy in gene expression files. After decades of effort, epigenetic modification has represented the hallmarks of different cancer types, and the enzymes involved in this process have provided novel targets for antitumor therapy development. Epigenetic drugs show significant effects on both preclinical and clinical studies in which the target development and research offer a promising direction for cancer therapy. Here, we summarize the different types of epigenetic enzymes which target corresponding protein domains, emphasize DNA methylation, histone modifications, and microRNA-mediated cooperation with epigenetic modification, and highlight recent achievements in developing targets for epigenetic inhibitor therapy. This article reviews current anticancer small-molecule inhibitors targeting epigenetic modified enzymes and displays their performances in different stages of clinical trials. Future studies are further needed to address their off-target effects and cytotoxicity to improve their clinical translation.

Polycomb Repressive Complex 2 Modulation through the Development of EZH2-EED Interaction Inhibitors and EED Binders

Epigenetics is nowadays a well-accepted area of research. In the last years, tremendous progress was made regarding molecules targeting EZH2, directly or indirectly. Recently tazemetostat hit the market after FDA-approval for the treatment of lymphoma. However, the impairment of EZH2 activity by orthosteric intervention has proven to be effective only in a limited subset of cancers. Considering the multiproteic nature of the PRC2 complex and the marked dependence of EZH2 functions on the other core subunits such as EED, in recent years, a new targeting approach ascended to prominence. The possibility to cripple the function of the PRC2 complex by interfering with its multimeric integrity fueled the interest in developing EZH2–EED protein–protein interaction and EED inhibitors as indirect modulators of PRC2-dependent methyltransferase activity. In this Perspective, we aim to summarize the latest findings regarding the development and the biological activity of these emerging classes of PRC2 modulators from a medicinal chemist’s viewpoint.

Chemoselective N- and O-Difluoromethylation of 2-Pyridones, Isoquinolinones, and Quinolinones with TMSCF2Br

An operationally simple protocol for direct N- and O-difluoromethylation of 2-pyridones, quinolinones, and isoquinolinones using commercially available TMSCF₂Br is disclosed. The chemoselectivity is modulated by simple variations in temperature, solvent, and strength of the base. Diverse, synthetically relevant functional groups are tolerated, including functional groups that have reported reactivity with TMSCF₂Br. Gram-scale reactions to prepare both N- and O-difluoromethyl compounds are included.

Structure-Guided Development of Small-Molecule PRC2 Inhibitors Targeting EZH2-EED Interaction

Disruption of EZH2-embryonic ectoderm development (EED) protein-protein interaction (PPI) is a new promising cancer therapeutic strategy. We have previously reported the discovery of astemizole, a small-molecule inhibitor targeting the EZH2-EED PPI. Herein, we report the cocrystal structure of EED in complex with astemizole at 2.15 Å. The structure elucidates the detailed binding mode of astemizole to EED and provides a structure-guided design for the discovery of a novel EZH2-EED interaction inhibitor, DC-PRC2in-01, with an affinity K_d of 4.56 μM. DC-PRC2in-01 destabilizes the PRC2 complex, thereby leading to the degradation of PRC2 core proteins and the decrease of global H3K27me3 levels in cancer cells. The proliferation of PRC2-driven lymphomas cells is effectively inhibited, and the cell cycle is arrested in the G0/G1 phase. Together, these data demonstrate that DC-PRC2in-01 could be an effective chemical probe for investigating the PRC2-related physiology and pathology and providing a promising chemical scaffold for further development.

Diversity-oriented functionalization of 2-pyridones and uracils

Heterocycles 2-pyridone and uracil are privileged pharmacophores. Diversity-oriented synthesis of their derivatives is in urgent need in medicinal chemistry. Herein, we report a palladium/norbornene cooperative catalysis enabled dual-functionalization of iodinated 2-pyridones and uracils. The success of this research depends on the use of two unique norbornene derivatives as the mediator. Readily available alkyl halides/tosylates and aryl bromides are utilized as ortho-alkylating and -arylating reagents, respectively. Widely accessible ipso-terminating reagents, including H/DCO2Na, boronic acid/ester, terminal alkene and alkyne are compatible with this protocol. Thus, a large number of valuable 2-pyridone derivatives, including deuterium/CD3-labeled 2-pyridones, bicyclic 2-pyridones, 2-pyridone-fenofibrate conjugate, axially chiral 2-pyridone (97% ee), as well as uracil and thymine derivatives, can be quickly prepared in a predictable manner (79 examples reported), which will be very useful in new drug discovery.

Predictive biomarkers and potential drug combinations of epi-drugs in cancer therapy

Epigenetics studies heritable genomic modifications that occur with the participation of epigenetic modifying enzymes but without alterations of the nucleotide structure. Small-molecule inhibitors of these epigenetic modifying enzymes are known as epigenetic drugs (epi-drugs), which can cause programmed death of tumor cells by affecting the cell cycle, angiogenesis, proliferation, and migration. Epi-drugs include histone methylation inhibitors, histone demethylation inhibitors, histone deacetylation inhibitors, and DNA methylation inhibitors. Currently, epi-drugs undergo extensive development, research, and application. Although epi-drugs have convincing anti-tumor effects, the patient's sensitivity to epi-drug application is also a fundamental clinical issue. The development and research of biomarkers for epi-drugs provide a promising direction for screening drug-sensitive patients. Here, we review the predictive biomarkers of 12 epi-drugs as well as the progress of combination therapy with chemotherapeutic drugs or immunotherapy. Further, we discuss the improvement in the development of natural ingredients with low toxicity and low side effects as epi-drugs.

Disruption of YY1-EZH2 Interaction Using Synthetic Peptides Inhibits Breast Cancer Development

Simple Summary

Both Yin Yang 1 (YY1) and enhancer of zeste homolog 2 (EZH2) are oncogenes with overexpressed statuses in cancers. As a transcription factor, YY1 recruits EZH2 through its oncoprotein binding (OPB) domain to repress gene expression. In this study, we identified the interaction domain of YY1 on EZH2 protein with amino acids 493–519, named the YY1 protein binding (YPB) domain. Synthetic peptides using YPB and OPB domain sequences effectively blocked endogenous YY1-EZH2 interaction. Functionally, YPB and OPB peptides could efficiently inhibit the proliferation of breast cancer cells, promote their apoptosis, and reduce tumor growth in a xenograft mouse model. Using chromatin immunoprecipitation DNA sequencing (ChIP-seq) analysis, we discovered that YPB and OPB peptides could interfere with H3K27 trimethylation of multiple genes. Eventually, we identified that YPB and OPB peptides primarily targeted the PTENP1 gene and validated its importance in the anticancer activity of the two peptides.

Abstract

Enhancer of zeste homolog 2 (EZH2) is a methyltransferase to mediate lysine 27 trimethylation in histone H3 (i.e., H3K27me3) and repress gene expression. In solid tumors, EZH2 promotes oncogenesis and is considered a therapeutic target. As a transcription factor, Yin Yang 1 (YY1) recruits EZH2 through its oncoprotein binding (OPB) domain to establish gene repression. In this study, we mapped the YY1 protein binding (YPB) domain on EZH2 to a region of 27 amino acids. Both YPB and OPB domain synthetic peptides could disrupt YY1EZH2 interaction, markedly reduce breast cancer cell viability, and efficiently inhibit tumor growth in a xenograft mouse model. We analyzed MDA-MB-231 cells treated with YPB, OPB, and control peptides by chromatin immunoprecipitation DNA sequencing (ChIP-seq) using an antibody against H3K27me3. YPB and OPB treatments altered H3K27me3 on 465 and 1137 genes, respectively, compared to the control. Of these genes, 145 overlapped between the two peptides. Among them, PTENP1, the PTEN pseudogene, showed reduced H3K27me3 signal when treated by either YPB or OPB peptide. Consistently, the two peptides enhanced both PTENP1 and PTEN expression with concomitantly reduced AKT activation. Further studies validated PTENP1′s contribution to the anticancer activity of YPB and OPB peptides.

NeuroD1 Dictates Tumor Cell Differentiation in Medulloblastoma

Tumor cells are characterized by unlimited proliferation and perturbed differentiation. Using single-cell RNA sequencing, we demonstrate that tumor cells in medulloblastoma (MB) retain their capacity to differentiate in a similar way as their normal originating cells, cerebellar granule neuron precursors. Once they differentiate, MB cells permanently lose their proliferative capacity and tumorigenic potential. Differentiated MB cells highly express NeuroD1, a helix-loop-helix transcription factor, and forced expression of NeuroD1 promotes the differentiation of MB cells. The expression of NeuroD1 in bulk MB cells is repressed by trimethylation of histone 3 lysine-27 (H3K27me3). Inhibition of the histone lysine methyltransferase EZH2 prevents H3K27 trimethylation, resulting in increased NeuroD1 expression and enhanced differentiation in MB cells, which consequently reduces tumor growth. These studies reveal the mechanisms underlying MB cell differentiation and provide rationales to treat MB (potentially other malignancies) by stimulating tumor cell differentiation.

Cheng et al. demonstrate that medulloblastoma cells retain the capacity to undergo differentiation. The differentiation of tumor cells is regulated by NeuroD1 expression, which is repressed by H3K27me3 in tumor cells. EZH2 inhibitors suppress medulloblastoma growth by stimulating tumor cell differentiation.

Full methylation of H3K27 by PRC2 is dispensable for initial embryoid body formation but required to maintain differentiated cell identity

Polycomb repressive complex 2 (PRC2) catalyzes methylation of histone H3 on lysine 27 and is required for normal development of complex eukaryotes. The nature of that requirement is not clear. H3K27me3 is associated with repressed genes, but the modification is not sufficient to induce repression and, in some instances, is not required. We blocked full methylation of H3K27 with both a small molecule inhibitor, GSK343, and by introducing a point mutation into EZH2, the catalytic subunit of PRC2, in the mouse CJ7 cell line. Cells with substantively decreased H3K27 methylation differentiate into embryoid bodies, which contrasts with EZH2 null cells. PRC2 targets had varied requirements for H3K27me3, with a subset that maintained normal levels of repression in the absence of methylation. The primary cellular phenotype of blocked H3K27 methylation was an inability of altered cells to maintain a differentiated state when challenged. This phenotype was determined by H3K27 methylation in embryonic stem cells through the first 4 days of differentiation. Full H3K27 methylation therefore was not necessary for formation of differentiated cell states during embryoid body formation but was required to maintain a stable differentiated state.