Post-translational modifications of EZH2 in cancer

Tumor markers for lipid metabolism-related genes: Based on small cell lung cancer and bronchial asthma dual analysis

Numerous studies have elucidated the intricate relationship between bronchial asthma and small cell lung cancer (SCLC), as well as the role lipid metabolism genes play in transitioning from bronchial asthma to SCLC. Despite this, the predictive power of single gene biomarkers remains insufficient and necessitates the development of more accurate prognostic models. In our study, we downloaded and preprocessed scRNA-seq of SCLC from the GEO database GSE164404 and severe asthma scRNA-seq from GSE145013 using the Seurat package. Using the MSigDB database and geneCard database, we selected lipid metabolism-related genes and performed scRNA-seq data analysis from the gene expression GEO database, aiming to uncover potential links between immune signaling pathways in bronchial asthma and SCLC. Our investigations yielded differentially expressed genes based on the scRNA-seq dataset related to lipid metabolism. We executed differential gene analysis, gene ontology, and Kyoto Encyclopedia of Genes and Genomes analyses. In-depth GSEA pathway activation analysis, crucial target gene predictions via protein-protein interactions, and key cluster gene evaluations for differential and diagnostic ROC values correlation analysis confirmed that key cluster genes are significant predictors for the progression of bronchial asthma to SCLC. To validate our findings, we performed wet laboratory experiments using real-time quantitative PCR to assess the expression of these relevant genes in SCLC cell lines. In conclusion, this research proposes a novel lipid metabolism-related gene marker that can offer comprehensive insights into the pathogenesis of bronchial asthma leading to SCLC. Although this study does not directly focus on senescence-associated molecular alterations, our findings in the lipid metabolism genes associated with inflammation and cancer progression offer valuable insights for further research targeting senescence-related changes in treating inflammatory diseases.

A methylation-phosphorylation switch controls EZH2 stability and hematopoiesis

The Polycomb Repressive Complex 2 (PRC2) methylates H3K27 to regulate development and cell fate by transcriptional silencing. Alteration of PRC2 is associated with various cancers. Here, we show that mouse Kdm1a deletion causes a dramatic reduction of PRC2 proteins, whereas mouse null mutation of L3mbtl3 or Dcaf5 results in PRC2 accumulation and increased H3K27 trimethylation. The catalytic subunit of PRC2, EZH2, is methylated at lysine 20 (K20), promoting EZH2 proteolysis by L3MBTL3 and the CLR4DCAF5 ubiquitin ligase. KDM1A (LSD1) demethylates the methylated K20 to stabilize EZH2. K20 methylation is inhibited by AKT-mediated phosphorylation of serine 21 in EZH2. Mouse Ezh2K20R/K20R mutants develop hepatosplenomegaly associated with high GFI1B expression, and Ezh2K20R/K20R mutant bone marrows expand hematopoietic stem cells and downstream hematopoietic populations. Our studies reveal that EZH2 is regulated by methylation-dependent proteolysis, which is negatively controlled by AKT-mediated S21 phosphorylation to establish a methylation-phosphorylation switch to regulate the PRC2 activity and hematopoiesis.

Regulation of EZH2 protein stability: new mechanisms, roles in tumorigenesis, and roads to the clinic

The importance of EZH2 as a key methyltransferase has been well documented theoretically. Practically, the first EZH2 inhibitor Tazemetostat (EPZ6438), was approved by FDA in 2020 and is used in clinic. However, for most solid tumors it is not as effective as desired and the scope of clinical indications is limited, suggesting that targeting its enzymatic activity may not be sufficient. Recent technologies focusing on the degradation of EZH2 protein have drawn attention due to their potential robust effects. This review focuses on the molecular mechanisms that regulate EZH2 protein stability via post-translational modifications (PTMs), mainly including ubiquitination, phosphorylation, and acetylation. In addition, we discuss recent advancements of multiple proteolysis targeting chimeras (PROTACs) strategies and the latest degraders that can downregulate EZH2 protein. We aim to highlight future directions to expand the application of novel EZH2 inhibitors by targeting both EZH2 enzymatic activity and protein stability.

The involvement of RNA N6-methyladenosine and histone methylation modification in decidualization and endometriosis-associated infertility

Defective decidualization of endometrial stromal cells (ESCs) in endometriosis (EM) patients leads to inadequate endometrial receptivity and EM-associated infertility. Hypoxia is an inevitable pathological process of EM and participates in deficient decidualization of the eutopic secretory endometrium. Enhancer of zeste homology 2 (EZH2) is a methyltransferase which catalyses H3K27Me3, leading to decreased expression levels of target genes. Although EZH2 expression is low under normal decidualization, it is abundantly increased in the eutopic secretory endometrium of EM and is induced by hypoxia. Chromatin immunoprecipitation-PCR results revealed that decidua marker IGFBP1 is a direct target of EZH2, partially explaining the increased levels of histone methylation modification in defected decidualization of EM. To mechanism controlling this, we examined the effects of hypoxia on EZH2 and decidualization. EZH2 mRNA showed decreased m6 A modification and increased expression levels under hypoxia and decidualization combined treatment. Increased EZH2 expression was due to the increased expression of m6 A demethylase ALKBH5 and decreased expression of the m6 A reader protein YTHDF2. YTHDF2 directly bind to the m6 A modification site of EZH2 to promote EZH2 mRNA degradation in ESCs. Moreover, selective Ezh2 depletion in mouse ESCs increased endometrial receptivity and improved mouse fertility by up-regulating decidua marker IGFBP1 expression. This is the first report showing that YTHDF2 can act as a m6 A reader to promote decidualization by decreasing the stability of EZH2 mRNA and further increasing the expression of IGFBP1 in ESCs. Taken together, our findings highlight the critical role of EZH2/H3K27Me3 in decidualization and reveal a novel epigenetic mechanism by which hypoxia can suppress EM decidualization by decreasing the m6 A modification of EZH2 mRNA.

Biological functions and applications of LncRNAs in the regulation of the extracellular matrix in osteoarthritis

Osteoarthritis (OA) is a major cause of disability, characterized by chronic pain, irreversible destruction, and loss of function of the articular cartilage. The integrity and arrangement of the composition and structure of the extracellular matrix (ECM) are essential for maintaining the elasticity, integrity, and mechanical support function of the cartilage tissue. Osteoarthritis causes substantial changes in the ECM, driving the progression of the disease. Recent studies have shown that the ECM plays a critical role in the development of cartilage tissue as well as the occurrence and development of osteoarthritis by directly or indirectly regulating chondrocyte proliferation, apoptosis, differentiation, and gene expression. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs derived from large transcripts. Mutations and disorders of lncRNAs are closely related to the development of osteoarthritis. Abnormal expression of lncRNAs in osteoarthritic cartilage regulates the synthesis and decomposition of the cartilaginous ECM. Therefore, the use of lncRNAs as nucleic acid drugs that regulate their targets may reduce ECM degradation, thereby delaying the pathological progression of osteoarthritis. In this review, the regulatory effects of lncRNAs on ECM in different cell behaviors related to OA are summarized. The roles of lncRNAs in the proliferation, apoptosis, differentiation, and ECM-related gene activity of chondrocytes, as well as the application of lncRNAs as potential gene therapy drugs for the repair and regeneration of osteoarthritic tissue, are also reviewed. A better understanding of the roles of lncRNAs in guiding chondrocyte behavior and ECM metabolism is critical for their future applications in osteoarthritis therapy and regenerative medicine.

O-GlcNAcylation: the sweet side of epigenetics

Histones display a wide variety of post-translational modifications, including acetylation, methylation, and phosphorylation. These epigenetic modifications can influence chromatin structure and function without altering the DNA sequence. Histones can also undergo post-translational O-GlcNAcylation, a rather understudied modification that plays critical roles in almost all biological processes and is added and removed by O-linked N-acetylglucosamine transferase and O-GlcNAcase, respectively. This review provides a current overview of our knowledge of how O-GlcNAcylation impacts the histone code both directly and by regulating other chromatin modifying enzymes. This highlights the pivotal emerging role of O-GlcNAcylation as an essential epigenetic marker.

Cancer metastasis under the magnifying glass of epigenetics and epitranscriptomics

Most of the cancer-associated mortality and morbidity can be attributed to metastasis. The role of epigenetic and epitranscriptomic alterations in cancer origin and progression has been extensively demonstrated during the last years. Both regulations share similar mechanisms driven by DNA or RNA modifiers, namely writers, readers, and erasers; enzymes responsible of respectively introducing, recognizing, or removing the epigenetic or epitranscriptomic modifications. Epigenetic regulation is achieved by DNA methylation, histone modifications, non-coding RNAs, chromatin accessibility, and enhancer reprogramming. In parallel, regulation at RNA level, named epitranscriptomic, is driven by a wide diversity of chemical modifications in mostly all RNA molecules. These two-layer regulatory mechanisms are finely controlled in normal tissue, and dysregulations are associated with every hallmark of human cancer. In this review, we provide an overview of the current state of knowledge regarding epigenetic and epitranscriptomic alterations governing tumor metastasis, and compare pathways regulated at DNA or RNA levels to shed light on a possible epi-crosstalk in cancer metastasis. A deeper understanding on these mechanisms could have important clinical implications for the prevention of advanced malignancies and the management of the disseminated diseases. Additionally, as these epi-alterations can potentially be reversed by small molecules or inhibitors against epi-modifiers, novel therapeutic alternatives could be envisioned.

Emerging trends in post-translational modification: Shedding light on Glioblastoma multiforme

Recent multi-omics studies, including proteomics, transcriptomics, genomics, and metabolomics have revealed the critical role of post-translational modifications (PTMs) in the progression and pathogenesis of Glioblastoma multiforme (GBM). Further, PTMs alter the oncogenic signaling events and offer a novel avenue in GBM therapeutics research through PTM enzymes as potential biomarkers for drug targeting. In addition, PTMs are critical regulators of chromatin architecture, gene expression, and tumor microenvironment (TME), that play a crucial function in tumorigenesis. Moreover, the implementation of artificial intelligence and machine learning algorithms enhances GBM therapeutics research through the identification of novel PTM enzymes and residues. Herein, we briefly explain the mechanism of protein modifications in GBM etiology, and in altering the biologics of GBM cells through chromatin remodeling, modulation of the TME, and signaling pathways. In addition, we highlighted the importance of PTM enzymes as therapeutic biomarkers and the role of artificial intelligence and machine learning in protein PTM prediction.

DUBing Primary Tumors of the Central Nervous System: Regulatory Roles of Deubiquitinases

The ubiquitin proteasome system (UPS) utilizes an orchestrated enzymatic cascade of E1, E2, and E3 ligases to add single or multiple ubiquitin-like molecules as post-translational modification (PTM) to proteins. Ubiquitination can alter protein functions and/or mark ubiquitinated proteins for proteasomal degradation but deubiquitinases (DUBs) can reverse protein ubiquitination. While the importance of DUBs as regulatory factors in the UPS is undisputed, many questions remain on DUB selectivity for protein targeting, their mechanism of action, and the impact of DUBs on the regulation of diverse biological processes. Furthermore, little is known about the expression and role of DUBs in tumors of the human central nervous system (CNS). In this comprehensive review, we have used publicly available transcriptional datasets to determine the gene expression profiles of 99 deubiquitinases (DUBs) from five major DUB families in seven primary pediatric and adult CNS tumor entities. Our analysis identified selected DUBs as potential new functional players and biomarkers with prognostic value in specific subtypes of primary CNS tumors. Collectively, our analysis highlights an emerging role for DUBs in regulating CNS tumor cell biology and offers a rationale for future therapeutic targeting of DUBs in CNS tumors.

RCC1 functions as a tumor facilitator in clear cell renal cell carcinoma by dysregulating cell cycle, apoptosis, and EZH2 stability

BACKGROUND

RCC1 functions as a pivotal guanine nucleotide exchange factor and was reported to be involved in mitosis, the assembly of the nuclear envelope, nucleocytoplasmic transport in cell physiological processes. Recent studies reported that RCC1 could regulate immunological pathways and promote the growth of some malignant solid tumors. However, the prognostic value and exact function of RCC1 remain unknown in patients with clear cell renal cell carcinoma (cRCC).

METHODS

The UALCAN and KM plotter portals were used to analyze the expression profile and related tumor prognosis of RCC1 in ccRCC using data from TCGA. The expression profile of RCC1 was also confirmed in clinical samples using qRT-PCR, western blotting, and immunohistochemistry. The role of RCC1 on ccRCC cells in vitro was confirmed by a series of functional assays. Animal experiments were performed to verify the suppressive effect of RCC1 knockdown on tumor growth in vivo. The correlation of RCC1 expression with that of EZH2 was explored in clinical samples using IHC. The interaction between RCC1 and EZH2 was further verified using a CO-IP assay and a protein stability assay.

RESULTS

RCC1 was upregulated in ccRCC tissues compared with normal tissues in TCGA dataset and paired clinical samples. RCC1 promoted ccRCC progression by accelerating the cell cycle and suppressing apoptosis. In addition, RCC1 could bind EZH2 and regulate its expression at the posttranscriptional level. RCC1 and EZH2 expression showed a strong correlation in clinical samples. Further investigation proved that RCC1 regulated EZH2 protein stability through the ubiquitin-proteasome pathway.

CONCLUSIONS

RCC1 could be a potential therapeutic target in ccRCC. The RCC1/EZH2 axis takes part in the development of ccRCC.

Yin Yang 1-Induced Long Noncoding RNA DUXAP9 Drives the Progression of Oral Squamous Cell Carcinoma by Blocking CDK1-Mediated EZH2 Degradation

LncRNAs play a critical role in oral squamous cell carcinoma (OSCC) progression. However, the function and detailed molecular mechanism of most lncRNAs in OSCC are not fully understood. Here, a novel nuclear-localized lncRNA, DUXAP9 (DUXAP9), that is highly expressed in OSCC is identified. A high level of DUXAP9 is positively associated with lymph node metastasis, poor pathological differentiation, advanced clinical stage, worse overall survival, and worse disease-specific survival in OSCC patients. Overexpression of DUXAP9 significantly promotes OSCC cell proliferation, migration, invasion, and xenograft tumor growth and metastasis, and upregulates N-cadherin, Vimentin, Ki67, PCNA, and EZH2 expression and downregulates E-cadherin in vitro and in vivo, whereas knockdown of DUXAP9 remarkably suppresses OSCC cell proliferation, migration, invasion, and xenograft tumor growth in vitro and in vivo in an EZH2-dependent manner. Yin Yang 1 (YY1) is found to activate the transcriptional expression of DUXAP9 in OSCC. Furthermore, DUXAP9 physically interacts with EZH2 and inhibits EZH2 degradation via the suppression of EZH2 phosphorylation, thereby blocking EZH2 translocation from the nucleus to the cytoplasm. Thus, DUXAP9 can serve as a promising target for OSCC therapy.

Artificial intelligence in ophthalmology: The path to the real-world clinic

Artificial intelligence (AI) has great potential to transform healthcare by enhancing the workflow and productivity of clinicians, enabling existing staff to serve more patients, improving patient outcomes, and reducing health disparities. In the field of ophthalmology, AI systems have shown performance comparable with or even better than experienced ophthalmologists in tasks such as diabetic retinopathy detection and grading. However, despite these quite good results, very few AI systems have been deployed in real-world clinical settings, challenging the true value of these systems. This review provides an overview of the current main AI applications in ophthalmology, describes the challenges that need to be overcome prior to clinical implementation of the AI systems, and discusses the strategies that may pave the way to the clinical translation of these systems.

Implication of KDM6A in bladder cancer

Background: Bladder cancer is a common urogenital malignancy characterized by frequent genetic alterations. Histone demethylase gene KDM6A is commonly mutated in bladder cancer. Aim: To review the characteristics of KDM6A and its mutation consequences, and to introduce a potential KDM6A-targeted treatment. Methods: We conducted a comprehensive literature search using two electronic databases, MEDLINE and Cochrane Library, to retrieve topic-related articles from July 2013 to July 2022 using keywords 'KDM6A', 'bladder cancer', 'UTX', 'treatment' and 'mutation'. Five reviewers independently screened literature search results and abstracted data from included studies. Descriptive analysis was conducted and 30 articles were retained. Main Results: A total of 30 articles were retrieved. Experimental and clinical data were collected and grouped by theme. Therapeutic strategies are depicted and organized by tables for a better understanding. Conclusion: This review demonstrates that KDM6A has crucial implications in bladder cancer pathogenesis and treatment.

lncRNAs-EZH2 interaction as promising therapeutic target in cutaneous melanoma

Melanoma is the most lethal skin cancer with increasing incidence worldwide. Despite a great improvement of diagnostics and treatment of melanoma patients, this disease is still a serious clinical problem. Therefore, novel druggable targets are in focus of research. EZH2 is a component of the PRC2 protein complex that mediates epigenetic silencing of target genes. Several mutations activating EZH2 have been identified in melanoma, which contributes to aberrant gene silencing during tumor progression. Emerging evidence indicates that long non-coding RNAs (lncRNAs) are molecular "address codes" for EZH2 silencing specificity, and targeting lncRNAs-EZH2 interaction may slow down the progression of many solid cancers, including melanoma. This review summarizes current knowledge regarding the involvement of lncRNAs in EZH2-mediated gene silencing in melanoma. The possibility of blocking lncRNAs-EZH2 interaction in melanoma as a novel therapeutic option and plausible controversies and drawbacks of this approach are also briefly discussed.

Polycomb Repressive Complex 2 in Oncology

Dynamic regulation of the chromatin state by Polycomb Repressive Complex 2 (PRC2) provides an important mean for epigenetic gene control that can profoundly influence normal development and cell lineage specification. PRC2 and PRC2-induced methylation of histone H3 lysine 27 (H3K27) are critically involved in a wide range of DNA-templated processes, which at least include transcriptional repression and gene imprinting, organization of three-dimensional chromatin structure, DNA replication and DNA damage response and repair. PRC2-based genome regulation often goes wrong in diseases, notably cancer. This chapter discusses about different modes-of-action through which PRC2 and EZH2, a catalytic subunit of PRC2, mediate (epi)genomic and transcriptomic regulation. We will also discuss about how alteration or mutation of the PRC2 core or axillary component promotes oncogenesis, how post-translational modification regulates functionality of EZH2 and PRC2, and how PRC2 and other epigenetic pathways crosstalk. Lastly, we will briefly touch on advances in targeting EZH2 and PRC2 dependence as cancer therapeutics.

Oxidative Stress and Nuclear Reprogramming: A Pilot Study of the Effects of Reactive Oxygen Species on Architectural and Epigenetic Landscapes

Cell genome integrity is continuously threatened by various sources, both endogenous and exogenous. Oxidative stress causes a multitude of damages, severely affecting cell viability, fidelity of genetic information inheritance, and determining profound alterations in gene expression. Epigenetics represents a major form of gene expression modulation, influencing DNA accessibility to transcription factors and the overall nuclear architecture. When assessing the stress-induced epigenome reprogramming, widely diffused biochemical and molecular approaches commonly fail to incorporate analyses such as architectural chromatin alterations and target molecules precise spatial localization. Unveiling the significance of the nuclear response to the oxidative stress, as well as the functional effects over the chromatin organization, may reveal targets and strategies for approaches aiming at limiting the impact on cellular stability. For these reasons, we utilized potassium bromate treatment, a stressor able to induce DNA damages without altering the cellular microenvironment, hence purely modeling nuclear oxidative stress. By means of high-resolution techniques, we described profound alterations in DNA and histone epigenetic modifications and in chromatin organization in response to the reactive oxygen species.

Decreased Expression of EZH2 in Granulosa Cells Contributes to Endometriosis-Associated Infertility by Targeting IL-1R2

The mechanism by which endometriosis, a common gynecological disease characterized by chronic pelvic pain and infertility, causes infertility remains elusive. Luteinized unruptured follicle syndrome, the most common type of ovulatory dysfunction, is a cause of endometriosis-associated infertility involving reduced numbers of retrieved and mature oocytes. Ovulation is controlled by luteinizing hormone and paracrine signals produced within the follicle microenvironment. Generally, interleukin (IL)-1β is elevated in endometriosis follicular fluid, whereby it amplifies ovulation signals by activating extracellular-regulated kinase 1/2 and CCAAT/enhancer binding protein β pathways. However, this amplification of ovulation by IL-1β does not occur in patients with endometriosis. To illuminate the mechanism of ovulatory dysfunction in endometriosis, we analyzed the effect of oxidative stress and IL-1β expression on endometriosis follicles. We found that oxidative stress decreased EZH2 expression and reduced H3K27Me3 levels in endometriosis ovarian granulosa cells (GCs). Selective Ezh2 depletion in mice ovarian GCs reduced fertility by disturbing cumulus-oocyte complex expansion and reducing epidermal growth factor-like factor expression. Gene expression and H3K27Me3 ChIP-sequencing (ChIP-Seq) of GCs revealed IL-1 receptor 2 (IL-1R2), a high-affinity IL-1β-receptor that suppresses IL-1β-mediated inflammatory cascades during ovulation, as a crucial target gene of the EZH2-H3K27Me3 axis. Moreover, IL-1β addition did not restore ovulation upon Ezh2 knockdown, indicating a vital function of IL-1R2 in endometriosis. Thus, our findings show that reducing EZH2 and H3K27Me3 in GCs suppressed ovulatory signals by increasing IL-1R2 expression, which may ultimately contribute to endometriosis-associated infertility.

Gene amplification-driven lncRNA SNHG6 promotes tumorigenesis via epigenetically suppressing p27 expression and regulating cell cycle in non-small cell lung cancer

Long non-coding RNAs (lncRNAs) have been validated to play essential roles in non-small cell lung carcinoma (NSCLC) progression. In this study, through systematically screening GSE33532 and GSE29249 from Gene Expression Omnibus (GEO) database and bioinformatics analysis, we found the significant upregulation of SNHG6 in NSCLC. The activation of SNHG6 was driven by copy number amplification and high expression of SNHG6 indicated a poor prognosis. Functionally, the knockdown of SNHG6 inhibited NSCLC cell proliferation, migration, and suppressed the G1/S transition of the cell cycle. SNHG6 overexpression had the opposite effects. Mechanically, SNHG6 recruited EZH2 to the promoter region of p27 and increased H3K27me3 enrichment, thus epigenetically repressing the expression of p27, regulating the cell cycle, and promoting tumorigenesis of NSCLC. SNHG6 silencing restrained tumor growth in vivo and suppressed the expressions of cell cycle-related proteins in the G1/S transition. In conclusion, our study uncovered a novel mechanism of SNHG6 activation and its function. SNHG6 can be considered a potential target for the diagnosis and treatment of NSCLC in the future.

Protein kinase Cλ/ι in cancer: a contextual balance of time and signals

Nononcogenic cancer drivers often impinge on complex signals that create new addictions and vulnerabilities. Protein kinase Cλ/ι (PKCλ/ι) suppresses tumorigenesis by blocking metabolic pathways that regulate fuel oxidation and create building blocks for the epigenetic control of cell differentiation. Reduced levels of PKCλ/ι unleash these pathways to promote tumorigenesis, but the simultaneous activation of the STING-driven interferon cascade prevents tumor initiation by triggering immunosurveillance mechanisms. However, depending on the context of other signaling pathways, such as WNT/β-catenin or PKCζ, and timing, PKCλ/ι deletion can promote or inhibit tumorigenesis. In this review, we discuss in detail the molecular and cellular underpinnings of PKCλ/ι functions in cancer with the perspective of the crosstalk between metabolism and inflammation in the tumor microenvironment.

The O-GlcNAcylation and its promotion to hepatocellular carcinoma

O-GlcNAcylation is a posttranslational modification that attaches O-linked β-N-acetylglucosamine (O-GlcNAc) to the serine and threonine residues of proteins. Such a glycosylation would alter the activities, stabilities, and interactions of target proteins that are functional in a wide range of biological processes and diseases. Accumulating evidence indicates that O-GlcNAcylation is tightly associated with hepatocellular carcinoma (HCC) in its onset, growth, invasion and metastasis, drug resistance, and stemness. Here we summarize the discoveries of the role of O-GlcNAcylation in HCC and its function mechanism, aiming to deepen our understanding of HCC pathology, generate more biomarkers for its diagnosis and prognosis, and offer novel molecular targets for its treatment.

SMYD3 regulates gastric cancer progression and macrophage polarization through EZH2 methylation

SET and MYND domain-containing protein 3 (SMYD3), a known histone methyltransferase, was reported to regulate cancer pathogenesis. However, its role in gastric development and progression remains unclear. EZH2 methylation had been associated with cancer metastasis, but the EZH2 methylation status in gastric cancer (GC) is unknown. Here, we report that EZH2 K421 methylation was responsible for gastric cancer cell soft agar colony formation, in vivo metastasis, and macrophage polarization. Mechanically, we identified SMYD3 as the methyltransferase of EZH2 at K421 residue which accelerates EZH2 Ubiquitin proteasome degradation. Cell harboring non-methylated EZH2 mutants promotes gastric cancer cell metastasis. Taken together, our results showed that SMYD3-EZH2 axis restricts gastric cancer metastasis via integrating epigenetic signaling.

EZH2 Regulates ANXA6 Expression via H3K27me3 and Is Involved in Angiotensin II-Induced Vascular Smooth Muscle Cell Senescence

Objectives

Abdominal aortic aneurysm (AAA) has a high risk of rupture of the aorta and is one of the leading causes of death in older adults. This study is aimed at confirming the influence and mechanism of the abnormally expressed ANXA6 gene in AAA.

Methods

Clinical samples were collected for proteome sequencing to screen for differentially expressed proteins. An Ang II-induced vascular smooth muscle cell (VSMC) aging model as well as an AAA animal model was used. Using RT-qPCR to detect the mRNA levels of EZH2, ANXA6, IK-6, and IL-8 in cells and tissues were assessed. Western blotting and immunohistochemistry staining were used apply for the expression of associated proteins in cells and tissues. SA-β-gal staining, flow cytometry, and DHE staining were used to detect senescent cells and the level of ROS. The cell cycle was assessed by flow cytometry. Arterial pathology was observed by HE staining. The aging of VSMCs in arterial tissue was assessed by coimmunofluorescence for α-SMA and p53.

Results

There were 24 differentially expressed proteins in the AAA clinical samples, including 10 upregulated protein and 14 downregulated protein, and the differential expression of ANXA6 was associated with vascular disease. Our study found that ANXA6 was highly expressed and EZH2 was lowly expressed in an Ang II-induced VSMC aging model. Knockdown of ANXA6 or overexpression of EZH2 inhibited Ang II-induced ROS, inhibited cell senescence, decreased Ang II evoked G1 arrest, and increased cells in G2 phase, while overexpression of ANXA6 played the opposite role. Overexpression of EZH2 inhibited ANXA6 expression by increasing H3K27me3 modification at the ANXA6 promoter. Simultaneous overexpression of EZH2 and the protective effect of EZH2 on cell senescence were partially reversed by ANXA6. Similarly, ANXA6 was highly expressed and EZH2 was lowly expressed in an Ang II-induced AAA animal model. Knockdown of ANXA6 and overexpression of EZH2 alleviated Ang II-induced VSMC senescence and inhibited AAA progression, while simultaneous overexpression of EZH2 and ANXA6 partially reversed the protective effect of EZH2 on AAA.

Conclusion

EZH2 regulates the ANXA6 promoter H3K27me3 modification, inhibits ANXA6 expression, alleviates Ang II-induced VSMC senescence, and inhibits AAA progression.

The emerging roles of TRIM21 in coordinating cancer metabolism, immunity and cancer treatment

Tripartite motif containing-21 (TRIM21), an E3 ubiquitin ligase, was initially found to be involved in antiviral responses and autoimmune diseases. Recently studies have reported that TRIM21 plays a dual role in cancer promoting and suppressing in the occurrence and development of various cancers. Despite the fact that TRIM21 has effects on multiple metabolic processes, inflammatory responses and the efficacy of tumor therapy, there has been no systematic review of these topics. Herein, we discuss the emerging role and function of TRIM21 in cancer metabolism, immunity, especially the immune response to inflammation associated with tumorigenesis, and also the cancer treatment, hoping to shine a light on the great potential of targeting TRIM21 as a therapeutic target.

The role of LINC01419 in regulating the cell stemness in lung adenocarcinoma through recruiting EZH2 and regulating FBP1 expression

Background

Recent years have witnessed a growing academic interest in the effects of lncRNAs on tumors. LINC01419 is found to facilitate proliferation and metastasis of lung adenocarcinoma (LUAD) cells, but there is a great deal of uncertainty about how LINC01419 works on LUAD cell stemness. For this reason, the focus of this research is centered on the regulatory impact of LINC01419 on LUAD cell stemness.

Methods

For the detection of the expression level of LINC01419 in LUAD, qRT-PCR was performed. And how oe-LINC01419 and sh-LINC01419 affected LUAD cell proliferation as well as stem cell sphere-formation were examined by CCK-8 and cell sphere-forming assays. In addition, whether LINC01419 could recruit EZH2 and regulate FBP1 expression were determined by bioinformatics analysis, RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (ChIP). Western blot was utilized to detect the protein expression levels of FBP1, CD44, CD133, and ALDH-1 as well.

Results

On the basis of the findings from those assays, an up-regulation of LINC01419 level was demonstrated in LUAD cell lines, and a remarkable upregulation of it in CD44 + LUAD cells. In LUAD cells, proliferation and stem cell sphere-formation that were attenuated by LINC01419 knockdown were discovered to be facilitated by LINC01419 overexpression. And a binding relationship between LINC01419 and EZH2 was determined by RIP assay. Besides, EZH2 was capable of binding to FBP1 promoter region, as found by ChIP-PCR assay. Finally, it was demonstrated by in vitro experiments that LINC01419 could inhibit FBP1 expression by recruiting EZH2, resulting in promotion of LUAD cell proliferation and stemness.

Significance

To summarize, our findings demonstrate a cancer-promoting role of LINC01419 in LUAD. LINC01419, by recruiting EZH2 and regulating FBP1 expression, contributes to LUAD cell stemness. According to these findings, the potential of LINC01419 to be the target for LUAD treatment is hence determined, which also adds more possibility to the enrichment of therapeutic strategies for lung cancer stem cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13062-022-00336-8.

Study on pharmacokinetic interactions between SHR2554 and itraconazole in healthy subjects: A single-center, open-label phase I trial

BACKGROUND

SHR2554, a novel oral Enhancer of Zeste Homolog 2 inhibitor, shows broad-spectrum anti-tumor efficacy in preclinical studies. As SHR2554 is mainly metabolized by CYP3A4, it is helpful to conduct research on the effects of itraconazole, a strong inhibitor of CYP3A4-metabolizing enzymes, on the pharmacokinetic characteristics and safety of SHR2554.

METHODS

We conducted a single-center, open-label pharmacokinetic study of itraconazole on SHR2554 in 18 healthy Chinese subjects. Subjects were orally administrated SHR2554 50 mg on Day 1, itraconazole 200 mg Quaque Die (QD) from Days 4 to 7, SHR2554 50 mg co-administrated with itraconazole 200 mg on Day 8, and itraconazole 200 mg QD from Days 9 to 12. Then, 4 ml of venous blood was collected at predetermined time points. Plasma SHR2554 concentrations were analyzed using a validated high-performance liquid chromatography tandem mass spectrometry method. Pharmacokinetic parameters were calculated using Phoenix WinNonlin v8.1.

RESULTS

The C_max of SHR2554 alone and in combination was 10.197 ± 7.0262 ng·ml^-1 versus 70.538 ± 25.0219 ng·ml^-1 , AUC_0-∞ was 50.99 ± 19.358 h·ng·ml^-1 versus 641.53 ± 319.538 h·ng·ml^-1 , and AUC_0-t was 28.70 ± 18.913 h·ng·ml^-1 versus 612.13 ± 315.720 h·ng·ml^-1 . Co-administration of SHR2554 and itraconazole caused 7.73-, 12.47-, and 23.75-fold adjusted geometric mean ratios increases in SHR2554 C_max , AUC_0-∞ and AUC_0-t respectively. The co-administration regimen was well tolerated and had a good safety profile.

CONCLUSIONS

Compared with a single dose of SHR2554 50 mg, the exposure of SHR2554 in vivo was significantly affected by the combined administration of itraconazole.

TP53-Status-Dependent Oncogenic EZH2 Activity in Pancreatic Cancer

Simple Summary

Epigenetic alterations contribute to the aggressiveness and therapy resistance of Pancreatic Ductal Adenocarcinoma (PDAC). However, epigenetic regulators, including Enhancer of Zeste Homolog 2 (EZH2), reveal a strong context-dependent activity. Our study aimed to examine the context-defining molecular prerequisites of oncogenic EZH2 activity in PDAC to assess the therapeutic efficacy of targeting EZH2. Our preclinical study using diverse PDAC models demonstrates that the TP53 status determines oncogenic EZH2 activity. Only in TP53-wildtype (wt) PDAC subtypes was EZH2 blockade associated with a favorable PDAC prognosis mainly through cell-death response. We revealed that EZH2 depletion increases p53wt stability by the de-repression of CDKN2A. Therefore, our study provides preclinical evidence that an intact CDKN2A-p53wt axis is indispensable for a beneficial outcome of EZH2 depletion and highlights the significance of molecular stratification to improve epigenetic targeting in PDAC.

Abstract

Pancreatic Ductal Adenocarcinoma (PDAC) represents a lethal malignancy with a consistently poor outcome. Besides mutations in PDAC driver genes, the aggressive tumor biology of the disease and its remarkable therapy resistance are predominantly installed by potentially reversible epigenetic dysregulation. However, epigenetic regulators act in a context-dependent manner with opposing implication on tumor progression, thus critically determining the therapeutic efficacy of epigenetic targeting. Herein, we aimed at exploring the molecular prerequisites and underlying mechanisms of oncogenic Enhancer of Zeste Homolog 2 (EZH2) activity in PDAC progression. Preclinical studies in EZH2 proficient and deficient transgenic and orthotopic in vivo PDAC models and transcriptome analysis identified the TP53 status as a pivotal context-defining molecular cue determining oncogenic EZH2 activity in PDAC. Importantly, the induction of pro-apoptotic gene signatures and processes as well as a favorable PDAC prognosis upon EZH2 depletion were restricted to p53 wildtype (wt) PDAC subtypes. Mechanistically, we illustrate that EZH2 blockade de-represses CDKN2A transcription for the subsequent posttranslational stabilization of p53wt expression and function. Together, our findings suggest an intact CDKN2A-p53wt axis as a prerequisite for the anti-tumorigenic consequences of EZH2 depletion and emphasize the significance of molecular stratification for the successful implementation of epigenetic targeting in PDAC.

Downregulation of the enhancer of zeste homolog 1 transcriptional factor predicts poor prognosis of triple-negative breast cancer patients

Background

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer and lacks effective biomarkers. This study seeks to unravel the expression status and the prospective transcriptional mechanisms of EZH1/EZH2 in TNBC tissue samples. Moreover, another objective of this study is to reveal the prognostic molecular signatures for risk stratification in TNBC patients.

Methods

To determine the expression status of EZH1/EZH2 in TNBC tissue samples, microarray analysis and immunohistochemistry were performed on in house breast cancer tissue samples. External mRNA expression matrices were used to verify its expression patterns. Furthermore, the prospective transcriptional mechanisms of EZH1/EZH2 in TNBC were explored by performing differential expression analysis, co-expression analysis, and chromatin immunoprecipitation sequencing analysis. Kaplan-Meier survival analysis and univariate Cox regression analysis were utilized to detect the prognostic molecular signatures in TNBC patients. Nomogram and time-dependent receiver operating characteristic curves were plotted to predict the risk stratification ability of the prognostic-signatures-based Cox model.

Results

In-house TMAs (66 TNBC vs. 106 non-TNBC) and external gene microarrays, as well as RNA-seq datasets (1,135 TNBC vs. 6,198 non-TNBC) results, confirmed the downregulation of EZH1 at both the protein and mRNA levels (SMD = -0.59 [-0.80, -0.37]), as is opposite to that of EZH2 (SMD = 0.74 [0.40, 1.08]). The upregulated transcriptional target genes of EZH1 were significantly aggregated in the cell cycle pathway, where CCNA2, CCNB1, MAD2L1, and PKMYT1 were determined as key transcriptional targets. Additionally, the downregulated transcriptional targets of EZH2 were enriched in response to the hormone, where ESR1 was identified as the hub gene. The six-signature-based prognostic model produced an impressive performance in this study, with a training AUC of 0.753, 0.981, and 0.977 at 3-, 5-, and 10-year survival probability, respectively.

Conclusion

EZH1 downregulation may be a key modulator in the progression of TNBC through negative transcriptional regulation by targeting CCNA2, CCNB1, MAD2L1, and PKMYT1.

DNMT1-mediated epigenetic silencing of TRAF6 promotes prostate cancer tumorigenesis and metastasis by enhancing EZH2 stability

A plethora of studies have shown that both DNMT1 and EZH2 have great effects on the progression of a variety of cancers. However, it remains unclear whether the expression profiles of these two epigenetic enzymes are molecularly intertwined in prostate cancer (PC), especially in castration-resistant prostate cancer (CRPC). Here, we found that DNMT1 is highly expressed and facilitates PC cell proliferation and migration. Importantly, we demonstrate that the abrogation of DNMT1 expression can induce the decreased expression of EZH2, resulting in the less aggressive capacity of PC cells. Mechanistically, we discovered that DNMT1 promotes PC tumorigenesis and metastasis by inhibiting TRAF6 transcriptional expression and subsequent TRAF6-mediated EZH2 ubiquitination. Finally, we confirmed that there is a negative correlation between DNMT1 and TRAF6 expression and a positive correlation between DNMT1 and EZH2 expression in PC patients. In this study, we first disclose that there is a direct crosstalk between DNA methyltransferase DNMT1 expression and histone methyltransferase EZH2 expression in tumorigenesis and cancer metastasis in vitro and in vivo. Our results also show that targeting DNMT1 with its inhibitor decitabine (an FDA-approved drug) is an appealing treatment strategy for CRPC patients through epigenetic suppression of both DNMT1-mediated DNA methylation and EZH2-modulated histone methylation.

Inhibition of polycomb repressive complex 2 by targeting EED protects against cisplatin-induced acute kidney injury

Polycomb repressive complex 2 (PRC2) is a multicomponent complex with methyltransferase activity that catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3). Interaction of the epigenetic reader protein EED with EZH2, a catalytic unit of PRC, allosterically stimulates PRC2 activity. In this study, we investigated the role and underlying mechanism of the PRC2 in acute kidney injury (AKI) by using EED226, a highly selective PRC2 inhibitor, to target EED. Administration of EED226 improved renal function, attenuated renal pathological changes, and reduced renal tubular cell apoptosis in a murine model of cisplatin‐induced AKI. In cultured renal epithelial cells, treatment with either EED226 or EED siRNA also ameliorated cisplatin‐induced apoptosis. Mechanistically, EED226 treatment inhibited cisplatin‐induced phosphorylation of p53 and FOXO3a, two transcriptional factors contributing to apoptosis, and preserved expression of Sirtuin 3 and PGC1α, two proteins associated with mitochondrial protection in vivo and in vitro. EED226 was also effective in enhancing renal tubular cell proliferation, suppressing expression of multiple inflammatory cytokines, and reducing infiltration of macrophages to the injured kidney. These data suggest that inhibition of the PRC2 activity by targeting EED can protect against cisplatin‐induced AKI by promoting the survival and proliferation of renal tubular cells and inhibiting inflammatory response.

3D chromatin architecture and transcription regulation in cancer

Chromatin has distinct three-dimensional (3D) architectures important in key biological processes, such as cell cycle, replication, differentiation, and transcription regulation. In turn, aberrant 3D structures play a vital role in developing abnormalities and diseases such as cancer. This review discusses key 3D chromatin structures (topologically associating domain, lamina-associated domain, and enhancer-promoter interactions) and corresponding structural protein elements mediating 3D chromatin interactions [CCCTC-binding factor, polycomb group protein, cohesin, and Brother of the Regulator of Imprinted Sites (BORIS) protein] with a highlight of their associations with cancer. We also summarise the recent development of technologies and bioinformatics approaches to study the 3D chromatin interactions in gene expression regulation, including crosslinking and proximity ligation methods in the bulk cell population (ChIA-PET and HiChIP) or single-molecule resolution (ChIA-drop), and methods other than proximity ligation, such as GAM, SPRITE, and super-resolution microscopy techniques.

Glioblastoma Stem Cells-Useful Tools in the Battle against Cancer

Glioblastoma stem cells (GSCs) are cells with a self-renewal ability and capacity to initiate tumors upon serial transplantation that have been linked to tumor cell heterogeneity. Most standard treatments fail to completely eradicate GSCs, causing the recurrence of the disease. GSCs could represent one reason for the low efficacy of cancer therapy and for the short relapse time. Nonetheless, experimental data suggest that the presence of therapy-resistant GSCs could explain tumor recurrence. Therefore, to effectively target GSCs, a comprehensive understanding of their biology and the survival and developing mechanisms during treatment is mandatory. This review provides an overview of the molecular features, microenvironment, detection, and targeting strategies of GSCs, an essential information required for an efficient therapy. Despite the outstanding results in oncology, researchers are still developing novel strategies, of which one could be targeting the GSCs present in the hypoxic regions and invasive edge of the glioblastoma.

Combining EGFR-TKI With SAHA Overcomes EGFR-TKI-Acquired Resistance by Reducing the Protective Autophagy in Non-Small Cell Lung Cancer

Nowadays, lung cancer has the highest mortality worldwide. The emergence of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has greatly improved the survival of patients with non-small cell lung cancer (NSCLC) having EGFR-TKI-sensitive mutations. Unfortunately, acquired resistance happens for most patients. In the present research, we found that EGFR-TKIs (such as gefitinib and osimertinib) can induce autophagy in NSCLC cell lines. Compared with parental sensitive cells, drug-resistant cells have higher autophagy activity. The use of an autophagy inhibitor could enhance the toxicity of gefitinib and osimertinib, which indicates that the enhancement of protective autophagy might be one of the mechanisms of EGFR-TKI resistance in NSCLC. In addition, increased autophagy activity is associated with decreased enhancer of zeste homolog 2 (EZH2) expression. Knockdown of EZH2 or EZH2 inhibitor treatment could lead to increased autophagy in NSCLC cells, indicating that EZH2 is a negative regulator of autophagy. We revealed that the increase in autophagy caused by the reduction of EZH2 was reversed in vitro and in vivo when combining gefitinib or osimertinib with suberoylanilide hydroxamic acid (SAHA), a broad-spectrum histone deacetylase inhibitor (HDACi). In conclusion, our results indicated that the combination of EGFR-TKIs and SAHA may be a new strategy to overcome EGFR-TKIs acquired resistance.

Post-Translational Modifications of BRD4: Therapeutic Targets for Tumor

Bromodomain-containing protein 4 (BRD4), a member of the bromodomain and extraterminal (BET) family, is considered to be a major driver of cancer cell growth and a new target for cancer therapy. Over 30 targeted inhibitors currently in preclinical and clinical trials have significant inhibitory effects on various tumors, including acute myelogenous leukemia (AML), diffuse large B cell lymphoma, prostate cancer, breast cancer and so on. However, resistance frequently occurs, revealing the limitations of BET inhibitor (BETi) therapy and the complexity of the BRD4 expression mechanism and action pathway. Current studies believe that when the internal and external environmental conditions of cells change, tumor cells can directly modify proteins by posttranslational modifications (PTMs) without changing the original DNA sequence to change their functions, and epigenetic modifications can also be activated to form new heritable phenotypes in response to various environmental stresses. In fact, research is constantly being supplemented with regards to that the regulatory role of BRD4 in tumors is closely related to PTMs. At present, the PTMs of BRD4 mainly include ubiquitination and phosphorylation; the former mainly regulates the stability of the BRD4 protein and mediates BETi resistance, while the latter is related to the biological functions of BRD4, such as transcriptional regulation, cofactor recruitment, chromatin binding and so on. At the same time, other PTMs, such as hydroxylation, acetylation and methylation, also play various roles in BRD4 regulation. The diversity, complexity and reversibility of posttranslational modifications affect the structure, stability and biological function of the BRD4 protein and participate in the occurrence and development of tumors by regulating the expression of tumor-related genes and even become the core and undeniable mechanism. Therefore, targeting BRD4-related modification sites or enzymes may be an effective strategy for cancer prevention and treatment. This review summarizes the role of different BRD4 modification types, elucidates the pathogenesis in the corresponding cancers, provides a theoretical reference for identifying new targets and effective combination therapy strategies, and discusses the opportunities, barriers, and limitations of PTM-based therapies for future cancer treatment.

Epigenetic, Metabolic, and Immune Crosstalk in Germinal-Center-Derived B-Cell Lymphomas: Unveiling New Vulnerabilities for Rational Combination Therapies

B-cell non-Hodgkin lymphomas (B-NHLs) are highly heterogenous by genetic, phenotypic, and clinical appearance. Next-generation sequencing technologies and multi-dimensional data analyses have further refined the way these diseases can be more precisely classified by specific genomic, epigenomic, and transcriptomic characteristics. The molecular and genetic heterogeneity of B-NHLs may contribute to the poor outcome of some of these diseases, suggesting that more personalized precision-medicine approaches are needed for improved therapeutic efficacy. The germinal center (GC) B-cell like diffuse large B-cell lymphomas (GCB-DLBCLs) and follicular lymphomas (FLs) share specific epigenetic programs. These diseases often remain difficult to treat and surprisingly do not respond advanced immunotherapies, despite arising in secondary lymphoid organs at sites of antigen recognition. Epigenetic dysregulation is a hallmark of GCB-DLBCLs and FLs, with gain-of-function (GOF) mutations in the histone methyltransferase EZH2, loss-of-function (LOF) mutations in histone acetyl transferases CREBBP and EP300, and the histone methyltransferase KMT2D representing the most prevalent genetic lesions driving these diseases. These mutations have the common effect to disrupt the interactions between lymphoma cells and the immune microenvironment, via decreased antigen presentation and responsiveness to IFN-γ and CD40 signaling pathways. This indicates that immune evasion is a key step in GC B-cell lymphomagenesis. EZH2 inhibitors are now approved for the treatment of FL and selective HDAC3 inhibitors counteracting the effects of CREBBP LOF mutations are under development. These treatments can help restore the immune control of GCB lymphomas, and may represent optimal candidate agents for more effective combination with immunotherapies. Here, we review recent progress in understanding the impact of mutant chromatin modifiers on immune evasion in GCB lymphomas. We provide new insights on how the epigenetic program of these diseases may be regulated at the level of metabolism, discussing the role of metabolic intermediates as cofactors of epigenetic enzymes. In addition, lymphoma metabolic adaptation can negatively influence the immune microenvironment, further contributing to the development of immune cold tumors, poorly infiltrated by effector immune cells. Based on these findings, we discuss relevant candidate epigenetic/metabolic/immune targets for rational combination therapies to investigate as more effective precision-medicine approaches for GCB lymphomas.

Chromatin-Independent Interplay of NFATc1 and EZH2 in Pancreatic Cancer

Background: The Nuclear Factor of Activated T-cells 1 (NFATc1) transcription factor and the methyltransferase Enhancer of Zeste Homolog 2 (EZH2) significantly contribute to the aggressive phenotype of pancreatic ductal adenocarcinoma (PDAC). Herein, we aimed at dissecting the mechanistic background of their interplay in PDAC progression. Methods: NFATc1 and EZH2 mRNA and protein expression and complex formation were determined in transgenic PDAC models and human PDAC specimens. NFATc1 binding on the Ezh2 gene and the consequences of perturbed NFATc1 expression on Ezh2 transcription were explored by Chromatin Immunoprecipitation (ChIP) and upon transgenic or siRNA-mediated interference with NFATc1 expression, respectively. Integrative analyses of RNA- and ChIP-seq data was performed to explore NFATc1-/EZH2-dependent gene signatures. Results: NFATc1 targets the Ezh2 gene for transcriptional activation and biochemically interacts with the methyltransferase in murine and human PDAC. Surprisingly, our genome-wide binding and expression analyses do not link the protein complex to joint gene regulation. In contrast, our findings provide evidence for chromatin-independent functions of the NFATc1:EZH2 complex and reveal posttranslational EZH2 phosphorylation at serine 21 as a prerequisite for robust complex formation. Conclusion: Our findings disclose a previously unknown NFATc1-EZH2 axis operational in the pancreas and provide mechanistic insights into the conditions fostering NFATc1:EZH2 complex formation in PDAC.

Insights into high-risk multiple myeloma from an analysis of the role of PHF19 in cancer

Despite  improvements in outcome, 15-25% of newly diagnosed multiple myeloma (MM) patients have treatment resistant high-risk (HR) disease with a poor survival. The lack of a genetic basis for HR has focused attention on the role played by epigenetic changes. Aberrant expression and somatic mutations affecting genes involved in the regulation of tri-methylation of the lysine (K) 27 on histone 3 H3 (H3K27me3) are common in cancer. H3K27me3 is catalyzed by EZH2, the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2). The deregulation of H3K27me3 has been shown to be involved in oncogenic transformation and tumor progression in a variety of hematological malignancies including MM. Recently we have shown that aberrant overexpression of the PRC2 subunit PHD Finger Protein 19 (PHF19) is the most significant overall contributor to HR status further focusing attention on the role played by epigenetic change in MM. By modulating both the PRC2/EZH2 catalytic activity and recruitment, PHF19 regulates the expression of key genes involved in cell growth and differentiation. Here we review the expression, regulation and function of PHF19 both in normal and the pathological contexts of solid cancers and MM. We present evidence that strongly implicates PHF19 in the regulation of genes important in cell cycle and the genetic stability of MM cells making it highly relevant to HR MM behavior. A detailed understanding of the normal and pathological functions of PHF19 will allow us to design therapeutic strategies able to target aggressive subsets of MM.

The Role of Protein SUMOylation in Human Hepatocellular Carcinoma: A Potential Target of New Drug Discovery and Development

Simple Summary

The small ubiquitin-like modifier is a highly conserved post-translational modification protein, mainly found in eukaryotes. Recently, studies have shown that SUMOylation promotes the development of liver cancer. This article summarises the recent literature on SUMOylation and Hepatocellular carcinoma (HCC). The mechanism of SUMOs in liver cancer cells was described. It also shows the potential of SUMO as a therapeutic target for liver cancer. At the same time, this article also enumerates the practical application in clinical, developing progress and future direction of HCC in clinical practice.

Abstract

Small ubiquitin-like modifier (SUMO) is a highly conserved post-translational modification protein, mainly found in eukaryotes. They are widely expressed in different tissues, including the liver. As an essential post-translational modification, SUMOylation is involved in many necessary regulations in cells. It plays a vital role in DNA repair, transcription regulation, protein stability and cell cycle progression. Increasing shreds of evidence show that SUMOylation is closely related to Hepatocellular carcinoma (HCC). The high expression of SUMOs in the inflammatory hepatic tissue may lead to the carcinogenesis of HCC. At the same time, SUMOs will upregulate the proliferation and survival of HCC, migration, invasion and metastasis of HCC, tumour microenvironment as well as drug resistance. This study reviewed the role of SUMOylation in liver cancer. In addition, it also discussed natural compounds that modulate SUMO and target SUMO drugs in clinical trials. Considering the critical role of SUMO protein in the occurrence of HCC, the drug regulation of SUMOylation may become a potential target for treatment, prognostic monitoring and adjuvant chemotherapy of HCC.

The Pivotal Immunomodulatory and Anti-Inflammatory Effect of Histone-Lysine N-Methyltransferase in the Glioma Microenvironment: Its Biomarker and Therapy Potentials

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase that encrypts a member of the Polycomb group (PcG) family. EZH2 forms a repressive chromatin structure which eventually participates in regulating the development as well as lineage propagation of stem cells and glioma progression. Posttranslational modifications are distinct approaches for the adjusted modification of EZH2 in the development of cancer. The amino acid succession of EZH2 protein makes it appropriate for covalent modifications, like phosphorylation, acetylation, O-GlcNAcylation, methylation, ubiquitination, and sumoylation. The glioma microenvironment is a dynamic component that comprises, besides glioma cells and glioma stem cells, a complex network that comprises diverse cell types like endothelial cells, astrocytes, and microglia as well as stromal components, soluble factors, and the extracellular membrane. EZH2 is well recognized as an essential modulator of cell invasion as well as metastasis in glioma. EZH2 oversecretion was implicated in the malfunction of several fundamental signaling pathways like Wnt/β-catenin signaling, Ras and NF-κB signaling, PI3K/AKT signaling, β-adrenergic receptor signaling, and bone morphogenetic protein as well as NOTCH signaling pathways. EZH2 was more secreted in glioblastoma multiforme than in low-grade gliomas as well as extremely secreted in U251 and U87 human glioma cells. Thus, the blockade of EZH2 expression in glioma could be of therapeutic value for patients with glioma. The suppression of EZH2 gene secretion was capable of reversing temozolomide resistance in patients with glioma. EZH2 is a promising therapeutic as well as prognostic biomarker for the treatment of glioma.

Curcumol inhibits malignant biological behaviors and TMZ-resistance in glioma cells by inhibiting long noncoding RNA FOXD2-As1-promoted EZH2 activation

Currently, conventional treatment is not sufficient to improve the survival of glioma patients. Hence, adopting novel personalized treatment programs is imperative. Curcumol, a Chinese herbal medicine extract from the roots of Rhizoma Curcumae, has attracted significant interest due to its beneficial pharmacological activities. The current study revealed that curcumol inhibited the proliferation, metastasis, self-renewal ability, and TMZ resistance in glioma cells in vitro and in vivo. Next, the potential molecular mechanisms of curcumol in inhibiting glioma were investigated. We found that the long non-coding RNA (lncRNA) FOXD2-As1 might contribute to the effects of curcumol on glioma cells. Enforced expression of FOXD2-As1 attenuated the curcumol-induced reduction in glioma cell proliferation, metastasis, self-renewal ability, and TMZ resistance. Moreover, the forced expression of FOXD2-As1 reversed the inhibitory effect of curcumol on the binding ability of EZH2 and H3K27me3 modification in the promoter regions of anti-oncogenes. Our results showed for the first time that curcumol is effective in inhibiting malignant biological behaviors and TMZ-resistance of glioma cells by suppressing FOXD2-As1-mediated EZH2 activation. Our study offers the possibility of exploiting curcumol as a promising therapeutic agent for glioma treatment and may provide an option for the clinical application of this natural herbal medicine.

The roles of epigenetics in cancer progression and metastasis

Cancer metastasis remains a major clinical challenge for cancer treatment. It is therefore crucial to understand how cancer cells establish and maintain their metastatic traits. However, metastasis-specific genetic mutations have not been identified in most exome or genome sequencing studies. Emerging evidence suggests that key steps of metastasis are controlled by reversible epigenetic mechanisms, which can be targeted to prevent and treat the metastatic disease. A variety of epigenetic mechanisms were identified to regulate metastasis, including the well-studied DNA methylation and histone modifications. In the past few years, large scale chromatin structure alterations including reprogramming of the enhancers and chromatin accessibility to the transcription factors were shown to be potential driving force of cancer metastasis. To dissect the molecular mechanisms and functional output of these epigenetic changes, it is critical to use advanced techniques and alternative animal models for interdisciplinary and translational research on this topic. Here we summarize our current understanding of epigenetic aberrations in cancer progression and metastasis, and their implications in developing new effective metastasis-specific therapies.

Emerging Roles of LncRNAs in the EZH2-regulated Oncogenic Network

Cancer is a life-threatening disease, but cancer therapies based on epigenetic mechanisms have made great progress. Enhancer of zeste homolog 2 (EZH2) is the key catalytic component of Polycomb repressive complex 2 (PRC2) that mediates the tri-methylation of lysine 27 on histone 3 (H3K27me3), a well-recognized marker of transcriptional repression. Mounting evidence indicates that EZH2 is elevated in various cancers and associates with poor prognosis. In addition, many studies revealed that EZH2 is also involved in transcriptional repression dependent or independent of PRC2. Meanwhile, long non-coding RNAs (lncRNAs) have been reported to regulate numerous and diverse signaling pathways in oncogenesis. In this review, we firstly discuss functional interactions between EZH2 and lncRNAs that determine PRC2-dependent and -independent roles of EZH2. Secondly, we summarize the lncRNAs regulating EZH2 expression at transcription, post-transcription and post-translation levels. Thirdly, we review several oncogenic pathways cooperatively regulated by lncRNAs and EZH2, including the Wnt/β-catenin and p53 pathways. In conclusion, lncRNAs play a key role in the EZH2-regulated oncogenic network with many fertile directions to be explored.

CHFR-mediated degradation of RNF126 confers sensitivity to PARP inhibitors in triple-negative breast cancer cells

Ring-finger protein 126 (RNF126), an E3 ubiquitin ligase, plays crucial roles in various biological processes, including cell proliferation, DNA damage repair, and intracellular vesicle trafficking. Whether RNF126 is modulated by posttranslational modifications is poorly understood. Here, we show that PARP1 interacts with and poly(ADP)ribosylates RNF126, which then recruits the PAR-binding E3 ubiquitin ligase CHFR to promote ubiquitination and degradation of RNF126. Moreover, RNF126 is required for the activation of ATR-Chk1 signaling induced by either irradiation (IR) or a PARP inhibitor (PARPi), and depletion of RNF126 increases the sensitivity of triple-negative breast cancer (TNBC) cells to PARPi treatment. Our findings suggest that PARPi-mediated upregulation of RNF126 protein stability contributes to TNBC cell resistance to PARPi. Therefore, targeting the E3 ubiquitin ligase RNF126 may be a novel treatment for overcoming the resistance of TNBC cells to PARPi in clinical trials.

EZH2 regulates the malignancy of human glioblastoma cells via modulation of Twist mRNA stability

Glioblastoma multiforme (GBM) is a lethal primary brain tumor with poor survival lifespan and dismal outcome. However, the effects and mechanisms of epigenetic factors on the development of GBM were still not well illustrated. We found that expression of enhancer of zeste homolog 2 (EZH2), which can catalyze histone H3K27me3 to modulate gene expression, was increased in GBM cells. Knockdown of EZH2 can suppress proliferation and migration, while increase temozolomide (TMZ) sensitivity, of GBM cells. Further, knockdown of EZH2 or its specific inhibitor GSK126 can decrease expression of Twist, while over expression of Twist can reverse si-EZH2-suppressed malignancy of GBM cells. Mechanistically, EZH2 can positively regulate mRNA stability of Twist1 mRNA. Further, miR-206, which can bind with 3'UTR of Twist1 mRNA, was involved in EZH2-regulated mRNA stability of Twist1. Collectively, our data suggest that EZH2 might be a potential target for GBM treatment. Further, miR-206/Twist axis is involved in EZH2-regulated malignancy of GBM cells.

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.