The noncanonical role of EZH2 in cancer

Epigallocatechin-3-gallate inhibit the protein arginine methyltransferase 5 and enhancer of Zeste homolog 2 in breast cancer both in vitro and in vivo

PURPOSE

Histone methyltransferases are enzymes that selectively methylate lysine or arginine residues on both histone and non-histone proteins, categorized into lysine methyltransferases and arginine methyltransferases. Notably, EZH2 and PRMT5 are known for catalyzing trimethylation of H3 at K27 and symmetric dimethylation of H4 at R3, respectively. These methylation events are recognized as characteristic histone-repressive marks in cancer. The over expression of PRMT5 and EZH2 were reported in various cancers and recognized as a drug target. The study aims to explore the inhibitory potential of phytocompound, Epigallocatechin-3-gallate (EGCG), against PRMT5 and EZH2 in the breast cancer model.

METHODS

Screening of an array of phytocompounds was conducted through a combination of in-silico and in-vitro assays. Interactions between EGCG and human PRMT5: MEP50 and EZH2 were evaluated using molecular docking. Binding efficiency was validated, by Surface Plasmon Resonance studies and inhibitory potential was accessed by in vitro methylation followed by western blots, ELISA, and cell-based assays. In-vivo efficacy of EGCG was carried on cell line derived mice xenograft model.

RESULTS

EGCG demonstrated robust interactions with PRMT5:MEP50 complex and EZH2, particularly within the SAM binding site. Surface Plasmon Resonance analysis revealed strong binding affinity in nanomolar concentrations, particularly with PRMT5-MEP50 compared to EZH2. In-vitro assays confirmed EGCG's ability to inhibit PRMT5 and EZH2, leading to a decrease in their catalytic products, namely H4R3me2s and H3K27me3, respectively. EGCG treatment induced both autophagy and apoptosis invitro. In-vivo studies demonstrated significant reductions in tumor size and the proliferation marker ki67, accompanied by a decrease in histone repressive marks.

CONCLUSION

The findings suggest that EGCG effectively inhibits PRMT5 and EZH2, underscoring its potential for combined therapeutic strategies in cancer treatment.

Engineered uterine primary myometrial cells with high-mobility group AT-hook 2 overexpression display a leiomyoma-like transcriptional and epigenomic phenotype

OBJECTIVE

To determine if engineered high-mobility group AT-hook 2 (HMGA2) overexpressing uterine primary myometrial cells recapitulate the transcriptional and epigenomic features of HMGA2-subtype leiomyomas.

DESIGN

Isolated primary, "normal" myometrial cells from three patients were engineered to overexpress HMGA2 to determine how HMGA2 establishes transcriptomic and epigenomic features of HMGA2-overexpressing leiomyoma.

SETTING

Academic research laboratory.

PATIENT(S)

Primary myometrial cells were isolated from normal myometrium obtained from three patients undergoing hysterectomy.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Determined genome-wide transcriptomic and epigenomic features of engineered HMGA2-overexpressing uterine primary myometrial cells.

RESULT(S)

Engineered HMGA2-V5-overexpressing primary myometrial cells approximated the HMGA2 expression level observed in HMGA2-overexpression subtype leiomyoma. High-mobility group AT-hook 2-V5 expression resulted in differential expression of 1,612 genes (false discovery rate [FDR] < 0.05) that were found to be enriched in pathways associated with leiomyoma formation, including extracellular matrix organization. Comparative gene expression analysis between HMGA2-V5 engineered primary cells and HMGA2-overexpression subtype leiomyoma revealed significant overlap of differentially expressed genes. Mechanistically, HMGA2-V5 overexpression resulted in 41,323 regions with differential H3K27ac deposition (FDR < 0.05) and 205,605 regions of altered chromatin accessibility (FDR < 0.05). Transcription factor binding site analysis implicated the AP-1 family of transcription factors.

CONCLUSION(S)

High-mobility group AT-hook 2 overexpression induces leiomyoma-like transcriptomic and epigenomic modulations in myometrial cells.

EZH2 Activates HTLV-1 bZIP Factor-Mediated TGF-β Signaling in Adult T-Cell Leukemia

Adult T-cell leukemia (ATL) is an aggressive malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) infection. Enhancer of zeste homolog 2 (EZH2) has been implicated in the development and progression of multiple cancers, including virus-induced malignancies. However, the potential function of EZH2 in HTLV-1-induced oncogenesis has not been clearly elucidated. In the present study, we showed that EZH2 was overexpressed and activated in HTLV-1-infected cell lines, potentially due to the activation of EZH2 promoter by HTLV-1 Tax and NF-κB p65 subunit. In addition, we found that EZH2 enhanced the HBZ-induced activation of TGF-β signaling in a histone methyltransferase-independent manner. As a mechanism for these actions, we found that EZH2 targeted Smad3/Smad4 to form a ternary complex, and the association between Smad3 and Smad4 was markedly enhanced in the presence of EZH2. Knockdown of EZH2 in ATL cells indeed repressed the expressions of the TGF-β target genes. In particular, EZH2 synergistically enhanced the HBZ/TGF-β-induced Foxp3 expression. Treatment of 3-Deazaneplanocin A, a specific inhibitor of EZH2 significantly inhibited the Foxp3 expression. Taken together, our results suggest that EZH2 may be involved in the differentiation of regulatory T cells through activating the HBZ-Smad3-TGF-β signaling axis, which is considered to be a key strategy for viral persistence.

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.

TRIM25, TRIM28 and TRIM59 and Their Protein Partners in Cancer Signaling Crosstalk: Potential Novel Therapeutic Targets for Cancer

Aberrant expression of TRIM proteins has been correlated with poor prognosis and metastasis in many cancers, with many TRIM proteins acting as key oncogenic factors. TRIM proteins are actively involved in many cancer signaling pathways, such as p53, Akt, NF-κB, MAPK, TGFβ, JAK/STAT, AMPK and Wnt/β-catenin. Therefore, this review attempts to summarize how three of the most studied TRIMs in recent years (i.e., TRIM25, TRIM28 and TRIM59) are involved directly and indirectly in the crosstalk between the signaling pathways. A brief overview of the key signaling pathways involved and their general cross talking is discussed. In addition, the direct interacting protein partners of these TRIM proteins are also highlighted in this review to give a picture of the potential protein-protein interaction that can be targeted for future discovery and for the development of novel therapeutics against cancer. This includes some examples of protein partners which have been proposed to be master switches to various cancer signaling pathways.

EZH2 mutation is associated with the development of visceral metastasis by enhancing proliferation and invasion and inhibiting apoptosis in breast cancer cells

BACKGROUND

The prognosis of breast cancer patients with visceral metastasis (VM) is significantly worse than that of patients without VM. We aimed to evaluate EZH2 (enhancer of zeste homolog 2) mutation as a biomarker associated with VM.

METHODS

Data from forty-nine patients with metastatic breast cancer (MBC) pathologically confirmed at our hospital between March 2016 and September 2018 were collected. Metastatic tissue samples were obtained via ultrasound-guided needle biopsy, and paired peripheral blood samples were also collected. Tissue and blood samples were subjected to targeted next-generation sequencing via a 247-gene panel. Stably transfected MDA-MB-231 cells expressing wild-type EZH2 (EZH2WT) or a mutant form of EZH2 (EZH2K515R) were generated. Cell proliferation, colony formation ability, migration and invasion abilities and apoptosis were assessed using CCK-8 assays, plate colony formation assays, Transwell chamber assays and flow cytometry.

RESULTS

The incidence of EZH2 mutations in the VM subgroup was greater than that in the non-VM subgroup in the entire cohort (n = 49, 42.3% vs. 13.0%, p = 0.024) and in the triple-negative breast cancer (TNBC) subgroup (n = 20, 50.0% vs. 10.0%, p = 0.05). Patients carrying EZH2 mutations had a significantly greater risk of developing VM than did those in the non-EZH2 mutation group in the entire cohort (HR 2.9) and in the TNBC subgroup (HR 6.45). Multivariate analysis revealed that EZH2 mutation was an independent prognostic factor for VM (HR 2.99, p = 0.009) in the entire cohort and in the TNBC subgroup (HR 10.1, p = 0.006). Data from cBioPortal also showed that patients with EZH2 mutations had a significantly greater risk of developing VM (HR 3.1), and the time to develop VM was significantly earlier in the EZH2 mutation group (31.5 months vs. 109.7 months, p = 0.008). Multivariate analysis revealed that EZH2 mutation (HR 2.73, p = 0.026) was an independent factor for VM after breast cancer surgery. There was no correlation between EZH2 mutations and BRCA1/2 mutations. Most of the patients (81.8%) in our cohort who developed VM carried the "c.1544A > G (p.K515R)" mutation. Compared with EZH2WT MDA-MB-231 cells, EZH2K515R MDA-MB-231 cells had greater colony formation rates (p < 0.01), greater migration and invasion rates (p < 0.001), and lower apoptosis rates (p < 0.01). The proportion of S + G2/M phase cells in the EZH2K515R group was significantly greater than that in the EZH2WT group.

CONCLUSIONS

EZH2 mutation is associated with VM development in breast cancer patients. The EZH2K515R mutation leads to VM and a poor prognosis by enhancing proliferation and invasion and inhibiting apoptosis in breast cancer cells.

UNSEG: unsupervised segmentation of cells and their nuclei in complex tissue samples

Multiplexed imaging technologies have made it possible to interrogate complex tissue microenvironments at sub-cellular resolution within their native spatial context. However, proper quantification of this complexity requires the ability to easily and accurately segment cells into their sub-cellular compartments. Within the supervised learning paradigm, deep learning-based segmentation methods demonstrating human level performance have emerged. However, limited work has been done in developing such generalist methods within the unsupervised context. Here we present an easy-to-use unsupervised segmentation (UNSEG) method that achieves deep learning level performance without requiring any training data via leveraging a Bayesian-like framework, and nucleus and cell membrane markers. We show that UNSEG is internally consistent and better at generalizing to the complexity of tissue morphology than current deep learning methods, allowing it to unambiguously identify the cytoplasmic compartment of a cell, and localize molecules to their correct sub-cellular compartment. We also introduce a perturbed watershed algorithm for stably and automatically segmenting a cluster of cell nuclei into individual nuclei that increases the accuracy of classical watershed. Finally, we demonstrate the efficacy of UNSEG on a high-quality annotated gastrointestinal tissue dataset we have generated, on publicly available datasets, and in a range of practical scenarios.

The Mutational and Microenvironmental Landscape of Cutaneous Squamous Cell Carcinoma: A Review

Cutaneous squamous cell carcinoma (cSCC) manifests through the complex interactions of UV-induced DNA damage, genetic mutations, and alterations in the tumor microenvironment. A high mutational burden is present in cSCC, as well as both cSCC precursors and normal skin, making driver genes difficult to differentiate. Despite this, several key driver genes have been identified, including TP53, the NOTCH family, CDKN2A, PIK3CA, and EGFR. In addition to mutations, the tumor microenvironment and the manipulation and evasion of the immune system play a critical role in cSCC progression. Novel therapeutic approaches, such as immunotherapy and EGFR inhibitors, have been used to target these dysregulations, and have shown promise in treating advanced cSCC cases, emphasizing the need for targeted interventions considering both genetic and microenvironmental factors for improved patient outcomes.

YTHDF1 promotes the osteolytic bone metastasis of breast cancer via inducing EZH2 and CDH11 translation

Bone metastasis is common in breast cancer and more effective therapies are required, however, its molecular mechanism is poorly understood. Additionally, the role of the m6A reader YTHDF1 in bone metastasis of breast cancer has not been reported. Here, we reveal that the increased expression of YTHDF1 is clinically correlated with breast cancer bone metastases. YTHDF1 promotes migration, invasion, and osteoblast adhesion and induces osteoclast differentiation of cancer cells in vitro and vivo. Mechanically, RNA-seq, MeRIP-seq and RIP-seq analysis, and molecular biology experiments demonstrate that YTHDF1 translationally enhances EZH2 and CDH11 expression by reading m6A-enriched sites of their transcripts. Moreover, adeno-associated virus (AAV) was used to deliver shYTHDF1 (shYTHDF1-AAV) in intratibial injection models, eliciting a significant suppressive effect on breast cancer bone metastatic formation and osteolytic destruction. Overall, we uncovered that YTHDF1 promotes osteolytic bone metastases of breast cancer by inducing EZH2 and CDH11 translation.

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.

PROTACs targeting androgen receptor signaling: Potential therapeutic agents for castration-resistant prostate cancer

After the initial androgen deprivation therapy (ADT), part of the prostate cancer may continuously deteriorate into castration-resistant prostate cancer (CRPC). The majority of patients suffer from the localized illness at primary diagnosis that could rapidly assault other organs. This disease stage is referred as metastatic castration-resistant prostate cancer (mCRPC). Surgery and radiation are still the treatment of CRPC, but have some adverse effects such as urinary symptoms and sexual dysfunction. Hormonal castration therapy interfering androgen receptor (AR) signaling pathway is indispensable for most advanced prostate cancer patients, and the first- and second-generation of novel AR inhibitors could effectively cure hormone sensitive prostate cancer (HSPC). However, the resistance to these chemical agents is inevitable, so many of patients may experience relapses. The resistance to AR inhibitor mainly involves AR mutation, splice variant formation and amplification, which indicates the important role in CRPC. Proteolysis-targeting chimera (PROTAC), a potent technique to degrade targeted protein, has recently undergone extensive development as a biological tool and therapeutic drug. This technique has the potential to become the next generation of antitumor therapeutics as it could overcome the shortcomings of conventional small molecule inhibitors. In this review, we summarize the molecular mechanisms on PROTACs targeting AR signaling for CRPC, hoping to provide insights into drug development and clinical medication.

Prediction and assessment of deleterious and disease causing nonsynonymous single nucleotide polymorphisms (nsSNPs) in human FOXP4 gene: An in - silico study

In humans, FOXP gene family is involved in embryonic development and cancer progression. The FOXP4 (Forkhead box protein P4) gene belongs to this FOXP gene family. FOXP4 gene plays a crucial role in oncogenesis. Single nucleotide polymorphisms are biological markers and common determinants of human diseases. Mutations can largely affect the function of the corresponding protein. Therefore, the molecular mechanism of nsSNPs in the FOXP4 gene needs to be elucidated. Initially, the SNPs of the FOXP4 gene were extracted from the dbSNP database and a total of 23124 SNPs was found, where 555 nonsynonymous, 20525 intronic, 1114 noncoding transcript, 334 synonymous were obtained and the rest were unspecified. Then, a series of bioinformatics tools (SIFT, PolyPhen2, SNAP2, PhD SNP, PANTHER, I-Mutant2.0, MUpro, GOR IV, ConSurf, NetSurfP 2.0, HOPE, DynaMut2, GeneMANIA, STRING and Schrodinger) were used to explore the effect of nsSNPs on FOXP4 protein function and structural stability. First, 555 nsSNPs were analyzed using SIFT, of which 57 were found as deleterious. Following, PolyPhen2, SNAP2, PhD SNP and PANTHER analyses, 10 nsSNPs (rs372762294, rs141899153, rs142575732, rs376938850, rs367607523, rs112517943, rs140387832, rs373949416, rs373949416 and rs376160648) were common and observed as deleterious, damaging and diseases associated. Following that, using I-Mutant2.0 and MUpro servers, 7 nsSNPs were found to be the most unstable. GOR IV predicted that these seven nsSNPs affect protein structure by altering the protein contents of alpha helixes, extended strands, and random coils. Following DynaMut2, 5 nsSNPs showed a decrease in the ΔΔG value compared with the wild-type and were found to be responsible for destabilizing the corresponding protein. GeneMANIA and STRING network revealed interaction of FOXP4 with other genes. Finally, molecular dynamics simulation analysis revealed consistent fluctuation in RMSD and RMSF values, Rg and hydrogen bonds in the mutant proteins compared with WT, which might alter the functional and structural stability of the corresponding protein. As a result, the aforementioned integrated comprehensive bioinformatic analyses provide insight into how various nsSNPs of the FOXP4 gene change the structural and functional properties of the corresponding protein, potentially proceeding with the pathophysiology of human diseases.

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.

Targeting EED as a key PRC2 complex mediator toward novel epigenetic therapeutics

EED within the PRC2 complex is crucial for chromatin regulation particularly in tumor development, making its inhibition a promising epigenetic therapeutic strategy. Significant advancement in PRC2 inhibitor development has been achieved with an approved EZH2 inhibitor in the market and with others in the clinical trials. However, current EZH2 inhibitors are limited to specific blood cancers and encounter therapeutic resistance. EED stabilizes PRC2 complex and enhances its activity through unique allosteric mechanisms, thereby acting as both a scaffold protein and a recognizer of H3K27me3 making it an attractive drug target. This review provides an overview of epigenetic therapeutic strategies targeting EED, including allosteric inhibitors, PPI inhibitors, and PROTACs, together with brief discussions on the relevant challenges, opportunities, and future directions.

Unveiling Gambogenic Acid as a Promising Antitumor Compound: A Review

Gambogenic acid is a derivative of gambogic acid, a polyprenylated xanthone isolated from Garcinia hanburyi. Compared with the more widely studied gambogic acid, gambogenic acid has demonstrated advantages such as a more potent antitumor effect and less systemic toxicity than gambogic acid according to early investigations. Therefore, the present review summarizes the effectiveness and mechanisms of gambogenic acid in different cancers and highlights the mechanisms of action. In addition, drug delivery systems to improve the bioavailability of gambogenic acid and its pharmacokinetic profile are included. Gambogenic acid has been applied to treat a wide range of cancers, such as lung, liver, colorectal, breast, gastric, bladder, and prostate cancers. Gambogenic acid exerts its antitumor effects as a novel class of enhancer of zeste homolog 2 inhibitors. It prevents cancer cell proliferation by inducing apoptosis, ferroptosis, and necroptosis and controlling the cell cycle as well as autophagy. Gambogenic acid also hinders tumor cell invasion and metastasis by downregulating metastasis-related proteins. Moreover, gambogenic acid increases the sensitivity of cancer cells to chemotherapy and has shown effects on multidrug resistance in malignancy. This review adds insights for the prevention and treatment of cancers using gambogenic acid.

UNSEG: unsupervised segmentation of cells and their nuclei in complex tissue samples

Multiplexed imaging technologies have made it possible to interrogate complex tumor microenvironments at sub-cellular resolution within their native spatial context. However, proper quantification of this complexity requires the ability to easily and accurately segment cells into their sub-cellular compartments. Within the supervised learning paradigm, deep learning based segmentation methods demonstrating human level performance have emerged. However, limited work has been done in developing such generalist methods within the label-free unsupervised context. Here we present an unsupervised segmentation (UNSEG) method that achieves deep learning level performance without requiring any training data. UNSEG leverages a Bayesian-like framework and the specificity of nucleus and cell membrane markers to construct an a posteriori probability estimate of each pixel belonging to the nucleus, cell membrane, or background. It uses this estimate to segment each cell into its nuclear and cell-membrane compartments. We show that UNSEG is more internally consistent and better at generalizing to the complexity of tissue morphology than current deep learning methods. This allows UNSEG to unambiguously identify the cytoplasmic compartment of a cell, which we employ to demonstrate its use in an exemplar biological scenario. Within the UNSEG framework, we also introduce a new perturbed watershed algorithm capable of stably and automatically segmenting a cluster of cell nuclei into individual cell nuclei that increases the accuracy of classical watershed. Perturbed watershed can also be used as a standalone algorithm that researchers can incorporate within their supervised or unsupervised learning approaches to extend classical watershed, particularly in the multiplexed imaging context. Finally, as part of developing UNSEG, we have generated a high-quality annotated gastrointestinal tissue (GIT) dataset, which we anticipate will be useful for the broader research community. We demonstrate the efficacy of UNSEG on the GIT dataset, publicly available datasets, and on a range of practical scenarios. In these contexts, we also discuss the possibility of bias inherent in quantification of segmentation accuracy based on F 1 score. Segmentation, despite its long antecedents, remains a challenging problem, particularly in the context of tissue samples. UNSEG, an easy-to-use algorithm, provides an unsupervised approach to overcome this bottleneck, and as we discuss, can help improve deep learning based segmentation methods by providing a bridge between unsupervised and supervised learning paradigms.

Iron overload increases the sensitivity of endometriosis stromal cells to ferroptosis via a PRC2-independent function of EZH2

Given the high concentration of iron in the micro-environment of ovarian endometriosis, it is plausible to hypothesize that ectopic endometrial cells may be more susceptible to undergoing ferroptosis. Manipulation of ferroptosis has been explored as a potential therapeutic strategy to treat related diseases. In this study, we examined the impact on ectopic endometrial stromal cells (EESCs) of iron overload and an inducer of ferroptosis. We found that the iron concentration in the ovarian endometriosis was much higher than control samples. Treatment of cultured EESCs with ferric ammonium citrate (FAC) increase the sensitivity to undergo ferroptosis. By analyzing the RNA-seq results, it was discovered that zeste 2 polycomb repressive complex 2 subunit (EZH2) was significantly downregulated in ferroptosis induced EESCs. Moreover, overexpression of EZH2 effectively prevented the induction of ferroptosis. In addition, the activity or expression of EZH2 is directly and specifically inhibited by the methyltransferase inhibitor GSK343, which raises the sensitivity of stromal cells to ferroptosis. Taken together, our findings revealed that EZH2 act as a suppressor in the induced cell ferroptosis through a PRC2-independent methyltransferase mechanism. Therefore, blocking EZH2 expression and inducing ferroptosis may be effective treatment approaches for ovarian endometriosis.

EZH2-mediated development of therapeutic resistance in cancer

Enhancer of zeste homolog 2 (EZH2) regulates gene expression and plays a definite role in cell proliferation, apoptosis, and senescence. Overexpression of EZH2 has been found in various human malignancies, including prostate, breast, and ovarian cancers, and is associated with increased metastasis and poor prognosis. EZH2 catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) as a canonical role in a PRC2-dependent manner. This mechanism silences various tumor suppressor genes through EZH2-mediated histone lysine methyltransferase activity. As a non-canonical role, EZH2 partners with other signaling molecules to undergo post-translational modification to orchestrate its function as a co-activator playing a critical role in cancer progression. Dysregulation of EZH2 has also been associated with therapeutic resistance in cancer cells. Given the role of EZH2 in promoting carcinogenesis and therapy resistance, both canonical and non-canonical EZH2 inhibitors have been used to combat multiple cancer types. Moreover, combining EZH2 inhibitors with other therapeutic modalities have shown to enhance the therapeutic efficacy and overcome potential resistance mechanisms in these cancerous cells. Therefore, targeting EZH2 through canonical and non-canonical modes appears to be a promising therapeutic strategy to enhance efficacy and overcome resistance in multiple cancers.

EZH2 is a key component of hepatoblastoma tumor cell growth

BACKGROUND

Enhancer of zeste homolog 2 (EZH2) catalyzes the trimethylation of histone H3 at lysine 27 via the polycomb recessive complex 2 (PRC2) and plays a time-specific role in normal fetal liver development. EZH2 is overexpressed in hepatoblastoma (HB), an embryonal tumor. EZH2 can also promote tumorigenesis via a noncanonical, PRC2-independent mechanism via proto-oncogenic, direct protein interaction, including β-catenin. We hypothesize that the pathological activation of EZH2 contributes to HB propagation in a PRC2-independent manner.

METHODS AND RESULTS

We demonstrate that EZH2 promotes proliferation in HB tumor-derived cell lines through interaction with β-catenin. Although aberrant EZH2 expression occurs, we determine that both canonical and noncanonical EZH2 signaling occurs based on specific gene-expression patterns and interaction with SUZ12, a PRC2 component, and β-catenin. Silencing and inhibition of EZH2 reduce primary HB cell proliferation.

CONCLUSIONS

EZH2 overexpression promotes HB cell proliferation, with both canonical and noncanonical function detected. However, because EZH2 directly interacts with β-catenin in human tumors and EZH2 overexpression is not equal to SUZ12, it seems that a noncanonical mechanism is contributing to HB pathogenesis. Further mechanistic studies are necessary to elucidate potential pathogenic downstream mechanisms and translational potential of EZH2 inhibitors for the treatment of HB.

Integrated scRNAseq analyses of mouse cochlear supporting cells reveal the involvement of Ezh2 in hair cell regeneration

BACKGROUND

In lower vertebrates like fish, the inner ear and lateral line hair cells (HCs) can regenerate after being damaged by proliferation/differentiation of supporting cells (SCs). However, the HCs of mouse cochlear could only regenerate within one to two weeks after birth but not for adults.

METHODS AND RESULTS

To better understand the molecular foundations, we collected several public single-cell RNA sequencing (scRNAseq) data of mouse cochleae from E14 to P33 and extracted the prosensory and supporting cells specifically. Gene Set Enrichment Analysis (GSEA) results revealed a down-regulation of genes in Notch signaling pathway during postnatal stages (P7 and P33). We also identified 107 time-course co-expression genes correlated with developmental stage and predicated that EZH2 and KLF15 may be the key transcriptional regulators for these genes. Expressions of candidate target genes of EZH2 and KLF15 were also found in supporting cells of the auditory epithelia in chick and the neuromasts in zebrafish. Furthermore, inhibiting EZH2 suppressed regeneration of hair cells in zebrafish neuromasts and altered expressions of some developmental stage correlated genes.

CONCLUSIONS

Our results extended the understanding for molecular basis of hair cell regeneration ability and revealed the potential role of Ezh2 in it.

Methyltransferase-independent function of enhancer of zeste homologue 2 maintains tumorigenicity induced by human oncogenic papillomavirus and polyomavirus

Merkel cell polyomavirus (MCV) and high-risk human papillomavirus (HPV) are human tumor viruses that cause Merkel cell carcinoma (MCC) and oropharyngeal squamous cell carcinoma (OSCC), respectively. HPV E7 and MCV large T (LT) oncoproteins target the retinoblastoma tumor suppressor protein (pRb) through the conserved LxCxE motif. We identified enhancer of zeste homolog 2 (EZH2) as a common host oncoprotein activated by both viral oncoproteins through the pRb binding motif. EZH2 is a catalytic subunit of the polycomb 2 (PRC2) complex that trimethylates histone H3 at lysine 27 (H3K27me3). In MCC tissues EZH2 was highly expressed, irrespective of MCV status. Loss-of-function studies revealed that viral HPV E6/E7 and T antigen expression are required for Ezh2 mRNA expression and that EZH2 is essential for HPV(+)OSCC and MCV(+)MCC cell growth. Furthermore, EZH2 protein degraders reduced cell viability efficiently and rapidly in HPV(+)OSCC and MCV(+)MCC cells, whereas EZH2 histone methyltransferase inhibitors did not affect cell proliferation or viability within the same treatment period. These results suggest that a methyltransferase-independent function of EZH2 contributes to tumorigenesis downstream of two viral oncoproteins, and that direct targeting of EZH2 protein expression could be a promising strategy for the inhibition of tumor growth in HPV(+)OSCC and MCV(+)MCC patients.

Knockdown of Bach1 protects periodontal bone regeneration from inflammatory damage

Periodontal bone regeneration is a major challenge in the treatment of periodontitis. However, the regenerative vitality of periodontal ligament cells (PDLCs) declines in the environment of periodontitis and accompanying oxidative stress. This study aimed to investigate the functional mechanisms of Bach1, a transcriptional suppressor involved in oxidative stress response, and its regulation of PDLC osteogenesis under inflammatory conditions. We observed a significant elevation in Bach1 expression in periodontal tissues with periodontitis and PDLCs under inflammatory conditions. Knockdown of Bach1 alleviated the inflammation-induced oxidative stress level and partly offset the inhibitory effect of inflammatory conditions on osteogenesis, as well as the expression of osteogenic genes BMP6, OPG and RUNX2. Similarly, knockdown of Bach1 protects PDLCs from inflammatory damage to periodontal bone regeneration in vivo. Furthermore, we found that Bach1 could bind to the histone methyltransferase EZH2, and the binding increased under inflammatory conditions. Bach1 enhanced the ability of EZH2 to catalyse H3K27me3 on the promoter region of RUNX2 and BMP6, thus repressing the expression of osteoblastic genes. In conclusion, our study revealed that knockdown of Bach1 effectively rescued the osteogenesis and oxidative stress of PDLCs with inflammation. Bach1 could be a promising target for enhancing periodontal tissue regeneration under periodontitis conditions.

Oncoviruses: How do they hijack their host and current treatment regimes

Viruses have the ability to modulate the cellular machinery of their host to ensure their survival. While humans encounter numerous viruses daily, only a select few can lead to disease progression. Some of these viruses can amplify cancer-related traits, particularly when coupled with factors like immunosuppression and co-carcinogens. The global burden of cancer development resulting from viral infections is approximately 12%, and it arises as an unfortunate consequence of persistent infections that cause chronic inflammation, genomic instability from viral genome integration, and dysregulation of tumor suppressor genes and host oncogenes involved in normal cell growth. This review provides an in-depth discussion of oncoviruses and their strategies for hijacking the host's cellular machinery to induce cancer. It delves into how viral oncogenes drive tumorigenesis by targeting key cell signaling pathways. Additionally, the review discusses current therapeutic approaches that have been approved or are undergoing clinical trials to combat malignancies induced by oncoviruses. Understanding the intricate interactions between viruses and host cells can lead to the development of more effective treatments for virus-induced cancers.

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.

Review: Targeting EZH2 in neuroblastoma

Neuroblastoma is one of the commonest extra-cranial pediatric tumors, and accounts for over 15% of all childhood cancer mortality. Risk stratification for children with neuroblastoma is based on age, stage, histology, and tumor cytogenetics. The majority of patients are considered to have high-risk neuroblastoma, for which the long-term survival is less than 50%. Current treatments combine surgical resection, chemotherapy, stem cell transplantation, radiotherapy, anti-GD2 based immunotherapy as well as the differentiating agent isotretinoin. Despite the intensive multimodal therapies applied, there are high relapse rates, and recurrent disease is often resistant to further therapy. Enhancer of Zeste Homolog 2 (EZH2), a catalytic subunit of Polycomb Repressive Complex 2 (PRC2), is a histone methyltransferase that represses transcription through trimethylation of lysine residue K27 on histone H3 (H3K27me3). It is responsible for epigenetic repression of transcription, making EZH2 an essential regulator for cell differentiation. Overexpression of EZH2 has been shown to promote tumorigenesis, cancer cell proliferation and prevent tumor cells from differentiating in a number of cancers. Therefore, research has been ongoing for the past decade, developing treatments that target EZH2 in neuroblastoma. This review summarises the role of EZH2 in neuroblastoma and evaluates the latest research findings on the therapeutic potential of targeting EZH2 in the treatment of neuroblastoma.

EZH2 activates Wnt/β-catenin signaling in human uterine fibroids, which is inhibited by the natural compound methyl jasmonate

OBJECTIVE

To investigate the link between EZH2 and Wnt/β-catenin signaling and its role in uterine fibroids (UFs) pathogenesis and explore the potential effect of natural compound methyl jasmonate (MJ) against UFs.

DESIGN

EZH2 overexpression or inhibition was achieved in human uterine leiomyoma (HuLM) cells using EZH2-expressing adenovirus or chemical EZH2 inhibitor (DZNep), respectively. The HuLM and normal uterine smooth muscle cells were treated with 0.1-3 mM of MJ, and several experiments were employed.

SETTING

Laboratory study.

PATIENTS(S)

None.

INTERVENTION(S)

Methyl jasmonate.

MAIN OUTCOME MEASURE(S)

Protein expression of EZH2, β-catenin, and proliferating cell nuclear antigen (PCNA) was measured by Western blot as well as gene expression alterations of Wnt ligands (Wnt5A, Wnt5b, and Wnt9A), WISP1, CTNNB1, and its responsive gene PITX2 using quantitative real-time polymerase chain reaction. The protein and ribonucleic acid (RNA) levels of several markers were measured in MJ-treated or untreated HuLM cells, including EZH2 and β-catenin, extracellular matrix markers collagen type 1 (COL1A1) and fibronectin (FN), proliferation markers cyclin D1 (CCND1) and PCNA, tumor suppressor marker p21, and apoptotic markers (BAX, cytochrome c, and cleaved caspase 3).

RESULT(S)

EZH2 overexpression significantly increased the gene expression of several Wnt ligands (PITX2, WISP1, WNT5A, WNT5B, and WNT9A), which increased nuclear translocation of β-catenin and PCNA and eventually HuLM cell proliferation. EZH2 inhibition blocked Wnt/β-catenin signaling activation where the aforementioned genes significantly decreased as well as PCNA, cyclin D1, and PITX2 protein expression compared with those in untreated HuLM. Methyl jasmonate showed a potent antiproliferative effect on HuLM cells in a dose- and time-dependent manner. Interestingly, the dose range (0.1-0.5 mM) showed a selective growth inhibitory effect on HuLM cells, not on normal uterine smooth muscle cells. Methyl jasmonate treatment at 0.5 mM for 24 hours significantly decreased both protein and RNA levels of EZH2, β-catenin, COL1A1, FN, CCND1, PCNA, WISP1, and PITX2 but increased the protein levels of p21, BAX, cytochrome, c and cleaved caspase 3 compared with untreated HuLM. Methyl jasmonate-treated cells exhibited down-regulation in the RNA expression of 36 genes, including CTNNB1, CCND1, Wnt5A, Wnt5B, and Wnt9A, and up-regulation in the expression of 34 genes, including Wnt antagonist genes WIF1, PRICKlE1, and DKK1 compared with control, confirming the quantitative real-time polymerase chain reaction results.

CONCLUSION(S)

Our studies provide a novel link between EZH2 and the Wnt/β-catenin signaling pathway in UFs. Targeting EZH2 with MJ interferes with the activation of wnt/β-catenin signaling in our model. Methyl jasmonate may offer a promising therapeutic option as a nonhormonal and cost-effective treatment against UFs with favorable clinical utility, pending proven safe and efficient in human clinical trials.

Fibrosis-the tale of H3K27 histone methyltransferases and demethylases

Fibrosis, or excessive scarring, is characterized by the emergence of alpha-smooth muscle actin (αSMA)-expressing myofibroblasts and the excessive accumulation of fibrotic extracellular matrix (ECM). Currently, there is a lack of effective treatment options for fibrosis, highlighting an unmet need to identify new therapeutic targets. The acquisition of a fibrotic phenotype is associated with changes in chromatin structure, a key determinant of gene transcription activation and repression. The major repressive histone mark, H3K27me3, has been linked to dynamic changes in gene expression in fibrosis through alterations in chromatin structure. H3K27-specific homologous histone methylase (HMT) enzymes, Enhancer of zeste 1 and 2 (EZH1, EZH2), which are the alternative subunits of the Polycomb Repressive Complex 2 (PRC2) and demethylase (KDM) enzymes, Ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX), and Lysine demethylase 6B (KDM6B), are responsible for regulating methylation status of H3K27me3. In this review, we explore how these key enzymes regulate chromatin structure to alter gene expression in fibrosis, highlighting them as attractive targets for the treatment of fibrosis.

Post-translational modifications of histones: Mechanisms, biological functions, and therapeutic targets

Histones are DNA-binding basic proteins found in chromosomes. After the histone translation, its amino tail undergoes various modifications, such as methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, and lactylation, which together constitute the "histone code." The relationship between their combination and biological function can be used as an important epigenetic marker. Methylation and demethylation of the same histone residue, acetylation and deacetylation, phosphorylation and dephosphorylation, and even methylation and acetylation between different histone residues cooperate or antagonize with each other, forming a complex network. Histone-modifying enzymes, which cause numerous histone codes, have become a hot topic in the research on cancer therapeutic targets. Therefore, a thorough understanding of the role of histone post-translational modifications (PTMs) in cell life activities is very important for preventing and treating human diseases. In this review, several most thoroughly studied and newly discovered histone PTMs are introduced. Furthermore, we focus on the histone-modifying enzymes with carcinogenic potential, their abnormal modification sites in various tumors, and multiple essential molecular regulation mechanism. Finally, we summarize the missing areas of the current research and point out the direction of future research. We hope to provide a comprehensive understanding and promote further research in this field.

Modulation of EZH2 Activity Induces an Antitumoral Effect and Cell Redifferentiation in Anaplastic Thyroid Cancer

Anaplastic thyroid cancer (ATC) is a rare and lethal form of thyroid cancer that requires urgent investigation of new molecular targets involved in its aggressive biology. In this context, the overactivation of Polycomb Repressive Complex 2/EZH2, which induces chromatin compaction, is frequently observed in aggressive solid tumors, making the EZH2 methyltransferase a potential target for treatment. However, the deregulation of chromatin accessibility is yet not fully investigated in thyroid cancer. In this study, EZH2 expression was modulated by CRISPR/Cas9-mediated gene editing and pharmacologically inhibited with EZH2 inhibitor EPZ6438 alone or in combination with the MAPK inhibitor U0126. The results showed that CRISPR/Cas9-induced EZH2 gene editing reduced cell growth, migration and invasion in vitro and resulted in a 90% reduction in tumor growth when EZH2-edited cells were injected into an immunocompromised mouse model. Immunohistochemistry analysis of the tumors revealed reduced tumor cell proliferation and less recruitment of cancer-associated fibroblasts in the EZH2-edited tumors compared to the control tumors. Moreover, EZH2 inhibition induced thyroid-differentiation genes' expression and mesenchymal-to-epithelial transition (MET) in ATC cells. Thus, this study shows that targeting EZH2 could be a promising neoadjuvant treatment for ATC, as it promotes antitumoral effects in vitro and in vivo and induces cell differentiation.

Dual inhibition of EZH2 and G9A/GLP histone methyltransferases by HKMTI-1-005 promotes differentiation of acute myeloid leukemia cells

All-trans-retinoic acid (ATRA)-based differentiation therapy of acute promyelocytic leukemia (APL) represents one of the most clinically effective examples of precision medicine and the first example of targeted oncoprotein degradation. The success of ATRA in APL, however, remains to be translated to non-APL acute myeloid leukemia (AML). We previously showed that aberrant histone modifications, including histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) methylation, were associated with this lack of response and that epigenetic therapy with small molecule inhibitors of the H3K4 demethylase LSD1/KDM1A could reprogram AML cells to respond to ATRA. Serving as the enzymatic component of Polycomb Repressive Complex 2, EZH2/KMT6A methyltransferase plays a critical role in normal hematopoiesis by affecting the balance between self-renewal and differentiation. The canonical function of EZH2 is methylation of H3K27, although important non-canonical roles have recently been described. EZH2 mutation or deregulated expression has been conclusively demonstrated in the pathogenesis of AML and response to treatment, thus making it an attractive therapeutic target. In this study, we therefore investigated whether inhibition of EZH2 might also improve the response of non-APL AML cells to ATRA-based therapy. We focused on GSK-343, a pyridone-containing S-adenosyl-L-methionine cofactor-competitive EZH2 inhibitor that is representative of its class, and HKMTI-1-005, a substrate-competitive dual inhibitor targeting EZH2 and the closely related G9A/GLP H3K9 methyltransferases. We found that treatment with HKMTI-1-005 phenocopied EZH2 knockdown and was more effective in inducing differentiation than GSK-343, despite the efficacy of GSK-343 in terms of abolishing H3K27 trimethylation. Furthermore, transcriptomic analysis revealed that in contrast to treatment with GSK-343, HKMTI-1-005 upregulated the expression of differentiation pathway genes with and without ATRA, while downregulating genes associated with a hematopoietic stem cell phenotype. These results pointed to a non-canonical role for EZH2, which was supported by the finding that EZH2 associates with the master regulator of myeloid differentiation, RARα, in an ATRA-dependent manner that was enhanced by HKMTI-1-005, possibly playing a role in co-regulator complex exchange during transcriptional activation. In summary, our results strongly suggest that addition of HKMTI-1-005 to ATRA is a new therapeutic approach against AML that warrants further investigation.

EZH2 and NF-κB: A context-dependent crosstalk and transcriptional regulation in cancer

Epigenetic modifications regulate critical biological processes that play a pivotal role in the pathogenesis of cancer. Enhancer of Zeste Homolog 2 (EZH2), a subunit of the Polycomb-Repressive Complex 2, catalyzes trimethylation of histone H3 on Lys 27 (H3K27) involved in gene silencing. EZH2 is amplified in human cancers and has roles in regulating several cellular processes, including survival, proliferation, invasion, and self-renewal. Though EZH2 is responsible for gene silencing through its canonical role, it also regulates the transcription of several genes promoting carcinogenesis via its non-canonical role. Constitutive activation of Nuclear Factor-kappaB (NF-κB) plays a crucial role in the development and progression of human malignancies. NF-κB is essential for regulating innate and adaptive immune responses and is one of the most important molecules that increases survival during carcinogenesis. Given the evidence that increased survival and proliferation are essential for tumor development and their association with epigenetic modifications, it seems plausible that EZH2 and NF-κB crosstalk may promote cancer progression. In this review, we expand on how EZH2 and NF-κB regulate cellular responses during cancer and their crosstalk of the canonical and non-canonical roles in a context-dependent manner.

EZH2 deregulates BMP, Hedgehog, and Hippo cell signaling pathways in esophageal squamous cell carcinoma

PURPOSE

Cell signaling pathways play central roles in cellular stemness state, and aberrant activation of these cascades is attributed to the severity of esophageal squamous cell carcinoma (ESCC). In this study, we aimed to determine the potential impact of enhancer of zeste homolog 2 (EZH2) gene on different cell signaling pathways including bone morphogenesis protein (BMP), Hedgehog, and Hippo in ESCC, and to illuminate EZH2-mediated gene regulatory networks in this aggressive malignancy.

MATERIALS AND METHODS

EZH2 silencing was performed in two ESCC lines, KYSE-30 and YM-1, followed by gene expression analysis of BMP, Hedgehog, and Hippo signaling using RT-qPCR. EZH2 enforced expression was induced in both cell lines and gene expression of the pathways was evaluated in parallel. The contribution of EZH2 in epithelial-mesenchymal transition (EMT) and cell migration were also evaluated.

RESULTS

EZH2 downregulation decreased expression of the vital components of the Hedgehog and Hippo signaling, while EZH2 upregulation significantly increased its levels in both ESCC cell lines. The expression of BMP target genes was either reduced in EZH2-expressing cells or increased in EZH2-silencing cells. Enforced expression of EZH2 stimulated downregulation of epithelial markers and upregulation of mesenchymal markers in KYSE-30 and YM-1 ​cells. Significant downregulation of mesenchymal markers was detected following the silencing of EZH2 in the cells. Knocking down EZH2 decreased migration, while enforced expression of EZH2 increased migration in both ESCC lines.

CONCLUSIONS

These results may support the promoting role of EZH2 in ESCC tumorigenesis through the recruitment of important cell signaling pathways.

PRC2 disruption in cerebellar progenitors produces cerebellar hypoplasia and aberrant myoid differentiation without blocking medulloblastoma growth

We show that Polycomb Repressive Complex-2 (PRC2) components EED and EZH2 maintain neural identity in cerebellar granule neuron progenitors (CGNPs) and SHH-driven medulloblastoma, a cancer of CGNPs. Proliferating CGNPs and medulloblastoma cells inherit neural fate commitment through epigenetic mechanisms. The PRC2 is an epigenetic regulator that has been proposed as a therapeutic target in medulloblastoma. To define PRC2 function in cerebellar development and medulloblastoma, we conditionally deleted PRC2 components Eed or Ezh2 in CGNPs and analyzed medulloblastomas induced in Eed-deleted and Ezh2-deleted CGNPs by expressing SmoM2, an oncogenic allele of Smo. Eed deletion destabilized the PRC2, depleting EED and EZH2 proteins, while Ezh2 deletion did not deplete EED. Eed-deleted cerebella were hypoplastic, with reduced proliferation, increased apoptosis, and inappropriate muscle-like differentiation. Ezh2-deleted cerebella showed similar, milder phenotypes, with fewer muscle-like cells and without reduced growth. Eed-deleted and Ezh2-deleted medulloblastomas both demonstrated myoid differentiation and progressed more rapidly than PRC2-intact controls. The PRC2 thus maintains neural commitment in CGNPs and medulloblastoma, but is not required for SHH medulloblastoma progression. Our data define a role for the PRC2 in preventing inappropriate, non-neural fates during postnatal neurogenesis, and caution that targeting the PRC2 in SHH medulloblastoma may not produce durable therapeutic effects.

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.

Regulation of the Key Epithelial Cancer Suppressor miR-124 Function by Competing Endogenous RNAs

A decrease in the miR-124 expression was observed in various epithelial cancers. Like a classical suppressor, miR-124 can inhibit the translation of multiple oncogenic proteins. Epigenetic mechanisms play a significant role in the regulation of miR-124 expression and involve hypermethylation of the MIR-124-1/-2/-3 genes and the effects of long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) according to the model of competing endogenous RNAs (ceRNAs). More than 40 interactomes (lncRNA/miR-124/mRNA) based on competition between lncRNAs and mRNAs for miR-124 binding have been identified in various epithelial cancers. LncRNAs MALAT1, NEAT1, HOXA11-AS, and XIST are the most represented in these axes. Fourteen axes (e.g., SND1-IT1/miR-124/COL4A1) are involved in EMT and/or metastasis. Moreover, eight axes (e.g., OIP5-AS1/miR-124-5p/IDH2) are involved in key pathways, such as Wnt/b-catenin, E2F1, TGF-β, SMAD, ERK/MAPK, HIF-1α, Notch, PI3K/Akt signaling, and cancer cell stemness. Additionally, 15 axes impaired patient survival and three axes reduced chemo- or radiosensitivity. To date, 14 cases of miR-124 regulation by circRNAs have been identified. Half of them involve circHIPK3, which belongs to the exonic ecircRNAs and stimulates cell proliferation, EMT, autophagy, angiogenesis, and multidrug resistance. Thus, miR-124 and its interacting partners may be considered promising targets for cancer therapy.

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.

Signatures of Co-Deregulated Genes and Their Transcriptional Regulators in Lung Cancer

Despite the significant progress made towards comprehending the deregulated signatures in lung cancer, these vary from study to study. We reanalyzed 25 studies from the Gene Expression Omnibus (GEO) to detect and annotate co-deregulated signatures in lung cancer and in single-gene or single-drug perturbation experiments. We aimed to decipher the networks that these co-deregulated genes (co-DEGs) form along with their upstream regulators. Differential expression and upstream regulators were computed using Characteristic Direction and Systems Biology tools, including GEO2Enrichr and X2K. Co-deregulated gene expression profiles were further validated across different molecular and immune subtypes in lung adenocarcinoma (TCGA-LUAD) and lung adenocarcinoma (TCGA-LUSC) datasets, as well as using immunohistochemistry data from the Human Protein Atlas, before being subjected to subsequent GO and KEGG enrichment analysis. The functional alterations of the co-upregulated genes in lung cancer were mostly related to immune response regulating the cell surface signaling pathway, in contrast to the co-downregulated genes, which were related to S-nitrosylation. Networks of hub proteins across the co-DEGs consisted of overlapping TFs (SOX2, MYC, KAT2A) and kinases (MAPK14, CSNK2A1 and CDKs). Furthermore, using Connectivity Map we highlighted putative repurposing drugs, including valproic acid, betonicine and astemizole. Similarly, we analyzed the co-DEG signatures in single-gene and single-drug perturbation experiments in lung cancer cell lines. In summary, we identified critical co-DEGs in lung cancer providing an innovative framework for their potential use in developing personalized therapeutic strategies.

ASCL1 regulates super-enhancer-associated miRNAs to define molecular subtypes of small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor with dismal prognosis. Recently, molecular subtypes of SCLC have been defined by the expression status of ASCL1, NEUROD1, YAP1, and POU2F3 transcription regulators. ASCL1 is essential for neuroendocrine differentiation and is expressed in the majority of SCLC. Although previous studies investigated ASCL1 target genes in SCLC cells, ASCL1‐mediated regulation of miRNAs and its relationship to molecular subtypes remain poorly explored. Here, we performed genome‐wide profiling of chromatin modifications (H3K27me3, H3K4me3, and H3K27ac) by CUT&Tag assay and ASCL1 knockdown followed by RNA sequencing and miRNA array analyses in SCLC cells. ASCL1 could preferentially regulate genes associated with super‐enhancers (SEs) defined by enrichment of H3K27ac marking. Moreover, ASCL1 positively regulated several SE‐associated miRNAs, such as miR‐7, miR‐375, miR‐200b‐3p, and miR‐429, leading to repression of their targets, whereas ASCL1 suppressed miR‐455‐3p, an abundant miRNA in other molecular subtypes. We further elucidated unique patterns of SE‐associated miRNAs in different SCLC molecular subtypes, highlighting subtype‐specific miRNA networks with functional relevance. Notably, we found apparent de‐repression of common target genes of different miRNAs following ASCL1 knockdown, suggesting combinatorial action of multiple miRNAs underlying molecular heterogeneity of SCLC (e.g., co‐targeting of YAP1 by miR‐9 and miR‐375). Our comprehensive analyses provide novel insights into SCLC pathogenesis and a clue to understanding subtype‐dependent phenotypic differences.

Targeting Triple-Negative Breast Cancer by a Novel Proteolysis Targeting Chimera Degrader of Enhancer of Zeste Homolog 2

Enhancer of zeste homolog 2 (EZH2), a catalytic subunit of polycomb repressive complex 2 (PRC2), is overexpressed in triple-negative breast cancer (TNBC), correlating with poor prognosis. However, EZH2 catalytic inhibitors are ineffective in suppressing the growth of TNBC cells that are dependent on EZH2. Knockdown of EZH2 inhibits the proliferation of these cells, suggesting that EZH2 protein overexpression but not its catalytic activity is critical for driving TNBC progression. Several proteolysis targeting chimera (PROTAC) degraders of EZH2, including the von Hippel-Lindau (VHL)-recruiting PROTAC YM281, have been reported. However, the effects of these EZH2 PROTACs in TNBC cells were not investigated. Here, we report the discovery and characterization of a novel, potent, and selective EZH2 PROTAC degrader, MS8815 (compound 16), which induced robust EZH2 degradation in a concentration-, time-, and proteasome-dependent manner in TNBC cells. Importantly, 16 effectively suppressed the cell growth in multiple TNBC cell lines and primary patient TNBC cells.

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.

EZH2 Regulates Lipopolysaccharide-Induced Periodontal Ligament Stem Cell Proliferation and Osteogenesis through TLR4/MyD88/NF-κB Pathway

Background

Periodontitis induced by bacteria especially Gram-negative bacteria is the most prevalent chronic inflammatory disease worldwide. Emerging evidence supported that EZH2 plays a significant role in the inflammatory response of periodontal tissues. However, little information is available regarding the underlying mechanism of EZH2 in periodontitis. This study is aimed at determining the potential role and underlying mechanism of EZH2 in periodontitis.

Methods

The protein levels of EZH2, H3K27ME, p-p65, p-IKB, TLR4, MyD88, Runx2, and OCN were examined by western blot assay. Proliferation was evaluated by CCK8 assay. The levels of TNFα, IL1β, and IL6 were detected by ELISA assay. Migration was detected by wound healing assay. The distribution of p65 was detected by immunofluorescence. The formation of mineralized nodules was analyzed using alizarin red staining.

Results

LPS stimulation significantly promoted EZH2 and H3K27me3 expression in primary human periodontal ligament stem cells (PDLSCs). Targeting EZH2 prevented LPS-induced upregulation of the inflammatory cytokines and inhibition of cell proliferation and migration. Furthermore, EZH2 knockdown attenuated the TLR4/MyD88/NF-κB signaling to facilitate PDLSC osteogenesis.

Conclusions

Modulation of the NF-κB pathway through the inhibition of EZH2 may offer a new perspective on the treatment of chronic apical periodontitis.

CircGSK3B promotes RORA expression and suppresses gastric cancer progression through the prevention of EZH2 trans-inhibition

BACKGROUND

Circular RNAs (circRNAs) are a class of non-coding RNA that play critical roles in the development and pathogenesis of various cancers. The circRNA circGSK3B (hsa_circ_0003763) has been shown to enhance cell proliferation, migration, and invasion in hepatocellular carcinoma. However, the specific functions and underlying mechanistic involvement of circGSK3B in gastric cancer (GC) have not yet been explored. Our study aimed to investigate the effect of circGSK3B on the progression of GC and to identify any potential mechanisms underlying this process.

METHODS

CircRNA datasets associated with GC were obtained from the PubMed, GEO, and ArrayExpress databases, and circRNAs were validated via RT-qPCR and Sanger sequencing. Biotin-labeled RNA pull-down, mass spectrometry, RNA immunoprecipitation, and in vitro binding assays were employed to determine proteins demonstrating interactions with circGSK3B. Gene expression regulation was assessed through RT-qPCR, chromatin immunoprecipitation, and western blot assays. Gain- and loss-of-function assays were used to analyze any effects of circGSK3B and its partner regulatory molecule (EZH2) on the proliferation, invasion, and migration abilities of GC cells both in vitro and in vivo.

RESULTS

CircGSK3B was mainly identified in the nucleus. This circRNA was present at a reduced concentration in GC tissues and cell lines. Overexpression of circGSK3B was shown to inhibit the growth, invasion, and metastasis of GC cells both in vitro and in vivo. Mechanistically, circGSK3B directly interacted with EZH2, acting to suppress the binding of EZH2 and H3K27me3 to the RORA promoter, and leading to an elevation in RORA expression and ultimately the suppression of GC progression.

CONCLUSIONS

CircGSK3B acts as a tumor suppressor, reducing EZH2 trans-inhibition and GC progression. This demonstrates the potential use of this RNA as a therapeutic target for GC.

The noncanonical role of EZH2 in cancer

Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of polycomb repressive complex 2 (PRC2). Dysregulation of EZH2 causes alteration of gene expression and functions, thereby promoting cancer development. The regulatory function of EZH2 varies across different tumor types. The canonical role of EZH2 is gene silencing through catalyzing the trimethylation of lysine 27 of histone H3 (H3K27me3) in a PRC2-dependent manner. Accumulating evidence indicates that EZH2 has an H3K27me3-independent function as a transcriptional coactivator and plays a critical role in cancer initiation, development, and progression. In this review, we summarize the regulation and function of EZH2 and focus on the current understanding of the noncanonical role of EZH2 in cancer.