EZH2 supports ovarian carcinoma cell invasion and/or metastasis via regulation of TGF-beta1 and is a predictor of outcome in ovarian carcinoma patients

Comparative transcriptomic study on the ovarian cancer between chicken and human

The laying hen is the spontaneous model of ovarian tumor. A comprehensive comparison based on RNA-seq from hens and women may shed light on the molecular mechanisms of ovarian cancer. We performed next-generation sequencing of microRNA and mRNA expression profiles in 9 chicken ovarian cancers and 4 normal ovaries, which has been deposited in GSE246604. Together with 6 public datasets (GSE21706, GSE40376, GSE18520, GSE27651, GSE66957, TCGA-OV), we conducted a comparative transcriptomics study between chicken and human. In the present study, miR-451, miR-2188-5p, and miR-10b-5p were differentially expressed in normal ovaries, early- and late-stage ovarian cancers. We also disclosed 499 up-regulated genes and 1,061 down-regulated genes in chicken ovarian cancer. The molecular signals from 9 cancer hallmarks, 25 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and 369 Gene Ontology (GO) pathways exhibited abnormalities in ovarian cancer compared to normal ovaries via Gene Set Enrichment Analysis (GSEA). In the comparative analysis across species, we have uncovered the conservation of 5 KEGG and 76 GO pathways between chicken and human including the mismatch repair and ECM receptor interaction pathways. Moreover, a total of 174 genes contributed to the core enrichment for these KEGG and GO pathways were identified. Among these genes, the 22 genes were found to be associated with overall survival in patients with ovarian cancer. In general, we revealed the microRNA profiles of ovarian cancers in hens and updated the mRNA profiles previously derived from microarrays. And we also disclosed the molecular pathways and core genes of ovarian cancer shared between hens and women, which informs model animal studies and gene-targeted drug development.

Epigenetic regulation in ovarian cancer

Ovarian cancer is one of the diseases that have the highest mortality rate for women, especially women over 50 years old. In the future, incidence and mortality rates are predicted to extend in countries with low HDI. Instability in the structure and function of genetic factors has long been known as a cause of cancer, including ovarian cancer. Besides understanding gene mutations, epigenetic alterations have emerged as another aspect leading to the pathogenesis of ovarian neoplasm. The development and progression of this fatal disease have been found to be associated with abnormalities of epigenetic regulation. DNA methylation, histone modification, and non-coding RNAs-based gene silencing are processes of interest in developing ovarian carcinoma and are also new targets for cancer detection or treatment.

Morphological Changes Induced by TKS4 Deficiency Can Be Reversed by EZH2 Inhibition in Colorectal Carcinoma Cells

BACKGROUND

The scaffold protein tyrosine kinase substrate 4 (TKS4) undergoes tyrosine phosphorylation by the epidermal growth factor receptor (EGFR) pathway via Src kinase. The TKS4 deficiency in humans is responsible for the manifestation of a genetic disorder known as Frank-Ter Haar syndrome (FTHS). Based on our earlier investigation, the absence of TKS4 triggers migration, invasion, and epithelial-mesenchymal transition (EMT)-like phenomena while concurrently suppressing cell proliferation in HCT116 colorectal carcinoma cells. This indicates that TKS4 may play a unique role in the progression of cancer. In this study, we demonstrated that the enhancer of zeste homolog 2 (EZH2) and the histone methyltransferase of polycomb repressive complex 2 (PRC2) are involved in the migration, invasion, and EMT-like changes in TKS4-deficient cells (KO). EZH2 is responsible for the maintenance of the trimethylated lysine 27 on histone H3 (H3K27me3).

METHODS

We performed transcriptome sequencing, chromatin immunoprecipitation, protein and RNA quantitative studies, cell mobility, invasion, and proliferation studies combined with/without the EZH2 activity inhibitor 3-deazanoplanocine (DZNep).

RESULTS

We detected an elevation of global H3K27me3 levels in the TKS4 KO cells, which could be reduced with treatment with DZNep, an EZH2 inhibitor. Inhibition of EZH2 activity reversed the phenotypic effects of the knockout of TKS4, reducing the migration speed and wound healing capacity of the cells as well as decreasing the invasion capacity, while the decrease in cell proliferation became stronger. In addition, inhibition of EZH2 activity also reversed most epithelial and mesenchymal markers. We investigated the wider impact of TKS4 deletion on the gene expression profile of colorectal cancer cells using transcriptome sequencing of wild-type and TKS4 knockout cells, particularly before and after treatment with DZNep. Additionally, we observed changes in the expression of several protein-coding genes and long non-coding RNAs that showed a recovery in expression levels following EZH2 inhibition.

CONCLUSIONS

Our results indicate that the removal of TKS4 causes a notable disruption in the gene expression pattern, leading to the disruption of several signal transduction pathways. Inhibiting the activity of EZH2 can restore most of these transcriptomics and phenotypic effects in colorectal carcinoma cells.

MTOR modulation induces selective perturbations in histone methylation which influence the anti-proliferative effects of mTOR inhibitors

Emerging data suggest a significant cross-talk between metabolic and epigenetic programs. However, the relationship between the mechanistic target of rapamycin (mTOR), which is a pivotal metabolic regulator, and epigenetic modifications remains poorly understood. Our results show that mTORC1 activation caused by the abrogation of its negative regulator tuberous sclerosis complex 2 (TSC2) coincides with increased levels of the histone modification H3K27me3 but not H3K4me3 or H3K9me3. This selective H3K27me3 induction was mediated via 4E-BP-dependent increase in EZH2 protein levels. Surprisingly, mTOR inhibition also selectively induced H3K27me3. This was independent of TSC2, and was paralleled by reduced EZH2 and increased EZH1 protein levels. Notably, the ability of mTOR inhibitors to induce H3K27me3 levels was positively correlated with their anti-proliferative effects. Collectively, our findings demonstrate that both activation and inhibition of mTOR selectively increase H3K27me3 by distinct mechanisms, whereby the induction of H3K27me3 may potentiate the anti-proliferative effects of mTOR inhibitors.

Enhancer of zeste homolog 2 (EZH2)-dependent sirtuin-3 determines sensitivity to glucose starvation in radioresistant head and neck cancer cells

Sirtuin 3 (SIRT3) regulates mitochondrial function as a mitochondrial deacetylase during oxidative stress. However, the specific regulatory mechanism and function of SIRT3 in radioresistant cancer cells are unclear. In this study, we aim to investigate how SIRT3 determines the susceptibility to glucose deprivation and its regulation in p53-based radioresistant head and neck cancer cells. We observed mitochondrial function using two established isogenic radioresistant subclones (HN3R-A [p53 null] and HN3R-B [p53 R282W]) with intratumoral p53 heterogeneity. Cell counting analysis was performed to evaluate cell proliferation and cell death. The correlation between the regulation of SIRT3 and enhancer of zeste homolog 2 (EZH2) was confirmed by immunoblotting and chromatin immunoprecipitation assay. p53-deficient radioresistant cells (HN3R-A) expression reduced SIRT3 levels and increased sensitivity to glucose deprivation due to mitochondrial dysfunction compared to other cells. In these cells, activation of SIRT3 significantly prevented glucose deprivation-induced cell death, whereas the loss of SIRT3 increased the susceptibility to glucose deficiency. We discovered that radiation-induced EZH2 directly binds to the SIRT3 promoter and represses the expression. Conversely, inhibiting EZH2 increased the expression of SIRT3 through epigenetic changes. Our findings indicate that p53-deficient radioresistant cells with enhanced EZH2 exhibit increased sensitivity to glucose deprivation due to SIRT3 suppression. The regulation of SIRT3 by EZH2 plays a critical role in determining the cell response to glucose deficiency in radioresistant cancer cells. Therefore, EZH2-dependent SIRT3 could be used as a predictive biomarker to select treatment options for patients with radiation-resistance.

The Ovary-Brain Connection

The brain and the ovaries are in a state of continuous communication [...].

Comparative analysis of EZH2, p16 and p53 expression in uterine carcinosarcomas

Introduction: The role of p16 and p53 immunohistochemistry in the diagnosis of rare and aggressive uterine carcinosarcoma (UCS) has been well established. However, enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and a member of the polycomb group family is a relatively new biomarker, with limited published data on its significance in this tumor type. The goal of this study was to examine EZH2 expression in UCS and its components, in correlation with morphological features, and p16 and p53 staining patterns. Methods: Twenty-eight UCSs were included in the study. EZH2, p16 and p53 immunoreactivity were assessed independently by two pathologists in both tumor components (epithelial and mesenchymal). EZH2 and p16 immunostains were scored semiquantitatively: based on the percentage and intensity of tumor cell staining a binary staining index ("high- or low-expressing") was calculated. The p53 staining pattern was evaluated as wild-type or aberrant (diffuse nuclear, null, or cytoplasmic expression). Statistical tests were used to evaluate the correlation between staining patterns for all three markers and the different tumor components and histotypes. Results: High EZH2 and p16 expression and aberrant p53 patterns were present in 89.3% 78.6% and 85.7% of the epithelial component and in 78.6%, 62.5% and 82.1% of the mesenchymal component, respectively. Differences among these expression rates were not found to be significant (p > 0.05). Regarding the epithelial component, aberrant p53 pattern was found to be significantly (p = 0.0474) more frequent in the serous (100%) than in endometrioid (66.6%) histotypes. Within the mesenchymal component, p53 null expression pattern occurred significantly (p = 0.0257) more frequently in heterologous sarcoma components (71.4%) compared to the homologous histotype (18.8%). Conclusion: In conclusion, EZH2, p16 and p53 seem to play a universal role in the pathogenesis of UCS; however, a distinctive pattern of p53 expression appears to exist between the serous and endometrioid carcinoma components and also between the homologous and heterologous sarcoma components.

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.

Discovery of a Novel Covalent EZH2 Inhibitor Based on Tazemetostat Scaffold for the Treatment of Ovarian Cancer

Enhancer of zeste homologue 2 (EZH2) is the enzymatic catalytic subunit of polycomb repressive complex 2 (PRC2), which plays an important role in post-translational modifications of histones. In this study, we designed and synthesized a new series EZH2 covalent inhibitors that have rarely been reported. Biochemical studies and mass spectrometry provide information that SKLB-03220 could covalently bind to the S-adenosylmethionine (SAM) pocket of EZH2. Besides, SKLB-03220 was highly potent for EZH2MUT, while exhibiting weak activities against other tested histone methyltransferases (HMTs) and kinases. Moreover, SKLB-03220 displayed noteworthy potency against ovarian cancer cell lines and continuously abolished H3K27me3 after washing out. Furthermore, oral administration of SKLB-03220 significantly inhibited tumor growth in PA-1 xenograft model without obvious adverse effects. Taken together, SKLB-03220 is a potent, selective EZH2 covalent inhibitor with noteworthy anticancer efficacy both in vitro and in vivo.

H3K27me3 in Diffuse Midline Glioma and Epithelial Ovarian Cancer: Opposing Epigenetic Changes Leading to the Same Poor Outcomes

Histone post-translational modifications modulate gene expression through epigenetic gene regulation. The core histone H3 family members, H3.1, H3.2, and H3.3, play a central role in epigenetics. H3 histones can acquire many post-translational modifications, including the trimethylation of H3K27 (H3K27me3), which represses transcription. Triple methylation of H3K27 is performed by the histone methyltransferase Enhancer of Zeste Homologue 2 (EZH2), a component of the Polycomb Repressive Complex 2. Both global increases and decreases in H3K27me3 have been implicated in a wide range of cancer types. Here, we explore how opposing changes in H3K27me3 contribute to cancer by highlighting its role in two vastly different cancer types; (1) a form of glioma known as diffuse midline glioma H3K27-altered and (2) epithelial ovarian cancer. These two cancers vary widely in the age of onset, sex, associated mutations, and cell and organ type. However, both diffuse midline glioma and ovarian cancer have dysregulation of H3K27 methylation, triggering changes to the cancer cell transcriptome. In diffuse midline glioma, the loss of H3K27 methylation is a primary driving factor in tumorigenesis that promotes glial cell stemness and silences tumor suppressor genes. Conversely, hypermethylation of H3K27 occurs in late-stage epithelial ovarian cancer, which promotes tumor vascularization and tumor cell migration. By using each cancer type as a case study, this review emphasizes the importance of H3K27me3 in cancer while demonstrating that the mechanisms of histone H3 modification and subsequent gene expression changes are not a one-size-fits-all across cancer types.

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.

Is There a Role for Epigenetic Therapies in Modulating DNA Damage Repair Pathways to Enhance Chemotherapy and Overcome Drug Resistance?

Epigenetic therapies describe drug molecules such as DNA methyltransferase, histone methyltransferase and histone acetylase/deacetylase inhibitors, which target epigenetic mechanisms such as DNA methylation and histone modifications. Many DNA damage response (DDR) genes are epigenetically regulated in cancer leading to transcriptional silencing and the loss of DNA repair capacity. Epigenetic marks at DDR genes, such as DNA methylation at gene promoters, have the potential to be used as stratification biomarkers, identifying which patients may benefit from particular chemotherapy treatments. For genes such as MGMT and BRCA1, promoter DNA methylation is associated with chemosensitivity to alkylating agents and platinum coordination complexes, respectively, and they have use as biomarkers directing patient treatment options. In contrast to epigenetic change leading to chemosensitivity, DNA methylation of DDR genes involved in engaging cell death responses, such as MLH1, are associated with chemoresistance. This contrasting functional effect of epigenetic modification on chemosensitivity raises challenges in using DNA-demethylating agents, and other epigenetic approaches, to sensitise tumours to DNA-damaging chemotherapies and molecularly targeted agents. Demethylation of MGMT/BRCA1 could lead to drug resistance whereas demethylation of MLH1 could sensitise cells to chemotherapy. Patient selection based on a solid understanding of the disease pathway will be one means to tackle these challenges. The role of epigenetic modification of DDR genes during tumour development, such as causing a mutator phenotype, has different selective pressures and outcomes compared to epigenetic adaptation during treatment. The prevention of epigenetic adaptation during the acquisition of drug resistance will be a potential strategy to improve the treatment of patients using epigenetic therapies.

Smad3 methylation by EZH2 promotes its activation and tumor metastasis

SMAD3 plays a central role in cancer metastasis, and its hyperactivation is linked to poor cancer outcomes. Thus, it is critical to understand the upstream signaling pathways that govern SMAD3 activation. Here, we report that SMAD3 underwent methylation at K53 and K333 (K53/K333) by EZH2, a process crucial for cell membrane recruitment, phosphorylation, and activation of SMAD3 upon TGFB1 stimulation. Mechanistically, EZH2-triggered SMAD3 methylation facilitated SMAD3 interaction with its cellular membrane localization molecule (SARA), which in turn sustained SMAD3 phosphorylation by the TGFB receptor. Pathologically, increased expression of EZH2 expression resulted in the accumulation of SMAD3 methylation to facilitate SMAD3 activation. EZH2-mediated SMAD3 K53/K333 methylation was upregulated and correlated with SMAD3 hyperactivation in breast cancer, promoted tumor metastasis, and was predictive of poor survival outcomes. We used 2 TAT peptides to abrogate SMAD3 methylation and therapeutically inhibit cancer metastasis. Collectively, these findings reveal the complicated layers involved in the regulation of SMAD3 activation coordinated by EZH2-mediated SMAD3 K53/K333 methylation to drive cancer metastasis.

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

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

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.

AP-2α-Mediated Activation of E2F and EZH2 Drives Melanoma Metastasis

In melanoma metastasis, the role of the AP-2α transcription factor, which is encoded by TFAP2A, is controversial as some findings have suggested tumor suppressor activity while other studies have shown high TFAP2A expression in node-positive melanoma associated with poor prognosis. Here we demonstrate that AP-2α facilitates melanoma metastasis through transcriptional activation of genes within the E2F pathway including EZH2. A BioID screen found that AP-2α interacts with members of the nucleosome remodeling and deacetylase (NuRD) complex. Loss of AP-2α removed activating chromatin marks in the promoters of EZH2 and other E2F target genes through activation of the NuRD repression complex. In melanoma cells, treatment with tazemetostat, an FDA-approved and highly specific EZH2 inhibitor, substantially reduced anchorage-independent colony formation and demonstrated heritable antimetastatic effects, which were dependent on AP-2α. Single-cell RNA sequencing analysis of a metastatic melanoma mouse model revealed hyperexpansion of Tfap2a ^High/E2F-activated cell populations in transformed melanoma relative to progenitor melanocyte stem cells. These findings demonstrate that melanoma metastasis is driven by the AP-2α/EZH2 pathway and suggest that AP-2α expression can be used as a biomarker to predict responsiveness to EZH2 inhibitors for the treatment of advanced melanomas. SIGNIFICANCE: AP-2α drives melanoma metastasis by upregulating E2F pathway genes including EZH2 through inhibition of the NuRD repression complex, serving as a biomarker to predict responsiveness to EZH2 inhibitors.

Morphologic and molecular correlates of EZH2 as a predictor of platinum resistance in high-grade ovarian serous carcinoma

BACKGROUND

Enhancer of zesta homologue 2 (EZH2) is an essential component of polycomb repressive complex 2 (PRC2) that contributes to tumor progression and chemo-resistance. The aim of this study was to comprehensively assess the prognostic value of EZH2 across the morphologic and molecular spectra of high-grade serous ovarian carcinoma (HGSOC) by utilizing both immunohistochemistry (IHC) and proteogenomic technologies.

METHODS

IHC of EZH2 was performed using a tissue microarray of 79 HGSOC scored (+/-) for lymphovascular invasion (LVI), tumor-infiltrating lymphocytic aggregates ≥1 mm (TIL) and architectural growth patterns. The association of EZH2 H-score with response to therapy and overall survival was evaluated by tumor features. We also evaluated EZH2 transcriptional (RNA sequencing) and protein (mass spectrometry) expression from bulk tumor samples from 336 HGSOC from The Cancer Genome Atlas (TCGA). EZH2 expression and co-expression networks were compared by clinical outcomes.

RESULTS

For HGSOC without TIL (58%), EZH2 expression was almost 2-fold higher in platinum resistant tumors (P = 0.01). Conversely, EZH2 was not associated with platinum resistance among TIL+ HGSOC (P = 0.41). EZH2 expression was associated with reduced survival for tumors with LVI (P = 0.04). Analysis of TCGA found higher EZH2 expression in immunoreactive and proliferative tumors (P = 6.7 × 10^- 5) although protein levels were similar across molecular subtypes (P = 0.52). Both mRNA and protein levels of EZH2 were lower in platinum resistant tumors although they were not associated with survival. Co-expression analysis revealed EZH2 networks totaling 1049 mRNA and 448 proteins that were exclusive to platinum sensitive or resistant tumors. The EZH2 network in resistant HGSOC included CARM1 which was positively correlated with EZH2 at both mRNA (r = 0.33, p = 0.003) and protein (r = 0.14, P = 0.01) levels. Further, EZH2 co-expression with CARM1 corresponded to a decreased prognostic significance of EZH2 expression in resistant tumors.

CONCLUSIONS

Our findings demonstrate that EZH2 expression varies based on its interactions with immunologic pathways and tumor microenvironment, impacting the prognostic interpretation. The association between high EZH2 expression and platinum resistance in TIL- HGSOC warrants further study of the implications for therapeutic strategies.

Application of enhancer of zeste homolog 2 immunocytochemistry to bile cytology

BACKGROUND

Bile cytology has low diagnostic sensitivity and requires ancillary techniques. This study assessed the utility of enhancer of zeste homolog 2 (EZH2) immunocytochemistry (ICC) in bile cytology.

METHODS

A total of 141 bile cytology specimens from 141 patients were evaluated retrospectively. Papanicolaou-stained slides were immunostained with an antibody to EZH2. After calculation of the EZH2 labeling index (LI), the cutoff value was determined via receiver operating characteristic curve analysis. Cytological performance with and without EZH2 ICC was evaluated with reference to the final diagnosis.

RESULTS

The area under the curve for the EZH2 LI was 0.955, and the cutoff value for identifying benign bile samples versus malignant ones was 24.0%. The sensitivity and specificity values for malignancy were 53.4% and 100% for routine cytology only, 89.0% and 95.7% for EZH2 ICC only, and 89.8% and 95.7% for a combination of routine cytology and EZH2 ICC. The sensitivities of EZH2 ICC only and a combination of routine cytology and EZH2 ICC were significantly improved in comparison with routine cytology only (P < .001). EZH2 ICC alone had a sensitivity of 68.0% and a specificity of 85.7% in bile samples with atypical cytology, a sensitivity of 87.0% in samples that were suspicious for malignancy, and a sensitivity of 85.7% and a specificity of 100% in samples that were negative for malignancy.

CONCLUSIONS

EZH2 ICC improved the diagnostic sensitivity for pancreatobiliary adenocarcinoma in bile cytology. This method is particularly meaningful in samples of indeterminate cytology and may be useful as an initial assessment to ensure that no cancer cells are missed.

EZH2-miRNA Positive Feedback Promotes Tumor Growth in Ovarian Cancer

Enhancer of zester homolog 2 (EZH2), a histone methyl transferase that mediates H3K27me3 through polycomb repressive complex 2 (PRC2), is overexpressed in ovarian cancer and promotes malignant proliferation. However, the underlying mechanism of maintaining high EZH2 expression remains elusive. Here we showed that microRNA(miRNA) inhibited EZH2 by binding to the 3′-UTR of EZH2 mRNA; conversely, EZH2 can inhibit miRNA expression. We confirmed that a feedback loop exists between EZH2 and miRNA that maintained EZH2 overexpression, thus promoting ovarian cancer proliferation in vivo and in vitro. We further explored that EZH2 inhibited miRNA expression through PRC2, as determined by CHIP (chromatin immunoprecipitation), and EZH2 decreased the expression of p21, p53, and RUNX3. These results suggest that EZH2 inhibits the expression of Et-miRNAs (EZH2-targeting miRNAs) through the H3K27me3 pathway, thus forming an EZH2-miRNA positive feedback loop that maintains the high expression of EZH2 and promotes the malignant proliferation of cancer cells by regulating the expression of cell proliferation-related proteins.

Effect of EZH2 on pulmonary artery smooth muscle cell migration in pulmonary hypertension

Pulmonary hypertension (PH) is a life‑threatening disease that often involves vascular remodeling. Although pulmonary arterial smooth muscle cells (PASMCs) are the primary participants in vascular remodeling, their biological role is not entirely clear. The present study analyzed the role of enhancer of zeste homolog 2 (EZH2) in vascular remodeling of PH by investigating the behavior of PASMCs. The expression levels of EZH2 in PASMCs in chronic thromboembolic pulmonary hypertension (CTEPH), a type of PH, were detected. The role of EZH2 in PASMC migration was investigated by wound‑healing assay following overexpression and knockdown. Functional enrichment analysis of the whole‑genome expression profiles of PASMCs with EZH2 overexpression was performed using an mRNA Human Gene Expression Microarray. Quantitative (q)PCR was performed to confirm the results of the microarray. EZH2 expression levels increased in CTEPH cell models. The overexpression of EZH2 enhanced PASMC migration compared with control conditions. Functional enrichment analysis of the differentially expressed genes following EZH2 overexpression indicated a strong link between EZH2 and the immune inflammatory response and oxidoreductase activity in PASMCs. mRNA expression levels of superoxide dismutase 3 were verified by qPCR. The results suggested that EZH2 was involved in the migration of PASMCs in PH, and may serve as a potential target for the treatment of PH.

Clinical impact of EZH2 and its antagonist SMARCA4 in ovarian cancer

SMARCA4 and EZH2 are two functional key players of their respective antagonizing chromatin remodeling complexes SWI/SNF and PRC2. EZH2 inhibitory drugs may abrogate pro-oncogenic features of PRC2 and turn the balance to cell differentiation via SWI/SNF activity in cancers. SMARCA4 and EZH2 expression was assessed by RT-PCR in 238 epithelial ovarian cancers (OCs) and put in relation to clinico-pathological parameters and patients' outcome. Optimal thresholds for high and low expression of both variables were calculated by the Youden's index based on receiver operating characteristic (ROC) curves. High SMARCA4 mRNA expression was independently associated with favorable progression-free survival (PFS) (P = 0.03) and overall survival (OS) (P = 0.018). As Youden's threshold determination for EZH2 yielded a S-shaped ROC-curve, two cut-off points (29th and 94th percentile) predicting opposite features were defined. Whereas EZH2 mRNA levels beyond the 29th percentile independently predicted poor PFS (P = 0.034), Cox-regression in EZH2 transcripts above the 94th percentile revealed a conversion from unfavorable to favorable PFS and OS (P = 0.009 and P = 0.032, respectively). High SMARCA4 expression associates with improved survival, whereas moderate/high EZH2 expression predicts poor outcome, which converts to favorable survival in ultra-high expressing OCs. This small OC subgroup could be characterized by REV7-abrogated platinum hypersensitivity but concomitant PARP-inhibitor resistance.

Downregulation of histone-lysine N-methyltransferase EZH2 inhibits cell viability and enhances chemosensitivity in lung cancer cells

Histone-lysine N-methyltransferase EZH2 (EZH2) is the principle component of the polycomb repressive complex 2 (PRC2)/embryonic ectoderm development protein-EZH2 complex, which promotes tumorigenesis by repressing transcription of tumor suppressor genes. EZH2 is considered a key marker in several types of cancer, such as colorectal and prostate cancer. However, the molecular mechanisms and clinical value of EZH2 in lung cancer have not yet been fully investigated. The aim of the present study was to investigate the functions of EZH2 in lung cancer progression and to determine whether treatment with an EZH2 inhibitor enhanced the chemosensitivity of lung cancer cells to cisplatin (CDDP). At the logarithmic growth phase, A549 cells were treated with a small interfering (si)RNA-EZH2, and cell viability was detected using an MTT assay. The degree of apoptosis and cell cycle were detected using flow cytometry. Cell migration and invasion were detected via wound healing and Transwell Matrigel assays. According to information from the Gene Expression Omnibus database, the results of the present study demonstrated that EZH2 was upregulated in lung cancer. Furthermore, overexpression of EZH2 was associated with poor patient prognosis, while EZH2 knockdown inhibited cell viability and migration, and enhanced apoptosis and chemosensitivity in a lung cancer cell line. EZH2 knockdown and treatment of A549 cells using EZH2 inhibitor elevated the inhibitory effects of CDDP on cell viability and apoptosis. Western blot and reverse transcription-quantitative PCR analyses were performed to assess the expression levels of relative protein and mRNA, respectively, in A549 cells treated with siRNA-EZH2 or with CDDP. Overall, the results of the present study demonstrated that high EZH2 expression was associated with poor prognosis, accompanied with a potential impairment of migration and viability in lung cancer cells. These findings suggest that EZH2 may act as a candidate molecular target for gene therapy, and treatment with EZH2 inhibitor may be used to increase chemosensitivity to CDDP agents in lung cancer.

Clinicopathologic significance of protein lysine methyltransferases in cancer

Protein lysine methyltransferases (PKMTs) constitute a large family of approximately 50 chromatin modifiers that mono-, di- and/or tri-methylate lysine residues on histone and non-histone substrates. With the advent of The Cancer Genome Atlas, it became apparent that this family of chromatin modifiers harbors frequent genetic and expression alterations in multiple types of cancer. In this regard, past and ongoing preclinical studies have provided insight into the mechanisms of action of some of these enzymes, laying the ground for the ongoing development of PKMT inhibitors as novel anticancer therapeutics. The purpose of this review is to summarize existing data obtained by different research groups through immunohistochemical analysis of the protein expression levels of PKMTs, and their respective clinicopathologic associations. We focused on studies that used immunohistochemistry to associate protein expression levels of specific PKMTs, as well as several established histone methylation marks, with clinicopathologic features and survival outcomes in various cancer types. We also review ongoing clinical trials of PKMT inhibitors in cancer treatment. This review underscores the clinical relevance and potential of targeting the family of PKMT enzymes as the next generation of cancer therapy.

Regulating Methylation at H3K27: A Trick or Treat for Cancer Cell Plasticity

Properly timed addition and removal of histone 3 lysine 27 tri-methylation (H3K27me3) is critical for enabling proper differentiation throughout all stages of development and, likewise, can guide carcinoma cells into altered differentiation states which correspond to poor prognoses and treatment evasion. In early embryonic stages, H3K27me3 is invoked to silence genes and restrict cell fate. Not surprisingly, mutation or altered functionality in the enzymes that regulate this pathway results in aberrant methylation or demethylation that can lead to malignancy. Likewise, changes in expression or activity of these enzymes impact cellular plasticity, metastasis, and treatment evasion. This review focuses on current knowledge regarding methylation and de-methylation of H3K27 in cancer initiation and cancer cell plasticity.

EZH2 Regulates Pancreatic Cancer Subtype Identity and Tumor Progression via Transcriptional Repression of GATA6

Recent studies have thoroughly described genome-wide expression patterns defining molecular subtypes of pancreatic ductal adenocarcinoma (PDAC), with different prognostic and predictive implications. Although the reversible nature of key regulatory transcription circuits defining the two extreme PDAC subtype lineages "classical" and "basal-like" suggests that subtype states are not permanently encoded but underlie a certain degree of plasticity, pharmacologically actionable drivers of PDAC subtype identity remain elusive. Here, we characterized the mechanistic and functional implications of the histone methyltransferase enhancer of zeste homolog 2 (EZH2) in controlling PDAC plasticity, dedifferentiation, and molecular subtype identity. Utilization of transgenic PDAC models and human PDAC samples linked EZH2 activity to PDAC dedifferentiation and tumor progression. Combined RNA- and chromatin immunoprecipitation sequencing studies identified EZH2 as a pivotal suppressor of differentiation programs in PDAC and revealed EZH2-dependent transcriptional repression of the classical subtype defining transcription factor Gata6 as a mechanistic basis for EZH2-dependent PDAC progression. Importantly, genetic or pharmacologic depletion of EZH2 sufficiently increased GATA6 expression, thus inducing a gene signature shift in favor of a less aggressive and more therapy-susceptible, classical PDAC subtype state. Consistently, abrogation of GATA6 expression in EZH2-deficient PDAC cells counteracted the acquisition of classical gene signatures and rescued their invasive capacities, suggesting that GATA6 derepression is critical to overcome PDAC progression in the context of EZH2 inhibition. Together, our findings link the EZH2-GATA6 axis to PDAC subtype identity and uncover EZH2 inhibition as an appealing strategy to induce subtype-switching in favor of a less aggressive PDAC phenotype. SIGNIFICANCE: This study highlights the role of EZH2 in PDAC progression and molecular subtype identity and suggests EZH2 inhibition as a strategy to recalibrate GATA6 expression in favor of a less aggressive disease. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/21/4620/F1.large.jpg.

EZH2-mediated Epigenetic Silencing of miR-29/miR-30 targets LOXL4 and contributes to Tumorigenesis, Metastasis, and Immune Microenvironment Remodeling in Breast Cancer

Enhancer of Zeste Homolog 2 (EZH2), a key epigenetic regulator, is involved in breast cancer progression and metastasis. LOXL4 is increasingly recognized as an important player in cancer progression. To date, how EZH2 regulates LOXL4 in the progression of breast cancer remains unclear.

Methods: We evaluated the association between LOX family proteins and EZH2 in invasive breast carcinoma through the starBase v2.0 analysis, and its correlation with breast tumorigenesis using the Oncomine dataset. We then applied miRcode data combined with gene expression omnibus (GEO) data to screen candidate miRNAs mediating the regulation of LOXL4 by EZH2. We explored the regulatory mechanism of EZH2, miR-29b/miR-30d, and LOXL4 in breast cancer cells by qRT-PCR, Western blotting, cell proliferation, colony formation, and wound healing assays, xenograft experiments, dual-luciferase reporter assay, and chromatin immunoprecipitation. All statistical tests were two-sided.

Results: Inhibition of EZH2 or LOXL4, or miR-29b/miR-30d overexpression, decreased breast cancer cell proliferation, migration, and metastasis in vitro and in vivo. LOXL4 was identified as a direct target of miR-29b and miR-30d. EZH2 inhibition enhanced miR-30d and miR-29b transcription via promoter binding activity, leading to the reduced expression of LOXL4. Immunohistochemical analysis of human breast cancer specimens and flow cytometry analysis of tumor-infiltrating macrophages in mice showed a positive association of EZH2 with LOXL4 expression and macrophage infiltration.

Conclusions: Our findings identified EZH2-miR-29b/miR-30d-LOXL4 signaling pathway was involved in breast tumorigenesis, and suggested that the epigenetic modulation represents a potential therapeutic target for breast cancer by controlling macrophage activation.

Epigenetic Silencing of miR-9 Promotes Migration and Invasion by EZH2 in Glioblastoma Cells

Glioblastoma (GBM) is the most common primary brain tumor in adults. Tumor invasion is the major reason for treatment failure and poor prognosis in GBM. Inhibiting migration and invasion has become an important therapeutic strategy for GBM treatment. Enhancer of zeste homolog 2 (EZH2) and C-X-C motif chemokine receptor 4 (CXCR4) have been determined to have important roles in the occurrence and development of tumors, but the specific relationship between EZH2 and CXCR4 expression in GBM is less well characterized. In this study, we report that EZH2 and CXCR4 were overexpressed in glioma patients. Furthermore, elevated EZH2 and CXCR4 were correlated with shorter disease-free survival. In three human GBM cell lines, EZH2 modulated the expression of miR-9, which directly targeted the oncogenic signaling of CXCR4 in GBM. The ectopic expression of miR-9 dramatically inhibited the migratory capacity of GBM cells in vitro. Taken together, our results indicate that miR-9, functioning as a tumor-suppressive miRNA in GBM, is suppressed through epigenetic silencing by EZH2. Thus, miR-9 may be an attractive target for therapeutic intervention in GBM.

The Emerging Roles of Heterochromatin in Cell Migration

Cell migration is a key process in health and disease. In the last decade an increasing attention is given to chromatin organization in migrating cells. In various types of cells induction of migration leads to a global increase in heterochromatin levels. Heterochromatin is required for optimal cell migration capabilities, since various interventions with heterochromatin formation impeded the migration rate of numerous cell types. Heterochromatin supports the migration process by affecting both the mechanical properties of the nucleus as well as the genetic processes taking place within it. Increased heterochromatin levels elevate nuclear rigidity in a manner that allows faster cell migration in 3D environments. Condensed chromatin and a more rigid nucleus may increase nuclear durability to shear stress and prevent DNA damage during the migration process. In addition, heterochromatin reorganization in migrating cells is important for induction of migration-specific transcriptional plan together with inhibition of many other unnecessary transcriptional changes. Thus, chromatin organization appears to have a key role in the cellular migration process.

EZH2 has a non-catalytic and PRC2-independent role in stabilizing DDB2 to promote nucleotide excision repair

Small cell lung cancer (SCLC) is a highly aggressive malignancy with poor outcomes associated with resistance to cisplatin-based chemotherapy. Enhancer of Zeste Homolog 2 (EZH2) is the catalytic subunit of Polycomb Repressive Complex 2 (PRC2), which silences transcription through trimethylation of histone H3 lysine 27 (H3K27me3) and has emerged as an important therapeutic target with inhibitors targeting its methyltransferase activity under clinical investigation. Here, we show that EZH2 has a non-catalytic and PRC2 independent role in stabilizing DDB2 to promote nucleotide excision repair (NER) and govern cisplatin resistance in SCLC. Using a synthetic lethality screen, we identified important regulators of cisplatin resistance in SCLC cells, including EZH2. EZH2 depletion causes cellular cisplatin and UV hypersensitivity in an epistatic manner with DDB1-DDB2. EZH2 complexes with DDB1-DDB2 and promotes DDB2 stability by impairing its ubiquitination independent of methyltransferase activity or PRC2, thereby facilitating DDB2 localization to cyclobutane pyrimidine dimer (CPD) crosslinks to govern their repair. Furthermore, targeting EZH2 for depletion with DZNep strongly sensitizes SCLC cells and tumors to cisplatin. Our findings reveal a non-catalytic and PRC2-independent function for EZH2 in promoting NER through DDB2 stabilization, suggesting a rationale for targeting EZH2 beyond its catalytic activity for overcoming cisplatin resistance in SCLC.

Carcinogenic roles and therapeutic effects of EZH2 in gynecological cancers

Enhancer of Zeste Homolog 2 (EZH2) is highly expressed in kinds of malignant tumors and related to tumor occurrence, development, and prognosis. EZH2 is the catalytic subunit of the polycomb repressive complex 2 (PRC2), which promotes cell proliferation, migration, and invasion by epigenetic regulation of anti-tumor gene. It can activate numerous tumor-associated signaling pathways and interfere with DNA damage repair. In recent years, large amounts of studies have shown that EZH2 is closely related to gynecologic-related malignancies and can be used as a potential target gene for the treatment of gynecological-related malignancies. This review summarizes the oncogenic function of EZH2 and introduces the recent advances in the development of EZH2 inhibitors. On this basis, future research prospect of EZH2 is proposed.

Overexpression of enhance of Zeste homolog 2 (EZH2) in endometrial carcinoma: An NRG Oncology/Gynecologic Oncology Group Study

OBJECTIVES

Enhancer of zeste homolog 2 (EZH2) is a histone methyl transferase that mediates epigenetic silencing of tumor suppressor genes. It is commonly over-expressed in several solid tumors and has been shown to be a prognostic biomarker. We investigated patterns of EZH2 expression in endometrial cancer.

METHODS

Evaluation of EZH2 expression was completed on both early and advanced stage endometrioid adenocarcinoma tissues and a subset of matched normal mullerian tissue samples, from participants enrolled in Gynecologic Oncology Group (GOG) protocol 210, using real time reverse transcription polymerase chain reaction (RT-PCR) and western blot (WB) analysis. Non-parametric methods were used to assess differences in mRNA and protein expression respectively with known clinical/pathologic prognostic factors. Survival analysis was performed using techniques including Cox proportional hazards (PH) model to evaluate differences in progression free survival (PFS) and overall survival (OS) based on EZH2 expression.

RESULTS

Eighty-seven patient samples were analyzed that included 60 tumors and 27 matched-normal tissue specimens. EZH2 mRNA (p < .0001) and protein expression (p < .0001) in tumor specimens were significantly higher than in matched-normal tissue. In primary tumors, EZH2 protein expression was associated with lympho-vascular space invasion (LVSI, p = .044), and EZH2 mRNA expression was associated with age (p = .037). Differences in EZH2 expression between primary tumors and matched normal tissue were not associated with other known clinical and pathologic factors. However, there did appear to be a trend toward decreased progression-free survival among patients with high EZH2 expression levels.

CONCLUSIONS

Our results confirm the differential expression of EZH2 in uterine cancers compared to normal tissues. However, there were no statistically significant differences in survival associated with EZH2 expression in patients with endometrial cancer. NCT #: NCT00340808.

The synergistic effect of DZ‑NEP, panobinostat and temozolomide reduces clonogenicity and induces apoptosis in glioblastoma cells

Current treatment against glioblastoma consists of surgical resection followed by temozolomide, with or without combined radiotherapy. Glioblastoma frequently acquires resistance to chemotherapy and/or radiotherapy. Novel therapeutic approaches are thus required. The inhibition of enhancer of zeste homolog 2 (EZH2; a histone methylase) and histone deacetylases (HDACs) are possible epigenetic treatments. Temozolomide, 3‑deazaneplanocin A (DZ‑Nep; an EZH2 inhibitor) and panobinostat (an HDAC inhibitor) were tested in regular and temozolomide‑resistant glioblastoma cells to confirm whether the compounds could behave in a synergistic, additive or antagonistic manner. A total of six commercial cell lines, two temozolomide‑induced resistant cell lines and two primary cultures derived from glioblastoma samples were used. Cell lines were exposed to single treatments of the drugs in addition to all possible two‑ and three‑drug combinations. Colony formation assays, synergistic assays and reverse transcription‑quantitative PCR analysis of apoptosis‑associated genes were performed. The highest synergistic combination was DZ‑Nep + panobinostat. Triple treatment was also synergistic. Reduced clonogenicity and increased apoptosis were both induced. It was concluded that the therapeutic potential of the combination of these three drugs in glioblastoma was evident and should be further explored.

Understanding and Targeting Apoptotic Pathways in Ovarian Cancer

Ovarian cancer cells evade the immune system as well as chemotherapeutic and/or biologic treatments through inherent or acquired mechanisms of survival and drug resistance. Depending on the cell type and the stimuli, this threshold can range from external forces such as blunt trauma to programmed processes such as apoptosis, autophagy, or necroptosis. This review focuses on apoptosis, which is one form of programmed cell death. It highlights the multiple signaling pathways that promote or inhibit apoptosis and reviews current clinical therapies that target apoptotic pathways in ovarian cancer.

Epigenetic Dysregulation at the Crossroad of Women's Cancer

An increasingly number of women of all age groups are affected by cancer, despite substantial progress in our understanding of cancer pathobiology, the underlying genomic alterations and signaling cascades, and cellular-environmental interactions. Though our understanding of women’s cancer is far more complete than ever before, there is no comprehensive model to explain the reasons behind the increased incidents of certain reproductive cancer among older as well as younger women. It is generally suspected that environmental and life-style factors affecting hormonal and growth control pathways might help account for the rise of women’s cancers in younger age, as well, via epigenetic mechanisms. Epigenetic regulators play an important role in orchestrating an orderly coordination of cellular signals in gene activity in response to upstream signaling and/or epigenetic modifiers present in a dynamic extracellular milieu. Here we will discuss the broad principles of epigenetic regulation of DNA methylation and demethylation, histone acetylation and deacetylation, and RNA methylation in women’s cancers in the context of gene expression, hormonal action, and the EGFR family of cell surface receptor tyrosine kinases. We anticipate that a better understanding of the epigenetics of women’s cancers may provide new regulatory leads and further fuel the development of new epigenetic biomarkers and therapeutic approaches.

EZH2 promotes invasion and tumour glycolysis by regulating STAT3 and FoxO1 signalling in human OSCC cells

The enhancer of zeste homolog 2 (EZH2), known as a member of the polycomb group (PcG) proteins, is an oncogene overexpressed in a variety of human cancers. Here, we found that EZH2 correlated with poor survival of oral squamous cell carcinoma (OSCC) patients using immunohistochemistry staining. EZH2 overexpression led to a significant induction in tumour glycolysis, Epithelial‐mesenchymal transition (EMT), migration and invasion of OSCC cells. Conversely, silencing of EZH2 inhibited tumour glycolysis, EMT, migration and invasion in OSCC cells. Ectopic overexpression of EZH2 increased phosphorylation of STAT3 at pY705 and decreased FoxO1 expression, and FoxO1 expression was enhanced when inhibiting STAT3. In addition, EZH2 overexpression led to a significant decrease in FoxO1 mRNA levels in nude mice xenograft. These results indicated that regulation of EZH2 might have the potential to be targeted for OSCC treatment.

The Role of Intra-Tumoral Heterogeneity and Its Clinical Relevance in Epithelial Ovarian Cancer Recurrence and Metastasis

Epithelial ovarian cancer is the deadliest gynecologic cancer, due in large part to recurrent tumors. Recurrences tend to have metastasized, mainly in the peritoneal cavity and developed resistance to the first line chemotherapy. Key to the progression and ultimate lethality of ovarian cancer is the existence of extensive intra-tumoral heterogeneity (ITH). In this review, we describe the genetic and epigenetic changes that have been reported to give rise to different cell populations in ovarian cancer. We also describe at length the contributions made to heterogeneity by both linear and parallel models of clonal evolution and the existence of cancer stem cells. We dissect the key biological signals from the tumor microenvironment, both directly from other cell types in the vicinity and soluble or circulating factors. Finally, we discuss the impact of tumor heterogeneity on the choice of therapeutic approaches in the clinic. Variability in ovarian tumors remains a major barrier to effective therapy, but by leveraging future research into tumor heterogeneity, we may be able to overcome this barrier and provide more effective, personalized therapy to patients.

Diagnostic Value of the EZH2 Immunomarker in Malignant Effusion Cytology

BACKGROUND

Differentiating reactive mesothelial cells from metastatic carcinoma in effusion cytology is a challenging task. The application of at least 4 monoclonal antibodies including 2 epithelial markers (Ber-EP4, MOC-31, CEA, or B72.3) and 2 mesothelial markers (calretinin, WT-1, CK5/6, or HBME-1) are often useful in this distinction; however, it is not readily available in many resource-limited developing countries. Aberrant immunoexpression of enhancer of zeste homolog 2 (EZH2), a transcriptional repressor involved in cancer progression, is observed widely in various malignancy. In this study, we evaluate the diagnostic value of EZH2 as a single reliable immunomarker for malignancy in effusion samples.

METHODS

A total of 108 pleural, peritoneal, and pericardial effusions/washings diagnosed as unequivocally reactive (n = 41) and metastatic carcinoma (n = 67) by cytomorphology over 18 months were reviewed. Among the metastatic carcinoma cases, 54 were adenocarcinoma and others were squamous cell carcinoma (n = 1), carcinosarcoma (n = 1), and carcinoma of undefined histological subtypes (n = 11). Cell block sections were immunostained by EZH2 (Cell Marque, USA). The percentages of EZH2-immunolabeled cells over the total cells of interest were calculated. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off score to define EZH2 immunopositivity.

RESULTS

A threshold of 8% EZH2-immunolabeled cells allows distinction between malignant and reactive mesothelial cells, with 95.5% sensitivity, 100% specificity, 100% positive predictive value, and 93.2% negative predictive value (p < 0.0001). The area under the curve was 0.988.

CONCLUSION

EZH2 is a promising diagnostic biomarker for malignancy in effusion cytology which is inexpensive yet trustworthy and could potentially be used routinely in countries under considerable economic constraints.

The polypeptide GALNT6 Displays Redundant Functions upon Suppression of its Closest Homolog GALNT3 in Mediating Aberrant O-Glycosylation, Associated with Ovarian Cancer Progression

Epithelial ovarian cancer (EOC) represents the most lethal gynecologic malignancy; a better understanding of the molecular mechanisms associated with EOC etiology could substantially improve EOC management. Aberrant O-glycosylation in cancer is attributed to alteration of N-acetylgalactosaminyltransferases (GalNAc-Ts). Reports suggest a genetic and functional redundancy between GalNAc-Ts, and our previous data are indicative of an induction of GALNT6 expression upon GALNT3 suppression in EOC cells. We performed single GALNT3 and double GALNT3/T6 suppression in EOC cells, using a combination of the CRISPR-Cas9 system and shRNA-mediated gene silencing. The effect of single GALNT3 and double GALNT3/T6 inhibition was monitored both in vitro (on EOC cells roliferation, migration, and invasion) and in vivo (on tumor formation and survival of experimental animals). We confirmed that GALNT3 gene ablation leads to strong and rather compensatory GALNT6 upregulation in EOC cells. Moreover, double GALNT3/T6 suppression was significantly associated with stronger inhibitory effects on EOC cell proliferation, migration, and invasion, and accordingly displayed a significant increase in animal survival rates compared with GALNT3-ablated and control (Ctrl) EOC cells. Our data suggest a possible functional redundancy of GalNAc-Ts (GALNT3 and T6) in EOC, with the perspective of using both these enzymes as novel EOC biomarkers and/or therapeutic targets.

Histone Methyltransferase EZH2: A Therapeutic Target for Ovarian Cancer

Ovarian cancer is the fifth leading cause of cancer-related deaths in females in the United States. There were an estimated 22,440 new cases and 14,080 deaths due to ovarian cancer in 2017. Most patients present with advanced-stage disease, revealing the urgent need for new therapeutic strategies targeting pathways of tumorigenesis and chemotherapy resistance. While multiple genomic changes contribute to the progression of this aggressive disease, it has become increasingly evident that epigenetic events play a pivotal role in ovarian cancer development. One of the well-studied epigenetic modifiers, the histone methyltransferase EZH2, is a member of polycomb repressive complex 2 (PRC2) and is commonly involved in transcriptional repression. EZH2 is the enzymatic catalytic subunit of the PRC2 complex that can alter gene expression by trimethylating lysine 27 on histone 3 (H3K27). In ovarian cancer, EZH2 is commonly overexpressed and therefore potentially serves as an effective therapeutic target. Multiple small-molecule inhibitors are being developed to target EZH2, which are now in clinical trials. Thus, in this review, we highlight the progress made in EZH2-related research in ovarian cancer and discuss the potential utility of targeting EZH2 with available small-molecule inhibitors for ovarian cancer. Mol Cancer Ther; 17(3); 591-602. ©2018 AACR.

Epigenetic Regulation of EMT (Epithelial to Mesenchymal Transition) and Tumor Aggressiveness: A View on Paradoxical Roles of KDM6B and EZH2

EMT (epithelial to mesenchymal transition) is a plastic phenomenon involved in metastasis formation. Its plasticity is conferred in a great part by its epigenetic regulation. It has been reported that the trimethylation of lysine 27 histone H3 (H3K27me3) was a master regulator of EMT through two antagonist enzymes that regulate this mark, the methyltransferase EZH2 (enhancer of zeste homolog 2) and the lysine demethylase KDM6B (lysine femethylase 6B). Here we report that EZH2 and KDM6B are overexpressed in numerous cancers and involved in the aggressive phenotype and EMT in various cell lines by regulating a specific subset of genes. The first paradoxical role of these enzymes is that they are antagonistic, but both involved in cancer aggressiveness and EMT. The second paradoxical role of EZH2 and KDM6B during EMT and cancer aggressiveness is that they are also inactivated or under-expressed in some cancer types and linked to epithelial phenotypes in other cancer cell lines. We also report that new cancer therapeutic strategies are targeting KDM6B and EZH2, but the specificity of these treatments may be increased by learning more about the mechanisms of action of these enzymes and their specific partners or target genes in different cancer types.

Epigenetics in ovarian cancer: premise, properties, and perspectives

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemical therapy increase patient mortality. Therefore, it is both urgent and important to identify biomarkers facilitating early identification and novel agents preventing recurrence. Accumulating evidence demonstrates that epigenetic aberrations (particularly histone modifications) are crucial in tumor initiation and development. Histone acetylation and methylation are respectively regulated by acetyltransferases-deacetylases and methyltransferases-demethylases, both of which are implicated in ovarian cancer pathogenesis. In this review, we summarize the most recent discoveries pertaining to ovarian cancer development arising from the imbalance of histone acetylation and methylation, and provide insight into novel therapeutic interventions for the treatment of ovarian carcinoma.

[Construction of EZH2 Knockout Animal Model by CRISPR/Cas9 Technology]

BACKGROUND

It has been proven that CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated 9) system was the modern gene-editing technology through the constitutive expression of nucleases Cas9 in the mammalian, which binds to the specific site in the genome mediated by single-guide RNA (sgRNA) at desired genomic loci. The aim of this study is that the animal model of EZH2 gene knockout was constructed using CRISPR/Cas9 technology.

METHODS

In this study, we designed two single-guide RNAs targeting the Exon3 and Exon4 of EZH2 gene. Then, their gene-targeting efficiency were detected by SURVEYOR assay. The lentivirus was perfused into the lungs of mice by using a bronchial tube and detected by immunohistochemistry and qRT-PCR.

RESULTS

The experimental results of NIH-3T3 cells verify that the designed sgEZH2 can efficiently effect the cleavage of target DNA by Cas9 in vitro. The immunohistochemistry and qRT-PCR results showed that the EZH2 expression in experimental group was significantly decreased in the mouse lung tissue.

CONCLUSIONS

The study successfully designed two sgRNA which can play a knock-out EZH2 function. An EZH2 knockout animal model was successfully constructed by CRISPR/Cas9 system, and it will be an effective animal model for studying the functions and mechanisms of EZH2.

Identifying genes as potential prognostic indicators in patients with serous ovarian cancer resistant to carboplatin using integrated bioinformatics analysis

Serous ovarian cancer (SOC) accounts for >50% of all epithelial ovarian cancers. However, patients with SOC present with various degrees of response to platinum‑based chemotherapy and, thus, their survival may differ. The present study aimed to identify the candidate genes involved in the carcinogenesis and drug resistance of SOC by analyzing the microarray datasets GDS1381 and GDS3592. GDS1381 and GDS3592 were downloaded from the Gene Expression Omnibus database (https://www.ncbi.nlm.nih.gov/gds/). A total of 219 differentially expressed genes (DEGs) were identified. Potential genes that may predict the response to carboplatin and, thus, the prognosis of SOC were analyzed. The enriched functions and pathways of DEGs included extracellular region, extracellular space and extracellular exosome, among others. Upon screening the upregulated and downregulated genes on the connectivity map, 10 small‑molecule drugs were identified that may be helpful in improving drug sensitivity in patients with ovarian cancer. A total of 30 hub genes were screened for further analysis after constructing the protein‑to‑protein interaction network. Through survival analysis, comparison of genes across numerous analyses, and immunohistochemistry, GNAI1, non‑structural maintenance of chromosomes (non‑SMC) condensin I complex subunit H (NCAPH), matrix metallopeptidase 9 (MMP9), aurora kinase A (AURKA) and enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) were identified as the key molecules that may be involved in the carcinogenesis and carboplatin resistance of SOC. In conclusion, GNAI1, NCAPH, MMP9, AURKA and EZH2 should be examined in further studies for the possibility of their participation in the carcinogenesis and carboplatin response of SOC.

Enhancer of zeste homolog 2 blockade by RNA interference is implicated with inhibited proliferation, invasion and promoted apoptosis in endometrial carcinoma

Endometrial carcinoma is the most common gynecological malignancy of the female genital tract worldwide (2012). Enhancer of zeste homolog 2 (EZH2), a critical component of the polycomb repressive complex 2, has been found to be associated with multiple biological processes and is overexpressed in multiple types of cancer. Previous studies have demonstrated that EZH2 is associated with endometrial carcinoma. The present study investigated the expression and biology function of EZH2 in endometrial cancer (EC). It was found that EZH2 levels were markedly increased in endometrial cancer tissues compared with that in adjacent normal tissues. EZH2 was significantly overexpressed in 3 separate endometrial cancer cell lines (Ishikawa, RL95-2 and HEC1-A) when compared with the normal endometrial cell line ESC. Additionally, small interfering RNA was used to investigate the role of EZH2 in endometrial carcinoma cell proliferation, and the results showed that EZH2 knockdown suppressed the proliferation of endometrial carcinoma cells in vitro. Furthermore, EZH2 knockdown induced apoptosis of human EC cells by promoting the expression of pro-apoptosis protein caspase 3, caspase 9, BCL2 associated X and decreasing the expression of anti-apoptosis protein Bcl-2. Finally, the present study demonstrated that EZH2 knockdown suppressed the invasion of EC cells through downregulation of the epithelial-mesenchymal transition. Collectively, these data demonstrate that EZH2 is frequently overexpressed in EC cells and its overexpression is associated with promoting the proliferation and invasion and decreasing the apoptosis of EC cells, suggesting that EZH2 may provide potential therapeutic targets for treatment of endometrial carcinoma.

Migration/Invasion of Malignant Gliomas and Implications for Therapeutic Treatment

Malignant tumors of the central nervous system (CNS) are among cancers with the poorest prognosis, indicated by their association with tumors of high-level morbidity and mortality. Gliomas, the most common primary CNS tumors that arise from neuroglial stem or progenitor cells, have estimated annual incidence of 6.6 per 100,000 individuals in the USA, and 3.5 per 100,000 individuals in Taiwan. Tumor invasion and metastasis are the major contributors to the deaths in cancer patients. Therapeutic goals including cancer stem cells (CSC), phenotypic shifts, EZH2/AXL/TGF-β axis activation, miRNAs and exosomes are relevant to GBM metastasis to develop novel targeted therapeutics for GBM and other brain cancers. Herein, we highlight tumor metastasis in our understanding of gliomas, and illustrate novel exosome therapeutic approaches in glioma, thereby paving the way towards innovative therapies in neuro-oncology.

EZH2 inhibition promotes epithelial-to-mesenchymal transition in ovarian cancer cells

Cancer cells acquire essential characteristics for metastatic dissemination through the process of epithelial-to-mesenchymal transition (EMT), which is regulated by gene expression and chromatin remodeling changes. The enhancer of zeste homolog 2 (EZH2), the catalytic subunit of the polycomb repressive complex 2 (PRC2), catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) to repress gene transcription. Here we report the functional roles of EZH2-catalyzed H3K27me3 during EMT in ovarian cancer (OC) cells. TGF-β-induced EMT in SKOV3 OC cells was associated with decreased levels of EZH2 and H3K27me3 (P<0.05). These effects were delayed (~72 h relative to EMT initiation) and coincided with increased (>15-fold) expression of EMT-associated transcription factors ZEB2 and SNAI2. EZH2 knockdown (using siRNA) or enzymatic inhibition (by GSK126) induced EMT-like changes in OC cells. The EMT regulator ZEB2 was upregulated in cells treated with either approach. Furthermore, TGF-β enhanced expression of ZEB2 in EZH2 siRNA- or GSK126-treated cells (P<0.01), suggesting that H3K27me3 plays a role in TGF-β-stimulated ZEB2 induction. Chromatin immunoprecipitation assays confirmed that TGF-β treatment decreased binding of EZH2 and H3K27me3 to the ZEB2 promoter (P<0.05). In all, these results demonstrate that EZH2, by repressing ZEB2, is required for the maintenance of an epithelial phenotype in OC cells.

Chromatin organization regulated by EZH2-mediated H3K27me3 is required for OPN-induced migration of bone marrow-derived mesenchymal stem cells

Osteopontin (OPN) is a chemokine-like extracellular matrix-associated protein involved in the migration of bone marrow-derived mesenchymal stem cells (BMSCs). An increasing number of studies have found that chromatin organization may affect cellular migration. However, whether OPN regulates chromatin organization is not understood, nor are the underlying molecular mechanisms. In this study, we investigated the link between chromatin organization and BMSC migration and demonstrated that OPN-mediated BMSC migration leads to elevated levels of heterochromatin marker histone H3 lysine 27 trimethylation (H3K27me3) through the methyltransferase EZH2. The expression of EZH2 reorganizes the chromatin structure of BMSCs. Pharmacological inhibition or depletion of EZH2 blocks BMSC migration. Moreover, using an atomic force microscope (AFM), we found that chromatin decondensation alters the mechanical properties of the nucleus. In addition, inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) signals represses OPN-promoted chromatin condensation and cell migration. Thus, our results identify a mechanism by which ERK1/2 signalling drives specific chromatin modifications in BMSCs, which alters chromatin organization and thereby enables OPN-mediated BMSC migration.

EZH2 contributes to the response to PARP inhibitors through its PARP-mediated poly-ADP ribosylation in breast cancer

Inhibitors against poly (ADP-ribose) polymerase (PARP) are promising targeted agents currently used to treat BRCA-mutant ovarian cancer and are in clinical trials for other cancer types, including BRCA-mutant breast cancer. To enhance the clinical response to PARP inhibitors (PARPis), understanding the mechanisms underlying PARPi sensitivity is urgently needed. Here, we show enhancer of zeste homolog 2 (EZH2), an enzyme that catalyzes H3 lysine trimethylation and associates with oncogenic function, contributes to PARPi sensitivity in breast cancer cells. Mechanistically, upon oxidative stress or alkylating DNA damage, PARP1 interacts with and attaches poly-ADP-ribose (PAR) chains to EZH2. PARylation of EZH2 by PARP1 then induces PRC2 complex dissociation and EZH2 downregulation, which in turn reduces EZH2-mediated H3 trimethylation. In contrast, inhibition of PARP by PARPi attenuates alkylating DNA damage-induced EZH2 downregulation, thereby promoting EZH2-mediated gene silencing and cancer stem cell property compared with PARPi-untreated cells. Moreover, the addition of an EZH2 inhibitor sensitizes the BRCA-mutant breast cells to PARPi. Thus, these results may provide a rationale for combining PARP and EZH2 inhibition as a therapeutic strategy for BRCA-mutated breast and ovarian cancers.

EZH2 enhances the invasive capability of renal cell carcinoma cells via activation of STAT3

The enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) gene has been recognized to be a proto-oncogene and to be linked to human malignancies. However, the additional functions of EZH2 in renal cell carcinoma (RCC) are not completely understood. In the present study, a possible role of EZH2 in RCC was identified. EZH2 was demonstrated to promote the cell proliferation and invasion potential of 769-P cells, and inhibition of EZH2 was demonstrated to prevent these two processes in 786-O cells. Mechanically, EZH2 was demonstrated to increase the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and upregulate 72 kDa type IV collagenase (MMP-2) expression. When cells were treated with small interfering RNA targeting STAT3 or Stattic, a specific inhibitor of STAT3, the invasive ability of the cells was decreased and downregulation of MMP-2 was observed. Based on these results, in the present study it was hypothesized that EZH2 may serve a critical role in the progression of RCC. Its ability to facilitate invasion makes EZH2 a promising target for the management of advanced RCC.

EZH2 promotes cell migration and invasion but not alters cell proliferation by suppressing E-cadherin, partly through association with MALAT-1 in pancreatic cancer

Enhancer of zeste homolog 2 (EZH2) is an essential component of the polycomb repressive complex 2 (PRC2), which is required for epigenetic silencing of target genes, including those affecting cancer progression. Its role in pancreatic cancer remains to be clarified; therefore, we investigated the effects of aberrantly expressed EZH2 on pancreatic cancer. We found that EZH2 expression is up-regulated in pancreatic cancer tissues and positively correlated with lymph node metastasis and advanced clinical stage in pancreatic cancer patients. EZH2 knockdown in pancreatic cancer cell lines inhibited cell migration and invasion, but did not alter cell proliferation. Silencing of EZH2 also increased E-cadherin expression in vitro, and E-cadherin expression was inversely correlated with EZH2 expression in pancreatic cancer tissue samples. Patients with high EZH2 and low E-cadherin expression had the worst prognosis. RIP and ChIP assays suggest that EZH2 is recruited to the E-cadherin promoter by the long non-coding RNA, MALAT-1 (metastasis associated in lung adenocarcinoma transcript 1), where it represses E-cadherin expression. Our results show that EZH2-based therapies may be an option for the treatment of pancreatic cancer.