Integration of estrogen and Wnt signaling circuits by the polycomb group protein EZH2 in breast cancer cells

Overexpression of CDCA7 predicts poor prognosis and induces EZH2-mediated progression of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with high proliferative and metastatic phenotypes. CDCA7, a new member of the cell division cycle associated family of genes, is involved in embryonic development and dysregulated in various types of human cancer. However, the biological role and molecular mechanism of CDCA7 in TNBC have not been defined. Herein, we found that CDCA7 was preferentially and markedly expressed in TNBC cell lines and tissues. High expression of CDCA7 was associated with metastatic relapse status and predicted poorer disease-free survival in patients with TNBC. We observed that CDCA7 silencing in TNBC cell lines effectively impaired cell proliferation, invasion and migration in vitro. Importantly, depletion of CDCA7 strongly reduced the tumorigenicity and distant colonization capacities of TNBC cells in vivo. Furthermore, CDCA7 increased the expression of EZH2, a marker of aggressive breast cancer that is involved in tumor progression, by enhancing the transcriptional activity of its promoter. This increase in EZH2 expression was essential for the CDCA7-mediated effects on TNBC progression. Finally, our immunohistochemical analysis revealed that the CDCA7/EZH2 axis was clinical relevant. These findings suggest CDCA7 plays a crucial role in TNBC progression by transcriptionally upregulating EZH2 and might be a potential prognostic factor and therapeutic target in TNBC.

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.

Targeting EZH2 reactivates a breast cancer subtype-specific anti-metastatic transcriptional program

Emerging evidence has illustrated the importance of epigenomic reprogramming in cancer, with altered post-translational modifications of histones contributing to pathogenesis. However, the contributions of histone modifiers to breast cancer progression are unclear, and how these processes vary between molecular subtypes has yet to be adequately addressed. Here we report that genetic or pharmacological targeting of the epigenetic modifier Ezh2 dramatically hinders metastatic behaviour in both a mouse model of breast cancer and patient-derived xenografts reflective of the Luminal B subtype. We further define a subtype-specific molecular mechanism whereby EZH2 maintains H3K27me3-mediated repression of the FOXC1 gene, thereby inactivating a FOXC1-driven, anti-invasive transcriptional program. We demonstrate that higher FOXC1 is predictive of favourable outcome specifically in Luminal B breast cancer patients and establish the use of EZH2 methyltransferase inhibitors as a viable strategy to block metastasis in Luminal B breast cancer, where options for targeted therapy are limited.

Histone modifications in cancer can contribute to pathogenesis. Here, the authors demonstrate that targeting epigenetic modifier Ezh2 hinders metastatic behaviour in Luminal B breast cancer models, and highlight a mechanism where Ezh2 contributes to metastatic behaviour by repression of FOXC1.

Noncanonical NF-κB in Cancer

The NF-κB pathway is a critical regulator of immune responses and is often dysregulated in cancer. Two NF-κB pathways have been described to mediate these responses, the canonical and the noncanonical. While understudied compared to the canonical NF-κB pathway, noncanonical NF-κB and its components have been shown to have effects, usually protumorigenic, in many different cancer types. Here, we review noncanonical NF-κB pathways and discuss its important roles in promoting cancer. We also discuss alternative NF-κB-independent functions of some the components of noncanonical NF-κB signaling. Finally, we discuss important crosstalk between canonical and noncanonical signaling, which blurs the two pathways, indicating that understanding the full picture of NF-κB regulation is critical to deciphering how this broad pathway promotes oncogenesis.

Functional and therapeutic significance of EZH2 in urological cancers

The enhancer of zeste homolog 2 (EZH2) is a core subunit of the polycomb repressor complex 2 (PRC2), which is overexpressed in numerous cancers and mutated in several others. Notably, EZH2 acts not only a critical epigenetic repressor through its role in histone methylation, it is also an activator of gene expression, acting through multiple signaling pathways in distinct cancer types. Increasing evidence suggests that EZH2 is an oncogene and is central to initiation, growth and progression of urological cancers. In this review, we highlight the critical role of EZH2 as a master regulator of tumorigenesis in the prostate, bladder and the kidney through epigenetic control of transcription as well as a modulation of various critical signaling pathways. We also discuss the promise and challenges for EZH2 inhibitors as future anticancer therapeutics, some of which are currently in clinical trials.

EZH2 inhibitors sensitize myeloma cell lines to panobinostat resulting in unique combinatorial transcriptomic changes

Multiple myeloma (MM) remains a largely incurable hematologic cancer due to an inability to broadly target inevitable drug-resistant relapse. Epigenetic abnormalities are abundantly present in multiple myeloma and have increasingly demonstrated critical roles for tumor development and relapse to standard therapies. Accumulating evidence suggests that the histone methyltransferase EZH2 is aberrantly active in MM. We tested the efficacy of EZH2 specific inhibitors in a large panel of human MM cell lines (HMCLs) and found that only a subset of HMCLs demonstrate single agent sensitivity despite ubiquitous global H3K27 demethylation. Pre-treatment with EZH2 inhibitors greatly enhanced the sensitivity of HMCLs to the pan-HDAC inhibitor panobinostat in nearly all cases regardless of single agent EZH2 inhibitor sensitivity. Transcriptomic profiling revealed large-scale transcriptomic alteration by EZH2 inhibition highly enriched for cancer-related pathways. Combination treatment greatly increased the scale of gene expression change with a large portion of differentially expressed genes being unique to the combination. Transcriptomic analysis demonstrated that combination treatment further perturbed oncogenic pathways and signaling nodes consistent with an antiproliferative/pro-apoptotic state. We conclude that combined inhibition of HDAC and EZH2 inhibitors is a promising therapeutic strategy to broadly target the epigenetic landscape of aggressive MM.

Role of EZH2 in cancer stem cells: from biological insight to a therapeutic target

Epigenetic modifications in cancer stem cells largely result in phenotypic and functional heterogeneity in many solid tumors. Increasing evidence indicates that enhancer of zeste homolog 2 (EZH2), the catalytic subunit of Polycomb repressor complex 2, is highly expressed in cancer stem cells of numerous malignant tumors and has a critical function in cancer stem cell expansion and maintenance. Here, we review up-to-date information regarding EZH2 expression patterns, functions, and molecular mechanisms in cancer stem cells in various malignant tumors and discuss the therapeutic potential of targeting EZH2 in tumors.

ZRANB1 Is an EZH2 Deubiquitinase and a Potential Therapeutic Target in Breast Cancer

Although EZH2 enzymatic inhibitors have shown antitumor effects in EZH2-mutated lymphoma and ARID1A-mutated ovarian cancer, many cancers do not respond because EZH2 can promote cancer independently of its histone methyltransferase activity. Here we identify ZRANB1 as the EZH2 deubiquitinase. ZRANB1 binds, deubiquitinates, and stabilizes EZH2. Depletion of ZRANB1 in breast cancer cells results in EZH2 destabilization and growth inhibition. Systemic delivery of ZRANB1 small interfering RNA (siRNA) leads to marked antitumor and antimetastatic effects in preclinical models of triple-negative breast cancer (TNBC). Intriguingly, a small-molecule inhibitor of ZRANB1 destabilizes EZH2 and inhibits the viability of TNBC cells. In patients with breast cancer, ZRANB1 levels correlate with EZH2 levels and poor survival. These findings suggest the therapeutic potential for targeting the EZH2 deubiquitinase ZRANB1.

Expression of enhancer of zeste homolog 2 (EZH2) protein in histiocytic and dendritic cell neoplasms with evidence for p-ERK1/2-related, but not MYC- or p-STAT3-related cell signaling

EZH2 is an important enzymatic subunit of the epigenetic regulator polycomb repressive complex 2 (PRC2), which controls gene silencing through post-translational modification, and is overexpressed in various carcinomas and hematopoietic neoplasms. We found that the majority of cases of histiocytic and dendritic cell neoplasms, including histiocytic sarcoma, follicular dendritic cell sarcoma, Langerhans cell histiocytosis, and interdigitating dendritic cell sarcoma, show strong EZH2 expression by immunohistochemical staining, in contrast to benign histiocytic lesions and normal cellular counterparts, which did not show EZH2 expression, suggesting that this molecule may function as an oncogenic protein in these neoplasms. We correlated EZH2 expression with that of p-ERK1/2, MYC, and p-STAT3, potential regulators of EZH2, and found that 60-80% of these cases showed strong p-ERK1/2 expression, and only a minority of cases showed positivity for MYC or p-STAT3 in neoplastic cells. In cases of follicular dendritic cell sarcoma, Langerhans cell histiocytosis, histiocytic sarcoma, and interdigitating dendritic cell sarcoma with strong EZH2 expression, 90%, 89%, 70%, and 100% of cases showed co-expression of p-ERK1/2 with EZH2, respectively, while only a small percentage of these cases showed MYC or p-STAT3 co-expression with EZH2 (≤30%). These findings suggest that the p-ERK1/2 signaling cascade, but not the p-STAT3 and MYC signaling cascades, may regulate EZH2 expression in histiocytic and dendritic cell neoplasms, and that EZH2 and the p-ERK1/2 signaling cascade could serve as therapeutic targets for the treatment of these neoplasms. Interestingly, only a minority of cases of blastic plasmacytoid dendritic cell neoplasm exhibited high EZH2 expression, and only a minority of these cases showed p-ERK1/2 co-expression, suggesting that alternative mechanisms may contribute to tumorigenesis in this aggressive neoplasm.

Epigenetic regulation of cancer progression by EZH2: from biological insights to therapeutic potential

Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and a catalytic component of PRC2, catalyzes tri-methylation of histone H3 at Lys 27 (H3K27me3) to regulate gene expression through epigenetic machinery. EZH2 also functions both as a transcriptional suppressor and a transcriptional co-activator, depending on H3K27me3 or not and on the different cellular contexts. Unsurprisingly, numerous studies have highlighted the role of EZH2 in cancer development and progression. Through modulating critical gene expression, EZH2 promotes cell survival, proliferation, epithelial to mesenchymal, invasion, and drug resistance of cancer cells. The tumor suppressive effects of EZH2 are also identified. What is more, EZH2 has decisive roles in immune cells (for example, T cells, NK cells, dendritic cells and macrophages), which are essential components in tumor microenvironment. In this review, we aim to discuss the molecular functions of EZH2, highlight recent findings regarding the physiological functions and related regulation of EZH2 in cancer pathogenesis. Furthermore, we summarized and updated the emerging roles of EZH2 in tumor immunity, and current pre-clinical and clinical trials of EZH2 inhibitors in cancer therapy.

Oestrogen, progesterone and stem cells: the discordant trio in endometriosis?

Oestrogen–progesterone signalling is highly versatile and critical for the maintenance of healthy endometrium in humans. The genomic and nongenomic signalling cascades initiated by these hormones in differentiated cells of endometrium have been the primary focus of research since 1920s. However, last decade of research has shown a significant role of stem cells in the maintenance of a healthy endometrium and the modulatory effects of hormones on these cells. Endometriosis, the growth of endometrium outside the uterus, is very common in infertile patients and the elusiveness in understanding of disease pathology causes hindrance in selection of treatment approaches to enhance fertility. In endometriosis, the stem cells are dysfunctional as it can confer progesterone resistance to their progenies resulting in disharmony of hormonal orchestration of endometrial homeostasis. The bidirectional communication between stem cell signalling pathways and oestrogen–progesterone signalling is found to be disrupted in endometriosis though it is not clear which precedes the other. In this paper, we review the intricate connection between hormones, stem cells and the cross-talks in their signalling cascades in normal endometrium and discuss how this is deregulated in endometriosis. Re-examination of the oestrogen–progesterone dependency of endometrium with a focus on stem cells is imperative to delineate infertility associated with endometriosis and thereby aid in designing better treatment modalities.

Epigenetic regulation of cancer biology and anti-tumor immunity by EZH2

Polycomb group proteins regulate chromatin structure and have an important regulatory role on gene expression in various cell types. Two polycomb group complexes (Polycomb repressive complex 1 (PRC1) and 2 (PRC2)) have been identified in mammalian cells. Both PRC1 and PRC2 compact chromatin, and also catalyze histone modifications. PRC1 mediates monoubiquitination of histone H2A, whereas PRC2 catalyzes methylation of histone H3 on lysine 27. These alterations of histones can lead to altered gene expression patterns by regulating chromatin structure. Numerous studies have highlighted the role of the PRC2 catalytic component enhancer of zeste homolog 2 (EZH2) in neoplastic development and progression, and EZH2 mutations have been identified in various malignancies. Through modulating the expression of critical genes, EZH2 is actively involved in fundamental cellular processes such as cell cycle progression, cell proliferation, differentiation and apoptosis. In addition to cancer cells, EZH2 also has a decisive role in the differentiation and function of T effector and T regulatory cells. In this review we summarize the recent progress regarding the role of EZH2 in human malignancies, highlight the molecular mechanisms by which EZH2 aberrations promote the pathogenesis of cancer, and discuss the anti-tumor effects of EZH2 targeting via activating direct anti-cancer mechanisms and anti-tumor immunity.

Integrated bioinformatics analysis of chromatin regulator EZH2 in regulating mRNA and lncRNA expression by ChIP sequencing and RNA sequencing

Enhancer of zeste homolog 2 (EZH2), a dynamic chromatin regulator in cancer, represents a potential therapeutic target showing early signs of promise in clinical trials. EZH2 ChIP sequencing data in 19 cell lines and RNA sequencing data in ten cancer types were downloaded from GEO and TCGA, respectively. Integrated ChIP sequencing analysis and co-expressing analysis were conducted and both mRNA and long noncoding RNA (lncRNA) targets were detected. We detected a median of 4,672 mRNA targets and 4,024 lncRNA targets regulated by EZH2 in 19 cell lines. 20 mRNA targets and 27 lncRNA targets were found in all 19 cell lines. These mRNA targets were enriched in pathways in cancer, Hippo, Wnt, MAPK and PI3K-Akt pathways. Co-expression analysis confirmed numerous targets, mRNA genes (RRAS, TGFBR2, NUF2 and PRC1) and lncRNA genes (lncRNA LINC00261, DIO3OS, RP11-307C12.11 and RP11-98D18.9) were potential targets and were significantly correlated with EZH2. We predicted genome-wide potential targets and the role of EZH2 in regulating as a transcriptional suppressor or activator which could pave the way for mechanism studies and the targeted therapy of EZH2 in cancer.

PRC2 Is Dispensable in Vivo for β-Catenin-Mediated Repression of Chondrogenesis in the Mouse Embryonic Cranial Mesenchyme

A hallmark of craniofacial development is the differentiation of multiple cell lineages in close proximity to one another. The mouse skull bones and overlying dermis are derived from the cranial mesenchyme (CM). Cell fate selection of the embryonic cranial bone and dermis in the CM requires Wnt/β-catenin signaling, and loss of β-catenin leads to an ectopic chondrogenic cell fate switch. The mechanism by which Wnt/β-catenin activity suppresses the cartilage fate is unclear. Upon conditional deletion of β-catenin in the CM, several key determinants of the cartilage differentiation program, including Sox9, become differentially expressed. Many of these differentially expressed genes are known targets of the Polycomb Repressive Complex 2 (PRC2). Thus, we hypothesized that PRC2 is required for Wnt/β-catenin-mediated repression of chondrogenesis in the embryonic CM. We find that β-catenin can physically interact with PRC2 components in the CM in vivo. However, upon genetic deletion of Enhancer of Zeste homolog 2 (EZH2), the catalytic component of PRC2, chondrogenesis remains repressed and the bone and dermis cell fate is preserved in the CM. Furthermore, loss of β-catenin does not alter either the H3K27me3 enrichment levels genome-wide or on cartilage differentiation determinants, including Sox9. Our results indicate that EZH2 is not required to repress chondrogenesis in the CM downstream of Wnt/β-catenin signaling.

EZH2-mediated Puma gene repression regulates non-small cell lung cancer cell proliferation and cisplatin-induced apoptosis

Polycomb group (PcG) proteins are highly conserved epigenetic effectors that maintain the silenced state of genes. EZH2 is the catalytic core and one of the most important components of the polycomb repressive complex 2 (PRC2). In non-small cell lung cancer (NSCLC) cells and primary lung tumors, we found that PRC2 components, including EZH2, are overexpressed. High levels of EZH2 protein were associated with worse overall survival rate in NSCLC patients. RNA interference mediated attenuation of EZH2 expression blunted the malignant phenotype in this setting, exerting inhibitory effects on cell proliferation, anchorage-independent growth, and tumor development in a xenograft mouse model. Unexpectedly, we discovered that, in the suppression of EZH2, p53 upregulated modulator of apoptosis (PUMA) expression was concomitantly induced. This is achieved through EZH2 directly binds to the Puma promoter thus epigenetic repression of PUMA expression. Furthermore, cisplatin-induced apoptosis of EZH2-knocking down NSCLC cells was elevated as a consequence of increased PUMA expression. Our work reveals a novel epigenetic regulatory mechanism controlling PUMA expression and suggests that EZH2 offers a candidate molecular target for NSCLC therapy and EZH2-regulated PUMA induction would synergistically increase the sensitivity to platinum agents in non-small cell lung cancers.

EZH2-mediated repression of GSK-3β and TP53 promotes Wnt/β-catenin signaling-dependent cell expansion in cervical carcinoma

Enhancer of zeste homolog 2 (EZH2), a catalytic core component of the Polycomb repressive complex 2 (PRC2), stimulates the silencing of target genes through histone H3 lysine 27 trimethylation (H3K27me3). Recent findings have indicated EZH2 is involved in the development and progression of various human cancers. However, the exact mechanism of EZH2 in the promotion of cervical cancer is largely unknown. Here, we show that EZH2 expression gradually increases during the progression of cervical cancer. We identified a significant positive correlation between EZH2 expression and cell proliferation in vitro and tumor formation in vivo by the up-regulation or down-regulation of EZH2 using CRISPR-Cas9-mediated gene editing technology and shRNA in HeLa and SiHa cells. Further investigation indicated that EZH2 protein significantly accelerated the cell cycle transition from the G0/G1 to S phase. TOP/FOP-Flash reporter assay revealed that EZH2 significantly activated Wnt/β-catenin signaling and the target genes of Wnt/β-catenin pathway were up-regulated, including β-catenin, cyclin D1, and c-myc. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays confirmed that EZH2 inhibited the expression of glycogen synthase kinase-3β (GSK-3β) and TP53 through physically interacting with motifs in the promoters of the GSK-3β and TP53 genes. Additionally, blockage of the Wnt/β-catenin pathway resulted in significant inhibition of cell proliferation, and activation of the Wnt/β-catenin pathway resulted in significant enhancement of cell proliferation, as induced by EZH2. Taken together, our data demonstrate that EZH2 promotes cell proliferation and tumor formation in cervical cancer through activating the Wnt/β-catenin pathway by epigenetic silencing via GSK-3β and TP53.

A Role for Monomethylation of Histone H3-K27 in Gene Activity in Drosophila

Polycomb repressive complex 2 (PRC2) is a conserved chromatin-modifying enzyme that methylates histone H3 on lysine-27 (K27). PRC2 can add one, two, or three methyl groups and the fully methylated product, H3-K27me3, is a hallmark of Polycomb-silenced chromatin. Less is known about functions of K27me1 and K27me2 and the dynamics of flux through these states. These modifications could serve mainly as intermediates to produce K27me3 or they could each convey distinct epigenetic information. To investigate this, we engineered a variant of Drosophila melanogaster PRC2 which is converted into a monomethyltransferase. A single substitution, F738Y, in the lysine-substrate binding pocket of the catalytic subunit, E(Z), creates an enzyme that retains robust K27 monomethylation but dramatically reduced di- and trimethylation. Overexpression of E(Z)-F738Y in fly cells triggers desilencing of Polycomb target genes significantly more than comparable overexpression of catalytically deficient E(Z), suggesting that H3-K27me1 contributes positively to gene activity. Consistent with this, normal genomic distribution of H3-K27me1 is enriched on actively transcribed Drosophila genes, with localization overlapping the active H3-K36me2/3 chromatin marks. Thus, distinct K27 methylation states link to either repression or activation depending upon the number of added methyl groups. If so, then H3-K27me1 deposition may involve alternative methyltransferases beyond PRC2, which is primarily repressive. Indeed, assays on fly embryos with PRC2 genetically inactivated, and on fly cells with PRC2 chemically inhibited, show that substantial H3-K27me1 accumulates independently of PRC2. These findings imply distinct roles for K27me1 vs. K27me3 in transcriptional control and an expanded machinery for methylating H3-K27.

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.

CRISPR-Cas9 screen reveals a MYCN-amplified neuroblastoma dependency on EZH2

Pharmacologically difficult targets, such as MYC transcription factors, represent a major challenge in cancer therapy. For the childhood cancer neuroblastoma, amplification of the oncogene MYCN is associated with high-risk disease and poor prognosis. Here, we deployed genome-scale CRISPR-Cas9 screening of MYCN-amplified neuroblastoma and found a preferential dependency on genes encoding the polycomb repressive complex 2 (PRC2) components EZH2, EED, and SUZ12. Genetic and pharmacological suppression of EZH2 inhibited neuroblastoma growth in vitro and in vivo. Moreover, compared with neuroblastomas without MYCN amplification, MYCN-amplified neuroblastomas expressed higher levels of EZH2. ChIP analysis showed that MYCN binds at the EZH2 promoter, thereby directly driving expression. Transcriptomic and epigenetic analysis, as well as genetic rescue experiments, revealed that EZH2 represses neuronal differentiation in neuroblastoma in a PRC2-dependent manner. Moreover, MYCN-amplified and high-risk primary tumors from patients with neuroblastoma exhibited strong repression of EZH2-regulated genes. Additionally, overexpression of IGFBP3, a direct EZH2 target, suppressed neuroblastoma growth in vitro and in vivo. We further observed strong synergy between histone deacetylase inhibitors and EZH2 inhibitors. Together, these observations demonstrate that MYCN upregulates EZH2, leading to inactivation of a tumor suppressor program in neuroblastoma, and support testing EZH2 inhibitors in patients with MYCN-amplified neuroblastoma.

Involvement of aberrantly activated HOTAIR/EZH2/miR-193a feedback loop in progression of prostate cancer

Background

Though androgen deprivation therapy is the standard treatment for prostate cancer (PCa), most patients would inevitably progress to castration-resistant prostate cancer (CRPC) which is the main cause of PCa death. Therefore, the identification of novel molecular mechanism regulating cancer progression and achievement of new insight into target therapy would be necessary for improving the benefits of PCa patients. This study aims to study the function and regulatory mechanism of HOTAIR/EZH2/miR-193a feedback loop in PCa progression.

Methods

MSKCC and TCGA datasets were used to identify miR-193a expression profile in PCa. Cell Counting Kit-8 (CCK-8) assays, colony formation, invasion, migration, flow cytometry, a xenograft model and Gene Set Enrichment Analysis were used to detect and analyze the biological function of miR-193a. Then, we assessed the role of HOTAIR and EZH2 in regulation of miR-193a expression by using plasmid, lentivirus and small interfering RNA (siRNA). Luciferase reporter assays and chromatin immunoprecipitation assays were performed to detect the transcriptional activation of miR-193a by EZH2 and HOTAIR. Further, qRT-PCR and luciferase reporter assays were conducted to examine the regulatory role of miR-193a controlling the HOTAIR expression in PCa. Finally, the correlation between HOTAIR, EZH2 and miR-193a expression were analyzed using In situ hybridization and immunohistochemistry.

Results

We found that miR-193a was significantly downregulated in metastatic PCa through mining MSKCC and TCGA datasets. In vitro studies revealed that miR-193a inhibited PCa cell growth, suppressed migration and invasion, and promoted apoptosis; in vivo results demonstrated that overexpression of miR-193a mediated by lentivirus dramatically reduced PCa xenograft tumor growth. Importantly, we found EZH2 coupled with HOTAIR to repress miR-193a expression through trimethylation of H3K27 at miR-193a promoter in PC3 and DU145 cells. Interestingly, further evidence illustrated that miR-193a directly targets HOTAIR showing as significantly reduced HOTAIR level in miR-193a overexpressed cells and tissues. The expression level of miR-193a was inversely associated with that of HOTAIR and EZH2 in PCa.

Conclusion

This study firstly demonstrated that miR-193a acted as tumor suppressor in CRPC and the autoregulatory feedback loop of HOTAIR/EZH2/miR-193a served an important mechanism in PCa development. Targeting this aberrantly activated feedback loop may provide a potential therapeutic strategy.

Electronic supplementary material

The online version of this article (doi: 10.1186/s13046-017-0629-7) contains supplementary material, which is available to authorized users.

Bivalent Epigenetic Control of Oncofetal Gene Expression in Cancer

Multiple mechanisms of epigenetic control that include DNA methylation, histone modification, noncoding RNAs, and mitotic gene bookmarking play pivotal roles in stringent gene regulation during lineage commitment and maintenance. Experimental evidence indicates that bivalent chromatin domains, i.e., genome regions that are marked by both H3K4me3 (activating) and H3K27me3 (repressive) histone modifications, are a key property of pluripotent stem cells. Bivalency of developmental genes during the G₁ phase of the pluripotent stem cell cycle contributes to cell fate decisions. Recently, some cancer types have been shown to exhibit partial recapitulation of bivalent chromatin modifications that are lost along with pluripotency, suggesting a mechanism by which cancer cells reacquire properties that are characteristic of undifferentiated, multipotent cells. This bivalent epigenetic control of oncofetal gene expression in cancer cells may offer novel insights into the onset and progression of cancer and may provide specific and selective options for diagnosis as well as for therapeutic intervention.

High glucose impaired estrogen receptor alpha signaling via β-catenin in osteoblastic MC3T3-E1

Diabetic Mellitus is a risk factor for osteoporosis. It has been suggested that altered estrogen or estrogen receptor α/β (ERα/β) signaling may be involved in diabetic osteoporosis. The present study is to investigate the effects of high glucose on ERα/β signaling in osteoblastic MC3T3-E1 and how the altered signaling of ERα/β affect osteoblastic bone formation. ERα/β signaling was demonstrated as ERα/β protein expression (Western Blotting) and ER transcription activity (Luciferase Reporter assays). Proliferation (WSK-1 assaying), differentiation (ALP staining) and mineralization (Alizalard Red staining) of MC3T3-E1 were examined to evaluate bone formation function. It has been found that high glucose increased ERα/β expression dose-dependently and time-dependently, but high glucose (33mM) decreased ERα transcription activity. 17β-estradiol increased the ERα/β expression dose-dependently in normal medium, but decreased the ERα/β expression dose-dependently in medium with high glucose (33mM). High glucose decreased bone formation and also decreased the osteogenic effects of 17β-estradiol (10^-8M). High glucose decreased β-catenin expression dose-dependently and time-dependently. LiCl, an inhibitor of β-catenin degradation, decreased ERα expression but increased ERα transcription activity. When compared with high glucose treatment, LiCl (5mM) increased ALP activity and calcified nodes. Besides, high glucose also decreased the protein expression PI-3K, pAKT/AKT, GSK-3β. In conclusion, the present study suggested that high glucose may impair ERα transcription activity by inhibiting β-catenin signaling in osteoblastic MC3T3-E1, leading decreased bone formation ligand-dependently or ligand-independently.

Abnormally glycosylated MUC1 establishes a positive feedback circuit of inflammatory cytokines, mediated by NF-κB p65 and EzH2, in colitis-associated cancer

The abnormal hypoglycosylated form of the epithelial mucin MUC1 is over-expressed in chronic inflammation and on human adenocarcinomas, suggesting its potential role in inflammation-driven tumorigenesis. The presence of human MUC1 aggravates colonic inflammation and increases tumor initiation and progression in an in vivo AOM/DSS mouse model of colitis-associated cancer (CAC). High expression levels of pro-inflammatory cytokines, including TNF-α and IL-6, were found in MUC1+ inflamed colon tissues. Exogenous TNF-α promoted the transcriptional activity of MUC1 as well as over-expression of its hypoglycosylated form in intestinal epithelial cells (IECs). In turn, hypoglycosylated MUC1 in IECs associated with p65 and up-regulated the expression of NF-κB-target genes encoding pro-inflammatory cytokines. Intestinal chronic inflammation also increased the expression of histone methyltransferase Enhancer of Zeste protein-2 (EzH2) and its interaction with cytokine promoters. Consequently, EzH2 was a positive regulator of MUC1 and p65-mediated IL-6 and TNF-α gene expression, and this function was not dependent on its canonical histone H3K27 methyltransferase activity. Our findings provide a mechanistic basis for already known tumorigenic role of the hypoglycosylated MUC1 in CAC, involving a transcriptional positive feedback loop of pro-inflammatory cytokines.

Semi-Quantitative Mass Spectrometry in AML Cells Identifies New Non-Genomic Targets of the EZH2 Methyltransferase

Alterations to the gene encoding the EZH2 (KMT6A) methyltransferase, including both gain-of-function and loss-of-function, have been linked to a variety of haematological malignancies and solid tumours, suggesting a complex, context-dependent role of this methyltransferase. The successful implementation of molecularly targeted therapies against EZH2 requires a greater understanding of the potential mechanisms by which EZH2 contributes to cancer. One aspect of this effort is the mapping of EZH2 partner proteins and cellular targets. To this end we performed affinity-purification mass spectrometry in the FAB-M2 HL-60 acute myeloid leukaemia (AML) cell line before and after all-trans retinoic acid-induced differentiation. These studies identified new EZH2 interaction partners and potential non-histone substrates for EZH2-mediated methylation. Our results suggest that EZH2 is involved in the regulation of translation through interactions with a number of RNA binding proteins and by methylating key components of protein synthesis such as eEF1A1. Given that deregulated mRNA translation is a frequent feature of cancer and that eEF1A1 is highly expressed in many human tumours, these findings present new possibilities for the therapeutic targeting of EZH2 in AML.

[The biological complexity of Polycomb group proteins: the case of EZH2]

Polycomb Group proteins (PcG) are repressive epigenetic factors essential for development and involved in numerous cancer processes, yet their modes of action and recruitment to specific genomic loci are not fully understood. Recently, it has been shown that the PcG protein recruitment is a dynamic process, contrary to what was foreseen in the initial hierarchical model. In addition, EZH2, a key PcG protein, can be associated to transcribed genes, challenging the former function of PcG proteins as transcriptional repressors. Furthermore, the dual role of EZH2, which can act as an oncogene or a tumor suppressor depending on the cellular type, illustrates the functional complexity of PcG proteins.

Long noncoding RNA UCA1 induced by SP1 promotes cell proliferation via recruiting EZH2 and activating AKT pathway in gastric cancer

Long noncoding RNA UCA1 has emerged as a novel regulator in cancer initiation and progression of various cancers. However, function and underlying mechanism of UCA1 in the progression of gastric cancer (GC) remain unclear. In the present study, we report that UCA1 expressed highly in GC tissues and GC cells, which was partly induced by SP1. UCA1 promoted GC cell proliferation and G1/S transition in vitro and in vivo. Moreover, UCA1 exerted its function through interacting with EZH2, promoting direct interaction with cyclin D1 promoter to activate the translation of cyclin D1. Furthermore, AKT/GSK-3B/cyclin D1 axis was activated to upregulate cyclin D1 due to overexpression of UCA1. In addition, EZH2 and phosphorylated AKT induced by UCA1 could impact each other to form a positive feedback to promote cyclin D1 expression. This study demonstrated that UCA1 as a critical regulator involved in GC proliferation and cell cycle progression by promoting cyclin D1 expression, which indicates that it may be clinically a potential therapeutic target in GC.

EZH2 in Cancer Progression and Potential Application in Cancer Therapy: A Friend or Foe?

Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, catalyzes tri-methylation of histone H3 at Lys 27 (H3K27me3) to regulate gene expression through epigenetic machinery. EZH2 functions as a double-facet molecule in regulation of gene expression via repression or activation mechanisms, depending on the different cellular contexts. EZH2 interacts with both histone and non-histone proteins to modulate diverse physiological functions including cancer progression and malignancy. In this review article, we focused on the updated information regarding microRNAs (miRNAs) and long non coding RNAs (lncRNAs) in regulation of EZH2, the oncogenic and tumor suppressive roles of EZH2 in cancer progression and malignancy, as well as current pre-clinical and clinical trials of EZH2 inhibitors.

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

Multiple studies have documented that Enhancer of zeste homolog 2 (EZH2) could play a role in inflammation and a wide range of malignancies; however, the underlying mechanisms remain largely unaddressed. Microglial activation is a key process in the production and release of numerous pro-inflammatory mediators that play important roles in inflammation and neurodegeneration in the central nervous system (CNS). Therefore, our aim was to investigate whether inhibition of EZH2 with the selective small molecule inhibitor EPZ-6438 protects against neonatal microglial activation. First, in mouse primary microglial cells and a microglial cell line, we found that LPS can rapidly increase EZH2 mRNA level and we subsequently performed gene expression profiling and constructed networks in resting, EPZ-6438-treated, LPS-treated and LPS+EPZ-6438-treated primary microglial cells and a microglial cell line using transcriptome RNA sequencing and bioinformatics analyses. By examining the RNA sequencing, we identified EPZ-6438 target genes and co-regulated modules that were critical for inflammation. We also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and the transcription of key inflammatory mediators. Furthermore, we showed that EPZ-6438 controls important inflammatory gene targets by modulating interferon regulatory factor (IRF) 1, IRF8, and signal transducer and activator of transcription (STAT) 1 levels at their promoter sites. Our unprecedented findings demonstrate that pharmacological interventions built upon EZH2 inhibition by EPZ-6438 could be a useful therapeutic approach for the treatment of neuroinflammatory diseases associated with microglial activation.

Lkb1 inactivation drives lung cancer lineage switching governed by Polycomb Repressive Complex 2

Adenosquamous lung tumours, which are extremely poor prognosis, may result from cellular plasticity. Here, we demonstrate lineage switching of KRAS+ lung adenocarcinomas (ADC) to squamous cell carcinoma (SCC) through deletion of Lkb1 (Stk11) in autochthonous and transplant models. Chromatin analysis reveals loss of H3K27me3 and gain of H3K27ac and H3K4me3 at squamous lineage genes, including Sox2, ΔNp63 and Ngfr. SCC lesions have higher levels of the H3K27 methyltransferase EZH2 than the ADC lesions, but there is a clear lack of the essential Polycomb Repressive Complex 2 (PRC2) subunit EED in the SCC lesions. The pattern of high EZH2, but low H3K27me3 mark, is also prevalent in human lung SCC and SCC regions within ADSCC tumours. Using FACS-isolated populations, we demonstrate that bronchioalveolar stem cells and club cells are the likely cells-of-origin for SCC transitioned tumours. These findings shed light on the epigenetics and cellular origins of lineage-specific lung tumours.

The mechanisms that govern the transdifferentiation of lung adenocarcinomas (ADC) to squamous cell carcinoma (SCC) are not fully understood. Here, the authors show that EZH2 loss exacerbates the transdifferentiation of ADCs to SCCs as a result of chromatin changes that lead to expression of squamous differentiation genes.

The expression pattern of long non-coding RNA PVT1 in tumor tissues and in extracellular vesicles of colorectal cancer correlates with cancer progression

The plasmacytoma variant translocation 1 gene (PVT1) is a large non-coding locus at adjacent of c-Myc, and long non-coding RNA PVT1 is now recognized as a cancerous gene co-amplified with c-Myc in various cancers. But the expression and functional role of PVT1 in colorectal cancer are still unelucidated. In addition, all the reported long non-coding RNAs so far are discovered in either cells or tissues, but no research about long non-coding RNAs detection in extracellular vesicles has been reported yet. In the present study, we firstly investigated the expression of PVT1 in colorectal cancer specimens and its correlation with the expression of c-Myc and other related genes by real-time polymerase chain reaction. Then, we isolated the extracellular vesicles from colorectal cancer cells culturing medium by differential centrifugation and detected the PVT1 expression in extracellular vesicles by using real-time polymerase chain reaction. The PVT1 targeting siRNA was transfected into SW480 and SW620 cells, and 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and flow cytometry were used to evaluate the cell proliferation and apoptosis. The results showed that the PVT1 expression in tumor tissues was higher than that in normal tissues, which was significantly correlated with the expression of c-Myc and three c-Myc regulating genes FUBP1, EZH2, and NPM1 and also correlated with the expression of two other PVT1-associated transcript factors nuclear factor-κB and myocyte-specific enhancer factor 2A. Here, we reported for the first time that PVT1 as a long non-coding RNA was successfully detected in extracellular vesicles excluded from SW620 and SW480 cells, and the expression level of PVT1 was higher in extracellular vesicles from the more aggressive cell SW620 than from SW480. The results also showed that by down-regulating the PVT1 expression, the c-Myc expression was suppressed, the cell proliferation was inhibited, and cell apoptosis was increased. Taken together, these findings implicated that PVT1 may be a new oncogene co-amplified with c-Myc in colorectal cancer tissues and extracellular vesicles and functionally correlated with the proliferation and apoptosis of colorectal cancer cells.

The Histone Methyltransferase Ash1l is Required for Epidermal Homeostasis in Mice

Epidermal homeostasis under normal and healing conditions are critical for the physical and functional maintenance of the skin barrier. It requires a proper balance between keratinocyte proliferation and differentiation under genetic and epigenetic regulations. Here we show that mice carrying a hypomorphic mutation of the histone methyltransferase Ash1l [(absent, small, or homeotic)-like (Drosophila)] develop epidermal hyperplasia and impaired epidermal stratification upon aging. In adult mutants, loss of Ash1l leads to more proliferative keratinocytes in disturbed differentiation stages. After wounding, Ash1l mutation leads to delayed re-epithlialization but increased keratinocyte proliferation at the wound edge. Elevated c-Myc expression could be observed in both aged and wounded mutant tissues. Taken together, these observations revealed an important role of the epigenetic regulator Ash1l in epidermal homeostasis.

Hsp90 inhibition destabilizes Ezh2 protein in alloreactive T cells and reduces graft-versus-host disease in mice

Modulating T-cell alloreactivity has been a main strategy to reduce graft-versus-host disease (GVHD), a life-threatening complication after allogeneic hematopoietic stem-cell transplantation (HSCT). Genetic deletion of T-cell Ezh2, which catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3), inhibits GVHD. Therefore, reducing Ezh2-mediated H3K27me3 is thought to be essential for inhibiting GVHD. We tested this hypothesis in mouse GVHD models. Unexpectedly, administration of the Ezh2 inhibitor GSK126, which specifically decreases H3K27me3 without affecting Ezh2 protein, failed to prevent the disease. In contrast, destabilizing T-cell Ezh2 protein by inhibiting Hsp90 using its specific inhibitor AUY922 reduced GVHD in mice undergoing allogeneic HSCT. In vivo administration of AUY922 selectively induced apoptosis of activated T cells and decreased the production of effector cells producing interferon γ and tumor necrosis factor α, similar to genetic deletion of Ezh2. Introduction of Ezh2 into alloreactive T cells restored their expansion and production of effector cytokines upon AUY922 treatment, suggesting that impaired T-cell alloreactivity by inhibiting Hsp90 is achieved mainly through depleting Ezh2. Mechanistic analysis revealed that the enzymatic SET domain of Ezh2 directly interacted with Hsp90 to prevent Ezh2 from rapid degradation in activated T cells. Importantly, pharmacological inhibition of Hsp90 preserved antileukemia activity of donor T cells, leading to improved overall survival of recipient mice after allogeneic HSCT. Our findings identify the Ezh2-Hsp90 interaction as a previously unrecognized mechanism essential for T-cell responses and an effective target for controlling GVHD.

TRIM28 interacts with EZH2 and SWI/SNF to activate genes that promote mammosphere formation

Histone methyl transferase EZH2 (Enhancer of Zeste Homolog 2) is generally associated with H3K27 methylation and gene silencing, as a member of the polycomb repressor 2 (PRC2) complex. Immunoprecipitation and mass spectrometry of the EZH2-protein interactome in estrogen receptor positive, breast cancer-derived MCF7 cells revealed EZH2 interactions with subunits of chromatin remodeler SWI/SNF complex and TRIM28, which formed a complex with EZH2 distinct from PRC2. Unexpectedly, transcriptome profiling showed that EZH2 primarily activates, rather than represses, transcription in MCF7 cells and with TRIM28 co-regulates a set of genes associated with stem cell maintenance and poor survival of breast cancer patients. TRIM28 depletion repressed EZH2 recruitment to chromatin and expression of this gene set, in parallel with decreased CD44^hi/CD24^lo mammosphere formation. Mammosphere formation, inhibited by EZH2 depletion, was rescued by ectopic expression of EZH2 but not by TRIM28 expression or by EZH2 mutated at the region (pre-SET domain) of TRIM28 interaction. These results support PRC2-independent functions of EZH2 and TRIM28 in activation of gene expression that promotes mammary stem cell enrichment and maintenance.

Alpha7-nicotinic acetylcholine receptors involve the imidacloprid-induced inhibition of IgE-mediated rat and human mast cell activation

Although our recent study indicated that imidacloprid, a widely used neonicotinoid insecticide, inhibited IgE-mediated mast cell activation, the inhibition mechanism still remains unclear.

Proximal and distal regulation of the HYAL1 gene cluster by the estrogen receptor α in breast cancer cells

Chromosomal and genome abnormalities at the 3p21.3 locus are frequent events linked to epithelial cancers, including ovarian and breast cancers. Genes encoded in the 3p21.3 cluster include HYAL1, HYAL2 and HYAL3 members of hyaluronidases involved in the breakdown of hyaluronan, an abundant component of the vertebrate extracellular matrix. However, the transcriptional regulation of HYAL genes is poorly defined. Here, we identified the estrogen receptor ERα as a negative regulator of HYAL1 expression in breast cancer cells. Integrative data mining using METABRIC dataset revealed a significant inverse correlation between ERα and HYAL1 gene expression in human breast tumors. ChIP-Seq analysis identified several ERα binding sites within the 3p21.3 locus, supporting the role of estrogen as an upstream signal that diversely regulates the expression of 3p21.3 genes at both proximal and distal locations. Of these, HYAL1 was repressed by estrogen through ERα binding to a consensus estrogen response element (ERE) located in the proximal promoter of HYAL1 and flanked by an Sp1 binding site, required to achieve optimal estrogen repression. The repressive chromatin mark H3K27me3 was increased at the proximal HYAL1 ERE but not at other EREs contained in the cluster, providing a mechanism to selectively downregulate HYAL1. The HYAL1 repression was also specific to ERα and not to ERβ, whose expression did not correlate with HYAL1 in human breast tumors. This study identifies HYAL1 as an ERα target gene and provides a functional framework for the direct effect of estrogen on 3p21.3 genes in breast cancer cells.

A New Role for ERα: Silencing via DNA Methylation of Basal, Stem Cell, and EMT Genes

Resistance to hormonal therapies is a major clinical problem in the treatment of estrogen receptor α-positive (ERα⁺) breast cancers. Epigenetic marks, namely DNA methylation of cytosine at specific CpG sites (5mCpG), are frequently associated with ERα⁺ status in human breast cancers. Therefore, ERα may regulate gene expression in part via DNA methylation. This hypothesis was evaluated using a panel of breast cancer cell line models of antiestrogen resistance. Microarray gene expression profiling was used to identify genes normally silenced in ERα⁺ cells but derepressed upon exposure to the demethylating agent decitabine, derepressed upon long-term loss of ERα expression, and resuppressed by gain of ERα activity/expression. ERα-dependent DNA methylation targets (n = 39) were enriched for ERα-binding sites, basal-up/luminal-down markers, cancer stem cell, epithelial-mesenchymal transition, and inflammatory and tumor suppressor genes. Kaplan-Meier survival curve and Cox proportional hazards regression analyses indicated that these targets predicted poor distant metastasis-free survival among a large cohort of breast cancer patients. The basal breast cancer subtype markers LCN2 and IFI27 showed the greatest inverse relationship with ERα expression/activity and contain ERα-binding sites. Thus, genes that are methylated in an ERα-dependent manner may serve as predictive biomarkers in breast cancer.

IMPLICATIONS

ERα directs DNA methylation-mediated silencing of specific genes that have biomarker potential in breast cancer subtypes. Mol Cancer Res; 15(2); 152-64. ©2016 AACR.

Cardamonin reduces chemotherapy-enriched breast cancer stem-like cells in vitro and in vivo

The failure of cytotoxic chemotherapy in breast cancers has been closely associated with the presence of drug resistant cancer stem cells (CSCs). Thus, screening for small molecules that selectively inhibit growth of CSCs may offer great promise for cancer control, particularly in combination with chemotherapy. In this report, we provide the first demonstration that cardamonin, a small molecule, selectively inhibits breast CSCs that have been enriched by chemotherapeutic drugs. In addition, cardamonin also sufficiently prevents the enrichment of CSCs when simultaneously used with chemotherapeutic drugs. Specifically, cardamonin effectively abolishes chemotherapeutic drug-induced up-regulation of IL-6, IL-8 and MCP-1 and activation of NF-κB/IKBα and Stat3. Furthermore, in a xenograft mouse model, co-administration of cardamonin and the chemotherapeutic drug doxorubicin significantly retards tumor growth and simultaneously decreases CSC pools in vivo. Since cardamonin has been found in some herbs, this work suggests a potential new approach for the effective treatment of breast CSCs by administration of cardamonin either concurrent with or after chemotherapeutic drugs.

Non-Canonical EZH2 Transcriptionally Activates RelB in Triple Negative Breast Cancer

Enhancer of zeste homology 2 (EZH2) is the methyltransferase component of the polycomb repressive complex (PRC2) which represses gene transcription via histone H3 trimethylation at lysine 23 (H3K27me3). EZH2 activity has been linked with oncogenesis where it is thought to block expression of certain tumor suppressors. Relative to a role in cancer, EZH2 functions to promote self-renewal and has been shown to be important for the tumor-initiating cell (TIC) phenotype in breast cancer. Recently a non-canonical role for EZH2 has been identified where it promotes transcriptional activation of certain genes. Here we show that EZH2, through a methyltransferase-independent mechanism, promotes the transcriptional activation of the non-canonical NF-κB subunit RelB to drive self-renewal and the TIC phenotype of triple-negative breast cancer cells.

Nested quantitative PCR approach for urinary cell-free EZH2 mRNA and its potential clinical application in bladder cancer

EZH2 is overexpressed in bladder cancer (BC) and plays important roles in tumor development and progression. Recent studies show cell free (cf) RNAs released from cancer cells can reflect tissues changes and are stable and detectable in urine. Although conventional quantitative real-time PCR (qPCR) is highly sensitive, low abundances of urinary cf-RNAs usually result in false-negatives. Thus, this study develops a nested qPCR (nqPCR) approach to quantify cf-EZH2 mRNA in urine and further assess its clinical significance for BC. Forty urine samples were first selected to evaluate feasibility of nqPCR. Then, levels of urinary cf-EZH2 mRNA were detected using developed method in an independent cohort of subjects with 91 healthy, 81 cystitis, 169 nonmuscle invasive BC (NMIBC) and 103 muscle-invasive BC (MIBC). In cf-EZH2 mRNA detection, nqPCR method was significantly associated with qPCR, but it could detect more urine samples and increase detection limit three orders of magnitude. Based on nqPCR method, cf-EZH2 mRNA levels have been found to be increased in urine of NMIBC and MIBC patients (p < 0.001). Compared with cytology, cf-EZH2 mRNA showed higher diagnostic ability for MIBC (p < 0.001) while not for NMIBC (p > 0.05). Moreover, it also could distinguish MIBC from NMIBC, with AUC of 0.787. For MIBC patients, high expression of cf-EZH2 mRNA associated with advanced stage and was an independent predictor of reduced disease free survival or overall survival. In conclusion, detection of cf-EZH2 mRNA in urine by nqPCR is a sensitive and noninvasive approach and may be used for diagnosis and prognosis prediction of MIBC.

Epstein-Barr Virus Oncoprotein LMP1 Mediates Epigenetic Changes in Host Gene Expression through PARP1

The latent infection of Epstein-Barr virus (EBV) is associated with 1% of human cancer incidence. Poly(ADP-ribosyl)ation (PARylation) is a posttranslational modification catalyzed by poly(ADP-ribose) polymerases (PARPs) that mediate EBV replication during latency. In this study, we detail the mechanisms that drive cellular PARylation during latent EBV infection and the effects of PARylation on host gene expression and cellular function. EBV-infected B cells had higher PAR levels than EBV-negative B cells. Moreover, cellular PAR levels were up to 2-fold greater in type III than type I latently infected EBV B cells. We identified a positive association between expression of the EBV genome-encoded latency membrane protein 1 (LMP1) and PAR levels that was dependent upon PARP1. PARP1 regulates gene expression by numerous mechanisms, including modifying chromatin structure and altering the function of chromatin-modifying enzymes. Since LMP1 is essential in establishing EBV latency and promoting tumorigenesis, we explored the model that disruption in cellular PARylation, driven by LMP1 expression, subsequently promotes epigenetic alterations to elicit changes in host gene expression. PARP1 inhibition resulted in the accumulation of the repressive histone mark H3K27me3 at a subset of LMP1-regulated genes. Inhibition of PARP1, or abrogation of PARP1 expression, also suppressed the expression of LMP1-activated genes and LMP1-mediated cellular transformation, demonstrating an essential role for PARP1 activity in LMP1-induced gene expression and cellular transformation associated with LMP1. In summary, we identified a novel mechanism by which LMP1 drives expression of host tumor-promoting genes by blocking generation of the inhibitory histone modification H3K27me3 through PARP1 activation.

IMPORTANCE

EBV is causally linked to several malignancies and is responsible for 1% of cancer incidence worldwide. The EBV-encoded protein LMP1 is essential for promoting viral tumorigenesis by aberrant activation of several well-known intracellular signaling pathways. We have identified and defined an additional novel molecular mechanism by which LMP1 regulates the expression of tumor-promoting host genes. We found that LMP1 activates the cellular protein PARP1, leading to a decrease in a repressive histone modification, accompanied by induction in expression of multiple cancer-related genes. PARP1 inhibition or depletion led to a decrease in LMP1-induced cellular transformation. Therefore, targeting PARP1 activity may be an effective treatment for EBV-associated malignancies.

MicroRNA-506 suppresses tumor proliferation and metastasis in colon cancer by directly targeting the oncogene EZH2

Increasing evidence reveals that aberrant expression of microRNA contributes to the development and progression of colon cancer, but the roles of microRNA-506 (miR-506) in colon cancer remain elusive. Here, we demonstrated that miR-506 was down-regulated in colon cancer tissue and cells and that miR-506 expression was inversely correlated with EZH2 expression, tumor size, lymph node invasion, TNM stage and metastasis. A high level of miR-506 identified patients with a favorable prognosis. In vitro and in vivo experiments confirmed that miR-506 inhibits the proliferation and metastasis of colon cancer, and a luciferase reporter assay confirmed that EZH2 is a direct and functional target of miR-506 via the 3′UTR of EZH2. The restoration of EZH2 expression partially reversed the proliferation and invasion of miR-506-overexpressing colon cancer cells. Moreover, we confirmed that the miR-506-EZH2 axis inhibits proliferation and metastasis by activating/suppressing specific downstream tumor-associated genes and the Wnt/β-catenin signaling pathway. Taking together, our study sheds light on the role of miR-506 as a suppressor for tumor growth and metastasis and raises the intriguing possibility that miR-506 may serve as a new potential marker for monitoring and treating colon cancer.

The Antitumor Effect of Metformin Is Mediated by miR-26a in Breast Cancer

Metformin, a drug approved for diabetes type II treatment, has been associated with a reduction in the incidence of breast cancer and metastasis and increased survival in diabetic breast cancer patients. High levels of miR-26a expression have been proposed as one of the possible mechanisms for this effect; likewise, this miRNA has also been associated with survival/apoptosis processes in breast cancer. Our aim was to evaluate if miR-26a and some of its targets could mediate the effect of metformin in breast cancer. The viability of MDA-MB-231, MDA-MB-468, and MCF-7 breast cancer cell lines was evaluated with an MTT assay after ectopic overexpression and/or downregulation of miR-26a. Similarly, the expression levels of the miR-26a targets CASP3, CCNE2, ABL2, APAF1, XIAP, BCL-2, PTEN, p53, E2F3, CDC25A, BCL2L1, MCL-1, EZH2, and MTDH were assessed by quantitative polymerase chain reaction (PCR). The effect of metformin treatment on breast cancer cell viability and miR-26a, BCL-2, PTEN, MCL-1, EZH2, and MTDH modulation were evaluated. Wound healing experiments were performed to analyze the effect of miR-26a and metformin treatment on cell migration. MiR-26a overexpression resulted in a reduction in cell viability that was partially recovered by inhibiting it. E2F3, MCL-1, EZH2, MTDH, and PTEN were downregulated by miR-26a and the PTEN (phosphatase and tensin homolog) protein was also reduced after miR-26a overexpression. Metformin treatment reduced breast cancer cell viability, increased miR-26a expression, and led to a reduction in BCL-2, EZH2, and PTEN expression. miR-26a inhibition partly prevents the metformin viability effect and the PTEN and EZH2 expression reduction. Our results indicate that metformin effectively reduces breast cancer cell viability and suggests that the effects of the drug are mediated by an increase in miR-26a expression and a reduction of its targets, PTEN and EHZ2 Thus, the use of metformin in breast cancer treatment constitutes a promising potential breast cancer therapy.

Integrating Epigenomic Elements and GWASs Identifies BDNF Gene Affecting Bone Mineral Density and Osteoporotic Fracture Risk

To identify susceptibility genes for osteoporosis, we conducted an integrative analysis that combined epigenomic elements and previous genome-wide association studies (GWASs) data, followed by validation at population and functional levels, which could identify common regulatory elements and predict new susceptibility genes that are biologically meaningful to osteoporosis. By this approach, we found a set of distinct epigenomic elements significantly enriched or depleted in the promoters of osteoporosis-associated genes, including 4 transcription factor binding sites, 27 histone marks, and 21 chromatin states segmentation types. Using these epigenomic marks, we performed reverse prediction analysis to prioritize the discovery of new candidate genes. Functional enrichment analysis of all the prioritized genes revealed several key osteoporosis related pathways, including Wnt signaling. Genes with high priority were further subjected to validation using available GWASs datasets. Three genes were significantly associated with spine bone mineral density, including BDNF, PDE4D, and SATB2, which all closely related to bone metabolism. The most significant gene BDNF was also associated with osteoporotic fractures. RNA interference revealed that BDNF knockdown can suppress osteoblast differentiation. Our results demonstrated that epigenomic data could be used to indicate common epigenomic marks to discover additional loci with biological functions for osteoporosis.

EZH2 phosphorylation by JAK3 mediates a switch to noncanonical function in natural killer/T-cell lymphoma

The best-understood mechanism by which EZH2 exerts its oncogenic function is through polycomb repressive complex 2 (PRC2)-mediated gene repression, which requires its histone methyltransferase activity. However, small-molecule inhibitors of EZH2 that selectively target its enzymatic activity turn out to be potent only for lymphoma cells with EZH2-activating mutation. Intriguingly, recent discoveries, including ours, have placed EZH2 into the category of transcriptional coactivators and thus raised the possibility of noncanonical signaling pathways. However, it remains unclear how EZH2 switches to this catalytic independent function. In the current study, using natural killer/T-cell lymphoma (NKTL) as a disease model, we found that phosphorylation of EZH2 by JAK3 promotes the dissociation of the PRC2 complex leading to decreased global H3K27me3 levels, while it switches EZH2 to a transcriptional activator, conferring higher proliferative capacity of the affected cells. Gene expression data analysis also suggests that the noncanonical function of EZH2 as a transcriptional activator upregulates a set of genes involved in DNA replication, cell cycle, biosynthesis, stemness, and invasiveness. Consistently, JAK3 inhibitor was able to significantly reduce the growth of NKTL cells, in an EZH2 phosphorylation-dependent manner, whereas various compounds recently developed to inhibit EZH2 methyltransferase activity have no such effect. Thus, pharmacological inhibition of JAK3 activity may provide a promising treatment option for NKTL through the novel mechanism of suppressing noncanonical EZH2 activity.

Role of EZH2 histone methyltrasferase in melanoma progression and metastasis

There is accumulating evidence that the histone methyltransferase enhancer of zeste homolog 2 (EZH2), the main component of the polycomb-repressive complex 2 (PRC2), is involved in melanoma progression and metastasis. Novel drugs that target and reverse such epigenetic changes may find a way into the management of patients with advanced melanoma. We provide a comprehensive up-to-date review of the role and biology of EZH2 on gene transcription, senescence/apoptosis, melanoma microenvironment, melanocyte stem cells, the immune system, and micro RNA. Furthermore, we discuss EZH2 inhibitors as potential anti-cancer therapy.

Fuse-binding protein 1 is a target of the EZH2 inhibitor GSK343, in osteosarcoma cells

Osteosarcoma is the primary cancer of leaf tissue and is regarded as a differentiation disease caused by genetic and epigenetic changes which interrupt the osteoblast differentiation from mesenchymal stem cells. Because of its high malignancy degree and rapid development, the morbidity and mortality are high. The enhancer of zeste homolog 2 (EZH2) is a catalytic subunit of polycomb repressive complex 2 (PRC2) and has been demonstrated to be involved in a variety of biological processes, such as cell proliferation and program cell death. EZH2 impairs gene expression by catalyzing the tri-methylation of histone H3 lysine 27 (H3K27me3) which controls gene transcription epigenetically. It is reported that EZH2 expression is higher in osteosarcoma than in osteoblastoma and the highest expression of EZH2 is found in osteosarcoma with metastasis. In the past few years, several potent inhibitors of EZH2 have been discovered, and GSK343 is one of them. In this study, we found that GSK343 inhibited osteosarcoma cell viability, restrained cell cycle transition and promoted programmed cell death. GSK343 not only inhibited the expression of EZH2 and its target, c-Myc and H3K27me3, but it also inhibited fuse binding protein 1 (FBP1) expression, another c-Myc regulator. Furthermore, we found that FBP1 physically interacts with EZH2. Based on these results, we believe that GSK343 is a potential molecule for osteosarcoma clinical treatment. Other than the inhibition on EZH2-c-Myc signal pathway, we postulate that the inhibition on FBP1-c-Myc signal pathway is another potential underlying mechanism with which GSK343 inhibits osteosarcoma cell viability.