Comprehensive evaluation of the role of EZH2 in the growth, invasion, and aggression of a panel of prostate cancer cell lines

First-in-Class Dual EZH2-HSP90 Inhibitor Eliciting Striking Antiglioblastoma Activity In Vitro and In Vivo

Structural analysis of tazemetostat, an FDA-approved EZH2 inhibitor, led us to pinpoint a suitable site for appendage with a pharmacophoric fragment of second-generation HSP90 inhibitors. Resultantly, a magnificent dual EZH2/HSP90 inhibitor was pinpointed that exerted striking cell growth inhibitory efficacy against TMZ-resistant Glioblastoma (GBM) cell lines. Exhaustive explorations of chemical probe 7 led to several revelations such as (i) compound 7 increased apoptosis/necrosis-related gene expression, whereas decreased M phase/kinetochore/spindle-related gene expression as well as CENPs protein expression in Pt3R cells; (ii) dual inhibitor 7 induced cell cycle arrest at the M phase; (iii) compound 7 suppressed reactive oxygen species (ROS) catabolism pathway, causing the death of TMZ-resistant GBM cells; and (iv) compound 7 elicited substantial in vivo anti-GBM efficacy in experimental mice xenografted with TMZ-resistant Pt3R cells. Collectively, the study results confirm the potential of dual EZH2-HSP90 inhibitor 7 as a tractable anti-GBM agent.

Tissue-Based Diagnostic Biomarkers of Aggressive Variant Prostate Cancer: A Narrative Review

Prostate cancer (PC) is a common malignancy among elderly men, characterized by great heterogeneity in its clinical course, ranging from an indolent to a highly aggressive disease. The aggressive variant of prostate cancer (AVPC) clinically shows an atypical pattern of disease progression, similar to that of small cell PC (SCPC), and also shares the chemo-responsiveness of SCPC. The term AVPC does not describe a specific histologic subtype of PC but rather the group of tumors that, irrespective of morphology, show an aggressive clinical course, dictated by androgen receptor (AR) indifference. AR indifference represents an adaptive response to androgen deprivation therapy (ADT), driven by epithelial plasticity, an inherent ability of tumor cells to adapt to their environment by changing their phenotypic characteristics in a bi-directional way. The molecular profile of AVPC entails combined alterations in the tumor suppressor genes retinoblastoma protein 1 (RB1), tumor protein 53 (TP53), and phosphatase and tensin homolog (PTEN). The understanding of the biologic heterogeneity of castration-resistant PC (CRPC) and the need to identify the subset of patients that would potentially benefit from specific therapies necessitate the development of prognostic and predictive biomarkers. This review aims to discuss the possible pathophysiologic mechanisms of AVPC development and the potential use of emerging tissue-based biomarkers in clinical practice.

Polycomb repressor complex: Its function in human cancer and therapeutic target strategy

The Polycomb Repressor Complex (PRC) plays a pivotal role in gene regulation during development and disease, with dysregulation contributing significantly to various human cancers. The intricate interplay between PRC and cellular signaling pathways sheds light on cancer complexity. PRC presents promising therapeutic opportunities, with inhibitors undergoing rigorous evaluation in preclinical and clinical studies. In this review, we emphasize the critical role of PRC complex in gene regulation, particularly PcG proteins mediated chromatin compaction through phase separation. We also highlight the pathological implications of PRC complex dysregulation in various tumors, elucidating underlying mechanisms driving cancer progression. The burgeoning field of therapeutic strategies targeting PRC complexes, notably EZH2 inhibitors, has advanced significantly. However, we explore the need for combination therapies to enhance PRC targeted treatments efficacy, providing a glimpse into the future of cancer therapeutics.

Simultaneous administration of EZH2 and BET inhibitors inhibits proliferation and clonogenic ability of metastatic prostate cancer cells

Androgen deprivation therapy (ADT) is a common treatment for recurrent prostate cancer (PC). However, after a certain period of responsiveness, ADT resistance occurs virtually in all patients and the disease progresses to lethal metastatic castration-resistant prostate cancer (mCRPC). Aberrant expression and function of the epigenetic modifiers EZH2 and BET over activates c-myc, an oncogenic transcription factor critically contributing to mCRPC. In the present work, we tested, for the first time, the combination of an EZH2 inhibitor with a BET inhibitor in metastatic PC cells. The combination outperformed single drugs in inhibiting cell viability, cell proliferation and clonogenic ability, and concomitantly reduced both c-myc and NF-kB expression. Although these promising results will warrant further in vivo validation, they represent the first step to establishing the rationale that the proposed combination might be suitable for mCRPC treatment, by exploiting molecular targets different from androgen receptor.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

miR-26a-5p restoration via EZH2 silencing blocks the IL-6/STAT3 axis to repress the growth of prostate cancer

BACKGROUND

Interleukin-6 (IL-6) is involved in the activation of several oncogenic pathways in prostate cancer. However, its upstream trans-signaling pathway remains largely unknown. This work proposes a mechanistic explanation of IL-6's upstream effectors in prostate carcinogenesis.

RESEARCH DESIGN & METHODS

Samples were harvested to validate the expression of EZH2, miR-26a-5p, and IL-6. Moreover, the protein and its phosphorylation of STAT3 (signal transducer and transcription activator 3) were assessed in prostate cancer cells. We explored the effects of these effectors on malignant phenotypes in vitro and tumor growth in vivo using functional assays. Bioinformatics analysis, dual-luciferase reporter gene assays, and chromatin immunoprecipitation (ChIP) assays were used to determine their binding relationships.

RESULTS

Overexpression of EZH2 and IL-6, and under expression of miR-26a-5p was observed in prostate cancer. Silencing IL-6 repressed STAT3 to suppress the malignant phenotypes of prostate cancer cells. Mechanistically, EZH2 inhibited miR-26a-5p expression by promoting H3K27 histone methylation, and miR-26a-5p restricted the malignant phenotypes of prostate cancer by targeting IL-6. Ectopic EZH2 expression reduced xenograft growth by inhibiting miR-26a-5p and activating the IL-6/STAT3 axis.

CONCLUSION

EZH2 May potentially be involved in regulating its expression by recruiting H3K27me3 to the miR-26a-5p promoter region, which could further impact the IL6/STAT3 pathway.

Addressing the need for more therapeutic options in neuroendocrine prostate cancer

INTRODUCTION

Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer frequently seen after prolonged treatment of castration resistant prostate cancer (CRPC). NEPC has become increasingly prevalent over the last 20 years, with a poor prognosis caused by a late diagnosis and limited treatment options. Recent advances in PET/CT imaging and targeted radioimmunotherapy are promising, but more research into additional treatment options is needed.

AREAS COVERED

The aim of this review is to analyze the current imaging and treatment options for NEPC, and to highlight future potential treatment strategies. A Pubmed search for 'Neuroendocrine Prostate Cancer' was performed and relevant articles were reviewed.

EXPERT OPINION

The recent FDA approval and success of 177 PSMA Lutetium in CRPC is promising, as 177 Lutetium could potentially be paired with a NEPC specific biomarker for targeted therapy. Recent laboratory studies pairing DLL3, which is overexpressed in NEPC, with 177 Lutetium and new PET agents have showed good efficacy in identifying and treating NEPC. The success of future development of NEPC therapies may depend on the availability of 177 Lutetium, as current supplies are limited. Further research into additional imaging and treatment options for NEPC is warranted.

Clinical considerations for the management of androgen indifferent prostate cancer

BACKGROUND

Many systemic therapies for advanced prostate cancer work by disrupting androgen receptor signaling. Androgen indifferent prostate cancer (AIPC) variants, including aggressive variant prostate cancer (AVPC), neuroendocrine prostate cancer (NEPC), and double-negative prostate cancer (DNPC), are increasingly common and often overlapping resistance phenotypes following treatment with androgen receptor signaling inhibitors in men with metastatic castration-resistant prostate cancer and are associated with poor outcomes. Understanding the underlying biology and identifying effective therapies for AIPC is paramount for improving survival for men with prostate cancer.

METHODS

In this review, we summarize the current knowledge on AIPC variants, including our current understanding of the clinical, morphologic, and molecular features as well as current therapeutic approaches. We also explore emerging therapies and biomarkers aimed at improving outcomes for men with AIPC.

RESULTS AND CONCLUSIONS

Establishing consensus definitions, developing novel biomarkers for early and accurate detection, further characterization of molecular drivers of each phenotype, and developing effective therapies will be critical to improving outcomes for men with AIPC. Significant progress has been made toward defining the clinical and molecular characteristics of AVPC, NEPC, and DNPC. Novel diagnostic approaches, including cell-free DNA, circulating tumor cells, and molecular imaging are promising tools for detecting AIPC in clinical practice. Building on previous treatment advances, several clinical trials are underway evaluating novel therapeutic approaches in patients with AIPC informed by an understanding of variant-specific biology. In this review, we discuss how these recent and ongoing studies will help to improve diagnosis, prognosis, and therapy for men with AIPC.

Loss and revival of androgen receptor signaling in advanced prostate cancer

Targeting the androgen receptor (AR) signaling axis has been, over decades, the mainstay of prostate cancer therapy. More potent inhibitors of androgen synthesis and antiandrogens have emerged and have been successfully implemented in clinical practice. That said, the stronger inhibition of the AR signaling axis has led in recent years to an increase of prostate cancers that de-differentiate into AR-negative disease. Unfortunately, this process is intimately linked with a poor prognosis. Here, we review the molecular mechanisms that enable cancer cells to switch from an AR-positive to an AR-negative disease and efforts to prevent/revert this process and thereby maintain/restore AR-dependence.

Molecular tracing of prostate cancer lethality

Prostate cancer is diagnosed mostly in men over the age of 50 years, and has favorable 5-year survival rates due to early cancer detection and availability of curative surgical management. However, progression to metastasis and emergence of therapeutic resistance are responsible for the majority of prostate cancer mortalities. Recent advancement in sequencing technologies and computational capabilities have improved the ability to organize and analyze large data, thus enabling the identification of novel biomarkers for survival, metastatic progression and patient prognosis. Large-scale sequencing studies have also uncovered genetic and epigenetic signatures associated with prostate cancer molecular subtypes, supporting the development of personalized targeted-therapies. However, the current state of mainstream prostate cancer management does not take full advantage of the personalized diagnostic and treatment modalities available. This review focuses on interrogating biomarkers of prostate cancer progression, including gene signatures that correspond to the acquisition of tumor lethality and those of predictive and prognostic value in progression to advanced disease, and suggest how we can use our knowledge of biomarkers and molecular subtypes to improve patient treatment and survival outcomes.

The Promise for Histone Methyltransferase Inhibitors for Epigenetic Therapy in Clinical Oncology: A Narrative Review

Epigenetic processes are essential for normal development and the maintenance of tissue-specific gene expression in mammals. Changes in gene expression and malignant cellular transformation can result from disruption of epigenetic mechanisms, and global disruption in the epigenetic landscape is a key feature of cancer. The study of epigenetics in cancer has revealed that human cancer cells harbor both genetic alterations and epigenetic abnormalities that interplay at all stages of cancer development. Unlike genetic mutations, epigenetic aberrations are potentially reversible through epigenetic therapy, providing a therapeutically relevant treatment option. Histone methyltransferase inhibitors are emerging as an epigenetic therapy approach with great promise in the field of clinical oncology. The recent accelerated approval of the enhancer of zeste homolog 2 (EZH2; also known as histone-lysine N-methyltransferase EZH2) inhibitor tazemetostat for metastatic or locally advanced epithelioid sarcoma marks the first approval of such a compound for the treatment of cancer. Many other histone methyltransferase inhibitors are currently in development, some of which are being tested in clinical studies. This review focuses on histone methyltransferase inhibitors, highlighting their potential in the treatment of cancer. We also discuss the role for such epigenetic drugs in overcoming epigenetically driven drug resistance mechanisms, and their value in combination with other therapeutic approaches such as immunotherapy.

Design, Synthesis, and Pharmacological Evaluation of Second Generation EZH2 Inhibitors with Long Residence Time

Histone methyltransferase EZH2, which is the catalytic subunit of the PRC2 complex, catalyzes the methylation of histone H3K27-a transcriptionally repressive post-translational modification (PTM). EZH2 is commonly mutated in hematologic malignancies and frequently overexpressed in solid tumors, where its expression level often correlates with poor prognosis. First generation EZH2 inhibitors are beginning to show clinical benefit, and we believe that a second generation EZH2 inhibitor could further build upon this foundation to fully realize the therapeutic potential of EZH2 inhibition. During our medicinal chemistry campaign, we identified 4-thiomethyl pyridone as a key modification that led to significantly increased potency and prolonged residence time. Leveraging this finding, we optimized a series of EZH2 inhibitors, with enhanced antitumor activity and improved physiochemical properties, which have the potential to expand the clinical use of EZH2 inhibition.

Targeting of EZH2 inhibits epithelial‑mesenchymal transition in head and neck squamous cell carcinoma via regulating the STAT3/VEGFR2 axis

Tumor metastasis regulated by epithelial‑mesenchymal transition (EMT) plays a significant role in the development of human cancers, whereas the molecular mechanisms of this process in head and neck squamous cell carcinoma (HNSCC) remain elusive. In this study, we found that inhibition of enhancer of zeste homolog 2 (EZH2) resulted in suppressed EMT in HNSCC in vitro and in vivo. We reported that signal transducer and activator of transcription factor 3 (STAT3)/vascular endothelial growth factor receptor 2 (VEGFR2) axis served as the downstream signaling of EZH2 and mediated EMT in HNSCC. EZH2 inhibition downregulated the expression of key molecules of the STAT3/VEGFR2 axis and EMT‑related markers, while the expression of E‑cadherin was upregulated in HNSCC cells. Targeting the EZH2/STAT3/VEGFR2 axis significantly reduced motility of HNSCC cells. Furthermore, EZH2 knockdown reduced the growth of xenograft HNSCC tumors via inhibiting the EZH2/STAT3/VEGFR2 axis. In conclusion, we proposed that EZH2 regulates EMT and tumor invasion and metastasis in HNSCC by governing the STAT3/VEGFR2 axis. These findings provide a rationale for developing novel strategies to treat invasive and metastatic HNSCC via targeting the EZH2/STAT3/VEGFR2 pathway.

Clinical significance of USP7 and EZH2 in predicting prognosis of laryngeal squamous cell carcinoma and their possible functional mechanism

BACKGROUND

Laryngeal squamous cell carcinoma (LSCC) is one of the most prevalent cancer types in the world. The ubiquitin specific protease 7 (USP7), a kind of deubiquitylating enzyme, has been reported to play multifaceted roles in different tumor types. EZH2 has been found to be highly expressed in various malignantcells and high expression of EZH2 is closely related to tumor growth infiltration, lymph node involvement, clinical stage, and poor prognosis. The aim of this study was to investigate the expression and function of USP7 and EZH2 in LSCC.

CASE PRESENTATION

Immunohistochemical staining and histochemical staining were performed to explore the expression of USP7 and EZH2 in both LSCC tissues and adjacent normal laryngeal tissues. Chi-square test, univariate analysis, and multivariate analysis were conducted to statistically evaluate the clinical significance of USP7 and EZH2.

CONCLUSIONS

USP7and EZH2 affects LSCC evolution; USP7 and EZH2 were upregulated in LSCC tissues, which can serve as independent prognostic predictors, and potential therapeutic targets for LSCC.

MicroRNAs Overcome Cell Fate Barrier by Reducing EZH2-Controlled REST Stability during Neuronal Conversion of Human Adult Fibroblasts

The ability to convert human somatic cells efficiently to neurons facilitates the utility of patient-derived neurons for studying neurological disorders. As such, ectopic expression of neuronal microRNAs (miRNAs), miR-9/9^∗ and miR-124 (miR-9/9^∗-124) in adult human fibroblasts has been found to evoke extensive reconfigurations of the chromatin and direct the fate conversion to neurons. However, how miR-9/9^∗-124 break the cell fate barrier to activate the neuronal program remains to be defined. Here, we identified an anti-neurogenic function of EZH2 in fibroblasts that acts outside its role as a subunit of Polycomb Repressive Complex 2 to directly methylate and stabilize REST, a transcriptional repressor of neuronal genes. During neuronal conversion, miR-9/9^∗-124 induced the repression of the EZH2-REST axis by downregulating USP14, accounting for the opening of chromatin regions harboring REST binding sites. Our findings underscore the interplay between miRNAs and protein stability cascade underlying the activation of neuronal program.

Overexpression of EZH2 is associated with the poor prognosis in osteosarcoma and function analysis indicates a therapeutic potential

Osteosarcoma is a primary malignant bone tumor that has a poor prognosis due to local recurrence, metastasis, and chemotherapy resistance. Therefore, there is an urgent need to develop novel potential therapeutic targets for osteosarcoma. Enhancer of zeste homologue 2 (EZH2) is a member of the polycomb group of proteins, which has important functions in epigenetic silencing and cell cycle regulation. Overexpression of EZH2 has been found in several malignancies, however, its expression and the role of EZH2 in osteosarcoma is largely unknown. In this study, we examined EZH2 expression by immunohistochemistry in a large series of osteosarcoma tissues in association with tumor characteristics and patient outcomes. EZH2 expression was also analyzed in a microarray dataset of osteosarcoma. Results showed that higher expression of EZH2 was significantly associated with more aggressive tumor behavior and poor patient outcomes of osteosarcoma. We subsequently investigated the functional and therapeutic relevance of EZH2 as a target in osteosarcoma. Immunohistochemical analysis indicated that EZH2 expression was significantly associated with more aggressive tumor behavior and poorer patient outcomes of osteosarcoma. EZH2 silencing by siRNA inhibited osteosarcoma cell growth, proliferation, migration, and invasion. Moreover, suppression of EZH2 attenuated cancer stem cell functions. Similar results were observed in osteosarcoma cells treated with EZH2 specific inhibitor 3-deazaneplanocin A (DZNep), which exhausted cellular levels of EZH2. These results suggest that EZH2 is critical for the growth and metastasis of osteosarcoma, and an epigenetic therapy that pharmacologically targets EZH2 via specific inhibitors may constitute a novel approach to the treatment of osteosarcoma.

Site-Specific Fucosylation Analysis Identifying Glycoproteins Associated with Aggressive Prostate Cancer Cell Lines Using Tandem Affinity Enrichments of Intact Glycopeptides Followed by Mass Spectrometry

Fucosylation (Fuc) of glycoproteins plays an important role in regulating protein function and has been associated with the development of several cancer types including prostate cancer (Pca). Therefore, the research of Fuc glycoproteins has attracted increasing attention recently in the analytical field. Herein, a strategy based on lectin affinity enrichments of intact glycopeptides followed by mass spectrometry has been established to evaluate the specificities of various Fuc-binding lectins for glycosite-specific Fuc analysis of nonaggressive (NAG) and aggressive (AG) Pca cell lines. The enrichment specificities of Fuc glycopeptides using lectins (LCA, PSA, AAL, LTL, UEA I, and AOL) and MAX extraction cartridges alone, or in tandem, were evaluated. Our results showed that the use of lectin enrichment significantly increased the ratio of fucosylated glycopeptides to total glycopeptides compared to MAX enrichment. Furthermore, tandem use of lectin followed by MAX increased the number of identifications of Fuc glycopeptides compared to using lectin enrichment alone. LCA, PSA, and AOL showed stronger binding capacity than AAL, LTL, and UEA I. Also, LCA and PSA bound specifically to core Fuc, whereas AOL, AAL, and UEA I showed binding to both core Fuc and branch Fuc. The optimized enrichment method with tandem enrichment of LCA followed by MAX (LCA-MAX) was then applied to examine the Fuc glycoproteomes in two NAG and two AG Pca cell lines. In total, 973 intact Fuc glycopeptides were identified and quantified from 252 Fuc proteins by using the tandem-mass-tags (TMT) labeling and nanoliquid chromatography-mass spectrometry (nanoLC-MS/MS) analysis. Further data analysis revealed that 51 Fuc glycopeptides were overexpressed more than 2-fold in AG cell lines compared to NAG cells. The analysis of protein core fucosylation has great potential for aiding our understanding of invasive activity of AG Pca and may lead to the development of diagnostic approaches for AG Pca.

LncRNA-ANCR down-regulation suppresses invasion and migration of colorectal cancer cells by regulating EZH2 expression

Our study aimed to explore the effects of long noncoding RNA (lncRNA)-ANCR on the invasion and migration of colorectal cancer (CRC) cells by regulating enhancer of zeste homolog 2 (EZH2) expression. CRC tissues and adjacent normal tissues were collected and CRC SW620 cells line and normal human intestinal epithelial cells (HIECs) were incubated. CRC SW620 cells line was transfected with ANCR-siRNA. The expressions of ANCR and EZH2 mRNA were measured by real-time quantitative polymerase chain reaction (RT-qPCR). EZH2 and trimethylation of H3K27 (H3K27me3) protein expressions were detected using Western blotting. The relationship between ANCR and EZH2 was determined through RNA pull-down and co-immunoprecipitation (co-IP) assays. Cell invasion and migration were determined by Trans-well and cell scratch assays. ANCR, EZH2 and H3K27me3 expressions were up-regulated in CRC tissues and SW620 cells (all P < 0.05). After transfected with ANCR-siRNA, SW620 cells showed decreased ANCR expression and EZH2 mRNA and protein expressions (all P < 0.05). According to the results of RNA pull-down and co-IP assays, ANCR could specifically bind to EZH2. The results of Trans-well and cell scratch tests showed that when ANCR expression was decreased, the invasion and migration abilities of SW620 cells significantly declined (both P < 0.05). In conclusion, these results suggest that lncRNA-ANCR could influence the invasion and migration of CRC cells by specifically binding to EZH2.

Inhibition of EZH2 by chemo- and radiotherapy agents and small molecule inhibitors induces cell death in castration-resistant prostate cancer

Androgen deprivation therapy is the mainstay of treatment of advanced prostate cancer (PCa). However, a significant portion of patients experience disease relapse and tumors ultimately evolve into castration resistant prostate cancer (CRPC), for which there is no cure in the clinic. The Polycomb protein enhancer of zeste homolog 2 (EZH2) is frequently overexpressed in CRPC. It is unclear whether EZH2 can be a therapeutic target in CRPC. Here, we demonstrated that chemo- and radiotherapy agents such as camptothecin (CPT) and γ irradiation decrease EZH2 expression in various PCa cell lines. We provided evidence that functional p53 and RB proteins are required for CPT- and irradiation-induced downregulation of EZH2 in CRPC cells. We demonstrated that EZH2-specific small molecule inhibitors mitigate CRPC cell growth. We further showed that the EZH2 inhibitor GSK126 inhibits both Polycomb-dependent and -independent functions of EZH2 in PCa cells. Importantly, we found that inhibition of EZH2 by genetic and pharmacological means sensitizes CRPC cells to CPT-induced apoptotic death and growth inhibition in culture and in mice. Our data suggest that concomitant administration of small molecule inhibitors of EZH2 may significantly increase the anti-tumor efficacy of conventional chemo- and radiotherapies in CRPC.

Targeting EZH2 regulates tumor growth and apoptosis through modulating mitochondria dependent cell-death pathway in HNSCC

EZH2 is a negative prognostic factor and is overexpressed or activated in most human cancers including head and neck squamous cell carcinoma (HNSCC). Analysis of The Cancer Genome Atlas (TCGA) HNSCC data indicated that EZH2 over-expression was associated with high tumor grade and conferred poor prognosis. EZH2 inhibition triggered cell apoptosis, cell cycle arrest and decreased cell growth in vitro. MICU1 (mitochondrial calcium uptake1) was shown to be down regulated when EZH2 expression was inhibited in HNSCC. When the EZH2 and MICU1 were inhibited, HNSCC cells became susceptible to cell cycle arrest and apoptosis. Mitochondrial membrane potential and cytosolic Ca²⁺ concentration analysis suggested that EZH2 and MICU1 were required to maintain mitochondrial membrane potential stability. A xenograft tumor model was used to confirm that EZH2 depletion inhibited HNSCC cell growth and induced tumor cell apoptosis. In summary, EZH2 is a potential anti-tumor target in HNSCC.

Cancer stem cell markers in prostate cancer: an immunohistochemical study of ALDH1, SOX2 and EZH2

The aims of this study were to investigate the immunohistochemical expression and potential prognostic significance of putative cancer stems cell markers ALDH1, EZH2 and SOX2 in prostate cancer.A total of 142 consecutive radical prostatectomies submitted to one laboratory with a diagnosis of prostatic adenocarcinoma between 2008 and 2012 were retrieved and retrospectively studied. Immunohistochemistry for the three markers was performed in each case and both univariate and multivariate analyses were undertaken to evaluate the correlation between the staining patterns and known histopathological prognostic features.ALDH1 showed a statistically significant association with tumour stage p < 0.001), extraprostatic extension (p < 0.001) and lymphovascular invasion (p = 0.001). EZH2 correlated with Gleason score (p = 0.044) and lymph node metastases (p = 0.023). SOX2 showed a statistically significant correlation with lymphovascular invasion only (p = 0.018) in both univariate and multivariate analyses.Cancer stem cell markers are variably expressed in prostate adenocarcinoma and immunohistochemical staining for ALDH1 and EZH2 may have a role in predicting tumour aggressiveness before treatment of prostate cancer.

MiR-26a and miR-138 block the G1/S transition by targeting the cell cycle regulating network in prostate cancer cells

PURPOSE

The tumor-suppressive microRNAs miR-26a and miR-138 are significantly down-regulated in prostate cancer (PCa) and have been identified as direct regulators of enhancer of zeste homolog 2 (EZH2), which is a known oncogene in PCa. In the present study, the influence of miR-26a and miR-138 on EZH2 and cellular function including the impact on the cell cycle regulating network was evaluated in PCa cells.

METHODS

PC-3 and DU-145 PCa cells were transfected with 100 nM of miRNA mimics, siRNA against EZH2 (siR-EZH2) or control constructs for 4 h. Analyses of gene expression and cellular function were conducted 48 h after transfection.

RESULTS

Both miRNAs influenced the EZH2 expression and activity only marginally, whereas siR-EZH2 led to a notable decrease of the EZH2 expression and activity. Both miRNAs inhibited short- and/or long-term proliferation of PCa cells but showed no effect on viability and apoptosis. In PC-3 cells, miR-26a and miR-138 caused a significant surplus of cells in the G0/G1 phase of 6 and 12 %, respectively, thus blocking the G1/S-phase transition. Treatment with siR-EZH2 was without substantial influence on cellular function and cell cycle. Therefore, alternative target genes involved in cell cycle regulation were identified in silico. MiR-26a significantly diminished the expression of its targets CCNE1, CCNE2 and CDK6, whereas CCND1, CCND3 and CDK6 were suppressed by their regulator miR-138.

CONCLUSIONS

The present findings suggest an anti-proliferative role for miR-26a and miR-138 in PCa by blocking the G1/S-phase transition independent of EZH2 but via a concerted inhibition of crucial cell cycle regulators.

Divergent clonal evolution of castration-resistant neuroendocrine prostate cancer

An increasingly recognized resistance mechanism to androgen receptor (AR)-directed therapy in prostate cancer involves epithelial plasticity, in which tumor cells demonstrate low to absent AR expression and often have neuroendocrine features. The etiology and molecular basis for this 'alternative' treatment-resistant cell state remain incompletely understood. Here, by analyzing whole-exome sequencing data of metastatic biopsies from patients, we observed substantial genomic overlap between castration-resistant tumors that were histologically characterized as prostate adenocarcinomas (CRPC-Adeno) and neuroendocrine prostate cancer (CRPC-NE); analysis of biopsy samples from the same individuals over time points to a model most consistent with divergent clonal evolution. Genome-wide DNA methylation analysis revealed marked epigenetic differences between CRPC-NE tumors and CRPC-Adeno, and also designated samples of CRPC-Adeno with clinical features of AR independence as CRPC-NE, suggesting that epigenetic modifiers may play a role in the induction and/or maintenance of this treatment-resistant state. This study supports the emergence of an alternative, 'AR-indifferent' cell state through divergent clonal evolution as a mechanism of treatment resistance in advanced prostate cancer.

Methylome-wide Sequencing Detects DNA Hypermethylation Distinguishing Indolent from Aggressive Prostate Cancer

A critical need in understanding the biology of prostate cancer is characterizing the molecular differences between indolent and aggressive cases. Because DNA methylation can capture the regulatory state of tumors, we analyzed differential methylation patterns genome-wide among benign prostatic tissue and low-grade and high-grade prostate cancer and found extensive, focal hypermethylation regions unique to high-grade disease. These hypermethylation regions occurred not only in the promoters of genes but also in gene bodies and at intergenic regions that are enriched for DNA-protein binding sites. Integration with existing RNA-sequencing (RNA-seq) and survival data revealed regions where DNA methylation correlates with reduced gene expression associated with poor outcome. Regions specific to aggressive disease are proximal to genes with distinct functions from regions shared by indolent and aggressive disease. Our compendium of methylation changes reveals crucial molecular distinctions between indolent and aggressive prostate cancer.

EZH2 dependent H3K27me3 is involved in epigenetic silencing of ID4 in prostate cancer

Inhibitor of DNA binding/differentiation protein 4 (ID4) is dominant negative helix loop helix transcriptional regulator is epigenetically silenced due to promoter hyper-methylation in many cancers including prostate. However, the underlying mechanism involved in epigenetic silencing of ID4 is not known. Here, we demonstrate that ID4 promoter methylation is initiated by EZH2 dependent tri-methylation of histone 3 at lysine 27 (H3K27me3). ID4 expressing (LNCaP) and non-expressing (DU145 and C81) prostate cancer cell lines were used to investigate EZH2, H3K27me3 and DNMT1 enrichment on ID4 promoter by Chromatin immuno-precipitation (ChIP). Enrichment of EZH2, H3K27Me3 and DNMT1 in DU145 and C81 cell lines compared to ID4 expressing LNCaP cell line. Knockdown of EZH2 in DU145 cell line led to re-expression of ID4 and decrease in enrichment of EZH2, H3K27Me3 and DNMT1 demonstrating that ID4 is regulated in an EZH2 dependent manner. ChIP data on prostate cancer tissue specimens and cell lines suggested EZH2 occupancy and H3K27Me3 marks on the ID4 promoter. Collectively, our data indicate a PRC2 dependent mechanism in ID4 promoter silencing in prostate cancer through recruitment of EZH2 and a corresponding increase in H3K27Me3. Increased EZH2 but decreased ID4 expression in prostate cancer strongly supports this model.

Histone H2A.Z deregulation in prostate cancer. Cause or effect?

Genetic and epigenetic changes are at the root of all cancers. The epigenetic component involves alterations of the post-synthetic modifications of DNA (methylation) and histones (histone posttranslational modifications, PTMs) as well as of those of their molecular "writers," "readers," and "erasers." Noncoding RNAs (ncRNA) can also play a role. Here, we focus on the involvement of histone alterations in cancer, in particular that of the histone variant H2A.Z in the etiology of prostate cancer. The structural mechanisms putatively responsible for the contribution of H2A.Z to oncogenic gene expression programs are first described, followed by what is currently known about the involvement of this histone variant in the regulation of androgen receptor regulated gene expression. The implications of this and their relevance to oncogene deregulation in different stages of prostate cancer, including the progression toward androgen independence, are discussed. This review underscores the increasing awareness of the epigenetic contribution of histone variants to oncogenic progression.

Chromatin Memory in the Development of Human Cancers

Cancer is a complex disease with acquired genomic and epigenomic alterations that affect cell proliferation, viability and invasiveness. Almost all the epigenetic mechanisms including cytosine methylation and hydroxymethylation, chromatin remodeling and non-coding RNAs have been found associate with carcinogenesis and cancer specific expression profile. Altered histone modification as an epigenetic hallmark is frequently found in tumors. Understanding the epigenetic alterations induced by carcinogens or infectious agents may help us understand early epigenetic changes prior to the development of cancer. In this review, we focus on chromatin remodeling and the associated histone modifiers in the development of cancer; the application of these modifiers as a cancer therapy target in different clinical trial phases is also discussed.

The role of microRNAs in the regulation of apoptosis in lung cancer and its application in cancer treatment

Lung cancer remains to be one of the most common and serious types of cancer worldwide. While treatment is available, the survival rate of this cancer is still critically low due to late stage diagnosis and high frequency of drug resistance, thus highlighting the pressing need for a greater understanding of the molecular mechanisms involved in lung carcinogenesis. Studies in the past years have evidenced that microRNAs (miRNAs) are critical players in the regulation of various biological functions, including apoptosis, which is a process frequently evaded in cancer progression. Recently, miRNAs were demonstrated to possess proapoptotic or antiapoptotic abilities through the targeting of oncogenes or tumor suppressor genes. This review examines the involvement of miRNAs in the apoptotic process of lung cancer and will also touch on the promising evidence supporting the role of miRNAs in regulating sensitivity to anticancer treatment.

Validation of stem cell markers in clinical prostate cancer: α6-integrin is predictive for non-aggressive disease

BACKGROUND

Stem cells are postulated to mediate prostate cancer progression, and represent a small fraction of the entire tumor. Various proteins (α2-integrin, α6-integrin, CD117, CD133, EZH2, OCT3/4) are associated with a prostate cancer stem cell phenotype in cell lines and xenografts. Our objective was to investigate expression of stem cell markers in clinical prostate cancer in relation to outcome.

METHODS

We validated immunohistochemical expression of stem cell markers in 481 prostate cancer patients and correlated expression with clinicopathologic parameters.

RESULTS

Sporadic expression of α2-integrin was present in a fraction of tumor cells (<5%) in 94.7% of tumors and associated with PSA > 10 ng/ml (P = 0.04). α6-Integrin expression (<5%) occurred in 28.4% patients, while ≥5% α6-integrin expression was associated with PSA≤10 ng/ml (P = 0.01), Gleason score <7 (P < 0.01) and pT2-disease (P = 0.02). α6-integrin was predictive for biochemical recurrence (P < 0.01), local recurrence (P = 0.03) and disease specific death (P = 0.03). EZH2 expression was generally low with 2.6% of tumors showing ≥1% positive cells. EZH2 was associated with Gleason score ≥7 (P = 0.01) and biochemical recurrence (P = 0.01). We did not identify expression of CD117, CD133, and OCT3/4 in prostate cancer samples.

CONCLUSIONS

Expression of α2-integrin and EZH2 in a small fraction of prostate cancer cells is supportive for their role as stem cell marker. Although α6-integrin was not a unique stem cell marker, it was predictive for prostate cancer biochemical and local recurrence, and disease specific death. The validity of CD117, CD133, and OCT3/4 as prostate cancer stem cell marker is questionable since these proteins were not expressed in clinical prostate cancer.

Deregulated expression of selected histone methylases and demethylases in prostate carcinoma

Prostate cancer (PCa), a leading cause of cancer-related morbidity and mortality, arises through the acquisition of genetic and epigenetic alterations. Deregulation of histone methyltransferases (HMTs) or demethylases (HDMs) has been associated with PCa development and progression. However, the precise influence of altered HMTs or HDMs expression and respective histone marks in PCa onset and progression remains largely unknown. To clarify the role of HMTs and HDMs in prostate carcinogenesis, expression levels of 37 HMTs and 20 HDMs were assessed in normal prostate and PCa tissue samples by RT-qPCR. SMYD3, SUV39H2, PRMT6, KDM5A, and KDM6A were upregulated, whereas KMT2A-E (MLL1-5) and KDM4B were downregulated in PCa, compared with normal prostate tissues. Remarkably, PRMT6 was the histone modifier that best discriminated normal from tumorous tissue samples. Interestingly, EZH2 and SMYD3 expression levels significantly correlated with less differentiated and more aggressive tumors. Remarkably, SMYD3 expression levels were of independent prognostic value for the prediction of disease-specific survival of PCa patients with clinically localized disease submitted to radical prostatectomy. We concluded that expression profiling of HMTs and HDMs, especially SMYD3, might be of clinical usefulness for the assessment of PCa patients and assist in pre-therapeutic decision-making.

Epigenetic therapy with the histone methyltransferase EZH2 inhibitor 3-deazaneplanocin A inhibits the growth of cholangiocarcinoma cells

Enhancer of zeste homolog 2 (EZH2) is involved in malignant transformation and the biological aggressiveness of several human malignancies. Growing evidence indicates that EZH2 may be an appropriate therapeutic target for malignancies, including cholangiocarcinoma. Recently, an S-adenosyl-L-homocysteine hydrolase inhibitor, 3-deazaneplanocin A (DZNep) was shown to deplete and inhibit EZH2. The aim of this study was to determine the effect of DZNep and the combination of gemcitabine and DZNep in cholangiocarcinoma cells. The effects of DZNep and its combination with gemcitabine were assessed in the cholangiocarcinoma cell lines RBE and TFK-1. DZNep depleted the cellular levels of EZH2 and inhibited the associated histone H3 lysine 27 trimethylation. DZNep treatment resulted in the inhibition of proliferation in the cholangiocarcinoma cell lines, and the combination of DZNep and gemcitabine showed synergistic inhibition of cell proliferation. DZNep induced apoptosis and G1 phase cell cycle arrest in cholangiocarcinoma cells, and the combination of DZNep and gemcitabine enhanced the induced apoptosis and G1 arrest when compared with gemcitabine alone. Inhibition of cell proliferation by DZNep was partially associated with upregulation of p16INK4a and p17KIP1. The present study shows that DZNep inhibits cell proliferation by inducing G1 arrest and apoptosis. These results indicate that an epigenetic therapy that pharmacologically targets EZH2 via DZNep may constitute a novel approach for the treatment of cholangiocarcinoma.

Identification of EZH2 and EZH1 small molecule inhibitors with selective impact on diffuse large B cell lymphoma cell growth

The histone methyltransferase enhancer of Zeste homolog 2 (EZH2) is a candidate oncogene due to its prevalent overexpression in malignant diseases, including late stage prostate and breast cancers. The dependency of cancer cells on EZH2 activity is also predicated by recurrent missense mutations residing in the catalytic domain of EZH2 that have been identified in subtypes of diffuse large B cell lymphoma, follicular lymphoma and melanoma. Herein, we report the identification of a highly selective small molecule inhibitor series of EZH2 and EZH1. These compounds inhibit wild-type and mutant versions of EZH2 with nanomolar potency, suppress global histone H3-lysine 27 methylation, affect gene expression, and cause selective proliferation defects. These compounds represent a structurally distinct EZH2 inhibitor chemotype for the exploration of the role of Polycomb Repressive Complex 2-mediated H3K27 methylation in various biological contexts.

Future prospects in the diagnosis and management of localized prostate cancer

Prostate cancer (PCa) is the commonest visceral cancer in men worldwide. Introduction of serum PSA as a highly specific biomarker for prostatic diseases has led to a dramatic increase in the diagnosis of early stage PCa in last decades. Guidelines underline that benefits as well as risks and squeals of early diagnosis and treatment should be discussed with patients. There are several new biomarkers (Pro-PSA, PCA-3 test, and TMPRSS2-ERG) available on the market but new ones are awaited in order to improve specificity and sensitivity. Investigators have also focused on identifying and isolating the gene, or genes, responsible for PCa. Current definitive treatment options for clinically localized PCa with functional and oncological success rates up to 95% include surgery (radical prostatectomy), external-beam radiation therapy, and interstitial radiation therapy (brachytherapy). Potential complications of overdiagnosis and overtreatment have resulted in arguments about screening and introduced a new management approach called "active surveillance." Improvements in diagnostic techniques, especially multiparametric magnetic resonance imaging, significantly ameliorated the accuracy of tumor localization and local staging. These advances will further support focal therapies as emerging treatment alternatives for localized PCa. As a conclusion, revolutionary changes in the diagnosis and management of PCa are awaited in the near future.

Genomic deregulation of the E2F/Rb pathway leads to activation of the oncogene EZH2 in small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive lung neoplasm with extremely poor clinical outcomes and no approved targeted treatments. To elucidate the mechanisms responsible for driving the SCLC phenotype in hopes of revealing novel therapeutic targets, we studied copy number and methylation profiles of SCLC. We found disruption of the E2F/Rb pathway was a prominent feature deregulated in 96% of the SCLC samples investigated and was strongly associated with increased expression of EZH2, an oncogene and core member of the polycomb repressive complex 2 (PRC2). Through its catalytic role in the PRC2 complex, EZH2 normally functions to epigenetically silence genes during development, however, it aberrantly silences genes in human cancers. We provide evidence to support that EZH2 is functionally active in SCLC tumours, exerts pro-tumourigenic functions in vitro, and is associated with aberrant methylation profiles of PRC2 target genes indicative of a “stem-cell like” hypermethylator profile in SCLC tumours. Furthermore, lentiviral-mediated knockdown of EZH2 demonstrated a significant reduction in the growth of SCLC cell lines, suggesting EZH2 has a key role in driving SCLC biology. In conclusion, our data confirm the role of EZH2 as a critical oncogene in SCLC, and lend support to the prioritization of EZH2 as a potential therapeutic target in clinical disease.

EZH2 inhibition: targeting the crossroad of tumor invasion and angiogenesis

Tumor angiogenesis and metastatic spreading are two highly interconnected phenomena, which contribute to cancer-associated deaths. Thus, the identification of novel strategies to target angiogenesis and metastatic spreading is crucial. Polycomb genes are a set of epigenetic effectors, structured in multimeric repressive complexes. EZH2 is the catalytic subunit of Polycomb repressive complex 2 (PRC2), which methylates histone H3 lysine 27, thereby silencing several tumor-suppressor genes. EZH2 is essential for cancer stem cell self-renewal. Interestingly, cancer stem cells are thought to be the seeds of metastatic spreading and are able to differentiate into tumor-associated endothelial cells. Pre-clinical studies showed that EZH2 is able to silence several anti-metastatic genes (e.g., E-cadherin and tissue inhibitors of metalloproteinases), thereby favoring cell invasion and anchorage-independent growth. In addition, EZH2 seems to play a crucial role in the regulation of tumor angiogenesis. High EZH2 expression predicts poor prognosis, high grade, and high stage in several cancer types. Recently, a small molecule inhibitor of PRC2 (DZNeP) demonstrated promising anti-tumor activity, both in vitro and in vivo. Interestingly, DZNeP was able to inhibit cancer cell invasion and tumor angiogenesis in prostate and brain cancers, respectively. At tumor-inhibiting doses, DZNeP is not harmful for non-transformed cells. In the present manuscript, we review current evidence supporting a role of EZH2 in metastatic spreading and tumor angiogenesis. Using Oncomine datasets, we show that DZNeP targets are specifically silenced in some metastatic cancers, and some of them may inhibit angiogenesis. Based on this evidence, we propose the development of EZH2 inhibitors as anti-angiogenic and anti-metastatic therapy.

Developmental and androgenic regulation of chromatin regulators EZH2 and ANCCA/ATAD2 in the prostate Via MLL histone methylase complex

BACKGROUND

Chromatin regulators ANCCA and EZH2 are overexpressed in prostate cancer and play crucial roles in androgen-stimulated and castration-refractory prostate tumor growth and survival. However, how their expression is regulated in the tumors and whether they play a role in prostate development remains unclear.

METHODS

Prostate tissue from different developmental stages of mouse and human were examined by IHC, qRT-PCR and Western for expression of ANCCA, EZH2, and Ki-67. Animals were castrated and T-implanted for the expression response in normal prostate and tumors. siRNA knockdown and ChIP were performed for the mechanism of ANCCA regulation of EZH2.

RESULTS

In contrast to their very low level expression in adult prostate, ANCCA and EZH2 are strongly expressed in the epithelium and mesenchyme of mouse and human UGS. Their expression becomes more restricted to epithelial cells during later development and displays a second peak during puberty, which correlates with the proliferative status of the epithelium. Importantly, their expression in normal prostate and tumors is strongly suppressed by castration and markedly induced by testosterone replacement. While androgen suppresses EZH2 in CRPC cells, in LNCaP cells, physiological concentrations of androgen stimulate expression of PRC2 genes (EZH2, SUZ12, and EED), which is mediated by androgen-induced ANCCA and involves E2F and histone H3K4me3 methylase MLL1 complex.

CONCLUSION

EZH2 and ANCCA are androgen regulated and strongly expressed in early prostate morphogenesis and during puberty, suggesting their important role in prostate development. Regulation of EZH2 by ANCCA emphasizes bromodomain protein ANCCA as a potential therapeutic target against prostate cancer.

A rapid ultra HPLC-MS/MS method for the quantitation and pharmacokinetic analysis of 3-deazaneplanocin A in mice

3-Deazaneplanocin A (DZNep) has been shown to have anti-cancer activity in numerous cancer types and its continued preclinical, and eventual clinical, drug development will require rapid and sensitive bioanalytical methods in order to quantitate this drug for pharmacokinetic analyses. The ultra HPLC with positive thermospray tandem mass spectrometric (LC-MS/MS) detection affords the most sensitive (limit of quantitation 5ng/mL) and rapid (3min run time) bioanalytical method to date for DZNep. Due to the polar nature of this drug and the internal standard (tubercidin), a hydrophilic-interaction column (HILIC) was used. The method was accurate, with less than 10% deviation from nominal values, as well as precise, where both within-day and between-day precisions were less than 15%. A liquid-liquid extraction procedure was able to recover ∼90% of drug from a small volume (50μL) of mouse plasma. This method was successfully applied to a pharmacokinetic study in mice intravenously injected with DZNep.

Epigenetic therapy with 3-deazaneplanocin A, an inhibitor of the histone methyltransferase EZH2, inhibits growth of non-small cell lung cancer cells

EZH2 (enhancer of zeste homolog 2) is the catalytic subunit of PRC2 (polycomb repressive complex 2), which mediates histone methyltransferase activity and functions as transcriptional repressor involved in gene silencing. EZH2 is involved in malignant transformation and biological aggressiveness of several human malignancies. We previously demonstrated that non-small cell lung cancers (NSCLCs) also overexpress EZH2 and that high expression of EZH2 correlates with poor prognosis. Growing evidence indicates that EZH2 may be an appropriate therapeutic target in malignancies, including NSCLCs. Recently, an S-adenosyl-l-homocysteine hydrolase inhibitor, 3-Deazaneplanocin A (DZNep), has been shown to deplete and inhibit EZH2. The aim of this study was to determine the effect of DZNep in NSCLC cells. Knockdown of EZH2 by small-interfering RNA (siRNA) resulted in decreased growth of four NSCLC cell lines. MTT assays demonstrated that DZNep treatment resulted in dose-dependent inhibition of proliferation in the NSCLC cell lines with a half maximal inhibitory concentration (IC50) ranging from 0.08 to 0.24 μM. Immortalized but non-cancerous bronchial epithelial and fibroblast cell lines were less sensitive to DZNep than the NSCLC cell lines. Soft agarose assays demonstrated that anchorage-independent growth was also reduced in all three NSCLC cell lines that were evaluated using this assay. Flow cytometry analysis demonstrated that DZNep induced apoptosis and G1 cell cycle arrest in NSCLC cells, which was partially associated with cyclin A decrease and p27(Kip1) accumulation. DZNep depleted cellular levels of EZH2 and inhibited the associated histone H3 lysine 27 trimethylation. These results indicated that an epigenetic therapy that pharmacologically targets EZH2 via DZNep may constitute a novel approach to treatment of NSCLCs.

Development and validation of reagents and assays for EZH2 peptide and nucleosome high-throughput screens

Histone methyltransferases (HMT) catalyze the methylation of histone tail lysines, resulting in changes in gene transcription. Misregulation of these enzymes has been associated with various forms of cancer, making this target class a potential new area for the development of novel chemotherapeutics. EZH2 is the catalytic component of the polycomb group repressive complex (PRC2), which selectively methylates histone H3 lysine 27 (H3K27). EZH2 is overexpressed in prostate, breast, bladder, brain, and other tumor types and is recognized as a molecular marker for cancer progression and aggressiveness. Several new reagents and assays were developed to aid in the identification of EZH2 inhibitors, and these were used to execute two high-throughput screening campaigns. Activity assays using either an H3K27 peptide or nucleosomes as substrates for methylation are described. The strategy to screen EZH2 with either a surrogate peptide or a natural substrate led to the identification of the same tractable series. Compounds from this series are reversible, are [(3)H]-S-adenosyl-L-methionine competitive, and display biochemical inhibition of H3K27 methylation.

Up-regulation of enhancer of zeste homolog 2 is associated positively with cyclin D1 overexpression and poor clinical outcome in head and neck squamous cell carcinoma

BACKGROUND

The authors previously observed that enhancer of zeste homolog 2 (EZH2) overexpression was associated significantly with the development of oral cancer. In the current study, they investigated whether EZH2 can function as a prognostic predictor for patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

Expression levels of EZH2 in HNSCC cells were detected using reverse transcriptase-polymerase chain reaction (PCR) and Western blot analyses. In addition, the effects of EZH2 ablation on the proliferation and invasion of HNSCC cells were investigated through small interfering RNA (siRNA)-mediated knockdown. Real-time PCR and immunohistochemistry were used to evaluate EZH2 and cyclin D1 expression in 46 HNSCC samples, and the expression levels also were re-evaluated in 124 independent samples by immunohistochemistry.

RESULTS

EZH2 expression was elevated remarkably in HNSCC specimens and cell lines. Upon EZH2 silencing, the proliferation and invasion of HNSCC cells were remarkably suppressed. EZH2 expression frequently was correlated with cyclin D1 expression (P = .034) and tumor differentiation (P = .020). In addition, both EZH2 messenger RNA levels and EZH2 protein levels were strongly associated with signs of histologic severity (P = .012 and P = .032, respectively). Univariate analysis revealed that high EZH2 expression was associated with worse overall survival (P = .001) and disease-free survival (P = .002). The combined expression of EZH2 and cyclin D1 had superior prognostic ability for patients with HNSCC than the expression of either marker alone. In multivariate analysis, EZH2 expression was identified as an independent predictor of overall and disease-free survival.

CONCLUSIONS

The current results indicated that EZH2 is an independent prognostic indicator for patients with HNSCC. In addition, an analysis of the combined expression of EZH2 and cyclin D1 can serve as a more powerful prognostic predictor for patients with HNSCC.

Myc enforces overexpression of EZH2 in early prostatic neoplasia via transcriptional and post-transcriptional mechanisms

EZH2 is part of the PRC2 polycomb repressive complex that is overexpressed in multiple cancer types and has been implicated in prostate cancer initiation and progression. Here, we identify EZH2 as a target of the MYC oncogene in prostate cancer and show that MYC coordinately regulates EZH2 through transcriptional and post-transcriptional means. Although prior studies in prostate cancer have revealed a number of possible mechanisms of EZH2 upregulation, these changes cannot account for the overexpression EZH2 in many primary prostate cancers, nor in most cases of high grade PIN. We report that upregulation of Myc in the mouse prostate results in overexpression of EZH2 mRNA and protein which coincides with reductions in miR-26a and miR-26b, known regulators of EZH2 in some non-prostate cell types, albeit not in others. Further, in human prostate cancer cells, Myc negatively regulates miR-26a and miR-26b via direct binding to their parental Pol II gene promoters, and forced overexpression of miR-26a and miR-26b in prostate cancer cells results in decreased EZH2 levels and suppressed proliferation. In human clinical samples, miR-26a and miR-26b are downregulated in most primary prostate cancers. As a separate mechanism of EZH2 mRNA upregulation, we find that Myc binds directly to and activates the transcription of the EZH2 promoter. These results link two major pathways in prostate cancer by providing two additional and complementary Myc-regulated mechanisms by which EZH2 upregulation occurs and is enforced during prostatic carcinogenesis. Further, the results implicate EZH2-driven mechanisms by which Myc may stimulate prostate tumor initiation and disease progression.

MicroRNAs: novel biomarkers for lung cancer diagnosis, prediction and treatment

MicroRNAs (miRNAs) are short non-protein-coding RNAs that post-transcriptionally regulate mRNA expression. A large body of evidence has identified important roles for these regulators in cell proliferation, differentiation, apoptosis and metabolism, as well as activation of oncogenic and antioncogenic signals. Aberrant expression of miRNAs has been found in most human malignancies and is strongly associated with tumorigenesis, prediction, diagnosis, progress, treatment and prognosis. Thus, miRNAs may become an intriguing and promising therapeutic target for many diseases, including cancer. In addition, research into miRNAs may provide insight into the mechanisms underlying tumor occurrence, progression and metastasis. This review summarizes the current knowledge of miRNAs, their roles in lung cancer and avenues for future research.

Enhancer of Zeste Homolog 2 Overexpression in Nasopharyngeal Carcinoma: An Independent Poor Prognosticator That Enhances Cell Growth

PURPOSE

As a key component of polycomb-repressive complex 2, enhancer of zeste homolog 2 (EZH2) represses target genes through histone methylation and is frequently overexpressed and associated with poor prognosis in common carcinomas. For the first time, we reported EZH2 expression and its biological and clinical significance in nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS

In NPC cell lines and specimens, endogenous expression of EZH2 mRNA and protein was determined by semiquantitative reverse transcription-polymerase chain reaction and immunoblotting, respectively. To analyze the effect on cell growth, stable silencing of EZH2 was established in EZH2-expressing TW02 NPC cells with RNA interference. EZH2 immunolabeling was assessable for 89 primary NPC biopsy samples and correlated with clinicopathological variables, disease-specific survival (DSS), and overall survival (OS).

RESULTS

Growth activity of TW02 cells was significantly suppressed (p < 0.001) with stable EZH2 silencing. Compared with normal nasopharyngeal tissue, expression levels of EZH2 transcript and protein were apparently upregulated in NPC specimens. As a continuous variable, higher EZH2 expression preferentially occurred in NPCs of T3 to T4 stages (p = 0.03) and significantly predicted inferior DSS (p = 0.0010) and OS (p = 0.004). The prognostic implications for DSS (p = 0.010) and OS (p = 0.006) still remained valid when using the median (≥ 60%) of EZH2 immunolabeling index to dichotomize the cohort. In the multivariate model, higher EZH2 expression was an independent adverse factor of both DSS (p = 0.012) and OS (p = 0.011), along with American Joint Committee on Cancer Stages III to IV (p = 0.024 for DSS, p = 0.017 for OS).

CONCLUSION

At least partly through promoting cell growth, EZH2 implicates disease progression, confers tumor aggressiveness, and represents an independent adverse prognosticator in patients with NPC.

A cell-based high-throughput screening assay to measure cellular histone h3 lys27 trimethylation with a modified dissociation-enhanced lanthanide fluorescent immunoassay

Histone proteins are subject to several modifications, including phosphorylation, acetylation, methylation, sumoylation, and ubiquitination. These posttranslational modifications play critical roles in chromatin structure and gene transcription. Because of their involvement in the progression of a variety of diseases, histone modifications are attracting increased attention. We report herein a high-throughput DELFIA assay to quantify H3K27me3 in the prostate cancer cell line, PC3. Using a high binding MaxiSorp plate, we were able to eliminate the need for the capture antibody. We also developed an effective method, a combination of "freeze-thaw" and 0.2 N HCl, to extract histone proteins in PC3 cells cultured in a 384-well plate. To compensate for cell viability change, we normalized H3K27me3 signal to the total amount of H3 in each sample well. As a result, we show that the assay has a good dynamic range with a robust assay window. Using a methlytransferase inhibitor, DZNep, we show that the change of H3K27me3 signal is target specific. This method simplifies the logistics in screening and profiling and reduces the cost per well to an acceptable level for high-throughput screening. The findings presented here should be applicable to other assays involving binding and extraction of histone proteins.

Epigenetic factors in cancer development: polycomb group proteins

The role of chromatin-modifying factors in cancer biology emerged exponentially in the last 10 years, and increased attention has been focused on Polycomb group (PcG) proteins and their enzymatic activities. PcG proteins are repressive chromatin modifiers required for proliferation and development. The frequent deregulation of PcG activities in human tumors has direct oncogenic effects and results, essential for cancer cell proliferation. Here we will review the recent findings regarding PcG proteins in prospective tumor development, focusing on the molecular mechanisms that deregulate PcG expression in different tumors, at the downstream pathways to PcG expression (that contribute to cancer development) and at the mechanisms that regulate PcG recruitment to specific targets. Finally, we will speculate on the benefit of PcG inhibition for cancer treatment, reviewing potential pharmacological strategies.

Down-regulation of the histone methyltransferase EZH2 contributes to the epigenetic programming of decidualizing human endometrial stromal cells

Differentiation of human endometrial stromal cells (HESC) into decidual cells represents a highly coordinated process essential for embryo implantation. We show that decidualizing HESC down-regulate the histone methyltransferase enhancer of Zeste homolog 2 (EZH2), resulting in declining levels of trimethylation of histone 3 on lysine 27 (H3K27me3) at the proximal promoters of key decidual marker genes PRL and IGFBP1. Loss of H3K27me3 was associated with a reciprocal enrichment in acetylation of the same lysine residue, indicating active remodeling from repressive to transcriptionally permissive chromatin. Chromatin immunoprecipitation coupled with DNA microarray analysis demonstrated that decidualization triggers genome-wide changes in H3K27me3 distribution that only partly overlap those observed upon EZH2 knockdown in undifferentiated HESC. Gene ontology revealed that gain of the repressive H3K27me3 mark in response to decidualization and upon EZH2 knockdown in undifferentiated cells was enriched at the promoter regions of genes involved in transcriptional regulation and growth/cell proliferation, respectively. However, loss of the H3K27me3 mark (indicating increased chromatin accessibility) in decidualizing cells and upon EZH2 knockdown occurred at selective loci enriched for genes functionally implicated in responses to stimulus. In agreement, EZH2 knockdown in undifferentiated HESC was sufficient to augment the induction of decidual marker genes in response to cyclic AMP and progesterone signaling. Thus, loss of EZH2-dependent methyltransferase activity in the endometrium is integral to the process of chromatin remodeling that enables the transition from a proliferative to a decidual phenotype in response to differentiation cues.

Glutathione-S-transferase pi 1(GSTP1) gene silencing in prostate cancer cells is reversed by the histone deacetylase inhibitor depsipeptide

Gene silencing by epigenetic mechanisms is frequent in prostate cancer (PCA). The link between DNA hypermethylation and histone modifications is not completely understood. We chose the GSTP1 gene which is silenced by hypermethylation to analyze the effect of the histone deacetylase inhibitor depsipeptide on DNA methylation and histone modifications at the GSTP1 promoter site. Prostate cell lines (PC-3, LNCaP, and BPH-1) were treated with depsipeptide; apoptosis (FACS analysis), GSTP1 mRNA levels (quantitative real-time PCR), DNA hypermethylation (methylation-specific PCR), and histone modifications (chromatin immunoprecipitation) were studied. Depsipeptide induced apoptosis in PCA cells, but not a cell cycle arrest. Depispeptide reversed DNA hypermethylation and repressive histone modifications (reduction of H3K9me2/3 and H3K27me2/3; increase of H3K18Ac), thereby inducing GSTP1 mRNA re-expression. Successful therapy requires both, DNA demethylation and activating histone modifications, to induce complete gene expression of epigenetically silenced genes and depsipeptide fulfils both criteria.

Methylator phenotype of malignant germ cell tumours in children identifies strong candidates for chemotherapy resistance

BACKGROUND

Yolk sac tumours (YSTs) and germinomas are the two major pure histological subtypes of germ cell tumours. To date, the role of DNA methylation in the aetiology of this class of tumour has only been analysed in adult testicular forms and with respect to only a few genes.

METHODS

A bank of paediatric tumours was analysed for global methylation of LINE-1 repeat elements and global methylation of regulatory elements using GoldenGate methylation arrays.

RESULTS

Both germinomas and YSTs exhibited significant global hypomethylation of LINE-1 elements. However, in germinomas, methylation of gene regulatory regions differed little from control samples, whereas YSTs exhibited increased methylation at a large proportion of the loci tested, showing a 'methylator' phenotype, including silencing of genes associated with Caspase-8-dependent apoptosis. Furthermore, we found that the methylator phenotype of YSTs was coincident with higher levels of expression of the DNA methyltransferase, DNA (cytosine-5)-methyltransferase 3B, suggesting a mechanism underlying the phenotype.

CONCLUSION

Epigenetic silencing of a large number of potential tumour suppressor genes in YSTs might explain why they exhibit a more aggressive natural history than germinomas and silencing of genes associated with Caspase-8-dependent cell death might explain the relative resistance of YSTs to conventional therapy.