Role of the EZH2 histone methyltransferase as a therapeutic target in cancer

EZH2-associated tumor malignancy: A prominent target for cancer treatment

The discussion in this review centers around the significant relationships between EZH2 and the initiation, progression, metastasis, metabolism, drug resistance, and immune regulation of cancer. Polycomb group (PcG) proteins, which encompass two primary Polycomb repressor complexes (PRC1 and PRC2), have been categorized. PRC2 consists mainly of four subunits, namely EZH2, EED, SUZ12, and RbAp46/48. As the crucial catalytic component within the PRC2 complex, EZH2 plays a pivotal role in controlling a wide range of biological processes. Overexpression/mutations of EZH2 have been detected in a wide variety of tumors. Several mechanisms of EZH regulation have been identified, including regulation EZH2 mRNA by miRNAs, LncRNAs, accessibility to DNA via DNA-binding proteins, post-translational modifications, and transcriptional regulation. EZH2 signaling triggers cancer progression and may intervene with anti-tumor immunity; therefore it has charmed attention as an effective therapeutic target in cancer therapy. Numerouss nucleic acid-based therapies have been used in the modification of EZH2. In addition to gene therapy approaches, pharmaceutical compounds can be used to target the EZH2 signaling pathway in the treatment of cancer. EZH2-associated tumor cells and immune cells enhance the effects of the immune response in a variety of human malignancies. The combination of epigenetic modifying agents, such as anti-EZH2 compounds with immunotherapy, could potentially be efficacious even in the context of immunosuppressive tumors. Summary, understanding the mechanisms underlying resistance to EZH2 inhibitors may facilitate the development of novel drugs to prevent or treat relapse in treated patients.

Distinct Regulation of EZH2 and its Repressive H3K27me3 Mark in Polyomavirus-Positive and -Negative Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive skin cancer for which Merkel cell polyomavirus integration and expression of viral oncogenes small T and Large T have been identified as major oncogenic determinants. Recently, a component of the PRC2 complex, the histone methyltransferase enhancer of zeste homolog 2 (EZH2) that induces H3K27 trimethylation as a repressive mark has been proposed as a potential therapeutic target in MCC. Because divergent results have been reported for the levels of EZH2 and trimethylation of lysine 27 on histone 3, we analyzed these factors in a large MCC cohort to identify the molecular determinants of EZH2 activity in MCC and to establish MCC cell lines' sensitivity to EZH2 inhibitors. Immunohistochemical expression of EZH2 was observed in 92% of MCC tumors (156 of 170), with higher expression levels in virus-positive than virus-negative tumors (P = 0.026). For the latter, we showed overexpression of EZHIP, a negative regulator of the PRC2 complex. In vitro, ectopic expression of the large T antigen in fibroblasts led to the induction of EZH2 expression, whereas the knockdown of T antigens in MCC cell lines resulted in decreased EZH2 expression. EZH2 inhibition led to selective cytotoxicity on virus-positive MCC cell lines. This study highlights the distinct mechanisms of EZH2 induction between virus-negative and -positive MCC.

Chromatin remodeler Activity-Dependent Neuroprotective Protein (ADNP) contributes to syndromic autism

BACKGROUND

Individuals affected with autism often suffer additional co-morbidities such as intellectual disability. The genes contributing to autism cluster on a relatively limited number of cellular pathways, including chromatin remodeling. However, limited information is available on how mutations in single genes can result in such pleiotropic clinical features in affected individuals. In this review, we summarize available information on one of the most frequently mutated genes in syndromic autism the Activity-Dependent Neuroprotective Protein (ADNP).

RESULTS

Heterozygous and predicted loss-of-function ADNP mutations in individuals inevitably result in the clinical presentation with the Helsmoortel-Van der Aa syndrome, a frequent form of syndromic autism. ADNP, a zinc finger DNA-binding protein has a role in chromatin remodeling: The protein is associated with the pericentromeric protein HP1, the SWI/SNF core complex protein BRG1, and other members of this chromatin remodeling complex and, in murine stem cells, with the chromodomain helicase CHD4 in a ChAHP complex. ADNP has recently been shown to possess R-loop processing activity. In addition, many additional functions, for instance, in association with cytoskeletal proteins have been linked to ADNP.

CONCLUSIONS

We here present an integrated evaluation of all current aspects of gene function and evaluate how abnormalities in chromatin remodeling might relate to the pleiotropic clinical presentation in individual"s" with Helsmoortel-Van der Aa syndrome.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Immunotherapy for Chordoma and Chondrosarcoma: Current Evidence

Chordomas and chondrosarcomas are rare but devastating neoplasms that are characterized by chemoradiation resistance. For both tumors, surgical resection is the cornerstone of management. Immunotherapy agents are increasingly improving outcomes in multiple cancer subtypes and are being explored in chordoma and chondrosarcoma alike. In chordoma, brachyury has been identified as a prominent biomarker and potential molecular immunotherapy target as well as PD-1 inhibition. While studies on immunotherapy in chondrosarcoma are sparse, there is emerging evidence and ongoing clinical trials for PD-1 as well as IDH inhibitors. This review highlights potential biomarkers and targets for immunotherapy in chordoma and chondrosarcoma, as well as current clinical evidence and ongoing trials.

Finding an easy way to harmonize: a review of advances in clinical research and combination strategies of EZH2 inhibitors

Enhancer of zeste homolog 2 inhibitors (EZH2i) have garnered increased attention owing to their anticancer activity by targeting EZH2, a well-known cancer-promoting factor. However, some lymphomas are resistant to EZH2i, and EZH2i treatment alone is ineffective in case of EZH2-overexpressing solid tumors. The anti-cancer efficacy of EZH2i may be improved through safe and effective combinations of these drugs with other treatment modalities. Preclinical evidence indicates that combining EZH2i with other therapies, such as immunotherapy, chemotherapy, targeted therapy, and endocrine therapy, has complementary or synergistic antitumor effects. Therefore, elucidating the underlying mechanisms of the individual constituents of the combination therapies is fundamental for their clinical application. In this review, we have summarized notable clinical trials and preclinical studies using EZH2i, their progress, and combinations of EZH2i with different therapeutic modalities, aiming to provide new insights for tumor treatment.

Translating Molecular Profiling of Soft Tissue Sarcomas into Daily Clinical Practice

Soft tissue sarcomas are a group of rare mesenchymal tumors with more than 70 subtypes described. Treatment of these subtypes in an advanced setting is mainly according to a one-size-fits-all strategy indicating a high unmet need of new and more targeted therapeutic options in order to optimize survival. The introduction of advanced molecular techniques in cancer has led to better diagnostics and identification of new therapeutic targets, leading to more personalized treatment and improved prognosis for several cancer types. In sarcoma, a likewise evolution is seen, albeit at a slower pace. This manuscript describes how in the past years advanced molecular profiling in soft tissue sarcomas was able to identify specific and often pathognomonic aberrations, deferring standard sarcoma treatment in favor of more targeted treatment from an oncologist’s point of view.

Epithelioid sarcoma: A clinicopathological study of 12 head and neck cases

OBJECTIVES

To determine the clinicopathological features of epithelioid sarcoma presenting in head and neck region (HNES) and elucidate diagnostic key points and treatment options for HNES.

MATERIALS AND METHODS

A total of 12 HNES cases were collected in our department from 2010 to 2020. Their clinical information and pathological features were documented, and relevant follow-up was performed. Immunohistochemistry was carried to analyze the protein markers of HNES.

RESULTS

Of the 12 HNES cases, 10 were primary tumors and 2 were metastasized from foot and shoulder, respectively. The patients with primary tumors were significantly younger than those with metastasized ones (22.7 vs 41.5, p = .0157), and male patients outnumbered female patients (3:1). Of all HNES cases, 9 were classic subtype, and 3 were proximal subtype. HNES patients had a poor prognosis, with 5-year overall survival of 41.5% and 5-year relapse-free survival of 22.5%. A loss of INI1 was identified as the hallmark of HNES with 83.3% (10/12) of HNES cases presenting as EZH2 positive.

CONCLUSIONS

HNES is more prevalent at younger ages and in males, has a poor prognosis, and exhibits a greater proportion of classic subtype than proximal subtype. EZH2 inhibitor has therapeutic potential in HNES.

EZH2-miRNA Positive Feedback Promotes Tumor Growth in Ovarian Cancer

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

Overexpression of EZH2/NSD2 Histone Methyltransferase Axis Predicts Poor Prognosis and Accelerates Tumor Progression in Triple-Negative Breast Cancer

Two histone methyltransferases, enhancer of zeste homolog 2 (EZH2) and nuclear SET domain-containing 2 (NSD2), are aberrantly expressed in several types of human cancers. However, the regulatory relationship between EZH2 and NSD2 and their prognostic values in breast cancer (BC) have not been fully elucidated. In this study, we demonstrated that EZH2 and NSD2 were overexpressed in BC compared with benign lesions and normal tissues using tissue microarray, immunohistochemistry, and bioinformatic databases. Both EZH2 and NSD2 expression were associated with pathological grade of tumor and lymph node metastasis. A comprehensive survival analysis using Kaplan-Meier Plotter database indicated that EZH2 expression was negatively correlated with relapse-free survival (RFS), overall survival (OS), distant metastasis-free survival (DMFS), and postprogression survival (PPS) in 3951 BC patients, and NSD2 expression was negatively correlated with RFS and DMFS. Notably, EZH2 and NSD2 expression were coordinately higher in triple-negative breast cancer (TNBC) than that in other subtypes. Stable knockdown of EZH2 using lentiviral shRNA vector significantly reduced the proliferation, migration and invasion abilities of TNBC cell line MDA-MB-231 and MDA-MB-468, and downregulated NSD2 expression as well as the levels of H3K27me3 and H3K36me2, two histone methylation markers catalyzed by EZH2 and NSD2, respectively. By contrast, overexpression of EZH2 using adenovirus vector displayed an inverse phenotype. Furthermore, knockdown of NSD2 in EZH2-overexpressing cells could dramatically attenuate EZH2-mediated oncogenic effects. Bioinformatic analysis further revealed the function and pathway enrichments of co-expressed genes and interactive genes of EZH2/NSD2 axis, suggesting that EZH2/NSD2 axis was associated with cell division, mitotic nuclear division and transition of mitotic cell cycle in TNBC. Taken together, EZH2/NSD2 axis may act as a predictive marker for poor prognosis and accelerate the progression of TNBC.

Phase 1 study of tazemetostat in Japanese patients with relapsed or refractory B-cell lymphoma

Background

Tazemetostat is a selective and orally available inhibitor of enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and epigenetic regulator of cellular differentiation programs. We carried out a phase I study of tazemetostat in Japanese patients with relapsed or refractory B‐cell non‐Hodgkin‐type lymphoma (B‐NHL) to evaluate its tolerability, safety, pharmacokinetics, and preliminary antitumor activity.

Methods

Tazemetostat was given orally at a single dose of 800 mg on the first day and 800 mg twice daily (BID: total 1600 mg/d) on following days in a 28‐day/cycle manner. Tazemetostat dose‐limiting toxicity (DLT) was evaluated up to the end of the first treatment cycle. Archival tumor tissues were analyzed for hotspot EZH2 mutations.

Results

As of 15 January 2018, seven patients (four follicular lymphoma [FL] and three diffuse large B‐cell lymphoma [DLBCL]) were enrolled. The median age was 73 (range, 59‐85) years, and the median number of prior chemotherapy regimens was three (range, one to five). No DLT was observed (one patient was not evaluable due to early disease progression). The common treatment‐related adverse events (AEs) were thrombocytopenia and dysgeusia (three patients each; 42.9%). No treatment‐related serious AEs were observed. The objective response rate was 57% (4/7 patients), including responses in three of four patients with FL and one of three patients with DLBCL. An EZH2 mutation was detected in one patient with FL responding to treatment.

Conclusions

Tazemetostat at 800 mg BID showed an acceptable safety profile and promising antitumor activity in Japanese patients with relapsed or refractory B‐NHL.

The Endothelium as a Target for Anti-Atherogenic Therapy: A Focus on the Epigenetic Enzymes EZH2 and SIRT1

Endothelial cell inflammatory activation and dysfunction are key events in the pathophysiology of atherosclerosis, and are associated with an elevated risk of cardiovascular events. Yet, therapies specifically targeting the endothelium and atherosclerosis are lacking. Here, we review how endothelial behaviour affects atherogenesis and pose that the endothelium may be an efficacious cellular target for antiatherogenic therapies. We discuss the contribution of endothelial inflammatory activation and dysfunction to atherogenesis and postulate that the dysregulation of specific epigenetic enzymes, EZH2 and SIRT1, aggravate endothelial dysfunction in a pleiotropic fashion. Moreover, we propose that commercially available drugs are available to clinically explore this postulation.

LincRNA-immunity landscape analysis identifies EPIC1 as a regulator of tumor immune evasion and immunotherapy resistance

Through an integrative analysis of the lincRNA expression and tumor immune response in 9,626 tumor samples across 32 cancer types, we developed a lincRNA-based immune response (LIMER) score that can predict the immune cells infiltration and patient prognosis in multiple cancer types. Our analysis also identified tumor-specific lincRNAs, including EPIC1, that potentially regulate tumor immune response in multiple cancer types. Immunocompetent mouse models and in vitro co-culture assays demonstrated that EPIC1 induces tumor immune evasion and resistance to immunotherapy by suppressing tumor cell antigen presentation. Mechanistically, lincRNA EPIC1 interacts with the histone methyltransferase EZH2, leading to the epigenetic silencing of IFNGR1, TAP1/2, ERAP1/2, and MHC-I genes. Genetic and pharmacological inhibition of EZH2 abolish EPIC1's immune-related oncogenic effect and its suppression of interferon-γ signaling. The EPIC1-EZH2 axis emerges as a potential mechanism for tumor immune evasion that can serve as therapeutic targets for immunotherapy.

Long Non-Coding RNA SNHG1 Regulates the Wnt/β-Catenin and PI3K/AKT/mTOR Signaling Pathways via EZH2 to Affect the Proliferation, Apoptosis, and Autophagy of Prostate Cancer Cell

Background

Prostate cancer (PCa) is the most common malignant cancer in western developed countries, which has seriously threatened the life style and life quality of men. Its pathogenesis and causes remain indistinct. Currently, it is found that lncRNA-SNHG1 (SNHG1) is highly expressed in multiple tumors with proto-oncogene effect, but its function and mechanism in PCa need to be further studied.

Methods

The expression of SNHG1 and EZH2 was detected by RT-qPCR in the 20 pairs of PCa tissue, adjacent tissue and PCa cell lines. They were transfected with siRNA NC, SNHG1 siRNA, EZH2 siRNA, SNHG1 siRNA+empty, and SNHG1 siRNA+EZH2 overexpression. Then, MTT and colony formation assay were used to detect the proliferation and cloning ability of PCa cells LNCaP and PC3. Transwell and flow cytometry were used to measure cell migration and invasion ability and apoptosis level respectively. Immunofluorescence was used to detect the LC3 spot formation. Western blot was used to detect the expression of the autophagy-related proteins, and PI3K/AKT/mTOR and Wnt/β-catenin signaling pathway related proteins. Finally, in vivo nude mice tumorigenesis experiment to explore the effect of SNHG1 expression on PCa.

Results

We found that SNHG1 and EZH2 were up-regulated in PCa tissue and cells. The expression of SNHG1 and EZH2 was positively correlated. RNA pull down and RNA IP assay further confirmed that SNHG1 bound to EZH2. The proliferation, colony formation, migration and invasion of LNCaP and PC3 cells were significantly reduced with the interference with SNHG1or EZH2 compared with the control group. The related proteins of Wnt/β-catenin and PI3K/AKT/mTOR signaling pathway were significantly reduced after the interference with SNHG1 or EZH2; after simultaneous interference with SNHG1 and overexpression of EZH2, the functional effects on LNCaP and PC3 cells interfered with SNHG1 were reversed. These results were also confirmed in vivo nude mice tumor formation experiments.

Conclusions

This study reveals that lncRNA-SNHG1 regulates Wnt/β-catenin and PI3K/AKT/mTOR signaling pathways via EZH2 gene to affect proliferation, apoptosis and autophagy of PCa cells. This experiment provides ideas and experimental basis for the improvement and treatment of PCa.

The functions of EZH2 in immune cells: Principles for novel immunotherapies

Enhancer of zeste homolog 2 (EZH2) is aberrantly expressed or mutated in multiple types of cancer cells and plays an oncogenic role in tumorigenesis and development in most cancers. Results from pilot clinical studies have implied that EZH2 inhibitors have therapeutic potential against some cancers. However, the exact mechanisms by which EZH2 plays oncogenic roles and EZH2 inhibition exerts anticancer effects are incompletely understood. To date, the findings of studies focusing on EZH2 and cancer cells have failed to fully explain the observations in preclinical and clinical studies. Therefore, recent studies about the roles of EZH2 in cancers have shifted from cancer cells to immune cells. The human immune system is a complex network comprising multiple subpopulations of immune cells. Immune cells communicate and interact with cancer cells during cancer development and treatment, dictating the fate of cancer cells. Elucidating the roles of EZH2 in immune cells, especially in cancer patients, promises the identification of novel immunotherapeutic strategies or priming of existing immunotherapies against cancer. Hence, we reviewed the studies focusing on the involvement of EZH2 in various immune cells, aiming to provide ideas for immunotherapies targeting EZH2 in immune cells.

Epithelioid Sarcoma-From Genetics to Clinical Practice

Epithelioid sarcoma is a mesenchymal soft tissue sarcoma often arising in the extremities, usually in young adults with a pick of incidence at 35 years of age. Epithelioid sarcoma (ES) is characterized by the loss of SMARCB1/INI1 (integrase interactor 1) or other proteins of the SWI/SNF complex. Two distinct types, proximal and distal, with varying biology and treatment outcomes, are distinguished. ES is known for aggressive behavior, including a high recurrence rate and regional lymph node metastases. An optimal long-term management strategy is still to be defined. The best treatment of localized ES is wide surgical resection. Neo-adjuvant or adjuvant radiotherapy may be recommended, as it reduces the local recurrence rate. Sentinel lymph node biopsy should be considered in ES patients. Patients with metastatic ES have a poor prognosis with an expected median overall survival of about a year. Doxorubicin-based regimens are recommended for advanced ES. Tazemetostat, an EZH2 methyltransferase, has shown promising results in ES patients. Novel therapies, including immunotherapy, are still needed.

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

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

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

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

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

Translational Pharmacokinetic-Pharmacodynamic Modeling for an Orally Available Novel Inhibitor of Epigenetic Regulator Enhancer of Zeste Homolog 2

PF06821497 has been identified as an orally available small-molecule enhancer of zeste homolog 2 inhibitor. The objectives of the present study were to characterize pharmacokinetic-pharmacodynamic-disease relationships of PF06821497 in xenograft mouse models with diffuse large B-cell lymphoma (Karpas422). An indirect-response model reasonably fit dose-dependent pharmacodynamic responses [histone H3 on lysine 27 (H3K27) me3 inhibition] with an unbound EC ₅₀ of 76 nM, whereas a signal-transduction model sufficiently fit dose-dependent disease responses (tumor growth inhibition) with an unbound tumor stasis concentration (T _sc ) of 168 nM. Thus, effective concentration for 70% of maximal effect (EC₇₀) for H3K27me3 inhibition was roughly comparable to T _sc , suggesting that 70% H3K27me3 inhibition could be required for tumor stasis. Consistently, an integrated pharmacokinetic-pharmacodynamic-disease model adequately describing tumor growth inhibition also suggested that ∼70% H3K27me3 inhibition was associated with tumor stasis. Based on these results, we would propose that an EC₇₀ estimate for H3K27me3 inhibition corresponding to tumor stasis could be considered a minimum target efficacious concentration of PF06821497 in cancer patients. SIGNIFICANCE STATEMENT: Using a mathematical modeling approach, the quantitative relationships of an orally available anticancer small-molecule enhancer of zeste homolog 2 inhibitor, PF06821497, were characterized among pharmacokinetics, pharmacodynamic biomarker inhibition, and disease responses in nonclinical xenograft models with diffuse large B-cell lymphoma. The modeling results suggest that >70% histone H3 on lysine 27 (H3K27) me3 inhibition would be required for tumor stasis (i.e., 100% tumor growth inhibition). Accordingly, we would propose that an effective concentration for 70% of maximal effect estimate for H3K27me3 inhibition could be considered a minimum target efficacious concentration of PF06821497 in cancer patients.

Enhancer of zeste homolog 2 modulates oxidative stress-mediated pyroptosis in vitro and in a mouse kidney ischemia-reperfusion injury model

Enhancer of zeste homolog 2 (EZH2), a well-known methyltransferase, mediates histone H3 lysine 27 trimethylation (H3K27me3) and plays a crucial role in several kidney disease models. However, its role in renal ischemia/reperfusion (I/R) injury still remains unclear. In this study, we found that EZH2 was positively related to renal I/R injury and inhibition of EZH2 with DZNeP alleviated I/R injury and blocked the activation of oxidative stress and pyroptosis in vivo. Similarly, inhibition of EZH2 with either DZNeP or si-RNA also exerted an inhibitory effect on hypoxia/reoxygenation (H/R)-induced oxidative stress and pyroptosis in vitro. Moreover, further study revealed that ablation of reactive oxygen species (ROS) with N-acetyl-cysteine (NAC) suppressed pyroptosis in human renal proximal tubular epithelial cell line cells exposed to H/R stimulation. Furthermore, Nox4, which was positively related to the generation of ROS, was upregulated during H/R process, while it could be reversed by EZH2 inhibition. Consistently, Nox4-mediated ROS generation was attenuated upon inhibition of EZH2 with DZNeP or si-RNA. Additionally, the transcriptional activity of Nox4 was enhanced by the activation of ALK5/Smad2/3 signaling pathway, which was abolished by ALK5 knockdown in vitro. Finally, EZH2 inhibition blocked H/R and I/R-activated ALK5/Smad2/3 pathway and also resulted in an obvious decrease in the transcriptional activity and protein expression levels of Nox4. In conclusion, our results proved that EZH2 inhibition alleviated renal pyroptosis by blocking Nox4-dependent ROS generation through ALK5/Smad2/3 signaling pathway, indicating that EZH2 could be a potential therapeutic target for renal I/R injury.

LncRNA SNHG15: A new budding star in human cancers

OBJECTIVES

Long non-coding RNAs (lncRNAs) represent an important group of non-coding RNAs (ncRNAs) with more than 200 nucleotides in length that are transcribed from the so-called genomic "dark matter." Mounting evidence has shown that lncRNAs have manifested a paramount function in the pathophysiology of human diseases, especially in the pathogenesis and progression of cancers. Despite the exponential growth in lncRNA publications, our understanding of regulatory mechanism of lncRNAs is still limited, and a lot of controversies remain in the current lncRNA knowledge.The purpose of this article is to explore the clinical significance and molecular mechanism of SNHG15 in tumors.

MATERIALS & METHODS

We have systematically searched the Pubmed, Web of Science, Embase and Cochrane databases. We provide an overview of current evidence concerning the functional role, mechanistic models and clinical utilities of SNHG15 in human cancers in this review.

RESULTS

Small nucleolar RNA host gene 15 (SNHG15), a novel lncRNA, is identified as a key regulator in tumorigenesis and progression of various human cancers, including colorectal cancer (CRC), gastric cancer (GC), pancreatic cancer (PC) and hepatocellular carcinoma (HCC). Dysregulation of SNHG15 has been revealed to be dramatically correlated with advanced clinicopathological factors and predicts poor prognosis, suggesting its potential clinical value as a promising biomarker and therapeutic target for cancer patients.

CONCLUSIONS

LncRNA SNHG15 may serve as a prospective and novel biomarker for molecular diagnosis and therapeutics in patients with cancer.

Exposure time versus cytotoxicity for anticancer agents

PURPOSE

Time is a critical factor in drug action. The duration of inhibition of the target or residence time of the drug molecule on the target often guides drug scheduling.

METHODS

The effects of time on the concentration-dependent cytotoxicity of approved and investigational agents [300 compounds] were examined in the NCI60 cell line panel in 2D at 2, 3, 7 and in 3D 11 days.

RESULTS

There was a moderate positive linear relationship between data from the 2-day NCI60 screen and the 3-, 7- and 11-day and a strong positive linear relationship between 3-, 7- and 11-day luminescence screen IC50s by Pearson correlation analysis. Cell growth inhibition by agents selective for a specific cell cycle phase plateaued when susceptible cells were growth inhibited or killed. As time increased the depth of cell growth inhibition increased without change in the IC50. DNA interactive agents had decreasing IC50s with increasing exposure time. Epigenetic agents required longer exposure times; several were only cytotoxic after 11 days' exposure. For HDAC inhibitors, time had little or no effect on concentration response. There were potency differences amongst the three BET bromodomain inhibitors tested, and an exposure duration effect. The PARP inhibitors, rucaparib, niraparib, and veliparib reached IC50s < 10 μM in some cell lines after 11 days.

CONCLUSIONS

The results suggest that variations in compound exposure time may reflect either mechanism of action or compound chemical half-life. The activity of slow-acting compounds may optimally be assessed in spheroid models that can be monitored over prolonged incubation times.

Future directions in soft tissue sarcoma treatment

Sarcoma is a broad term for mesenchymal malignancies that arise from soft tissue or bone. Despite classification by histologic subtype, clinical behavior and response to therapy have great variability. Modern genetic sequencing techniques have been able to identify additional genetic variability and subsequently new targeted therapies. In this review, we discuss the current state of STS diagnostics and treatment and explore some of the more promising areas in which progress is being made. We discuss therapies targeting PDGFRα/KIT, β-Catenin/APC/NOTCH, IDH-1/2 mutations, MDM2 amplifications, EZH2/INI1 expression loss, ALK fusion, and ASPSCR1-TFE3 fusion. We also discuss the progress that has been made within immunotherapies. While soft tissue sarcomas still portend a poor prognosis, these targeted therapies and immunotherapies provide treatment with less toxic side effects.

HOXB13 networking with ABCG1/EZH2/Slug mediates metastasis and confers resistance to cisplatin in lung adenocarcinoma patients

Rationale: Distant metastasis and chemoresistance are the major causes of short survival after initial chemotherapy in lung adenocarcinoma patients. However, the underlying mechanisms remain elusive. Our pilot study identified high expression of the homeodomain transcription factor HOXB13 in chemoresistant lung adenocarcinomas. We aimed to investigate the role of HOXB13 in mediating lung adenocarcinoma chemoresistance.

Methods: Immunohistochemistry assays were employed to assess HOXB13 protein levels in 148 non-small cell lung cancer patients. The role of HOXB13 in lung adenocarcinoma progression and resistance to cisplatin therapy was analyzed in cells, xenografted mice, and patient-derived xenografts. Needle biopsies from 15 lung adenocarcinoma patients who were resistant to cisplatin and paclitaxel therapies were analyzed for HOXB13 and EZH2 protein levels using immunohistochemistry.

Results: High expression of HOXB13 observed in 17.8% of the lung adenocarcinoma patients in this study promoted cancer progression and predicted poor prognosis. HOXB13 upregulated an array of metastasis- and drug-resistance-related genes, including ABCG1, EZH2, and Slug, by directly binding to their promoters. Cisplatin induced HOXB13 expression in lung adenocarcinoma cells, and patient-derived xenografts and depletion of ABCG1 enhanced the sensitivity of lung adenocarcinoma cells to cisplatin therapy. Our results suggest that determining the combined expression of HOXB13 and its target genes can predict patient outcomes.

Conclusions: A cisplatin-HOXB13-ABCG1/EZH2/Slug network may account for a novel mechanism underlying cisplatin resistance and metastasis after chemotherapy. Determining the levels of HOXB13 and its target genes from needle biopsy specimens may help predict the sensitivity of lung adenocarcinoma patients to platinum-based chemotherapy and patient outcomes.

EZH2 plays a crucial role in ischemia/reperfusion-induced acute kidney injury by regulating p38 signaling

OBJECTIVE AND DESIGN

Renal ischemia-reperfusion (IR)-induced acute kidney injury (AKI) remains a major challenge in clinic. The histone methyltransferases enhancer of zest homolog-2 (EZH2) is associated with the development of renal injury. However, the molecular mechanism has not been fully elucidated.

MATERIALS

AKI in C57BL/6 mice was generated by renal IR.

TREATMENTS

The 3-deazaneplanocin A (DZNeP), a selective EZH2 inhibitor, or vehicle was administrated in mice after IR. HK-2 cells were exposed to hypoxia-reoxygenation (H/R) stress.

METHODS

Apoptosis was detected by TUNEL assay or flow cytometry. EZH2, caspase-3, p38, F4/80⁺ macrophages, and CD3⁺ T cells were examined by immunohistochemistry or Western blot. Tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, IL-6, and IL-18 were measured using RT-PCR.

RESULTS

Mice treated with DZNeP exhibited less severe renal dysfunction and tubular injury following IR. EZH2 inhibition decreased apoptotic cells while reducing activation of caspase-3 in kidneys under IR condition. Moreover, EZH2 inhibition impaired the recruitment of CD3⁺ T cells and F4/80⁺ cells in kidneys with IR. Administration of DZNeP suppressed the production of TNF-α, MCP-1, IL-6, and IL-18 in IR-treated kidneys. Of note, EZH2 inhibition reduced p38 phosphorylation in kidneys after IR. In H/R-treated HK-2 cells, DZNeP treatment or EZH2 knockdown reduced apoptosis. EZH2 inhibition inactivated p38 resulting in reduction of active caspase-3 and proinflammatory molecules. By contrast, EZH2 overexpression induced p38 phosphorylation, caspase-3 activation, and production of proinflammatory molecules, which was reversed by SB203580.

CONCLUSIONS

EZH2 plays a crucial role in IR-induced AKI via modulation of p38 signaling. Targeting EZH2/p38 signaling pathway may offer novel strategies to protect kidneys from acute kidney injury induced by ischemia-reperfusion.

Translocation-Related Sarcomas

Chromosomal translocations are observed in approximately 20% of soft tissue sarcomas (STS). With the advances in pathological examination technology, the identification of translocations has enabled precise diagnoses and classifications of STS, and it has been suggested that the presence of and differences in translocations could be prognostic factors in some translocation-related sarcomas. Most of the translocations in STS were not regarded as targets of molecular therapies until recently. However, trabectedin, an alkylating agent, has shown clinical benefits against translocation-related sarcoma based on a modulation of the transcription of the tumor's oncogenic fusion proteins. Many molecular-targeted drugs that are specific to translocations (e.g., anaplastic lymphoma kinase and tropomyosin kinase related fusion proteins) have emerged. The progress in gene technologies has allowed researchers to identify and even induce new translocations and fusion proteins, which might become targets of molecular-targeted therapies. In this review, we discuss the clinical significance of translocation-related sarcomas, including their diagnoses and targeted therapies.

Flow-dependent epigenetic regulation of IGFBP5 expression by H3K27me3 contributes to endothelial anti-inflammatory effects

Rationale: Atherosclerosis is a chronic inflammatory and epigenetic disease that is influenced by different patterns of blood flow. However, the epigenetic mechanism whereby atheroprotective flow controls endothelial gene programming remains elusive. Here, we investigated the possibility that flow alters endothelial gene expression through epigenetic mechanisms. Methods: En face staining and western blot were used to detect protein expression. Real-time PCR was used to determine relative gene expression. RNA-sequencing of human umbilical vein endothelial cells treated with siRNA of enhancer of zeste homolog 2 (EZH2) or laminar flow was used for transcriptional profiling. Results: We found that trimethylation of histone 3 lysine 27 (H3K27me3), a repressive epigenetic mark that orchestrates gene repression, was reduced in laminar flow areas of mouse aorta and flow-treated human endothelial cells. The decrease of H3K27me3 paralleled a reduction in the epigenetic "writer"-EZH2, the catalytic subunit of the polycomb repressive complex 2 (PRC2). Moreover, laminar flow decreased expression of EZH2 via mechanosensitive miR101. Genome-wide transcriptome profiling studies in endothelial cells treated with EZH2 siRNA and flow revealed the upregulation of novel mechanosensitive gene IGFBP5 (insulin-like growth factor-binding protein 5), which is epigenetically silenced by H3K27me3. Functionally, inhibition of H3K27me3 by EZH2 siRNA or GSK126 (a specific EZH2 inhibitor) reduced H3K27me3 levels and monocyte adhesion to endothelial cells. Adenoviral overexpression of IGFBP5 also recapitulated the anti-inflammatory effects of H3K27me3 inhibition. More importantly, we observed EZH2 upregulation, and IGFBP5 downregulation, in advanced atherosclerotic plaques from human patients. Conclusion: Taken together, our findings reveal that atheroprotective flow reduces H3K27me3 as a chromatin-based mechanism to augment the expression of genes that confer an anti-inflammatory response in the endothelium. Our study exemplifies flow-dependent epigenetic regulation of endothelial gene expression, and also suggests that targeting the EZH2/H3K27me3/IGFBP5 pathway may offer novel therapeutics for inflammatory disorders such as atherosclerosis.

Tazemetostat, an EZH2 inhibitor, in relapsed or refractory B-cell non-Hodgkin lymphoma and advanced solid tumours: a first-in-human, open-label, phase 1 study

BACKGROUND

Activating enhancer of zeste homolog 2 (EZH2) mutations or aberrations of the switch/sucrose non-fermentable (SWI/SNF) complex (eg, mutations or deletions of the subunits INI1 or SMARCA4) can lead to aberrant histone methylation, oncogenic transformation, and a proliferative dependency on EZH2 activity. In this first-in-human study, we aimed to investigate the safety, clinical activity, pharmacokinetics, and pharmacodynamics of tazemetostat, a first-in-class selective inhibitor of EZH2.

METHODS

We did an open-label, multicentre, dose-escalation, phase 1 study using a 3 + 3 design with planned cohort expansion at the two highest doses below the maximally tolerated dose. The study was done at two centres in France: Institut Gustave Roussy (Villejuif, Val de Marne) and Institut Bergonié (Bordeaux, Gironde). Eligible patients had relapsed or refractory B-cell non-Hodgkin lymphoma or an advanced solid tumour and were older than 18 years, with Eastern Cooperative Oncology Group performance status of 0 or 1, and adequate end-organ function. Tazemetostat was administered orally from 100 mg twice daily to 1600 mg twice daily in 28-day cycles. The primary endpoint was to establish the maximum tolerated dose or recommended phase 2 dose of tazemetostat, as determined by dose-limiting toxicities, laboratory values, and other safety or pharmacokinetic measures in cycle one according to local investigator assessment. Safety was assessed in patients who received at least one dose of tazemetostat; antitumour activity was assessed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT01897571. The phase 1 part of the study is complete, and phase 2 is ongoing.

FINDINGS

Between June 13, 2013, and Sept 21, 2016, 64 patients (21 with B-cell non-Hodgkin lymphoma, and 43 with advanced solid tumours) received doses of tazemetostat. The most common treatment-related adverse events, regardless of attribution, were asthenia (21 [33%] of 64 treatment-related events), anaemia (nine [14%]), anorexia (four [6%]), muscle spasms (nine [14%]), nausea (13 [20%]), and vomiting (six [9%]), usually grade 1 or 2 in severity. A single dose-limiting toxicity of grade 4 thrombocytopenia was identified at the highest dose of 1600 mg twice daily. No treatment-related deaths occurred; seven (11%) patients had non-treatment-related deaths (one at 200 mg twice daily, four at 400 mg twice daily, and two at 1600 mg twice daily). The recommended phase 2 dose was determined to be 800 mg twice daily. Durable objective responses, including complete responses, were observed in eight (38%) of 21 patients with B-cell non-Hodgkin lymphoma and two (5%) of 43 patients with solid tumours.

INTERPRETATION

Tazemetostat showed a favourable safety profile and antitumour activity in patients with refractory B-cell non-Hodgkin lymphoma and advanced solid tumours, including epithelioid sarcoma. Further clinical investigation of tazemetostat monotherapy is ongoing in phase 2 studies in adults and a phase 1 study for children, which are currently enrolling patients who have B-cell non-Hodgkin lymphoma and INI1-negative or SMARCA4-negative tumours.

FUNDING

Epizyme and Eisai.

EZH2 inhibition sensitizes tamoxifen‑resistant breast cancer cells through cell cycle regulation

Enhancer of zeste homologue 2 (EZH2), a catalytic subunit of polycomb repressive complex 2, is overexpressed in a number of different tumors including breast cancer, and serves important roles in cell cycle regulation, proliferation, apoptosis, tumorigenesis and drug resistance. However, it remains unclear whether EZH2 contributes to tamoxifen resistance in breast cancer. In the present study, the role of EZH2 in tamoxifen resistance in MCF‑7 cells was investigated. EZH2 was overexpressed in MCF‑7 tamoxifen‑resistant (MCF‑7 TamR) cells. EZH2 overexpression decreased the sensitivity of MCF‑7 cells to tamoxifen, and EZH2 knockdown improved the sensitivity of MCF‑7 TamR cells to tamoxifen. Furthermore, EZH2 knockdown induced cell cycle arrest in MCF‑7 TamR cells, accompanied by a decrease in cyclin D1 expression and an increase in p16 expression. EZH2 knockdown reduced p16 gene methylation in MCF‑7 TamR cells. These findings suggested that EZH2 overexpression may contribute to tamoxifen resistance in breast cancer, and EZH2 inhibition may reverse tamoxifen resistance in breast cancer by regulating the cell cycle via the demethylation of the p16 gene. Thus, EZH2 inhibitors may be effective for treating tamoxifen resistance in breast cancer.

MicroRNA‑137 has a suppressive role in liver cancer via targeting EZH2

A variety of microRNAs (miRs) have been demonstrated to be associated with the development and malignant progression of human cancer; however, the regulatory mechanism of miR-137 underlying hepatocellular carcinoma (HCC) growth and metastasis still remains to be fully revealed. In the present study, reverse transcription-quantitative polymerase chain reaction and western blot were used to examine mRNA and protein expression. MTT assay, wound healing assay and Transwell assay were performed to determine cell proliferation, migration and invasion. Luciferase reporter assay was conducted to confirm the targeting relationship. miR-137 was significantly downregulated in HCC tissues compared to adjacent normal tissues. Low expression of miR-137 was significantly associated with lymph node metastasis, vein invasion, advanced clinical stage and poor prognosis in HCC. In addition, miR-137 was also downregulated in several liver cancer cell lines compared with normal liver epithelial cells. Overexpression of miR-137 led to a significant reduction in cell proliferation, migration and invasion of HepG2 cells. Enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) was further identified as a direct target gene of miR-137, and the protein expression of EZH2 was negatively regulated by miR-137 in HepG2 cells. Additionally, EZH2 was significantly upregulated in HCC tissues and liver cancer cell lines. Furthermore, overexpression of EZH2 significantly eliminated the inhibitory effects of miR-137 on the malignant phenotypes of HepG2 cells. Therefore, the findings suggest that miR-137 may have a suppressive role in HCC growth and metastasis via targeting EZH2.

Inhibition of Human Enhancer of Zeste Homolog 2 with Tambjamine Analogs

Combining computational modeling, de novo compound synthesis, and in vitro and cellular assays, we have performed an inhibition study against the enhancer of zeste homolog 2 (EZH2) histone-lysine N-methyltransferase. This enzyme is an important catalytic component of the PRC2 complex whose alterations have been associated with different cancers. We introduce here several tambjamine-inspired derivatives with low micromolar in vitro activity that produce a significant decrease in histone 3 trimethylation levels in cancer cells. We demonstrate binding at the methyl transfer active site, showing, in addition, that the EZH2 isolated crystal structure is capable of being used in molecular screening studies. Altogether, this work provides a successful molecular model that will help in the identification of new specific EZH2 inhibitors and identify a novel class of tambjamine-derived EZH2 inhibitors with promising activities for their use in cancer treatment.

MicroRNA-138 suppresses cell proliferation in laryngeal squamous cell carcinoma via inhibiting EZH2 and PI3K/AKT signaling

MicroRNA (miR)-138 generally has a suppressive role in various human cancer types; however, its role and the underlying mechanisms in laryngeal squamous cell carcinoma (LSCC) have remained to be elucidated. The present study assessed the clinical significance and regulatory mechanisms of miR-138 in LSCC progression. Reverse-transcription quantitative polymerase chain reaction analysis indicated that miR-138 was significantly downregulated in LSCC tissues and cell lines. In addition, the decreased expression of miR-138 was significantly associated with poor differentiation, lymph node metastasis and advanced clinical stage of LSCC. Restoration of miR-138 expression caused a significant decrease in the proliferation of Hep-2 LSCC cells, while knockdown of miR-138 significantly promoted Hep-2 cell proliferation. A luciferase reporter assay further identified enhancer of zeste homologue 2 (EZH2) as a direct target gene of miR-138, and the protein expression of EZH2 was negatively regulated by miR-138 in Hep-2 cells. Furthermore, overexpression of EZH2 eliminated the suppressive effects of miR-138 on Hep-2 cell proliferation via activation of phosphoinositide-3 kinase (PI3K)/AKT signaling. In addition, EZH2 was found to be significantly upregulated in LSCC tissues and to be inversely correlated to the miR-138 levels. The results of the present study demonstrated that miR-138 inhibits the proliferation of LSCC cells, at least partly via targeting EZH2 and inhibiting PI3 K/AKT signaling. The present study highlighted the clinical significance of the miR-138/EZH2 axis in LSCC.

EZH2 upregulation correlates with tumor invasiveness, proliferation, and angiogenesis in human pituitary adenomas

Enhancer of zeste homolog 2 (EZH2) is a critical component of the polycomb repressive complex 2, which epigenetically represses genes involved in tumorigenesis and is highly expressed in tumors. However, no studies have investigated EZH2 expression and its clinical significance in human pituitary adenomas (PAs). Therefore, we examined the expression pattern of EZH2 in PAs and studied the correlations between protein expression and invasiveness, proliferation, angiogenesis, hormone functioning, and some other factors. We measured EZH2 and MMP-14 protein and EZH2 mRNA expression in 62 samples of PAs by immunohistochemistry staining and quantitative real-time polymerase chain reaction and correlated protein expression relative to clinicopathologic features. The immunopositive rate of EZH2 was 88.7% (55/62). The extent of expression was associated with invasiveness, microvessel density, and proliferation (Ki-67 index). Moreover, EZH2 expression correlated with MMP-14 expression. We did not find any correlation between EZH2 overexpression and hormone-secreting function or patient age or sex. The quantitative real-time polymerase chain reaction analysis revealed that the amount of EZH2 mRNA was significantly higher in invasive than in noninvasive adenomas. This is the first report to describe EZH2 overexpression in human PAs, especially invasive adenomas. Thus, EZH2 is a potentially useful diagnostic marker and pharmacotherapeutic target for invasive PAs.

MicroRNA-137 acts as a tumor suppressor in osteosarcoma by targeting enhancer of zeste homolog 2

MicroRNA (miR) are short non-coding RNA that bind to the 3′-untranslational region of their target genes, inhibiting translation and causing mRNA degradation. miR deregulation has been implicated in human cancer; however, the detailed regulatory mechanism of miR-137 in osteosarcoma (OS) remains largely unknown. In the present study, miR-137 and enhancer of zeste homologue 2 (EZH2) mRNA and protein expression levels were analyzed using reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. MTT and transwell assays were performed to evaluate cell viability and invasion capacities and a luciferase reporter gene assay was used to determine the targeting relationship. The results of the current study indicated that miR-137 expression was significantly downregulated in OS tissues and cell lines (P<0.01). Moreover, it was observed that low miR-137 expression levels were significantly associated with lung metastasis and advanced TMN stage (P<0.05), but not associated with age, gender, tumor size, location, serum lactate dehydrogenase or serum alkaline phosphatase. Increasing levels of miR-137 significantly inhibited U2OS cell viability and invasion (P<0.01). By contrast, knockdown of miR-137 markedly increased U2OS cell viability and invasion. EZH2 was identified as a direct target gene of miR-137 in U2OS cells by luciferase reporter assay and EZH2 expression was found to be significantly increased in OS tissues and cell lines (P<0.01). EZH2 was significantly downregulated following miR-137 overexpression (P<0.01), and was upregulated following miR-137 knockdown in U2OS cells. Furthermore, EZH2 overexpression significantly attenuated the suppressive effects of miR-137 on U2OS cell viability and invasion (P<0.01), suggesting that miR-137 inhibits the viability and invasion of OS cells by targeting EZH2. Therefore, the results of the current study suggest that the miR-137/EZH2 axis may be a potential target for novel potential therapeutic strategies to treat OS.

The histone demethylase lysine-specific demethylase-1-mediated epigenetic silence of KLF2 contributes to gastric cancer cell proliferation, migration, and invasion

Gastric cancer is one of the most common malignancies and leading causes of cancer-related death worldwide. An increasing number of evidence has revealed that gastric tumorigenesis is a multistage pathological state, and epigenetic alterations are considered to play critical roles in the etiology of gastric cancer. Lysine-specific demethylase-1, a histone demethylase, has been linked to malignancy in several human cancers and considered to epigenetically regulate many tumor suppressor genes during tumorigenesis and cancer progression. However, its role and underlying targets in gastric cancer are still unclear. In this study, we detected the lysine-specific demethylase-1 expression level in gastric cancer tissues and cell lines and investigated the function and mechanism of lysine-specific demethylase-1 in the gastric cancer. The in vitro analysis shows that knockdown of lysine-specific demethylase-1 significantly inhibits gastric cancer cell proliferation, migration, and invasion and induces cell cycle G1 phase arrest and cell apoptosis. In vivo assays determine that lysine-specific demethylase-1 downregulation represses gastric cancer cell tumorigenesis. Mechanistic investigation reveals that tumor suppressor KLF2 is a key downstream target of lysine-specific demethylase-1 in gastric cancer. These findings indicate that lysine-specific demethylase-1 is an important oncogene in gastric cancer, and lysine-specific demethylase-1-mediated epigenetic repression of KLF2 plays a critical role in gastric cancer development and progression, which supports lysine-specific demethylase-1 as a potential therapeutic target in this disease.

Inhibition of DNA and Histone Methylation by 5-Aza-2'-Deoxycytidine (Decitabine) and 3-Deazaneplanocin-A on Antineoplastic Action and Gene Expression in Myeloid Leukemic Cells

Epigenetic alterations play an important role in the development of acute myeloid leukemia (AML) by silencing of genes that suppress leukemogenesis and differentiation. One of the key epigenetic changes in AML is gene silencing by DNA methylation. The importance of this alteration is illustrated by the induction of remissions in AML by 5-aza-2′-deoxycytidine (5-AZA-CdR, decitabine), a potent inhibitor of DNA methylation. However, most patients induced into remission by 5-AZA-CdR will relapse, suggesting that a second agent should be sought to increase the efficacy of this epigenetic therapy. An interesting candidate for this purpose is 3-deazaneplanocin A (DZNep). This analog inhibits EZH2, a histone methyltransferase that trimethylates lysine 27 histone H3 (H3K27me3), a marker for gene silencing. This second epigenetic silencing mechanism also plays an important role in leukemogenesis as shown in preclinical studies where DZNep exhibits potent inhibition of colony formation by AML cells. We reported previously that 5-AZA-CdR in combination with DZNep exhibits a synergistic antineoplastic action against human HL-60 AML cells and the synergistic activation of several tumor suppressor genes. In this report, we showed that this combination also induced a synergistic activation of apoptosis in HL-60 cells. The synergistic antineoplastic action of 5-AZA-CdR plus DZNep was also observed on a second human myeloid leukemia cell line, AML-3. In addition, 5-AZA-CdR in combination with the specific inhibitors of EZH2, GSK-126, or GSK-343, also exhibited a synergistic antineoplastic action on both HL-60 and AML-3. The combined action of 5-AZA-CdR and DZNep on global gene expression in HL-60 cells was investigated in greater depth using RNA sequencing analysis. We observed that this combination of epigenetic agents exhibited a synergistic activation of hundreds of genes. The synergistic activation of so many genes that suppress malignancy by 5-AZA-CdR plus DZNep suggests that epigenetic gene silencing by DNA and histone methylation plays a major role in leukemogenesis. Targeting DNA and histone methylation is a promising approach that merits clinical investigation for the treatment of AML.

MicroRNA-30d inhibits the migration and invasion of human esophageal squamous cell carcinoma cells via the post‑transcriptional regulation of enhancer of zeste homolog 2

The present study was carried out to investigate the expression pattern, clinical significance and biological functions of microRNA-30d (miR-30d) in esophageal carcinogenesis. Quantitative real-time PCR was performed to detect the expression levels of miR-30d in esophageal squamous cell carcinoma (ESCC) tissues and cell lines. Then, associations between miR-30d expression and various clinicopathological features of patients with ESCC were statistically evaluated. In addition, the effects of miR-30d on the migration and invasion of two human ESCC cell lines transfected with miRNA or co-transfected with miRNA mimics and the expression vector of its target gene were determined. The results revealed that the expression levels of miR-30d were markedly decreased in ESCC tissues and cell lines, comparing with the corresponding normal controls. Notably, reduced expression of miR-30d occurred more frequently in ESCC patients with positive lymph node metastasis, moderate-poor differentiation and advanced tumor-node-metastasis stage than those with negative features. Functionally, enforced expression of miR-30d was found to inhibit cell invasion and migration of the ESCC cell lines. Luciferase reporter assay identified enhancer of zeste homolog 2 (EZH2) as a direct target gene of miR-30d. The expression level of EZH2 mRNA was negatively correlated with the expression of miR-30d in the ESCC tissues. Moreover, the inhibitory effect of miR-30d on ESCC cell motility was reversed by EZH2 overexpression. Collectively, these findings provide convincing evidence that decreased expression of miR-30d may be implicated in esophageal carcinogenesis and progression. We also confirmed miR-30d as a tumor-suppressor which may inhibit cancer cell motility by targeting EZH2, a potential therapeutic target for ESCC.

Epigenetic control of the tumor microenvironment

Stromal cells of the tumor microenvironment have been shown to play important roles in both supporting and limiting cancer growth. The altered phenotype of tumor-associated stromal cells (fibroblasts, immune cells, endothelial cells etc.) is proposed to be mainly due to epigenetic dysregulation of gene expression; however, only limited studies have probed the roles of epigenetic mechanisms in the regulation of stromal cell function. We review recent studies demonstrating how specific epigenetic mechanisms (DNA methylation and histone post-translational modification-based gene expression regulation, and miRNA-mediated translational regulation) drive aspects of stromal cell phenotype, and discuss the implications of these findings for treatment of malignancies. We also summarize the effects of epigenetic mechanism-targeted drugs on stromal cells and discuss the consideration of the microenvironment response in attempts to use these drugs for cancer treatment.