Validation of EZH2 Inhibitor Efficiency in Anaplastic Thyroid Carcinoma Cell Lines

BACKGROUND/AIM

The prognosis of anaplastic thyroid carcinoma (ATC) is poor, and there is currently no established treatment to improve its outcome. We previously reported that enhancer of zeste homolog 2 (EZH2) was highly expressed in ATC, and may be a therapeutic target; however, the effects of EZH2 on ATC growth currently remain unknown.

MATERIALS AND METHODS

We investigated the effects of an EZH2 inhibitor (DZNep) on four ATC cell lines (8305C, KTA1, TTA1 and TTA2). We performed a gene panel analysis of all ATC cell lines to identify differences in DZNep sensitivity between the cell lines. To investigate the effects of DZNep on the recovery of differentiation, we assessed changes in thyroid differentiation markers (TDMs) before and after the DZNep treatment using PCR.

RESULTS

EZH2 was expressed in all ATC cell lines. The cell-reducing effects of DZNep were detected in all ATC cell lines, and were the strongest in KTA1 cells followed by TTA2 cells. The TTA1 and 8305C cell lines, which showed weak cell-reducing effects, had TP53 mutations. No changes in TDMs were observed in any ATC cell line.

CONCLUSION

DZNep, an EZH2 inhibitor, exerted suppressive effects on the growth of ATC cell lines and has potential as a therapeutic strategy; however, its effects may be attenuated in ATC with TP53 mutations.

EZH2 inhibitor DZNep blocks cell proliferation of GCB-DLBCL cells by upregulating p16

Diffuse large B-cell lymphomas (DLBCLs) are phenotypically and genetically heterogeneous. Two main subgroups of DLBCL include germinal center B-cell-like (GCB) and activated B-cell-like (ABC). Molecular profiling can further classify DLBCL into four subtypes: MCD (both CD79B and MYD88 L265P), BN2 (NOTCH2 mutation or BCL6 fusion), N1 (NOTCH1 mutation), or EZB (EZH2 mutation or BCL2 fusion). EZH2 inhibitors were recommended for patients with the EZB subtype of DLBCLs; however, little is known about the therapeutic mechanisms. Our results showed that DZNep arrested G1/S phase of GCB-DLBCL cells and inhibited the cell proliferation in vitro through upregulation of p16 by demethylating its promoter. These results suggest that DZNep may have potential as a novel therapeutic agent for DFLBL therapy. This agent may serve as a novel molecular agent to be applied to GCB DLBCL.

S-adenosylmethionine-dependent methyltransferase inhibitor DZNep blocks transcription and translation of SARS-CoV-2 genome with a low tendency to select for drug-resistant viral variants

We report the in vitro antiviral activity of DZNep (3-Deazaneplanocin A; an inhibitor of S-adenosylmethionine-dependent methyltransferase) against SARS-CoV-2, besides demonstrating its protective efficacy against lethal infection of infectious bronchitis virus (IBV, a member of the Coronaviridae family). DZNep treatment resulted in reduced synthesis of SARS-CoV-2 RNA and proteins without affecting other steps of viral life cycle. We demonstrated that deposition of N6-methyl adenosine (m6A) in SARS-CoV-2 RNA in the infected cells recruits heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), an RNA binding protein which serves as a m6A reader. DZNep inhibited the recruitment of hnRNPA1 at m6A-modified SARS-CoV-2 RNA which eventually suppressed the synthesis of the viral genome. In addition, m6A-marked RNA and hnRNPA1 interaction was also shown to regulate early translation to replication switch of SARS-CoV-2 genome. Furthermore, abrogation of methylation by DZNep also resulted in defective synthesis of the 5’ cap of viral RNA, thereby resulting in its failure to interact with eIF4E (a cap-binding protein), eventually leading to a decreased synthesis of viral proteins. Most importantly, DZNep-resistant mutants could not be observed upon long-term sequential passage of SARS-CoV-2 in cell culture. In summary, we report the novel role of methylation in the life cycle of SARS-CoV-2 and propose that targeting the methylome using DZNep could be of significant therapeutic value against SARS-CoV-2 infection.

DZNep promotes mouse bone defect healing via enhancing both osteogenesis and osteoclastogenesis

Background

Enhancer of zeste homolog 2 (EZH2) is a novel oncogene that can specifically trimethylate the histone H3 lysine 27 (H3K27me3) to transcriptionally inhibit the expression of downstream tumor-suppressing genes. As a small molecular inhibitor of EZH2, 3-Deazaneplanocin (DZNep) has been widely studied due to the role of tumor suppression. With the roles of epigenetic regulation of bone cells emerged in past decades, the property and molecular mechanism of DZNep on enhancing osteogenesis had been reported and attracted a great deal of attention recently. This study aims to elucidate the role of DZNep on EZH2-H3K27me3 axis and downstream factors during both osteoclasts and osteoblasts formation and the therapeutic possibility of DZNep on bone defect healing.

Methods

Bone marrow-derived macrophages (BMMs) cells were cultured, and their responsiveness to DZNep was evaluated by cell counting kit-8, TRAP staining assay, bone resorption assay, podosome actin belt. Bone marrow-derived mesenchymal stem cells (BMSC) were cultured and their responsiveness to DZNep was evaluated by cell counting kit-8, ALP and AR staining assay. The expression of nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), Wnt signaling pathway was determined by qPCR and western blotting. Mouse bone defect models were created, rescued by DZNep injection, and the effectiveness was evaluated by X-ray and micro-CT and histological staining.

Results

Consistent with the previous study that DZNep enhances osteogenesis via Wnt family member 1(Wnt1), Wnt6, and Wnt10a, our results showed that DZNep also promotes osteoblasts differentiation and mineralization through the EZH2-H3K27me3-Wnt4 axis. Furthermore, we identified that DZNep promoted the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation via facilitating the phosphorylation of IKKα/β, IκB, and subsequently NF-κB nuclear translocation, which credit to the EZH2-H3K27me3-Foxc1 axis. More importantly, the enhanced osteogenesis and osteoclastogenesis result in accelerated mice bone defect healing in vivo.

Conclusion

DZNep targeting EZH2-H3K27me3 axis facilitated the healing of mice bone defect via simultaneously enhancing osteoclastic bone resorption and promoting osteoblastic bone formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02670-6.

Abnormal H3K27 histone methylation of RASA1 gene leads to unexplained recurrent spontaneous abortion by regulating Ras-MAPK pathway in trophoblast cells

Some studies suggest that the inactivation of the Ras-MAPK pathway in trophoblast cells can lead to recurrent abortion, but the molecular mechanism underlying the inactivation of this pathway in trophoblast cells is still unclear. This study aimed to explore the relationship between the mechanism of abnormal activation of RASA1, a regulatory protein of the Ras-MAPK pathway, and unexplained recurrent spontaneous abortion. RT-qPCR was used to detect the transcription levels of RASA1 gene. Immunohistochemistry and Western blot were used to detect the expression levels of the RASA1, Raf and MEK proteins. CCK-8, TUNEL and Transwell assays were used to detect the proliferative, apoptotic, and invasive capacities of HTR-8/SVneo cells. ChIP assays were used to detect the enrichment of H3K27me3 in RASA1 gene promoter. Abortion villi experiments showed that the enrichment of H3K27me3 in the RASA1 gene promoter was reduced, and that both RASA1 gene transcription and RASA1 protein expression were increased. Cell experiments confirmed that RASA1 could decrease the phosphorylated Raf and MEK proteins, inhibit the proliferation and invasion ability, and promote the apoptosis ability of HTR-8/SVneo cells. It was also found that the proliferation and invasion ability as well as the Ras-MAPK pathway activity of HTR-8/SVneo cells were inhibited when treated with histone methyltransferase inhibitor DZNep. RASA1 gene was abnormally activated in unexplained recurrent spontaneous abortion villi due to the decreased enrichment of H3K27me3 in the gene promoter. High expression of RASA1 could inhibit the activity of the Ras-MAPK pathway, and thus inhibit the proliferation and invasion ability of trophoblast cells.

DZNep, an inhibitor of the histone methyltransferase EZH2, suppresses hepatic fibrosis through regulating miR-199a-5p/SOCS7 pathway

Background

Hepatic fibrosis is a common response to chronic liver injury. Recently, the role of DZNep (a histone methyltransferase EZH2 inhibitor) in repressing pulmonary and renal fibrosis was verified. However, the potential effect of DZNep on hepatic fibrosis has not been elucidated.

Methods

The hepatic fibrosis model was established in rats treated with CCl4 and in hepatic stellate cells (HSCs) treated with TGF-β1. The liver tissues were stained with H&E and Masson’s trichrome. The expression of EZH2, SOCS7, collagen I, αSMA mRNA and miR-199-5p was assessed using qPCR, immunohistochemical or western blot analysis. A dual-luciferase reporter assay was carried out to validate the regulatory relationship of miR-199a-5p with SOCS7.

Results

The EZH2 level was increased in CCl4-treated rats and in TGF-β1-treated HSCs, whereas DZNep treatment significantly inhibited EZH2 expression. DZNep repressed hepatic fibrosis in vivo and in vitro, as evidenced by the decrease of hepatic fibrosis markers (α-SMA and Collagen I). Moreover, miR-199a-5p expression was repressed by DZNep in TGF-β1-activated HSCs. Notably, downregulation of miR-199a-5p decreased TGF-β1-induced expression of fibrosis markers. SOCS7 was identified as a direct target of miR-199a-5p. The expression of SOCS7 was decreased in TGF-β1-activated HSCs, but DZNep treatment restore d SOCS7 expression. More importantly, SOCS7 knockdown decreased the effect of DZNep on collagen I and α SMA expression in TGF-β1-activated HSCs.

Conclusions

DZNep suppresses hepatic fibrosis through regulating miR-199a-5p/SOCS7 axis, suggesting that DZNep may represent a novel treatment for fibrosis.

The Effect of EZH2 Inhibition through DZNep on Epithelial-Mesenchymal Transition Mechanism

Although the molecular pathogenesis of hepatocellular carcinoma (HCC) is uncertain, it is known that the epithelial-mesenchymal transition (EMT) mechanism and epigenetic changes have an important role. This study was focused on evaluating the relationship of 3-Deazaneplanocin A (DZNep) with the EMT mechanism, which is a histone methyltransferase inhibitor on HCC and is also known as an enhancer of zeste homolog 2 (EZH2) inhibitor. Cell viability of HepG2 cells (HCC cell line) assessed for DZNep over 72 hours with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, colony-forming assay, apoptosis assay, RNA isolation, cDNA synthesis, and real-time PCR (RT-PCR) were performed to see the effect of DZNep on HepG2 cells. DZNep reduced cell proliferation for 72 hours, also significantly reduced colony formation in addition it increased the total apoptosis. DZNep on EZH2, E-cadherin, N-cadherin, and Vimentin (Vim) gene expressions was given different results by either decreasing or increasing the expressions. In this study, we observed a positive effect of DZNep on apoptosis and TIMP3 expression level and decreased colony formation. However, it gave complicated results with the level of gene expression E-cadherin and TIMP2, increase the level of Vim and MMP2 expression. Therefore, we think that further studies are necessary to clarify the role of DZNep.

Chromatin remodeling by the histone methyltransferase EZH2 drives lung pre-malignancy and is a target for cancer prevention

Background

Trimethylation of lysine 27 and dimethylation of lysine 9 of histone-H3 catalyzed by the histone methyltransferases EZH2 and G9a impede gene transcription in cancer. Our human bronchial epithelial (HBEC) pre-malignancy model studied the role of these histone modifications in transformation. Tobacco carcinogen transformed HBEC lines were characterized for cytosine DNA methylation, transcriptome reprogramming, and the effect of inhibiting EZH2 and G9a on the transformed phenotype. The effects of targeting EZH2 and G9a on lung cancer prevention was assessed in the A/J mouse lung tumor model.

Results

Carcinogen exposure induced transformation and DNA methylation of 12–96 genes in the four HBEC transformed (T) lines that was perpetuated in malignant tumors. In contrast, 506 unmethylated genes showed reduced expression in one or more HBECTs with many becoming methylated in tumors. ChIP-on-chip for HBEC2T identified 327 and 143 genes enriched for H3K27me3 and H3K9me2. Treatment of HBEC2T and HBEC13T with DZNep, a lysine methyltransferase inhibitor depleted EZH2, reversed transformation, and induced transcriptional reprogramming. The EZH2 small molecule inhibitor EPZ6438 also affected transformation and expression in HBEC2T, while a G9a inhibitor, UNC0642 was ineffective. Genetic knock down of EZH2 dramatically reduced carcinogen-induced transformation of HBEC2. Only DZNep treatment prevented progression of hyperplasia to adenomas in the NNK mouse lung tumor model through reducing EZH2 and affecting the expression of genes regulating cell growth and invasion.

Conclusion

These studies demonstrate a critical role for EZH2 catalyzed histone modifications for premalignancy and its potential as a target for chemoprevention of lung carcinogenesis.

Histone Methylation Inhibitor DZNep Ameliorated the Renal Ischemia-Reperfusion Injury via Inhibiting TIM-1 Mediated T Cell Activation

Renal ischemia-reperfusion injury (IRI) after renal transplantation often leads to the loss of kidney graft function. However, there is still a lack of efficient regimens to prevent or alleviate renal IRI. Our study focused on the renoprotective effect of 3-Deazaneplanocin A (DZNep), which is a histone methylation inhibitor. We found that DZNep significantly alleviated renal IRI by suppressing nuclear factor kappa-B (NF-κB), thus inhibiting the expression of inflammatory factors in renal tubular epithelial cells in vivo or in vitro. After treatment with DZNep, T cell activation was impaired in the spleen and kidney, which correlated with the downregulated expression of T-cell immunoglobulin mucin (TIM)-1 on T cells and TIM-4 in macrophages. In addition, pretreatment with DZNep was not sufficient to protect the kidney, while administration of DZNep from before to after surgery significantly ameliorated IRI. Our findings suggest that DZNep can be a novel strategy for preventing renal IRI following kidney transplantation.

Small Molecules Targeting H3K9 Methylation Prevent Silencing of Reactivated FMR1 Alleles in Fragile X Syndrome Patient Derived Cells

In fragile X syndrome (FXS), expansion of a CGG repeat tract in the 5′-untranslated region of the FMR1 gene to >200 repeats causes transcriptional silencing by inducing heterochromatin formation. Understanding the mechanism of FMR1 silencing is important as gene reactivation is a potential treatment approach for FXS. To date, only the DNA demethylating drug 5-azadeoxycytidine (AZA) has proved effective at gene reactivation; however, this drug is toxic. The repressive H3K9 methylation mark is enriched on the FMR1 gene in FXS patient cells and is thus a potential druggable target. However, its contribution to the silencing process is unclear. Here, we studied the effect of small molecule inhibitors of H3K9 methylation on FMR1 expression in FXS patient cells. Chaetocin showed a small effect on FMR1 gene reactivation and a synergistic effect on FMR1 mRNA levels when used in combination with AZA. Additionally, chaetocin, BIX01294 and 3-Deazaneplanocin A (DZNep) were able to significantly delay the re-silencing of AZA-reactivated FMR1 alleles. These data are consistent with the idea that H3K9 methylation precedes DNA methylation and that removal of DNA methylation is necessary to see the optimal effect of histone methyl-transferase (HMT) inhibitors on FMR1 gene expression. Nonetheless, our data also show that drugs targeting repressive H3K9 methylation marks are able to produce sustained reactivation of the FMR1 gene after a single dose of AZA.

S-adenosylhomocysteine (AdoHcy)-dependent methyltransferase inhibitor DZNep overcomes breast cancer tamoxifen resistance via induction of NSD2 degradation and suppression of NSD2-driven redox homeostasis

Endocrine therapies (e.g. tamoxifen and aromatase inhibitors) targeting estrogen action are effective in decreasing mortality of breast cancer. However, their efficacy is limited by intrinsic and acquired resistance. Our previous study demonstrated that overexpression of a histone methyltransferase NSD2 drives tamoxifen resistance in breast cancer cells and that NSD2 is a potential biomarker of tamoxifen resistant breast cancer. Here, we found that DZNep, an indirect inhibitor of histone methyltransferases, potently induces the degradation of NSD2 protein and inhibits the expression of NSD2 target genes (HK2, G6PD, GLUT1 and TIGAR) involved in the pentose phosphate pathway (PPP). DZNep treatment of tamoxifen-resistant breast cancer cells and xenograft tumors also strongly inhibits tumor growth and the cancer cell survival through decreasing cell production of NADPH and glutathione (GSH) and invoking elevated ROS to cause apoptosis. These findings suggest that DZNep-like agents can be developed to target NSD2 histone methyltransferase for effective treatment of tamoxifen-resistant breast cancer.

Inhibition of juvenile hormone synthesis in mosquitoes by the methylation inhibitor 3-deazaneplanocin A (DZNep)

Juvenile hormone (JH), synthesized by the corpora allata (CA), controls development and reproduction in mosquitoes through its action on thousands of JH-responsive genes. These JH-dependent processes can be studied using tools that increase or decrease JH titers in vitro and in vivo. Juvenile hormone acid methyl transferase (JHAMT) is a critical JH biosynthetic enzyme. JHAMT utilizes the methyl donor S-adenosyl-methionine (SAM) to methylate farnesoic acid (FA) into methyl farnesoate (MF), releasing the product S-adenosyl-L-homocysteine (AdoHcy), which inhibits JHAMT. S-adenosyl-homocysteine hydrolase (SAHH) catalyzes AdoHcy hydrolysis to adenosine and homocysteine, alleviating AdoHcy inhibition of JHAMT. 3-deazaneplanocin A (DZNep), an analog of adenosine, is an inhibitor of SAHH, and an epigenetic drug for cancer therapy. We tested the effect of DZNep on in vitro JH synthesis by CA of mosquitoes. DZNep inhibited JH synthesis in a dose-response fashion. Addition of MF, but not of FA relieved the inhibition, demonstrating a direct effect on JHAMT. In vivo experiments, with addition of DZNep to the sugar ingested by mosquitoes, resulted in a dose-response decrease in JH synthesis and JH hemolymphatic titers, as well as expression of early trypsin, a JH-dependent gene. Our studies suggest that DZNep can be employed to lower JH synthesis and titer in experiments evaluating JH-controlled processes in mosquitoes.

A Compound AC1Q3QWB Selectively Disrupts HOTAIR-Mediated Recruitment of PRC2 and Enhances Cancer Therapy of DZNep

Over 20% of cancer 'driver' genes encode chromatin regulators. Long noncoding RNAs (lincRNAs), which are dysregulated in various cancers, play a critical role in chromatin dynamics and gene regulation by interacting with key epigenetic regulators. It has been previously reported that the lincRNA HOTAIR mediates recruitment of polycomb repressive complex 2 (PRC2) leading to aberrant transcriptional silencing of tumor suppressor genes in glioma and breast cancer. Thus, lincRNA HOTAIR can serve as a promising therapeutic target. Herein, we identified a small-molecule compound AC1Q3QWB (AQB) as a selective and efficient disruptor of HOTAIR-EZH2 interaction, resulting in blocking of PRC2 recruitment and increasing tumor suppressors expression.

Methods: Molecular docking and high-throughput screening were performed to identify the small compound, AQB. RIP and ChIRP assays were carried to assess the selective interference of AQB with the HOTAIR-EZH2 interaction. The effects of AQB on tumor malignancy were evaluated in a variety of cancer cell lines and orthotopic breast cancer models. The combination therapy of AQB and 3-Deazaneplanocin A (DZNep), an inhibitor of the histone methyltransferase EZH2 was used in vitro and in orthotopic breast cancer and glioblastoma patient-derived xenograft (PDX) models.

Results: Tumor cells highly expressing HOTAIR and EZH2 were sensitive to AQB. APC2, as one of the target genes, was significantly up-regulated by AQB and led to degradation of β-catenin resulting in suppression of Wnt/β-catenin signaling which may contribute to inhibition of tumor growth and metastasis in vitro and in orthotopic breast cancer models. Remarkably, AQB enhanced the toxicity of DZNep in vitro. In orthotopic breast cancer and glioblastoma patient-derived xenografts (PDX) models, the combination of low doses of AQB and DZNep realized much better killing than DZNep treatment alone.

Conclusion: AQB is a HOTAIR-EZH2 inhibitor, which blocks PRC2 recruitment and has great potential as an effective agent for targeted cancer therapy.

EZH2 inhibitor DZNep modulates microglial activation and protects against ischaemic brain injury after experimental stroke

Enhancer of zeste homolog-2 (EZH2), a histone methyltransferase, has been recognized to play a pivotal role in regulating the immune response in various diseases. However, its role in the inflammatory response induced by ischaemic stroke remains to be further investigated. The aim of this study was to determine the role of EZH2 in microglia-associated inflammation in ischaemic stroke and to further detect the effects of the EZH2 inhibitor, 3-deazaadenosine A (DZNep), in ischaemic brain injury. Here, we found that both in vivo ischemic/reperfusion (I/R) injury and in vitro oxygen-glucose deprivation (OGD) treatment induced a marked upregulation of EZH2 in microglia. The administration of the EZH2 inhibitor DZNep improved behavioural performance and reduced the infarct volume in mice after experimental stroke. Furthermore, we showed that DZNep blocked pro-inflammatory (CD86⁺) microglial activation and triggered anti-inflammatory (CD206⁺) microglial polarization in experimental stroke. Pro-inflammatory cytokines such as IL-1β, IL-6, TNF-α and CXCL10 were also significantly downregulated by DZNep. In addition, it was found that DZNep blocked the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in microglia, which was increased by I/R injury and OGD. Collectively, we demonstrated that EZH2 is implicated in regulating microglial activation and exacerbates neurological deficits after ischaemic stroke, probably via activating STAT3, and that the EZH2 inhibitor DZNep can exert neuroprotective effects after ischaemic stroke.

Aberrant Epigenetic Regulation in Head and Neck Cancer Due to Distinct EZH2 Overexpression and DNA Hypermethylation

Enhancer of Zeste homologue 2 (EZH2) overexpression is associated with tumor proliferation, metastasis, and poor prognosis. Targeting and inhibition of EZH2 is a potentially effective therapeutic strategy for head and neck squamous cell carcinoma (HNSCC). We analyzed EZH2 mRNA expression in a well-characterized dataset of 230 (110 original and 120 validation cohorts) human head and neck cancer samples. This study aimed to investigate the effects of inhibiting EZH2, either via RNA interference or via pharmacotherapy, on HNSCC growth. EZH2 upregulation was significantly correlated with recurrence (p < 0.001) and the methylation index of tumor suppressor genes (p < 0.05). DNMT3A was significantly upregulated upon EZH2 upregulation (p = 0.043). Univariate analysis revealed that EZH2 upregulation was associated with poor disease-free survival (log-rank test, p < 0.001). In multivariate analysis, EZH2 upregulation was evaluated as a significant independent prognostic factor of disease-free survival (hazard ratio: 2.085, 95% confidence interval: 1.390–3.127; p < 0.001). Cells treated with RNA interference and DZNep, an EZH2 inhibitor, showed the most dramatic changes in expression, accompanied with a reduction in the growth and survival of FaDu cells. These findings suggest that EZH2 upregulation is correlated with tumor aggressiveness and adverse patient outcomes in HNSCC. Evaluation of EZH2 expression might help predict the prognosis of HNSCC patients.

DZNep represses Bcl-2 expression and modulates apoptosis sensitivity in response to Nutlin-3a

MDM2 antagonists stabilize and activate wild-type p53, and histone methyltransferase (HMT) inhibitors reduce methylation on histone lysines and arginines. Both MDM2 antagonists and HMT inhibitors are being developed as cancer therapeutics. Wild-type p53 expressing HCT116 colon cancer cells were resistant to apoptosis in response to the MDM2 antagonist Nutlin-3a. However, co-treatment with the HMT inhibitor DZNep sensitized the cells to Nutlin-3a-induced apoptosis. This sensitization resulted from reduced activity of the Bcl-2 gene promoter and a reduction in Bcl-2 mRNA and protein. Surprisingly, DZNep reduced Bcl-2 expression in other colon cancer cell lines (RKO, SW48, and LoVo) but failed to sensitize them to Nutlin-3a. We found these cell lines express elevated levels of Bcl-2 or other Bcl-2-family proteins, including Bcl-xL, Mcl-1, and Bcl-w. Knockdown of Mcl-1 and/or treatment with specific or pan Bcl-2-family inhibitors (BH3 mimetics) sensitized RKO, SW48, and LoVo cells to apoptosis by Nutlin-3a. The results demonstrate 1) DZNep represses the Bcl-2 gene promoter and affects apoptosis sensitivity by reducing Bcl-2 protein expression, and 2) elevated expression of pro-survival Bcl-2 family members protects colon cancer cells from Nutlin-3a-induced apoptosis. Targeting Bcl-2 proteins via DZNep or BH3 mimetics could increase the therapeutic potential of MDM2-antagonists like Nutlin-3a in colon cancer.

Emerging role of SETDB1 as a therapeutic target

INTRODUCTION

Epigenetic changes lead to aberrant gene expression in cancer. SETDB1, a histone lysine methyltransferase plays an important role in methylation and gene silencing. Aberrant histone methylation at H3K9 by SETDB1 promotes silencing of tumor suppressor genes and thus contributes to carcinogenesis. Recent studies indicate that SETDB1 is abnormally expressed in various human cancer conditions which contributed to enhanced tumor growth and metastasis. Hence, SETDB1 appears to be a promising epigenetic target for therapeutic intervention. Areas covered: In this article, the structural features, localization and functions of SETDB1 are reviewed. Also, an overview of the role of SETDB1 in cancer and other disease mechanisms, the currently studied inhibitors for SETDB1 are mentioned. Expert opinion: Silencing of tumor suppressor genes due to excessive trimethylation at H3K9 by amplified SETDB1 levels is found in various cancerous conditions. Since epigenetic changes are reversible, SETDB1 holds promise as an important therapeutic target for cancer. Therefore, a better understanding of the role of SETDB1 and its interaction with various proteins in cancer-related mechanisms along with therapeutic interventions specific for SETDB1 may improve targeted cancer therapy.

Inhibition of histone methyltransferase EZH2 ameliorates early acute renal allograft rejection in rats

BACKGROUND

Although histone methyltransferases EZH2 has been proved to have significant regulatory effect on the immune rejection after hematopoietic stem cell transplantation, its role in solid-organ transplantation remains uncovered. In this study, we investigate whether histone methylation regulation can impact renal allograft rejection in rat models.

RESULTS

Allogeneic rat renal transplantation model (Wistar to Lewis) was established, and the recipients were administrated with EZH2 inhibitor DZNep after transplantation. Renal allografts and peripheral blood were collected on day 5 after transplantation for histological examination and mechanism investigation. We found that inhibition of EZH2 by DZNep after transplantation significantly ameliorated acute rejection (AR), with decreased histological injury and reduced inflammatory infiltration in renal allografts. Attenuation of AR was due to the prohibited activation of alloreactive T cells, the subsequent impaired production of inflammatory cytokines, and also the elevated apoptosis of alloreactive T cells in both renal allografts and periphery. However, inhibition of EZH2 did not increase the regulatory T cells during the AR.

CONCLUSIONS

Disruption of EZH2 by DZNep suppressed the immune responses of alloreactive T cells and ameliorated AR of renal allografts. This suggests a therapeutic potential of targeting histone methyltransferases EZH2 in treating allograft rejection after solid organ transplantation.

Downregulation of Enhancer of Zeste Homolog 2 (EZH2) is essential for the Induction of Autophagy and Apoptosis in Colorectal Cancer Cells

Increasing evidence indicates that elevated expression of enhancer of zeste homolog 2 gene (EZH2) in many human malignant tumors acts a significant role in the oncogenic process. However, the underlying molecular mechanism is still unclarified. It is evident that apoptosis and autophagy of tumor cells is crucial for the tumorigenesis and progression of cancer, however, the exact role of EZH2 plays in apoptosis and autophagy has not been fully elucidated in colorectal cancer (CRC). Our previous study found that the expression level of EZH2 was higher in CRC tumor tissues than in the paired normal tissues using immunohistochemical analysis. We also recently found that the autophagy-related gene-related protein Ambra1 plays an important role in the autophagy pathway in CRC cells. In this study, mRNA and protein expression of EZH2 in four CRC cell lines were tested at first and RKO and HCT116 cells showed the highest levels among them. Here we transfected with EZH2-shRNA, or added DZNep (an EZH2 inhibitor) to RKO and HCT116 cells in order to detect the effect of EZH2 on autophagy via determining the change of the protein expression of LC3 and Ambra1. The outcome indicated an obvious decrease of autophagy level in cells transfected with EZH2-shRNA or DZNep. We also found the apoptotic rate of cells was elevated significantly after downregulation of EZH2. In addition, compared to control group, CRC cells transfected with EZH2-shRNA or added DZNep revealed a significantly increased G1 cell cycle rate and an obvious decrease in the G2 cell cycle rate. Further analysis showed that knockdown of EZH2 induced cell-cycle arrest in CRC cells. Meanwhile, downregulation of EZH2 in CRC cells induces autophagy and apoptosis. Taken together, our results suggest that EZH2 plays a critical role in autophagy and apoptosis in the progression of CRC, which potentially facilitates the development of an ideal strategy for combating colorectal cancer.

3-Deazaneplanocin A May Directly Target Putative Cancer Stem Cells in Biliary Tract Cancer

BACKGROUND/AIM

Polycomb repressive complex 2 (PRC2), an epigenetic master regulator, contributes to progression and development of biliary tract cancer (BTC). The present study investigated the effects of the PRC2 inhibitor 3-deazaneplanocin A (DZNep) on BTC cell lines.

MATERIALS AND METHODS

In vitro effects of DZNep treatment were analyzed for cell viability, gene expression and functional characteristics of cancer stem cell (CSC).

RESULTS

DZNep treatment caused a cell line- and dose-dependent decrease in viability. In the EGI-1 cell line, a direct cytotoxic effect was accompanied by mRNA down-regulation of the PRC2 core components, cyclins as well as of CSC-related genes. Furthermore, DZNep affected putative CSCs by reduction of sphere formation and aldehyde dehydrogenase-1-positive cells. The stem cell characteristics of these subpopulations were verified by real-time polymerase chain reaction analysis.

CONCLUSION

Taken together, our results show that DZNep might be a promising pharmacological agent for future therapies regarding BTC.

DZNep inhibits the proliferation of colon cancer HCT116 cells by inducing senescence and apoptosis

EZH2 is over-expressed in human colon cancer and is closely associated with tumor proliferation, metastasis and poor prognosis. Targeting and inhibiting EZH2 may be an effective therapeutic strategy for colon cancer. 3-Deazaneplanocin A (DZNep), as an EZH2 inhibitor, can suppress cancer cell growth. However, the anti-cancer role of DZNep in colon cancer cells has been rarely studied. In this study, we demonstrate that DZNep can inhibit the growth and survival of colon cancer HCT116 cells by inducing cellular senescence and apoptosis. The study provides a novel view of anti-cancer mechanisms of DZNep in human colon cancer cells.

Enhancer of zeste homolog 2 (EZH2) promotes tumour cell migration and invasion via epigenetic repression of E-cadherin in renal cell carcinoma

OBJECTIVE

To investigate the molecular mechanism and clinical significance for an oncogenic role of enhancer of zeste homolog 2 (EZH2) in renal cell carcinoma (RCC).

MATERIALS AND METHODS

Immunohistochemistry analyses of EZH2, histone H3 trimethyl Lys27 (H3K27me3) and E-cadherin were performed in tumour tissue samples from 257 patients with RCC. Regulatory effects of EZH2 on E-cadherin expression were examined by quantitative real-time polymerase chain reaction, Western blot, chromatin immunoprecipitation assay and immunohistochemical staining. Migration and invasion assays were performed in RCC cell lines. Tumour xenograft experiments with RCC cells were carried out in nude mice.

RESULTS

EZH2 promoted migration and invasion in RCC cell lines. Silencing EZH2 with short-hairpin EZH2 (shEZH2) or 3-deazaneplanocin A (DZNep) inhibited migration and invasion (P < 0.001), up-regulated the expression of E-cadherin in vitro, inhibited tumour growth, and prolonged survival in vivo (P = 0.022). EZH2 expression accompanied with E-cadherin repression was associated with advanced disease stage (P = 0.004) and poor overall (P < 0.001) and disease-free survival (P < 0.001).

CONCLUSION

EZH2 may contribute to RCC progression and is a potential therapeutic target for advanced RCC.

The specific alteration of histone methylation profiles by DZNep during early zebrafish development

Early embryo development constitutes a unique opportunity to study acquisition of epigenetic marks, including histone methylation. This study investigates the in vivo function and specificity of 3-deazaneplanocin A (DZNep), a promising anti-cancer drug that targets polycomb complex genes. One- to two-cell stage embryos were cultured with DZNep, and subsequently evaluated at the post-mid blastula transition stage for H3K27me3, H3K4me3 and H3K9me3 occupancy and enrichment at promoters using ChIP-chip microarrays. DZNep affected promoter enrichment of H3K27me3 and H3K9me3, whereas H3K4me3 remained stable. Interestingly, DZNep induced a loss of H3K27me3 and H3K9me3 from a substantial number of promoters but did not prevent de novo acquisition of these marks on others, indicating gene-specific targeting of its action. Loss/gain of H3K27me3 on promoters did not result in changes in gene expression levels until 24h post-fertilization. In contrast, genes gaining H3K9me3 displayed strong and constant down-regulation upon DZNep treatment. H3K9me3 enrichment on these gene promoters was observed not only in the proximal area as expected, but also over the transcription start site. Altered H3K9me3 profiles were associated with severe neuronal and cranial phenotypes at day 4-5 post-fertilization. Thus, DZNep was shown to affect enrichment patterns of H3K27me3 and H3K9me3 at promoters in a gene-specific manner.

3-Deazaneplanocin A (DZNep), an inhibitor of S-adenosylmethionine-dependent methyltransferase, promotes erythroid differentiation

EZH2, a core component of polycomb repressive complex 2 (PRC2), plays a role in transcriptional repression through histone H3 Lys-27 trimethylation and is involved in various biological processes, including hematopoiesis. It is well known that 3-deazaneplanocin A (DZNep), an inhibitor of S-adenosylmethionine-dependent methyltransferase that targets the degradation of EZH2, preferentially induces apoptosis in various hematological malignancies, suggesting that EZH2 may be a new target for epigenetic treatment. Because PRC2 participates in epigenetic silencing of a subset of GATA-1 target genes during erythroid differentiation, inhibition of EZH2 may influence erythropoiesis. To explore this possibility, we evaluated the impact of DZNep on erythropoiesis. DZNep treatment significantly induced erythroid differentiation of K562 cells, as assessed by benzidine staining and quantitative RT-PCR analysis for representative erythroid-related genes, including globins. When we evaluated the effects of DZNep in human primary erythroblasts derived from cord blood CD34-positive cells, the treatment significantly induced erythroid-related genes, as observed in K562 cells, suggesting that DZNep induces erythroid differentiation. Unexpectedly, siRNA-mediated EZH2 knockdown had no significant effect on the expression of erythroid-related genes. Transcriptional profiling of DZNep-treated K562 cells revealed marked up-regulation of SLC4A1 and EPB42, previously reported as representative targets of the transcriptional corepressor ETO2. In addition, DZNep treatment reduced the protein level of ETO2. These data suggest that erythroid differentiation by DZNep may not be directly related to EZH2 inhibition but may be partly associated with reduced protein level of hematopoietic corepressor ETO2. These data provide a better understanding of the mechanism of action of DZNep, which may be exploited for therapeutic applications for hematological diseases, including anemia.

DZNep, inhibitor of S-adenosylhomocysteine hydrolase, down-regulates expression of SETDB1 H3K9me3 HMTase in human lung cancer cells

3-Deazaneplanocin A (DZNep), an epigenetic anticancer drug, leads to the indirect suppression of S-adenosyl methionine-dependent cellular methylations by inhibiting S-adenosyl homocystein (AdoHcy) hydrolase. Although it is well known that DZNep targets the degradation of EZH2 protein, H3K27me3 HMTase, there are still uncertainties about the regulation of other types of HMTases during cell death. In this study, we describe that SETDB1 gene expression was regulated by DZNep treatment in human lung cancer cells. We confirm that DZNep induced growth inhibition and increased the dead cell population of lung cancer cells. DZNep treatment affected histone methylations, including H3K27me3 and H3K9me3, but not H3K4me3. Reduced levels of H3K27me3 and H3K9me3 were related with the decreased EZH2 and SETDB1 proteins. Real time PCR analysis showed that SETDB1 gene expression was decreased by DZNep treatment, but no effect was observed for EZH2 gene expression. We cloned the promoter region of SETDB1 and SUV39H1 genes, and performed luciferase assays. The promoter activity of SETDB1 gene was down regulated by DZNep treatment, whereas no effect on SUV39H1 promoter activity was observed. In conclusion, we suggest that DZNep regulates not only on H3K27me3 HMTase EZH2, but also H3K9 HMTase SETDB1 gene expression at the transcription level, implicating that the mechanism of action of DZNep targets multiple HMTases during the death of lung cancer cells.