EZH2 regulates the expression of p16 in the nasopharyngeal cancer cells

EZH2-mediated development of therapeutic resistance in cancer

Enhancer of zeste homolog 2 (EZH2) regulates gene expression and plays a definite role in cell proliferation, apoptosis, and senescence. Overexpression of EZH2 has been found in various human malignancies, including prostate, breast, and ovarian cancers, and is associated with increased metastasis and poor prognosis. EZH2 catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) as a canonical role in a PRC2-dependent manner. This mechanism silences various tumor suppressor genes through EZH2-mediated histone lysine methyltransferase activity. As a non-canonical role, EZH2 partners with other signaling molecules to undergo post-translational modification to orchestrate its function as a co-activator playing a critical role in cancer progression. Dysregulation of EZH2 has also been associated with therapeutic resistance in cancer cells. Given the role of EZH2 in promoting carcinogenesis and therapy resistance, both canonical and non-canonical EZH2 inhibitors have been used to combat multiple cancer types. Moreover, combining EZH2 inhibitors with other therapeutic modalities have shown to enhance the therapeutic efficacy and overcome potential resistance mechanisms in these cancerous cells. Therefore, targeting EZH2 through canonical and non-canonical modes appears to be a promising therapeutic strategy to enhance efficacy and overcome resistance in multiple cancers.

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.

Evaluation of Tazemetostat as a Therapeutically Relevant Substance in Biliary Tract Cancer

Biliary tract cancer (BTC) is a gastrointestinal malignancy associated with a poor survival rate. Current therapies encompass palliative and chemotherapeutic treatment as well as radiation therapy, which results in a median survival of only one year due to standard therapeutic ineffectiveness or resistance. Tazemetostat is an FDA-approved inhibitor of enhancer of Zeste homolog 2 (EZH2), a methyltransferase involved in BTC tumorigenesis via trimethylation of histone 3 at lysine 27 (H3K27me3), an epigenetic mark associated with silencing of tumor suppressor genes. Up to now, there are no data available regarding tazemetostat as a possible treatment option against BTC. Therefore, the aim of our study is a first-time investigation of tazemetostat as a potential anti-BTC substance in vitro. In this study, we demonstrate that tazemetostat affects cell viability and the clonogenic growth of BTC cells in a cell line-dependent manner. Furthermore, we found a strong epigenetic effect at low concentrations of tazemetostat, which was independent of the cytotoxic effect. We also observed in one BTC cell line that tazemetostat increases the mRNA levels and protein expression of the tumor suppressor gene Fructose-1,6-bisphosphatase 1 (FBP1). Interestingly, the observed cytotoxic and epigenetic effects were independent of the mutation status of EZH2. To conclude, our study shows that tazemetostat is a potential anti-tumorigenic substance in BTC with a strong epigenetic effect.

EZH2 W113C is a gain-of-function mutation in B cell lymphoma enabling both PRC2 methyltransferase activation and tazemetostat resistance

Polycomb Repressive Complex2 (PRC2) suppresses gene transcription by methylating lysine 27 of histone H3 (H3K27) and plays critical roles in embryonic development. Among the core PRC2 subunits, EZH2 is the catalytic subunit and EED allosterically activates EZH2 upon binding trimethylated H3K27 (H3K27me3). Activating mutations on Y641, A677, and A687 within the enzymatic SET domain of EZH2 have been associated with enhanced H3K27me3 and tumorigenicity of many cancers including B-cell lymphoma and melanoma. To tackle the critical residues outside the EZH2 SET domain, we examined EZH2 mutations in lymphoma from cancer genome databases and identified a novel gain-of-function (GoF) mutation W113C, which increases H3K27me3 in vitro and in vivo and promotes CDKN2A silencing to a similar level as the EZH2 Y641F. Different from other GoF mutations, this mutation is located in the SAL motif at the EZH2 N-terminus, which stabilizes the SET domain and facilitates substrate binding. This may explain how the W113C mutation increases PRC2 activity. Tazemetostat is an FDA-approved EZH2 binding inhibitor for follicular lymphoma treatment. Intriguingly, the W113C mutation leads to tazemetostat-resistance in cell and in vivo in both H3K27 methylation and tumor proliferation. Another class of allosteric PRC2 inhibitor binding EED overcomes the resistance, effectively decreases H3K27me3, and blocks tumor proliferation in cells expressing EZH2 W113C. As this mutation is originally identified from lymphoma samples, our results demonstrated its activating characteristic and the deleterious consequence, provide insights on PRC2 regulation, and support the continued exploration of treatment optimization for lymphoma patients.

The role of EZH2 as a potential therapeutic target in retinoblastoma

Enhancer of zeste homolog 2 (EZH2) has been reported selectively expressed in postnatal human retinoblastoma (RB). While, the contribution of EZH2 in progression of RB and its clinical importance has not been clarified. Here, immunohistochemistry (IHC) was performed on tumor specimens from 53 RB patients. UNC1999 and GSK503, inhibitors targeting EZH2, were incubated with human RB cell line WERI-Rb-1 and Y79 to assess the role and mechanism of EZH2 in RB proliferation, metastasis and tumor glycolysis. Administration of UNC1999 in subcutaneous tumor model of RB was conducted. The results showed that highly expressed EZH2 in RB tissues was significantly associated with the poor overall survival. UNC1999 and GSK503 inhibited proliferation, migration, invasion and tumor glycolysis of RB. Results in mouse xenograft model confirmed the inhibitory effect of UNC1999 on tumor growth of RB and the regulation effect of EZH2 to STAT3/FoxO1 signaling pathway. Therefore, EZH2 is rewarding to study as a potential target for anti-RB treatment.

METTL3 Accelerates Breast Cancer Progression via Regulating EZH2 m6A Modification

We aimed to investigate the bio-functions of METTL3 in promoting breast cancer (BCa) progression via regulating N6-methyladenosine (m6A) modification of EZH2 mRNA. METTL3 levels in 48 cases of BCa and matched paracancerous tissues were detected. In the meantime, METTL3 in BCa patients with different staging or lymphatic metastasis states were examined. Prognosis of the BCa patients was analyzed using Kaplan-Meier estimator. Protein levels of EMT-associated genes and invasive and migratory abilities were evaluated. The binding relationship between EZH2 and METTL3 was analyzed via RIP. Besides, m6A modification of EZH2 mRNA was explored. E-Cadherin level in MCF-7 cells with EZH2 knockdown was tested. Subsequently, ChIP was done to verify the interaction between E-cadherin and EZH2. Regulatory effects of METTL3/E-cadherin axis on EMT and metastasis of BCa were finally determined. METTL3 was upregulated in BCa tissues compared to paracancerous ones. METTL3 was especially higher in T3-T4 BCa or those with lymphatic metastasis. BCa patients expressing high level of METTL3 experienced worse survival. METTL3 was identically upregulated in BCa cell lines. Knockdown of METTL3 in MCF-7 cells attenuated EMT and metastatic abilities. Protein level of EZH2 was downregulated after knockdown of METTL3 in MCF-7 cells, while its mRNA level was not influenced by METTL3. Furthermore, METTL3 was confirmed to interact with EZH2, and m6A modification existed in EZH2 mRNA. Knockdown of EZH2 greatly upregulated mRNA level of E-cadherin, and later, ChIP assay confirmed the interaction between EZH2 and E-cadherin. E-Cadherin could abolish the effects of METTL3 on BCa metastasis and epithelial-mesenchymal transition. METTL3 is upregulated in BCa. It could regulate the protein level of EZH2 through m6A modification to promote EMT and metastasis in BCa cells, thereafter aggravating the progression of BCa.

Induction of senescence-associated secretory phenotype underlies the therapeutic efficacy of PRC2 inhibition in cancer

The methyltransferase Polycomb Repressive Complex 2 (PRC2), composed of EZH2, SUZ12, and EED subunits, is associated with transcriptional repression via tri-methylation of histone H3 on lysine 27 residue (H3K27me3). PRC2 is a valid drug target, as the EZH2 gain-of-function mutations identified in patient samples drive tumorigenesis. PRC2 inhibitors have been discovered and demonstrated anti-cancer efficacy in clinic. However, their pharmacological mechanisms are poorly understood. MAK683 is a potent EED inhibitor in clinical development. Focusing on MAK683-sensitive tumors with SMARCB1 or ARID1A loss, we identified a group of PRC2 target genes with high H3K27me3 signal through epigenomic and transcriptomic analysis. Multiple senescence-associated secretory phenotype (SASP) genes, such as GATA4, MMP2/10, ITGA2 and GBP1, are in this group besides previously identified CDKN2A/p16. Upon PRC2 inhibition, the de-repression of SASP genes is detected in multiple sensitive models and contributes to decreased Ki67+, extracellular matrix (ECM) reorganization, senescence associated inflammation and tumor regression even in CDKN2A/p16 knockout tumor. And the combination of PRC2 inhibitor and CDK4/6 inhibitor leads to better effect. The genes potential regulated by PRC2 in neuroblastoma samples exhibited significant enrichment of ECM and senescence associated inflammation, supporting the clinical relevance of our results. Altogether, our results unravel the pharmacological mechanism of PRC2 inhibitors and propose a combination strategy for MAK683 and other PRC2 drugs.

The prognostic value of m6A-related LncRNAs in patients with HNSCC: bioinformatics analysis of TCGA database

N6-methyladenosine (m6A) modifications play an essential role in tumorigenesis. These modifications modulate RNAs, including mRNAs and lncRNAs. However, the prognostic role of m6A-related lncRNAs in head and neck squamous cell carcinoma (HNSCC) is poorly understood. Based on LASSO Cox regression, enrichment analysis, univariate and multivariate Cox regression analysis, a prognostic risk model, and consensus clustering analysis, we analyzed 12 m6A-related lncRNAs in HNSCC sample data from The Cancer Genome Atlas (TCGA) database. We found 12 m6A-related lncRNAs in the training cohort and validated them in all cohorts by Kaplan–Meier and Cox regression analyses, revealing their independent prognostic value in HNSCC. Moreover, ROC analysis was conducted, confirming the strong predictive ability of this signature for HNSCC survival. GSEA and detailed immune infiltration analyses revealed specific pathways associated with m6A-related lncRNAs. In this study, a novel risk model including twelve genes (SAP30L-AS1, AC022098.1, LINC01475, AC090587.2, AC008115.3, AC015911.3, AL122035.2, AC010226.1, AL513190.1, ZNF32-AS1, AL035587.1 and AL031716.1) was built. It could accurately predict HNSCC outcomes and could provide new therapeutic targets for HNSCC patients.

Epstein–Barr Virus Epithelial Cancers—A Comprehensive Understanding to Drive Novel Therapies

Epstein–Barr virus (EBV) is a ubiquitous oncovirus associated with specific epithelial and lymphoid cancers. Among the epithelial cancers, nasopharyngeal carcinoma (NPC), lymphoepithelioma-like carcinoma (LELC), and EBV-associated gastric cancers (EBVaGC) are the most common. The role of EBV in the pathogenesis of NPC and in the modulation of its tumour immune microenvironment (TIME) has been increasingly well described. Much less is known about the pathogenesis and tumour–microenvironment interactions in other EBV-associated epithelial cancers. Despite the expression of EBV-related viral oncoproteins and a generally immune-inflamed cancer subtype, EBV-associated epithelial cancers have limited systemic therapeutic options beyond conventional chemotherapy. Immune checkpoint inhibitors are effective only in a minority of these patients and even less efficacious with molecular targeting drugs. Here, we examine the key similarities and differences of NPC, LELC, and EBVaGC and comprehensively describe the clinical, pathological, and molecular characteristics of these cancers. A deeper comparative understanding of these EBV-driven cancers can potentially uncover targets in the tumour, TIME, and stroma, which may guide future drug development and cast light on resistance to immunotherapy.

The Biological Function, Mechanism, and Clinical Significance of m6A RNA Modifications in Head and Neck Carcinoma: A Systematic Review

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, yet the molecular mechanisms underlying its onset and development have not yet been fully elucidated. Indeed, an in-depth understanding of the potential molecular mechanisms underlying HNSCC oncogenesis may aid the development of better treatment strategies. Recent epigenetic studies have revealed that the m6A RNA modification plays important roles in HNSCC. In this review, we summarize the role of m6A modification in various types of HNSCC, including thyroid, nasopharyngeal, hypopharyngeal squamous cell, and oral carcinoma. In addition, we discuss the regulatory roles of m6A in immune cells within the tumor microenvironment, as well as the potential molecular mechanisms. Finally, we review the development of potential targets for treating cancer based on the regulatory functions of m6A, with an aim to improving targeted therapies for HNSCC. Together, this review highlights the important roles that m6A modification plays in RNA synthesis, transport, and translation, and demonstrates that the regulation of m6A-related proteins can indirectly affect mRNA and ncRNA function, thus providing a novel strategy for reengineering intrinsic cell activity and developing simpler interventions to treat HNSCC.

lncRNA ZEB2-AS1 Aggravates Progression of Non-Small Cell Lung Carcinoma via Suppressing PTEN Level

Background

The aim of this study was to assess the involvement of lncRNA ZEB2-AS1 in the development of NSCLC and to explore the potential mechanism involved.

Material/Methods

ZEB2-AS1 expressions in 48 paired NSCLC tissues and paracancerous tissues were examined by qRT-PCR. ZEB2-AS1 level in NSCLC patients affected by tumor staging and lymphatic metastasis was examined as well. Regulatory effects of ZEB2-AS1 on proliferative, migratory, and invasive properties of NCI-H1650 and HCC827 cells were evaluated. The interaction between ZEB2-AS1 and EZH2 was identified through RIP assay. Subsequently, the binding of EZH2 on PTEN promoter region was tested by ChIP. Finally, rescue experiments were conducted to assess the involvement of PTEN in the development of NSCLC.

Results

ZEB2-AS1 was upregulated in NSCLC tissues and cell lines. Its level was higher in NSCLC patients with T3–T4 or accompanied with lymphatic metastasis relative to those with T1–T2 or without metastatic loci. Knockdown of ZEB2-AS1 suppressed proliferative, migratory, and invasive properties of NCI-H1650 and HCC827 cells. PTEN level was elevated after knockdown of ZEB2-AS1 or EZH2 in HCC827 cells. Subsequently, RIP assay proved the interaction between ZEB2-AS1 and EZH2. Knockdown of ZEB2-AS1 markedly reduced the binding of EZH2 on the PTEN promoter region. Notably, knockdown of PTEN reversed the effects of EZB2-AS1 on regulating proliferative, migratory, and invasive properties of NSCLC cells.

Conclusions

lncRNA ZEB2-AS1 is upregulated in NSCLC, which elevates the viability and malignant degree of NSCLC cells by downregulating PTEN, thus aggravating the progression of NSCLC.

Elevated SUV39H2 attributes to the progression of nasopharyngeal carcinoma via regulation of NRIP1

Nasopharyngeal carcinoma (NPC) is a prevalent tumor in southern China and southeast Asia. Recent studies have demonstrated that viral infection, somatic genetic changes, and epigenetic changes synergistically contribute to NPC pathogenesis. Genome-wide studies show that epigenetic aberrations likely drive nasopharyngeal carcinoma development and progression. This work is aimed at investigating the effect of histone methyltransferase SUV39H2 in NPC. The elevated expression of SUV39H2 in NPC is observed by analyzing GSE53819 and GSE12452 downloaded from the Gene Expression Omnibus (GEO) database. SUV39H2 knockdown inhibits NPC proliferation and induces the apoptosis of cancer cells. At last, RNaseq analysis identifies a variety of SUV39H2 downstream genes related with cancer, in which, NRIP1 is identified as a critical downstream target of SUV39H2 in NPC. Taken together, these findings provide a theoretical basis for understating the biological roles of SUV39H2 in NPC.

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.

miR-663 promotes NPC cell proliferation by directly targeting CDKN2A

MicroRNAs (miRs) act as important regulators during the development and progression of human cancer; however, the regulatory mechanism of miR-663 in nasopharyngeal carcinoma (NPC) remains unclear. The present study demonstrated that serum miR‑663 levels were significantly increased in patients with NPC compared with healthy controls. In addition, the serum levels of miR‑663 were associated with the grade, lymph node metastasis and clinical stage of NPC. The expression of miR‑663 was increased in NPC C666‑1 cells, compared with normal nasopharyngeal epithelial NP69 cells. The knockdown of miR‑663 markedly decreased the proliferation of C666‑1 cells through the induction of cell cycle arrest at the G1 stage. Cyclin‑dependent kinase inhibitor 2A (CDKN2A) was hypothesized to be a putative target of miR‑663. Further investigation confirmed that miR‑663 was able to directly bind to the 3' untranslated region of CDKN2A mRNA, and to negatively regulate CDKN2A protein expression in C666‑1 cells. Inhibition of CDKN2A expression attenuated the suppressive effects of miR‑663 knockdown on the proliferation and cell cycle progression of C666‑1 cells. In addition, it was observed that the mRNA and protein levels of CDKN2A were decreased in C666‑1 cells compared with NP69 cells. In conclusion, the results of the present study demonstrated that miR‑663 promoted the proliferation and cell cycle progression of NPC cells by directly targeting CDKN2A, suggesting that miR‑663 may become a potential therapeutic target for the treatment of NPC.

Identification of Polycomb Group Protein EZH2-Mediated DNA Mismatch Repair Gene MSH2 in Human Uterine Fibroids

Uterine fibroids (UFs) are benign smooth muscle neoplasms affecting up to 70% of reproductive age women. Treatment of symptomatic UFs places a significant economic burden on the US health-care system. Several specific genetic abnormalities have been described as etiologic factors of UFs, suggesting that a low DNA damage repair capacity may be involved in the formation of UF. In this study, we used human fibroid and adjacent myometrial tissues, as well as an in vitro cell culture model, to evaluate the expression of MutS homolog 2 (MSH2), which encodes a protein belongs to the mismatch repair system. In addition, we deciphered the mechanism by which polycomb repressive complex 2 protein, EZH2, deregulates MSH2 in UFs. The RNA expression analysis demonstrated the deregulation of MSH2 expression in UF tissues in comparison to its adjacent myometrium. Notably, protein levels of MSH2 were upregulated in 90% of fibroid tissues (9 of 10) as compared to matched adjacent myometrial tissues. Human fibroid primary cells treated with 3-deazaneplanocin A (DZNep), chemical inhibitor of EZH2, exhibited a significant increase in MSH2 expression (P < .05). Overexpression of EZH2 using an adenoviral vector approach significantly downregulated the expression of MSH2 (P < .05). Chromatin immunoprecipitation assay demonstrated that enrichment of H3K27me3 in promoter regions of MSH2 was significantly decreased in DZNep-treated fibroid cells as compared to vehicle control. These data suggest that EZH2-H3K27me3 regulatory mechanism dynamically changes the expression levels of DNA mismatch repair gene MSH2, through epigenetic mark H3K27me3. MSH2 may be considered as a marker for early detection of UFs.

Mutual regulation between CHD5 and EZH2 in hepatocellular carcinoma

Chromodomain helicase DNA binding protein 5 (CHD5) acts as a tumor suppressor in many cancers. In the present study, we demonstrated that reduced levels of CHD5 in hepatocellular carcinoma (HCC) tissues were significantly associated with metastasis and poor prognosis. Gain-of-function assays revealed that CHD5 suppressed motility and invasion of HCC cells. Subsequent investigations showed that CHD5 was epigenetically silenced by polycomb repressive complex 2 (PRC2)-mediated the trimethylation of histone H3 at lysine 27 (H3K27me3) in HCC cells. Furthermore, overexpression of CHD5 repressed enhancer of zeste homolog 2 (EZH2) and activated PRC2 target genes, such as p16 and p21. Chromatin immunoprecipitation and luciferase reporter assays also showed that CHD5 and EZH2 bind to each other's promoters and inhibit transcription. These findings uncovered, for the first time, a mutual suppression regulation between CHD5 and EZH2, which may provide new insights into their potential therapeutic significance for HCC.

Histone methylases as novel drug targets: developing inhibitors of EZH2

Post-translational modifications of histones (so-called epigenetic modifications) play a major role in transcriptional control and normal development, and are tightly regulated. Disruption of their control is a frequent event in disease. In particular, the methylation of lysine 27 on histone H3 (H3K27), induced by the methylase EZH2, emerges as a key control of gene expression and a major regulator of cell physiology. The identification of driver mutations in EZH2 has already led to new prognostic and therapeutic advances, and new classes of potent and specific inhibitors for EZH2 show promising results in preclinical trials. This review examines the roles of histone lysine methylases and demethylases in cells and focuses on the recent knowledge and developments about EZH2.

EZH2 expression in gliomas: Correlation with CDKN2A gene deletion/ p16 loss and MIB-1 proliferation index

Enhancer of zeste homolog 2 (EZH2) mediated down-regulation of CDKN2A/p16 has been observed in cell lines as well as in a few carcinomas. However, there is no study correlating EZH2 expression with CDKN2A/p16 status in gliomas. Hence, the present study was conducted to evaluate EZH2 expression in astrocytic and oligodendroglial tumors and correlate with CDKN2A/p16 status as well as MIB-1 labeling index (LI). Gliomas of all grades (n = 118) were studied using immunohistochemistry to assess EZH2, p16 and MIB-1 LI and fluorescence in situ hybrization to evaluate CDKN2A gene status. EZH2 expression and CDKN2A homozygous deletion (HD) were both significantly more frequent in high-grade gliomas (HGG). Further, strong EZH2 expression (LI ≥ 25%) was significantly more common in HGGs without CDKN2A HD (48.7%; 19/39) as compared to cases with deletion (15.8%; 3/19). Loss of p16 expression was noted in 100% and 51.3% of CDKN2A deleted and non-deleted tumors, respectively. Notably, 80% (16/20) of the CDKN2A non-deleted HGGs with p16 loss had strong EZH2 expression, in contrast to only 15.8% (3/19) in the deleted group. Loss of p16 expression significantly correlated with MIB-1 LI, irrespective of EZH2 status. Thus, this study shows that EZH2 expression correlates with tumor grade in both astrocytic and oligodendroglial tumors and hence can be used as a diagnostic marker to differentiate between low and HGGs. Further, this is the first report demonstrating an inverse correlation of strong EZH2 expression with CDKN2A HD in HGGs. Loss of p16 protein expression is mostly attributable to CDKN2A HD and correlates significantly with MIB-1 LI. Notably, our study for the first time suggests a possible epigenetic mechanism of p16 loss in CDKN2A non-deleted HGGs mediated by strong EZH2 expression. A hypothetical model for control of proliferative activity in low versus HGGs is therefore proposed.

SOX1 down-regulates β-catenin and reverses malignant phenotype in nasopharyngeal carcinoma

Background

Aberrant activation of the Wnt/β-catenin signaling pathway is an important factor in the development of nasopharyngeal carcinoma (NPC). Previous studies have demonstrated that the developmental gene sex-determining region Y (SRY)-box 1 (SOX1) inhibits cervical and liver tumorigenesis by interfering with the Wnt/β-catenin signaling pathway. However, the role of SOX1 in NPC remains unclear. This study investigates the function of SOX1 in NPC pathogenesis.

Results

Down-regulation of SOX1 was detected in NPC cell lines and tissues. Besides, quantitative methylation-specific polymerase chain reaction revealed that SOX1 promoter was hypermethylated in NPC cell lines. Ectopic expression of SOX1 in NPC cells suppressed colony formation, proliferation and migration in vitro and impaired tumor growth in nude mice. Restoration of SOX1 expression significantly reduced epithelial-mesenchymal transition, enhanced cell differentiation and induced cellular senescence. Conversely, transient knockdown of SOX1 by siRNA in these cells partially restored cell proliferation and colony formation. Notably, SOX1 was found to physically interact with β-catenin and reduce its expression independent of proteasomal activity, leading to inhibition of Wnt/β-catenin signaling and decreased expression of downstream target genes.

Conclusions

SOX1 decreases the expression of β-catenin in a proteasome-independent manner and reverses the malignant phenotype in NPC cells.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-257) contains supplementary material, which is available to authorized users.

The polycomb group protein EZH2 is a novel therapeutic target in tongue cancer

EZH2, a core member of the Polycomb Repressor Complex 2 (PRC2), mediates transcriptional silencing by catalyzing the trimethylation of histone 3 lysine 27 (H3K27), which plays key roles in cancer initiation and progression. Here, we investigated the expression pattern and biological roles of EZH2 in tongue tumorigenesis by loss-of-function assays using small interference RNA and EZH2 inhibitor DZNep. Also we determined the therapeutic efficiency of DZNep against tongue cancer in vivo. We found that aberrantly overexpressed EZH2 was associated with pathological grade, cervical nodes metastasis and Ki-67 expression in tongue cancers. Elevated EZH2 correlated with shorter overall survival and showed significant and independent prognostic importance in patients with tongue cancer. Both genetic and pharmacological depletion of EZH2 inhibited cell proliferation, migration, invasion and colony formation and decreased CD44+ subpopulation probably in part through modulating p16, p21 and E-caherin. Moreover, DZNep enhanced the anticancer effects of 5-Fluorouracil. Furthermore, intratumoral EZH2 inhibition induced by DZNep intraperitoneal administration significantly attenuated tumor growth in a tongue cancer xenograft model. Taken together, our results indicate that EZH2 serves as a key driver with multiple oncogenic functions during tongue tumorigenesis and a new biomarker for tongue cancer diagnosis and prognostic prediction. These findings open up possibilities for therapeutic intervention against EZH2 in tongue cancer.