Methylation-mediated silencing of microRNA-211 promotes cell growth and epithelial to mesenchymal transition through activation of the AKT/β-catenin pathway in GBM

EZH2 Promotes Glioma Cell Proliferation, Invasion, and Migration via Mir-142-3p/KCNQ1OT1/HMGB3 Axis : Running Title: EZH2 Promotes Glioma cell Malignant Behaviors

This study investigates the role and molecular mechanism of EZH2 in glioma cell proliferation, invasion, and migration. EZH2, miR-142-3p, lncRNA KCNQ1OT1, LIN28B, and HMGB3 expressions in glioma tissues and cells were determined using qRT-PCR or Western blot, followed by CCK-8 assay detection of cell viability, Transwell detection of invasion and migration, ChIP analysis of the enrichment of EZH2 and H3K27me3 on miR-142-3p promoter, dual-luciferase reporter assay and RIP validation of the binding of miR-142-3p-KCNQ1OT1 and KCNQ1OT1-LIN28B, and actinomycin D detection of KCNQ1OT1 and HMGB3 mRNA stability. A nude mouse xenograft model and a lung metastasis model were established. EZH2, KCNQ1OT1, LIN28B, and HMGB3 were highly expressed while miR-142-3p was poorly expressed in gliomas. EZH2 silencing restrained glioma cell proliferation, invasion, and migration. EZH2 repressed miR-142-3p expression by elevating the H3K27me3 level. miR-142-3p targeted KCNQ1OT1 expression, and KCNQ1OT1 bound to LIN28B to stabilize HMGB3 mRNA, thereby promoting its protein expression. EZH2 silencing depressed tumor growth and metastasis in nude mice via the miR-142-3p/KCNQ1OT1/HMGB3 axis. In conclusion, EZH2 curbed miR-142-3p expression, thereby relieving the inhibition of KCNQ1OT1 expression by miR-142-3p, enhancing the binding of KCNQ1OT1 to LIN28B, elevating HMGB3 expression, and ultimately accelerating glioma cell proliferation, invasion, and migration.

Bifunctional HDAC and DNMT inhibitor induces viral mimicry activates the innate immune response in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a unique breast cancer subtype characterized by a lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. Since TNBC lacks ER, PR, and HER2, there are currently no drugs that specifically target TNBC. Therefore, the development of new drugs or effective treatment strategies to target TNBC has become an urgent clinical need. Research has shown that the application of histone deacetylase (HDAC) inhibitors and DNA methyltransferase (DNMT) inhibitors leads to genomic and epigenomic instability. This, in turn, triggers the activation of pattern recognition receptors (PRRs) and subsequently activates downstream interferon (IFN) signalling pathways. In this study, the bifunctional HDAC and DNMT inhibitor J208 exhibited antitumour activity in TNBC cell lines. J208 effectively induced apoptosis and cell cycle arrest at the G0/G1 phase, inhibiting cell migration and invasion in TNBC. Moreover, this bifunctional inhibitor induced the expression of endogenous retroviruses (ERVs) and elicited a viral mimicry response, which increased the intracellular levels of double-stranded RNA (dsRNA) to activate the innate immune signalling pathway in TNBC. In summary, we demonstrated that the bifunctional inhibitor J208, which is designed to inhibit HDAC and DNMT, has potent anticancer effects, providing a new research basis for reactivating antitumour immunity by triggering innate immune signalling and offering a promising strategy for TNBC treatment.

Regulatory role of miRNAs on Wnt/β-catenin signaling in tumorigenesis of glioblastoma

Glioblastoma (GBM) is one of the most aggressive tumors in the brain with high mortality worldwide. Despite recent advances in therapeutic strategies, the survival rate remains low in patients with GBM. The pathogenesis of GBM is a very complicated process involving various genetic mutations affecting several oncogenic signaling pathways like Wnt/β-catenin axis. Overactivation of the Wnt/β-catenin signaling pathway is associated with decreased survival and poor prognosis in patients with GBM. MicroRNAs (miRNAs) were shown to play important roles in the regulation of cell proliferation, differentiation, apoptosis, and tumorigenesis by modulating the expression of their target genes. Aberrant expression of miRNAs were reported in various human malignancies including GBM, breast, colorectal, liver, and prostate cancers, but little is known about their cellular mechanisms. Therefore, recognition of the expression profile and regulatory effects of miRNAs on the Wnt/β-catenin pathway may offer a novel approach for the classification, diagnosis, prognosis, and treatment of patients with GBM. This review summarizes previous data on the modulatory role of miRNAs on the Wnt/β-catenin pathway implicated in tumorigenesis of GBM.

HMGA2 regulation by miRNAs in cancer: affecting cancer hallmarks and therapy response

High mobility group A 2 (HMGA2) is a protein that modulates the structure of chromatin in the nucleus. Importantly, aberrant expression of HMGA2 occurs during carcinogenesis, and this protein is an upstream mediator of cancer hallmarks including evasion of apoptosis, proliferation, invasion, metastasis, and therapy resistance. HMGA2 targets critical signaling pathways such as Wnt/β-catenin and mTOR in cancer cells. Therefore, suppression of HMGA2 function notably decreases cancer progression and improves outcome in patients. As HMGA2 is mainly oncogenic, targeting expression by non-coding RNAs (ncRNAs) is crucial to take into consideration since it affects HMGA2 function. MicroRNAs (miRNAs) belong to ncRNAs and are master regulators of vital cell processes, which affect all aspects of cancer hallmarks. Long ncRNAs (lncRNAs) and circular RNAs (circRNAs), other members of ncRNAs, are upstream mediators of miRNAs. The current review intends to discuss the importance of the miRNA/HMGA2 axis in modulation of various types of cancer, and mentions lncRNAs and circRNAs, which regulate this axis as upstream mediators. Finally, we discuss the effect of miRNAs and HMGA2 interactions on the response of cancer cells to therapy. Regarding the critical role of HMGA2 in regulation of critical signaling pathways in cancer cells, and considering the confirmed interaction between HMGA2 and one of the master regulators of cancer, miRNAs, targeting miRNA/HMGA2 axis in cancer therapy is promising and this could be the subject of future clinical trial experiments.

MiR-211 plays a dual role in cancer development: From tumor suppressor to tumor enhancer

Cancer is a general term for more than 100 unique malignancies in different organs of the body. Each cancer type and subtype has its own unique genetic, epigenetic, and cellular factors accountable for malignant progression and metastasis. Small non-coding RNAs called miRNAs target mRNAs and play a vital part in the pathogenesis of human diseases, specifically cancer. Recent investigations provided knowledge of the deregulation of miR-211 in various cancer types and disclosed that miR-211 has an oncogenic or tumor-suppressive impact on tumourigenesis and cancer development. Moreover, recent discoveries which clarify the essential functions of miR-211 might provide proof for its prognosis, diagnostic and therapeutic impact on cancer. Thereby, this review will discuss recent findings regarding miR-211 expression level, target genes, and mechanisms in different cancers. In addition, the most recent results that propose miR-211 usefulness as a noninvasive biomarker and therapeutic factor for the diagnosis and treatment of cancer will be explained.

Regulatory interplay between microRNAs and WNT pathway in glioma

Glioma is one of the most common neoplasms of the central nervous system with a poor survival. Due to the obstacles in treating this disease, a part of recent studies mainly focuses on identifying the underlying molecular mechanisms that contribute to its malignancy. Altering microRNAs (miRNAs) expression pattern has been identified obviously in many cancers. Through regulating various targets and signaling pathways, miRNAs play a pivotal role in cancer progression. As one of the essential signaling pathways, WNT pathway is dysregulated in many cancers, and a growing body of evidence emphasis its dysregulation in glioma. Herein, we provide a comprehensive review of miRNAs involved in WNT pathway in glioma. Moreover, we show the interplay between miRNAs and WNT pathway in regulating different processes such as proliferation, invasion, migration, radio/chemotherapy resistance, and epithelial-mesenchymal-transition. Then, we introduce several drugs and treatments against glioma, which their effects are mediated through the interplay of WNT pathway and miRNAs.

The Paradoxical Behavior of microRNA-211 in Melanomas and Other Human Cancers

Cancer initiation, progression, and metastasis leverage many regulatory agents, such as signaling molecules, transcription factors, and regulatory RNA molecules. Among these, regulatory non-coding RNAs have emerged as molecules that control multiple cancer types and their pathologic properties. The human microRNA-211 (MIR211) is one such molecule, which affects several cancer types, including melanoma, glioblastoma, lung adenocarcinomas, breast, ovarian, prostate, and colorectal carcinoma. Previous studies suggested that in certain tumors MIR211 acts as a tumor suppressor while in others it behaves as an oncogenic regulator. Here we summarize the known molecular genetic mechanisms that regulate MIR211 gene expression and molecular pathways that are in turn controlled by MIR211 itself. We discuss how cellular and epigenetic contexts modulate the biological effects of MIR211, which exhibit pleiotropic effects. For example, up-regulation of MIR211 expression down-regulates Warburg effect in melanoma tumor cells associated with an inhibition of the growth of human melanoma cells in vitro, and yet these conditions robustly increase tumor growth in xenografted mice. Signaling through the DUSP6-ERK5 pathway is modulated by MIR211 in BRAFV600E driven melanoma tumors, and this function is involved in the resistance of tumor cells to the BRAF inhibitor, Vemurafenib. We discuss several alternate but testable models, involving stochastic cell-to-cell expression heterogeneity due to multiple equilibria involving feedback circuits, intracellular communication, and genetic variation at miRNA target sties, to reconcile the paradoxical effects of MIR211 on tumorigenesis. Understanding the precise role of this miRNA is crucial to understanding the genetic basis of melanoma as well as the other cancer types where this regulatory molecule has important influences. We hope this review will inspire novel directions in this field.

Mesenchymal Transformation: The Rosetta Stone of Glioblastoma Pathogenesis and Therapy Resistance

Despite decades of research, glioblastoma (GBM) remains invariably fatal among all forms of cancers. The high level of inter- and intratumoral heterogeneity along with its biological location, the brain, are major barriers against effective treatment. Molecular and single cell analysis identifies different molecular subtypes with varying prognosis, while multiple subtypes can reside in the same tumor. Cellular plasticity among different subtypes in response to therapies or during recurrence adds another hurdle in the treatment of GBM. This phenotypic shift is induced and sustained by activation of several pathways within the tumor itself, or microenvironmental factors. In this review, the dynamic nature of cellular shifts in GBM and how the tumor (immune) microenvironment shapes this process leading to therapeutic resistance, while highlighting emerging tools and approaches to study this dynamic double-edged sword are discussed.

miRNA signature in glioblastoma: Potential biomarkers and therapeutic targets

MicroRNAs (miRNAs) are transcripts with sizes of about 22 nucleotides, which are produced through a multistep process in the nucleus and cytoplasm. These transcripts modulate the expression of their target genes through binding with certain target regions, particularly 3' suntranslated regions. They are involved in the pathogenesis of several kinds of cancers, such as glioblastoma. Several miRNAs, including miR-10b, miR-21, miR-17-92-cluster, and miR-93, have been up-regulated in glioblastoma cell lines and clinical samples. On the other hand, expression of miR-7, miR-29b, miR-32, miR-34, miR-181 family members, and a number of other miRNAs have been decreased in this type of cancer. In the current review, we explain the role of miRNAs in the pathogenesis of glioblastoma through providing a summary of studies that reported dysregulation of these epigenetic effectors in this kind of brain cancer.

The complex interplay between DNA methylation and miRNAs in gene expression regulation

The short, non-coding RNAs, also called microRNAs (miRNAs) can bind complementary sequences on cellular mRNAs. The consequence of this binding is generally the degradation of mRNA and the inhibition of its translation. For this reason, miRNAs are included among the epigenetic factors acting as a modulator of gene expression. How miRNAs expression is, in turn, regulated is still the object of active investigation, but DNA methylation, another epigenetic modification, seems to play a central role in this sense. The "one-carbon" metabolism is responsible for the metabolic regulation of trans-methylation reactions and, therefore, DNA methylation. For this reason, to investigate the possible correlations between alterations of the one-carbon metabolism and differential DNA methylation sounds interesting. Moreover, recent evidence indicates that, vice-versa, miRNAs are associated with DNA methylation modulation, in a mutual cross-talk. The present review will discuss the interplay between miRNAs and DNA methylation and its fall-out on gene expression regulation.

High Mobility Group A (HMGA): Chromatin Nodes Controlled by a Knotty miRNA Network

High mobility group A (HMGA) proteins are oncofoetal chromatin architectural factors that are widely involved in regulating gene expression. These proteins are unique, because they are highly expressed in embryonic and cancer cells, where they play a relevant role in cell proliferation, stemness, and the acquisition of aggressive tumour traits, i.e., motility, invasiveness, and metastatic properties. The HMGA protein expression levels and activities are controlled by a connected set of events at the transcriptional, post-transcriptional, and post-translational levels. In fact, microRNA (miRNA)-mediated RNA stability is the most-studied mechanism of HMGA protein expression modulation. In this review, we contribute to a comprehensive overview of HMGA-targeting miRNAs; we provide detailed information regarding HMGA gene structural organization and a comprehensive evaluation and description of HMGA-targeting miRNAs, while focusing on those that are widely involved in HMGA regulation; and, we aim to offer insights into HMGA-miRNA mutual cross-talk from a functional and cancer-related perspective, highlighting possible clinical implications.

circ_0001730 promotes proliferation and invasion via the miR-326/Wnt7B axis in glioma cells

Aim: To study the role of circRNA (circ_0001730) in glioblastoma. Materials & methods: The interaction between circ_0001730 and miR-326 was confirmed by FISH, RNA pull down, RNA-binding protein immunoprecipitation and luciferase reporter assays. Cell proliferation and growth were determined by MTT, EdU and colony formation assays. Cell migration was assessed by the Boyden assay. Results: The levels of circ_0001730 were elevated in glioblastoma cell lines and tissues. circ_0001730 downregulation suppressed migration and proliferation in glioblastoma cells. SP1 bounds to the promoter of circ_0001730 host gene EPHB4 thereby increasing the expression of circ_0001730. circ_0001730 activated the Wnt/β-catenin pathway via the miR-326/Wnt7B axis. Conclusion: circ_000173 promoted growth and invasion in glioblastoma cells via the miR-326/Wnt7B axis.

Silencing of microRNA-708 promotes cell growth and epithelial-to-mesenchymal transition by activating the SPHK2/AKT/β-catenin pathway in glioma

Aberrant microRNA-708 (miR-708) expression is frequently reported in cancer studies; however, its role in glioma has not been examined in detail. We investigated miR-708 function in glioma and revealed that miR-708 expression was significantly down-regulated in glioma tissues and cell lines. Restoration of miR-708 inhibited glioma cell growth and invasion both in vitro and in vivo. The oncogene SPHK2 (sphingosine kinase 2) was identified as a downstream target of miR-708 using luciferase and western blot assays. miR-708 inhibited AKT/β-catenin signaling, which is activated by SPHK2. In addition, we revealed that miR-708 was transcriptionally repressed by EZH2 (enhancer of zeste homolog 2)-induced histone H3 lysine 27 trimethylation and promoter methylation. In summary, our findings revealed that miR-708 is a glioma tumor suppressor and suggest that miR-708 is a potential therapeutic target for glioma patients.

Polycomb complex mediated epigenetic reprogramming alters TGF-β signaling via a novel EZH2/miR-490/TGIF2 axis thereby inducing migration and EMT potential in glioblastomas

Recent advancement in understanding cancer etiology has highlighted epigenetic deregulation as an important phenomenon leading to poor prognosis in glioblastoma (GBM). Polycomb repressive complex 2 (PRC2) is one such important epigenetic modifier reportedly altered in GBM. However, its defined mechanism in tumorigenesis still remains elusive. In present study, we analyzed our in-house ChIPseq data for H3k27me3 modified miRNAs and identified miR-490-3p to be the most common target in GBM with significantly downregulated expression in glioma patients in both TCGA and GBM patient cohort. Our functional analysis delineates for the first time, a central role of PRC2 catalytic unit EZH2 in directly regulating expression of this miRNA and its host gene CHRM2 in GBM. In accordance, cell line treatment with EZH2 siRNA and 5-azacytidine also confirmed its coregulation by CpG and histone methylation based epigenetic mechanisms. Furthermore, induced overexpression of miR-490-3p in GBM cell lines significantly inhibited key hallmarks including cellular proliferation, colony formation and spheroid formation, as well as epithelial-to-mesenchymal transition (EMT), with downregulation of multiple EMT transcription factors and promigratory genes (MMP9, CCL5, PIK3R1, ICAM1, ADAM17 and NOTCH1). We also for the first time report TGFBR1 and TGIF2 as two direct downstream effector targets of miR-490-3p that are also deregulated in GBM. TGIF2, a novel target, was shown to promote migration and EMT that could partially be rescued by miR-490-3p overexpression. Overall, this stands as a first study that provides a direct link between epigenetic modulator EZH2 and oncogenic TGF-β signaling involving novel miR-490-3p/TGIF2/TGFBR1 axis, that being targetable might be promising in developing new therapeutic intervention strategies for GBM.

Methylation-Mediated Silencing of MicroRNA-211 Decreases the Sensitivity of Melanoma Cells to Cisplatin

BACKGROUND Malignant melanoma is recalcitrant to most existing chemotherapies, and aberrant expression of miR-211 plays prominent roles in progression of melanoma. However, the trigger mechanism of aberrant miR-211 expression in melanoma is still elusive. MATERIAL AND METHODS We used qRT-PCR to test miR-211 expression. Cell viability assay and mouse xenograft assay were performed to examine the role of miR-211 on the sensitivity of melanoma cells to cisplatin. The epigenetic modification of miR-211 promoter was assess by DNA methylation analysis and DAC treatment. RESULTS In this study, decreased miR-211 expression was detected. Bisulfite sequencing PCR showed that DNA hypermethylation contributed to the downregulation of miR-211 in melanoma tissues. In melanoma cells, overexpressed 211 could enhance the anticancer effect of cisplatin and restoration of miR-211 rendered susceptibility to cisplatin in cisplatin-resistant cells. And the same result was showed in vivo by mouse xenograft assay. What is more, DAC treatment could increase miR-211 expression and EZH2 expression was increased in cisplatin-resistant cells. MiR-211 could be transcriptionally repressed by EZH2 mediated promoter methylation. CONCLUSIONS Taken together, our findings revealed that epigenetic modification of miR-211 governed melanoma cell chemosensitivity and were involved in the progression of tumorigenesis.

EMT is associated with an epigenetic signature of ECM remodeling genes

Type III epithelial–mesenchymal transition (EMT) has been previously associated with increased cell migration, invasion, metastasis, and therefore cancer aggressiveness. This reversible process is associated with an important gene expression reprogramming mainly due to epigenetic plasticity. Nevertheless, most of the studies describing the central role of epigenetic modifications during EMT were performed in a single-cell model and using only one mode of EMT induction. In our study, we studied the overall modulations of gene expression and epigenetic modifications in four different EMT-induced cell models issued from different tissues and using different inducers of EMT. Pangenomic analysis (transcriptome and ChIP–sequencing) validated our hypothesis that gene expression reprogramming during EMT is largely regulated by epigenetic modifications of a wide range of genes. Indeed, our results confirmed that each EMT model is unique and can be associated with a specific transcriptome profile and epigenetic program. However, we could select some genes or pathways that are similarly regulated in the different models and that could therefore be used as a common signature of all EMT models and become new biomarkers of the EMT phenotype. As an example, we can cite the regulation of gene-coding proteins involved in the degradation of the extracellular matrix (ECM), which are highly induced in all EMT models. Based on our investigations and results, we identified ADAM19 as a new biomarker of in vitro and in vivo EMT and we validated this biological new marker in a cohort of non-small lung carcinomas.

microRNA-141-3p fosters the growth, invasion, and tumorigenesis of cervical cancer cells by targeting FOXA2

microRNA (miR)-141-3p has context-dependent effects on tumor progression. In this study, we attempted to explore the expression and function of miR-141-3p in cervical cancer. We found that miR-141-3p expression was significantly increased in cervical cancer specimens relative to normal cervical tissues. Moreover, miR-141-3p levels were associated with tumor size and lymph node metastasis status. Ectopic expression of miR-141-3p significantly increased cervical cancer cell proliferation, colony formation, invasion, and epithelial to mesenchymal transition, whereas depletion of miR-141-3p suppressed cervical cancer cell proliferation and invasion. FOXA2 was identified to be a target of miR-141-3p. Overexpression of miR-141-3p led to a marked inhibition of endogenous FOXA2 in cervical cancer cells. FOXA2 silencing phenocopied the effects of miR-141-3p overexpression on cervical cancer cell proliferation and invasion. Enforced expression of FOXA2 blocked the effects of miR-141-3p on cervical cancer cell proliferation and invasion. miR-141-3p overexpression significantly accelerated the growth of xenograft tumors, which was accompanied by a striking reduction in FOXA2 expression. miR-141-3p acts as an oncogene in cervical cancer largely through repression of FOXA2. Targeting miR-141-3p may represent a potential therapeutic strategy for cervical cancer.

miR-497/Wnt3a/c-jun feedback loop regulates growth and epithelial-to-mesenchymal transition phenotype in glioma cells

Glioma is one of the most frequent intracranial malignant tumors. Abnormal expression of microRNAs usually contributes to the development and progression of glioma. In the current study, we explored the role and underlying mechanism of miR-497 in glioma. We revealed that miR-497 expression was significantly down-regulated in glioma tissues and cell lines. Reduced expression of miR-497 was associated with poor disease-free and over-all survival rate. Restoration of miR-497 decreased glioma cell growth and invasion both in vitro and in vivo. The oncogene Wnt3a was identified as a downstream target of miR-497 by using luciferase and western blot assays. Knockdown of Wnt3a mimicked the effect of miR-497 in glioma cells. In summary, our study demonstrated that miR-497 may function as a tumor suppressor in glioma and suggested that miR-497 is a potential therapeutic target for glioma patients.

Functional Role of Non-Coding RNAs during Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a key biological process involved in a multitude of developmental and pathological events. It is characterized by the progressive loss of cell-to-cell contacts and actin cytoskeletal rearrangements, leading to filopodia formation and the progressive up-regulation of a mesenchymal gene expression pattern enabling cell migration. Epithelial-to-mesenchymal transition is already observed in early embryonic stages such as gastrulation, when the epiblast undergoes an EMT process and therefore leads to the formation of the third embryonic layer, the mesoderm. Epithelial-to-mesenchymal transition is pivotal in multiple embryonic processes, such as for example during cardiovascular system development, as valve primordia are formed and the cardiac jelly is progressively invaded by endocardium-derived mesenchyme or as the external cardiac cell layer is established, i.e., the epicardium and cells detached migrate into the embryonic myocardial to form the cardiac fibrous skeleton and the coronary vasculature. Strikingly, the most important biological event in which EMT is pivotal is cancer development and metastasis. Over the last years, understanding of the transcriptional regulatory networks involved in EMT has greatly advanced. Several transcriptional factors such as Snail, Slug, Twist, Zeb1 and Zeb2 have been reported to play fundamental roles in EMT, leading in most cases to transcriptional repression of cell⁻cell interacting proteins such as ZO-1 and cadherins and activation of cytoskeletal markers such as vimentin. In recent years, a fundamental role for non-coding RNAs, particularly microRNAs and more recently long non-coding RNAs, has been identified in normal tissue development and homeostasis as well as in several oncogenic processes. In this study, we will provide a state-of-the-art review of the functional roles of non-coding RNAs, particularly microRNAs, in epithelial-to-mesenchymal transition in both developmental and pathological EMT.