MicroRNA-21 promotes glioblastoma tumorigenesis by down-regulating insulin-like growth factor-binding protein-3 (IGFBP3)

The Role of Circulating MicroRNA in Glioblastoma Liquid Biopsy

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignancy of the central nervous system. The standard used to monitor disease progression and therapeutic response has been magnetic resonance imaging, which is usually obtained preoperatively and postoperatively. Patients with GBM are monitored every 2-3 months and scans are repeated until progression is detected. Sometimes there is an inability to detect tumor progression or difficulty in differentiating tumor progression from pseudoprogression. With the difficulty of distinguishing disease progression, as well as the cost of imaging, there may be a need for the existence of a noninvasive liquid biopsy. There is no reliable biomarker for GBM that can be used for liquid biopsy, but if one could be detected in serum or cerebrospinal fluid and vary with tumor burden, then, it could be developed into one. MicroRNAs (miRNAs) are short, single-stranded, noncoding RNAs that posttranscriptionally control gene expression. They play vital roles in tumor progression, migration, invasion, and stemness. Because miRNAs are secreted in stable forms in bodily fluid, either via extracellular vesicles or in cell-free form, they have great potential as biomarkers that can be used for liquid biopsy. Various miRNAs that are dysregulated in GBM have been identified in tissue, cerebrospinal fluid, and serum samples. There needs to be standardization of sample collection and quantification for both cell-free and exosomal-derived samples. Further studies need to be performed on larger cohorts to evaluate the sensitivity and specificity of not just miRNAs but most potential biomarkers.

MiR-3116 sensitizes glioma cells to temozolomide by targeting FGFR1 and regulating the FGFR1/PI3K/AKT pathway

Glioma is a brain tumour that is often diagnosed, and temozolomide (TMZ) is a common chemotherapeutic drug used in glioma. Yet, resistance to TMZ is a chief hurdle towards curing the malignancy. The current work explores the pathways and involvement of miR-3116 in the TMZ resistance. miR-3116 and FGFR1 mRNA were quantified by real-time PCR in malignant samples and cell lines. Appropriate assays were designed for apoptosis, viability, the ability to form colonies and reporter assays to study the effects of the miR-3116 or FGFR1. The involvement of PI3K/AKT signalling was assessed using Western blotting. Tumorigenesis was evaluated in an appropriate xenograft mouse model in vivo. This work revealed that the levels of miR-3116 dipped in samples resistant to TMZ, while increased miR-3116 caused an inhibition of the tumour features mentioned above to hence augment TMZ sensitivity. miR-3116 was found to target FGFR1. When FGFR1 was overexpressed, resistance to TMZ was augmented and reversed the sensitivity caused by miR-3116. Our findings further confirmed PI3K/AKT signalling pathway is involved in this action. In conclusion, miR-3116 sensitizes glioma cells to TMZ through FGFR1 downregulation and the PI3K/AKT pathway inactivation. Our results provide a strategy to overcome TMZ resistance in glioma treatment.

MicroRNAs associated to single drug components of R-CHOP identifies diffuse large B-cell lymphoma patients with poor outcome and adds prognostic value to the international prognostic index

Background

Treatment resistance is a major clinical challenge of diffuse large B-cell lymphoma (DLBCL) where approximately 40% of the patients have refractory disease or relapse. Since DLBCL is characterized by great clinical and molecular heterogeneity, the purpose of the present study was to investigate whether miRNAs associated to single drug components of R-CHOP can improve robustness of individual markers and serve as a prognostic classifier.

Methods

Fifteen DLBCL cell lines were tested for sensitivity towards single drug compounds of the standard treatment R-CHOP: rituximab (R), cyclophosphamide (C), doxorubicin (H), and vincristine (O). For each drug, cell lines were ranked using the area under the dose-response curve and grouped as either sensitive, intermediate or resistant. Baseline miRNA expression data were obtained for each cell line in untreated condition, and differential miRNA expression analysis between sensitive and resistant cell lines identified 43 miRNAs associated to growth response after exposure towards single drugs of R-CHOP. Using the Affymetrix HG-U133 platform, expression levels of miRNA precursors were assessed in 701 diagnostic DLBCL biopsies, and miRNA-panel classifiers predicting disease progression were build using multiple Cox regression or random survival forest. Classifiers were validated and ranked by repeated cross-validation.

Results

Prognostic accuracies were assessed by Brier Scores and time-varying area under the ROC curves, which revealed better performance of multivariate Cox models compared to random survival forest models. The Cox model including miR-146a, miR-155, miR-21, miR-34a, and miR-23a~miR-27a~miR-24-2 cluster performed the best and successfully stratified GCB-DLBCL patients into high- and low-risk of disease progression. In addition, combination of the Cox miRNA-panel and IPI substantially increased prognostic performance in GCB classified patients.

Conclusion

As a proof of concept, we found that expression data of drug associated miRNAs display prognostic utility and adding these to IPI improves prognostic stratification of GCB-DLBCL patients treated with R-CHOP.

Super-enhancers: A new frontier for glioma treatment

Glioma is the most common primary malignant tumor in the human brain. Although there are a variety of treatments, such as surgery, radiation and chemotherapy, glioma is still an incurable disease. Super-enhancers (SEs) are implicated in the control of tumor cell identity, and they promote oncogenic transcription, which supports tumor cells. Inhibition of the SE complex, which is required for the assembly and maintenance of SEs, may repress oncogenic transcription and impede tumor growth. In this review, we discuss the unique characteristics of SEs compared to typical enhancers, and we summarize the recent advances in the understanding of their properties and biological role in gene regulation. Additionally, we highlight that SE-driven lncRNAs, miRNAs and genes are involved in the malignant phenotype of glioma. Most importantly, the application of SE inhibitors in different cancer subtypes has introduced new directions in glioma treatment.

The Yin-Yang Regulation of Reactive Oxygen Species and MicroRNAs in Cancer

Reactive oxygen species (ROS) are highly reactive oxygen-containing chemical species formed as a by-product of normal aerobic respiration and also from a number of other cellular enzymatic reactions. ROS function as key mediators of cellular signaling pathways involved in proliferation, survival, apoptosis, and immune response. However, elevated and sustained ROS production promotes tumor initiation by inducing DNA damage or mutation and activates oncogenic signaling pathways to promote cancer progression. Recent studies have shown that ROS can facilitate carcinogenesis by controlling microRNA (miRNA) expression through regulating miRNA biogenesis, transcription, and epigenetic modifications. Likewise, miRNAs have been shown to control cellular ROS homeostasis by regulating the expression of proteins involved in ROS production and elimination. In this review, we summarized the significance of ROS in cancer initiation, progression, and the regulatory crosstalk between ROS and miRNAs in cancer.

Downregulation of miR-21 inhibits the malignant phenotype of pancreatic cancer cells by targeting VHL

Background

MicroRNA (miR)-21 is overexpressed in numerous types of malignancy and participates in the development of cancer. However, the basic mechanism of the influence of miR-21 on the malignant phenotype of pancreatic cancer remains unclear.

Purpose

The present study aimed to investigate the role of miR-21 in pancreatic cancer development and explore its molecular mechanism.

Patients and methods

The tissue samples were collected at the Second Hospital of Tianjin Medical University (Tianjin, China) between January 2013 and December 2015. The expression of VHL in tissue samples was evaluated by IHC staining. The expression of miR-21 was measured by quantitative real-time polymerase chain reaction (qRT-PCR). MiR-21 target gene was detected by real-time PCR, Western blot and the luciferase reporter assay. Cell viability, cell proliferation, cell migration and invasion were evaluated by the MTT assays, the colony formation assays and the transwell assays. The nude mouse tumor xenograft model was performed to detect the effect of miR-21 on tumor growth in vivo.

Results

Von Hippel-Lindau tumor suppressor (VHL) was downregulated in pancreatic cancer tissues compared with pancreatic non-tumor tissues. VHL was identified as a novel direct target of miR-21, by which it is negatively regulated. In PANC-1 cells, inhibition of miR-21 and upregulation of VHL significantly suppressed cell proliferation, migration and invasion. Knockdown of miR-21 inhibited the hypoxia-inducible factor (HIF)-1α/vascular endothelial growth factor (VEGF) pathway, while inhibiting the expression of matrix metallopeptidase (MMP)-2 and MMP-9. Silencing of miR-21 inhibited tumor growth in vivo.

Conclusion

Knockdown miR-21 increased the expression of VHL, and thus modulated the HIF-1α/VEGF pathway and the expression of MMP-2 and MMP-9, which led to the inhibition of the proliferation, migration and invasion of pancreatic cancer cells. All of these results suggest that the miR-21/VHL interaction may be a novel potential target for pancreatic cancer prevention and therapy.

Potential Therapeutic Effects of Exosomes Packed With a miR-21-Sponge Construct in a Rat Model of Glioblastoma

Glioblastoma multiforme (GBM) is a grade 4 and the most aggressive form of glioma, with a poor response to current treatments. The expression of microRNAs (miRNAs) is widely dysregulated in various cancers, including GBM. One of the overexpressed miRNAs in GBM is miR-21 which promotes proliferation, invasion and metastatic behaviors of tumor cells. With a size of 30-100 nm, the extracellular vesicles "exosomes" have emerged as a novel and powerful drug delivering systems. Recently, exosomal transfer of miRNAs or anti-miRNAs to tumor cells has introduced a new approach for therapeutic application of miRNAs to combat cancer. Here, we have tried to down-regulate miR-21 expression in glioma cell lines, U87-MG, and C6, by using engineered exosomes, packed with a miR-21-sponge construct. Our data revealed that the engineered exosomes have the potential to suppress miR-21 and consequently to upregulate miR-21 target genes, PDCD4 and RECK. Interestingly, in cells treated with miR-21-sponge exosomes we observed a decline in proliferation and also an elevation in apoptotic rates. Finally, in a rat model of glioblastoma, administrating exosomes loaded with a miR-21-sponge construct leads to a significant reduction in the volume of the tumors. In brief, our findings suggest a new therapeutic strategy to use engineered exosomes to deliver a miR-21-sponge construct to GBM cells, in order to block its malignant behavior.

Intranasal delivery of targeted polyfunctional gold-iron oxide nanoparticles loaded with therapeutic microRNAs for combined theranostic multimodality imaging and presensitization of glioblastoma to temozolomide

The prognosis for glioblastoma (GBM) remains depressingly low. The biological barriers of the brain present a major challenge to achieving adequate drug concentrations for GBM therapy. To address this, we explore the potential of the nose-to-brain direct transport pathway to bypass the blood-brain barrier, and to enable targeted delivery of theranostic polyfunctional gold-iron oxide nanoparticles (polyGIONs) surface loaded with therapeutic miRNAs (miR-100 and antimiR-21) to GBMs in mice. These nanoformulations would thus allow presensitization of GBM cells to the systemically delivered chemotherapy drug temozolomide (TMZ), as well as in vivo multimodality molecular and anatomic imaging of nanoparticle delivery, trafficking, and treatment effects. First, we synthesized GIONs coated with β-cyclodextrin-chitosan (CD-CS) hybrid polymer, and co-loaded with miR-100 and antimiR-21. Then we decorated their surface with PEG-T7 peptide using CD-adamantane host-guest chemistry. The resultant polyGIONs showed efficient miRNA loading with enhanced serum stability. We characterized them for particle size, PDI, polymer functionalization, charge and release using dynamic light scattering analysis, TEM and qRT-PCR. For in vivo intranasal delivery, we used U87-MG GBM cell-derived orthotopic xenograft models in mice. Intranasal delivery resulted in efficient accumulation of Cy5-miRNAs in mice treated with T7-targeted polyGIONs, as demonstrated by in vivo optical fluorescence and MR imaging. We measured the therapeutic response of these FLUC-EGFP labelled U87-MG GBMs using bioluminescence imaging. Overall, there was a significant increase in survival of mice co-treated with T7-polyGIONs loaded with miR-100/antimiR-21 plus systemic TMZ, compared to the untreated control group, or the animals receiving non-targeted polyGIONs-miR-100/antimiR-21, or TMZ alone. Once translated clinically, this novel theranostic nanoformulation and its associated intranasal delivery strategy will have a strong potential to potentiate the effects of TMZ treatment in GBM patients.

Development of Novel antimiRzymes for Targeted Inhibition of miR-21 Expression in Solid Cancer Cells

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the regulation of gene expression. Previous reports showed an over-expression of miRNA-21 (miR-21) in various cancer cells, and its up-regulation is closely related to cancer initiation, proliferation and metastasis. In this work, we envisioned the development of novel antimiRzymes (anti-miRNA-DNAzyme) that are capable of selectively targeting and cleaving miR-21 and inhibit its expression in cancer cells using the DNAzyme technique. For this purpose, we have designed different antimiRzyme candidates by systematically targeting different regions of miR-21. Our results demonstrated that RNV541, a potential arm-loop-arm type antimiRzyme, was very efficient (90%) to suppress miR-21 expression in U87MG malignant glioblastoma cell line at 200 nM concentration. In addition, RNV541 also inhibited miR-21 expression (50%) in MDA-MB-231 breast cancer cell line. For targeted delivery, we conjugated RNV541 with a transferrin receptor (TfR) targeting aptamer for TfR-mediated cancer cell delivery. As expected, the developed chimeric structure efficiently delivered the antimiRzyme RNV541 into TfR positive glioblastoma cells. TfR aptamer-RNV541 chimeric construct showed 52% inhibition of miR-21 expression in U87MG glioblastoma cells at 2000 nM concentration, without using any transfection reagents, making it a highly desirable strategy to tackle miR-21 over-expressed malignant cancers. Although these are in vitro based observations, based on our results, we firmly believe that our findings could be beneficial towards the development of targeted cancer therapeutics where conventional therapies face several challenges.

Liquid Biopsy in Glioblastoma: Opportunities, Applications and Challenges

Liquid biopsy represents a minimally invasive procedure that can provide similar information from body fluids to what is usually obtained from a tissue biopsy sample. Its implementation in the clinical setting might significantly renew the field of medical oncology, facilitating the introduction of the concepts of precision medicine and patient-tailored therapies. These advances may be useful in the diagnosis of brain tumors that currently require surgery for tissue collection, or to perform genetic tumor profiling for disease classification and guidance of therapy. In this review, we will summarize the most recent advances and putative applications of liquid biopsy in glioblastoma, the most common and malignant adult brain tumor. Moreover, we will discuss the remaining challenges and hurdles in terms of technology and biology for its clinical application.

The protean world of non-coding RNAs in glioblastoma

Non-coding ribonucleic acids (ncRNAs) are a diverse group of RNA molecules that are mostly not translated into proteins following transcription. We review the role of ncRNAs in the pathobiology of glioblastoma (GBM), and their potential applications for GBM therapy. Significant advances in our understanding of the protean manifestations of ncRNAs have been made, allowing us to better decipher the molecular complexity of GBM. A large number of regulatory ncRNAs appear to have a greater influence on the molecular pathology of GBM than thought previously. Importantly, also, a range of therapeutic approaches are emerging whereby ncRNA-based systems may be used to molecularly target GBM. The most successful of these is RNA interference, and some of these strategies are being evaluated in ongoing clinical trials. However, a number of limitations exist in the clinical translation of ncRNA-based therapeutic systems, such as delivery mechanisms and cytotoxicity; concerted research endeavors are currently underway in an attempt to overcome these. Ongoing and future studies will determine the potential practical role for ncRNA-based therapeutic systems in the clinical management of GBM. These applications may be especially promising, given that current treatment options are limited and prognosis remains poor for this challenging malignancy.

miR-21-5p protects IL-1β-induced human chondrocytes from degradation

OBJECTIVE

Osteoarthritis (OA) is a prevalent degenerative disease caused by various factors. MicroRNAs are important regulators in OA. MiR-21-5p expression is decreased in OA cartilage, but the effects of modulating miR-21-5p on cartilage regeneration are unknown. Therefore, our aim was to investigate the effects of miR-21-5p on cartilage metabolism of OA chondrocytes.

DESIGN

We used IL-1β (10 ng/ml) to mimic OA chondrocytes. OA chondrocytes were transfected with miR-21-5p, the gene expression of COL2A1, MMP13, and ADAMTS5 was detected by qPCR. At the same time, COL2A1, MMP13, and ADAMTS5 were analyzed at the protein level by Western blot. CCK8 measured the cell's viability and SA-β-gal detected the cell's senescence.

RESULTS

Upregulation of miR-21-5p had increased COL2A1 expression and decreased MM P13 and ADAMTS5 expression, which were in accord with Western blot data. SA-β-gal activity significantly increased, the viability was decreased in OA chondrocytes, and upregulation of miR-21-5p can decrease the SA-β-gal activity and increase cell viability.

CONCLUSION

MiR-21-5p might be a potential disease-modifying compound in OA, as it promotes hyaline cartilage production. These results provided that novel insights into the important function in OA pathological development.

Roles of Non-Coding RNAs in Normal Human Brain Development, Brain Tumor, and Neuropsychiatric Disorders

One of modern biology’s great surprises is that the human genome encodes only ~20,000 protein-coding genes, which represents less than 2% of the total genome sequence, and the majority of them are transcribed into non-coding RNAs (ncRNAs). Increasing evidence has shown that ncRNAs, including miRNAs, long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play important roles in regulating a wide range of biological processes of the human brain. They not only regulate the pathogenesis of brain tumors, but also the development of neuropsychiatric diseases. This review provides an integrated overview of the roles of ncRNAs in normal human brain function, brain tumor development, and neuropsychiatric disease. We discussed the functions and molecular mechanisms of miRNAs, lncRNAs, and circRNAs in normal brain function and glioma, respectively, including those in exosome vesicles that can act as a molecular information carrier. We also discussed the regulatory roles of ncRNAs in the development of neuropsychiatric diseases. Lastly, we summarized the currently available platforms and tools that can be used for ncRNA identification and functional exploration in human diseases. This study will provide comprehensive insights for the roles of ncRNAs in human brain function and disease.

Oligonucleotide Therapeutics as a New Class of Drugs for Malignant Brain Tumors: Targeting mRNAs, Regulatory RNAs, Mutations, Combinations, and Beyond

Malignant brain tumors are rapidly progressive and often fatal owing to resistance to therapies and based on their complex biology, heterogeneity, and isolation from systemic circulation. Glioblastoma is the most common and most aggressive primary brain tumor, has high mortality, and affects both children and adults. Despite significant advances in understanding the pathology, multiple clinical trials employing various treatment strategies have failed. With much expanded knowledge of the GBM genome, epigenome, and transcriptome, the field of neuro-oncology is getting closer to achieve breakthrough-targeted molecular therapies. Current developments of oligonucleotide chemistries for CNS applications make this new class of drugs very attractive for targeting molecular pathways dysregulated in brain tumors and are anticipated to vastly expand the spectrum of currently targetable molecules. In this chapter, we will overview the molecular landscape of malignant gliomas and explore the most prominent molecular targets (mRNAs, miRNAs, lncRNAs, and genomic mutations) that provide opportunities for the development of oligonucleotide therapeutics for this class of neurologic diseases. Because malignant brain tumors focally disrupt the blood-brain barrier, this class of diseases might be also more susceptible to systemic treatments with oligonucleotides than other neurologic disorders and, thus, present an entry point for the oligonucleotide therapeutics to the CNS. Nevertheless, delivery of oligonucleotides remains a crucial part of the treatment strategy. Finally, synthetic gRNAs guiding CRISPR-Cas9 editing technologies have a tremendous potential to further expand the applications of oligonucleotide therapeutics and take them beyond RNA targeting.

Construction of Potential Glioblastoma Multiforme-Related miRNA-mRNA Regulatory Network

Background: Glioblastoma multiforme (GBM), the most common and aggressive human malignant brain tumor, is notorious for its limited treatment options and poor prognosis. MicroRNAs (miRNAs) are found to be involved in tumorigenesis of GBM. However, a comprehensive miRNA-mRNA regulatory network has still not been established.

Methods: A miRNA microarray dataset (GSE90603) was obtained from GEO database. Then, we employed GEO2R tool to perform differential expression analysis. Potential transcription factors and target genes of screened differentially expressed miRNAs (DE-miRNAs) were predicted. The GBM mRNA dataset were downloaded from TCGA database for identifying differentially expressed genes (DEGs). Next, GO annotation and KEGG pathway enrichment analysis was conducted. PPI network was then established, and hub genes were identified via Cytoscape software. The expression and prognostic roles of hub genes was further evaluated.

Results: Total 33 DE-miRNAs, consisting of 10 upregulated DE-miRNAs and 23 downregulated DE-miRNAs, were screened. SP1 was predicted to potentially regulate most of screened DE-miRNAs. Three thousand and twenty seven and 3,879 predicted target genes were obtained for upregulated and downregulated DE-miRNAs, respectively. Subsequently, 1,715 upregulated DEGs and 1,259 downregulated DEGs were identified. Then, 149 and 295 potential downregulated and upregulated genes commonly appeared in target genes of DE-miRNAs and DEGs were selected for GO annotation and KEGG pathway enrichment analysis. The downregulated genes were significantly enriched in cGMP-PKG signaling pathway and calcium signaling pathway whereas the upregulated genes were enriched in pathways in cancer and PI3K-Akt signaling pathway. Construction and analysis of PPI network showed that STXBP1 and TP53 were recognized as hub genes with the highest connectivity degrees. Expression analytic result of the top 20 hub genes in GBM using GEPIA database was generally identical with previous differential expression analysis for TCGA data. EGFR, PPP3CB, and MYO5A expression was significantly associated with patients' OS.

Conclusions: In this study, we established a potential GBM-related miRNA-mRNA regulatory network, which explores a comprehensive understanding of the molecular mechanisms and provides key clues in seeking novel therapeutic targets for GBM. In the future, more experiments need to be performed to validate our current findings.

APELA Expression in Glioma, and Its Association with Patient Survival and Tumor Grade

Glioblastoma (GBM) is the most common and deadliest primary adult brain tumor. Invasion, resistance to therapy, and tumor recurrence in GBM can be attributed in part to brain tumor-initiating cells (BTICs). BTICs isolated from various patient-derived xenografts showed high expression of the poorly characterized Apelin early ligand A (APELA) gene. Although originally considered to be a non-coding gene, the APELA gene encodes a protein that binds to the Apelin receptor and promotes the growth of human embryonic stem cells and the formation of the embryonic vasculature. We found that both APELA mRNA and protein are expressed at high levels in a subset of brain tumor patients, and that APELA is also expressed in putative stem cell niche in GBM tumor tissue. Analysis of APELA and the Apelin receptor gene expression in brain tumor datasets showed that high APELA expression was associated with poor patient survival in both glioma and glioblastoma, and APELA expression correlated with glioma grade. In contrast, gene expression of the Apelin receptor or Apelin was not found to be associated with patient survival, or glioma grade. Consequently, APELA may play an important role in glioblastoma tumorigenesis and may be a future therapeutic target.

Comprehensive data analysis for development of custom qRT-PCR miRNA assay for glioblastoma: a prevalidation study

Aim: Glioblastoma (GB) is one notable example of miRNA-modulated neoplasms. Given its unique expression signature, proper miRNA profiling can help discriminate between GB and other types of brain tumors. The current work aimed to develop a more GB-specific and applicable custom designed quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) miRNA assay. Materials & methods: A comprehensive data analysis of bioinformatics databases, previous literature and commercially available pre-designed miRNA PCR arrays within the market. Results: A highly enriched panel of 84 deregulated and GB-specific miRNAs has been developed. Conclusion: After validation of this newly developed array, it can not only save the researcher's time and effort, but can also have a potential diagnostic and/or prognostic role in GB, paving the road toward personalized medicine.

MiR-21, miR-34a, miR-125b, miR-181d and miR-648 levels inversely correlate with MGMT and TP53 expression in primary glioblastoma patients

INTRODUCTION

TP53 and MGMT alterations play a crucial role in glioblastoma (GB) pathogenesis. TP53 and MGMT function is affected by several pathologic mechanisms, such as point mutations or promoter methylation, which are well characterized. Expression of both genes can be regulated by other mechanisms as well, e.g., microRNAs (miRNAs). Moreover, cross-talk among various pathologic processes may occur, further affecting MGMT and TP53 functionality.

MATERIAL AND METHODS

In 49 GB patients, we analyzed the possible associations between TP53 and its miRNA regulators miR-125b, miR-21, and miR-34a, as well as MGMT and its miRNA regulators miR-181d and miR-648. We evaluated the possible influence of mutational and methylation status on the pre-identified associations.

RESULTS

In patients with immunohistochemistry-detected TP53 overexpression, expression levels of miR-34a and TP53 were negatively correlated (r = -0.56, p = 0.0195), and in patients with TP53 mutations, expression levels of TP53 and miR-21 were negatively correlated (r = -0.67, p = 0.0330). In patients with MGMT methylation, expression levels of MGMT were negatively correlated with miR-648 and miR-125b expression levels (r = -0.61, p = 0.0269 and r = -0.34, p = 0.0727, respectively).

CONCLUSIONS

Our findings demonstrate that selected miRNAs are significantly correlated with MGMT and TP53 levels, but the extent of this correlation differs regarding the TP53 and MGMT mutational and promoter methylation status.

MicroRNA-365 suppressed cell proliferation and migration via targeting PAX6 in glioblastoma

MicroRNAs (miRNAs) act an important role in the progression of tumor. In this study, we showed that the serum expression of miR-365 was downregulated in the glioblastoma compared with in the healthy controls. We also demonstrated that miR-365 expression was downregulated in glioblastoma tissues compared with the adjacent normal tissues. Overexpression of miR-365 suppressed the glioblastoma cell proliferation and migration. Moreover, ectopic expression of miR-365 promoted the expression of Ecadherin while inhibited the expression of N-cadherin and Vimentin in U87 cell. Furthermore, we identified PAX6 as a direct target gene of miR-365 in U87 cell. Overexpression of miR-365 suppressed glioblastoma cell proliferation and migration and epithelial-to-mesenchymal transition through inhibiting PAX6 expression. These results suggested that miR-365 played a tumor suppressor in glioblastoma.

Transcriptional and epigenetic mechanisms underlying astrocyte identity

Astrocytes play a significant role in coordinating neural development and provide critical support for the function of the CNS. They possess important adaptation capacities that range from their transition towards reactive astrocytes to their ability to undergo reprogramming, thereby revealing their potential to retain latent features of neural progenitor cells. We propose that the mechanisms underlying reactive astrogliosis or astrocyte reprogramming provide an opportunity for initiating neuronal regeneration, a process that is notably reduced in the mammalian nervous system throughout evolution. Conversely, this plasticity may also affect normal astrocytic functions resulting in pathologies ranging from neurodevelopmental disorders to neurodegenerative diseases and brain tumors. We postulate that epigenetic mechanisms linking extrinsic cues and intrinsic transcriptional programs are key factors to maintain astrocyte identity and function, and critically, to control the balance of regenerative and degenerative activity. Here, we will review the main evidences supporting this concept. We propose that unravelling the epigenetic and transcriptional mechanisms underlying the acquisition of astrocyte identity and plasticity, as well as understanding how these processes are modulated by the local microenvironment under specific threatening or pathological conditions, may pave the way to new therapeutic avenues for several neurological disorders including neurodegenerative diseases and brain tumors of astrocytic lineage.

Sulforaphane from Cruciferous Vegetables: Recent Advances to Improve Glioblastoma Treatment

Sulforaphane (SFN), an isothiocyanate (ITC) derived from cruciferous vegetables, particularly broccoli and broccoli sprouts, has been widely investigated due to its promising health-promoting properties in disease, and low toxicity in normal tissue. Although not yet fully understood, many mechanisms of anticancer activity at each step of cancer development have been attributed to this ITC. Given the promising data available regarding SFN, this review aimed to provide an overview on the potential activities of SFN related to the cellular mechanisms involved in glioblastoma (GBM) progression. GBM is the most frequent malignant brain tumor among adults and is currently an incurable disease due mostly to its highly invasive phenotype, and the poor efficacy of the available therapies. Despite all efforts, the median overall survival of GBM patients remains approximately 1.5 years under therapy. Therefore, there is an urgent need to provide support for translating the progress in understanding the molecular background of GBM into more complex, but promising therapeutic strategies, in which SFN may find a leading role.

c-Fos/microRNA-18a feedback loop modulates the tumor growth via HMBOX1 in human gliomas

Glioma is one of the most aggressive and lethal human cancers in central nervous system (CNS). Recent studies have identified many dysregulated microRNAs (miRNA, miR) in human glioma, which are a class of small non-coding RNA molecules. Increasing data have shown that miR-18a plays significant roles in several tumors. However, its effects on glioma are unclear. In this study, we found the elevated expression of c-Fos and miR-18a in tissues of human glioma patients and glioma cells. Then the miR-18a inhibitor or c-Fos siRNA were transfected into glioma cells line H4 to determine their effects on H4 cells. MTT assay showed that both miR-18a inhibitor and si-c-Fos suppressed the H4 cell proliferation. Transwell assay showed the reduced cell migration by miR-18a inhibitor and si-c-Fos in H4 cells. The increased level of H4 cells apoptosis by miR-18a inhibitor and si-c-Fos was also determined. Moreover, knockout of c-Fos decreased the miR-18a level, while miR-18a inhibitor reduced the c-Fos level in H4 cells. Added with the results of ChIP assay, this report showed a positive feedback between c-Fos and miR-18a. Finally, luciferase assay showed that HMBOX1 was directly targeted by miR-18a in H4 cells, and the HMBOX1 siRNA reversed the effects of miR-18a inhibitor on cell proliferation, migration and apoptosis of H4 cells. In conclusion, our study determine that c-Fos/miR-18a feedback loop promotes the tumor growth of gliomas by HMBOX1, providing important clues for understanding the key roles of transcription factor mediated mRNA-miRNA functional network in the regulation of gliomas.

Simultaneous miRNA and mRNA transcriptome profiling of glioblastoma samples reveals a novel set of OncomiR candidates and their target genes

Although glioblastomas are common, there remains a need to elucidate the underlying mechanisms behind their initiation and progression and identify molecular pathways for improving treatment. In this study, sixteen fresh-frozen glioblastoma samples and seven samples of healthy brain tissues were analyzed with miRNA and whole transcriptome microarray chips. Candidate miRNAs and mRNAs were selected to validate expression in fifty patient samples in total with the criteria of abundance, relevance and prediction scores. miRNA and target mRNA relationships were assessed by inhibiting selected miRNAs in glioblastoma cells. Functional tests have been conducted in order to see the effects of miRNAs on invasion, migration and apoptosis of GBM cells. Analyses were carried out to determine correlations between selected molecules and clinicopathological features. 1332 genes and 319 miRNAs were found to be dysregulated by the microarrays. The results were combined and analyzed with Transcriptome Analysis Console 3 software and the DAVID online database. Primary differential pathways included Ras, HIF-1, MAPK signaling and cell adhesion. OncomiR candidates 21-5p, 92b-3p, 182-5p and 339-5p for glioblastoma negatively correlated with notable mRNA targets both in tissues and in in vitro experiments. miR-21-5p and miR-339-5p significantly affected migration, invasion and apoptosis of GBM cells in vitro. Significant correlations with overall survival, tumor volume, recurrence and age at diagnosis were discovered. In this article we present valuable integrated microarray analysis of glioblastoma samples regarding miRNA and gene-expression levels. Notable biomarkers and miRNA-mRNA interactions have been identified, some of which correlated with clinicopathological features in our cohort.

Emerging role of exosome signalling in maintaining cancer stem cell dynamic equilibrium

Cancer stem cells (CSCs) are a small subset of heterogeneous cells existed in tumour tissues or cancer cell lines with self-renewal and differentiation potentials. CSCs were considered to be responsible for the failure of conventional therapy and tumour recurrence. However, CSCs are not a static cell population, CSCs and non-CSCs are maintained in dynamic interconversion state by their self-differentiation and dedifferentiation. Therefore, targeting CSCs for cancer therapy is still not enough,exploring the mechanism of dynamic interconversion between CSCs and non-CSCs and blocking the interconversion seems to be imperative. Exosomes are 30-100 nm size in diameter extracellular vesicles (EVs) secreted by multiple living cells into the extracellular space. They contain cell-state-specific bioactive materials, including DNA, mRNA, ncRNA, proteins, lipids, etc. with their specific surface markers, such as, CD63, CD81, Alix, Tsg101, etc. Exosomes have been considered as information carriers in cell communication between cancer cells and non-cancer cells, which affect gene expressions and cellular signalling pathways of recipient cells by delivering their contents. Now that exosomes acted as information carriers, whether they played role in maintaining dynamic equilibrium state between CSCs and non-CSCs and their mechanism of activity are unknown. This review summarized the current research advance of exosomes' role in maintaining CSC dynamic interconversion state and their possible mechanism of action, which will provide a better understanding the contribution of exosomes to dedifferentiation and stemness acquisition of non-CSCs, and highlight that exosomes might be taken as the attractive target approaches for cancer therapeutics.

MicroRNA-21 in the Pathogenesis of Traumatic Brain Injury

MicroRNAs (miRNAs), an abundant class of small noncoding RNA molecules, which regulate gene expression by functioning as post-transcriptional regulatory factors, have been identified as key components of traumatic brain injury (TBI) progression. MicroRNA-21 (miR-21) is a recently identified typical miRNA that is involved in the signaling pathways of inflammation, neuronal apoptosis, reactive gliosis, disruption of blood brain barrier, angiogenesis and recovery process induced by physical exercises in TBI. Hence, miR-21 is now considered as a potential therapeutic target of TBI. We review the correlative literature and research progress regarding the roles of miR-21 in TBI in this article.

Exosomes and their implications in central nervous system tumor biology

Exosomes are 20-100 nm cellular derived vesicles that upon discovery, were thought to be a form of cellular recycling of intracellular contents. More recently, these vesicles are under investigation for their purported significant roles in intercellular communication in both healthy and diseased states. Herein, we focus on the secretion of exosomes associated with glioblastoma, as most exosome studies on brain tumors have been performed in this tumor type. However, we included exosomes secreted from other forms of brain tumors for comparison as available. Exosomes contain intracellular content that can be transferred to other cells in the tumor or to cells of the immune system and endothelial cells. These recipient cells may subsequently take on oncogenic properties, including therapeutic resistance, cancer progression, and angiogenesis. Genetic components (DNA, RNA and miRNA) of the cell of origin may be included in the secreted exosomes. The presence of genetic material in the exosomes could serve as a biomarker for mutations in tumors, potentially leading to novel treatment strategies. In the last decade, exosomes have been identified as having a major impact on multiple aspects of medicine and tumor biology, and appear to be primed for a critical position in cancer diagnosis, prognosis, and treatment.

Snail-overexpressing Cancer Cells Promote M2-Like Polarization of Tumor-Associated Macrophages by Delivering MiR-21-Abundant Exosomes

Epithelial-mesenchymal transition (EMT) is a major event during cancer progression and metastasis; however, the definitive role of EMT in remodeling tumor microenvironments (TMEs) is unclear. Tumor-associated macrophages (TAMs) are a major type of host immune cells in TMEs, and they perform a wide range of functions to regulate tumor colonization and progression by regulating tumor invasiveness, local tumor immunity, and angiogenesis. TAMs are considered to have an M2-like, i.e., alternatively activated, phenotype; however, how these EMT-undergoing cancer cells promote M2 polarization of TAMs as a crucial tumor-host interplay during cancer progression is unclear. In this study, we investigated the mechanism of EMT-mediated TAM activation. Here, we demonstrate that the EMT transcriptional factor Snail directly activates the transcription of MIR21 to produce miR-21-abundant tumor-derived exosomes (TEXs). The miR-21-containing exosomes were engulfed by CD14⁺ human monocytes, suppressing the expression of M1 markers and increasing that of M2 markers. Knockdown of miR-21 in Snail-expressing human head and neck cancer cells attenuated the Snail-induced M2 polarization, angiogenesis, and tumor growth. In head and neck cancer samples, a high expression of miR-21 was correlated with a higher level of SNAI1 and the M2 marker MRC1. This study elucidates the mechanism of EMT-mediated M2 polarization through delivery of the miR-21-abundant exosomes, which may serve as a candidate biomarker of tumor progression and provide a potential target for intercepting EMT-mediated TME remodeling.

IGF-binding proteins

Insulin-like growth factor-binding proteins (IGFBPs) 1-6 bind IGFs but not insulin with high affinity. They were initially identified as serum carriers and passive inhibitors of IGF actions. However, subsequent studies showed that, although IGFBPs inhibit IGF actions in many circumstances, they may also potentiate these actions. IGFBPs are widely expressed in most tissues, and they are flexible endocrine and autocrine/paracrine regulators of IGF activity, which is essential for this important physiological system. More recently, individual IGFBPs have been shown to have IGF-independent actions. Mechanisms underlying these actions include (i) interaction with non-IGF proteins in compartments including the extracellular space and matrix, the cell surface and intracellular space, (ii) interaction with and modulation of other growth factor pathways including EGF, TGF-β and VEGF, and (iii) direct or indirect transcriptional effects following nuclear entry of IGFBPs. Through these IGF-dependent and IGF-independent actions, IGFBPs modulate essential cellular processes including proliferation, survival, migration, senescence, autophagy and angiogenesis. They have been implicated in a range of disorders including malignant, metabolic, neurological and immune diseases. A more complete understanding of their cellular roles may lead to the development of novel IGFBP-based therapeutic opportunities.

Computational identification of specific genes for glioblastoma stem-like cells identity

Glioblastoma, the most malignant brain cancer, contains self-renewing, stem-like cells that sustain tumor growth and therapeutic resistance. Identifying genes promoting stem-like cell differentiation might unveil targets for novel treatments. To detect them, here we apply SWIM - a software able to unveil genes (named switch genes) involved in drastic changes of cell phenotype - to public datasets of gene expression profiles from human glioblastoma cells. By analyzing matched pairs of stem-like and differentiated glioblastoma cells, SWIM identified 336 switch genes, potentially involved in the transition from stem-like to differentiated state. A subset of them was significantly related to focal adhesion and extracellular matrix and strongly down-regulated in stem-like cells, suggesting that they may promote differentiation and restrain tumor growth. Their expression in differentiated cells strongly correlated with the down-regulation of transcription factors like OLIG2, POU3F2, SALL2, SOX2, capable of reprogramming differentiated glioblastoma cells into stem-like cells. These findings were corroborated by the analysis of expression profiles from glioblastoma stem-like cell lines, the corresponding primary tumors, and conventional glioma cell lines. Switch genes represent a distinguishing feature of stem-like cells and we are persuaded that they may reveal novel potential therapeutic targets worthy of further investigation.

MicroRNA-21 plays a pivotal role in the oocyte-secreted factor-induced suppression of cumulus cell apoptosis

It is known that oocytes and cumulus cells (CCs) are more resistant to apoptosis than other compartments of the antral follicle. However, although oocyte-secreted factors (OSFs) have been found to be involved in suppressing bovine CC apoptosis, little is known about the intracellular mechanisms by which OSFs render CCs resistant to apoptosis. Here, we show that coculture with mouse or pig cumulus-denuded oocytes, culture with recombinant mouse growth differentiation factor-9 (GDF-9), or culture in pig oocyte-conditioned medium (POCM) significantly inhibited CC apoptosis of mouse oocytectomized cumulus oophorus complexes (OOXs). The POCM contained both GDF-9 and bone morphogenetic protein-15, and their levels remained constant during culture of OOXs. The level of microRNA-21 (miR-21) was significantly lower in OOXs than in COCs after culture in a simplified α-MEM medium, but increased significantly when OOXs were cultured with GDF-9 or in POCM. The level of miR-21 in OSF-treated CCs was correlated with that of Dicer1 but not that of Drosha mRNA. Inhibiting activin receptor-like kinase 5 or SMAD3 completely abolished the beneficial effects of GDF-9 or POCM on CC apoptosis and miR-21 levels. Up- and downregulating miR-21 expression significantly reduced and increased CC apoptosis, respectively. The OSF-upregulated miR-21 expression suppressed CC apoptosis with activation of the PI3K/Akt signaling. In conclusion, miR-21 plays a pivotal role in the OSF suppression of CC apoptosis. OSFs upregulated miR-21 expression through the TGF-β superfamily signaling, which worked through DICER. MicroRNA-21 prevented apoptosis via the PI3K/Akt signaling.

Targeted nanoparticle delivery of therapeutic antisense microRNAs presensitizes glioblastoma cells to lower effective doses of temozolomide in vitro and in a mouse model

Temozolomide (TMZ) chemotherapy for glioblastoma (GBM) is generally well tolerated at standard doses but it can cause side effects. GBMs overexpress microRNA-21 and microRNA-10b, two known oncomiRs that promote cancer development, progression and resistance to drug treatment. We hypothesized that systemic injection of antisense microRNAs (antagomiR-21 and antagomiR-10b) encapsulated in cRGD-tagged PEG-PLGA nanoparticles would result in high cellular delivery of intact functional antagomiRs, with consequent efficient therapeutic response and increased sensitivity of GBM cells to lower doses of TMZ. We synthesized both targeted and non-targeted nanoparticles, and characterized them for size, surface charge and encapsulation efficiency of antagomiRs. When using targeted nanoparticles in U87MG and Ln229 GBM cells, we showed higher uptake-associated improvement in sensitivity of these cells to lower concentrations of TMZ in medium. Co-inhibition of microRNA-21 and microRNA-10b reduced the number of viable cells and increased cell cycle arrest at G2/M phase upon TMZ treatment. We found a significant increase in expression of key target genes for microRNA-21 and microRNA-10b upon using targeted versus non-targeted nanoparticles. There was also significant reduction in tumor volume when using TMZ after pre-treatment with loaded nanoparticles in human GBM cell xenografts in mice. In vivo targeted nanoparticles plus different doses of TMZ showed a significant therapeutic response even at the lowest dose of TMZ, indicating that preloading cells with antagomiR-21 and antagomiR-10b increases cellular chemosensitivity towards lower TMZ doses. Future clinical applications of this combination therapy may result in improved GBM response by using lower doses of TMZ and reducing nonspecific treatment side effects.

Identification of microRNAs associated with glioma diagnosis and prognosis

The sensitivity and specificity of microRNAs (miRNAs) for diagnosing glioma are controversial. We therefore performed a meta-analysis to systematically identify glioma-associated miRNAs. We initially screened five miRNA microarray datasets to evaluate the differential expression of miRNAs between glioma and normal tissues. We next compared the expression of the miRNAs in different organs and tissues to assess the sensitivity and specificity of the differentially expressed miRNAs in the diagnosis of glioma. Finally, pathway analysis was performed using GeneGO. We identified 27 candidate miRNAs associated with glioma initiation, progression, and patient prognosis. Sensitivity and specificity analysis indicated miR-15a, miR-16, miR-21, miR-23a, and miR-9 were up-regulated, while miR-124 was down-regulated in glioma. Ten signaling pathways showed the strongest association with glioma development and progression: the p53 pathway feedback loops 2, Interleukin signaling pathway, Toll receptor signaling pathway, Parkinson's disease, Notch signaling pathway, Cadherin signaling pathway, Apoptosis signaling pathway, VEGF signaling pathway, Alzheimer disease-amyloid secretase pathway, and the FGF signaling pathway. Our results indicate that the integration of miRNA, gene, and protein expression data can yield valuable biomarkers for glioma diagnosis and treatment. Indeed, six of the miRNAs identified in this study may be useful diagnostic and prognostic biomarkers in glioma.

Oncogenomic disruptions in arsenic-induced carcinogenesis

Chronic exposure to arsenic affects more than 200 million people worldwide, and has been associated with many adverse health effects, including cancer in several organs. There is accumulating evidence that arsenic biotransformation, a step in the elimination of arsenic from the human body, can induce changes at a genetic and epigenetic level, leading to carcinogenesis. At the genetic level, arsenic interferes with key cellular processes such as DNA damage-repair and chromosomal structure, leading to genomic instability. At the epigenetic level, arsenic places a high demand on the cellular methyl pool, leading to global hypomethylation and hypermethylation of specific gene promoters. These arsenic-associated DNA alterations result in the deregulation of both oncogenic and tumour-suppressive genes. Furthermore, recent reports have implicated aberrant expression of non-coding RNAs and the consequential disruption of signaling pathways in the context of arsenic-induced carcinogenesis. This article provides an overview of the oncogenomic anomalies associated with arsenic exposure and conveys the importance of non-coding RNAs in the arsenic-induced carcinogenic process.

Neural progenitor fate decision defects, cortical hypoplasia and behavioral impairment in Celsr1-deficient mice

The development of the cerebral cortex is a tightly regulated process that relies on exquisitely coordinated actions of intrinsic and extrinsic cues. Here, we show that the communication between forebrain meninges and apical neural progenitor cells (aNPC) is essential to cortical development, and that the basal compartment of aNPC is key to this communication process. We found that Celsr1, a cadherin of the adhesion G protein coupled receptor family, controls branching of aNPC basal processes abutting the meninges and thereby regulates retinoic acid (RA)-dependent neurogenesis. Loss-of-function of Celsr1 results in a decreased number of endfeet, modifies RA-dependent transcriptional activity and biases aNPC commitment toward self-renewal at the expense of basal progenitor and neuron production. The mutant cortex has a reduced number of neurons, and Celsr1 mutant mice exhibit microcephaly and behavioral abnormalities. Our results uncover an important role for Celsr1 protein and for the basal compartment of neural progenitor cells in fate decision during the development of the cerebral cortex.

MiRNA203 suppresses the expression of protumorigenic STAT1 in glioblastoma to inhibit tumorigenesis

MicroRNAs (miRNAs) play critical roles in regulating cancer cell proliferation, migration, survival and sensitivity to chemotherapy. The potential application of using miRNAs for cancer prognosis holds great promise but miRNAs with predictive value remain to be identified and underlying mechanisms of how they promote or suppress tumorigenesis are not completely understood. Here, we show a strong correlation between miR203 expression and brain cancer patient survival. Low miR203 expression is found in subsets of brain cancer patients, especially glioblastoma. Ectopic miR203 expression in glioblastoma cell lines inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by interferon or temozolomide in vitro, and inhibited tumorigenesis in vivo. We further show that STAT1 is a direct functional target of miR203, and miR203 level is negatively correlated with STAT1 expression in brain cancer patients. Knockdown of STAT1 expression mimicked the effect of overexpression of miR203 in glioblastoma cell lines, and inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by IFN or temozolomide in vitro, and inhibited glioblastoma tumorigenesis in vivo. High STAT1 expression significantly correlated with poor survival in brain cancer patients. Mechanistically, we found that enforced miR203 expression in glioblastoma suppressed STAT1 expression directly, as well as that of a number of STAT1 regulated genes. Taken together, our data suggest that miR203 acts as a tumor suppressor in glioblastoma by suppressing the pro-tumorigenic action of STAT1. MiR203 may serve as a predictive biomarker and potential therapeutic target in subsets of cancer patients with low miR203 expression.

What Happened to the IGF Binding Proteins?

Insulinlike growth factor (IGF) binding proteins (IGFBPs) 1 to 6 are high-affinity regulators of IGF activity. They generally inhibit IGF actions by preventing binding to the IGF-I receptor but can also enhance their actions under some conditions. Posttranslational modifications such as glycosylation and phosphorylation modulate IGFBP properties, and IGFBP proteolysis results in IGF release. IGFBPs have more recently been shown to have IGF-independent actions. A number of mechanisms are involved, including modulation of other growth factor pathways, nuclear localization and transcriptional regulation, interaction with the sphingolipid pathway, and binding to non-IGF biomolecules in the extracellular space and matrix, on the cell surface and intracellularly. IGFBPs modulate important biological processes, including cell proliferation, survival, migration, senescence, autophagy, and angiogenesis. Their actions have been implicated in growth, metabolism, cancer, stem cell maintenance and differentiation, and immune regulation. Recent studies have shown that epigenetic mechanisms are involved in the regulation of IGFBP abundance. A more complete understanding of IGFBP biology is necessary to further define their cellular roles and determine their therapeutic potential.

Extracellular miRNA-21 as a novel biomarker in glioma: Evidence from meta-analysis, clinical validation and experimental investigations

Evidence is accumulating highlighting the importance of extracellular miRNA as a novel biomarker for diagnosing various kinds of malignancies. MiR-21 is one of the most studied miRNAs and is over-expressed in cancer tissues. To explore the clinical implications and secretory mechanisms of extracellular miR-21, we firstly meta-analyzed the diagnostic efficiency of extracellular miR-21 in different cancer types. Eighty-one studies based on 59 articles were finally included. In our study, extracellular miR-21 was observed to exhibit an outstanding diagnostic accuracy in detecting brain cancer (area under the summary receiver operating characteristic curve or AUC = 0.94), and this accuracy was more obvious in glioma diagnosis (AUC = 0.95). Our validation study (n = 45) further confirmed the diagnostic and prognostic role of miR-21 in cerebrospinal fluid (CSF) for glioma. These findings inspired us to explore the biological function of miR-21. We next conducted mechanistic investigations to explain the secretory mechanisms of extracellular miR-21 in glioma. TGF-β/Smad3 signaling was identified to participate in mediating the release of miR-21 from glioma cells. Further targeting TGF-β/Smad3 signaling using galunisertib, an inhibitor of the TGF-β type I receptor kinase, can attenuate the secretion of miR-21 from glioma cells. Taken together, CSF-based miR-21 might serve as a potential biomarker for diagnosing brain cancer, especially for patients with glioma. Moreover, extracellular levels of miR-21 were affected by exogenous TGF-β activity and galunisertib treatment.

MicroRNA203a suppresses glioma tumorigenesis through an ATM-dependent interferon response pathway

Glioblastoma (GBM) is a deadly and incurable brain tumor. Although microRNAs (miRNAs) play critical roles in regulating the cancer cell phenotype, the underlying mechanisms of how they regulate tumorigenesis are incompletely understood. We previously showed that miR-203a is expressed at relatively low levels in GBM patients, and ectopic miR-203a expression in GBM cell lines inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by interferon (IFN) or temozolomide in vitro, and inhibited GBM tumorigenesis in vivo. Here we show that ectopic expression of miR-203a in GBM cell lines promotes the IFN response pathway as evidenced by increased IFN production and IFN-stimulated gene (ISG) expression, and high basal tyrosine phosphorylation of multiple STAT proteins. Importantly, we identified that miR-203a directly suppressed the protein levels of ataxia-telangiectasia mutated (ATM) kinase that negatively regulates IFN production. We found that high ATM expression in GBM correlates with poor patient survival and that ATM expression is inversely correlated with miR-203a expression. Knockout of ATM expression and inhibition of ATM function in GBM cell lines inhibited cell proliferation and migration, increased sensitivity to apoptosis induced by therapeutic agents in vitro, and markedly suppressed GBM tumor growth and promoted animal survival. In contrast, restoring ATM levels in GBM cells ectopically expressing miR-203a increased tumorigenicity and decreased animal survival. Our study suggests that low miR-203a expression in GBM suppresses the interferon response through an ATM-dependent pathway.

CRISPR-Cas9 screen reveals a MYCN-amplified neuroblastoma dependency on EZH2

Pharmacologically difficult targets, such as MYC transcription factors, represent a major challenge in cancer therapy. For the childhood cancer neuroblastoma, amplification of the oncogene MYCN is associated with high-risk disease and poor prognosis. Here, we deployed genome-scale CRISPR-Cas9 screening of MYCN-amplified neuroblastoma and found a preferential dependency on genes encoding the polycomb repressive complex 2 (PRC2) components EZH2, EED, and SUZ12. Genetic and pharmacological suppression of EZH2 inhibited neuroblastoma growth in vitro and in vivo. Moreover, compared with neuroblastomas without MYCN amplification, MYCN-amplified neuroblastomas expressed higher levels of EZH2. ChIP analysis showed that MYCN binds at the EZH2 promoter, thereby directly driving expression. Transcriptomic and epigenetic analysis, as well as genetic rescue experiments, revealed that EZH2 represses neuronal differentiation in neuroblastoma in a PRC2-dependent manner. Moreover, MYCN-amplified and high-risk primary tumors from patients with neuroblastoma exhibited strong repression of EZH2-regulated genes. Additionally, overexpression of IGFBP3, a direct EZH2 target, suppressed neuroblastoma growth in vitro and in vivo. We further observed strong synergy between histone deacetylase inhibitors and EZH2 inhibitors. Together, these observations demonstrate that MYCN upregulates EZH2, leading to inactivation of a tumor suppressor program in neuroblastoma, and support testing EZH2 inhibitors in patients with MYCN-amplified neuroblastoma.

TGF-â1-induced miR-503 controls cell growth and apoptosis by targeting PDCD4 in glioblastoma cells

Aberrant expression of microRNAs hae been shown to be closely associated with glioblastoma cell proliferation, apoptosis and drug resistance. However, mechanisms underlying the role of mcroRNAs in glioblastoma cell growth and apoptosis are not fully understood. In this study, we report that miR-503 is overexpressed in glioblastoma tissue compared with normal human brain tissue. Mechanistically, miR-503 can be induced by TGF-â1 at the transcriptional level by binding the smad2/3 binding elements in the promoter. Ectopic overexpression of miR-503 promotes cell growth and inhibits apoptosis by targeting PDCD4. In contrast, inhibition of miR-503 reduces cell growth. Furthermore, miR-503 inhibitor augments the growth inhibitory effect of temozolomide in glioblastoma cells. These results establish miR-503 as a promising molecular target for glioblastoma therapy.

MiR-21: A key player in glioblastoma pathogenesis

Glioblastoma multiform (GBM) is one of common cancers worldwide which has high rate among various populations. Despite serious efforts worldwide, GBM remains a deadly disease which is associated with poor prognosis. Multiple lines evidence indicated that deregulation of a variety of cellular and molecular pathways are related with GBM pathogenesis. Among of various targets involved in GBM pathogenesis, microRNAs (miRNAs) have been emerged as targets which deregulation of them are related with various stages of GBM. These molecules are small non-coding RNAs which could affect on a variety of cellular and molecular pathways involved in GBM. It has been showed that deregulation of them are associated with initiation and progression of GBM. MiR-21 is one of important miRNAs involved in GBM pathogenesis. A large number studies indicated that this miRNA could affect on a variety of cellular and molecular pathways such as insulin-like growth factor (IGF)-binding protein-3 (IGFBP3), RECK, and TIMP3. Exosomes are one of important players in GBM pathogenesis. Among of various exosomes, exosomal miR-21 may has key roles in GBM pathogenesis. These findings indicated that miR-21 has critical roles in GBM pathogenesis and could be used as diagnostic and therapeutic biomarkers for GBM patients. Here, we summarized the roles of miR-21 and exosomal miR-21 in GBM pathogenesis. Moreover, we highlighted utilization of miR-21 as diagnostic and therapeutic biomarker for GBM patients.

MicroRNA-1468-5p inhibits glioma cell proliferation and induces cell cycle arrest by targeting RRM1

MicroRNAs are associated with different types of cancers. In this study, we found that miR-1468-5p could inhibit growth and cell cycle progression in glioma by targeting ribonucleotide reductase large subunit M1 (RRM1). First, we analyzed miR-1468-5p expression in different glioma grades and the prognostic significance of its expression in glioblastoma multiform patients from the Chinese Glioma Genome Atlas. Then, we expressed miR-1468-5p in U87 and U251 cells and assessed the effects on proliferation and cell cycle progression using cell counting kit-8, colony formation, EdU and flow cytometry assays. Western blotting and luciferase reporter assays identified RRM1 as a novel direct target of miR-1468-5p. Experiments to determine the role of RRM1 in glioma showed that RRM1 expression was significantly higher in glioma than in normal brain tissues, and silencing RRM1 with small-interfering RNAs decreased proliferation and suppressed cell cycle progression, which indicated that RRM1 had pro-tumor functions. miR-1468-5p overexpression suppressed RRM1 expression, reduced glioma cell proliferation and induced cell cycle arrest, which was partially rescued by forced RRM1 expression. In summary, our study revealed that the regulatory mechanism of miR-1468-5p in glioma cell cycle progression involved direct regulation of RRM1 expression, suggesting that RRM1 may be a potential therapeutic target for glioma.

A Comprehensive Review of Genomics and Noncoding RNA in Gliomas

Glioblastoma (GBM) is the most malignant primary adult brain tumor. In spite of our greater understanding of the biology of GBMs, clinical outcome of GBM patients remains poor, as their median survival with best available treatment is 12 to 18 months. Recent efforts of The Cancer Genome Atlas (TCGA) have subgrouped patients into 4 molecular/transcriptional subgroups: proneural, neural, classical, and mesenchymal. Continuing efforts are underway to provide a comprehensive map of the heterogeneous makeup of GBM to include noncoding transcripts, genetic mutations, and their associations to clinical outcome. In this review, we introduce key molecular events (genetic and epigenetic) that have been deemed most relevant as per studies such as TCGA, with a specific focus on noncoding RNAs such as microRNAs (miRNA) and long noncoding RNAs (lncRNA). One of our main objectives is to illustrate how miRNAs and lncRNAs play a pivotal role in brain tumor biology to define tumor heterogeneity at molecular and cellular levels. Ultimately, we elaborate how radiogenomics-based predictive models can describe miRNA/lncRNA-driven networks to better define heterogeneity of GBM with clinical relevance.

Integration of MicroRNA, mRNA, and Protein Expression Data for the Identification of Cancer-Related MicroRNAs

MicroRNAs (miRNAs) are responsible for the regulation of target genes involved in various biological processes, and may play oncogenic or tumor suppressive roles. Many studies have investigated the relationships between miRNAs and their target genes, using mRNA and miRNA expression data. However, mRNA expression levels do not necessarily represent the exact gene expression profiles, since protein translation may be regulated in several different ways. Despite this, large-scale protein expression data have been integrated rarely when predicting gene-miRNA relationships. This study explores two approaches for the investigation of gene-miRNA relationships by integrating mRNA expression and protein expression data. First, miRNAs were ranked according to their effects on cancer development. We calculated influence scores for each miRNA, based on the number of significant mRNA-miRNA and protein-miRNA correlations. Furthermore, we constructed modules containing mRNAs, proteins, and miRNAs, in which these three molecular types are highly correlated. The regulatory interactions between miRNA and genes in these modules have been validated based on the direct regulations, indirect regulations, and co-regulations through transcription factors. We applied our approaches to glioblastomas (GBMs), ranked miRNAs depending on their effects on GBM, and obtained 52 GBM-related modules. Compared with the miRNA rankings and modules constructed using only mRNA expression data, the rankings and modules constructed using mRNA and protein expression data were shown to have better performance. Additionally, we experimentally verified that miR-504, highly ranked and included in the identified modules, plays a suppressive role in GBM development. We demonstrated that the integration of both expression profiles allows a more precise analysis of gene-miRNA interactions and the identification of a higher number of cancer-related miRNAs and regulatory mechanisms.