Potential role of miRNAs and their inhibitors in glioma treatment

MiR-95-3p acts as a prognostic marker and promotes cervical cancer progression by targeting VCAM1

BACKGROUND

Cervical cancer patients have a high risk of metastasis and a poor prognosis with shorter disease-free survival. Thus, novel biomarkers and feasible therapies urgently need to be discovered. Previous studies have shown that miR-95-3p plays crucial roles in several cancer types. However, the roles of miR-95-3p in cervical cancer remain unknown.

METHODS

The micro ribonucleic acid (miRNA) expression data and clinical characteristics of cervical cancer samples were downloaded from The Cancer Genome Atlas (TCGA) database. Univariate and multivariate Cox regression analyses were conducted to identify the prognostic-related miRNAs. The potential target genes of miR-95-3p were predicted by the TargetScan database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted to explore the target gene of miR-95-3p. The effects of miR-95-3p inhibition and overexpression on cell proliferation were inspected by cell counting kit-8 (CCK-8) assays and cell colony formation assays. Wound-healing assays and transwell assays were also used to examine cell migration ability in HeLa and SiHa cells.

RESULTS

MiR-95-3p was the only miRNA significantly associated with the poor prognosis of cervical squamous cell carcinoma. A further analysis suggested that vascular cell adhesion molecule 1 (VCAM1) is a target gene of miR-95-3p in cervical cancer, and miR-95-3p promotes the malignant behavior of cervical cancer cells by inhibiting the expression of VCAM1. The CCK-8 and cell colony assays showed that miR-95-3p downregulation significantly suppressed cell proliferation in the HeLa and SiHa cells. The transwell and wound-healing assays showed that miR-95-3p inhibition suppressed cell migration in the HeLa and SiHa cells. Further the Western blot analysis and the quantitative real-time-polymerase chain reaction (qRT-PCR) showed that the knockdown of miR-95-3p in HeLa cells resulted in increased VCAM1 expression. And VCAM1 was highly expressed in the paired adjacent normal cervical epithelium tissue samples, but lowly expressed in the cervical tumor tissue samples.

CONCLUSIONS

Our study was the first to show that miR-95-3p could serve as a prognostic biomarker of cervical cancer. Mechanistically, we discovered that miR-95-3p inhibited the expression of the cell adhesion molecule VCAM1 and thus promoted further tumor progression.

A 4-miRNA signature predicts the therapeutic outcome of glioblastoma

Multimodal therapy of glioblastoma (GBM) reveals inter-individual variability in terms of treatment outcome. Here, we examined whether a miRNA signature can be defined for the a priori identification of patients with particularly poor prognosis.

FFPE sections from 36 GBM patients along with overall survival follow-up were collected retrospectively and subjected to miRNA signature identification from microarray data. A risk score based on the expression of the signature miRNAs and cox-proportional hazard coefficients was calculated for each patient followed by validation in a matched GBM subset of TCGA. Genes potentially regulated by the signature miRNAs were identified by a correlation approach followed by pathway analysis.

A prognostic 4-miRNA signature, independent of MGMT promoter methylation, age, and sex, was identified and a risk score was assigned to each patient that allowed defining two groups significantly differing in prognosis (p-value: 0.0001, median survival: 10.6 months and 15.1 months, hazard ratio = 3.8). The signature was technically validated by qRT-PCR and independently validated in an age- and sex-matched subset of standard-of-care treated patients of the TCGA GBM cohort (n=58). Pathway analysis suggested tumorigenesis-associated processes such as immune response, extracellular matrix organization, axon guidance, signalling by NGF, GPCR and Wnt. Here, we describe the identification and independent validation of a 4-miRNA signature that allows stratification of GBM patients into different prognostic groups in combination with one defined threshold and set of coefficients that could be utilized as diagnostic tool to identify GBM patients for improved and/or alternative treatment approaches.

MiRNA expression profiling in human gliomas: upregulated miR-363 increases cell survival and proliferation

The role of microRNAs (miRNAs) in glioma biology is increasingly recognized. To investigate the regulatory mechanisms governing the malignant signature of gliomas with different grades of malignancy, we analyzed miRNA expression profiles in human grade I-IV tumor samples and primary glioma cell cultures. Multiplex real-time PCR was used to profile miRNA expression in a set of World Health Organization (WHO) grade I (pilocytic astrocytoma), II (diffuse fibrillary astrocytoma), and IV (glioblastoma multiforme) astrocytic tumors and primary glioma cell cultures. Primary glioma cell cultures were used to evaluate the effect of transfection of specific miRNAs and miRNA inhibitors. miRNA microarray showed that a set of miRNAs was consistently upregulated in all glioma samples. miR-363 was upregulated in all tumor specimens and cell lines, and its expression correlated with tumor grading. The transfection of glioma cells with the specific inhibitor of miR-363 increased the expression level of tumor suppressor growth-associated protein 43 (GAP-43). Transfection of miR-363 induced cell survival, while inhibition of miR-363 significantly reduced glioma cell viability. Furthermore, miRNA-363 inhibition induced the downregulation of AKT, cyclin-D1, matrix metalloproteinase (MMP)-2, MMP-9, and Bcl-2 and upregulation of caspase 3. Together, these data suggest that the upregulation of miR-363 may play a role in malignant glioma signature.

High expression of CXCR3 is an independent prognostic factor in glioblastoma patients that promotes an invasive phenotype

Chemokines are a superfamily of small heparin-binding cytokines that induce leukocytes to migrate to sites of inflammation or injury through interacting with specific transmembrane G protein-coupled receptors. Currently, attention is focused on chemokine/chemokine receptor pairs and their ability to promote tumor cell migration and angiogenesis. The chemokine receptor CXCR3 is involved in tumor metastasis and is used as a prognostic biomarker. However, its relationship with the clinicopathological features of primary glioblastoma multiforme (pGBM) and its potential prognostic value have yet to be investigated. Here, we report that high CXCR3 expression conferred poor survival in pGBM patients. Further analysis showed that CXCR3 served as an independent prognostic biomarker for pGBM patients. In addition, functional assays indicated that CXCR3 induced glioma cell invasion. Therefore, this evidence indicates CXCR3 is an independent prognostic factor for pGBM patients and promotes an invasive phenotype, which suggests a new potential biotarget for glioblastoma multiforme therapy.

ROCK1, a novel target of miR-145, promotes glioma cell invasion

Malignant glioma is the most common type of cancer in the central nervous system, with highly invasive characteristics. The Rho-associated protein kinase (ROCK1) has been found to act as key regulator of actin cytoskeleton reorganization, a process closely associated with cancer cell invasion. microRNA-145 (miRNA-145) has been recently shown to act as a suppressor in several types of tumor, including glioma. However, the exact regulatory mechanism by which miR-145 inhibits glioma still remains to be uncovered. In this study, we report that the miR-145 level was significantly reduced in glioma tissues and in the human glioma cell lines U87 and U251, as compared to matched adjacent and normal brain tissues. We then identified the ROCK1 gene as a novel target of miR-145. The expression of ROCK1 was markedly upregulated in glioma tissues, as well as in U87 and U251 cells. Moreover, miR-145 significantly inhibited ROCK1 protein expression in U87 cells. We further show that miR-145 transfection considerably reduced the invasive ability of U87 cells, and was accompanied by the downregulation of matrix metalloproteinase 2 and 9, an effect which could be attenuated by overexpression of ROCK1. In conclusion, the present study suggests that miR-145 can inhibit U87 glioma cell invasion, at least partially via downregulation of the RhoA/ROCK1 pathway. In conclusion, this is the first study to report that ROCK1, as a novel target of miR-145, acts as a positive regulator of glioma cell invasion. Therefore, ROCK1 may constitute a promising target for glioma treatment.

Leveraging metabolomics to assess the next generation of temozolomide-based therapeutic approaches for glioblastomas

Glioblastoma multiforme (GBM) is the most common adult primary tumor of the central nervous system. The current standard of care for glioblastoma patients involves a combination of surgery, radiotherapy and chemotherapy with the alkylating agent temozolomide. Several mechanisms underlying the inherent and acquired temozolomide resistance have been identified and contribute to treatment failure. Early identification of temozolomide-resistant GBM patients and improvement of the therapeutic strategies available to treat this malignancy are of uttermost importance. This review initially looks at the molecular pathways underlying GBM formation and development with a particular emphasis placed on recent therapeutic advances made in the field. Our focus will next be directed toward the molecular mechanisms modulating temozolomide resistance in GBM patients and the strategies envisioned to circumvent this resistance. Finally, we highlight the diagnostic and prognostic value of metabolomics in cancers and assess its potential usefulness in improving the current standard of care for GBM patients.

Suppression of tumorigenicity by microRNA-138 through inhibition of EZH2-CDK4/6-pRb-E2F1 signal loop in glioblastoma multiforme

Deregulation of microRNAs (miRNAs) is implicated in tumor progression. We attempt to identify the tumor suppressive miRNA not only down-regulated in glioblastoma multiforme (GBM) but also potent to inhibit the oncogene EZH2, and then investigate the biological function and pathophysiologic role of the candidate miRNA in GBM. In this study, we show that miRNA-138 is reduced in both GBM clinical specimens and cell lines, and is effective to inhibit EZH2 expression. Moreover, high levels of miR-138 are associated with long overall and progression-free survival of GBM patients from The Cancer Genome Atlas dataset (TCGA) data portal. Ectopic expression of miRNA-138 effectively inhibits GBM cell proliferation in vitro and tumorigenicity in vivo through inducing cell cycles G1/S arrest. Mechanism investigation reveals that miRNA-138 acquires tumor inhibition through directly targeting EZH2, CDK6, E2F2 and E2F3. Moreover, an EZH2-mediated signal loop, EZH2-CDK4/6-pRb-E2F1, is probably involved in GBM tumorigenicity, and this loop can be blocked by miRNA-138. Additionally, miRNA-138 negatively correlates to mRNA levels of EZH2 and CDK6 among GBM clinical samples from both TCGA and our small amount datasets. In conclusion, our data demonstrate a tumor suppressive role of miRNA-138 in GBM tumorigenicity, suggesting a potential application in GBM therapy.

Direct quantification of microRNA at low picomolar level in sera of glioma patients using a competitive hybridization followed by amplified voltammetric detection

MicroRNAs (miRNAs), acting as oncogenes or tumor suppressors in humans, play a key role in regulating gene expression and are believed to be important for developing novel therapeutic treatments and clinical prognoses. Due to their short lengths (17-25 nucleotides) and extremely low concentrations (typically < picomolar) in biological samples, quantification of miRNAs has been challenging to conventional biochemical methods, such as Northern blotting, microarray, and quantitative polymerase chain reaction (qPCR). In this work, a biotinylated miRNA (biotin-miRNA) whose sequence is the same as that of a miRNA target is introduced into samples of interest and allowed to compete with the miRNA target for the oligonucleotide (ODN) probe preimmobilized onto an electrode. Voltammetric quantification of the miRNA target was accomplished after complexation of the biotin-miRNA with ferrocene (Fc)-capped gold nanoparticle/streptavidin conjugates. The Fc oxidation current was found to be inversely proportional to the concentration of target miRNA between 10 fM and 2.0 pM. The method is highly reproducible (relative standard deviation (RSD) < 5%), regenerable (at least 8 regeneration/assay cycles without discernible signal decrease), and selective (with sequence specificity down to a single nucleotide mismatch). The low detection levels (10 fM or 0.1 attomoles of miRNA in a 10 μL solution) allow the direct quantification of miRNA-182, a marker correlated to the progression of glioma in patients, to be performed in serum samples without sample pretreatment and RNA extraction and enrichment. The concentration of miRNA-182 in glioma patients was found to be 3.1 times as high as that in healthy persons, a conclusion in excellent agreement with a separate qPCR measurement of the expression level. The obviations of the requirement of an internal reference in qPCR, simplicity, and cost-effectiveness are other additional advantages of this method for detection of nucleic acids in clinical samples.

miRNA expression profiling in migrating glioblastoma cells: regulation of cell migration and invasion by miR-23b via targeting of Pyk2

Background

Glioblastoma (GB) is the most common and lethal type of primary brain tumor. Clinical outcome remains poor and is essentially palliative due to the highly invasive nature of the disease. A more thorough understanding of the molecular mechanisms that drive glioma invasion is required to limit dispersion of malignant glioma cells.

Methodology/Principal Findings

We investigated the potential role of differential expression of microRNAs (miRNA) in glioma invasion by comparing the matched large-scale, genome-wide miRNA expression profiles of migrating and migration-restricted human glioma cells. Migratory and migration-restricted cell populations from seven glioma cell lines were isolated and profiled for miRNA expression. Statistical analyses revealed a set of miRNAs common to all seven glioma cell lines that were significantly down regulated in the migrating cell population relative to cells in the migration-restricted population. Among the down-regulated miRNAs, miR-23b has been reported to target potential drivers of cell migration and invasion in other cell types. Over-expression of miR-23b significantly inhibited glioma cell migration and invasion. A bioinformatics search revealed a conserved target site within the 3′ untranslated region (UTR) of Pyk2, a non-receptor tyrosine kinase previously implicated in the regulation of glioma cell migration and invasion. Increased expression of miR-23b reduced the protein expression level of Pyk2 in glioma cells but did not significantly alter the protein expression level of the related focal adhesion kinase FAK. Expression of Pyk2 via a transcript variant missing the 3′UTR in miR-23b-expressing cells partially rescued cell migration, whereas expression of Pyk2 via a transcript containing an intact 3′UTR failed to rescue cell migration.

Conclusions/Significance

Reduced expression of miR-23b enhances glioma cell migration in vitro and invasion ex vivo via modulation of Pyk2 protein expression. The data suggest that specific miRNAs may regulate glioma migration and invasion to influence the progression of this disease.

Genome-wide profiling identified a set of miRNAs that are differentially expressed in glioblastoma stem cells and normal neural stem cells

A major challenge in cancer research field is to define molecular features that distinguish cancer stem cells from normal stem cells. In this study, we compared microRNA (miRNA) expression profiles in human glioblastoma stem cells and normal neural stem cells using combined microarray and deep sequencing analyses. These studies allowed us to identify a set of 10 miRNAs that are considerably up-regulated or down-regulated in glioblastoma stem cells. Among them, 5 miRNAs were further confirmed to have altered expression in three independent lines of glioblastoma stem cells by real-time RT-PCR analysis. Moreover, two of the miRNAs with increased expression in glioblastoma stem cells also exhibited elevated expression in glioblastoma patient tissues examined, while two miRNAs with decreased expression in glioblastoma stem cells displayed reduced expression in tumor tissues. Furthermore, we identified two oncogenes, NRAS and PIM3, as downstream targets of miR-124, one of the down-regulated miRNAs; and a tumor suppressor, CSMD1, as a downstream target of miR-10a and miR-10b, two of the up-regulated miRNAs. In summary, this study led to the identification of a set of miRNAs that are differentially expressed in glioblastoma stem cells and normal neural stem cells. Characterizing the role of these miRNAs in glioblastoma stem cells may lead to the development of miRNA-based therapies that specifically target tumor stem cells, but spare normal stem cells.

Recent advances in the molecular understanding of glioblastoma

Glioblastoma is the most common and most aggressive primary brain tumor. Despite maximum treatment, patients only have a median survival time of 15 months, because of the tumor’s resistance to current therapeutic approaches. Thus far, methylation of the O⁶-methylguanine-DNA methyltransferase (MGMT) promoter has been the only confirmed molecular predictive factor in glioblastoma. Novel “genome-wide” techniques have identified additional important molecular alterations as mutations in isocitrate dehydrogenase 1 (IDH1) and its prognostic importance. This review summarizes findings and techniques of genetic, epigenetic, transcriptional, and proteomic studies of glioblastoma. It provides the clinician with an up-to-date overview of current identified molecular alterations that should ultimately lead to new therapeutic targets and more individualized treatment approaches in glioblastoma.

Immunotherapy targeting glioma stem cells--insights and perspectives

INTRODUCTION

Glioblastoma multiforme (GBM) is the most aggressive and lethal primary malignant brain tumor. Although progress has been made in current conventional therapies for GBM patients, the effect of these advances on clinical outcomes has been disappointing. Recent research into the origin of cancers suggest that GBM cancer stem cells (GSC) are the source of initial tumor formation, resistance to current conventional therapeutics and eventual patient relapse. Currently, there are very few studies that apply immunotherapy to target GSC.

AREAS COVERED

CD133, a cell surface protein, is used extensively as a surface marker to identify and isolate GSC in malignant glioma. We discuss biomarkers such as CD133, L1-cell adhesion molecule (L1-CAM), and A20 of GSC. We review developing novel treatment modalities, including immunotherapy strategies, to target GSC.

EXPERT OPINION

There are very few reports of preclinical studies targeting GSC. Identification and validation of unique molecular signatures and elucidation of signaling pathways involved in survival, proliferation and differentiation of GSC will significantly advance this field and provide a framework for the rational design of a new generation of antigen-specific, anti-GSC immunotherapy- and nanotechnology-based targeted therapyies. Combined with other therapeutic avenues, GSC-targeting therapies may represent a new paradigm to treat GBM patients.

miRNA-mediated immune regulation and immunotherapeutic potential in glioblastoma

Glioblastoma (GB), the most common primary neoplasm of the CNS, remains universally fatal with standard therapies and has a mean overall survival time of only 14.6 months. Even in the most favorable situations most patients do not survive longer than 2 years. Another hallmark of GBs, apart from the poor control of proliferation, is an immune suppressed tumor microenvironment. miRNAs usually bind the 3' untranslated region of target mRNAs and direct their post-transcriptional repression. Certain miRNAs are known to have altered expression levels in GB tumors, and in many immune cell subtypes. miRNAs have been found to serve important roles in gene regulation and are implicated in many processes in oncogenesis and immune deregulation. In this article we focus on the miRNAs involved in gliomagenesis and in the regulation of the immune response. We also present current challenges and miRNA immunotherapeutic strategies that should be investigated further.

MiRNA expression patterns predict survival in glioblastoma

Background

In order to define new prognostic subgroups in patients with glioblastoma a miRNA screen (> 1000 miRNAs) from paraffin tissues followed by a bio-mathematical analysis was performed.

Methods

35 glioblastoma patients treated between 7/2005 - 8/2008 at a single institution with surgery and postoperative radio(chemo)therapy were included in this retrospective analysis. For microarray analysis the febit biochip "Geniom^® Biochip MPEA homo-sapiens" was used. Total RNA was isolated from FFPE tissue sections and 1100 different miRNAs were analyzed.

Results

It was possible to define a distinct miRNA expression pattern allowing for a separation of distinct prognostic subgroups. The defined miRNA pattern was significantly associated with early death versus long-term survival (split at 450 days) (p = 0.01). The pattern and the prognostic power were both independent of the MGMT status.

Conclusions

At present, this is the first dataset defining a prognostic role of miRNA expression patterns in patients with glioblastoma. Having defined such a pattern, a prospective validation of this observation is required.

Integration and analysis of genome-scale data from gliomas

Primary brain tumors are a leading cause of cancer-related mortality among young adults and children. The most common primary malignant brain tumor, glioma, carries a median survival of only 14 months. Two major multi-institutional programs, the Glioma Molecular Diagnostic Initiative and The Cancer Genome Atlas, have pursued a comprehensive genomic characterization of a large number of clinical glioma samples using a variety of technologies to measure gene expression, chromosomal copy number alterations, somatic and germline mutations, DNA methylation, microRNA, and proteomic changes. Classification of gliomas on the basis of gene expression has revealed six major subtypes and provided insights into the underlying biology of each subtype. Integration of genome-wide data from different technologies has been used to identify many potential protein targets in this disease, while increasing the reliability and biological interpretability of results. Mapping genomic changes onto both known and inferred cellular networks represents the next level of analysis, and has yielded proteins with key roles in tumorigenesis. Ultimately, the information gained from these approaches will be used to create customized therapeutic regimens for each patient based on the unique genomic signature of the individual tumor. In this Review, we describe efforts to characterize gliomas using genomic data, and consider how insights gained from these analyses promise to increase understanding of the biological underpinnings of the disease and lead the way to new therapeutic strategies.