MicroRNAs in glioblastoma multiforme pathogenesis and therapeutics

Identification of a novel role of IL-13Rα2 in human Glioblastoma multiforme: interleukin-13 mediates signal transduction through AP-1 pathway

Background

Previously, we have demonstrated that Interleukin 13 receptor alpha 2 (IL-13Rα2) is overexpressed in approximate 78% Glioblastoma multiforme (GBM) samples. We have also demonstrated that IL-13Rα2 can serve as a target for cancer immunotherapy in several pre-clinical and clinical studies. However, the significance of overexpression of IL-13Rα2 in GBM and astrocytoma and signaling through these receptors is not known. IL-13 can signal through IL-13R via JAK/STAT and AP-1 pathways in certain cell lines including some tumor cell lines. Herein, we have investigated a role of IL-13/IL-13Rα2 axis in signaling through AP-1 transcription factors in human glioma samples in situ.

Methods

We examined the activation of AP-1 family of transcription factors (c-Jun, Fra-1, Jun-D, c-Fos, and Jun-B) after treating U251, A172 (IL-13Rα2 +ve) and T98G (IL-13Rα2 −ve) glioma cell lines with IL-13 by RT-qPCR, and immunocytochemistry (ICC). We also performed colorimetric ELISA based assay to determine AP-1 transcription factor activation in glioma cell lines. Furthermore, we examined the expression of AP-1 transcription factors in situ in GBM and astrocytoma specimens by multiplex-immunohistochemistry (IHC). Student t test and ANOVA were used for statistical analysis of the results.

Results

We have demonstrated up-regulation of two AP-1 transcription factors (c-Jun and Fra-1) at mRNA and protein levels upon treatment with IL-13 in IL-13Rα2 positive but not in IL-13Rα2 negative glioma cell lines. Both transcription factors were also overexpressed in patient derived GBM specimens, however, in contrast to GBM cell lines, c-Fos is also overexpressed in patient derived specimens. Astrocytoma specimens showed lesser extent of immunostaining for IL-13Rα2 and three AP-1 factors compared to GBM specimens. By transcription factor activation assay, we demonstrated that AP-1 transcription factors (C-Jun and Fra-1) were activated upon treatment of IL-13Rα2 + GBM cell lines but not IL-13Rα2 − GBM cell line with IL-13. Our results demonstrate functional activity of AP-1 transcription factor in GBM cell lines in response to IL-13.

Conclusions

These results indicate that IL-13/IL-13Rα2 axis can mediate signal transduction in situ via AP-1 pathway in GBM and astrocytoma and may serve as a new target for GBM immunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1746-6) contains supplementary material, which is available to authorized users.

Glioma Cell Secretion: A Driver of Tumor Progression and a Potential Therapeutic Target

Cellular secretion is an important mediator of cancer progression. Secreted molecules in glioma are key components of complex autocrine and paracrine pathways that mediate multiple oncogenic pathologies. In this review, we describe tumor cell secretion in high-grade glioma and highlight potential novel therapeutic opportunities. Cancer Res; 78(21); 6031-9. ©2018 AACR.

Potential Strategies Overcoming the Temozolomide Resistance for Glioblastoma

Glioblastoma (GBM) is a highly malignant type of primary brain tumor with a high mortality rate. Although the current standard therapy consists of surgery followed by radiation and temozolomide (TMZ), chemotherapy can extend patient's post-operative survival but most cases eventually demonstrate resistance to TMZ. O6-methylguanine-DNA methyltransferase (MGMT) repairs the main cytotoxic lesion, as O6-methylguanine, generated by TMZ, can be the main mechanism of the drug resistance. In addition, mismatch repair and BER also contribute to TMZ resistance. TMZ treatment can induce self-protective autophagy, a mechanism by which tumor cells resist TMZ treatment. Emerging evidence also demonstrated that a small population of cells expressing stem cell markers, also identified as GBM stem cells (GSCs), contributes to drug resistance and tumor recurrence owing to their ability for self-renewal and invasion into neighboring tissue. Some molecules maintain stem cell properties. Other molecules or signaling pathways regulate stemness and influence MGMT activity, making these GCSs attractive therapeutic targets. Treatments targeting these molecules and pathways result in suppression of GSCs stemness and, in highly resistant cases, a decrease in MGMT activity. Recently, some novel therapeutic strategies, targeted molecules, immunotherapies, and microRNAs have provided new potential treatments for highly resistant GBM cases. In this review, we summarize the current knowledge of different resistance mechanisms, novel strategies for enhancing the effect of TMZ, and emerging therapeutic approaches to eliminate GSCs, all with the aim to produce a successful GBM treatment and discuss future directions for basic and clinical research to achieve this end.

Long noncoding RNA gastric cancer-associated transcript 3 plays oncogenic roles in glioma through sponging miR-3127-5p

Evidence is emerging that long noncoding RNAs (lncRNAs) play vital roles in tumorigenesis. LncRNA gastric cancer-associated transcript 3 (GACAT3) is reported to participate in the development of breast cancer, colorectal cancer, nonsmall cell lung cancer, and gastric cancer. However, whether it is implicated in glioma has not been elucidated. Here, we found that GACAT3 level was aberrantly elevated in glioma tissues and cell lines. Higher GACAT3 expression predicted lower survival rate. Knockdown of GACAT3 suppressed the proliferation, colony formation, migration, and invasion but promoting apoptosis in glioma cells. Next, we determined that GACAT3 contributes to glioma progression through inhibiting microRNA (miR)-3127-5p. Subsequently, ELAVL1 was identified as a direct target of miR-3127-5p by bioinformatics analysis and luciferase reporter assay. Moreover, we confirmed that GACAT3 promoted ELAVL1 expression through sponging miR-3127-5p, leading to glioma progression. Taken together, our study elucidated that GACAT3/miR-3127-5p/ELAVL1 signaling regulates glioma development and might be a promising therapeutic target.

miR-874 regulates multiple-drug resistance in gastric cancer by targeting ATG16L1

Chemotherapy is an important treatment option for gastric cancer (GC); however, chemotherapy usually fails due to drug resistance, particularly multidrug resistance (MDR). In our previous studies, microRNA (miR)‑874 was demonstrated to serve an important role in tumour growth, apoptosis and angiogenesis. In the present study, the precise roles and underlying mechanisms of miR‑874 in MDR were investigated in GC. The overexpression of miR‑874 reversed cancer cell drug resistance in vitro. According to reporter gene and western blot assays, Autophagy‑related 16‑like 1 (ATG16 L1) was identified as a direct target of miR‑874. ATG16L1 was also demonstrated to be positively associated with autophagy. Reducing the expression of ATG16L1 and inhibiting the occurrence of autophagy sensitized GC cells to chemotherapy. Thus, the miR‑874/ATG16L1/autophagy regulatory loop was demonstrated to serve an important role in MDR in GC. Furthermore, miR‑874 may be used as a prognostic factor in GC. Overall, miR‑874 could inhibit autophagy and sensitize GC cells to chemotherapy via the target gene ATG16L1, highlighting the potential clinical application of miR‑874 in chemotherapeutic resistance.

miR-370-3p Is a Therapeutic Tool in Anti-glioblastoma Therapy but Is Not an Intratumoral or Cell-free Circulating Biomarker

In the last decade, microRNAs (miRs) have been described as biomarkers and therapeutic agents. Based on this finding, our aim here is to know if (1) miRNA-370-3p can be used as a biomarker associated with a favorable survival and if (2) miRNA-370-3p can be used as a therapeutic tool that increases the efficiency of standard anti-GBM treatment. A first approach using the data available on the “Prognostic miRNA Database” indicated that the expression level of miRNA-370-3p in GBM (T-miR-370-3p) is not associated with a prognosis value for survival. A second approach quantifying the expression level of cell-free circulating miRNA-370-3p (cfc-miR-370-3p) also indicated that cfc-miR-370-3p is not associated with a prognosis value for survival. To investigate whether miR-370-3p can be used in vivo to increase the anti-GBM effect of TMZ, we then used the model of LN18-induced GBMs in mice. Our data indicated that the miRNA-370-3p/TMZ treatment was two times more efficient than the TMZ treatment for decreasing the tumor volume. In addition, our study correlated the decrease of tumor volume induced by the miRNA-370-3p/TMZ treatment with the decrease in FOXM1 and MGMT (i.e., two targets of miR-370-3p).

Our data thus support the idea that miR-370-3p could be used as therapeutic tool for anti-glioblastoma therapy, but not as a biomarker.

miR-17-5p-CXCL14 axis related transcriptome profile and clinical outcome in diffuse gliomas

GBM tissues are comprised of not only tumor cells but also tumor-associated nontumor cells, such as stromal cells and immune cells, which dilute the purity of glioma cells and function in glioma biology. However, the roles of miRNAs in modulating glioma purity are not clarified. In total, 838 glioma samples with transcriptome data, including 537 RNAseq data from TCGA project and 301 microarray data from Chinese Glioma Genome Atlas (CGGA project), were recruited into our investigation. Tumor purity, molecular subtypes and IDH status were also available. R language was employed as the main tool for statistical analysis and graphical work. Screening miRNA profiling and paired TCGA samples' transcriptome data demonstrates that miR-17-5p expression harbors the most significant positive correlation with glioma purity among all miRNAs. CXCL14 shows robust negative correlation with miR-17-5p expression in TCGA and CGGA dataset. miR-17-5p directly targets CXCL14 and functions as a tumor-suppressor of GBM. CXCL14 showed lower expression in proneural subtype and may contribute as a potential marker for proneural subtype in glioma. Genes markedly correlated with CXCL14 are involved in essential functions associated with anti-tumor immune process. CXCL14 has a strong correlation with immune(T cells, Monocytic lineage and Neutrophils) and Fibroblasts within glioma environment. miR-17-5p and CXCL14 exhibited predictive values for high-grade glioma(HGG) patients: Higher miR-17-5p indicated significantly longer survival while lower CXCL14 indicated longer survival. Our results highlight the importance of the miR-17-5p-CXCL14 axis in regulating key steps of anti-tumor immune process and may serve as potential targets of immune treatments for gliomas.

LncRNA LINC01446 promotes glioblastoma progression by modulating miR-489-3p/TPT1 axis

Accumulating evidence indicates that long noncoding RNA (lncRNA) is implicated in human diseases, including cancers. However, how lncRNA regulates glioblastoma (GBM) progression is poorly understood. Our study revealed a novel lncRNA LINC01446 whose expression was elevated in GBM tissues. Besides, high expression of LINC01446 indicated a poor prognosis in GBM patients. Functionally, LINC01446 knockdown dramatically inhibited GBM cell proliferation, arrested cell-cycle progression and attenuated invasion in vitro. Furthermore, the xenograft mouse model showed that LINC01446 silence led to impaired tumor growth in vivo. Mechanistically, bioinformatics analysis showed that LINC01446 acted as a sponge for miR-489-3p which targeted TPT1. Though inhibiting miR-489-3p availability, LINC01446 promoted TPT1 expression in GBM cells. Rescue experiments demonstrated that restoration of TPT1 could significantly rescued the effects of LINC01446 silence or miR-489-3p overexpression. Taken together, this study demonstrates a novel singling pathway of LINC01446/miR-489-3p/TPT1 cascade that regulates GBM progression.

Long noncoding RNA H19, and not microRNA miR-326, is over-expressed and predicts survival in glioblastoma

Glioblastoma (GB) represents the most common malignant brain tumor, which, despite extensive research, remains of poor prognosis. The focus of recent studies of GB pathogenesis has shifted to the study of the role of noncoding RNAs (ncRNAs). In this study, we examined the expression levels of the microRNA miR-326 and the long ncRNA H19 (on which a miR-326 putative binding site was found by in-silico analysis) in brain tumor tissue from GB patients as compared to cancer-free brain tissue. Relative expression levels of miR-326 were not found to be significantly altered in GB patients. By comparison, H19 was consistently over-expressed in all GB patients (p < 0.001), and correlated with poorer overall survival (OS) and progression-free survival (PFS) (p = 0.026 and p = 0.045, respectively). At a cutoff value of 5.27, H19 up-regulation could predict OS in GB patients, with a 71.4% sensitivity and 59.6% specificity (p = 0.026). The current GB patients were clustered by the multivariate analysis into 4 groups based on miR-326 and H19 expression profiles, age at diagnosis, and PFS. Our data suggest a role for H19 in the pathogenesis of GB and could be a potential prognostic biomarker for GB.

Oncogenic MicroRNA-20a is downregulated by the HIF-1α/c-MYC pathway in IDH1 R132H-mutant glioma

Mutations in the isocitrate dehydrogenase 1 (IDH1) gene have been identified as one of the earliest events in gliomagenesis, occurring in over 70% of low grade gliomas and are present in the vast majority of secondary glioblastoma (GBM) that develop from these low-grade lesions. The aim of this study was to investigate whether the IDH1 R132H mutation influences the expression of oncogenic miR-20a and shed light on the underlying molecular mechanisms. The findings of the current study demonstrate presence of the IDH1 R132H mutation in primary human glioblastoma cell lines with upregulated HIF-1α expression, downregulating c-MYC activity and resulting in a consequential decrease in miR-20a, which is responsible for cell proliferation and resistance to standard temozolomide treatment. Elucidating the mechanism of oncogenic miR-20a activity introduces its role among well-established signaling pathways (i.e. HIF/c-MYC) and may be a meaningful prognostic biomarker or target for novel therapies among patients with IDH1-mutant glioma.

miR-24-3p/FGFR3 Signaling as a Novel Axis Is Involved in Epithelial-Mesenchymal Transition and Regulates Lung Adenocarcinoma Progression

Our previous studies showed that Fibroblast growth factor receptor 3 (FGFR3) contributed to cell growth in lung cancer. However, the correlation between FGFR3 and tumor progression, coupled with the underlying mechanisms, are not fully understood. The clinical significance of FGFR3 was determined in two cohorts of clinical samples (n = 22, n = 78). A panel of biochemical assays and functional experiments was utilized to elucidate the underlying mechanisms and effects of FGFR3 and miR-24-3p on lung adenocarcinoma progression. Upregulated FGFR3 expression indicated an adverse prognosis for lung adenocarcinoma individuals and promoted metastatic potential of lung adenocarcinoma cells. Owing to the direct regulation towards FGFR3, miR-24-3p could interfere with the potential of proliferation, migration, and invasion in lung adenocarcinoma, following variations of EMT-related protein expression. As a significant marker of EMT, E-cadherin was negatively correlated with FGFR3, of which ectopic overexpression could neutralize the antitumour effects of miR-24-3p and reverse its regulatory effects on EMT markers. Taken together, these findings define a novel insight into the miR-24-3p/FGFR3 signaling axis in regulating lung adenocarcinoma progression and suggest that targeting the miR-24-3p/FGFR3 axis could be an effective and efficient way to prevent tumor progression.

The novel long non-coding RNA TALNEC2, regulates tumor cell growth and the stemness and radiation response of glioma stem cells

Despite advances in novel therapeutic approaches for the treatment of glioblastoma (GBM), the median survival of 12-14 months has not changed significantly. Therefore, there is an imperative need to identify molecular mechanisms that play a role in patient survival. Here, we analyzed the expression and functions of a novel lncRNA, TALNEC2 that was identified using RNA seq of E2F1-regulated lncRNAs. TALNEC2 was localized to the cytosol and its expression was E2F1-regulated and cell-cycle dependent. TALNEC2 was highly expressed in GBM with poor prognosis, in GBM specimens derived from short-term survivors and in glioma cells and glioma stem cells (GSCs). Silencing of TALNEC2 inhibited cell proliferation and arrested the cells in the G1\S phase of the cell cycle in various cancer cell lines. In addition, silencing of TALNEC2 decreased the self-renewal and mesenchymal transformation of GSCs, increased sensitivity of these cells to radiation and prolonged survival of mice bearing GSC-derived xenografts. Using miRNA array analysis, we identified specific miRNAs that were altered in the silenced cells that were associated with cell-cycle progression, proliferation and mesenchymal transformation. Two of the downregulated miRNAs, miR-21 and miR-191, mediated some of TALNEC2 effects on the stemness and mesenchymal transformation of GSCs. In conclusion, we identified a novel E2F1-regulated lncRNA that is highly expressed in GBM and in tumors from patients of short-term survival. The expression of TALNEC2 is associated with the increased tumorigenic potential of GSCs and their resistance to radiation. We conclude that TALNEC2 is an attractive therapeutic target for the treatment of GBM.

Transfer of functional microRNAs between glioblastoma and microvascular endothelial cells through gap junctions

Extensive invasion and angiogenesis are hallmark features of malignant glioblastomas. Here, we co-cultured U87 human glioblastoma cells and human microvascular endothelial cells (HMEC) to demonstrate the exchange of microRNAs that initially involve the formation of gap junction communications between the two cell types. The functional inhibition of gap junctions by carbenoxolone blocks the transfer of the anti-tumor miR-145-5p from HMEC to U87, and the transfer of the pro-invasive miR-5096 from U87 to HMEC. These two microRNAs exert opposite effects on angiogenesis in vitro. MiR-5096 was observed to promote HMEC tubulogenesis, initially by increasing Cx43 expression and the formation of heterocellular gap junctions, and secondarily through a gap-junction independent pathway. Our results highlight the importance of microRNA exchanges between tumor and endothelial cells that in part involves the formation of functional gap junctions between the two cell types.

MicroRNA-Based Drugs for Brain Tumors

MicroRNAs (miRNAs) are key regulatory elements encoded by the genome. A single miRNA can downregulate the expression of multiple genes involved in diverse functions. Because cancer is a disease with multiple gene aberrations, developing novel approaches to identify and modulate miRNA pathways may result in a breakthrough for cancer treatment. With a special focus on glioblastoma (GBM), this review provides an up-to-date summary of miRNA biogenesis, the role of miRNA in cancer resistance, and essential tools for modulating miRNA expression, as well as of clinically promising RNAi delivery systems and how they can be adapted for therapy.

Allicin induces apoptosis through activation of both intrinsic and extrinsic pathways in glioma cells

Allicin is an extract purified from Allium sativum (garlic), and previous research has indicated that Allicin has an inhibitory effect on many kinds of tumor cells. The aim of the present study was to explore the anticancer activity of Allicin on human glioma cells and investigate the underlying mechanism. MTT and colony-formation assays were performed to detect glioma cell proliferation, and explore the effect of Allicin at various doses and time-points. The apoptosis of glioma cells was measured by fluorescence microscopy with Hoechst 33258 staining, and then flow cytometry was used to analyzed changes in glioma cell apoptosis. Reverse transcription‑quantitative polymerase chain reaction and western blot analysis were used to detect the effect of Allicin on the expression levels of Fas/Fas ligand (FasL), caspase‑3, B‑cell lymphoma 2 and Bcl‑2‑associated X protein. Allicin suppressed the proliferation and colony formation ability of U251 cells in a dose‑ and time‑dependent manner. A cytotoxic effect of Allicin was observed in glioma cells in a dose‑dependent manner. Changes in nuclear morphology were observed in U251 cells with Hoechst 33258 staining. The activity of caspases were significantly elevated and Fas/FasL expression levels were increased following treatment with Allicin, at both the mRNA and protein level. These results demonstrated that Allicin suppresses proliferation and induces glioma cell apoptosis in vitro. Both intrinsic mitochondrial and extrinsic Fas/FasL‑mediated pathways react in glioma cell after treating with Allicin, which then activate major apoptotic cascades. These results implicate Allicin as a novel antitumor agent in treating glioma.

microRNA-7 upregulates death receptor 5 and primes resistant brain tumors to caspase-mediated apoptosis

Background

MicroRNAs (miRs) are known to play a pivotal role in tumorigenesis, controlling cell proliferation and apoptosis. In this study, we investigated the potential of miR-7 to prime resistant tumor cells to apoptosis in glioblastoma (GBM).

Methods

We created constitutive and regulatable miR-7 expression vectors and utilized pharmacological inhibition of caspases and genetic loss of function to study the effect of forced expression of miR-7 on death receptor (DR) pathways in a cohort of GBM with established resistance to tumor necrosis factor apoptosis inducing ligand (TRAIL) and in patient-derived primary GBM stem cell (GSC) lines. We engineered adeno-associated virus (AAV)-miR-7 and stem cell (SC) releasing secretable (S)-TRAIL and utilized real time in vivo imaging and neuropathology to understand the effect of the combined treatment of AAV-miR-7 and SC-S-TRAIL in vitro and in mouse models of GBM from TRAIL-resistant GSC.

Results

We show that expression of miR-7 in GBM cells results in downregulation of epidermal growth factor receptor and phosphorylated Akt and activation of nuclear factor-kappaB signaling. This leads to an upregulation of DR5, ultimately priming resistant GBM cells to DR-ligand, TRAIL-induced apoptotic cell death. In vivo, a single administration of AAV-miR-7 significantly decreases tumor volumes, upregulates DR5, and enables SC-delivered S-TRAIL to eradicate GBM xenografts generated from patient-derived TRAIL-resistant GSC, significantly improving survival of mice.

Conclusions

This study identifies the unique role of miR-7 in linking cell proliferation to death pathways that can be targeted simultaneously to effectively eliminate GBM, thus presenting a promising strategy for treating GBM.

Glioblastoma: new therapeutic strategies to address cellular and genomic complexity

Glioblastoma (GBM) is the most invasive and devastating primary brain tumor with a median overall survival rate about 18 months with aggressive multimodality therapy. Its unique characteristics of heterogeneity, invasion, clonal populations maintaining stem cell-like cells and recurrence, have limited responses to a variety of therapeutic approaches, and have made GBM the most difficult brain cancer to treat. A great effort and progress has been made to reveal promising molecular mechanisms to target therapeutically. Especially with the emerging of new technologies, the mechanisms underlying the pathology of GBM are becoming more clear. The purpose of this review is to summarize the current knowledge of molecular mechanisms of GBM and highlight the novel strategies and concepts for the treatment of GBM.

Downregulation of miR‑205 is associated with glioblastoma cell migration, invasion, and the epithelial-mesenchymal transition, by targeting ZEB1 via the Akt/mTOR signaling pathway

Glioblastoma (GBM) is the most common type of malignant brain tumor. In spite of recent advancements in surgical techniques, chemotherapy, and radiation therapy, patients with GBM often face a dire prognosis. MicroRNAs have been shown to modulate the aggressiveness of various cancers, and have emerged as possible therapeutic agents for the management of GBM. miR‑205 is dysregulated in glioma and act as a prognostic indicator. However, the role of miR‑205 in the development of GBM has not been elucidated. To better understand the pathogenesis of GBM, we examine the biological significance and molecular mechanisms of miR‑205 in GBM cells. Zinc finger E-box binding homeobox 1 (ZEB1) has been shown to regulate the epithelial-mesenchymal transition (EMT), which is strongly associated with GBM malignancy. In the present study, we show miR‑205 expression is reduced in GBM tissues and cell lines, and ZEB1 expression is inversely correlated with miR‑205 expression. We also show ZEB1 is a downstream target of miR‑205 and the Akt/mTOR signaling pathway is activated when miR‑205 interacts with ZEB1. Increased activity of miR‑205 in GBM cells significantly inhibits migration and invasion, and prevents EMT. Furthermore, overexpression of ZEB1 partially abolishes these inhibitory effects of miR‑205. We show that miR‑205 negatively regulates the expression of ZEB1 in GBM, inhibits cell migration and invasion, and prevents EMT, at least in part through the inhibition of the activation of the Akt/mTOR signaling pathway. Our results indicate miR‑205 may be an efficacious therapeutic agent in the treatment of GBM.

MicroRNA-target cross-talks: Key players in glioblastoma multiforme

The role of microRNAs in brain cancer is still naive. Some act as oncogene and others as tumor suppressors. Discovery of efficient biomarkers is mandatory to debate that aggressive disease. Bioinformatically selected microRNAs and their targets were investigated to evaluate their putative signature as diagnostic and prognostic biomarkers in primary glioblastoma multiforme. Expression of a panel of seven microRNAs (hsa-miR-34a, hsa-miR-16, hsa-miR-17, hsa-miR-21, hsa-miR-221, hsa-miR-326, and hsa-miR-375) and seven target genes ( E2F3, PI3KCA, TOM34, WNT5A, PDCD4, DFFA, and EGFR) in 43 glioblastoma multiforme specimens were profiled compared to non-cancer tissues via quantitative reverse transcription-polymerase chain reaction. Immunohistochemistry staining for three proteins (VEGFA, BAX, and BCL2) was performed. Gene enrichment analysis identified the biological regulatory functions of the gene panel in glioma pathway. MGMT ( O-6-methylguanine-DNA methyltransferase) promoter methylation was analyzed for molecular subtyping of tumor specimens. Our data demonstrated a significant upregulation of five microRNAs (hsa-miR-16, hsa-miR-17, hsa-miR-21, hsa-miR-221, and hsa-miR-375), three genes ( E2F3, PI3KCA, and Wnt5a), two proteins (VEGFA and BCL2), and downregulation of hsa-miR-34a and three other genes ( DFFA, PDCD4, and EGFR) in brain cancer tissues. Receiver operating characteristic analysis revealed that miR-34a (area under the curve = 0.927) and miR-17 (area under the curve = 0.900) had the highest diagnostic performance, followed by miR-221 (area under the curve = 0.845), miR-21 (area under the curve = 0.836), WNT5A (area under the curve = 0.809), PDCD4 (area under the curve = 0.809), and PI3KCA (area under the curve = 0.800). MGMT promoter methylation status was associated with high miR-221 levels. Moreover, patients with VEGFA overexpression and downregulation of TOM34 and BAX had poor overall survival. Nevertheless, miR-17, miR-221, and miR-326 downregulation were significantly associated with high recurrence rate. Multivariate analysis by hierarchical clustering classified patients into four distinct groups based on gene panel signature. In conclusion, the explored microRNA-target dysregulation could pave the road toward developing potential therapeutic strategies for glioblastoma multiforme. Future translational and functional studies are highly recommended to better understand the complex bio-molecular signature of this difficult-to-treat tumor.

Nanomaterials for convection-enhanced delivery of agents to treat brain tumors

Nanomaterials represent a promising and versatile platform for the delivery of therapeutics to the brain. Treatment of brain tumors has been a long-standing challenge in the field of neuro-oncology. The current standard of care - a multimodal approach of surgery, radiation and chemotherapy - yields only a modest therapeutic benefit for patients with malignant gliomas. A major obstacle for treatment is the failure to achieve sufficient delivery of therapeutics at the tumor site. Recent advances in local drug delivery techniques, along with the development of highly effective brain-penetrating nanocarriers, have significantly improved treatment and imaging of brain tumors in preclinical studies. The major advantage of this combined strategy is the ability to optimize local therapy, by maintaining an effective and sustained concentration of therapeutics in the brain with minimal systemic toxicity. This review highlights some of the latest developments, significant advancements and current challenges in local delivery of nanomaterials for the treatment of brain tumors.

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.

The Microvascular Gap Junction Channel: A Route to Deliver MicroRNAs for Neurological Disease Treatment

Brain microvascular endothelial cells (BMECs) separate the peripheral blood from the brain. These cells, which are surrounded by basal lamina, pericytes and glial cells, are highly interconnected through tight and gap junctions. Their permeability properties restrict the transfer of potentially useful therapeutic agents. In such a hermetic system, the gap junctional exchange of small molecules between cerebral endothelial and non-endothelial cells is crucial for maintaining tissue homeostasis. MicroRNA were shown to cross gap junction channels, thereby modulating gene expression and function of the recipient cell. It was also shown that, when altered, BMEC could be regenerated by endothelial cells derived from pluripotent stem cells. Here, we discuss the transfer of microRNA through gap junctions between BMEC, the regeneration of BMEC from induced pluripotent stem cells that could be engineered to express specific microRNA, and how such an innovative approach could benefit to the treatment of glioblastoma and other neurological diseases.

Breaching barriers in glioblastoma. Part I: Molecular pathways and novel treatment approaches

Glioblastoma multiforme (GBM) is the most common primary brain tumour, and the most aggressive in nature. The prognosis for patients with GBM remains poor, with a median survival time of only 1-2 years. The treatment failure relies on the development of resistance by tumour cells and the difficulty of ensuring that drugs effectively cross the dual blood brain barrier/blood brain tumour barrier. The advanced molecular and genetic knowledge has allowed to identify the mechanisms responsible for temozolomide resistance, which represents the standard of care in GBM, along with surgical resection and radiotherapy. Such resistance has motivated the researchers to investigate new avenues for GBM treatment intended to improve patient survival. In this review, we provide an overview of major obstacles to effective treatment of GBM, encompassing biological barriers, cancer stem cells, DNA repair mechanisms, deregulated signalling pathways and autophagy. New insights and potential therapy approaches for GBM are also discussed, emphasizing localized chemotherapy delivered directly to the brain, immunotherapy, gene therapy and nanoparticle-mediated brain drug delivery.

MicroRNA Regulation of Glycolytic Metabolism in Glioblastoma

Glioblastoma (GBM) is the most aggressive and common malignant brain tumour in adults. A well-known hallmark of GMB and many other tumours is aerobic glycolysis. MicroRNAs (miRNAs) are a class of short nonprotein coding sequences that exert posttranscriptional controls on gene expression and represent critical regulators of aerobic glycolysis in GBM. In GBM, miRNAs regulate the expression of glycolytic genes directly and via the regulation of metabolism-associated tumour suppressors and oncogenic signalling pathways. This review aims to establish links between miRNAs expression levels, the expression of GBM glycolytic regulatory genes, and the malignant progression and prognosis of GBM. In this review, the involvement of 25 miRNAs in the regulation of glycolytic metabolism of GBM is discussed. Seven of these miRNAs have been shown to regulate glycolytic metabolism in other tumour types. Further eight miRNAs, which are differentially expressed in GBM, have also been reported to regulate glycolytic metabolism in other cancer types. Thus, these miRNAs could serve as potential glycolytic regulators in GBM but will require functional validation. As such, the characterisation of these molecular and metabolic signatures in GBM can facilitate a better understanding of the molecular pathogenesis of this disease.

A tumor-suppressive microRNA, miRNA-485-5p, inhibits glioma cell proliferation and invasion by down-regulating TPD52L2

Glioblastoma multiforme is the most deadly primary brain tumor and has no effective treatment. Therefore, it is important to identify novel and effective therapies that impede glioma tumorigenesis. MicroRNAs (miRNAs) are helpful analytical biomarkers and may be useful targets for treating multiple human cancers. Previous reports suggest that miRNA-485-5p is dysregulated and contributes to tumorigenesis in some cancer types. Nevertheless, the biological role of miRNA-485-5p in glioma is not well understood. In this study, we demonstrated that miRNA-485-5p expression was reduced in gliomat issues and cell lines. In addition, miRNA-485-5p overexpression inhibited cell proliferation, migration, and invasion in glioma cell lines. Additionally, we identified Tumor Protein D52 Like 2 (TPD52L2) as a direct target of miRNA-485-5p. Moreover, we showed that miRNA-485-5p regulated glioma tumorigenesis by down-regulating TPD52L2 expression in vitro and in vivo. Our results suggest that miRNA-485-5p is a suppressor of glioma tumorigenesis and could serve as a novel candidate for therapeutic applications in glioma treatment.

Identification of IGF-1-enhanced cytokine expressions targeted by miR-181d in glioblastomas via an integrative miRNA/mRNA regulatory network analysis

The insulin-like growth factor (IGF)-1 signaling is relevant in regulating cell growth and cytokine secretions by glioblastomas. MicroRNAs determine the cell fate in glioblastomas. However, relationships between IGF-1 signaling and miRNAs in glioblastoma pathogenesis are still unclear. Our aim was to validate the IGF-1-mediated mRNA/miRNA regulatory network in glioblastomas. Using in silico analyses of mRNA array and RNA sequencing data from The Cancer Genome Atlas (TCGA), we identified 32 core enrichment genes that were highly associated with IGF-1-promoted cytokine-cytokine receptor interactions. To investigate the IGF-1-downregulated miRNA signature, microarray-based approaches with IGF-1-treated U87-MG cells and array data in TCGA were used. Four miRNAs, including microRNA (miR)-9-5p, miR-9-3p, miR-181d, and miR-130b, exhibited an inverse correlation with IGF-1 levels. The miR-181d, that targeted the most IGF-1-related cytokine genes, was significantly reduced in IGF-1-treated glioma cells. Statistical models incorporating both high-IGF-1 and low-miR-181d statuses better predicted poor patient survival, and can be used as an independent prognostic factor in glioblastomas. The C-C chemokine receptor type 1 (CCR1) and interleukin (IL)-1b demonstrated inverse correlations with miR-181d levels and associations with patient survival. miR-181d significantly attenuated IGF-1-upregulated CCR1 and IL-1b gene expressions. These findings demonstrate a distinct role for IGF-1 signaling in glioma progression via miR-181d/cytokine networks.

The miR-24-3p/p130Cas: a novel axis regulating the migration and invasion of cancer cells

MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression by suppressing translation or facilitating mRNA decay. Differential expression of miRNAs is involved in the pathogenesis of several diseases including cancer. Here, we investigated the role of-miR-24-3p as a downregulated miRNA in metastatic cancer. miR-24-3p was decreased in metastatic cancer and lower expression of miR-24-3p was related to poor survival of cancer patients. Consistently, ectopic expression of miR-24-3p suppressed the cell migration, invasion, and proliferation of MCF7, Hep3B, B16F10, SK-Hep1, and PC-3 cells by directly targeting p130Cas. Stable expression of p130Cas restored miR-24-3p-mediated inhibition of cell migration and invasion. These results suggest that miR-24-3p functions as a tumor suppressor and the miR-24-3p/p130Cas axis is a novel factor of cancer progression by regulating cell migration and invasion.

The microRNA-302b-inhibited insulin-like growth factor-binding protein 2 signaling pathway induces glioma cell apoptosis by targeting nuclear factor IA

MicroRNAs are small noncoding RNAs that post-transcriptionally control the expression of genes involved in glioblastoma multiforme (GBM) development. Although miR-302b functions as a tumor suppressor, its role in GBM is still unclear. Therefore, this study comprehensively explored the roles of miR-302b-mediated gene networks in GBM cell death. We found that miR-302b levels were significantly higher in primary astrocytes than in GBM cell lines. miR-302b overexpression dose dependently reduced U87-MG cell viability and induced apoptosis through caspase-3 activation and poly(ADP ribose) polymerase degradation. A transcriptome microarray revealed 150 downregulated genes and 380 upregulated genes in miR-302b-overexpressing cells. Nuclear factor IA (NFIA), higher levels of which were significantly related to poor survival, was identified as a direct target gene of miR-302b and was involved in miR-302b-induced glioma cell death. Higher NFIA levels were observed in GBM cell lines and human tumor sections compared with astrocytes and non-tumor tissues, respectively. NFIA knockdown significantly enhanced apoptosis. We found high levels of insulin-like growth factor-binding protein 2 (IGFBP2), another miR-302b-downregulated gene, in patients with poor survival. We verified that NFIA binds to the IGFBP2 promoter and transcriptionally enhances IGFBP2 expression levels. We identified that NFIA-mediated IGFBP2 signaling pathways are involved in miR-302b-induced glioma cell death. The identification of a regulatory loop whereby miR-302b inhibits NFIA, leading to a decrease in expression of IGFBP-2, may provide novel directions for developing therapies to target glioblastoma tumorigenesis.

Serum microRNA profiling in patients with glioblastoma: a survival analysis

Because circulating microRNAs (miRNAs) have drawn a great deal of attention as promising novel cancer diagnostics and prognostic biomarkers, we sought to identify serum miRNAs significantly associated with outcome in glioblastoma patients. To do this, we performed global miRNA profiling in serum samples from 106 primary glioblastoma patients. The study subjects were randomly divided into two sets: set one (n = 40) and set two (n = 66). Using a Cox regression model, 3 serum miRNAs (miR-106a-5p, miR-182, and miR-145-5p) and 5 serum miRNAs (miR-222-3p, miR-182, miR-20a-5p, miR-106a-5p, and miR-145-5p) were identified significantly associated with 2-year patient overall survival and disease-free survival (P < 0.05) in both sets and the combined set. We then created the miRNA risk scores to assess the total impact of the significant serum miRNAs on survival. The high risk scores were associated with poor patient survival (overall survival: HR = 1.92, 95% CI: 1.19, 10.23, and disease-free survival: HR = 2.03, 95%CI: 1.24, 4.28), and were independent of other clinicopathological factors. Our results suggest that serum miRNAs could serve as prognostic predictors of glioblastoma.

Dual Functional MicroRNA-186-5p Targets both FGF2 and RelA to Suppress Tumorigenesis of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is one of the most malignant cancers. MicroRNAs (miRs) were reported to play important roles in GBM recently. However, the role of a novel miR-186-5p in GBM tumorigenesis is still elusive. Using bioinformatics, miR-186-5p was identified as potential regulators of both fibroblast growth factor (FGF)-2 and NF-κB subunit RelA. Luciferase reporter assay was used to confirm the direct recognition FGF2 and RelA mRNAs by miR-186-5p. Invasion and migration assays were employed to study the effect of miR-186-5p on GBM cell growth in vitro. Xenograft tumor animal model was established to elucidate the in vivo function of miR-186-5p. MiR-186-5p directly targeted mRNAs of both FGF2 and RelA, and repressed their expressions. Invasive and migratory abilities of GBM cells and growth of xenograft tumors were significantly inhibited by miR-186-5p, which can be restored by re-introduction of FGF2 and RelA expressions. MiR-186-5p is a novel tumor suppressor miR that functions to inhibit tumorigenesis of GBM both in vitro and in vivo, by targeting both FGF2 and RelA. MiR-186-5p/FGF2/RelA pathway may be potentially used as molecular targets of in the clinical treatment of GBM.

MicroRNA expression patterns and signalling pathways in the development and progression of childhood solid tumours

The development of childhood solid tumours is tied to early developmental processes. These tumours may be complex and heterogeneous, and elucidating the aberrant mechanisms that alter the early embryonic environment and lead to disease is essential to our understanding of how these tumours function. MicroRNAs (miRNAs) are vital regulators of gene expression at all stages of development, and their crosstalk via developmental signalling pathways is essential for orchestrating regulatory control in processes such as proliferation, differentiation and apoptosis of cells. Oncogenesis, from aberrant miRNA expression, can occur through amplification and overexpression of oncogenic miRNAs (oncomiRs), genetic loss of tumour suppressor miRNAs, and global miRNA reduction from genetic and epigenetic alterations in the components regulating miRNA biogenesis. While few driver mutations have been identified in many of these types of tumours, abnormal miRNA expression has been found in a number of childhood solid tumours compared to normal tissue. An exploration of the network of key developmental pathways and interacting miRNAs may provide insight into the development of childhood solid malignancies and how key regulators are affected. Here we present a comprehensive introduction to the roles and implications of miRNAs in normal early development and childhood solid tumours, highlighting several tumours in depth, including embryonal brain tumours, neuroblastoma, osteosarcoma, Wilms tumour, and hepatoblastoma. In light of recent literature describing newer classifications and subtyping of tumours based on miRNA profiling, we discuss commonly identified miRNAs, clusters or families associated with several solid tumours and future directions for improving therapeutic approaches.

The role of micro-RNA in the regulation of signal pathways in gliomas

Gliomas are invasive brain tumors with high rates of recurrence and mortality. Glioblastoma multiforme (GBM) is the most deadly form of glioma with nearly 100% rate of recurrence and unfavorable prognosis in patients. Micro-RNAs (miR) are the class of wide-spread short non-coding RNAs that inhibit translation via binding to the mRNA of target genes. The aim of the present review is to analyze recent studies and experimental results concerning aberrant expression profiles of miR, which target components of the signaling pathways Hedgehog, Notch, Wnt, EGFR, TGFb, HIF1a in glioma/glioblastoma. Particularly, the interactions of miR with targets of 2-hydroxyglutarate (the product of mutant isocytrate dehydrogenase, R132H IDH1, which is specific for the glioma pathogenesis) have been considered in the present review. Detecting specific miRNAs in tissue and serum may serve as a diagnostic and prognostic tool for glioma, as well as for predicting treatment response of an individual patient, and potentially serving as a mechanism for creating personalized treatment strategies

A new function for miRNAs as regulators of autophagy

Autophagy is a self-digestive process regulated by an intricate network of factors able either to ensure the prosurvival function of autophagy or to convert it in a death pathway. Recently, the involvement of miRNAs in the regulation of autophagy networks has been reported. This review will summarize the main features of these small noncoding endogenous RNAs, focusing on their relevance in cancer and finally addressing their impact on autophagy.

SIRP Alpha Protein Downregulates in Human Astrocytoma: Presumptive Involvement of Hsa-miR-520d-5p and Hsa-miR-520d-3p

Astrocytomas are the most common brain tumors with poor survival in malignant forms. Signal regulatory protein alpha (SIRP alpha) is a transmembrane protein expressed on immune cells and macrophages and is reported to modulate tumor cell phagocytosis. In the present study, we investigated the involvement of miR-520d-5p and miR-520d-3p in regulation of SIRP alpha expression. Here, we report mRNA and protein expression profile of SIRP alpha in 39 surgically resected human astrocytoma tissue samples and 14 control brain tissue samples. Transcript expression pattern was studied by real-time PCR while Western blotting and immunohistochemistry were used to evaluate protein expression. Expression profile of miR-520d-5p and miR-520d-3p was studied by real-time PCR. Computational prediction was employed to analyze the binding of miR-520d-5p and miR-520d-3p for SIRP alpha mRNA. It is evident from preliminary investigation that SIRP alpha transcripts are expressed in control brain tissues, increased in low-grade (grade II) tumor tissues, and decreased with further grade progression (P < 0.05). SIRP alpha protein was moderately expressed in control brain tissues but under-expressed in low- and high-grade tissue samples (P < 0.05). Immunohistochemistry results further confirmed Western blot outcomes. Computational prediction supplemented with 3' and 5'UTR targeting analysis and correlation studies reveals that hsa-miR-520d-5p (P = 0.028, R ² = 0.94) (95 % CI 0.15 to 0.99) and hsa-miR-520d-3p (P = 0.027, R ² = 0.94) (95% CI 0.17 to 0.99) may be the putative microRNAs involved in regulation of SIRP alpha protein expression. Real-time PCR expression profile depicts that mature form of both miRNAs is significantly overexpressed in low-grade (GII) tumor tissue samples compared to control and high-grade (GIII and GIV) tissue samples. MiR-520d-5p and miR-520d-3p were found with expression pattern similar to SIRP alpha transcripts. We show that SIRP alpha protein is under-expressed in low and high grades of astrocytoma patients' tissue samples. Control brain tissues were found to be positive with SIRP alpha protein expression. Real-time PCR expression analysis confirms that miR-520d-5p and miR-520d-3p expression levels were significantly correlated with SIRP alpha transcripts in control, low-grade, and high-grade tissue samples. Computational prediction further evidenced for binding sites of these miRNAs on 3' and 5'UTR of SIRP alpha transcripts. Taken together, we predict that miR-520d-5p and miR-520d-3p may be having role in the regulation of under-expressed SIRP alpha protein expression.

The Inhibition of microRNA-128 on IGF-1-Activating mTOR Signaling Involves in Temozolomide-Induced Glioma Cell Apoptotic Death

Temozolomide (TMZ), an alkylating agent of the imidazotetrazine series, is a first-line chemotherapeutic drug used in the clinical therapy of glioblastoma multiforme, the most common and high-grade primary glioma in adults. Micro (mi)RNAs, which are small noncoding RNAs, post-transcriptionally regulate gene expressions and are involved in gliomagenesis. However, no studies have reported relationships between TMZ and miRNA gene regulation. We investigated TMZ-mediated miRNA profiles and its molecular mechanisms underlying the induction of glioma cell death. By performing miRNA microarray and bioinformatics analyses, we observed that expression of 248 miRNAs was altered, including five significantly upregulated and 17 significantly downregulated miRNAs, in TMZ-treated U87MG cells. miR-128 expression levels were lower in different glioma cells and strongly associated with poor survival. TMZ treatment significantly upregulated miR-128 expression. TMZ significantly enhanced miR-128-1 promoter activity and transcriptionally regulated miR-128 levels through c-Jun N-terminal kinase 2/c-Jun pathways. The overexpression and knockdown of miR-128 expression significantly affected TMZ-mediated cell viability and apoptosis-related protein expression. Furthermore, the overexpression of miR-128 alone enhanced apoptotic death of glioma cells through caspase-3/9 activation, poly(ADP ribose) polymerase degradation, reactive oxygen species generation, mitochondrial membrane potential loss, and non-protective autophagy formation. Finally, we identified that key members in mammalian target of rapamycin (mTOR) signaling including mTOR, rapamycin-insensitive companion of mTOR, insulin-like growth factor 1, and PIK3R1, but not PDK1, were direct target genes of miR-128. TMZ inhibited mTOR signaling through miR-128 regulation. These results indicate that miR-128-inhibited mTOR signaling is involved in TMZ-mediated cytotoxicity. Our findings may provide a better understanding of cytotoxic mechanisms of TMZ involved in glioblastoma development.

MicroRNAs in glioblastoma multiforme pathogenesis and therapeutics

Glioblastoma multiforme (GBM) is the most common and lethal cancer of the adult brain, remaining incurable with a median survival time of only 15 months. In an effort to identify new targets for GBM diagnostics and therapeutics, recent studies have focused on molecular phenotyping of GBM subtypes. This has resulted in mounting interest in microRNAs (miRNAs) due to their regulatory capacities in both normal development and in pathological conditions such as cancer. miRNAs have a wide range of targets, allowing them to modulate many pathways critical to cancer progression, including proliferation, cell death, metastasis, angiogenesis, and drug resistance. This review explores our current understanding of miRNAs that are differentially modulated and pathologically involved in GBM as well as the current state of miRNA-based therapeutics. As the role of miRNAs in GBM becomes more well understood and novel delivery methods are developed and optimized, miRNA-based therapies could provide a critical step forward in cancer treatment.