Long non-coding RNA HOTAIR acts as a competing endogenous RNA to promote glioma progression by sponging miR-126-5p

The Role of Long Non-Coding RNAs in Thyroid Cancer

Thyroid cancer, the most common endocrine malignancy, has become the most commonly diagnosed malignant solid tumor. Moreover, some cases have poor prognosis, and the survival period is only 3-5 months. Long noncoding RNAs (lncRNAs) are a group of functional RNA molecules more than 200 nucleotides in length that lack the ability to encode protein but participate in all aspects of gene regulation. Functionally, many lncRNAs play essential roles in epigenetic regulation at transcriptional and post-transcriptional levels via various molecular mechanisms. Recent studies have discovered important roles for lncRNAs during the complex process of carcinogenesis in thyroid cancer. In this review, we focus on lncRNAs dysregulated in thyroid cancer and summarize recently reported associations between lncRNAs and thyroid cancer in order to demonstrate the significant value of lncRNAs in diagnosis and treatment.

Non-Coding RNAs as Key Regulators of Glutaminolysis in Cancer

Cancer cells exhibit exacerbated metabolic activity to maintain their accelerated proliferation and microenvironmental adaptation in order to survive under nutrient-deficient conditions. Tumors display an increase in glycolysis, glutaminolysis and fatty acid biosynthesis, which provide their energy source. Glutamine is critical for fundamental cellular processes, where intermediate metabolites produced through glutaminolysis are necessary for the maintenance of mitochondrial metabolism. These include antioxidants to remove reactive oxygen species, and the generation of the nonessential amino acids, purines, pyrimidines and fatty acids required for cellular replication and the activation of cell signaling. Some cancer cells are highly dependent on glutamine consumption since its catabolism provides an anaplerotic pathway to feed the Krebs cycle. Intermediate members of the glutaminolysis pathway have been found to be deregulated in several types of cancers and have been proposed as therapeutic targets and prognostic biomarkers. This review summarizes the main players in the glutaminolysis pathway, how they have been found to be deregulated in cancer and their implications for cancer maintenance. Furthermore, non-coding RNAs are now recognized as new participants in the regulation of glutaminolysis; therefore, their involvement in glutamine metabolism in cancer is discussed in detail.

The New Biomarker for Cervical Squamous Cell Carcinoma and Endocervical Adenocarcinoma (CESC) Based on Public Database Mining

To reconstruct the ceRNA biological network of cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) and to select an appropriate mRNA as a biomarker that could be used for CESC early diagnosis and prognosis evaluation. We downloaded CESC data from the TCGA public database, and statistical analysis was conducted with the R software to find out differential expressed genes encoding for lncRNAs, miRNAs, and mRNAs. The differentially expressed mRNAs (DEmRNAs) screened in the ceRNA network were analyzed for survival to find the mRNAs with significantly linked to the survival prognosis. These mRNAs were searched in the Pathological Atlas to identify the final appropriate mRNAs. Differential expression analysis revealed 773 lncRNAs, 94 miRNAs, and 2466 mRNAs. Survival analysis of DEmRNAs in the ceRNA network indicated that ADGRF4, ANXA8L1, HCAR3, IRF6, and PDE2A (P < 0.05) were negatively correlated with survival time. Verification of these six DEmRNAs in the Pathology Atlas indicated that PDE2A was a possible biomarker for CESC patients. PDE2A might be a biomarker for early diagnosis and prognosis evaluation of CESC patients, but due to the lack of available data, further studies may be needed for confirmation.

Construction of lncRNA-associated ceRNA networks to identify prognostic lncRNA biomarkers for glioblastoma

Long noncoding RNAs (lncRNAs) serve as competitive endogenous RNAs (ceRNAs) that play significant regulatory roles in the pathogenesis of tumors. However, the role of lncRNAs, especially the lncRNA-related ceRNA regulatory network, in glioblastoma (GBM) has not been fully elucidated. The goal of the current study was to construct lncRNA-microRNA-mRNA-related ceRNA networks for further investigation of their mechanism of action in GBM. We downloaded data from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases and identified differential lncRNAs, microRNAs (miRNAs), and messenger RNAs (mRNAs) associated with GBM. A ceRNA network was constructed and analyzed to examine the relationship between lncRNAs and patients' overall survival. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGGs) were used to analyze the related mRNAs to indirectly explain the mechanism of action of lncRNAs. The potential effective drugs for the treatment of GBM were identified using the connectivity map (CMap). After integrated analysis, we obtained a total of 210 differentially expressed lncRNAs, 90 differentially expressed miRNAs, and 2508 differentially expressed mRNAs (DEmRNAs) from the TCGA and GEO databases. Using these differential genes, we constructed a lncRNA-associated ceRNA network. Six lncRNAs in the ceRNA network were associated with the overall survival of patients with GBM. Through KEGG analysis, it was found that the DEmRNAs involved in the network are related to cancer-associated pathways, for instance, mitogen-activated protein kinase and Ras signaling pathways. CMap analysis revealed four small-molecule compounds that could be used as drugs for the treatment of GBM. In this study, a multi-database joint analysis was used to construct a lncRNA-related ceRNA network to help identify the regulatory functions of lncRNAs in the pathogenesis of GBM.

LncRNA HOTAIR targets miR-126-5p to promote the progression of Parkinson's disease through RAB3IP

Parkinson's disease (PD) is a common neurological disorder characterized by dopaminergic (DA) neuron degeneration and death in the midbrain, and the long noncoding RNA HOTAIR has been shown to affect disease progression in PD. In this study, we aimed to further illustrate the molecular mechanism of HOTAIR in PD. Bioinformatics analysis was utilized to determine the potential downstream targets of HOTAIR in PD. Luciferase assay and the RNA Binding Protein Immunoprecipitation (RIP) assay were used to validate the existence of binding sites between competing endogenous RNAs (ceRNAs). Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting indicated that HOTAIR and RAB3IP increased while miR-126-5p decreased in PD cells and PD mice. Additionally, the CCK-8 assay and flow cytometric analysis indicated that the knockdown of HOTAIR and RAB3IP and the overexpression of miR-126-5p significantly increased cell proliferation and reduced apoptosis in PD cells. Furthermore, the results of in vivo experiments suggested that knockdown of HOTAIR expression increased the number of TH-positive cells and the number of α-synuclein-positive cells decreased while reducing the apoptosis rate among DA neurons. Our study confirmed that HOTAIR promotes PD progression by regulating miR-126-5p and RAB3IP in a ceRNA-dependent manner and further clarified how HOTAIR works in PD.

Retracted Article: LncRNA SNHG5 regulates the cell viability and apoptosis of glioma cells by the miR-1297/KPNA2 axis

Long non-coding RNA small nucleolar RNA host gene 5 (lncRNA SNHG5) has been reported to participate in the occurrence and development of glioma. However, the function and underlying molecular mechanisms of SNHG5 in glioma remain largely unknown. The expressions of SNHG5, microRNA-1297 (miR-1297) and karyopherin subunit alpha 2 (KPNA2) in glioma tissues and cells were evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) or western blot. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry were used to detect cell viability and apoptosis, respectively. Western blot was also performed to detect the expressions of autophagy-associated proteins. The relationship among lncRNA SNHG5, miR-1297 and KPNA2 was verified by luciferase reporter assay and RNA immunoprecipitation (RIP) assay. SNHG5 and KPNA2 were over expressed, and the level of miR-1297 was down-regulated in glioma tissues and cell lines. Knockdown of SHNG5 promoted apoptosis, while suppressing cell viability and autophagy of A172 and LN340 cells. Meanwhile, SHNG5 harbored the binding sites with miR-1297, and a negative correlation between the expression of SNHG5 and miR-1297 in glioma tissues was also observed. Interestingly, silencing of miR-1297 undermined the SHNG5 depletion-mediated effect on cell viability, apoptosis, and autophagy. KPNA2 was a direct target of miR-1297, and negatively regulated by miR-1297. More importantly, gain of KPNA2 mitigated the effect of SHNG5l knockdown on glioma cells. Silencing of SNHG5 had an implication in inhibiting apoptosis and stimulating cell viability and autophagy by the miR-1297/KPNA2 axis in glioma.

Long non-coding RNA small nucleolar RNA host gene 5 (lncRNA SNHG5) has been reported to participate in the occurrence and development of glioma.

Long noncoding RNA LINC00518 acts as a competing endogenous RNA to promote the metastasis of malignant melanoma via miR-204-5p/AP1S2 axis

Long intergenic nonprotein coding RNA 518 (LINC00518) has been shown to promote cancer cell growth and metastasis in some human tumors. Although it has been reported that LINC00518 is dysregulated in melanoma, its exact role and molecular mechanism in melanoma remain unclear. RNA-seq analysis and qRT-PCR was used to detect the expression of LINC00518 in melanoma tissues. Melanoma cases from The Cancer Genome Atlas (TCGA), GEO#GSE15605 and GEO#GSE24469 were included in this study. 3D migration, transwell and scratch wound assay were used to explore the role of LINC00518 in melanoma cells. Bioinformatics, luciferase reporter assays, MS2-RIP assay, RNA pull-down assay and RNA-ChIP assay were used to demonstrate the mechanism of LINC00518 in melanoma. We found that LICN00518 was significantly upregulated in melanoma tissue, and high LICN00518 level was an independent risk factor for melanoma patients. LICN00518 promoted the invasion and migration of melanoma cells. LICN00518 exerted its role by decoying miR-204-5p to upregulate Adaptor Related Protein Complex 1 Sigma 2 Subunit (AP1S2) expression. We also demonstrated that LICN00518 promoted melanoma metastasis in vivo through pulmonary metastasis assay. This result elucidates a new mechanism for LICN00518 in the metastasis of melanoma. LICN00518 may serve as a survival indicator and potential therapeutic target in melanoma patients.

3-Bromopyruvate inhibits the malignant phenotype of malignantly transformed macrophages and dendritic cells induced by glioma stem cells in the glioma microenvironment via miR-449a/MCT1

Bromopyruvate (3-BrPA) is a glycolysis inhibitor that has been reported to have a strong anti-tumour effect in many human tumours. Several studies have reported that 3-BrPA could inhibit glioma progression; however, its role on the interstitial cells in the glioma microenvironment has not been investigated. In previous studies, we found that in the glioma microenvironment, glioma stem cells can induce the malignant transformation of macrophages and dendritic cells. In this study, we focused on the effects of 3-BrPA on malignantly transformed macrophages and dendritic cells. First, we found that 3-BrPA inhibited the proliferation of malignantly transformed macrophages and dendritic cells in a dose-dependent and time-dependent manner. Further study indicated that 3-BrPA significantly decreased extracellular lactate and inhibited the clone formation, migration and invasion of malignantly transformed macrophages and dendritic cells. Using an online database and a series of experiments, we demonstrated that 3-BrPA inhibits the malignant progression of malignantly transformed macrophages and dendritic cells via the miR-449a/MCT1 axis. These findings built experimental basis for new approach against glioma.

LncRNA-XIST/microRNA-126 sponge mediates cell proliferation and glucose metabolism through the IRS1/PI3K/Akt pathway in glioma

Abnormal glucose metabolism may contribute to cancer progression. Glioma represents a cancer resulting from an imbalance between glucose metabolism and tumor growth. However, the molecular mechanisms responsible for dysregulated brain glucose metabolism and lactate accumulation in glioma remain to be elucidated. The present study identified a long noncoding RNA (lncRNA) X-inactive specific transcript (XIST) as a candidate to mediate glucose metabolism in glioma. Cell viability, migration, invasion, and resistance to apoptosis were evaluated in lncRNA-XIST-depleted glioblastoma cells by short hairpin RNA. Glucose uptake, lactate production, as well as levels of glucose transporter 1 (GLUT1) and GLUT3, were measured. Luciferase assay, RNA pull-down, and RNA immunoprecipitation were performed to validate the interactions among lncRNA-XIST, microRNA-126 (miR-126), and insulin receptor substrate 1 (IRS1). An in vivo analysis was carried out in nude mice bearing glioblastoma cell xenografts. The study found that lncRNA-XIST knockdown inhibited cell viability, migration, invasion, resistance to apoptosis, and glucose metabolism of glioblastoma cells. LncRNA-XIST functioned as a competing endogenous RNA of miR-126 and then regulated IRS1/PI3K/Akt pathway in glioblastoma cells. In vivo results demonstrated lncRNA-XIST knockdown reduces the tumorigenicity of glioblastoma cells. Taken together, we demonstrated a novel cellular mechanism that was dependent of the lncRNA-XIST/miR-126/IRS1/PI3K/Akt pathway in enhanced glucose metabolism in glioma.

Long non-coding RNA HOTAIR functions as a competitive endogenous RNA to regulate PRAF2 expression by sponging miR-326 in cutaneous squamous cell carcinoma

Background

LncRNAs may exert a regulatory effect in tumorigenesis. Although the expression of lncRNA HOTAIR has been confirmed to be notably elevated in the tissues of CSCC, its biological mechanism in CSCC is still unknown.

Methods

HOTAIR expression level in CSCC cell lines was monitored via qRT-PCR. Then CCK-8 assay, Transwell assay and EdU assay were adopted to detect cell migration and proliferation. Meanwhile, through bioinformatics analysis and luciferase reporter gene detection, a new target of HOTAIR was identified. Additionally, Western blotting and RIP analysis were adopted to discuss the possible mechanism.

Results

HOTAIR expression in CSCC cell lines exhibited an obvious elevation. Cell function analysis revealed that HOTAIR overexpression remarkably facilitated CSCC cell migration, proliferation and EMT process, which were impeded by down-regulation of HOTAIR. Furthermore, HOTAIR competitively bound to miR-326, so as to positively modulate miR-326 expression.

Conclusions

These results present that HOTAIR, as a ceRNA, regulates PRAF2 expression by competitive binding to miR-326 during CSCC.

The long noncoding RNA ZFAS1 promotes the progression of glioma by regulating the miR-150-5p/PLP2 axis

Numerous studies have reported that long noncoding RNA (lncRNA) dysregulation is involved in the progression of many malignant tumors, including glioma. The lncRNA ZNFX1 antisense RNA 1 (ZFAS1) plays an oncogenic role in various malignant tumors, such as gastric cancer and hepatocellular carcinoma. However, the underlying molecular mechanism of ZFAS1 in glioma has not been fully clarified. In this study, we found that the expression of ZFAS1 was upregulated in both glioma tissues and cell lines. Functional experiments revealed that ZFAS1 promoted glioma proliferation, migration and invasion, and increased resistance to temozolomide in vitro. By using online databases, RNA pull-down assays and luciferase reporter assays, ZFAS1 was demonstrated to act as a sponge of miR-150-5p. Furthermore, proteolipid protein 2 (PLP2) was shown to be the functional target of miR-150-5p. Rescue experiments revealed that ZFAS1 regulated the expression of PLP2 by sponging miR-150-5p. Finally, a xenograft tumor assay demonstrated that ZFAS1 promoted glioma growth in vivo. Our results showed that ZFAS1 promoted glioma malignant progression by regulating the miR-150-5p/PLP2 axis, which may provide a potential therapeutic target for the treatment of glioma.

Long non-coding RNA MYOSLID functions as a competing endogenous RNA to regulate MCL-1 expression by sponging miR-29c-3p in gastric cancer

Objective

Long non‐coding RNA (lncRNA) has become an important regulator of many human malignancies. However, the biological role and clinical significance of most lncRNA in gastric cancer (GC) remain unclear.

Methods

We investigate the biological function, mechanism of action and clinical expression of lncRNA MYOSLID in GC. First, we analysed the differential expression of lncRNA MYOSLID in GC tissues and non‐cancerous tissues by analysing the sequencing data obtained from The Cancer Genome Atlas. Subsequently, we verified that lncRNA MYOSLID regulates the proliferation and apoptosis of GC cells by acting as a ceRNA against miR‐29c‐3p. The nude mouse xenograft was used to further confirm the functional significance of lncRNA MYOSLID in vivo.

Results

We found for the first time that the expression of lncRNA MYOSLID was significantly up‐regulated in GC tissues, and the up‐regulation of lncRNA MYOSLID in GC was correlated with tumour size, AJCC stage, depth of invasion and survival time. In addition, apoptosis and growth arrest can be induced in vitro after knockdown of lncRNA MYOSLID, which inhibits tumorigenesis in mouse xenografts in vivo. Further in‐depth studies revealed that lncRNA MYOSLID acts as a ceRNA of miR‐29c‐3p, resulting in de‐repression of its downstream target gene MCL‐1.

Conclusion

The lncRNA MYOSLID‐miR‐29c‐3p‐MCL‐1 axis plays a key role in the development of GC. Our findings may provide potential new targets for the diagnosis and treatment of human GC.

Long non-coding RNA, HOTAIRM1, promotes glioma malignancy by forming a ceRNA network

Long non-coding RNAs play critical roles in tumorigenesis and the immune process. In this study, RNA sequencing data for 946 glioma samples from The Cancer Genome Atlas and the Chinese Glioma Genome Atlas databases were analyzed to evaluate the prognostic value and function of homeobox A transcript antisense RNA myeloid-specific (HOTAIRM)1. HOTAIRM1 expression was associated with clinical and molecular features of glioma: patients with high HOTAIRM1 expression were more likely to be classified as malignant cases, and elevated HOTAIRM1 level was associated with shorter survival time in subgroups stratified by clinical and molecular features. A multivariate Cox regression analysis showed that HOTAIRM1 was an independent prognostic factor for patient outcome. In vitro experiments revealed that HOTAIRM1 knockdown suppressed the malignant behavior of glioma and increased tumor sensitivity to temozolomide. The results of an in silico analysis indicated that HOTAIRM1 promotes the malignancy of glioma by acting as a sponge for microRNA (miR)-129-5p and miR-495-3p. HOTAIRM1 overexpression was also associated with immune activation characterized by enhanced T cell-mediated immune and inflammatory responses. These results suggest that HOTAIRM1 is a prognostic biomarker and potential therapeutic target in glioma.

Down-regulation of long non-coding RNA HOTAIR inhibits invasion and migration of oesophageal cancer cells via up-regulation of microRNA-204

Oesophageal cancer is a progressive tumour with high mortality. However, therapies aimed at treating oesophageal cancer remain relatively limited. Accumulating studies have highlighted long non‐coding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR), microRNA‐204 (miR‐204) and homeobox C8 (HOXC8) in the progression of oesophageal cancer. Herein, we tried to demonstrate the function of HOTAIR, miR‐204 and HOXC8 in oesophageal cancer and their relationship. Differentially expressed genes involved in oesophageal cancer were identified. The endogenous expression of HOTAIR and miR‐204 in oesophageal cancer cell lines was altered to elucidate their effects and to identify the interaction among HOTAIR, miR‐204 and HOXC8. We also explored the underlying regulatory mechanisms of HOTAIR and miR‐204 with siRNA against HOTAIR, miR‐204 mimic or miR‐204 inhibitor. Cell proliferation, migration, invasion and apoptosis were subsequently detected. Xenograft in nude mice was induced to evaluate tumourigenicity. miR‐204 was down‐regulated, while HOTAIR and HOXC8 were up‐regulated in the oesophageal cancer tissues. HOTAIR could competitively bind to miR‐204 and miR‐204 could further target HOXC8. The oesophageal cancer cells treated with si‐HOTAIR or miR‐204 mimic exhibited decreased expression levels of HOXC8, Vimentin and MMP‐9, but increased E‐cadherin level. Silenced HOTAIR or elevated miR‐204 inhibited proliferation, migration and invasion, along with stimulated apoptosis of oesophageal cancer cells. In summary, our results show that lncRNA HOTAIR could specifically bind to miR‐204 as a competing endogenous RNA and regulate miR‐204 and HOXC8. Hence, down‐regulation of HOTAIR could inhibit progression of oesophageal cancer, indicating a novel target for oesophageal cancer treatment.

Long non-coding RNA SNHG5 promotes glioma progression via miR-205/E2F3 axis

In recent years, many studies have reported on the abnormal expression and correlation of long non-coding RNAs (lncRNAs) in tumours. However, the accurate molecular mechanism of lncRNAs in glioma is still in its infancy. In the present study, we aimed to explore the molecular mechanism of small nucleolar RNA host gene 5 (SNHG5) in glioma progression. First, we found that SNHG5 expression was higher in glioma and was related to glioma glucose uptake, migration and invasion. Second, through a series of assays, we concluded that SNHG5 acts as a sponge for miR-205, which inhibits tumour growth in glioma by targeting E2F transcription factor 3 (E2F3). Third, using a xenograft mouse model, we demonstrated that SNHG5 regulates tumourigenesis in vivo. Taken together, our results show that the SNHG5/miR-205/E2F3 axis is involved in glioma progression and may provide a new therapeutic target for the diagnosis and therapy of glioma.

Glutaminase C Regulates Microglial Activation and Pro-inflammatory Exosome Release: Relevance to the Pathogenesis of Alzheimer's Disease

Microglial activation is a key pathogenic process at the onset of Alzheimer’s disease (AD). Identifying regulators of microglial activation bears great potential in elucidating causes and mechanisms of AD and determining candidates for early intervention. Previous studies demonstrate abnormal elevation of glutaminase C (GAC) in HIV-infected or immune-activated microglia. However, whether GAC elevation causes microglial activation remains unknown. In this study, we found heightened expression levels of GAC in early AD mouse brain tissues compared with those in control littermates. Investigations on an in vitro neuroinflammation model revealed that GAC is increased in primary mouse microglia following pro-inflammatory stimulation. To model GAC elevation we overexpressed GAC by plasmid transfection and observed that GAC-overexpression shift the microglial phenotype to a pro-inflammatory state. Treatment with BPTES, a glutaminase inhibitor, reversed LPS-induced microglial activation and inflammation. Furthermore, we discovered that GAC overexpression in mouse microglia increased exosome release and changed exosome content, which includes specific packaging of pro-inflammatory miRNAs that activate microglia. Together, our results demonstrate a causal effect of GAC elevation on microglial activation and exosome release, both of which promote the establishment of a pro-inflammatory microenvironment. Therefore, GAC may have important relevance to the pathogenesis of AD.

The long non-coding RNA SNHG1 promotes glioma progression by competitively binding to miR-194 to regulate PHLDA1 expression

Long non-coding RNAs (lncRNAs) play a vital role in tumourigenesis, including that of glioma. Small nucleolar RNA host gene 1 (SNHG1) is a relatively novel lncRNA that is involved in the development of multiple human tumours. However, its underlying molecular mechanism in glioma has not been completely clarified. In this study, we show that SNHG1 is overexpressed in glioma tissues and cell lines. A series of functional assays suggested that SNHG1 promotes glioma progression in vitro and in vivo. Next, through online databases, a luciferase reporter assay and an RNA pull-down assay, we confirmed that SNHG1 functions as a sponge for miR-194, which acts as a suppressor in glioma. We also verified that pleckstrin homology like domain family A, member 1 (PHLDA1) is the functional target of miR-194. Moreover, rescue experiments demonstrated that SNHG1 regulates PHLDA1 expression in a miR-194-dependent manner. Taken together, our study shows that SNHG1 promotes glioma progression by competitively binding to miR-194 to regulate PHLDA1 expression, which may provide a novel therapeutic strategy for glioma.

Long noncoding RNA HOXD-AS2 regulates cell cycle to promote glioma progression

Now, numerous exciting findings have been found that long noncoding RNAs (lncRNAs) play a vital role in cancer malignant progression. However, their potential involvement in glioma is not well understood. Here, we performed a high-throughput microarray to detect the lncRNA expression profiles between glioma cell lines and normal astrocyte cell lines. HOXD-AS2 was increased in glioma cells and it was associated with glioma grade and poor prognosis. Loss of HOXD-AS2 can inhibit glioma cell growth by inducing cell-cycle G1 arrest in vitro. The proliferation of glioma was inhibited followed by knocking down the expression of HOXD-AS2 not only in subcutaneous injection model but also in orthotopic implantation model. These findings indicate that HOXD-AS2 promotes the glioma progression and may serve as a potential target for glioma diagnosis and therapy.

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.

Long noncoding RNA GACAT3 promotes glioma progression by sponging miR-135a

The long noncoding RNA (lncRNA) gastric cancer associated transcript 3 (GACAT3) has been reported to play important roles in human tumorigenesis. However, its expression pattern, functions, and underlying mechanism in glioma remain unclear. In the present study, we showed that GACAT3 is upregulated in glioma tissues and cell lines. Through online databases, luciferase reporter assays and RNA immunoprecipitation (RIP) assays, we determined that GACAT3 acts as a competing endogenous RNA (ceRNA) for microRNA (miR)-135a, which was downregulated and performed as a tumor inhibitor in glioma. Further, nicotinamide phosphoribosyl transferase (NAMPT) was confirmed as a target gene of miR-135a by a series of gain- and loss-of-function assays. Overall, the present study was the first to show that GACAT3 regulates the expression of NAMPT to promote glioma progression by sponging miR-135a. These findings provide a promising therapy strategy for glioma.

MiRNA-139-3p inhibits the proliferation, invasion, and migration of human glioma cells by targeting MDA-9/syntenin

Gliomas are the most common primary malignant brain tumor in adults. Although these tumors are aggressive and frequently lethal, there are currently few therapeutic approaches available to prolong patient survival. MicroRNAs play important roles in regulating the expression of genes that control diverse cellular processes. Here, we investigated the expression and function of miR-139-3p in gliomas using clinical specimens, cultured cells, and a mouse xenograft tumor model. We found that miR-139-3p expression is markedly lower in human glioma tissues than in normal brain tissues. We identified melanoma differentiation-associated gene-9 (MDA-9)/syntenin, an adaptor protein implicated in tumor metastasis, as a novel direct target of miR-139-3p and showed that syntenin mRNA and miR-139-3p levels were inversely correlated in clinical specimens (r = -0.6817, P = 0.0002). Overexpression of miR-139-3p in human glioma cell lines inhibited cell proliferation, migration, and invasion, and these effects were rescued by co-transfection with syntenin. Our results indicate that miR-139-3p plays a significant role in controlling behaviors associated with the malignant progression of gliomas, and we identify the miR-139-3p-syntenin axis as a potential therapeutic target for glioma.

LncRNA LOC728196/miR-513c axis facilitates glioma carcinogenesis by targeting TCF7

Numerous long noncoding RNAs (lncRNAs) are reported to be dysregulated in glioma. However, how lncRNA participates in the process of glioma development and progression still remains elusive. Here, we identified a novel lncRNA LOC728196 highly expressed in glioma tissues. LOC728196 high expression predicts low survival rate in patients. Our data proved that LOC728196 knockdown repressed cellular growth, migration and invasion in vitro. Silencing LOC728196 led to impaired growth of glioma in vivo. Mechanistic studies further demonstrated that LOC728196 acts as the sponge for miR-513c to upregulate TCF7 expression. We observed a reciprocal inhibition between LOC728196 and miR-513c. Rescue assay showed that either inhibition of miR-513c or TCF7 overexpression restored the abilities of proliferation, migration and invasion in LOC728196-silenced glioma cells. Taken together, our study provides a comprehensive investigation on the role of LOC728196 in glioma progression and contributes to understanding the vital role of competing endogenous RNA (ceRNA).