A critical overview of long non-coding RNA in glioma etiology 2016: an update

ADAMTS9-AS1 Long Non‑coding RNA Sponges miR‑128 and miR-150 to Regulate Ras/MAPK Signaling Pathway in Glioma

Glioma is a malignancy of the central nervous system with a poor prognosis. Therefore, the elaboration of its molecular features creates therapeutic opportunities. Looking for the regulatory non-coding RNAs (lncRNAs and miRNAs) that are involved in glioma incidence/progression, RNA-seq analysis introduced upregulated ADAMTS9-AS1 as a bona fide candidate that sponges miR-128 and miR-150 and shows the negative correlation of expression with them. Then, RT-qPCR verified the upregulation of ADAMTS9-AS1 in glioma tissues and cell lines. Furthermore, dual-luciferase assay supported that cytoplasmic ADAMTS9-AS1 is capable of sponging miR-128 and miR-150, which are known as regulators of Ras/MAPK, PI3K, and Wnt pathways. Following the overexpression of ADAMTS9-AS1 in 1321N1 and U87 glioma cells, tyrosine kinase receptors (IGF1R and TrkC), as well as Wnt receptors (Lrp6 and Fzd) were upregulated, detected by RT-qPCR. Furthermore, downstream genes of both Ras/MAPK and Wnt pathways were upregulated. Finally following the ADAMTS9-AS1 overexpression, upregulation of Ras/MAPK and Wnt signaling pathways was verified through western blotting and Top/Fop flash assay, respectively. At the cellular level, ADAMTS9-AS1 overexpression brought about reduced sub-G1 cell population, increased proliferation rate, reduced apoptosis level, increased migration rate, shortened Bax/Bcl2 ratio, induced EMT, and stemness characteristics of transfected cells, detected by flow cytometry, MTT assay, scratch test, and RT-qPCR. Overall, these results introduced ADAMTS9-AS1 as an oncogene that upregulates Ras/MAPK and Wnt pathways through sponging of the miR-128 and miR-150 in glioma cells. The outcome of ADAMTS9-AS1 expression is more aggression of the glioma cells through increased EMT and stemness characteristics. These features candidate ADAMTS9-AS1 locus for glioma therapy. As a result, we discovered the oncogenic properties of ADAMTS9-AS1 in glioma cancer. It sponges miR-128 and miR-150 and subsequently overstimulates RAS/MAPK and Wnt signaling pathways, particularly at the receptors level. Thus, ADAMTS9-AS1 increases proliferation, migration, and stemness in glioma cell lines. A schematic representation showing the functional effect of ADAMTS9-AS1.

LINC02381-ceRNA exerts its oncogenic effect through regulation of IGF1R signaling pathway in glioma

PURPOSE

LncRNAs play essential roles in the cellular and molecular biology of glioma. Some LncRNAs exert their role through sponging miRNAs and regulating multiple signaling pathways. LINC02381 is involved in several cancer types as either oncogene or tumor suppressor. Here, we intended to find the molecular mechanisms of the LINC02381 effect during the glioma progression in related cell lines.

METHODS AND RESULTS

RNA-seq data analysis indicated the oncogenic characteristics of LINC02381, and RT-qPCR results confirmed its upregulation compared to normal tissues. Besides its expression was relatively stronger in invasive glioma cell lines. Furthermore, in silico analysis revealed LINC02381 is concentrated in the cytoplasm and predicted its sponging effect against miR-128 and miR-150, which was verified through dual luciferase assay. When LINC02381 was overexpressed in 1321N1, U87, and A172 cell lines, IGF1R and TrkC receptors as well as their downstream pathways (PI3K and RAS/MAPK), were upregulated, detected by RT-qPCR, and verified by western analysis. Consistently, LINC02381 overexpression was followed by an increased proliferation rate of transfected glioma cell lines, detected by flow cytometry and MTT assay, and RT-qPCR. It also resulted in elevated EMT and stemness markers expression level, increased migration rate, and reduced apoptosis rate, detected by RT-qPCR, western analysis, scratch test, and Annexin/PI flow cytometry analysis, respectively.

CONCLUSION

The overall results indicated that LINC02381 exerts its oncogenic effect in glioma cells through sponging miR-128 and miR-150 to upregulate the IGF1R signaling pathway. Our results introduce LINC02381 and miR-128, and miR-150 as potential prognosis and therapy targets for the treatment of glioma.

Large-Scale Transcriptomics-Driven Approach Revealed Overexpression of CRNDE as a Poor Survival Prognosis Biomarker in Glioblastoma

Glioblastoma is the most common and malignant brain malignancy worldwide, with a 10-year survival of only 0.7%. Aggressive multimodal treatment is not enough to increase life expectancy and provide good quality of life for glioblastoma patients. In addition, despite decades of research, there are no established biomarkers for early disease diagnosis and monitoring of patient response to treatment. High throughput sequencing technologies allow for the identification of unique molecules from large clinically annotated datasets. Thus, the aim of our study was to identify significant molecular changes between short- and long-term glioblastoma survivors by transcriptome RNA sequencing profiling, followed by differential pathway-activation-level analysis. We used data from the publicly available repositories The Cancer Genome Atlas (TCGA; number of annotated cases = 135) and Chinese Glioma Genome Atlas (CGGA; number of annotated cases = 218), and experimental clinically annotated glioblastoma tissue samples from the Institute of Pathology, Faculty of Medicine in Ljubljana corresponding to 2-58 months overall survival (n = 16). We found one differential gene for long noncoding RNA CRNDE whose overexpression showed correlation to poor patient OS. Moreover, we identified overlapping sets of congruently regulated differential genes involved in cell growth, division, and migration, structure and dynamics of extracellular matrix, DNA methylation, and regulation through noncoding RNAs. Gene ontology analysis can provide additional information about the function of protein- and nonprotein-coding genes of interest and the processes in which they are involved. In the future, this can shape the design of more targeted therapeutic approaches.

Integrative analysis of transcriptional profile reveals LINC00052 as a suppressor of breast cancer cell migration

BACKGROUND

Long-non-coding RNAs, a class of transcripts with lengths > 200 nt, play key roles in tumour progression. Previous reports revealed that LINC00052 (long intergenic non-coding RNA 00052) was strongly downregulated during breast cancer multicellular spheroids formation and suggested a role in cell migration and oxidative metabolism.

OBJECTIVE

To examine the function of LINC00052 in MCF-7 breast cancer cells.

METHODS

Loss-of-function studies were performed to evaluate LINC00052 role on MCF-7 breast cancer cells. Microarray expression assays were performed to determine genes and cellular functions modified after LINC00052 knockdown. Next, the impact of LINC00052 depletion on MCF-7 cell respiration and migration was evaluated.

RESULTS

1,081 genes were differentially expressed upon LINC00052 inhibition. Gene set enrichment analysis, Gene Ontology and Key Pathway Advisor analysis showed that signalling networks related to cell migration and oxidative phosphorylation were enriched. However, whereas LINC00052 knockdown in MCF-7 cells revealed marginal difference in oxygen consumption rates when compared with control cells, LINC00052 inhibition enhanced cell migration in vitro and in vivo, as observed using a Zebrafish embryo xenotransplant model.

CONCLUSION

Our data show that LINC00052 modulates MCF-7 cell migration. Genome-wide microarray experiments suggest that cancer cell migration is affected by LINC00052 through cytoskeleton modulation and Notch/β-catenin/NF-κB signalling pathways.

LncRNA MIR155HG Promotes Temozolomide Resistance by Activating the Wnt/β-Catenin Pathway Via Binding to PTBP1 in Glioma

Temozolomide (TMZ) is widely used for glioma therapy in the clinic. Currently, the development of TMZ resistance has largely led to poor prognosis. However, very little is understood about the role of MIR155HG, as a long noncoding RNA, in TMZ resistance. In our study, MIR155HG level was markedly higher in glioma patients than in normal controls and that poor survival was positively correlated with MIR155HG expression. It was apparent that TMZ sensitivity was promoted by downregulation of MIR155HG, and this could be reversed by MIR155HG overexpression in vivo and in vitro. Furthermore, polypyrimidine tract binding protein 1 (PTBP1) was proven to bind with MIR155HG and to regulate MIR155HG-related TMZ resistance. Mechanistic investigation showed that the expression levels of both MIR155HG and PTBP1 influenced the expression of relevant proteins in the Wnt/β-catenin pathway. Collectively, the study demonstrated that the knockdown of MIR155HG increased glioma sensitivity to TMZ by inhibiting Wnt/β-catenin pathway activation via potently downregulating PTBP1.

Identification of Potential Prognostic Long Non-Coding RNA Biomarkers for Predicting Recurrence in Patients with Cervical Cancer

Background

Cervical cancer (CC) is one of the most common malignant tumors in women, and its treatment is often accompanied by high recurrence. We aimed to identify the long non-coding RNAs (lncRNAs) associated with CC recurrence.

Methods

We downloaded lncRNAs expression data of CC patients from The Cancer Genome Atlas (TCGA) dataset and used Cox regression models to analyze the lncRNAs relationship with CC recurrence. The significantly associated lncRNAs were utilized to construct a recurrence risk score (RRS) model. Bioinformatics analyses were used to assess the potential role of the critical lncRNAs in CC recurrence. The effect of critical lncRNAs on CC phenotype was determined by in vitro experiments.

Results

Using Cox regression analysis, four lncRNAs, ie, HCG11, CASC15, LINC00189, and LINC00905, were markedly associated with worse recurrence-free survival (RFS) of CC, whereas three lncRNAs, including HULC, LINC00173, and MIR22HG, were the opposite. After constructing the RRS model, Kaplan-Meier analysis revealed that patients with high RRS had significantly increased risk of recurrence. Among the 20 types of tumors in the TCGA database which all had adjacent normal tissues, MIR22HG and HCG11were significantly downregulated in 18 and 10 types of tumors including CC, respectively. Increased MIR22HG was significantly relevant to decreased risks of recurrence among the subgroups of age at diagnosis < 45 (Hazard Ratio (HR) = 0.26), stage I/II (HR = 0.33), T stage I/II (HR = 0.30), chemotherapy (HR = 0.18), and molecular therapy (HR = 0.16). Functionally, elevated MIR22HG expression could suppress CC cell proliferation, migration and invasion.

Conclusion

MIR22HG has a fundamental role in CC recurrence and could be served as a potential prognostic biomarker.

LncRNA FOXD1-AS1 acts as a potential oncogenic biomarker in glioma

AIMS

Altered activities of long noncoding RNAs (lncRNAs) have been associated with cancer development, and lncRNA FOXD1-AS1 (FOXD1-AS1) is the antisense transcript of the gene encoding for FOXD1, known for its role as an oncogene in several tumor types including glioma. However, the role of FOXD1-AS1 in the differentiation and progression of glioma is not well known.

METHODS

Expression profile chip and qPCR were used to screen and identify FOXD1-AS1. Glioma cells were transfected with siRNA or eukaryotic expression vector to observe FOXD1-AS1 function in vitro and in vivo. Dual luciferase reporter gene analysis, Western blot, and ChIRP-MS were used to detect microRNAs and protein that combine with FOXD1-AS1.

RESULTS

FOXD1-AS1 was upregulated and directly correlated with the glioma grade, and it was localized in both the nucleus and the cytoplasm of the glioma cell. FOXD1-AS1 silencing caused tumor suppressive effects via inhibiting cell proliferation, migration, and apoptosis, while FOXD1-AS1 overexpression resulted in opposite effects. Additionally, in vivo experiments showed that FOXD1-AS1 knockdown reduced tumor volume and weight. More importantly, mechanical studies revealed that FOXD1-AS1 targeted both miR339-5p and miR342-3p (miR339/342). Furthermore, protein eukaryotic translation initiation factor 5 subunit A (eIF5a) resulted a direct target of FOXD1-AS1.

CONCLUSIONS

These data indicated that FOXD1-AS1, a miR339/342 target, affected biological processes via protein eIF5a; thus, it might be considered as a new therapeutic target for glioblastoma.

The protean world of non-coding RNAs in glioblastoma

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

Testing of library preparation methods for transcriptome sequencing of real life glioblastoma and brain tissue specimens: A comparative study with special focus on long non-coding RNAs

Current progress in the field of next-generation transcriptome sequencing have contributed significantly to the study of various malignancies including glioblastoma multiforme (GBM). Differential sequencing of transcriptomes of patients and non-tumor controls has a potential to reveal novel transcripts with significant role in GBM. One such candidate group of molecules are long non-coding RNAs (lncRNAs) which have been proved to be involved in processes such as carcinogenesis, epigenetic modifications and resistance to various therapeutic approaches. To maximize the value of transcriptome sequencing, a proper protocol for library preparation from tissue-derived RNA needs to be found which would produce high quality transcriptome sequencing data and increase the number of detected lncRNAs. It is important to mention that success of library preparation is determined by the quality of input RNA, which is in case of real-life tissue specimens very often altered in comparison to high quality RNA commonly used by manufacturers for development of library preparation chemistry. In the present study, we used GBM and non-tumor brain tissue specimens and compared three different commercial library preparation kits, namely NEXTflex Rapid Directional qRNA-Seq Kit (Bioo Scientific), SENSE Total RNA-Seq Library Prep Kit (Lexogen) and NEBNext Ultra II Directional RNA Library Prep Kit for Illumina (NEB). Libraries generated using SENSE kit were characterized by the most normal distribution of normalized average GC content, the least amount of over-represented sequences and the percentage of ribosomal RNA reads (0.3–1.5%) and highest numbers of uniquely mapped reads and reads aligning to coding regions. However, NEBNext kit performed better having relatively low duplication rates, even transcript coverage and the highest number of hits in Ensembl database for every biotype of our interest including lncRNAs. Our results indicate that out of three approaches the NEBNext library preparation kit was most suitable for the study of lncRNAs via transcriptome sequencing. This was further confirmed by highly consistent data reached in an independent validation on an expanded cohort.

Long Non-Coding RNAs in Gliomas: From Molecular Pathology to Diagnostic Biomarkers and Therapeutic Targets

Gliomas are the most common malignancies of the central nervous system. Because of tumor localization and the biological behavior of tumor cells, gliomas are characterized by very poor prognosis. Despite significant efforts that have gone into glioma research in recent years, the therapeutic efficacy of available treatment options is still limited, and only a few clinically usable diagnostic biomarkers are available. More and more studies suggest non-coding RNAs to be promising diagnostic biomarkers and therapeutic targets in many cancers, including gliomas. One of the largest groups of these molecules is long non-coding RNAs (lncRNAs). LncRNAs show promising potential because of their unique tissue expression patterns and regulatory functions in cancer cells. Understanding the role of lncRNAs in gliomas may lead to discovery of the novel molecular mechanisms behind glioma biological features. It may also enable development of new solutions to overcome the greatest obstacles in therapy of glioma patients. In this review, we summarize the current knowledge about lncRNAs and their involvement in the molecular pathology of gliomas. A conclusion follows that these RNAs show great potential to serve as powerful diagnostic, prognostic, and predictive biomarkers as well as therapeutic targets.

Long non-coding RNAs in brain tumours: Focus on recent epigenetic findings in glioma

Glioma biology is a major focus in tumour research, primarily due to the aggressiveness and high mortality rate of its most aggressive form, glioblastoma. Progress in understanding the molecular mechanisms behind poor prognosis of glioblastoma, regardless of treatment approaches, has changed the classification of brain tumours after nearly 100 years of relying on anatomopathological criteria. Expanding knowledge in genetic, epigenetic and translational medicine is also beginning to contribute to further elucidating molecular dysregulation in glioma. Long non‐coding RNAs (lncRNAs) and their main representatives, large intergenic non‐coding RNAs (lincRNAs), have recently been under scrutiny in glioma research, revealing novel mechanisms of pathogenesis and reinforcing others. Among those confirmed was the reactivation of events significant for foetal brain development and neuronal commitment. Novel mechanisms of tumour suppression and activation of stem‐like behaviour in tumour cells have also been examined. Interestingly, these processes involve lncRNAs that are present both during normal brain development and in brain malignancies and their reactivation might be explained by epigenetic mechanisms, which we discuss in detail in the present review. In addition, the review discusses the lncRNAs‐induced changes, as well as epigenetic changes that are consequential for tumour formation, affecting, in turn, the expression of various types of lncRNAs.

Long Noncoding RNA HOXA11-AS Functions as miRNA Sponge to Promote the Glioma Tumorigenesis Through Targeting miR-140-5p

Long noncoding RNAs (lncRNAs) have been proved as important regulators in many diseases, including cancers. HOXA11 antisense RNA (HOXA11-AS) is a novel identified lncRNA associated with cancer progression. However, the role of HOXA11-AS in glioma remains poorly understood and needs to be elucidated. The purpose of this study is to investigate the role and regulating mechanism of HOXA11-AS on gliomagenesis. Expression of HOXA11-AS was significantly upregulated in glioma tissue and cell lines compared with the adjacent normal tissue and cells. Moreover, patients with high HOXA11-AS expression had a shorter survival and poorer prognosis than that of lower expression. Loss-of-function experiments revealed that HOXA11-AS knockdown inhibited the proliferation, induced cell cycle arrest at G0/G1 phase, and enhanced the apoptosis. Bioinformatics prediction forecast that miR-140-5p directly targeted HOXA11-AS at 3'-UTR, which was confirmed by luciferase reporter assay. In vitro rescue experiment assays, miR-140-5p inhibitor transfection, could reverse the function of HOXA11-AS knockdown on the proliferation, cell cycle arrest, and apoptosis. Taken together, the present study illustrates that the pathway of HOXA11-AS sponging miR-140-5p might play a vital regulating role in the development and progression of glioma.

Long Noncoding RNAs as Biomarkers in Cancer

Long noncoding RNAs (lncRNAs) are a relatively well-characterized class of noncoding RNA (ncRNA) molecules, involved in the regulation of various cell processes, including transcription, intracellular trafficking, and chromosome remodeling. Their deregulation has been associated with the development and progression of various cancer types, the fact which makes them suitable as biomarkers for cancer diagnosis and prognosis. In recent years, detection of cancer-associated lncRNAs in body fluids of cancer patients has proven itself as an especially valuable method to effectively diagnose cancer. Cancer diagnosis and prognosis employing circulating lncRNAs are preferential when compared to classical biopsies of tumor tissues, especially due to their noninvasiveness, and have great potential for routine usage in clinical practice. Thus, this review focuses on summarizing the perspectives of lncRNAs as biomarkers in cancer, based on evaluating their expression profiles determined in body fluids of cancer patients.

LncRNAs: macromolecules with big roles in neurobiology and neurological diseases

Long noncoding RNAs (lncRNAs) are recently defined as thousands of RNA molecules longer than 200 nucleotides and lacking an appreciable open reading frame in mammals. Although lncRNAs lack protein-coding function, they play critical roles in the regulation of almost all the protein-coding genes in a cell at various stages including chromatin modification, transcription and post-transcriptional processing. It is thus not surprising that lncRNAs may be the crucial regulators in the normal development, physiology and pathology. LncRNAs in neuroscience is a novel research field. Interestingly, recent studies have demonstrated that many lncRNAs are highly expressed in brain and their dysregulations occur in neurological disorders. In this review, we describe the current understanding of lncRNAs in neurobiology and neurological diseases including cerebral injury. LncRNAs could be novel biomarkers and could be potential new targets for new drugs for many neurological diseases in the future, although the related studies are still at in the early stages.