MicroRNA-29a inhibits glioblastoma stem cells and tumor growth by regulating the PDGF pathway

Exosomes: Their role in the diagnosis, progression, metastasis, and treatment of glioblastoma

Exosomes are crucial for the growth and spread of glioblastomas, an aggressive form of brain cancer. These tiny vesicles play a crucial role in the activation of signaling pathways and intercellular communication. They can also transfer a variety of biomolecules such as proteins, lipids and nucleic acids from donor to recipient cells. Exosomes can influence the immune response by regulating the activity of immune cells, and they are crucial for the growth and metastasis of glioblastoma cells. In addition, exosomes contribute to drug resistance during treatment, which is a major obstacle in the treatment of glioblastoma. By studying them, the diagnosis and prognosis of glioblastoma can be improved. Due to their high biocompatibility and lack of toxicity, they have become an attractive option for drug delivery. The development of exosomes as carriers of specific therapeutic agents could overcome some of the obstacles to effective treatment of glioblastoma. In this review, we address the potential of exosomes for the treatment of glioblastoma and show how they can be modified for this purpose.

miR-29a-KLF4 signaling inhibits breast tumor initiation by regulating cancer stem cells

Cancer stem cells (CSCs) are known for their potent ability to drive tumor initiation and recurrence, yet the molecular mechanisms regulating CSCs are still unclear. Our study found a positive correlation between increased levels of miR-29a and better survival rates in early-stage breast cancer patients, but a negative correlation in late-stage patients, suggesting a dual function of miR-29a in regulating breast cancer. Furthermore, miR-29a showed significant downregulation in the ALDH+ breast cancer stem cell population compared to non-stem cancer cells. Overexpression of miR-29a in human breast cancer cells reduced the proportion of CSCs, suppressed their ability to form mammospheres, and inhibited the expression of stemness genes SOX2, KLF4, and hTERT in vitro. Conversely, knockdown of miR-29a in breast cancer cells showed opposite effects. Tumor xenograft experiments revealed that miR-29a overexpression significantly inhibited tumorigenesis initiated by MDA-MB-231 cell transplantation in nude mice. We further demonstrated that Krüppel-like factor 4 (KLF4), a key gene that regulates cell stemness, was a direct target of miR-29a in breast cancer cells. miR-29a suppressed the expression of KLF4 at both mRNA and protein levels. Reintroduction of KLF4 into breast cancer cells rescued the miR-29a-induced CSC suppression phenotype. In summary, our study is the first to demonstrate that miR-29a-KLF4 signaling inhibits breast tumor initiation by regulating CSCs, which provides novel therapeutic targets for preventing breast tumor initiation.

Use of microRNAs as Diagnostic, Prognostic, and Therapeutic Tools for Glioblastoma

Glioblastoma (GB) is the most aggressive and common type of cancer within the central nervous system (CNS). Despite the vast knowledge of its physiopathology and histology, its etiology at the molecular level has not been completely understood. Thus, attaining a cure has not been possible yet and it remains one of the deadliest types of cancer. Usually, GB is diagnosed when some symptoms have already been presented by the patient. This diagnosis is commonly based on a physical exam and imaging studies, such as computed tomography (CT) and magnetic resonance imaging (MRI), together with or followed by a surgical biopsy. As these diagnostic procedures are very invasive and often result only in the confirmation of GB presence, it is necessary to develop less invasive diagnostic and prognostic tools that lead to earlier treatment to increase GB patients' quality of life. Therefore, blood-based biomarkers (BBBs) represent excellent candidates in this context. microRNAs (miRNAs) are small, non-coding RNAs that have been demonstrated to be very stable in almost all body fluids, including saliva, serum, plasma, urine, cerebrospinal fluid (CFS), semen, and breast milk. In addition, serum-circulating and exosome-contained miRNAs have been successfully used to better classify subtypes of cancer at the molecular level and make better choices regarding the best treatment for specific cases. Moreover, as miRNAs regulate multiple target genes and can also act as tumor suppressors and oncogenes, they are involved in the appearance, progression, and even chemoresistance of most tumors. Thus, in this review, we discuss how dysregulated miRNAs in GB can be used as early diagnosis and prognosis biomarkers as well as molecular markers to subclassify GB cases and provide more personalized treatments, which may have a better response against GB. In addition, we discuss the therapeutic potential of miRNAs, the current challenges to their clinical application, and future directions in the field.

HSV1 microRNAs in glioblastoma development: an in silico study

Glioblastoma multiforme (GBM) is a highly aggressive primary brain tumor. Recent findings highlighted the significance of viral microRNAs (miRs) in regulating post-transcriptional mRNA expression in various human conditions. Although HSV1 encodes viral miRs and affects the central nervous system, no study investigated the roles of HSV1-encoding miRs in GBM development. This study applied in silico approaches to investigate whether HSV1-encoding miRs are involved in GBM development and, if so, how they regulate tumor-suppressive/oncogenes expression in GBM. This study leveraged bioinformatics approaches to identify the potential effect of HSV1 miRs in GBM development. The GSE158284, GSE153679, and GSE182109 datasets were analyzed to identify differentially expressed genes in GBM tissues and cell lines using the limma package in the R software. The GSE182109 dataset was analyzed to determine gene expression at the single-cell levels using the Seurat package in the R software. The TCGA-GTEX, GDSC, CTRP, immunogenetic, and enrichment analyses were performed to study the impact of identified viral HSV1 miRs targets in GBM development. hsv1-miR-H6-3p is upregulated in GBM and can be responsible for EPB41L1 and SH3PXD2A downregulation in GBM tissues. Also, hsv1-miR-H1-5p is upregulated in GBM and can decrease the expression of MELK, FZD2, NOVA1, TMEM97, PTPRZ1, and PDGFC in GBM development. The single-cell RNA sequencing analyses have demonstrated that MELK, FZD2, NOVA1, TMEM97, PTPRZ1, and PDGFC are expressed in astrocytes residing in the GBM microenvironment. This study provides novel insights into the potential roles of HSV1 miRs in GBM pathogenesis and offers a reference for further studies on the significance of HSV1 miRs in GBM development.

Identification of Disease-Associated MicroRNAs Via Locality-Constrained Linear Coding-Based Ensemble Learning

Clinical trials indicate that the dysregulation of microRNAs (miRNAs) is closely associated with the development of diseases. Therefore, predicting miRNA-disease associations is significant for studying the pathogenesis of diseases. Since traditional wet-lab methods are resource-intensive, cost-saving computational models can be an effective complementary tool in biological experiments. In this work, a locality-constrained linear coding is proposed to predict associations (ILLCEL). Among them, ILLCEL adopts miRNA sequence similarity, miRNA functional similarity, disease semantic similarity, and interaction profile similarity obtained by locality-constrained linear coding (LLC) as the priori information. Next, features and similarities extracted from multiperspectives are input to the ensemble learning framework to improve the comprehensiveness of the prediction. Significantly, the introduction of hypergraph-regular terms improves the accuracy of prediction by describing complex associations between samples. The results under fivefold cross validation indicate that ILLCEL achieves superior prediction performance. In case studies, known associations are accurately predicted and novel associations are verified in HMDD v3.2, miRCancer, and existing literature. It is concluded that ILLCEL can be served as a powerful tool for inferring potential associations.

miR-3174 Is a New Tumor Suppressor MicroRNA That Inhibits Several Tumor-Promoting Genes in Glioblastoma

microRNAs (miRNAs) play an important role in the pathology of glioblastoma (GBM), which is the most malignant and most common primary malignant brain tumor. miRNAs can target multiple genes simultaneously and are considered as potential therapeutic agents or targets. This study aimed to determine the role of miR-3174 in the pathobiology of GBM using both in vitro and in vivo approaches. This is the first study deciphering the role of miR-3174 in GBM. We studied the expression of miR-3174 and found it to be downregulated in a panel of GBM cell lines, GSCs and tissues relative to astrocytes and normal brain tissue. This finding led us to hypothesize that miR-3174 has a tumor-suppressive role in GBM. Exogenous expression of miR-3174 inhibited GBM cell growth and invasion, and hampered the neurosphere formation ability of GSCs. miR-3174 downregulated the expression of multiple tumor-promoting genes including CD44, MDM2, RHOA, PLAU and CDK6. Further, overexpression of miR-3174 reduced tumor volume in nude mice with intracranial xenografts. Immuno-histochemical study of brain sections with intracranial tumor xenografts revealed the pro-apoptotic and anti-proliferative activity of miR-3174. In conclusion, we demonstrated that miR-3174 has a tumor-suppressive role in GBM and could be exploited for therapeutic purposes.

MiR-29a-3p: a potential biomarker and therapeutic target in colorectal cancer

Cancer is frequently caused by microRNAs, which control post-transcriptional levels of gene expression by binding to target mRNAs. MiR-29a-3p has recently been shown to play a twofold function in the majority of malignancies, including colorectal cancer (CRC), according to mounting evidence. Here, we not only briefly summarize such connection between miR-29a-3p and cancers, but aslo primarily evaluate the miR-29a-3p expression pattern, clinical applicability, and molecular mechanisms in CRC to provide a guide for future studies. This review established the diagnostic and prognostic value of miR-29a-3p abnormalty in a variety of clinical samples for CRC. Furthermore, current molecular mechanisms of miR-29a-3p for regulating cancerous biological processes such growth, invasion, metastasis, the epithelial-mesenchymal transformation process, and immunomodulation through its upstream regulatory factors and downstream targeted genes were briefly explored. More specifically, miR-29a-3p has been linked to a few medications that have been shown to have anticancer benefits. To sum up, miR-29a-3p is a promising biomarker and prospective therapeutic target for the diagnosis and prognosis of CRC, but further research is still needed to establish a theoretical basis for more practical applications.

Signaling pathways governing glioma cancer stem cells behavior

Glioma is the most common malignant brain tumor that develops in the glial tissue. Several studies have identified that glioma cancer stem cells (GCSCs) play important roles in tumor-initiating features in malignant gliomas. GCSCs are a small population in the brain that presents an essential role in the metastasis of glioma cells to other organs. These cells can self-renew and differentiate, which are thought to be involved in the pathogenesis of glioma. Therefore, targeting GCSCs might be a novel strategy for the treatment of glioma. Accumulating evidence revealed that several signaling pathways, including Notch, TGF-β, Wnt, STAT3, AKT, and EGFR mediated GCSC growth, proliferation, migration, and invasion. Besides, non-coding RNAs (ncRNAs), including miRNAs, circular RNAs, and long ncRNAs have been found to play pivotal roles in the regulation of GCSC pathogenesis and drug resistance. Therefore, targeting these pathways could open a new avenue for glioma management. In this review, we summarized critical signaling pathways involved in the stimulation or prevention of GCSCs tumorigenesis and invasiveness.

Non-coding RNAs and glioma: Focus on cancer stem cells

Glioblastoma and gliomas can have a wide range of histopathologic subtypes. These heterogeneous histologic phenotypes originate from tumor cells with the distinct functions of tumorigenesis and self-renewal, called glioma stem cells (GSCs). GSCs are characterized based on multi-layered epigenetic mechanisms, which control the expression of many genes. This epigenetic regulatory mechanism is often based on functional non-coding RNAs (ncRNAs). ncRNAs have become increasingly important in the pathogenesis of human cancer and work as oncogenes or tumor suppressors to regulate carcinogenesis and progression. These RNAs by being involved in chromatin remodeling and modification, transcriptional regulation, and alternative splicing of pre-mRNA, as well as mRNA stability and protein translation, play a key role in tumor development and progression. Numerous studies have been performed to try to understand the dysregulation pattern of these ncRNAs in tumors and cancer stem cells (CSCs), which show robust differentiation and self-regeneration capacity. This review provides recent findings on the role of ncRNAs in glioma development and progression, particularly their effects on CSCs, thus accelerating the clinical implementation of ncRNAs as promising tumor biomarkers and therapeutic targets.

Strategies, considerations, and recent advancements in the development of liquid biopsy for glioblastoma: a step towards individualized medicine in glioblastoma

OBJECTIVE

Glioblastoma (GBM) is a devasting primary brain tumor with less than a 5% 5-year survival. Treatment response assessment can be challenging because of inflammatory pseudoprogression that mimics true tumor progression clinically and on imaging. Developing additional noninvasive assays is critical. In this article, the authors review various biomarkers that could be used in developing liquid biopsies for GBM, along with strengths, limitations, and future applications. In addition, they present a potential liquid biopsy design based on the use of an extracellular vesicle-based liquid biopsy targeting nonneoplastic extracellular vesicles.

METHODS

The authors conducted a current literature review of liquid biopsy in GBM by searching the PubMed, Scopus, and Google Scholar databases. Articles were assessed for type of biomarker, isolation methodology, analytical techniques, and clinical relevance.

RESULTS

Recent work has shown that liquid biopsies of plasma, blood, and/or CSF hold promise as noninvasive clinical tools that can be used to diagnose recurrence, assess treatment response, and predict patient outcomes in GBM. Liquid biopsy in GBM has focused primarily on extracellular vesicles, cell-free tumor nucleic acids, and whole-cell isolates as focal biomarkers. GBM tumor signatures have been generated via analysis of tumor gene mutations, unique RNA expression, and metabolic and proteomic alterations. Liquid biopsies capture tumor heterogeneity, identifying alterations in GBM tumors that may be undetectable via surgical biopsy specimens. Finally, biomarker burden can be used to assess treatment response and recurrence in GBM.

CONCLUSIONS

Liquid biopsy offers a promising avenue for monitoring treatment response and recurrence in GBM without invasive procedures. Although additional steps must be taken to bring liquid biopsy into the clinic, proof-of-principle studies and isolation methodologies are promising. Ultimately, CSF and/or plasma-based liquid biopsy is likely to be a powerful tool in the neurosurgeon's arsenal in the near future for the treatment and management of GBM patients.

Molecular Pathways and Genomic Landscape of Glioblastoma Stem Cells: Opportunities for Targeted Therapy

Glioblastoma (GBM) is an aggressive tumor of the central nervous system categorized by the World Health Organization as a Grade 4 astrocytoma. Despite treatment with surgical resection, adjuvant chemotherapy, and radiation therapy, outcomes remain poor, with a median survival of only 14-16 months. Although tumor regression is often observed initially after treatment, long-term recurrence or progression invariably occurs. Tumor growth, invasion, and recurrence is mediated by a unique population of glioblastoma stem cells (GSCs). Their high mutation rate and dysregulated transcriptional landscape augment their resistance to conventional chemotherapy and radiation therapy, explaining the poor outcomes observed in patients. Consequently, GSCs have emerged as targets of interest in new treatment paradigms. Here, we review the unique properties of GSCs, including their interactions with the hypoxic microenvironment that drives their proliferation. We discuss vital signaling pathways in GSCs that mediate stemness, self-renewal, proliferation, and invasion, including the Notch, epidermal growth factor receptor, phosphatidylinositol 3-kinase/Akt, sonic hedgehog, transforming growth factor beta, Wnt, signal transducer and activator of transcription 3, and inhibitors of differentiation pathways. We also review epigenomic changes in GSCs that influence their transcriptional state, including DNA methylation, histone methylation and acetylation, and miRNA expression. The constituent molecular components of the signaling pathways and epigenomic regulators represent potential sites for targeted therapy, and representative examples of inhibitory molecules and pharmaceuticals are discussed. Continued investigation into the molecular pathways of GSCs and candidate therapeutics is needed to discover new effective treatments for GBM and improve survival.

Insights Into the Role of Platelet-Derived Growth Factors: Implications for Parkinson’s Disease Pathogenesis and Treatment

Parkinson’s disease (PD), the second most common neurodegenerative disease after Alzheimer’s disease, commonly occurs in the elderly population, causing a significant medical and economic burden to the aging society worldwide. At present, there are few effective methods that achieve satisfactory clinical results in the treatment of PD. Platelet-derived growth factors (PDGFs) and platelet-derived growth factor receptors (PDGFRs) are important neurotrophic factors that are expressed in various cell types. Their unique structures allow for specific binding that can effectively regulate vital functions in the nervous system. In this review, we summarized the possible mechanisms by which PDGFs/PDGFRs regulate the occurrence and development of PD by affecting oxidative stress, mitochondrial function, protein folding and aggregation, Ca2+ homeostasis, and cell neuroinflammation. These modes of action mainly depend on the type and distribution of PDGFs in different nerve cells. We also summarized the possible clinical applications and prospects for PDGF in the treatment of PD, especially in genetic treatment. Recent advances have shown that PDGFs have contradictory roles within the central nervous system (CNS). Although they exert neuroprotective effects through multiple pathways, they are also associated with the disruption of the blood–brain barrier (BBB). Our recommendations based on our findings include further investigation of the contradictory neurotrophic and neurotoxic effects of the PDGFs acting on the CNS.

Novel cancer gene discovery using a forward genetic screen in RCAS-PDGFB-driven gliomas

BACKGROUND

Malignant gliomas, the most common malignant brain tumors in adults, represent a heterogeneous group of diseases with poor prognosis. Retroviruses can cause permanent genetic alterations that modify genes close to the viral integration site.

METHODS

Here we describe the use of a high-throughput pipeline coupled to the commonly used tissue-specific retroviral RCAS-TVA mouse tumor model system. Utilizing next-generation sequencing, we show that retroviral integration sites can be reproducibly detected in malignant stem cell lines generated from RCAS-PDGFB-driven glioma biopsies.

RESULTS

A large fraction of common integration sites contained genes that have been dysregulated or misexpressed in glioma. Others overlapped with loci identified in previous glioma-related forward genetic screens, but several novel putative cancer-causing genes were also found. Integrating retroviral tagging and clinical data, Ppfibp1 was highlighted as a frequently tagged novel glioma-causing gene. Retroviral integrations into the locus resulted in Ppfibp1 upregulation, and Ppfibp1-tagged cells generated tumors with shorter latency on orthotopic transplantation. In human gliomas, increased PPFIBP1 expression was significantly linked to poor prognosis and PDGF treatment resistance.

CONCLUSIONS

Altogether, the current study has demonstrated a novel approach to tagging glioma genes via forward genetics, validating previous results, and identifying PPFIBP1 as a putative oncogene in gliomagenesis.

Targeting Acid Ceramidase Inhibits Glioblastoma Cell Migration through Decreased AKT Signaling

Glioblastoma (GBM) remains one of the most aggressive cancers, partially due to its ability to migrate into the surrounding brain. The sphingolipid balance, or the balance between ceramides and sphingosine-1-phosphate, contributes to the ability of GBM cells to migrate or invade. Of the ceramidases which hydrolyze ceramides, acid ceramidase (ASAH1) is highly expressed in GBM samples compared to non-tumor brain. ASAH1 expression also correlates with genes associated with migration and focal adhesion. To understand the role of ASAH1 in GBM migration, we utilized shRNA knockdown and observed decreased migration that did not depend upon changes in growth. Next, we inhibited ASAH1 using carmofur, a clinically utilized small molecule inhibitor. Inhibition of ASAH1 by carmofur blocks in vitro migration of U251 (GBM cell line) and GBM cells derived from patient-derived xenografts (PDXs). RNA-sequencing suggested roles for carmofur in MAPK and AKT signaling. We found that carmofur treatment decreases phosphorylation of AKT, but not of MAPK. The decrease in AKT phosphorylation was confirmed by shRNA knockdown of ASAH1. Our findings substantiate ASAH1 inhibition using carmofur as a potential clinically relevant treatment to advance GBM therapeutics, particularly due to its impact on migration.

MicroRNA 3928 Suppresses Glioblastoma through Downregulation of Several Oncogenes and Upregulation of p53

Glioblastoma (GBM) is the most frequent and lethal primary malignant brain tumor. Despite decades of research, therapeutic advances that significantly prolong life are non-existent. In recent years, microRNAs (miRNAs) have been a focus of study in the pathobiology of cancer because of their ability to simultaneously regulate multiple genes. The aim of this study was to determine the functional and mechanistic effects of miR-3928 in GBM both in vitro and in vivo. To the best of our knowledge, this is the first article investigating the role of miR-3928 in GBM. We measured endogenous miR-3928 expression levels in a panel of patient-derived GBM tissue samples and cell lines. We found that GBM tissue samples and cell lines express lower levels of miR-3928 than normal brain cortex and astrocytes, respectively. Therefore, we hypothesized that miR-3928 is a tumor suppressive microRNA. We verified this hypothesis by showing that exogenous expression of miR-3928 has a strong inhibitory effect on both cell growth and invasiveness of GBM cells. Stable ex vivo overexpression of miR-3928 in GBM cells led to a reduction in tumor size in nude mice xenografts. We identified many targets (MDM2, CD44, DDX3X, HMGA2, CCND1, BRAF, ATOH8, and BMI1) of miR-3928. Interestingly, inhibition of the oncogene MDM2 also led to an upregulation of wild-type p53 expression and phosphorylation. In conclusion, we find that miR-3928, through the downregulation of several oncogenes and upregulation and activation of wild-type p53, is a strong tumor suppressor in GBM. Furthermore, the fact that miR-3928 can target many important dysregulated proteins in GBM suggests it might be a "master" regulatory microRNA that could be therapeutically exploited.

Mesenchymal stem cell (MSC)-derived exosomes as novel vehicles for delivery of miRNAs in cancer therapy

Mesenchymal stem cells (MSCs) are known as promising sources for cancer therapy and can be utilized as vehicles in cancer gene therapy. MSC-derived exosomes are central mediators in the therapeutic functions of MSCs, known as the novel cell-free alternatives to MSC-based cell therapy. MSC-derived exosomes show advantages including higher safety as well as more stability and convenience for storage, transport and administration compared to MSCs transplant therapy. Unmodified MSC-derived exosomes can promote or inhibit tumors while modified MSC-derived exosomes are involved in the suppression of cancer development and progression via the delivery of several therapeutics molecules including chemotherapeutic drugs, miRNAs, anti-miRNAs, specific siRNAs, and suicide gene mRNAs. In most malignancies, dysregulation of miRNAs not only occurs as a consequence of cancer progression but also is directly involved during tumor initiation and development due to their roles as oncogenes (oncomiRs) or tumor suppressors (TS-miRNAs). MiRNA restoration is usually achieved by overexpression of TS-miRNAs using synthetic miRNA mimics and viral vectors or even downregulation of oncomiRs using anti-miRNAs. Similar to other therapeutic molecules, the efficacy of miRNAs restoration in cancer therapy depends on the effectiveness of the delivery system. In the present review, we first provided an overview of the properties and potentials of MSCs in cancer therapy as well as the application of MSC-derived exosomes in cancer therapy. Finally, we specifically focused on harnessing the MSC-derived exosomes for the aim of miRNA delivery in cancer therapy.

Silencing lncRNA LINC01410 suppresses cell viability yet promotes apoptosis and sensitivity to temozolomide in glioblastoma cells by inactivating PTEN/AKT pathway via targeting miR-370-3p

BACKGROUND

Long non-coding RNAs (LncRNAs) are involved in glioblastoma (GBM), but the role of long intergenic non-protein coding RNA 01410 (lncRNA LINC01410) is poorly understood.

METHODS

The expression of LINC01410 in GBM tissues and cells was analyzed. After transfection or temozolomide (TMZ) treatment, the cell viability and apoptosis were detected using cell counting kit-8 assay and flow cytometry. The targeting relationship between LINC01410 and microRNA (miR)-370-3p was confirmed by dual-luciferase reporter assay. Expressions of LINC01410, miR-370-3p and drug resistance- and Phosphatase and Tensin Homolog (PTEN)/AKT pathway-related factors were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

LINC01410 expression was upregulated in GBM, and silencing of LINC01410 decreased cell viability. A slowed decreased trend in cell viability yet an increased half maximal inhibitory concentration (IC50 for TMZ) value and increased expressions of drug resistance-related factors as well as LINC01410 were found in TMZ-resistant GBM cells. Silencing of LINC01410 also decreased the IC50 value yet promoted the sensitivity and apoptosis in TMZ-resistant cells, while upregulating the expression of PTEN and downregulating the phosphorylation of AKT. MiR-370-3p could competitively bind to LINC01410 and its expression was decreased in both parental and TMZ-resistant GBM cells. Downregulation of miR-370-3p reversed the effects of LINC01410 silencing on cell viability, apoptosis and the expressions of miR-370-3p and PTEN/AKT pathway-related factors.

CONCLUSION

Silencing of LINC01410 inhibits cell viability yet enhances apoptosis and sensitivity to TMZ in GBM cells by inactivating PTEN/AKT pathway via targeting miR-370-3p.

Role of microRNAs in glioblastoma

Glioblastoma is the most common and aggressive primary human brain cancer. MicroRNAs (miRNAs) are a set of small endogenous non-coding RNA molecules which play critical roles in different biological processes including cancer. The realization of miRNA regulatory functions in GBM has demonstrated that these molecules play a critical role in its initiation, progression and response to therapy. In this review we discuss the studies related to miRNA discovery and function in glioblastoma. We first summarize the typical miRNAs and their roles in GBM. Then we debate the potential for miRNA-based therapy for glioblastoma, including various delivery strategies. We surmise that future directions identified by these studies will point towards the necessity for therapeutic development and optimization to improve the outcomes for patients with glioblastoma.

Targeting Non-coding RNA for Glioblastoma Therapy: The Challenge of Overcomes the Blood-Brain Barrier

Glioblastoma (GBM) is the most malignant form of all primary brain tumors, and it is responsible for around 200,000 deaths each year worldwide. The standard therapy for GBM treatment includes surgical resection followed by temozolomide-based chemotherapy and/or radiotherapy. With this treatment, the median survival rate of GBM patients is only 15 months after its initial diagnosis. Therefore, novel and better treatment modalities for GBM treatment are urgently needed. Mounting evidence indicates that non-coding RNAs (ncRNAs) have critical roles as regulators of gene expression. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are among the most studied ncRNAs in health and disease. Dysregulation of ncRNAs is observed in virtually all tumor types, including GBMs. Several dysregulated miRNAs and lncRNAs have been identified in GBM cell lines and GBM tumor samples. Some of them have been proposed as diagnostic and prognostic markers, and as targets for GBM treatment. Most ncRNA-based therapies use oligonucleotide RNA molecules which are normally of short life in circulation. Nanoparticles (NPs) have been designed to increase the half-life of oligonucleotide RNAs. An additional challenge faced not only by RNA oligonucleotides but for therapies designed for brain-related conditions, is the presence of the blood-brain barrier (BBB). The BBB is the anatomical barrier that protects the brain from undesirable agents. Although some NPs have been derivatized at their surface to cross the BBB, optimal NPs to deliver oligonucleotide RNA into GBM cells in the brain are currently unavailable. In this review, we describe first the current treatments for GBM therapy. Next, we discuss the most relevant miRNAs and lncRNAs suggested as targets for GBM therapy. Then, we compare the current drug delivery systems (nanocarriers/NPs) for RNA oligonucleotide delivery, the challenges faced to send drugs through the BBB, and the strategies to overcome this barrier. Finally, we categorize the critical points where research should be the focus in order to design optimal NPs for drug delivery into the brain; and thus move the Oligonucleotide RNA-based therapies from the bench to the clinical setting.

miR-29a sensitizes the response of glioma cells to temozolomide by modulating the P53/MDM2 feedback loop

Recently, pivotal functions of miRNAs in regulating common tumorigenic processes and manipulating signaling pathways in brain tumors have been recognized; notably, miR‐29a is closely associated with p53 signaling, contributing to the development of glioma. However, the molecular mechanism of the interaction between miR-29a and p53 signaling is still to be revealed. Herein, a total of 30 glioma tissues and 10 non-cancerous tissues were used to investigate the expression of miR‐29a. CCK-8 assay and Transwell assay were applied to identify the effects of miR-29a altered expression on the malignant biological behaviors of glioma cells in vitro, including proliferation, apoptosis, migration and invasion. A dual-luciferase reporter assay was used to further validate the regulatory effect of p53 or miR-29a on miR-29a or MDM2, respectively, at the transcriptional level. The results showed that miR-29a expression negatively correlated with tumor grade of human gliomas; at the same time it inhibited cell proliferation, migration, and invasion and promoted apoptosis of glioma cells in vitro. Mechanistically, miR-29a expression was induced by p53, leading to aberrant expression of MDM2 targeted by miR-29a, and finally imbalanced the activity of the p53-miR-29a-MDM2 feedback loop. Moreover, miR-29a regulating p53/MDM2 signaling sensitized the response of glioma cells to temozolomide treatment. Altogether, the study demonstrated a potential molecular mechanism in the tumorigenesis of glioma, while offering a possible target for treating human glioma in the future.

The Acidic Brain-Glycolytic Switch in the Microenvironment of Malignant Glioma

Malignant glioma represents a fatal disease with a poor prognosis and development of resistance mechanisms against conventional therapeutic approaches. The distinct tumor zones of this heterogeneous neoplasm develop their own microenvironment, in which subpopulations of cancer cells communicate. Adaptation to hypoxia in the center of the expanding tumor mass leads to the glycolytic and angiogenic switch, accompanied by upregulation of different glycolytic enzymes, transporters, and other metabolites. These processes render the tumor microenvironment more acidic, remodel the extracellular matrix, and create energy gradients for the metabolic communication between different cancer cells in distinct tumor zones. Escape mechanisms from hypoxia-induced cell death and energy deprivation are the result. The functional consequences are more aggressive and malignant behavior with enhanced proliferation and survival, migration and invasiveness, and the induction of angiogenesis. In this review, we go from the biochemical principles of aerobic and anaerobic glycolysis over the glycolytic switch, regulated by the key transcription factor hypoxia-inducible factor (HIF)-1α, to other important metabolic players like the monocarboxylate transporters (MCTs)1 and 4. We discuss the metabolic symbiosis model via lactate shuttling in the acidic tumor microenvironment and highlight the functional consequences of the glycolytic switch on glioma malignancy. Furthermore, we illustrate regulation by micro ribonucleic acids (miRNAs) and the connection between isocitrate dehydrogenase (IDH) mutation status and glycolytic metabolism. Finally, we give an outlook about the diagnostic and therapeutic implications of the glycolytic switch and the relation to tumor immunity in malignant glioma.

Promotive effects of HOXA10 antisense RNA on the stemness of oral squamous cell carcinoma stem cells through a microRNA-29a/MCL-1/phosphatidyl inositol 3-kinase/protein kinase B axis

OBJECTIVE

The aim of this study was to investigate the effects of long non-coding RNA (lncRNA) HOXA10 antisense RNA (HOXA10-AS) on the properties of oral squamous cell carcinoma (OSCC) stem cells and the molecular mechanism.

DESIGN

Tumor and the paracancerous tissues were collected from 83 patients with OSCC. OSCC stem cells were extracted from a human OSCC cell line Tca8113. Silencing of HOXA10-AS was introduced in stem cells and then the malignant behaviors of cells were determined. The target transcripts of HOXA10-AS were predicted using integrated bioinformatics analyses. The interactions among HOXA10-AS, microRNA (miR)-29a and MCL-1 were validated, and their functions in stem cell behaviors in vivo and in vitro were explored.

RESULTS

HOXA10-AS and MCL-1 were highly expressed while miR-29a was poorly expressed in the collected tumor tissues and the extracted OSCC stem cells. High expression of HOXA10-AS and MCL-1, while poor expression of miR-29a was relevant to poor prognosis in patients. Silencing of HOXA10-AS suppressed proliferation and tumor sphere formation ability of stem cells, and it reduced growth and metastasis of tumors in animals. HOXA10-AS served as a sponge for miR-29a and upregulated MCL-1 mRNA expression. Inhibition of miR-29a promoted, while silencing of MCL-1 suppressed the malignant behaviors of OSCC stem cells. In addition, HOXA-10-AS and MCL-1 were found to activate the phosphatidyl inositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway.

CONCLUSION

This study evidenced that HOXA10-AS enhances the stem cell property of OSCC stem cells through the miR-29a/MCL-1/PI3K/AKT axis.

LINC00460 facilitated tongue squamous cell carcinoma progression via the miR-320b/IGF2BP3 axis

OBJECTIVE

We aimed to explore the role of long intergenic non-protein coding RNA 460 (LINC00460) in tongue squamous cell carcinoma (TSCC).

METHODS

We enrolled 27 TSCC patients to explore LINC00460 expression in clinical TSCC samples. RT-qPCR measured expression of molecules in this research. Loss-of-function assays explored biological function of LINC00460 in TSCC cells. RNA pull-down assay, luciferase reporter assay, and RIP assay investigated mechanism of LINC00460 underlying TSCC cells.

RESULTS

TSCC tissues and cell lines both showed high expression of LINC00460. Functionally, LINC00460 downregulation inhibited TSCC cell growth and promoted TSCC cell apoptosis. Additionally, LINC00460 silencing suppressed tumor growth in vivo. Mechanistically, LINC00460 bound with microRNA 320b (miR-320b) in TSCC cells. MiR-320b overexpression suppressed TSCC cell growth and promoted TSCC cell apoptosis. Moreover miR-320b targeted insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) 3'untranslated region in TSCC cells. Furthermore, IGF2BP3 silencing suppressed TSCC cell growth and promoted TSCC cell apoptosis. IGF2BP3 upregulation countervailed effects of silenced LINC00460 on TSCC cells. The LINC00460/miR-320b/IGF2BP3 axis was associated with lymph node metastasis of TSCC patients.

CONCLUSION

Our research illustrated that LINC00460 facilitated TSCC progression via the miR-320b/IGF2BP3 axis, highlighting a potential insight for the treatment of TSCC.

MicroRNA-29a inhibits cell proliferation and arrests cell cycle by modulating p16 methylation in cervical cancer

Cervical cancer is the second most common gynecological malignancy. Accumulating evidence has suggested that microRNAs (miRNAs) are involved in the occurrence and development of cervical cancer. The present study aimed to investigate the function and underlying molecular mechanism of microRNA (miRNA/miR)-29a in cervical cancer. Reverse transcription-quantitative PCR and methylation-specific PCR were used to examine the expression of miR-29a and methylated status of p16 promoter, respectively. Cell Counting Kit-8 analysis and flow cytometry were performed to evaluate cell viability and cycle, respectively. Dual-luciferase reporter assay was performed to verify the interaction between miR-29a and its targets. Western blot analysis was performed to detect the protein levels of DNA methyltransferases (DNMT)3A and DNMT3B. The results demonstrated that miR-29a expression was downregulated in cervical cancer tissues and cells, and negatively correlated with p16 promoter hypermethylation. Furthermore, cell experiments confirmed that miR-29a suppressed cell proliferation and induced cell cycle arrest in HeLa and C-33A cells. Mechanically, miR-29a restored normal methylation pattern of the p16 gene by sponging DNMT3A and DNMT3B. Taken together, the results of the present study demonstrated the epigenetic regulation of tumor suppressor p16 by miR-29a as a unique mechanism, thus providing a rationale for the development of miRNA-based strategies in the treatment of cervical cancer.

Regulators at Every Step-How microRNAs Drive Tumor Cell Invasiveness and Metastasis

Simple Summary

Tumor cell invasiveness and metastasis are key processes in cancer progression and are composed of many steps. All of them are regulated by multiple microRNAs that either promote or suppress tumor progression. Multiple studies demonstrated that microRNAs target the mRNAs of multiple genes involved in the regulation of cell motility, local invasion, and metastatic niche formation. Thus, microRNAs are promising biomarkers and therapeutic targets in oncology.

Abstract

Tumor cell invasiveness and metastasis are the main causes of mortality in cancer. Tumor progression is composed of many steps, including primary tumor growth, local invasion, intravasation, survival in the circulation, pre-metastatic niche formation, and metastasis. All these steps are strictly controlled by microRNAs (miRNAs), small non-coding RNA that regulate gene expression at the post-transcriptional level. miRNAs can act as oncomiRs that promote tumor cell invasion and metastasis or as tumor suppressor miRNAs that inhibit tumor progression. These miRNAs regulate the actin cytoskeleton, the expression of extracellular matrix (ECM) receptors including integrins and ECM-remodeling enzymes comprising matrix metalloproteinases (MMPs), and regulate epithelial–mesenchymal transition (EMT), hence modulating cell migration and invasiveness. Moreover, miRNAs regulate angiogenesis, the formation of a pre-metastatic niche, and metastasis. Thus, miRNAs are biomarkers of metastases as well as promising targets of therapy. In this review, we comprehensively describe the role of various miRNAs in tumor cell migration, invasion, and metastasis.

Regulators at Every Step—How microRNAs Drive Tumor Cell Invasiveness and Metastasis

Tumor cell invasiveness and metastasis are the main causes of mortality in cancer. Tumor progression is composed of many steps, including primary tumor growth, local invasion, intravasation, survival in the circulation, pre-metastatic niche formation, and metastasis. All these steps are strictly controlled by microRNAs (miRNAs), small non-coding RNA that regulate gene expression at the post-transcriptional level. miRNAs can act as oncomiRs that promote tumor cell invasion and metastasis or as tumor suppressor miRNAs that inhibit tumor progression. These miRNAs regulate the actin cytoskeleton, the expression of extracellular matrix (ECM) receptors including integrins and ECM-remodeling enzymes comprising matrix metalloproteinases (MMPs), and regulate epithelial–mesenchymal transition (EMT), hence modulating cell migration and invasiveness. Moreover, miRNAs regulate angiogenesis, the formation of a pre-metastatic niche, and metastasis. Thus, miRNAs are biomarkers of metastases as well as promising targets of therapy. In this review, we comprehensively describe the role of various miRNAs in tumor cell migration, invasion, and metastasis.

LncRNA TUG1 Promotes Growth and Metastasis of Cholangiocarcinoma Cells by Inhibiting miR-29a

Background

As a highly malignant tumor, cholangiocarcinoma poses a serious threat to human life and health, so exploring the mechanisms of its development and progression at a molecular level is of great significance to the diagnosis and treatment of the disease.

Objective

This study was aimed at investigating the effects and related mechanisms of LncRNA TUG1 on cholangiocarcinoma cells.

Methods

Cholangiocarcinoma tissues and adjacent tissues (n=82 each), human cholangiocarcinoma cell lines (RBE, QBC939, HuH28), and a human normal biliary epithelial cell line (HIBE) were collected. miR-29a-mimics, miR-29a-inhibitor, miR-NC, si-TUG1, pcDNA3.1 TUG1, and NC were transfected into the cholangiocarcinoma cells. qRT-PCR was performed to detect TUG1 and miR-29a expression in the cholangiocarcinoma tissues and cells. Western blotting (WB) was conducted to detect the expression of Bax, Caspase-3, and Bcl-2 in the cells. CCK-8 assay, Transwell, and flow cytometry were carried out to detect cell proliferation, invasion, and apoptosis. Dual luciferase reporter gene assay (DLRGA) was performed to confirm the correlation of TUG1 with miR-29a.

Results

TUG1 was highly expressed while miR-29a was poorly expressed in cholangiocarcinoma cells. TUG1 expression was negatively correlated with miR-29a expression, and TUG1 had a relatively high diagnostic value for cholangiocarcinoma. Cell experiments showed that inhibiting TUG1 expression or up-regulating miR-29a expression could inhibit cholangiocarcinoma cells from proliferation and invasion, and promote their apoptosis, while up-regulating TUG1 or inhibiting miR-29a could promote the proliferation and invasion but inhibit the apoptosis. Rescue experiment showed that overexpressing miR-29a could reverse the effects of high TUG1 expression on cholangiocarcinoma cells. DLRGA confirmed that there was a regulatory relationship between TUG1 and miR-29a.

Conclusion

TUG1 is highly expressed in cholangiocarcinoma tissues. It can promote the growth and metastasis of cholangiocarcinoma cells by inhibiting miR-29a, so it may be a new target for diagnosing and treating cholangiocarcinoma.

Overexpression of microRNA-129-5p in glioblastoma inhibits cell proliferation, migration, and colony-forming ability by targeting ZFP36L1

Glioblastoma multiforme (GBM) is a highly invasive cancer with a high recurrence rate. The prognosis of GBM patients remains poor, even after standard surgical resection combined with chemoradiotherapy. Thus, there is an urgent need for new therapeutic targets in GBM. In recent years, microRNAs have received considerable attention due to their important role in tumor development and progression. In this study, we investigated the role of miR-129-5p and miR-129-5p/ZFP36L1 axis in GBM tumorigenesis. Analysis of GSE103228 microarray data from the GEO database showed that miR-129-5p was significantly downregulated in GBM vs. normal brain tissues. Quantitative reverse transcription PCR analysis of miR-129-5p expression in seven GBM cell lines (LN229, A172, U87, T98G, U251, H4, and LN118) vs. normal human astrocytes (NHA) showed miR-129-5p was significantly downregulated in GBM cells. Overexpression of miR-129-5p in LN229 and A172 cells significantly suppressed cell proliferation, migration, invasion, and colony-forming ability. Target Scan analysis identified ZFP36L1 as the target of miR-129-5p. UALCAN dataset analysis found that ZFP36L1 was significantly upregulated in GBM vs. normal brain tissues, and high ZFP36L1 expression was positively associated with poor survival of GBM patients. Western blot analysis demonstrated that ZFP36L1 was significantly upregulated in seven GBM cell lines vs. NHA. Overexpression of miR-129-5p in LN229 and A172 cells significantly inhibited ZFP36L1 mRNA and protein expression, while overexpression of ZFP36L1 in LN229 and A172 cells reversed miR-129-5p-mediated inhibition on GBM tumorigenesis. Our results revealed an important role of miR-129-5p in the negative regulation of ZFP36L1 expression in GBM, suggesting new candidates for targeted therapy in GBM patients.

MiRNA-146a rs2910164 Confers a Susceptibility to Digestive System Cancer: A Meta-Analysis Involving 59,098 Subjects

BACKGROUND

MicroRNA (miR)-146a might participate in the occurrence of malignant tumor. The aim of the current investigation was to evaluate the relationship of microRNA-146a (miR-146a) rs2910164 C > G locus to the development of digestive system cancer (DSC).

METHODS

We retrieved publications from PubMed, China Biology Medicine and EMBASE databases up to August 29, 2019. Finally, 56 independent case-control studies with 59,098 participants were included. The strength of the relationship between rs2910164 locus and a risk of DSC was assessed. The power value was also calculated in this study.

RESULTS

We identified a correlation of rs2910164 locus in miR-146a with DSC development in dominant model (P = .035; power value = 0.994). MiR-146a rs2910164 locus was also identified to be correlated with a risk of DSC in Asians (GG/CG vs. CC: P = .033; power value = 0.989). Sensitivity analysis revealed that any individual study could not alter the final decision. In our study, no significant bias was found among these included studies (P > .1). The results of heterogeneity analysis suggested that small sample size (<1000 subjects), colorectal carcinoma, Asians, gastric carcinoma, esophageal squamous cell carcinoma, hepatocellular cancer, hospital-based study and high-quality score (≥7.0) subgroups contributed the heterogeneity to our findings. Galbraith radial plot determined that eleven outliers contributed to the main heterogeneity.

CONCLUSION

In summary, this meta-analysis highlights that rs2910164 locus might be implicated in the risk of DSC. More studies are, therefore, needed to confirm our results.

Recent Trends of microRNA Significance in Pediatric Population Glioblastoma and Current Knowledge of Micro RNA Function in Glioblastoma Multiforme

Central nervous system tumors are a significant problem for modern medicine because of their location. The explanation of the importance of microRNA (miRNA) in the development of cancerous changes plays an important role in this respect. The first papers describing the presence of miRNA were published in the 1990s. The role of miRNA has been pointed out in many medical conditions such as kidney disease, diabetes, neurodegenerative disorder, arthritis and cancer. There are several miRNAs responsible for invasiveness, apoptosis, resistance to treatment, angiogenesis, proliferation and immunology, and many others. The research conducted in recent years analyzing this group of tumors has shown the important role of miRNA in the course of gliomagenesis. These particles seem to participate in many stages of the development of cancer processes, such as proliferation, angiogenesis, regulation of apoptosis or cell resistance to cytostatics.

The Role of Circulating MicroRNA in Glioblastoma Liquid Biopsy

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