The miRNA Content of Exosomes Released from the Glioma Microenvironment Can Affect Malignant Progression

Exploring the clinical implications and applications of exosomal miRNAs in gliomas: a comprehensive study

Gliomas are aggressive brain tumors associated with poor prognosis and limited treatment options due to their invasive nature and resistance to current therapeutic modalities. Research suggests that exosomal microRNAs have emerged as key players in intercellular communication within the tumor microenvironment, influencing tumor progression and therapeutic responses. Exosomal microRNAs (miRNAs), small non-coding RNAs, are crucial in glioma development, invasion, metastasis, angiogenesis, and immune evasion by binding to target genes. This comprehensive review examines the clinical relevance and implications of exosomal miRNAs in gliomas, highlighting their potential as diagnostic biomarkers, therapeutic targets and prognosis biomarker. Additionally, we also discuss the limitations of current exsomal miRNA treatments and address challenges and propose future directions for leveraging exosomal miRNAs in precision oncology for glioma management.

Exosomal TNF-α mediates voltage-gated Na+ channel 1.6 overexpression and contributes to brain tumor-induced neuronal hyperexcitability

Patients affected by glioma frequently experience epileptic discharges; however, the causes of brain tumor-related epilepsy (BTRE) are still not completely understood. We investigated the mechanisms underlying BTRE by analyzing the effects of exosomes released by U87 glioma cells and by patient-derived glioma cells. Rat hippocampal neurons incubated for 24 hours with these exosomes exhibited increased spontaneous firing, while their resting membrane potential shifted positively by 10-15 mV. Voltage clamp recordings demonstrated that the activation of the Na+ current shifted toward more hyperpolarized voltages by 10-15 mV. To understand the factors inducing hyperexcitability, we focused on exosomal cytokines. Western blot and ELISAs showed that TNF-α was present inside glioma-derived exosomes. Remarkably, incubation with TNF-α fully mimicked the phenotype induced by exosomes, with neurons firing continuously, while their resting membrane potential shifted positively. Real-time PCR revealed that both exosomes and TNF-α induced overexpression of the voltage-gated Na+ channel Nav1.6, a low-threshold Na+ channel responsible for hyperexcitability. When neurons were preincubated with infliximab, a specific TNF-α inhibitor, the hyperexcitability induced by exosomes and TNF-α was drastically reduced. We propose that infliximab, an FDA-approved drug to treat rheumatoid arthritis, could ameliorate the conditions of glioma patients with BTRE.

The tumor-associated fibrotic reactions in microenvironment aggravate glioma chemoresistance

Malignant gliomas are one of the most common and lethal brain tumors with poor prognosis. Most patients with glioblastoma (GBM) die within 2 years of diagnosis, even after receiving standard treatments including surgery combined with concomitant radiotherapy and chemotherapy. Temozolomide (TMZ) is the first-line chemotherapeutic agent for gliomas, but the frequent acquisition of chemoresistance generally leads to its treatment failure. Thus, it's urgent to investigate the strategies for overcoming glioma chemoresistance. Currently, many studies have elucidated that cancer chemoresistance is not only associated with the high expression of drug-resistance genes in glioma cells but also can be induced by the alterations of the tumor microenvironment (TME). Numerous studies have explored the use of antifibrosis drugs to sensitize chemotherapy in solid tumors, and surprisingly, these preclinical and clinical attempts have exhibited promising efficacy in treating certain types of cancer. However, it remains unclear how tumor-associated fibrotic alterations in the glioma microenvironment (GME) mediate chemoresistance. Furthermore, the possible mechanisms behind this phenomenon are yet to be determined. In this review, we have summarized the molecular mechanisms by which tumor-associated fibrotic reactions drive glioma transformation from a chemosensitive to a chemoresistant state. Additionally, we have outlined antitumor drugs with antifibrosis functions, suggesting that antifibrosis strategies may be effective in overcoming glioma chemoresistance through TME normalization.

Extracellular vesicles in glioblastoma: a challenge and an opportunity

Glioblastoma is a highly heterogeneous tumor whose pathophysiological complexities dictate both the diagnosis of disease severity as well as response to therapy. Conventional diagnostic tools and standard treatment regimens have only managed to achieve limited success in the management of patients suspected of glioblastoma. Extracellular vesicles are an emerging liquid biopsy tool that has shown great promise in resolving the limitations presented by the heterogeneous nature of glioblastoma. Here we discuss the contrasting yet interdependent dual role of extracellular vesicles as communication agents that contribute to the progression of glioblastoma by creating a heterogeneous microenvironment and as a liquid biopsy tool providing an opportunity to accurately identify the disease severity and progression.

Extracellular vesicles secreted by 3D tumor organoids are enriched for immune regulatory signaling biomolecules compared to conventional 2D glioblastoma cell systems

Background

Newer 3D culturing approaches are a promising way to better mimic the in vivo tumor microenvironment and to study the interactions between the heterogeneous cell populations of glioblastoma multiforme. Like many other tumors, glioblastoma uses extracellular vesicles as an intercellular communication system to prepare surrounding tissue for invasive tumor growth. However, little is known about the effects of 3D culture on extracellular vesicles. The aim of this study was to comprehensively characterize extracellular vesicles in 3D organoid models and compare them to conventional 2D cell culture systems.

Methods

Primary glioblastoma cells were cultured as 2D and 3D organoid models. Extracellular vesicles were obtained by precipitation and immunoaffinity, with the latter allowing targeted isolation of the CD9/CD63/CD81 vesicle subpopulation. Comprehensive vesicle characterization was performed and miRNA expression profiles were generated by smallRNA-sequencing. In silico analysis of differentially regulated miRNAs was performed to identify mRNA targets and corresponding signaling pathways. The tumor cell media and extracellular vesicle proteome were analyzed by high-resolution mass spectrometry.

Results

We observed an increased concentration of extracellular vesicles in 3D organoid cultures. Differential gene expression analysis further revealed the regulation of twelve miRNAs in 3D tumor organoid cultures (with nine miRNAs down and three miRNAs upregulated). MiR-23a-3p, known to be involved in glioblastoma invasion, was significantly increased in 3D. MiR-7-5p, which counteracts glioblastoma malignancy, was significantly decreased. Moreover, we identified four miRNAs (miR-323a-3p, miR-382-5p, miR-370-3p, miR-134-5p) located within the DLK1-DIO3 domain, a cancer-associated genomic region, suggesting a possible importance of this region in glioblastoma progression. Overrepresentation analysis identified alterations of extracellular vesicle cargo in 3D organoids, including representation of several miRNA targets and proteins primarily implicated in the immune response.

Conclusion

Our results show that 3D glioblastoma organoid models secrete extracellular vesicles with an altered cargo compared to corresponding conventional 2D cultures. Extracellular vesicles from 3D cultures were found to contain signaling molecules associated with the immune regulatory signaling pathways and as such could potentially change the surrounding microenvironment towards tumor progression and immunosuppressive conditions. These findings suggest the use of 3D glioblastoma models for further clinical biomarker studies as well as investigation of new therapeutic options.

FCGR2B as a prognostic and immune microenvironmental marker for gliomas based on transcriptomic analysis

To explore the expression and prognosis of Fc fragment of IgG low affinity IIb receptor (FCGR2B) in glioma and its relationship with immune microenvironment, so as to provide potential molecular targets for the treatment of glioma. We analyzed the gene expression of FCGR2B using the Cancer Genome Atlas database, Chinese Glioma Genome Atlas, Gene Expression Omnibus database and other glioma related databases. Moreover, we generated survival receiver operating characteristic curve, carried out univariate and multivariate Cox analysis and nomograph construction, and analyzed the relationship between FCGR2B and prognosis. According to the median of FCGR2B gene expression value, the differential expression analysis was carried out by high and low grouping method, and the gene ontology, Kyoto encyclopedia of genes and genomes, and gene set enrichment analysis enrichment analysis were carried out to explore the possible mechanism. Then, the correlation between immune score of glioma and prognosis, World Health Organization grade and FCGR2B expression was analyzed. Finally, the correlation between FCGR2B expression and the proportion of tumor infiltrating immune cells, immune checkpoints, tumor mutation load and immune function was analyzed. The expression of FCGR2B in gliomas was higher than that in normal tissues and was associated with poor prognosis. Independent prognostic analysis showed that FCGR2B was an independent prognostic factor for glioma. The analysis of gene ontology and gene set enrichment analysis showed that FCGR2B was closely related to immune-related functions. The analysis of immune scores and prognosis, World Health Organization grade and FCGR2B expression in gliomas indicated that patients with high immune scores had significantly poorer overall survival and higher tumor pathological grade. In addition, immune scores were significantly positively correlated with the expression of FCGR2B. The analysis of tumor infiltrating immune cells suggested that the expression level of FCGR2B affected the immune activity of TME. In addition, the expression of FCGR2B was positively correlated with almost all immune checkpoint molecules including CD28, CD44, TNFSF14, PDCD1LG2, LAIR1, and CD48 and was significantly positively correlated with tumor mutation load. All immunobiological functions of the high expression group of FCGR2B were significantly inhibited. FCGR2B may play an important role in the occurrence, development and invasion of tumor by influencing the tumor microenvironment of immunosuppression. FCGR2B may be an important target for the treatment of glioma.

LIN28B and Let-7 in Diffuse Midline Glioma: A Review

Diffuse midline glioma (DMG) is the most lethal of all childhood cancers. DMGs are driven by histone-tail-mutation-mediated epigenetic dysregulation and partner mutations in genes controlling proliferation and migration. One result of this epigenetic and genetic landscape is the overexpression of LIN28B RNA binding protein. In other systems, LIN28B has been shown to prevent let-7 microRNA biogenesis; however, let-7, when available, faithfully suppresses tumorigenic pathways and induces cellular maturation by preventing the translation of numerous oncogenes. Here, we review the current literature on LIN28A/B and the let-7 family and describe their role in gliomagenesis. Future research is then recommended, with a focus on the mechanisms of LIN28B overexpression and localization in DMG.

Tumor Microenvironment and Glioblastoma Cell Interplay as Promoters of Therapeutic Resistance

The invasive nature of glioblastoma is problematic in a radical surgery approach and can be responsible for tumor recurrence. In order to create new therapeutic strategies, it is imperative to have a better understanding of the mechanisms behind tumor growth and invasion. The continuous cross-talk between glioma stem cells (GSCs) and the tumor microenvironment (TME) contributes to disease progression, which renders research in this field difficult and challenging. The main aim of the review was to assess the different possible mechanisms that could explain resistance to treatment promoted by TME and GSCs in glioblastoma, including the role of M2 macrophages, micro RNAs (miRNAs), and long non-coding RNAs (lncRNAs) from exosomes from the TME. A systematic review of the literature on the role of the TME in developing and promoting radioresistance and chemoresistance of GBM was performed according to PRISMA-P (Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols) guidelines. A dedicated literature review search was also performed on the immunotherapeutic agents against the immune TME. We identified 367 papers using the reported keywords. The final qualitative analysis was conducted on 25 studies. A growing amount of evidence in the current literature supports the role of M2 macrophages and non-coding RNAs in promoting the mechanisms of chemo and radioresistance. A better insight into how GBM cells interact with TME is an essential step towards comprehending the mechanisms that give rise to resistance to standard treatment, which can help to pave the way for the development of novel therapeutic strategies for GBM patients.

Modification of Extracellular Vesicle Surfaces: An Approach for Targeted Drug Delivery

Extracellular vesicles (EVs) are a promising drug delivery vehicle candidate because of their natural origin and intrinsic function of transporting various molecules between different cells. Several advantages of the EV delivery platform include enhanced permeability and retention effect, efficient interaction with recipient cells, the ability to traverse biological barriers, high biocompatibility, high biodegradability, and low immunogenicity. Furthermore, EV membranes share approximately similar structures and contents to the cell membrane, which allows surface modification of EVs, an approach to enable specific targeting. Enhanced drug accumulation in intended sites and reduced adverse effects of chemotherapeutic drugs are the most prominent effects of targeted drug delivery. In order to improve the targeting ability of EVs, chemical modification and genetic engineering are the most adopted methods to date. Diverse chemical methods are employed to decorate EV surfaces with various ligands such as aptamers, carbohydrates, peptides, vitamins, and antibodies. In this review, we introduce the biogenesis, content, and cellular pathway of natural EVs and further discuss the genetic modification of EVs, and its challenges. Furthermore, we provide a comprehensive deliberation on the various chemical modification methods for improved drug delivery, which are directly related to increasing the therapeutic index.

Identification of a Prognostic Microenvironment-Related Gene Signature in Glioblastoma Patients Treated with Carmustine Wafers

Despite the state-of-the-art treatment, patients diagnosed with glioblastoma (GBM) have a median overall survival (OS) of 14 months. The insertion of carmustine wafers (CWs) into the resection cavity as adjuvant treatment represents a promising option, although its use has been limited due to contrasting clinical results. Our retrospective evaluation of CW efficacy showed a significant improvement in terms of OS in a subgroup of patients. Given the crucial role of the tumor microenvironment (TME) in GBM progression and response to therapy, we hypothesized that the TME of patients who benefited from CW could have different properties compared to that of patients who did not show any advantage. Using an in vitro model of the glioma microenvironment, represented by glioma-associated-stem cells (GASC), we performed a transcriptomic analysis of GASC isolated from tumors of patients responsive and not responsive to CW to identify differentially expressed genes. We found different transcriptomic profiles, and we identified four genes, specifically down-regulated in GASC isolated from long-term survivors, correlated with clinical data deposited in the TCGA–GBM dataset. Our results highlight that studying the in vitro properties of patient-specific glioma microenvironments can help to identify molecular determinants potentially prognostic for patients treated with CW.

Astragalus Polysaccharides Affect Glioblastoma Cells Through Targeting miR-34a-5p

This study discussed Astragalus Polysaccharides (APS)’s effect on the cytobiology of glioma. U87 glioma cells were assigned into control group (U87 cells), miR-34a-5p mimic group (transfected with miR-34a-5p mimic), and APS group (treated with 10 μM APS) followed by analysis of miR-34a-5p level, cell proliferation and invasion, Caspase3 and SOD activity as well as E-cadherin, Vimentin and survivn expression. APS treatment significantly upregulated miR-34a-5p expression, inhibits cell proliferation and invasion, and promoted cell apoptosis. In addition, APS also significantly upregulated E-cadherin, downregulated Vimentin and survivn level in glioma cells as well as inhibited ROS generation and increased SOD activity. In conclusion, the level of miR-34a-5a in glioma cells is up-regulated by APS so as to restrain the biological behaviors of glioma cells, indicating that it might be used as novel agent for the treatment of glioma.

Construction of a novel microRNA-based signature for predicting the prognosis of glioma

Background and purpose: Glioma is a frequent primary brain tumor. MicroRNAs (miRNA) have been shown to potentially play a crucial part in tumor development. Based on miRNAs and clinical factors, a model was constructed to predict the glioma prognosis. Methods: The miRNA expression profiles of glioma come from The Cancer Genome Atlas (TCGA, training group) and Chinese Glioma Genome Atlas (CGGA, validation group). Regression analyses of Cox and Lasso were applied to identity miRNAs associated with glioma prognosis in the TCGA database. The miRNAs were combined with clinical factors to construct individualized prognostic prediction models, whose performance was validated in the CGGA database. The role of miRNA in glioma development was investigated by in vitro experiments.Results: We identified five key miRNAs associated with glioma prognosis and constructed a prediction model. The area under ROC curve for predicting 3-year survival of glioma patients in the TCGA and CGGA groups was 0.844 and 0.770, respectively. The nomogram constructed using the miRNA risk scores and clinical factors showed high accuracy of prediction in the TCGA group (C-index of 0.820) and the CGGA group (C-index of 0.722). The miR-196b-5p altered the migration, proliferation, invasion, and apoptosis of glioma cells by regulating target genes, according to in vitro experiments.Conclusions: A miRNA-based individualized prognostic prediction model was constructed for glioma and miR-196b-5p was identified as a potential biomarker of glioma development.

Current Understanding of Exosomal MicroRNAs in Glioma Immune Regulation and Therapeutic Responses

Exosomes, the small extracellular vesicles, are released by multiple cell types, including tumor cells, and represent a novel avenue for intercellular communication via transferring diverse biomolecules. Recently, microRNAs (miRNAs) were demonstrated to be enclosed in exosomes and therefore was protected from degradation. Such exosomal miRNAs can be transmitted to recipient cells where they could regulate multiple cancer-associated biological processes. Accumulative evidence suggests that exosomal miRNAs serve essential roles in modifying the glioma immune microenvironment and potentially affecting the malignant behaviors and therapeutic responses. As exosomal miRNAs are detectable in almost all kinds of biofluids and correlated with clinicopathological characteristics of glioma, they might be served as promising biomarkers for gliomas. We reviewed the novel findings regarding the biological functions of exosomal miRNAs during glioma pathogenesis and immune regulation. Furthermore, we elaborated on their potential clinical applications as biomarkers in glioma diagnosis, prognosis and treatment response prediction. Finally, we summarized the accessible databases that can be employed for exosome-associated miRNAs identification and functional exploration of cancers, including glioma.

Exosomes: Small vesicles with big roles in cancer, vaccine development, and therapeutics

Cancer is a deadly disease that is globally and consistently one of the leading causes of mortality every year. Despite the availability of chemotherapy, radiotherapy, immunotherapy, and surgery, a cure for cancer has not been attained. Recently, exosomes have gained significant attention due to the therapeutic potential of their various components including proteins, lipids, nucleic acids, miRNAs, and lncRNAs. Exosomes constitute a set of tiny extracellular vesicles with an approximate diameter of 30-100 nm. They are released from different cells and are present in biofluids including blood, cerebrospinal fluid (CSF), and urine. They perform crucial multifaceted functions in the malignant progression of cancer via autocrine, paracrine, and endocrine communications. The ability of exosomes to carry different cargoes including drug and molecular information to recipient cells make them a novel tool for cancer therapeutics. In this review, we discuss the major components of exosomes and their role in cancer progression. We also review important literature about the potential role of exosomes as vaccines and delivery carriers in the context of cancer therapeutics.

Current Strategies for Cancer Cell-Derived Extracellular Vesicles for Cancer Therapy

Cancer cell-derived extracellular vesicles (CEVs), a novel type of therapeutic agent in cancer treatment, can be prepared from the autocrine secretion of various cancer cells, the direct extraction of cancer cells and the combination of cancer cell-derived membranes with advanced materials. With various bioactive molecules, exosomes are produced by cells for intercellular communication. Although cancer cell-derived exosomes are known to inhibit tumor apoptosis and promote the progression of cancer, researchers have developed various innovative strategies to prepare anti-tumor vesicles from cancer cells. With current strategies for anti-tumor vesicles, four different kinds of CEVs are classified including irradiated CEVs, advanced materials combined CEVs, chemotherapeutic drugs loaded CEVs and genetically engineered CEVs. In this way, CEVs can not only be the carriers for anti-tumor drugs to the target tumor area but also act as immune-active agents. Problems raised in the strategies mainly concerned with the preparation, efficacy and application. In this review, we classified and summarized the current strategies for utilizing the anti-tumor potential of CEVs. Additionally, the challenges and the prospects of this novel agent have been discussed.

ANXA1 as a Prognostic and Immune Microenvironmental Marker for Gliomas Based on Transcriptomic Analysis and Experimental Validation

The tumor microenvironment (TME) plays an important role in the growth and invasion of glioma. This study aimed to analyze the composition of the immune microenvironment in glioma samples and analyze the important differentially expressed genes to identify novel immune-targeted therapy for glioma. We downloaded transcriptomic data of 669 glioma samples from The Cancer Genome Atlas database. CIBERSORT and ESTIMATE methods were used to calculate the proportion of tumor-infiltrating immune cells and ratio of immune and stromal components in the TME. The differentially expressed genes (DEGs) were screened by comparing the genes expressed by both stromal and immune cells. Annexin A1 (ANXA1) was determined to be an important prognostic indicator through the common overlap of univariate Cox regression analysis and protein–protein interaction network analysis. The proportion of tumor-infiltrating immune cells, calculated by CIBERSORT algorithm, had a significant difference in distribution among the high and low ANXA1 expression groups, indicating that ANXA1 could be an important immune marker of TME. Furthermore, ANXA1 level was positively correlated with the histopathological factors and negatively related to the survival of glioma patients based on the analysis of multiple databases. Finally, in vitro experiments verified that antagonizing ANXA1 expression promoted cell apoptosis and inhibited the invasion and migration capacities of glioma cells. Therefore, ANXA1 due to its immune-related functions, can be an important prognostic indicator and immune microenvironmental marker for gliomas. Further studies are warranted to confirm ANXA1 as a potential immunotherapeutic target for gliomas.