MiR-21 in the extracellular vesicles (EVs) of cerebrospinal fluid (CSF): a platform for glioblastoma biomarker development

Microvesicles and Microvesicle-Associated microRNAs Reflect Glioblastoma Regression: Microvesicle-Associated miR-625-5p Has Biomarker Potential

Glioblastoma (GB) is the most aggressive and recurrent form of brain cancer in adults. We hypothesized that the identification of biomarkers such as certain microRNAs (miRNAs) and the circulating microvesicles (MVs) that transport them could be key to establishing GB progression, recurrence and therapeutic response. For this purpose, circulating MVs were isolated from the plasma of GB patients (before and after surgery) and of healthy subjects and characterized by flow cytometry. OpenArray profiling and the individual quantification of selected miRNAs in plasma and MVs was performed, followed by target genes’ prediction and in silico survival analysis. It was found that MVs’ parameters (number, EGFRvIII and EpCAM) decreased after the surgical resection of GB tumors, but the inter-patient variability was high. The expression of miR-106b-5p, miR-486-3p, miR-766-3p and miR-30d-5p in GB patients’ MVs was restored to control-like levels after surgery: miR-106b-5p, miR-486-3p and miR-766-3p were upregulated, while miR-30d-5p levels were downregulated after surgical resection. MiR-625-5p was only identified in MVs isolated from GB patients before surgery and was not detected in plasma. Target prediction and pathway analysis showed that the selected miRNAs regulate genes involved in cancer pathways, including glioma. In conclusion, miR-625-5p shows potential as a biomarker for GB regression or recurrence, but further in-depth studies are needed.

Extracellular Vesicles for Regenerative Medicine Applications

Tissue engineering and regenerative medicine (TERM) may be defined as a translational discipline focused on the development of novel techniques, devices, and materials to replace or repair injured or diseased tissue and organs. The main approaches typically use cells, scaffolds, and signaling molecules, either alone or in combination, to promote repair and regeneration. Although cells are required to create new functional tissue, the source of cells, either from an exogenous allogeneic or autologous source or through the recruitment of endogenous (autologous) cells, is technically challenging and risks the host rejection of new tissue. Regardless of the cell source, these approaches also require appropriate instruction for proliferation, differentiation, and in vivo spatial organization to create new functional tissue. Such instruction is supplied through the microenvironment where cells reside, environments which largely consist of the extracellular matrix (ECM). The specific components of the ECM, and broadly the extracellular space, responsible for promoting tissue regeneration and repair, are not fully understood, however extracellular vesicles (EVs) found in body fluids and solid phases of ECM have emerged as key mediators of tissue regeneration and repair. Additionally, these EVs might serve as potential cell-free tools in TERM to promote tissue repair and regeneration with minimal risk for host rejection and adverse sequelae. The past two decades have shown a substantial interest in understanding the therapeutic role of EVs and their applications in the context of TERM. Therefore, the purpose of this review is to highlight the fundamental characteristics of EVs, the current pre-clinical and clinical applications of EVs in TERM, and the future of EV-based strategies in TERM.

The Exosome Journey: From Biogenesis to Regulation and Function in Cancers

Exosomes are a type of small endosomal-derived vesicles ranging from 30 to 150 nm, which can serve as functional mediators in cell-to-cell communication and various physiological and pathological processes. In recent years, exosomes have emerged as crucial mediators of intracellular communication among tumor cells, immune cells, and stromal cells, which can shuttle bioactive molecules, such as proteins, lipids, RNA, and DNA. Exosomes exhibit the high bioavailability, biological stability, targeting specificity, low toxicity, and immune characteristics, suggesting their potentials in the diagnosis and treatment of cancers. They can be applied as an effective tool in the diagnostics, therapeutics, and drug delivery in cancers. This review summarizes the regulation and functions of exosomes in various cancers to augment our understanding of exosomes, which paves the way for parallel advancements in the therapeutic approach of cancers. In this review, we also discuss the challenges and prospects for clinical application of exosome-based diagnostics and therapeutics for cancers.

Molecular and Circulating Biomarkers in Patients with Glioblastoma

Glioblastoma is the most aggressive malignant tumor of the central nervous system with a low survival rate. The difficulty of obtaining this tumor material represents a major limitation, making the real-time monitoring of tumor progression difficult, especially in the events of recurrence or resistance to treatment. The identification of characteristic biomarkers is indispensable for an accurate diagnosis, the rigorous follow-up of patients, and the development of new personalized treatments. Liquid biopsy, as a minimally invasive procedure, holds promise in this regard. The purpose of this paper is to summarize the current literature regarding the identification of molecular and circulating glioblastoma biomarkers and the importance of their integration as a valuable tool to improve patient care.

Diagnostic and Therapeutic Properties of Exosomes in Cardiac Fibrosis

Cardiac fibrosis results from both the differentiation of cardiac fibroblasts and excessive accumulation of extracellular matrix (ECM), leading to myocardial stiffness and reduced compliance of the ventricular wall. The conversion of cardiac fibroblasts to myofibroblasts is the most important initiating step in the process of this pathological cardiac remodeling. It occurs during the progression of many cardiovascular diseases, adversely influencing both the clinical course and outcome of the disease. The pathogenesis is complex and there is no effective treatment. Exosomes are extracellular vesicles that mediate intercellular communication through delivering specific cargoes of functional nucleic acids and proteins derived from particular cell types. Recent studies have found that exosomes play an important role in the diagnosis and treatment of cardiac fibrosis, and is a potential biotherapeutics and drug delivery vectors for the treatment of cardiac fibrosis. The present review aimed to summarize the current knowledge of exosome-related mechanisms underlying cardiac fibrosis and to suggest potential therapy that could be used to treat the condition.

Different Sourced Extracellular Vesicles and Their Potential Applications in Clinical Treatments

Extracellular vesicles (EVs) include a heterogeneous group of natural cell-derived nanostructures that are increasingly regarded as promising biotherapeutic agents and drug delivery vehicles in human medicine. Desirable intrinsic properties of EVs including the ability to bypass natural membranous barriers and to deliver their unique biomolecular cargo to specific cell populations position them as fiercely competitive alternatives for currently available cell therapies and artificial drug delivery platforms. EVs with distinct characteristics can be released from various cell types into the extracellular environment as a means of transmitting bioactive components and altering the status of the target cell. Despite the existence of a large number of preclinical studies confirming the therapeutic efficacy of different originated EVs for treating several pathological conditions, in this review, we first provide a brief overview of EV biophysical properties with an emphasis on their intrinsic therapeutic benefits over cell-based therapies and synthetic delivery systems. Next, we describe in detail different EVs derived from distinct cell sources, compare their advantages and disadvantages, and recapitulate their therapeutic effects on various human disorders to highlight the progress made in harnessing EVs for clinical applications. Finally, knowledge gaps and concrete hurdles that currently hinder the clinical translation of EV therapies are debated with a futuristic perspective.

Glioma extracellular vesicles for precision medicine: prognostic and theragnostic application

EV produced by tumour cells carry a diverse population of proteins, lipids, DNA, and RNA molecules throughout the body and appear to play an important role in the overall development of the disease state, according to growing data. Gliomas account for a sizable fraction of all primary brain tumours and the vast majority of brain malignancies. Glioblastoma multiforme (GBM) is a kind of grade IV glioma that has a very dismal prognosis despite advancements in diagnostic methods and therapeutic options. The authors discuss advances in understanding the function of extracellular vesicles (EVs), in overall glioma growth, as well as how recent research is uncovering the utility of EVs in glioma diagnostics, prognostic and therapeutics approaches.

Microfluidics for detection of exosomes and microRNAs in cancer: State of the art

Exosomes are small extracellular vesicles with sizes ranging from 30-150 nanometers that contain proteins, lipids, mRNAs, microRNAs, and double-stranded DNA derived from the cells of origin. Exosomes can be taken up by target cells, acting as a means of cell-to-cell communication. The discovery of these vesicles in body fluids and their participation in cell communication has led to major breakthroughs in diagnosis, prognosis, and treatment of several conditions (e.g., cancer). However, conventional isolation and evaluation of exosomes and their microRNA content suffers from high cost, lengthy processes, difficult standardization, low purity, and poor yield. The emergence of microfluidics devices with increased efficiency in sieving, trapping, and immunological separation of small volumes could provide improved detection and monitoring of exosomes involved in cancer. Microfluidics techniques hold promise for advances in development of diagnostic and prognostic devices. This review covers ongoing research on microfluidics devices for detection of microRNAs and exosomes as biomarkers and their translation to point-of-care and clinical applications.

Role of Acute Myeloid Leukemia (AML)-Derived exosomes in tumor progression and survival

Acute myeloid leukemia (AML) is a quickly aggressive hematopoietic disorder that progress due to the accumulation and clonal expansion of immature myeloid cells. Despite the latest developments in AML treatment, repeated relapses and drug resistance remain one of the major challenges in treatment of leukemia. Currently, it is well known that the components of the tumor microenvironment such as cellular and non-cellular elements play a critical function in treatment failures of AML, also they are most common cause of complications including suppression of hematopoiesis. Exosomes are membrane-bound extracellular vesicles (EVs) that transfer signaling molecules and have attracted a large amount of attention due to their important role in inter-cellular communication in health and disease. Exosomes participate in the survival and chemoresistance of many leukemia through transferring their rich cargos of molecules including miRNAs, growth factors, and cytokines. The key producers of exosomes that mainly participate to AML pathogenesis are bone marrow mesenchymal stem cell (BMSCs) and AML cell themselves. These cells release an enormous number of exosomes that affect several target cells such as natural killer (NK) and hematopoietic stem cells to the development of leukemia proliferation and progression. In the present study, a comprehensive review of the literature has been done to briefly discuss the biology of exosomes and highlight the role of exosomes derived from AML in the progress of acute myeloid leukemia.

Exosome: The “Off-the-Shelf” Cellular Nanocomponent as a Potential Pathogenic Agent, a Disease Biomarker, and Neurotherapeutics

Exosomes are nanosized “off-the-shelf” lipid vesicles released by almost all cell types and play a significant role in cell–cell communication. Exosomes have already been proven to carry cell-specific cargos of proteins, lipids, miRNA, and noncoding RNA (ribonucleic acid). These vesicles can be selectively taken up by the neighboring cell and can regulate cellular functions. Herein, we have discussed three different roles of exosomes in neuroscience. First, we have discussed how exosomes play the role of a pathogenic agent as a part of cell–cell communication and transmit pathogens such as amyloid-beta (Aβ), further helping in the propagation of neurodegenerative and other neurological diseases. In the next section, the review talks about the role of exosomes in biomarker discovery in neurological disorders. Toward the end, we have reviewed how exosomes can be harnessed and engineered for therapeutic purposes in different brain diseases. This review is based on the current knowledge generated in this field and our comprehension of this domain.

Extracellular Vesicle-Based Multianalyte Liquid Biopsy as a Diagnostic for Cancer

Liquid biopsy is the analysis of materials shed by tumors into circulation, such as circulating tumor cells, nucleic acids, and extracellular vesicles (EVs), for the diagnosis and management of cancer. These assays have rapidly evolved with recent FDA approvals of single biomarkers in patients with advanced metastatic disease. However, they have lacked sensitivity or specificity as a diagnostic in early-stage cancer, primarily due to low concentrations in circulating plasma. EVs, membrane-enclosed nanoscale vesicles shed by tumor and other cells into circulation, are a promising liquid biopsy analyte owing to their protein and nucleic acid cargoes carried from their mother cells, their surface proteins specific to their cells of origin, and their higher concentrations over other noninvasive biomarkers across disease stages. Recently, the combination of EVs with non-EV biomarkers has driven improvements in sensitivity and accuracy; this has been fueled by the use of machine learning (ML) to algorithmically identify and combine multiple biomarkers into a composite biomarker for clinical prediction. This review presents an analysis of EV isolation methods, surveys approaches for and issues with using ML in multianalyte EV datasets, and describes best practices for bringing multianalyte liquid biopsy to clinical implementation. Expected final online publication date for the Annual Review of Biomedical Data Science, Volume 5 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The diagnostic value of serum miR-21 in patients with ovarian cancer: a systematic review and meta-analysis

Objective

There have been a variety of published studies on the expression of serum miR-21 in patients with ovarian cancer associated with the diagnostic value of ovarian cancer, but the conclusions are not clearly elucidated. This study aims to evaluate the value of serum miR-21 expression in the diagnosis of patients with ovarian cancer by meta-analysis.

Methods

Databases, such as PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), and China WanFang, were searched for relevant studies upon the correlation between the expression of serum miR-21 and the diagnostic value of ovarian cancer from inception to March 7, 2022. Statistical analysis was performed using Stata 15.0 software. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were calculated. The meta-regression analysis and subgroup analysis were used to explore the sources of heterogeneity. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) system was used to evaluate the quality of the included literature.

Results

A total of 6 articles were included in the meta-analysis. The results showed that the pooled sensitivity, specificity, PLR, NLR, and DOR were 0.81 (95%CI: 0.73–0.88), 0.82 (95%CI: 0.75–0.87), 4.51 (95%CI: 3.22–6.31), 0.23 (95%CI: 0.16–0.33), and 19.87 (95% CI: 11.27–35.03), respectively. The area under the summary receiver operating characteristic curve was 0.89 (95%CI: 0.85–0.91). No significant publication bias was found (P > 0.05).

Conclusion

Serum miR-21 has a good diagnostic value for ovarian cancer, which can be an ideal diagnostic biomarker for ovarian cancer. However, we should gingerly use miR-21 as a diagnostic reference standard, due to the limited number of included studies and heterogeneity.

miR-3184-3p enriched in CSF exosomes contribute to progression of glioma and promotes M2-like macrophage polarization

Liquid biopsy is a novel strategy for tumour diagnosis. The contents of cerebrospinal fluid (CSF) exosomes could reflect glioma status, hence sampling exosomes from CSF is a means of liquid biopsy for glioma. However, few studies have focused on the function of microRNAs in CSF exosomes. In this study, we found that miR‐3184‐3p was enriched in CSF exosomes in glioma patients and was downregulated after tumour resection. We found that miR‐3184 facilitates glioma progression in two ways. On the one hand, miR‐3184 directly promotes proliferation, migration, and invasion while inhibiting apoptosis in glioma. On the other hand, miR‐3184 in glioma‐derived exosomes polarizes macrophages to an M2‐like phenotype, which further aggravates tumour progression. Overall, the current findings uncovered a new mechanism and highlighted the significant role of miR‐3184 in glioma progression. Furthermore, exosomal miR‐3184 could be a considerable factor with potential applications in glioma diagnosis and treatment in the future.

Tumor-derived extracellular vesicles: Potential tool for cancer diagnosis, prognosis, and therapy

Various types of cancer pose a notable threat to human health globally. To date, many researchers have undertaken the search for anticancer therapies. However, many anticancer therapeutic approaches accompany many undesirable hazards. In this respect, extracellular vesicles as a whole gained excessive attention from the research community owing to their remarkable potential for delivery of anticancer agents since they are involved in distal intercellular communication via biological cargoes. With the discovery of the fact that tumor cells discharge huge quantities of EVs, new insights have been developed in cancer diagnosis and treatment. Tumor-derived extracellular vesicles (TD-EVs) can be distinguished from the normal cell-derived EVs due to the presence of specific labels on their surface. TD-EVs carry specific oncogenic proteins and the nucleic acids on their surface membrane that participate in tumor progression. Moreover, the proportion of these nucleic acids and the protein greatly varies among malignant and healthy cell-derived EVs. The diagnostic potential of TD-EVs can be implied for the more precise and early-stage detection of cancer that was impossible in the past. This review examines the recent progress in prognostic, diagnostic, and therapeutic potential of the EVs derived from the tumor cells.

Extracellular Vesicles Secreted by Glioma Stem Cells Are Involved in Radiation Resistance and Glioma Progression

Glioblastoma is the most aggressive brain tumour with short survival, partly due to resistance to conventional therapy. Glioma stem cells (GSC) are likely to be involved in treatment resistance, by releasing extracellular vesicles (EVs) containing specific molecular cargoes. Here, we studied the EVs secreted by glioma stem cells (GSC-EVs) and their effects on radiation resistance and glioma progression. EVs were isolated from 3 GSCs by serial centrifugation. NanoSight measurement, cryo-electron microscopy and live imaging were used to study the EVs size, morphology and uptake, respectively. The non-GSC glioma cell lines LN229 and U118 were utilised as a recipient cell model. Wound healing assays were performed to detect cell migration. Colony formation, cell viability and invadopodium assays were conducted to detect cell survival of irradiated recipient cells and cell invasion post GSC-EV treatment. NanoString miRNA global profiling was used to select for the GSC-EVs’ specific miRNAs. All three GSC cell lines secreted different amounts of EVs, and all expressed consistent levels of CD9 but different level of Alix, TSG101 and CD81. EVs were taken up by both LN229 and U118 recipient cells. In the presence of GSC-EVs, these recipient cells survived radiation exposure and initiated colony formation. After GSC-EVs exposure, LN229 and U118 cells exhibited an invasive phenotype, as indicated by an increase in cell migration. We also identified 25 highly expressed miRNAs in the GSC-EVs examined, and 8 of these miRNAs can target PTEN. It is likely that GSC-EVs and their specific miRNAs induced the phenotypic changes in the recipient cells due to the activation of the PTEN/Akt pathway. This study demonstrated that GSC-EVs have the potential to induce radiation resistance and modulate the tumour microenvironment to promote glioma progression. Future therapeutic studies should be designed to interfere with these GSC-EVs and their specific miRNAs.

Exosomes Immunity Strategy: A Novel Approach for Ameliorating Intervertebral Disc Degeneration

Low back pain (LBP), which is one of the most severe medical and social problems globally, has affected nearly 80% of the population worldwide, and intervertebral disc degeneration (IDD) is a common musculoskeletal disorder that happens to be the primary trigger of LBP. The pathology of IDD is based on the impaired homeostasis of catabolism and anabolism in the extracellular matrix (ECM), uncontrolled activation of immunologic cascades, dysfunction, and loss of nucleus pulposus (NP) cells in addition to dynamic cellular and biochemical alterations in the microenvironment of intervertebral disc (IVD). Currently, the main therapeutic approach regarding IDD is surgical intervention, but it could not considerably cure IDD. Exosomes, extracellular vesicles with a diameter of 30–150 nm, are secreted by various kinds of cell types like stem cells, tumor cells, immune cells, and endothelial cells; the lipid bilayer of the exosomes protects them from ribonuclease degradation and helps improve their biological efficiency in recipient cells. Increasing lines of evidence have reported the promising applications of exosomes in immunological diseases, and regarded exosomes as a potential therapeutic source for IDD. This review focuses on clarifying novel therapies based on exosomes derived from different cell sources and the essential roles of exosomes in regulating IDD, especially the immunologic strategy.

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.

Evaluation of exosomal non-coding RNAs in cancer using high-throughput sequencing

Clinical oncologists need more reliable and non-invasive diagnostic and prognostic biomarkers to follow-up cancer patients. However, the existing biomarkers are often invasive and costly, emphasizing the need for the development of biomarkers to provide convenient and precise detection. Extracellular vesicles especially exosomes have recently been the focus of translational research to develop non-invasive and reliable biomarkers for several diseases such as cancers, suggesting as a valuable source of tumor markers. Exosomes are nano-sized extracellular vesicles secreted by various living cells that can be found in all body fluids including serum, urine, saliva, cerebrospinal fluid, and ascites. Different molecular and genetic contents of their origin such as nucleic acids, proteins, lipids, and glycans in a stable form make exosomes a promising approach for various cancers' diagnoses, prediction, and follow-up in a minimally invasive manner. Since exosomes are used by cancer cells for intercellular communication, they play a critical role in the disease process, highlighting the importance of their use as clinically relevant biomarkers. However, regardless of the advantages that exosome-based diagnostics have, they suffer from problems regarding their isolation, detection, and characterization of their contents. This study reviews the history and biogenesis of exosomes and discusses non-coding RNAs (ncRNAs) and their potential as tumor markers in different types of cancer, with a focus on next generation sequencing (NGS) as a detection method. Moreover, the advantages and challenges associated with exosome-based diagnostics are also presented.

A new transgene mouse model using an extravesicular EGFP tag enables affinity isolation of cell-specific extracellular vesicles

The in vivo function of cell-derived extracellular vesicles (EVs) is challenging to establish since cell-specific EVs are difficult to isolate and differentiate. We, therefore, created an EV reporter using truncated CD9 to display enhanced green fluorescent protein (EGFP) on the EV surface. CD9truc-EGFP expression in cells did not affect EV size and concentration but enabled co-precipitation of EV markers TSG101 and ALIX from the cell-conditioned medium by anti-GFP immunoprecipitation. We then created a transgenic mouse where CD9truc-EGFP was inserted in the inverse orientation and double-floxed, ensuring irreversible Cre recombinase-dependent EV reporter expression. We crossed the EV reporter mice with mice expressing Cre ubiquitously (CMV-Cre), in cardiomyocytes (αMHC-MerCreMer) and renal tubular epithelial cells (Pax8-Cre), respectively. The CD9truc-EGFP positive mice showed Cre-dependent EGFP expression, and plasma CD9truc-EGFP EVs were immunoprecipitated only from CD9truc-EGFP positive CD9truc-EGFPxCMV-Cre and CD9truc-EGFPxαMHC-Cre mice, but not in CD9truc-EGFPxPax8-Cre and CD9truc-EGFP negative mice. In urine samples, CD9truc-EGFP EVs were detected by immunoprecipitation only in CD9truc-EGFP positive CD9truc-EGFPxCMV-Cre and CD9truc-EGFPxPax8-Cre mice, but not CD9truc-EGFPxαMHC-Cre and CD9truc-EGFP negative mice. In conclusion, our EV reporter mouse model enables Cre-dependent EV labeling, providing a new approach to studying cell-specific EVs in vivo and gaining a unique insight into their physiological and pathophysiological function.

Insights into Exosome in the Intervertebral Disc: Emerging Role for Disc Homeostasis and Normal Function

Low back pain (LBP) is a chronic condition that causes great individual suffering and economic burden. The major contributor of LBP is intervertebral disc degeneration (IDD), which is caused by a spectrum of homeostasis alteration, including the apoptosis of nucleus pulposus (NP) and annulus fibrosus (AF) cells, degradation of extracellular matrix (ECM), calcification of cartilaginous endplates (CEP) and so on. Currently, the therapeutic strategy for IDD includes conservative and surgery treatment. Nevertheless, none of them could reverse the progressive destruction of the intervertebral disc. Hence, it is pivotal to pursue a new therapeutic approach. Exosomes, nano-sized substances with diameters of 30-150 nm, can be synthesized and secreted by various types of cells. They play an important role in intercellular communication. Increasing evidence implicates that exosomes could impact the intracellular transcription activities, thereby inhibiting or accelerating the proliferation and apoptosis of cells. Thus, it is a new therapeutic source for IDD. This review chiefly focuses on generalizing and clarifying the roles of exosomes in the onset and deterioration of IDD, and their therapeutic potential.

The Study of Cerebrospinal Fluid microRNAs in Spinal Cord Injury and Neurodegenerative Diseases: Methodological Problems and Possible Solutions

Despite extensive research on neurological disorders, unanswered questions remain regarding the molecular mechanisms underpinning the course of these diseases, and the search continues for effective biomarkers for early diagnosis, prognosis, or therapeutic intervention. These questions are especially acute in the study of spinal cord injury (SCI) and neurodegenerative diseases. It is believed that the changes in gene expression associated with processes triggered by neurological disorders are the result of post-transcriptional gene regulation. microRNAs (miRNAs) are key regulators of post-transcriptional gene expression and, as such, are often looked to in the search for effective biomarkers. We propose that cerebrospinal fluid (CSF) is potentially a source of biomarkers since it is in direct contact with the central nervous system and therefore may contain biomarkers indicating neurodegeneration or damage to the brain and spinal cord. However, since the abundance of miRNAs in CSF is low, their isolation and detection is technically difficult. In this review, we evaluate the findings of recent studies of CSF miRNAs as biomarkers of spinal cord injury (SCI) and neurodegenerative diseases. We also summarize the current knowledge concerning the methods of studying miRNA in CSF, including RNA isolation and normalization of the data, highlighting the caveats of these approaches and possible solutions.

A systematic update to circulating extracellular vesicles proteome; transcriptome and small RNA-ome as glioma diagnostic, prognostic and treatment-response biomarkers

Brain gliomas are major neurosurgical challenges due to high mortality and morbidity. Hence, development of novel biomarkers is of great value to plan appropriate treatment strategy. Evaluation of the molecular content of extracellular vesicles (EVs) as novel non-invasive biomarker repertoires can provide a real-time portrait of disease status. This study aims to provide a systematic, comprehensive and critical report of the diagnostic and prognostic significance of EV biomarkers (proteins, DNAs and RNAs) for brain gliomas, discuss their biogenesis and passage through the blood brain barrier, and also highlight the high throughput methods used for EV biomarker discovery; as well as discussing potential limitations of EV isolation and characterization methods as glioma diagnostic, prognostic or treatment response biomarkers. Moreover, we critically appraise the bias risk in the previous studies, discuss the limitations EV biomarker discovery faces to enter neurosurgical practice in the future, and highlight the need for more optimized protocols for EV isolation and biomarker discovery in high throughput studies. The current systematic review was conducted upon PRISMA guidelines [10].

Research Progress on Circular RNA in Glioma

The discovery of circular RNA (circRNA) greatly complements the traditional gene expression theory. CircRNA is a class of non-coding RNA with a stable cyclic structure. They are highly expressed, spatiotemporal-specific and conservative across species. Importantly, circRNA participates in the occurrence of many kinds of tumors and regulates the tumor development. Glioma is featured by limited therapy and grim prognosis. Cancer-associated circRNA compromises original function or creates new effects in glioma, thus contributing to oncogenesis. Therefore, this article reviews the biogenesis, metabolism, functions and properties of circRNA as a novel potential biomarker for gliomas. We elaborate the expression characteristics, interaction between circRNA and other molecules, aiming to identify new targets for early diagnosis and treatment of gliomas.

Exploratory Profiling of Extracellular MicroRNAs in Cerebrospinal Fluid Comparing Leptomeningeal Metastasis with Other Central Nervous System Tumor Statuses

The diagnosis of leptomeningeal metastasis (LM) is often difficult due to the paucity of cancer cells in cerebrospinal fluid (CSF) and nonspecific findings on neuroimaging. Investigations of extracellular microRNAs (miRNAs) in CSF could be used for both the diagnosis and study of LM pathogenesis because they reflect the activity of disseminating cancer cells. We isolated CSF extracellular miRNAs from patients (n = 65) of different central nervous system tumor statuses, including cancer control, healthy control, LM, brain metastasis (BM), and primary brain tumor (BT) groups, and performed miRNA microarrays. In unsupervised clustering analyses, all LM and two BM samples showed unique profiles. Among 30 miRNAs identified for LM-specific biomarkers via a Prediction Analysis of Microarrays, miR-335-5p and miR-34b-3p were confirmed in both the discovery and validation samples (n = 23). Next, we performed a significance analysis of the microarray (SAM) to extract discriminative miRNA profiles of two selected CSF groups, with LM samples revealing a greater number of discriminative miRNAs than BM and BT samples compared to controls. Using SAM comparisons between LM and BM samples, we identified 30 upregulated and 6 downregulated LM miRNAs. To reduce bias from different primary cancers, we performed a subset analysis with primary non-small cell lung cancer, and 12 of 13 upregulated miRNAs in LM vs. BM belonged to the upregulated miRNAs in LM. We identified possible target genes and their biological processes that could be affected by LM discriminative miRNAs in NSCLC using the gene ontology database. In conclusion, we identified a unique extracellular miRNA profile in LM CSF that was different from BM, suggesting the use of miRNAs as LM biomarkers in studies of LM pathogenesis.

Liquid Biopsy in Glioblastoma Management: From Current Research to Future Perspectives

Glioblastoma (GBM) is the most common primary tumor of the central nervous system. Arising from neuroepithelial glial cells, GBM is characterized by invasive behavior, extensive angiogenesis, and genetic heterogeneity that contributes to poor prognosis and treatment failure. Currently, there are several molecular biomarkers available to aid in diagnosis, prognosis, and predicting treatment outcomes; however, all require the biopsy of tumor tissue. Nevertheless, a tissue sample from a single location has its own limitations, including the risk related to the procedure and the difficulty of obtaining longitudinal samples to monitor treatment response and to fully capture the intratumoral heterogeneity of GBM. To date, there are no biomarkers in blood or cerebrospinal fluid for detection, follow-up, or prognostication of GBM. Liquid biopsy offers an attractive and minimally invasive solution to support different stages of GBM management, assess the molecular biology of the tumor, identify early recurrence and longitudinal genomic evolution, predict both prognosis and potential resistance to chemotherapy or radiotherapy, and allow patient selection for targeted therapies. The aim of this review is to describe the current knowledge regarding the application of liquid biopsy in glioblastoma, highlighting both benefits and obstacles to translation into clinical care. IMPLICATIONS FOR PRACTICE: To translate liquid biopsy into clinical practice, further prospective studies are required with larger cohorts to increase specificity and sensitivity. With the ever-growing interest in RNA nanotechnology, microRNAs may have a therapeutic role in brain tumors.

The role of extracellular vesicles in the physiological and pathological regulation of the blood-brain barrier

Extracellular vesicles (EVs) are a subclass of biological nanoparticles secreted by most cell types. Once secreted, EVs can travel long distances to deliver their content to target cells thereby playing a key role in cell-to-cell communication and supporting both physiological and pathological processes. In recent years, the functional versatility of EVs has come to be more widely appreciated. Their heterogeneous structure encloses solubilized bioactive cargoes including proteins and nucleic acids. EVs mirror the secreting cell in composition therefore representing a novel source of diagnostic and prognostic biomarkers. Moreover, due to their unique structure, EVs constitute a promising class of biocompatible nanovehicles for drug delivery as well. Importantly, and of burgeoning interest, is the fact that EVs have the intrinsic ability to breach biological barriers including the complex blood-brain barrier (BBB), whose restrictive nature represents a significant therapeutic challenge. EVs have been shown to contribute to the progression of a variety of brain diseases including metastatic brain cancer, neurodegenerative diseases, and acute pathologies including infections and ischemia. In this review, the role of EVs in the maintenance and regulation of the BBB under normal physiological and pathologic conditions are discussed. Applications of EVs as therapeutic and diagnostic tools in the treatment of diseases that affect the central nervous system are presented as are limitations hindering their broad translation and potential solutions to resolve them.

A systematic review of extracellular vesicles as non-invasive biomarkers in glioma diagnosis, prognosis, and treatment response monitoring

The present systematic review was done to investigate the possible application of Extracellular vesicles (EVs) in the diagnosis, prognosis, and treatment response monitoring of gliomas using available literature to wrap up the final applicable conclusion in this regard. we searched PubMed/MEDLINE, Scopus, and ISI Web of Science databases. Authors evaluated the quality of the included studies by the QUADAS-2 tool. In total, 2037 published datasets were retrieved through systematic search. Upon screening for eligibility, 35 datasets were determined as eligible. Exosome was the EV-subtype described in the majority of studies, and most datasets used serum as the primary EVs isolation source. EVs isolation was primarily conducted by ultracentrifugation. 31 datasets reported that EVs hold considerable potential for being used in diagnostics, with the majority reporting different types of miRNAs as biomarkers. Besides, 8 datasets reported that EVs could be a potential source of prognostic biomarkers. And finally, 3 datasets reported that EVs might be a reliable strategy for monitoring therapy response in glioma patients. According to the findings of the current systematic review, it seems that miR-301, miR-21, and HOTAIR had the highest diagnostic accuracy. However, heterogeneous and limited evidence regarding prognosis and treatment response monitoring precludes us from drawing a practical conclusion regarding EVs.

A review of the role of extracellular vesicles in neonatal physiology and pathology

Extracellular vesicles (EVs) are cell-derived membrane-bound particles, extensively investigated across many fields to improve the understanding of pathophysiological processes, as biomarkers of disease and as therapeutic targets for pharmacological intervention. We aim to describe the current knowledge of EVs detected in the body fluids of human neonates, both term and preterm, from birth to 4 weeks of age. To date, EVs have been described in several neonatal body fluids, including cerebrospinal fluid, umbilical cord blood, neonatal blood, tracheal aspirates and urine. These studies demonstrate some important roles of EVs in the neonatal population, particularly in haemostasis. Moreover, some studies have demonstrated the pathophysiological mechanisms and the identification of potential biomarkers of neonatal disease. We must continue to build on this knowledge, evaluating the role of EVs in neonatal pathology, particularly in prematurity and during the perinatal adaption period. Future studies should use larger numbers, robust EV characterisation techniques and always correlate the findings to clinical outcomes. IMPACT: This article summarises the current knowledge of the effect of EVs in neonates. It describes the potential compensatory role of EVs in neonatal haemostasis. It also describes the role of EVs as mediators of pathology and as potential biomarkers of perinatal and neonatal disease.

Exosome-derived noncoding RNAs in gastric cancer: functions and clinical applications

Exosomes are a subpopulation of the tumour microenvironment (TME) that transmit various biological molecules to promote intercellular communication. Exosomes are derived from nearly all types of cells and exist in all body fluids. Noncoding RNAs (ncRNAs) are among the most abundant contents in exosomes, and some ncRNAs with biological functions are specifically packaged into exosomes. Recent studies have revealed that exosome-derived ncRNAs play crucial roles in the tumorigenesis, progression and drug resistance of gastric cancer (GC). In addition, regulating the expression levels of exosomal ncRNAs can promote or suppress GC progression. Moreover, the membrane structures of exosomes protect ncRNAs from degradation by enzymes and other chemical substances, significantly increasing the stability of exosomal ncRNAs. Specific hallmarks within exosomes that can be used for exosome identification, and specific contents can be used to determine their origin. Therefore, exosomal ncRNAs are suitable for use as diagnostic and prognostic biomarkers or therapeutic targets. Regulating the biogenesis of exosomes and the expression levels of exosomal ncRNAs may represent a new way to block or eradicate GC. In this review, we summarized the origins and characteristics of exosomes and analysed the association between exosomal ncRNAs and GC development.

The Role of Non-coding RNAs in the Pathogenesis of Glial Tumors

Among the many malignant neoplasms, glioblastoma (GBM) leads to one of the worst prognosis for patients and has an almost 100% recurrence rate. The only chemotherapeutic drug that is widely used for treating glioblastoma is temozolomide, a DNA alkylating agent. Its impact, however, is only minor; it increases patients' survival just by 12 to 14 months. Multiple highly selective compounds that affect specific proteins and have performed well in other types of cancer have proved ineffective against glioblastoma. Hence, there is an urgent need for novel methods that could help achieve the long-awaited progress in glioblastoma treatment. One of the potentially promising approaches is the targeting of non-coding RNAs (ncRNAs). These molecules are characterized by extremely high multifunctionality and often act as integrators by coordinating multiple key signaling pathways within the cell. Thus, the impact on ncRNAs has the potential to lead to a broader and stronger impact on cells, as opposed to the more focused action of inhibitors targeting specific proteins. In this review, we summarize the functions of long noncoding RNAs, circular RNAs, as well as microRNAs, PIWI-interacting RNAs, small nuclear and small nucleolar RNAs. We provide a classification of these transcripts and describe their role in various signaling pathways and physiological processes. We also provide examples of oncogenic and tumor suppressor ncRNAs belonging to each of these classes in the context of their involvement in the pathogenesis of gliomas and glioblastomas. In conclusion, we considered the potential use of ncRNAs as diagnostic markers and therapeutic targets for the treatment of glioblastoma.

The Multifaceted Role of Extracellular Vesicles in Glioblastoma: microRNA Nanocarriers for Disease Progression and Gene Therapy

Glioblastoma (GB) is the most aggressive form of brain cancer in adults, characterized by poor survival rates and lack of effective therapies. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression post-transcriptionally through specific pairing with target messenger RNAs (mRNAs). Extracellular vesicles (EVs), a heterogeneous group of cell-derived vesicles, transport miRNAs, mRNAs and intracellular proteins, and have been shown to promote horizontal malignancy into adjacent tissue, as well as resistance to conventional therapies. Furthermore, GB-derived EVs have distinct miRNA contents and are able to penetrate the blood-brain barrier. Numerous studies have attempted to identify EV-associated miRNA biomarkers in serum/plasma and cerebrospinal fluid, but their collective findings fail to identify reliable biomarkers that can be applied in clinical settings. However, EVs carrying specific miRNAs or miRNA inhibitors have great potential as therapeutic nanotools in GB, and several studies have investigated this possibility on in vitro and in vivo models. In this review, we discuss the role of EVs and their miRNA content in GB progression and resistance to therapy, with emphasis on their potential as diagnostic, prognostic and disease monitoring biomarkers and as nanocarriers for gene therapy.

Serum Extracellular Vesicle-Derived circHIPK3 and circSMARCA5 Are Two Novel Diagnostic Biomarkers for Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most frequent and deadly human brain cancer. Early diagnosis through non-invasive biomarkers may render GBM more easily treatable, improving the prognosis of this currently incurable disease. We suggest the use of serum extracellular vesicle (sEV)-derived circular RNAs (circRNAs) as highly stable minimally invasive diagnostic biomarkers for GBM diagnosis. EVs were isolated by size exclusion chromatography from sera of 23 GBM and 5 grade 3 glioma (GIII) patients, and 10 unaffected controls (UC). The expression of two candidate circRNAs (circSMARCA5 and circHIPK3) was assayed by droplet digital PCR. CircSMARCA5 and circHIPK3 were significantly less abundant in sEVs from GBM patients with respect to UC (fold-change (FC) of -2.15 and -1.92, respectively) and GIII (FC of -1.75 and -1.4, respectively). Receiver operating characteristic curve (ROC) analysis, based on the expression of sEV-derived circSMARCA5 and circHIPK3, allowed us to distinguish GBM from UC (area under the curve (AUC) 0.823 (0.667-0.979) and 0.855 (0.704 to 1.000), with a 95% confidence interval (CI), respectively). Multivariable ROC analysis, performed by combining the expression of sEV-derived circSMARCA5 and circHIPK3 with preoperative neutrophil to lymphocyte (NLR), platelet to lymphocyte (PLR) and lymphocyte to monocyte (LMR) ratios, three known diagnostic and prognostic GBM markers, allowed an improvement in the GBM diagnostic accuracy (AUC 0.901 (0.7912 to 1.000), 95% CI). Our data suggest sEV-derived circSMARCA5 and circHIPK3 as good diagnostic biomarkers for GBM, especially when associated with preoperative NLR, PLR and LMR.

Current Development of Glioblastoma Therapeutic Agents

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary brain tumor in humans. Over the past several decades, despite improvements in neurosurgical techniques, development of powerful chemotherapeutic agents, advances in radiotherapy, and comprehensive genomic profiling and molecular characterization, treatment of GBM has achieved very limited success in increasing overall survival. Thus, identifying and understanding the key molecules and barriers responsible for the malignant phenotypes and treatment resistance of GBM will yield new potential therapeutic targets. We review the most recent development of receptor tyrosine kinase targeted therapy for GBM and discuss the current status of several novel strategies with the emphasis on blood-brain barrier penetration as a major obstacle for small-molecule drugs to achieve their therapeutic goals. Likewise, a major opportunity for the treatment of GBM lies in the use of biomarkers for the discovery and development of new receptor tyrosine kinase targeted therapy.

The role of extracellular vesicles in regulating local and systemic inflammation in cardiovascular disease

Extracellular vesicles are heterogeneous structures surrounded by cell membranes and carry complex contents including nucleotides, proteins, and lipids. These proteins include cytokines and chemokines that are important for exaggerating local and systemic inflammation in disease. Extracellular vesicles are mainly categorized as exosomes and micro-vesicles, which are directly shed from the endosomal system or originated from the cell membrane, respectively. By transporting several bioactive molecules to recipient cells and tissues, extracellular vesicles have favorable, neutral, or detrimental impacts on their targets, such as switching cell phenotype, modulating gene expression, and controlling biological pathways such as inflammatory cell recruitment, activation of myeloid cells and cell proliferation. Extracellular vesicles mediate these functions via both autocrine and paracrine signaling. In the cardiovascular system, extracellular vesicles can be secreted by multiple cell types like cardiomyocytes, smooth muscle cells, macrophages, monocytes, fibroblasts, and endothelial cells, and affect functions of cells or tissues in distant organs. These effects involve maintaining homeostasis, regulating inflammation, and triggering pathological process in cardiovascular disease. In this review, we mainly focus on the role of micro-vesicles and exosomes, two important subtypes of extracellular vesicles, in local and systemic inflammation in cardiovascular diseases such as myocardial infarction, atherosclerosis and heart failure. We summarize recent findings and knowledge on the effect of extracellular vesicles in controlling both humoral and cellular immunity, and the therapeutic approaches to harness this knowledge to control exacerbated inflammation in cardiovascular diseases.

Biomarkers for differentiating grade II meningiomas from grade I: a systematic review

INTRODUCTION

There are a number of prognostic markers (methylation, CDKN2A/B) described to be useful for the stratification of meningiomas. However, there are currently no clinically validated biomarkers for the preoperative prediction of meningioma grade, which is determined by the histological analysis of tissue obtained from surgery. Accurate preoperative biomarkers would inform the pre-surgical assessment of these tumours, their grade and prognosis and refine the decision-making process for treatment. This review is focused on the more controversial grade II tumours, where debate still surrounds the need for adjuvant therapy, repeat surgery and frequency of follow up.

METHODS

We evaluated current literature for potential grade II meningioma clinical biomarkers, focusing on radiological, biochemical (blood assays) and immunohistochemical markers for diagnosis and prognosis, and how they can be used to differentiate them from grade I meningiomas using the post-2016 WHO classification. To do this, we conducted a PUBMED, SCOPUS, OVID SP, SciELO, and INFORMA search using the keywords; 'biomarker', 'diagnosis', 'atypical', 'meningioma', 'prognosis', 'grade I', 'grade 1', 'grade II' and 'grade 2'.

RESULTS

We identified 1779 papers, 20 of which were eligible for systematic review according to the defined inclusion and exclusion criteria. From the review, we identified radiological characteristics (irregular tumour shape, tumour growth rate faster than 3cm³/year, high peri-tumoural blood flow), blood markers (low serum TIMP1/2, high serum HER2, high plasma Fibulin-2) and histological markers (low H3K27me3, low SMARCE1, low AKAP12, high ARIDB4) that may aid in differentiating grade II from grade I meningiomas.

CONCLUSION

Being able to predict meningioma grade at presentation using the radiological and blood markers described may influence management as the likely grade II tumours will be followed up or treated more aggressively, while the histological markers may prognosticate progression or post-treatment recurrence. This to an extent offers a more personalised treatment approach for patients.

Extracellular Vesicles as a Novel Liquid Biopsy-Based Diagnosis for the Central Nervous System, Head and Neck, Lung, and Gastrointestinal Cancers: Current and Future Perspectives

Simple Summary

To improve clinical outcomes, early diagnosis is mandatory in cancer patients. Several diagnostic approaches have been proposed, however, the main drawback relies on the invasive procedures required. Extracellular vesicles (EVs) are bilayer lipid membrane structures released by almost all cells and transferred to remote sites via the bloodstream. The observation that their cargo reflects the cell of origin has opened a new frontier for non-invasive biomarker discovery in oncology. Moreover, since EVs can be recovered from different body fluids, their impact as a Correctdiagnostic tool has gained particular interest. Hence, in the last decade, several studies using different biological fluids have been performed, showing the valuable contributions of EVs as tumour biomarkers, and their improved diagnostic power when combined with currently available tumour markers. In this review, the most relevant data on the diagnostic relevance of EVs, alone or in combination with the well-established tumour markers, are discussed.

Abstract

Early diagnosis, along with innovative treatment options, are crucial to increase the overall survival of cancer patients. In the last decade, extracellular vesicles (EVs) have gained great interest in biomarker discovery. EVs are bilayer lipid membrane limited structures, released by almost all cell types, including cancer cells. The EV cargo, which consists of RNAs, proteins, DNA, and lipids, directly mirrors the cells of origin. EVs can be recovered from several body fluids, including blood, cerebral spinal fluid (CSF), saliva, and Broncho-Alveolar Lavage Fluid (BALF), by non-invasive or minimally invasive approaches, and are therefore proposed as feasible cancer diagnostic tools. In this review, methodologies for EV isolation and characterization and their impact as diagnostics for the central nervous system, head and neck, lung, and gastrointestinal cancers are outlined. For each of these tumours, recent data on the potential clinical applications of the EV’s unique cargo, alone or in combination with currently available tumour biomarkers, have been deeply discussed.

Liquid Biomarkers for Improved Diagnosis and Classification of CNS Tumors

Liquid biopsy, as a non-invasive technique for cancer diagnosis, has emerged as a major step forward in conquering tumors. Current practice in diagnosis of central nervous system (CNS) tumors involves invasive acquisition of tumor biopsy upon detection of tumor on neuroimaging. Liquid biopsy enables non-invasive, rapid, precise and, in particular, real-time cancer detection, prognosis and treatment monitoring, especially for CNS tumors. This approach can also uncover the heterogeneity of these tumors and will likely replace tissue biopsy in the future. Key components of liquid biopsy mainly include circulating tumor cells (CTC), circulating tumor nucleic acids (ctDNA, miRNA) and exosomes and samples can be obtained from the cerebrospinal fluid, plasma and serum of patients with CNS malignancies. This review covers current progress in application of liquid biopsies for diagnosis and monitoring of CNS malignancies.

Function of exosomes in neurological disorders and brain tumors

Exosomes are a subtype of extracellular vesicles released from different cell types including those in the nervous system, and are enriched in a variety of bioactive molecules such as RNAs, proteins and lipids. Numerous studies have indicated that exosomes play a critical role in many physiological and pathological activities by facilitating intercellular communication and modulating cells' responses to external environments. Particularly in the central nervous system, exosomes have been implicated to play a role in many neurological disorders such as abnormal neuronal development, neurodegenerative diseases, epilepsy, mental disorders, stroke, brain injury and brain cancer. Since exosomes recapitulate the characteristics of the parental cells and have the capacity to cross the blood-brain barrier, their cargo can serve as potential biomarkers for early diagnosis and clinical assessment of disease treatment. In this review, we describe the latest findings and current knowledge of the roles exosomes play in various neurological disorders and brain cancer, as well as their application as promising biomarkers. The potential use of exosomes to deliver therapeutic molecules to treat diseases of the central nervous system is also discussed.

An integrated workflow for biomarker development using microRNAs in extracellular vesicles for cancer precision medicine

EV-miRNAs are microRNA (miRNA) molecules encapsulated in extracellular vesicles (EVs), which play crucial roles in tumor pathogenesis, progression, and metastasis. Recent studies about EV-miRNAs have gained novel insights into cancer biology and have demonstrated a great potential to develop novel liquid biopsy assays for various applications. Notably, compared to conventional liquid biomarkers, EV-miRNAs are more advantageous in representing host-cell molecular architecture and exhibiting higher stability and specificity. Despite various available techniques for EV-miRNA separation, concentration, profiling, and data analysis, a standardized approach for EV-miRNA biomarker development is yet lacking. In this review, we performed a substantial literature review and distilled an integrated workflow encompassing important steps for EV-miRNA biomarker development, including sample collection and EV isolation, EV-miRNA extraction and quantification, high-throughput data preprocessing, biomarker prioritization and model construction, functional analysis, as well as validation. With the rapid growth of "big data", we highlight the importance of efficient mining of high-throughput data for the discovery of EV-miRNA biomarkers and integrating multiple independent datasets for in silico and experimental validations to increase the robustness and reproducibility. Furthermore, as an efficient strategy in systems biology, network inference provides insights into the regulatory mechanisms and can be used to select functionally important EV-miRNAs to refine the biomarker candidates. Despite the encouraging development in the field, a number of challenges still hinder the clinical translation. We finally summarize several common challenges in various biomarker studies and discuss potential opportunities emerging in the related fields.

Mechanisms of temozolomide resistance in glioblastoma - a comprehensive review

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and has an exceedingly low median overall survival of only 15 months. Current standard-of-care for GBM consists of gross total surgical resection followed by radiation with concurrent and adjuvant chemotherapy. Temozolomide (TMZ) is the first-choice chemotherapeutic agent in GBM; however, the development of resistance to TMZ often becomes the limiting factor in effective treatment. While O6-methylguanine-DNA methyltransferase repair activity and uniquely resistant populations of glioma stem cells are the most well-known contributors to TMZ resistance, many other molecular mechanisms have come to light in recent years. Key emerging mechanisms include the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. This review aims to provide a comprehensive overview of the clinically relevant molecular mechanisms and their extensive interconnections to better inform efforts to combat TMZ resistance.

Comprehensive In Silico Analysis of a Novel Serum Exosome-Derived Competitive Endogenous RNA Network for Constructing a Prognostic Model for Glioblastoma

Purpose

Glioblastoma (GBM) is one of the most aggressive brain tumors with high mortality, and tumor-derived exosomes provide new insight into the mechanisms of GBM tumorigenesis, metastasis and therapeutic resistance. We aimed to establish an exosome-derived competitive endogenous RNA (ceRNA) network for constructing a prognostic model for GBM.

Methods

We obtained the expression profiles of long noncoding RNAs (lncRNAs), miRNAs, and mRNAs from the GEO and TCGA databases and identified differentially expressed RNAs in GBM to construct a ceRNA network. By performing lasso and multivariate Cox regression analyses, we identified optimal prognosis-related differentially expressed lncRNAs (DElncRNAs) and generated a risk score model termed the exosomal lncRNA (exo-lncRNA) signature. The exo-lncRNA signature was subsequently validated in the CGGA GBM cohort. Finally, a novel prognostic nomogram was constructed based on the exo-lncRNA signature and clinicopathological parameters and validated in the CGGA external cohort. Based on the ceRNA hypothesis, oncocers were identified based on highly positive correlations between lncRNAs and mRNAs mediated by the same miRNAs. Furthermore, regression analyses were performed to assess correlations between the expression abundances of lncRNAs in tumors and exosomes.

Results

A total of 45 DElncRNAs, six DEmiRNAs, and 38 DEmRNAs were identified, and an exosome-derived ceRNA network was built. Three optimal prognostic-related DElncRNAs, HOTAIR (HR=0.341, P<0.001), SOX21-AS1 (HR=0.30, P<0.001), and STEAP3-AS1 (HR=2.47, P<0.001), were included to construct the exo-lncRNA signature, which was further proven to be an independent prognostic factor. The novel prognostic nomogram was constructed based on the exo-lncRNA signature, patient age, pharmacotherapy, radiotherapy, IDH mutation status, and MGMT promoter status, with a concordance index of 0.878. ROC and calibration plots both suggested that the nomogram had beneficial discrimination and predictive abilities. A total of 11 pairs of prognostic oncocers were identified. Regression analysis suggested excellent consistency of the expression abundance of the three exosomal lncRNAs between exosomes and tumor tissues.

Conclusions

Exosomal lncRNAs may serve as promising prognostic predictors and therapeutic targets. The prognostic nomogram based on the exo-lncRNA signature might provide an intuitive method for individualized survival prediction and facilitate better treatment strategies.

Epigenetics and Communication Mechanisms in Microglia Activation with a View on Technological Approaches

Microglial cells, the immune cells of the central nervous system (CNS), play a crucial role for the proper brain development and function and in CNS homeostasis. While in physiological conditions, microglia continuously check the state of brain parenchyma, in pathological conditions, microglia can show different activated phenotypes: In the early phases, microglia acquire the M2 phenotype, increasing phagocytosis and releasing neurotrophic and neuroprotective factors. In advanced phases, they acquire the M1 phenotype, becoming neurotoxic and contributing to neurodegeneration. Underlying this phenotypic change, there is a switch in the expression of specific microglial genes, in turn modulated by epigenetic changes, such as DNA methylation, histones post-translational modifications and activity of miRNAs. New roles are attributed to microglial cells, including specific communication with neurons, both through direct cell–cell contact and by release of many different molecules, either directly or indirectly, through extracellular vesicles. In this review, recent findings on the bidirectional interaction between neurons and microglia, in both physiological and pathological conditions, are highlighted, with a focus on the complex field of microglia immunomodulation through epigenetic mechanisms and/or released factors. In addition, advanced technologies used to study these mechanisms, such as microfluidic, 3D culture and in vivo imaging, are presented.

Single-step equipment-free extracellular vesicle concentration using super absorbent polymer beads

Extracellular vesicles (EVs) contain useful biomarkers for disease diagnosis and are promising biomaterials for the delivery of therapeutic molecules in vivo. Accordingly, an efficient concentration method is necessary for large-scale production or high-throughput isolation of EVs from bulk liquid samples, including culture medium and body fluids, to achieve their clinical application. However, current EV concentration methods, including ultrafiltration, are limited with respect to cost, efficiency, and centrifugation time. In this study, we developed the first single-step, equipment-free EV concentration method using super absorbent polymer (SAP) beads. SAP beads absorb small molecules, including water, via nano-sized channels but expel and thereby concentrate EVs. Consequently, the beads drastically enrich EVs by reducing the solution volume in a single step, without affecting EV characteristics. Moreover, the purity of the concentrated EV solution was high due to the absorption of protein impurities by SAP beads. To further demonstrate the versatility of the method, we showed that SAP beads successfully enrich EVs in human urine samples and culture medium, enabling better isolation performance than conventional ultrafiltration. We believe the newly developed approach and insight gained in this study will facilitate the use of EVs as prominent biomaterials for disease diagnosis and therapy.

miRNA-21 may serve as a promising noninvasive marker of glioma with a high diagnostic performance: a pooled analysis of 997 patients

Background:

Although various serum and tissue biomarkers have been investigated for glioma diagnosis, no gold standard has been identified. miRNA-21 was demonstrated to be a promising biomarker for the diagnosis of various brain tumors, whereas there remains uncertainty concerning whether miRNA-21 could be used as a good clinical diagnostic biomarker for glioma. The current meta-analysis aimed to evaluate the diagnostic accuracy of miRNA-21 as a potent biomarker in adults with suspected glioma.

Methods:

The Pubmed and Embase databases were searched systematically from inception to January 2020 to identify relevant research reports. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated. Summary receiver operating characteristic (SROC) curves were used to evaluate the overall diagnostic performance. Meta-regression and subgroup analyses were conducted to determine the source of heterogeneity and test the robustness of the results.

Results:

From 5394 citations with 997 subjects that met the inclusion criteria, 11 studies were selected. Summary estimates of the diagnostic performance of miRNA-21 were as follows: sensitivity, 0.83 [95% confidence interval (CI): 0.73–0.89]; specificity, 0.92 (95% CI: 0.85–0.96); PLR, 10.20 (95% CI: 5.10–20.30); NLR, 0.19 (95% CI: 0.12–0.31); and DOR, 54 (95% CI: 19–155). The area under the SROC curve was 0.94 (95% CI: 0.92–0.96). Deeks’s funnel plot revealed no evidence of publication bias (p = 0.59). Meta-regression analysis suggested that study publication year could attribute to the heterogeneity. Subgroup analysis found miRNA-21 had a constant high diagnostic accuracy across different ethnicity, glioma grade, sample source, and study region.

Conclusion:

This meta-analysis demonstrated that miRNA-21 has high diagnostic performance and could serve as a promising noninvasive diagnostic marker for glioma. Further large prospective studies are needed to validate its diagnostic value and its prognostic significance and therapeutic effects.

Time to focus on circulating nucleic acids for diagnosis and monitoring of gliomas: A systematic review of their role as biomarkers

Gliomas are diffusely growing tumours arising from progenitors within the central nervous system. They encompass a range of different molecular types and subtypes, many of which have a well-defined profile of driver mutations, copy number changes and DNA methylation patterns. A majority of gliomas will require surgical intervention to relieve raised intracranial pressure and reduce tumour burden. A proportion of tumours, however, are located in neurologically sensitive areas and a biopsy poses a significant risk of a deficit. A majority of gliomas recur after surgery, and monitoring tumour burden of the recurrence is currently achieved by imaging. However, most imaging modalities have limitations in assessing tumour burden and infiltration into adjacent brain, and sometimes imaging is unable to discriminate between tumour recurrence and pseudo-progression. Liquid biopsies, obtained from body fluids such as cerebrospinal fluid or blood, contain circulating nucleic acids or extracellular vesicles containing tumour-derived components. The studies for this systematic review were selected according to PRISMA criteria, and suggest that the detection of circulating tumour-derived nucleic acids holds great promises as biomarker to aid diagnosis and prognostication by monitoring tumour progression, and thus can be considered a pathway towards personalized medicine.

Profiling of extracellular vesicles in oral cancer, from transcriptomics to proteomics

Oral cancers occurring in different subsites can have distinct etiologies' and are a significant problem worldwide. In general, the incidence of oral cancers has declined over the last decade due to improvements in modifiable risk factors (tobacco and alcohol consumption). However, recent data suggest that the incidence of squamous cell carcinomas in the oral tongue and oropharynx are increasing. Human papilloma virus (HPV) is an important risk factor for oropharyngeal cancer and is associated with better treatment responses when compared with HPV-unrelated oropharyngeal cancer. Regardless of the subsite, there are no clinically available biomarkers for the early detection of these cancers and many are detected at an advanced stage and are associated with poor 5-year survival rates. Tumor tissue and serial needle biopsies are used to diagnose and prognosticate oral cancers but have important limitations. Besides being invasive and physically painful, these types of biopsies offer a limited view of a complex tumor due to inter- and intra-tumoral heterogeneity and a dynamic tumor microenvironment. Liquid biopsies offer a promising and alternative way to measure disease in real-time. Extracellular vesicles (EVs) are small particles that are secreted by all cells types and can be readily isolated from a wide range of biofluids. EVs are structurally stable and can horizontally transfer bioactive molecules to distant sites throughout the body in concentrated forms that exceed what can be delivered in a soluble format. As EVs represent their cell of origin, biofluid derived EVs are heterogeneous and are comprised of a complex repertoire of host- and cancer-derived particles. This review article has focused on studies that have used transcriptomics and proteomics to explore the function and clinical significance of EVs in oral cavity and oropharyngeal cancers.

Extracellular Vesicles and Their Roles in Cancer Progression

Extracellular vesicles (EVs) produced by cancer cells function as a unique form of intercellular communication that can promote cell growth and survival, help shape the tumor microenvironment, and increase invasive and metastatic activity. There are two major classes of EVs, microvesicles (MVs) and exosomes, and they differ in how they are formed. MVs are generated by the outward budding and fission of the plasma membrane. On the other hand, exosomes are derived as multivesicular bodies (MVBs) fuse with the plasma membrane and release their contents. What makes EVs especially interesting is how they mediate their effects. Both MVs and exosomes have been shown to contain a wide-variety of bioactive cargo, including cell surface, cytosolic, and nuclear proteins, as well as RNA transcripts, micro-RNAs (miRNAs), and even fragments of DNA. EVs, and their associated cargo, can be transferred to other cancer cells, as well as to normal cell types, causing the recipient cells to undergo phenotypic changes that promote different aspects of cancer progression. These findings, combined with those demonstrating that the amounts and contents of EVs produced by cancer cells can vary depending on their cell of origin, stage of development, or response to therapies, have raised the exciting possibility that EVs can be used for diagnostic purposes. Moreover, the pharmaceutical community is aggressively pursuing the use of EVs as a potential drug delivery platform. Here, in this chapter, we will highlight what is currently known about how EVs are generated, how they impact cancer progression, and the different ways they are being exploited for clinical applications.

Extracellular Vesicles in Neurological Disorders

The role of extracellular vesicles (EVs) in the central nervous system, and in particular the brain, is a rapidly growing research area. Importantly, the role for EVs in the nervous system spans from early development through to old age, with EVs being associated with several different neurological disorders. To date, researchers have been studying the function of EVs in the nervous system in three major areas: (i) the role of EVs in promoting disease pathways, (ii) the ability of EVs to be used as a diagnostic tool to identify cellular changes in the nervous system, and (iii) the potential use of EVs as therapeutic tools for the delivery of biomolecules or drugs to the nervous system. In each of these settings the analysis and use of EVs performs a different function, highlighting the breadth of areas in which the EV field is applicable. A key aspect of EV biology is the ability of vesicles to cross biological barriers, in particular the blood brain barrier. This allows for the measurement of serum EVs that contain information about cells in the brain, or alternatively, allows for the delivery of biomolecules that are packaged within EVs for therapeutic use.

Role of Exosomes in the Progression, Diagnosis, and Treatment of Gliomas

Gliomas are the most common primary malignant brain tumors associated with a low survival rate. Even after surgery, radiotherapy, and chemotherapy, gliomas still have a poor prognosis. Extracellular vesicles are a heterogeneous group of cell-derived membranous structures. Exosomes are a type of extracellular vesicles, their size ranges from 30 nm to 100 nm. Recent studies have proved that glioma cells could release numerous exosomes; therefore, exosomes have gained increasing attention in glioma-related research.

Recent studies have confirmed the importance of extracellular vesicles, particularly exosomes, in the development of brain tumors, including gliomas. Exosomes mediate intercellular communication in the tumor microenvironment by transporting biomolecules (proteins, lipids, deoxyribonucleic acid, and ribonucleic acid); thereby playing a prominent role in tumor proliferation, differentiation, metastasis, and resistance to chemotherapy or radiation. Given their nanoscale size, exosomes can traverse the blood-brain barrier and promote tumor progression by modifying the tumor microenvironment. Based on their structural and functional characteristics, exosomes are demonstrating their value not only as diagnostic and prognostic markers, but also as tools in therapies specifically targeting glioma cells.

Therefore, exosomes are a promising therapeutic target for the diagnosis, prognosis, and treatment of malignant gliomas. More research will be needed before exosomes can be used in clinical applications. Here, we describe the exosomes, their morphology, and their roles in the diagnosis and progression of gliomas. In addition, we discuss the potential of exosomes as a therapeutic target/drug delivery system for patients with gliomas.

Diagnostic accuracy of cerebrospinal fluid and serum-isolated extracellular vesicles for glioblastoma: a systematic review and meta-analysis

BACKGROUND

Glioblastoma (GBM) is the most malignant brain cancer because there are no available biopsy-free methods for the diagnosis or the preoperative early detection. In this regard, the development of a non- or minimally invasive methods for early detection could increase the survival rate of GBM patients.

METHODS

The present study aimed to assess the diagnostic accuracy of extracellular vesicles (EVs) derived RNAs, isolated from patients' CSF or serum for GBM diagnosis. For this purpose, we searched all literature databases and performed a backward and forward reference checking procedure to retrieve appropriate studies. We conducted a meta-analysis on EVs derived biomarkers as well as sensitivity analysis and meta-regression.

RESULTS

We identified EVs-derived 24 RNAs, which can diagnose GBM. The analyzed pooled data showed 76% sensitivity, 80% specificity, and 0.85 AUC, for 16 biomarkers. Besides, the pooled PLR, NLR, and DOR were 3.7, 0.30, and 12, respectively. Subgroup analysis did not show a significant difference between serum and CSF.

CONCLUSIONS

According to the pooled sensitivity, specificity, and AUC for EVs derived biomarkers, we suggest that EVs-derived biomarkers might serve as a high potential and noninvasive diagnostic tool for GBM detection using serum and CSF samples.