Exosomal miRNAs as cancer biomarkers and therapeutic targets

Extracellular Vesicles in Cancer Metastasis: Potential as Therapeutic Targets and Materials

The vast majority of cancer-related deaths are due to metastasis of the primary tumor that develops years to decades after apparent cures. However, it is difficult to effectively prevent or treat cancer metastasis. Recent studies have shown that communication between cancer cells and surrounding cells enables cancer progression and metastasis. The comprehensive term "extracellular vesicles" (EVs) describes lipid bilayer vesicles that are secreted to outside cells; EVs are well-established mediators of cell-to-cell communication. EVs participate in cancer progression and metastasis by transferring bioactive molecules, such as proteins and RNAs, including microRNAs (miRNAs), between cancer and various cells in local and distant microenvironments. Clinically, EVs functioning as diagnostic biomarkers, therapeutic targets, or even as anticancer drug-delivery vehicles have been emphasized as a result of their unique biological and pathophysiological characteristics. The potential therapeutic effects of EVs in cancer treatment are rapidly emerging and represent a new and important area of research. This review focuses on the therapeutic potential of EVs and discusses their utility for the inhibition of cancer progression, including metastasis.

Tumor cells derived-exosomes as angiogenenic agents: possible therapeutic implications

Angiogenesis is a multistep process and various molecules are involved in regulating it. Extracellular vesicles are cell-derived particles, secreted from several types of cells and are known to mediate cell-to-cell communication. These vesicles contain different bio-molecules including nucleic acids, proteins, and lipids, which are transported between cells and regulate physiological and pathological conditions in the recipient cell. Exosomes, 30–150 nm extracellular vesicles, and their key roles in tumorigenesis via promoting angiogenesis are of great recent interest. In solid tumors, the suitable blood supply is the hallmark of their progression, growth, and metastasis, so it can be supported by angiogenesis. Tumor cells abundantly release exosomes containing different kinds of biomolecules such as angiogenic molecules that contribute to inducing angiogenesis. These exosomes can be trafficked between tumor cells or between tumor cells and endothelial cells. The protein and nucleic acid cargo of tumor derived-exosomes can deliver to endothelial cells mostly by endocytosis, and then induce angiogenesis. Tumor derived-exosomes can be used as biomarker for cancer diagnosis. Targeting exosome-induced angiogenesis may serve as a promising tool for cancer therapy. Taken together, tumor derived-exosomes are the major contributors in tumor angiogenesis and a supposed target for antiangiogenic therapies. However, further scrutiny is essential to investigate the function of exosomes in tumor angiogenesis and clinical relevance of targeting exosomes for suppressing angiogenesis.

miR-23a-3p-abundant small extracellular vesicles released from Gelma/nanoclay hydrogel for cartilage regeneration

Articular cartilage has limited self-regenerative capacity and the therapeutic methods for cartilage defects are still dissatisfactory in clinic. Recent studies showed that exosomes derived from mesenchymal stem cells promoted chondrogenesis by delivering bioactive substances to the recipient cells, indicating exosomes might be a novel method for repairing cartilage defect. Herein, we investigated the role and mechanism of human umbilical cord mesenchymal stem cells derived small extracellular vesicles (hUC-MSCs-sEVs) on cartilage regeneration. In vitro results showed that hUC-MSCs-sEVs promoted the migration, proliferation and differentiation of chondrocytes and human bone marrow mesenchymal stem cells (hBMSCs). MiRNA microarray showed that miR-23a-3p was the most highly expressed among the various miRNAs contained in hUC-MSCs-sEVs. Our data revealed that hUC-MSCs-sEVs promoted cartilage regeneration by transferring miR-23a-3p to suppress the level of PTEN and elevate expression of AKT. Moreover, we fabricated Gelatin methacrylate (Gelma)/nanoclay hydrogel (Gel-nano) for sustained release of sEVs, which was biocompatible and exhibited excellent mechanical property. In vivo results showed that hUC-MSCs-sEVs containing Gelma/nanoclay hydrogel (Gel-nano-sEVs) effectively promoted cartilage regeneration. These results indicated that Gel-nano-sEVs have a promising capacity to stimulate chondrogenesis and heal cartilage defects, and also provided valuable data for understanding the role and mechanism of hUC-MSCs-sEVs in cartilage regeneration.

Serum Exosomal MicroRNA-21, MicroRNA-126, and PTEN Are Novel Biomarkers for Diagnosis of Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a serious threat to public health. Based on clinical manifestations, ACS can be classified into unstable angina (UA) pectoris and acute myocardial infarction (AMI). The purpose of this study was to explore the possibility of using serum exosomal microRNA (miR)-126, miR-21, and phosphatase and tensin homolog (PTEN) expression levels as biomarkers of UA and AMI and to investigate whether these levels were positively correlated with the severity of coronary stenosis based on the Gensini score. Exosomes were isolated by ultracentrifugation from the serum of 34 patients with AMI, 31 patients with UA, and 22 healthy controls. The isolated exosomes were characterized by electron microscopy and particle size analysis; exosomal identity was further confirmed by western blotting using exosome-specific antibodies. Real-time quantitative polymerase chain reaction indicated that the serum exosomal levels of miR-126 and miR-21 were significantly higher in the patients with UA and AMI than in the healthy controls. Enzyme-linked immunosorbent assay showed that the serum exosomal PTEN levels were significantly higher in the UA and AMI groups than in the control group. Receiving operating characteristic curve analysis demonstrated the diagnostic efficiency of serum exosomal miR-126, miR-21, and PTEN levels for predicting AMI and UA. In addition, the circulating exosomal miR-126 level was positively correlated with the severity of coronary artery stenosis in patients with UA and AMI based on the Gensini score.

Deep-Sequencing Identification of MicroRNA Biomarkers in Serum Exosomes for Early Pig Pregnancy

Early pregnancy diagnosis in sows can significantly improve the efficiency of pig industry. Exosomes are membrane-covered nanovesicles that can transport microRNAs (miRNAs) and other molecular signals between cells. In other species, serum exosome-derived miRNAs can serve as good biomarkers of diseases and different physiological states, including pregnancy status. We hypothesized that circulating exosome-derived miRNAs might be used to differentiate the pregnancy status as early as several days after insemination in pigs. To test this hypothesis, we randomly assigned pigs for artificial insemination with fertile or dead semen (control group). Serum samples were obtained from pregnant pigs on days 9, 12, and 15 after insemination and from non-pregnant pigs on days 0, 9, 12, and 15 after insemination. Exosomes were isolated for RNA extraction. The exosomal RNA samples from pigs on day 9 of the estrus cycle and pregnancy were used for small-RNA sequencing. A total 321 miRNAs were identified in all samples. Twenty eight differentially abundant miRNAs were identified between the pregnant and control groups. miRNAs with | log2 (fold change)| > 2 from sequencing results were selected for validation by quantitative reverse-transcription-polymerase chain reaction (RT-qPCR) in larger samples. Finally two upregulated miRNAs (miR-92b-3p and miR-17-5p) in the pregnant groups (on days 9, 12, and 15 of pregnancy) were confirmed by RT-qPCR. In summary, we have successfully identified circulating exosomal miRNA profiles in the serum of pigs in early pregnancy. miR-92b-3p and miR-17-5p could be used as potential circulating biomarkers for early pregnancy diagnosis.

MicroRNA-421-3p-abundant small extracellular vesicles derived from M2 bone marrow-derived macrophages attenuate apoptosis and promote motor function recovery via inhibition of mTOR in spinal cord injury

Background

Spinal cord injury (SCI) has a very disabling central nervous system impact but currently lacks effective treatment. Bone marrow-derived macrophages (BMDMs) are recruited to the injured area after SCI and participate in the regulation of functional recovery with microglia. Previous studies have shown that M2 microglia-derived small extracellular vesicles (SEVs) have neuroprotective effects, but the effects of M2 BMDM-derived sEVs (M2 BMDM-sEVs) have not been reported in SCI treatment.

Results

In this study, we investigated the role of M2 BMDM-sEVs in vivo and in vitro for SCI treatment and its mechanism. Our results indicated that M2 BMDM-sEVs promoted functional recovery after SCI and reduced neuronal apoptosis in mice. In addition, M2 BMDM-sEVs targeted mammalian target of rapamycin (mTOR) to enhance the autophagy level of neurons and reduce apoptosis. MicroRNA-421-3P (miR-421-3p) can bind to the 3′ untranslated region (3′UTR) of mTOR. MiR-421-3p mimics significantly reduced the activity of luciferase-mTOR 3′UTR constructs and increased autophagy. At the same time, tail vein injection of inhibitors of SEVs (Inh-sEVs), which were prepared by treatment with an miR-421-3p inhibitor, showed diminished protective autophagy of neuronal cells in vivo.

Conclusions

In conclusion, M2 BMDM-sEVs inhibited the mTOR autophagy pathway by transmitting miR-421-3p, which reduced neuronal apoptosis and promoted functional recovery after SCI, suggesting that M2 BMDM-sEVs may be a potential therapy for SCI.

Exosomal miRNA-34 from cancer-associated fibroblasts inhibits growth and invasion of gastric cancer cells in vitro and in vivo

Gastric cancer (GC) is one of the most common malignancies worldwide manifesting high morbidity and mortality. Cancer-associated fibroblasts (CAFs), important components of the tumor microenvironment, are essential for tumorigenesis and progression. Exosomes secreted from CAFs have been reported as the critical molecule-vehicle in intercellular crosstalk. However, the precise mechanism underlying the effect of CAFs remains to be fully investigated. In this study, we aimed to determine the role of CAFs and their exosomes in the progression of GC and related mechanisms. The results revealed that miRNA-34 was downregulated in both GC fibroblasts (GCFs) and GC cell lines while the overexpression of miRNA-34 suppressed the proliferation, invasion, and motility of GC cell lines. Coculturing GC cells with miRNA-34-overexpressing GCFs led to the suppression of cancer progression. Also, exosomes derived from GCFs were taken up by GC cells in vitro and in vivo and exerted antitumor roles in GC. In addition, exosomal miRNA-34 inhibited GC cell proliferation and invasion in vitro and suppressed tumor growth in vivo. Furthermore, 16 genes were identified as potential downstream targeting genes of miRNA-34. Taken together, GCFs-derived exosomal miRNA-34 may be a promising targeting molecule for therapeutic strategies in GC.

MicroRNAs and Xenobiotic Toxicity: An Overview

The advent of new technologies has paved the rise of various chemicals that are being employed in industrial as well as consumer products. This leads to the accumulation of these xenobiotic compounds in the environment where they pose a serious threat to both target and non-target species. miRNAs are one of the key epigenetic mechanisms that have been associated with toxicity by modulating the gene expression post-transcriptionally. Here, we provide a comprehensive view on miRNA biogenesis, their mechanism of action and, their possible role in xenobiotic toxicity. Further, we review the recent in vitro and in vivo studies involved in xenobiotic exposure induced miRNA alterations and the mRNA-miRNA interactions. Finally, we address the challenges associated with the miRNAs in toxicological studies.

Circulating Exosomal miRNA as Diagnostic Biomarkers of Neurodegenerative Diseases

Neurodegenerative diseases (NDDs) are a group of diseases caused by chronic and progressive degeneration of neural tissue. The main pathological manifestations are neuronal degeneration and loss in the brain and/or spinal cord. Common NDDs include Alzheimer disease (AD), Parkinson disease (PD), Huntington disease (HD), and amyotrophic lateral sclerosis (ALS). The complicated pathological characteristics and different clinical manifestations of NDDs result in a lack of sensitive and efficient diagnostic methods. In addition, no sensitive biomarkers are available to monitor the course of NDDs, predict their prognosis, and monitor the therapeutic response. Despite extensive research in recent years, analysis of amyloid β (Aβ) and α-synuclein has failed to effectively improve NDD diagnosis. Although recent studies have indicated circulating miRNAs as promising diagnostic biomarkers of NDDs, the miRNA in the peripheral circulation is susceptible to interference by other components, making circulating miRNA results less consistent. Exosomes are small membrane vesicles with a diameter of approximately 30-100 nm that transport proteins, lipids, mRNA, and miRNA. Because recent studies have shown that exosomes have a double-membrane structure that can resist ribonuclease in the blood, giving exosomal miRNA high stability and making them resistant to degradation, they may become an ideal biomarker of circulating fluids. In this review, we discuss the applicability of circulating exosomal miRNAs as biomarkers, highlight the technical aspects of exosomal miRNA analysis, and review studies that have used circulating exosomal miRNAs as candidate diagnostic biomarkers of NDDs.

Comparability of the small RNA secretome across human biofluids concomitantly collected from healthy adults

Small extracellular vesicles (sEV) are nano-sized (40–150 nm), membrane-encapsulated vesicles that are released by essentially all cells into the extracellular space and function as intercellular signaling vectors through the horizontal transfer of biologic molecules, including microRNA (miRNA) and other small non-coding RNA (ncRNA), that can alter the phenotype of recipient cells. sEV are present in essentially all extracellular biofluids, including serum, urine and saliva, and offer a new avenue for discovery and development of novel biomarkers of various disease states and exposures. The objective of this study was to systematically interrogate similarities and differences between sEV ncRNA derived from saliva, serum and urine, as well as cell-free small ncRNA (cf-ncRNA) from serum. Saliva, urine and serum were concomitantly collected from 4 healthy donors to mitigate potential bias that can stem from interpersonal and temporal variability. sEV were isolated from each respective biofluid, along with cf-RNA from serum. sEV were isolated from the respective biofluids via differential ultracentrifugation with a 30% sucrose cushion to minimize protein contamination. Small RNA-sequencing was performed on each sample, and cluster analysis was performed based on ncRNA profiles. While some similarities existed in terms of sEV ncRNA cargo across biofluids, there are also notable differences in ncRNA class and ncRNA secretion, with sEV in each biofluid bearing a unique ncRNA profile, including major differences in composition by ncRNA class. We conclude that sEV ncRNA cargo varies according to biofluid, so thus should be carefully selected and interpreted when designing or contrasting translational or epidemiological studies.

Radiotherapy-induced overexpression of exosomal miRNA-378a-3p in cancer cells limits natural killer cells cytotoxicity

Aim: We here hypothesized that tumor-derived exosomal miRNA (TexomiR) released from irradiated tumors may play a role in the tumor cells escape to natural killer (NK) cells. Materials & methods: Our study included the use of different cancer cell lines, blood biopsies of xenograph mice model and patients treated with radiotherapy. Results: The irradiation of cancer cells promotes the TET2-mediated demethylation of miR-378 promoter, miR-378a-3p overexpression and its loading in exosomes, inducing the decrease of granzyme-B (GZMB) secretion by NK cells. An inverse correlation between TexomiR-378a-3p and GZMB was observed in murine and human blood samples. Conclusion: Our work identifies TexomiR-378a-3p as a molecular signature associated with the loss of NK cells cytotoxicity via the decrease of GZMB expression upon radiotherapy.

MicroRNA-181d-5p-Containing Exosomes Derived from CAFs Promote EMT by Regulating CDX2/HOXA5 in Breast Cancer

Recently, novel mechanisms underlying the pro-tumorigenic effects of cancer-associated fibroblasts (CAFs) have been identified in several cancers, including breast cancer. CAFs can secrete exosomes that are loaded with proteins, lipids, and RNAs to affect tumor microenvironment. Herein, we identify CAF-derived exosomes that can transfer miR-181d-5p to enhance the aggressiveness of breast cancer. Cancerous tissues and matched paracancerous tissues were surgically resected from 122 patients with breast cancer. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were employed to identify interaction between homeobox A5 (HOXA5) and caudal-related homeobox 2 (CDX2), as well as between CDX2 and miR-181d-5p, respectively. Human breast cancer Michigan Cancer Foundation-7 (MCF-7) cells were cocultured with CAF-derived exosomes. 5-Ethynyl-2'-deoxyuridine (EdU) assay, TUNEL staining, Transwell invasion assays, and scratch tests were carried out to evaluate MCF-7 cell functions. Nude mice bearing xenografted MCF-7 cells were injected with CAF-derived exosomes, and the tumor formation was evaluated. HOXA5 expressed at a poor level in breast cancer tissues, and its overexpression retarded MCF-7 cell proliferation, invasion, migration, and epithelial-mesenchymal transition (EMT) and facilitated its apoptosis in vitro. miR-181d-5p targets CDX2, a transcription factor binding to HOXA5 promoter. Coculture of CAFs and MCF-7 cells showed that CAFs prolonged proliferation and antagonized apoptosis of MCF-7 cells via release of exosomes. Coculture of MCF-7 cells and exosomes derived from CAFs identified miR-181d-5p as a mediator of the exosomal effects on MCF-7 cells, in part, via downregulation of CDX2 and HOXA5. CAF-derived exosomes containing miR-181d-5p promoted the tumor growth of nude mice bearing xenografted MCF-7 cells. In conclusion, exosomal miR-181d-5p plays a key role in CAF-mediated effects on tumor environment in breast cancer, likely via CDX2 and HOXA5.

MicroRNAs in Small Extracellular Vesicles Indicate Successful Embryo Implantation during Early Pregnancy

Synchronous communication between the developing embryo and the receptive endometrium is crucial for embryo implantation. Thus, uterine receptivity evaluation is vital in managing recurrent implantation failure (RIF). The potential roles of small extracellular vesicle (sEV) miRNAs in pregnancy have been widely studied. However, the systematic study of sEVs derived from endometrium and its cargos during the implantation stage have not yet been reported. In this study, we isolated endometrium-derived sEVs from the mouse endometrium on D2 (pre-receptive phase), D4 (receptive phase), and D5 (implantation) of pregnancy. Herein, we reveal that multivesicular bodies (MVBs) in the endometrium increase in number during the window of implantation (WOI). Moreover, our findings indicate that CD63, a well-known sEV marker, is expressed in the luminal and glandular epithelium of mouse endometrium. The sEV miRNA expression profiles indicated that miR-34c-5p, miR-210, miR-369-5p, miR-30b, and miR-582-5p are enriched during WOI. Further, we integrated the RIF’s database analysis results and found out that miR-34c-5p regulates growth arrest specific 1 (GAS1) for normal embryo implantation. Notably, miR-34c-5p is downregulated during implantation but upregulated in sEVs. An implication of this is the possibility that sEVs miR-34c-5p could be used to evaluate uterine states. In conclusion, these findings suggest that the endometrium derived-sEV miRNAs are potential biomarkers in determining the appropriate period for embryo implantation. This study also has several important implications for future practice, including therapy of infertility.

Progress in extracellular vesicle biology and their application in cancer medicine

Under the broader category of extracellular vesicles (EVs), exosomes are now well recognized for their contribution and potential for biomedical research. During the last ten years, numerous technologies for purification and characterization of EVs have been developed. This enhanced knowledge has resulted in the development of novel applications of EVs. This review is an attempt to capture the exponential growth observed in EV science in the last decade and discuss the future potential to improve our understanding of EVs, develop technologies to overcome current limitations, and advance their utility for human benefit, especially in cancer medicine.

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Emerging Technologies

Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease

Role of exosomes and exosomal microRNAs in cancer

A growing body of evidence indicates that exosomes play a critical role in the cell-cell communication process. Exosomes are biological nanoparticles with an average diameter of 30-100 nm in size and are produced by almost all cell types in the human body; however, cancer cells contain higher concentrations of exosomes than healthy cells. They are released into all body fluids and contain double-stranded DNA (originated from nucleus and mitochondria), a variety of RNA species, and specific protein biomarkers that can be utilized as cancer biomarkers and therapeutic targets, and lipids. Therefore, the specific exosomes secreted by tumor cells could be used to predict the existence of the presence of a tumor in cancer patients. This review summarizes the role of exosomes in cancer development and their potential utility in the clinic.

Single-step RT-qPCR for detection of extracellular vesicle microRNAs in vivo: a time- and cost-effective method

Emerging evidence suggests that extracellular vesicle (EV)-associated microRNAs (miRNAs) are a potential diagnostic tool for liquid biopsy in various human diseases. However, the experimental procedure for the detection of EV-associated miRNAs (EV-miRNAs) from body fluids is relatively complex and not cost-effective. Due to the limited amount of EVs and EV-RNAs, a column-based RNA purification, which is an expensive approach, is often used to detect EV-miRNAs via reverse transcription-quantitative real-time PCR (RT-qPCR). Here, we developed and validated a simple and cost-effective method (single-step RT-qPCR) in which we directly detect EV-miRNAs without RNA purification from the EVs. We validated this protocol using the EVs isolated from mouse broncho-alveolar lavage fluid (BALF) and serum. The obtained EVs were first lysed in the EV-lysis buffer, followed by RT-qPCR without isolation and purification of RNAs. We successfully detected the designated miRNAs from lysed EVs; 10⁶ to 10⁷ EVs were optimal to detect the EV-miRNAs using the single-step RT-qPCR. In our previously published work, using the conventional RT-qPCR method, we have reported that miR-142 and -223 are dramatically upregulated in both BALF and serum EVs after lung infection. Hence, we reassessed and confirmed the level of EV-miR-142/223 using the newly developed single-step RT-qPCR. Notably, inhibition of RNase activity in the lysed EVs remains crucial for the detection of EV-miRNAs. Moreover, repeated freeze-thaw cycling significantly interferes the EV-miRNA quantification. Collectively, the single-step RT-qPCR for the detection of EV-miRNAs in vivo will potentially provide a fast, accurate, and convenient way to quantify circulating and/or body fluid-derived EV-miRNAs. This method may potentially be applied to the diagnostic blood testing used in the medical centers or research laboratories.

MicroRNA-320a inhibits invasion and metastasis in osteosarcoma by targeting cytoplasmic polyadenylation element-binding protein 1

Osteosarcoma is a primary malignant bone tumor, which affects children, adolescents, and young adults commonly. MicroRNAs (miRNAs) have been proved to be dysregulated in different cancers, including osteosarcoma. Although miR‐320a has been implicated in many types of malignancies, little is known about the role of miR‐320a in osteosarcoma. In this study, we show that the overexpression of miR‐320a or knockdown of cytoplasmic polyadenylation element‐binding protein 1 (CPEB1) inhibited osteosarcoma cell migration and invasion. miR‐320a downregulates CPEB1 expression by directly targeting the CPEB1 3′‐UTR. Furthermore, CPEB1 reintroduction reversed the antiproliferation, antimigration, and antiinvasion roles of miR‐320a, indicating that miR‐320a might function as a tumor suppressor in osteosarcoma through CPEB1. In conclusion, our study demonstrates that miR‐320a plays a critical role in osteosarcoma progression and may provide a potential therapeutic target for osteosarcoma.

The biology function and biomedical applications of exosomes

The study of extracellular vesicles (EVs) has the potential to identify unknown cellular and molecular mechanisms in intercellular communication and in organ homeostasis and disease. Exosomes, with an average diameter of ~100 nanometers, are a subset of EVs. The biogenesis of exosomes involves their origin in endosomes, and subsequent interactions with other intracellular vesicles and organelles generate the final content of the exosomes. Their diverse constituents include nucleic acids, proteins, lipids, amino acids, and metabolites, which can reflect their cell of origin. In various diseases, exosomes offer a window into altered cellular or tissue states, and their detection in biological fluids potentially offers a multicomponent diagnostic readout. The efficient exchange of cellular components through exosomes can inform their applied use in designing exosome-based therapeutics.

Exosome-shuttled miR-216a-5p from hypoxic preconditioned mesenchymal stem cells repair traumatic spinal cord injury by shifting microglial M1/M2 polarization

Background

Spinal cord injury (SCI) can lead to severe motor and sensory dysfunction with high disability and mortality. In recent years, mesenchymal stem cell (MSC)-secreted nano-sized exosomes have shown great potential for promoting functional behavioral recovery following SCI. However, MSCs are usually exposed to normoxia in vitro, which differs greatly from the hypoxic micro-environment in vivo. Thus, the main purpose of this study was to determine whether exosomes derived from MSCs under hypoxia (HExos) exhibit greater effects on functional behavioral recovery than those under normoxia (Exos) following SCI in mice and to seek the underlying mechanism.

Methods

Electron microscope, nanoparticle tracking analysis (NTA), and western blot were applied to characterize differences between Exos and HExos group. A SCI model in vivo and a series of in vitro experiments were performed to compare the therapeutic effects between the two groups. Next, a miRNA microarray analysis was performed and a series of rescue experiments were conducted to verify the role of hypoxic exosomal miRNA in SCI. Western blot, luciferase activity, and RNA-ChIP were used to investigate the underlying mechanisms.

Results

Our results indicate that HExos promote functional behavioral recovery by shifting microglial polarization from M1 to M2 phenotype in vivo and in vitro. A miRNA array showed miR-216a-5p to be the most enriched in HExos and potentially involved in HExos-mediated microglial polarization. TLR4 was identified as the target downstream gene of miR-216a-5p and the miR-216a-5p/TLR4 axis was confirmed by a series of gain- and loss-of-function experiments. Finally, we found that TLR4/NF-κB/PI3K/AKT signaling cascades may be involved in the modulation of microglial polarization by hypoxic exosomal miR-216a-5p.

Conclusion

Hypoxia preconditioning represents a promising and effective approach to optimize the therapeutic actions of MSC-derived exosomes and a combination of MSC-derived exosomes and miRNAs may present a minimally invasive method for treating SCI.

Expression of Serum Exosomal miRNA 122 and Lipoprotein Levels in Dogs Naturally Infected by Leishmania infantum: A Preliminary Study

Simple Summary

The immunopathogenesis of leishmaniasis is not completely understood. Exosomes are extracellular vesicles produced by most eukaryotic cells, containing various molecular constituents with biological effects (e.g., proteins, peptides, RNA). They play an important role in cell-to-cell signaling. Recently, exosomal microRNA were demonstrated to be able to regulate gene expression and protein production in mammalian cells, serving as potential biomarkers of disease. The microRNA miR-122 is a biomarker of hepatic damage widely studied in mice in the course of Leishmania infection. Leishmania organisms can interfere with miR-122 production leading to a dysfunction in cholesterol metabolism ensuring its proliferation in the infected host. In this study, we suggest that such a phenomenon may also occur in dogs affected by Leishmania infection.

Abstract

Current knowledge on the role of exosomal microRNA (miRNA) in canine leishmaniasis (CL), with particular regards to the interaction between miR-122 and lipid alterations, is limited. The aim of this study was to isolate/characterize exosomes in canine serum and evaluate the expression of miR-122 in ten healthy and ten leishmaniotic dogs. Serum exosomes were isolated using a polymer-based kit, ExoQuick^® and characterized by flow cytometry and transmission electron microscopy, whereas miR-122-5p expression was evaluated by quantitative reverse-transcriptase polymerase chain reaction. A significant decreased expression of exosomal miR-122-5p, decreased serum levels of high-density lipoproteins, and increased serum levels of low-density lipoproteins were seen in leishmaniotic dogs when compared with healthy dogs. These results suggest that hepatic dysfunctions induced by the parasite interfere with lipoprotein status. The decreased expression of exosomal miR122 represents an additional effect of Leishmania infection in dogs as in people.

Extracellular vesicle-mediated delivery of miR-101 inhibits lung metastasis in osteosarcoma

Rationale: Extracellular vesicles (EVs) have emerged as novel mediators of cell-to-cell communication that are capable of the stable transfer of therapeutic microRNAs (miRNAs), and thus, EVs hold immense promise as a miRNA delivery system for cancer therapy. Additionally, as miRNA-containing EVs are secreted into circulation, miRNAs contained within plasma EVs may represent ideal biomarkers for diseases. The objective of this study was to characterize a potential tumor suppressor miRNA, miR-101, and explore the potential of miR-101 delivery via EVs for in vivo therapy of metastatic osteosarcoma as well as the potential value of plasma EV-packaged miR-101 (EV-miR-101) level for predicting osteosarcoma metastasis.

Methods: The relationship of miR-101 expression and osteosarcoma progression was investigated in osteosarcoma specimens by in situ hybridization (ISH), and the potential inhibitory effect of miR-101 was further investigated using in vivo models. Using prediction software analysis, the mechanism of action of miR-101 in osteosarcoma was explored using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting and dual-luciferase assay. Adipose tissue-derived mesenchymal stromal cells (AD-MSCs) were transduced with lentiviral particles to obtain miR-101-enriched EVs. A Transwell assay and lung metastasis models of osteosarcoma were used to observe the effect of miR-101-enriched EVs on osteosarcoma invasiveness and metastasis. Detection of plasma EV-miR-101 levels was carried out in osteosarcoma patients and healthy controls by qRT-PCR.

Results: miR-101 expression was markedly lower in metastatic osteosarcoma specimens compared to non-metastatic specimens. Significantly fewer metastatic lung nodules were formed by Saos-2 cells overexpressing miR-101 and SOSP-9607 cells overexpressing miR-101 injected into mice. With increased miR-101 expression, B cell lymphoma 6 (BCL6) mRNA and protein expression levels were reduced, and miR-101 was found to exert its effects by directly targeting BCL6. AD-MSCs were successfully engineered to secrete miR-101-enriched EVs. Once taken up by osteosarcoma cells, these EVs showed suppressive effects on cell invasion and migration in vitro, and systemic administration of these EVs effectively suppressed metastasis in vivo with no significant side effects. Finally, the EV-miR-101 level was lower in osteosarcoma patients than in healthy controls and even lower in osteosarcoma patients with metastasis than in those without metastasis.

Conclusion: Our data support the function of miR-101 as a tumor suppressor in osteosarcoma via downregulation of BCL6. AD-MSC derived miR-101-enriched EVs represent a potential innovative therapy for metastatic osteosarcoma. EV-miR-101 also represents a promising circulating biomarker of osteosarcoma metastasis.

Cervical Cancer Cells-Secreted Exosomal microRNA-221-3p Promotes Invasion, Migration and Angiogenesis of Microvascular Endothelial Cells in Cervical Cancer by Down-Regulating MAPK10 Expression

Purpose

Cervical cancer (CC) is recognized as a common cancer with a high risk worldwide. Exosomal microRNAs (miRNAs) have received attention for their increasing potentials in CC therapy. In this study, we identify the involvement of miR-221-3p in CC progression by affecting angiogenesis of microvascular endothelial cells (MVECs).

Methods

Microarray-based gene expression profiling was conducted to retrieve the differentially expressed genes in CC. The expression patterns of miR-221-3p were measured by RT-qPCR, while Western blot analysis and RT-qPCR were performed to determine the expression of MAPK10 in the CC tissues and cells, followed by verification of the interaction between miR-221-3p and MAPK10 using dual luciferase reporter gene assay. Then the effects of miR-221-3p and MAPK10 on cell activities were assessed through gain- and loss-of-function experiments in CC. Subsequently, the impact of exosomal miR-221-3p on MVEC proliferation, migration, invasion and angiogenesis was examined after exosomal isolation from CC cells and co-cultured with MVECs.

Results

Gene expression profile showed that MAPK10 might participate in CC with a low expression. Moreover, miR-221-3p was highly expressed and MAPK10 was poorly expressed in CC tissues and cells. It was observed that miR-221-3p targeted MAPK10. Depletion of miR-221-3p blocked the cell proliferation, invasion and migration in CC by up-regulating MAPK10. Moreover, CC cells-derived exosomes carrying miR-221-3p accelerated MVEC proliferation, invasion, migration and angiogenesis in CC by regulating MAPK10.

Conclusion

CC cells-derived exosomes harboring miR-221-3p enhanced MVEC angiogenesis in CC by decreasing MAPK10.

Extracellular vesicles as biomarkers and therapeutic targets for cancer

Extracellular vesicles (EVs) are small lipid membrane vesicles that are secreted from almost all kinds of cells into the extracellular space. EVs are widely accepted to be involved in various cellular processes; in particular, EVs derived from cancer cells have been reported to play important roles in modifying the tumor microenvironment and promoting tumor progression. In addition, EVs derived from cancer cells encapsulate various kinds of tumor-specific molecules, such as proteins and RNAs, which contribute to cancer malignancy. Therefore, the unveiling of the precise mechanism of intercellular communication via EVs in cancer patients will provide a novel strategy for cancer treatment. Furthermore, a focus on the contents of EVs could promote the use of EVs in body fluids as clinically useful diagnostic and prognostic biomarkers. In this review, we summarize the current research knowledge on EVs as biomarkers and therapeutic targets and discuss their potential clinical applications.

Isolation and Retrieval of Extracellular Vesicles for Liquid Biopsy of Malignant Ground-Glass Opacity

Extracellular vesicles (EVs) are cell-released vesicles of submicrometer size. EVs contain a tissue-specific signature wherein a variety of proteins and nucleic acids are selectively packaged. Recent studies validate that EVs can be used for cancer diagnostics, staging, and treatment monitoring. EV-related clinical translation requires effective EV isolation as a prerequisite. However, lengthy procedures, low yield, low throughput, and high levels of contaminants disqualify the existing isolation approaches for large-scale clinical use. Hence, new approaches for rapid, efficient, and low-cost isolation of EVs in high purity for flexible analyses of the diverse contents in real-world clinical settings are highly desired yet are currently unavailable. Here, we report the effective use of heparin/polymer-coated microspheres (HPM) for EV isolation and retrieval. Approximately 81% of EVs can be isolated from plasma in 1 h with depletion of ∼99.5% plasma protein and nucleic acid contaminants, and 72% of isolated EVs can be retrieved with saline in 5 min for various cargo analyses. This approach was further validated with clinical samples derived from patients with malignant ground-glass opacity (GGO). In eight patients, the mutation concordance between EV DNA and tissue DNA is 39.8%. The prevalence and mutation count of EGFR, TP53, and NF1 are higher than those of other oncogenes and antioncogenes that are intensely associated with lung adenocarcinoma. Moreover, different mutation prevalence and patterns between smokers and nonsmokers can be observed. Our findings suggest that the combination of HPM assay and targeted sequencing of EV DNA could be translated in the differential diagnosis of malignant GGO with short turnaround time.

Genetic Pathways of Aging and Their Relevance in the Dog as a Natural Model of Human Aging

Aging research has experienced a burst of scientific efforts in the last decades as the growing ratio of elderly people has begun to pose an increased burden on the healthcare and pension systems of developed countries. Although many breakthroughs have been reported in understanding the cellular mechanisms of aging, the intrinsic and extrinsic factors that contribute to senescence on higher biological levels are still barely understood. The dog, Canis familiaris, has already served as a valuable model of human physiology and disease. The possible role the dog could play in aging research is still an open question, although utilization of dogs may hold great promises as they naturally develop age-related cognitive decline, with behavioral and histological characteristics very similar to those of humans. In this regard, family dogs may possess unmatched potentials as models for investigations on the complex interactions between environmental, behavioral, and genetic factors that determine the course of aging. In this review, we summarize the known genetic pathways in aging and their relevance in dogs, putting emphasis on the yet barely described nature of certain aging pathways in canines. Reasons for highlighting the dog as a future aging and gerontology model are also discussed, ranging from its unique evolutionary path shared with humans, its social skills, and the fact that family dogs live together with their owners, and are being exposed to the same environmental effects.

RAB27B-activated secretion of stem-like tumor exosomes delivers the biomarker microRNA-146a-5p, which promotes tumorigenesis and associates with an immunosuppressive tumor microenvironment in colorectal cancer

The dynamic cell-cell communication is essential for tissue homeostasis in normal physiological circumstances and contributes to a diversified tumor microenvironment. Although exosomes are extracellular vesicles that actively participate in cell-cell interaction by shutting cellular components, impacts of tumor exosomes in the context of cancer stemness remain elusive. Here, we expand colorectal cancer stem cells (CRCSCs) as cancer spheroids and demonstrate that the β-catenin/Tcf-4-activated RAB27B expression is required for the secretion of CRCSC exosomes. In an exosomal RNA sequencing analysis, a switch of exosomal RNA species from retrotransposons to microRNAs (miRNAs) is identified upon expanding CRCSCs. miRNA-146a-5p (miR-146a) is the major miRNA in CRCSC exosomes and exosomal miR-146a promotes stem-like properties and tumorigenicity by targeting Numb in recipient CRC cells. Among 53 CRC patients, those with abundant exosomal miR-146a expression in serum exhibits higher miR-146aHigh /NumbLow CRCSC traits, an increased number of tumor-filtrating CD66(+) neutrophils and a decreased number of tumor-infiltrating CD8(+) T cells. Our study elucidates a unique mechanism of tumor exosome-mediated stemness expansion.

Sound wave activated nano-sieve (SWANS) for enrichment of nanoparticles

Acoustic actuation is widely used in microfluidic systems as a method of controlling the behaviour of suspended matter. When acoustic waves impinge on particles, a radiation force is exerted which can cause migration over multiple acoustic time periods; in addition the scattering of the wave by the particle will affect the behaviour of nearby particles. This interparticle effect, or Bjerknes force, tends to attract particles together. Here, instead of manipulating a dilute sample of particles, we examine the acoustic excitation of a packed bed. We fill a microfluidic channel with microparticles, such that they form a closely packed structure and then excite them at the particle's resonant frequency. In this scenario, each particle acts as a source of scattered waves and we show that these waves are highly effective at attracting nanoparticles onto the surface of the microparticles, and nanoparticle collection characterises the performance of this mechanically activated packed bed.

Noncoding RNAs in Extracellular Fluids as Cancer Biomarkers: The New Frontier of Liquid Biopsies

The last two decades of cancer research have been devoted in two directions: (1) understanding the mechanism of carcinogenesis for an effective treatment, and (2) improving cancer prevention and screening for early detection of the disease. This last aspect has been developed, especially for certain types of cancers, thanks also to the introduction of new concepts such as liquid biopsies and precision medicine. In this context, there is a growing interest in the application of alternative and noninvasive methodologies to search for cancer biomarkers. The new frontiers of the research lead to a search for RNA molecules circulating in body fluids. Searching for biomarkers in extracellular body fluids represents a better option for patients because they are easier to access, less painful, and potentially more economical. Moreover, the possibility for these types of samples to be taken repeatedly, allows a better monitoring of the disease progression or treatment efficacy for a better intervention and dynamic treatment of the patient, which is the fundamental basis of personalized medicine. RNA molecules, freely circulating in body fluids or packed in microvesicles, have all the characteristics of the ideal biomarkers owing to their high stability under storage and handling conditions and being able to be sampled several times for monitoring. Moreover, as demonstrated for many cancers, their plasma/serum levels mirror those in the primary tumor. There are a large variety of RNA species noncoding for proteins that could be used as cancer biomarkers in liquid biopsies. Among them, the most studied are microRNAs, but recently the attention of the researcher has been also directed towards Piwi-interacting RNAs, circular RNAs, and other small noncoding RNAs. Another class of RNA species, the long noncoding RNAs, is larger than microRNAs and represents a very versatile and promising group of molecules which, apart from their use as biomarkers, have also a possible therapeutic role. In this review, we will give an overview of the most common noncoding RNA species detectable in extracellular fluids and will provide an update concerning the situation of the research on these molecules as cancer biomarkers.

miR-181c expression in neuroblastoma children and proliferation of neuroblastoma M17 cells

Expression level of miR-181c in neuroblastoma children and its effect on proliferation of neuroblastoma M17 cells were investigated. Fifty-seven neuroblastoma patients admitted to Weifang People's Hospital from January 2013 to December 2017 were selected and their cancer tissues and normal adjacent tissues were obtained. The expression level of miR-181c in the tissues of neuroblastoma patients was measured. The association of miR-181c expression level with the clinical and pathological features was analyzed. Neuroblastoma M17 cells were cultured in vitro, and cells were transfected and divided into miR-181c and blank groups. MTT assay was used to observe the proliferation of cells at 24, 48 and 72 h. The results of RT-qPCR detection showed that the expression level of miR-181c was significantly lower in neuroblastoma cancer tissues than that in adjacent tissues, with a statistically significant difference (t=18.570, P<0.001). The expression of miR-181c was not associated with sex (P=0.632), but associated with age, differentiation degree, lymph node metastasis, distant metastasis and the International Neuroblastoma Risk Group Staging System (INRGSS), with statistically significant differences (P<0.05). Following transfection of miR-181c into M17 cells, the results of MTT assay showed that there was no significant difference between the two groups in the proliferation of M17 cells at 24 h (P>0.05). After 48 h, differences between the two groups were recorded. Proliferation of M17 cells was significantly lower in the miR-181c group than that in the blank group, with a statistically significant difference (P<0.05). Age, differentiation degree, lymph node metastasis, distant metastasis, and INRGSS staging were independent risk factors for neuroblastoma (P<0.05). miR-181c has certain clinical significance in evaluating pathogenesis, early diagnosis and treatment of patients with neuroblastoma.

A MoS2-MWCNT based fluorometric nanosensor for exosome detection and quantification

Circulating exosomes in body fluids are involved in many diseases and have important roles in pathophysiological processes. Specifically, they have emerged as a promising new class of biomarkers in cancer diagnosis and prognosis because of their high concentration and availability in a variety of biological fluids. The ability to quantitatively detect and characterize these nano-sized vesicles is crucial to make use of exosomes as a reliable biomarker for clinical applications. However, current methods are mostly technically challenging and time-consuming which prevents them from being adopted in clinical practice. In this work, we have developed a rapid sensitive platform for exosome detection and quantification by employing MoS₂-multiwall carbon nanotubes as a fluorescence quenching material. This exosome biosensor shows a sensitive and selective biomarker detection. Using this MoS₂-MWCNT based fluorometric nanosensor to analyze exosomes derived from MCF-7 breast cancer cells, we found that CD63 expression could be measured based on the retrieved fluorescence of the fluorophore with a good linear response range of 0-15% v/v. In addition, this nanosensing technique is able to quantify exosomes with different surface biomarker expressions and has revealed that exosomes secreted from MCF-7 breast cancer cells have a higher CD24 expression compared to CD63 and CD81.

Analysis of circulating non-coding RNAs in a non-invasive and cost-effective manner

Non-coding RNAs (ncRNAs) participate in regulation of gene expression, and are highly relevant to pathological development. They are found to be stably present in diverse body fluids, including those in the circulatory system, which can be sampled non-invasively for clinical tests. Thus, circulating ncRNAs have great potential to be disease biomarkers. However, tremendous efforts are desired to discover and utilize ncRNAs as biomarkers in clinical diagnosis, calling for technological advancement in analysis of circulating ncRNAs in biospecimens. Hence, this review summarizes the recent developments in this area, highlighting the works devoted to cancer diagnosis and prognosis. Three main directions are focused: 1) Extraction and purification of ncRNAs from body fluids; 2) Quantification of the purified circulating ncRNAs; and 3) Microfluidic platforms for integration of both steps to enable point-of-care diagnostics. These technologies have laid a solid foundation to move forward the applications of circulating ncRNAs in disease diagnosis and cure.

Evaluation of circulating small extracellular vesicles derived miRNAs as biomarkers of early colon cancer: a comparison with plasma total miRNAs

Early diagnosis of colon cancer (CC) is clinically important, as it can significantly improve patients’ survival rate and quality of life. Although the potential role for small extracellular vesicles (sEVs) in early detection of many diseases has been repeatedly mentioned, systematic screening of plasma sEVs derived early CC specific biomarkers has not yet been reported. In this work, plasma sEVs enriched fractions were derived from 15 early-stage (TisN0M0) CC patients and 10 normal controls (NC). RNA sequencing identified a total number of 95 sEVs enriched fraction derived miRNAs with differential expression between CC and NC, most of which (60/95) was in well accordance with tissue results in the Cancer Genome Atlas (TCGA) dataset. Among those miRNAs, we selected let-7b-3p, miR-139-3p, miR-145-3p, and miR-150-3p for further validation in an independent cohort consisting of 134 participants (58 CC and 76 NC). In the validation cohort, the AUC of 4 individual miRNAs ranged from 0.680 to 0.792. A logistic model combining two miRNAs (i.e. let-7b-3p and miR-145-3p) achieved an AUC of 0.901. Adding the 3rd miRNA into this model can further increase the AUC to 0.927. Side by side comparison revealed that sEVs miRNA profile outperformed cell-free plasma miRNA in the diagnosis of early CC. In conclusion, we suggested that circulating sEVs enriched fractions have a distinct miRNA profile in CC patients, and sEVs derived miRNA could be used as a promising biomarker to detect CC at an early stage.

An ARF6-Exportin-5 axis delivers pre-miRNA cargo to tumour microvesicles

Tumor-derived microvesicles (TMVs) comprise a class of extracellular vesicles released from tumor cells that are now understood to facilitate communication between the tumor and the surrounding microenvironment. Despite their significance, the regulatory mechanisms governing the trafficking of bioactive cargos to TMVs at the cell surface remain poorly defined. Here we describe a molecular pathway for the delivery of microRNA (miRNA) cargo to nascent TMVs involving the dissociation of a pre-miRNA/Exportin-5 complex from Ran-GTP following nuclear export, and its subsequent transfer to a cytoplasmic shuttle comprised of ARF6-GTP and GRP1. As such, ARF6 activation increases pre-miRNA cargo contained within TMVs via a process that requires casein kinase 2-mediated phosphorylation of Ran-GAP1. Further, TMVs were found to contain pre-miRNA processing machinery including Dicer and Argonaute 2, which allow for cell-free pre-miRNA processing within shed vesicles. These findings offer cellular targets to block the loading and processing of pre-miRNAs within TMVs.

Circulating Exosomal miR-141-3p and miR-375 in Metastatic Progression of Rectal Cancer

As many as 30% to 40% of locally advanced rectal cancer (LARC) patients experience metastatic progression of the disease. Recognizing the potential of the genetic cargo in tumor-derived exosomes, we hypothesized that plasma exosomal microRNA (miRNA) may reflect biological aggressiveness in LARC and provide new markers for rectal cancer aggressiveness and risk stratification. In a prospective LARC cohort (NCT01816607), plasma samples were collected from 29 patients at the time of diagnosis, before neoadjuvant therapy and surgery. Exosomes, precipitated from plasma using a commercial kit, were verified by cryo-electron microscopy, nanoparticle tracking analysis, and western blotting. Expression of exosomal miRNAs was profiled using a miRCURY LNA miRNA microarray and validation of six miRNAs associated with pathological and clinical end-points was undertaken in plasma collected at the time of diagnosis from 64 patients in an independent prospective LARC cohort (NCT00278694). In both cohorts, exosomal miR-141-3p and miR-375 were higher in patients with synchronous liver metastasis than in those without (P = .010 and P = .017 respectively in the investigative cohort, and P < .001 for both in the validation cohort). Further, high exosomal miR-141-3p was associated with post-operative metastatic liver progression in the investigative cohort (P = .034). Because both miRNAs are associated with tumor angiogenesis and immune modulation, we propose that these miRNAs in circulating exosomes may reflect rectal cancer aggressiveness and accordingly be candidate biomarkers for further investigations.

Circulating miRNAs as non-invasive biomarkers to predict aggressive prostate cancer after radical prostatectomy

BACKGROUND

Prostate cancer is an extremely heterogeneous disease. Despite being clinically similar, some tumours are more likely to recur after surgery compared to others. Distinguishing those that need adjuvant or salvage radiotherapy will improve patient outcomes. The goal of this study was to identify circulating microRNA that could independently predict prostate cancer patient risk stratification after radical prostatectomy.

METHODS

Seventy-eight prostate cancer patients were recruited at the Odette Cancer Centre in Sunnybrook Health Sciences Centre. All patients had previously undergone radical prostatectomy. Blood samples were collected simultaneously for PSA testing and miRNA analysis using NanoString nCounter technology. Of the 78 samples, 75 had acceptable miRNA quantity and quality. Patients were stratified into high- and low-risk categories based on Gleason score, pathological T stage, surgical margin status, and diagnostic PSA: patients with Gleason ≥ 8; pT3a and positive margin; pT3b and any margin; or diagnostic PSA > 20 µg/mL were classified as high-risk (n = 44) and all other patients were classified as low-risk (n = 31).

RESULTS

Using our patient dataset, we identified a four-miRNA signature (miR-17, miR-20a, miR-20b, miR-106a) that can distinguish high- and low-risk patients, in addition to their pathological tumour stage. High expression of these miRNAs is associated with shorter time to biochemical recurrence in the TCGA dataset. These miRNAs confer an aggressive phenotype upon overexpression in vitro.

CONCLUSIONS

This proof-of-principle report highlights the potential of circulating miRNAs to independently predict risk stratification of prostate cancer patients after radical prostatectomy.

Glioma stem cells-derived exosomal miR-26a promotes angiogenesis of microvessel endothelial cells in glioma

BACKGROUND

Cancer stem cells (CSCs), which are involved in cancer initiation and metastasis, could potentially release exosomes that mediate cellular communication by delivering microRNAs (miRNAs). Based on the role of miR-26a in angiogenesis of glioma, our study was performed to investigate whether glioma stem cells (GSCs)-derived exosomes containing miR-26a could exert effects on angiogenesis of microvessel endothelial cells in glioma, in order to provide a new therapeutic RNA vehicle for glioma therapies.

METHODS

The expression of miR-26a and PTEN in glioma was quantified and the interaction among miR-26a, PTEN and PI3K/Akt signaling pathway was examined. Next, a series of gain- and loss-of function experiments were conducted to determine the role of miR-26a in angiogenesis of human brain microvascular endothelial cells (HBMECs). Subsequently, HBMECs were exposed to exosomes derived from GSCs with the gain-/loss-of-function of miR-26a. Finally, the effect of exosomal miR-26a on angiogenesis of HBMECs was assessed both in vitro and in vivo.

RESULTS

The results revealed that PTEN was down-regulated, while miR-26a was up-regulated in glioma. miR-26a activated the PI3K/Akt signaling pathway by targeting PTEN. Restored miR-26a promoted proliferation, migration, tube formation, and angiogenesis of HBMECs in vitro. In addition, GSCs-derived exosomes overexpressing miR-26a contributed to enhanced proliferation and angiogenesis of HBMECs in vitro through inhibition of PTEN. The angiogenic effects of GSCs-derived exosomes overexpressing miR-26a in vivo were consistent with the above-mentioned in vitro findings.

CONCLUSION

Collectively, our study demonstrates that GSCs-derived exosomal miR-26a promotes angiogenesis of HBMECs, highlighting an angiogenic role of miR-26a via exosomes.

Mechanism of exosomal microRNA-224 in development of hepatocellular carcinoma and its diagnostic and prognostic value

BACKGROUND

Exosomes contain proteins, lipids, and biological molecules such as DNA and RNA. Nucleic acids in exosomes are a group of molecules that can act as biomarkers. Currently, there are many reports on exosomal microRNAs, which are ideal biomarkers for the early diagnosis of cancer. However, there are few reports on the role of exosomal microRNAs in the diagnosis and prognosis of hepatocellular carcinoma (HCC).

AIM

To understand the mechanism of exosomal microRNA-224 (miR-224) in the development of HCC and evaluate its diagnostic and prognostic value.

METHODS

Cell culture and transfection of exosomal miRNA-224, real-time quantitative PCR, luciferase reporter assay, and other methods were used to find new biomarkers related to the development of HCC that can be used to diagnose HCC and predict HCC prognosis.

RESULTS

By targeting glycine N-methyltransferase, incubating exosomes with miR-224 mimic resulted in a significant increase in cell proliferation compared to that of the control group, while incubation with the miR-224 inhibitor significantly reduced cell proliferation. The same results were obtained for the cell invasion assay. Serum exosomal miR-224 did have some ability to differentiate patients with HCC from healthy controls, with an area under the curve of 0.910, and HCC patients with higher serum exosomal miR-224 expression had lower overall survival.

CONCLUSION

Exosomal miR-224 is a tumor promotor and can be a marker of diagnosis and prognosis of HCC patients, however, its ability to distinguish liver diseases needs further verification.

Extracellular Vesicle as a Source of Alzheimer's Biomarkers: Opportunities and Challenges

Alzheimer’s disease (AD) is a chronic progressive neurodegenerative disease characterized by memory decline and cognitive dysfunction. Although the primary causes of AD are not clear, it is widely accepted that the accumulation of amyloid beta (Aβ) and consecutive hyper-phosphorylation of tau, synaptic loss, oxidative stress and neuronal death might play a vital role in AD pathogenesis. Recently, it has been widely suggested that extracellular vesicles (EVs), which are released from virtually all cell types, are a mediator in regulating AD pathogenesis. Clinical evidence for the diagnostic performance of EV-associated biomarkers, particularly exosome biomarkers in the blood, is also emerging. In this review, we briefly introduce the biological function of EVs in the central nervous system and discuss the roles of EVs in AD pathogenesis. In particular, the roles of EVs associated with autophagy and lysosomal degradation systems in AD proteinopathy and in disease propagation are discussed. Next, we summarize candidates for biochemical AD biomarkers in EVs, including proteins and miRNAs. The accumulating data brings hope that the application of EVs will be helpful for early diagnostics and the identification of new therapeutic targets for AD. However, at the same time, there are several challenges in developing valid EV biomarkers. We highlight considerations for the development of AD biomarkers from circulating EVs, which includes the standardization of pre-analytical sources of variability, yield and purity of isolated EVs and quantification of EV biomarkers. The development of valid EV AD biomarkers may be facilitated by collaboration between investigators and the industry.

Review of the Isolation, Characterization, Biological Function, and Multifarious Therapeutic Approaches of Exosomes

Exosomes are extracellular vesicles that contain a specific composition of proteins, lipids, RNA, and DNA. They are derived from endocytic membranes and can transfer signals to recipient cells, thus mediating a novel mechanism of cell-to-cell communication. They are also thought to be involved in cellular waste disposal. Exosomes play significant roles in various biological functions, including the transfer of biomolecules such as RNA, proteins, enzymes, and lipids and the regulation of numerous physiological and pathological processes in various diseases. Because of these properties, they are considered to be promising biomarkers for the diagnosis and prognosis of various diseases and may contribute to the development of minimally invasive diagnostics and next generation therapies. The biocompatible nature of exosomes could enhance the stability and efficacy of imaging probes and therapeutics. Due to their potential use in clinical applications, exosomes have attracted much research attention on their roles in health and disease. To explore the use of exosomes in the biomedical arena, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are well-understood. Herein, we discuss the history, biogenesis, release, isolation, characterization, and biological functions of exosomes, as well as the factors influencing their biogenesis and their technical and biological challenges. We conclude this review with a discussion on the future perspectives of exosomes.

Extracellular vesicles as cancer liquid biopsies: from discovery, validation, to clinical application

Substantial research has been devoted to elucidate the roles that extracellular vesicles (EVs) play in the regulation of both normal and pathological processes, and multiple studies have demonstrated their potential as a source of cancer biomarkers. However, several factors have slowed the development of liquid biopsy EV biomarkers for cancer diagnosis, including logistical and technical difficulties associated with reproducibly obtaining highly purified EVs suitable for diagnostic analysis. Significant effort has focused on addressing these problems, and multiple groups have now reported EV analysis methods using liquid biopsies that have the potential for clinical translation. However, there are still important issues that must be addressed if these discoveries and technical advances are to be used for clinical translation of EV cancer biomarkers from liquid biopsies. To address these issues, this review focuses on the potential application of EV biomarkers for diagnosis of major cancer types, discussing approaches for EV biomarker discovery and verification, EV clinical assay development, analytical and clinical validation, clinical trials, regulatory submission, and end user utilization for the intended clinical application. This review also discusses key difficulties related to these steps, and recommendations for how to best accomplish steps in order to translate EV-based biomarkers into clinical settings.

Extracellular Vesicles from Thyroid Carcinoma: The New Frontier of Liquid Biopsy

The diagnostic approach to thyroid cancer is one of the most challenging issues in oncology of the endocrine system because of its high incidence (3.8% of all new cancer cases in the US) and the difficulty to distinguish benign from malignant non-functional thyroid nodules and establish the cervical lymph node involvement during staging. Routine diagnosis of thyroid nodules usually relies on a fine-needle aspirate biopsy, which is invasive and often inaccurate. Therefore, there is an urgent need to identify novel, accurate, and non-invasive diagnostic procedures. Liquid biopsy, as a non-invasive approach for the detection of diagnostic biomarkers for early tumor diagnosis, prognosis, and disease monitoring, may be of particular benefit in this context. Extracellular vesicles (EVs) are a consistent source of tumor-derived RNA due to their prevalence in circulating bodily fluids, the well-established isolation protocols, and the fact that RNA in phospholipid bilayer-enclosed vesicles is protected from blood-borne RNases. Recent results in other types of cancer, including our recent study on plasma EVs from glioblastoma patients suggest that information derived from analysis of EVs from peripheral blood plasma can be integrated in the routine diagnostic tumor approach. In this review, we will examine the diagnostic and prognostic potential of liquid biopsy to detect tumor-derived nucleic acids in circulating EVs from patients with thyroid carcinoma.

Tumor stem-like cell-derived exosomal RNAs prime neutrophils for facilitating tumorigenesis of colon cancer

Background

Cell-cell interactions maintain tissue homeostasis and contribute to dynamic alteration of the tumor microenvironment (TME). Communication between cancer and host cells not only promotes advanced disease aggression but also determines therapeutic response in cancer patients. Despite accumulating evidence supporting the role of tumor-infiltrating immunocytes in modulating tumor immunity, the interplay between heterogeneous tumor subpopulations and immunocytes is elusive.

Methods

We expanded colorectal cancer stem cells (CRCSCs) as cancer spheroids from the murine colorectal cancer (CRC) cell line CT26 to interrogate tumor-host interactions using a syngeneic tumor model. RNA-sequencing analysis of host cells and tumor exosomes was performed to identify molecular determinants that mediate the crosstalk between CRCSCs and immunocytes. The Cancer Genome Atlas (TCGA) database was used to validate the clinical significance in CRC patients.

Results

The expanded CT26 cancer spheroids showed increased stemness gene expression, enhanced spheroid and clonogenicity potential, and an elevated tumor-initiating ability, characteristic of CRCSCs. By examining immune cell composition in syngeneic tumor-bearing mice, a systemic increase in CD11b⁺/Ly6G^High/Ly6C^Low neutrophils was observed in mice bearing CRCSC-derived tumors. An increased secretion of CRCSC exosomes was observed in vitro, and through in vivo tracking, CRCSC exosomes were found to be transported to the bone marrow. Moreover, CRCSC exosomes prolonged the survival of bone marrow-derived neutrophils and engendered a protumoral phenotype in neutrophils. Mechanistically, tumor exosomal tri-phosphate RNAs induced the expression of interleukin-1β (IL-1β) through a pattern recognition-NF-κB signaling axis to sustain neutrophil survival. CRCSC-secreted CXCL1 and CXCL2 then attracted CRCSC-primed neutrophils to promote tumorigenesis of CRC cells via IL-1β. Moreover, neutrophil depletion using a Ly6G-specific antibody (clone 1A8) attenuated the tumorigenicity of CRCSCs. In human specimens, CRC patients exhibiting an active CRCSC signal (Snail⁺IL8⁺) showed elevated tumor infiltration of MPO⁺ neutrophils, and high (in the top 10%) MPO expression predicted poor survival of CRC patients.

Conclusions

This study elucidates a multistep CRCSC-neutrophil interaction during advanced cancer progression. Strategies targeting aberrant neutrophil activation may be developed for combating CSC-related malignancy.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0699-4) contains supplementary material, which is available to authorized users.

Balancing yield, purity and practicality: a modified differential ultracentrifugation protocol for efficient isolation of small extracellular vesicles from human serum

Ultracentrifugation remains the gold standard for isolation of small extracellular vesicles (sEV), particularly for cancer applications. The objective of this study was to determine if a widely used ultracentrifugation protocol for isolation of serum sEV could be modified to reduce the number of ultracentrifugation cycles and increase efficiency, while maintaining equal or better sample purity and yield. Serum was obtained from two healthy subjects. sEVs were isolated from 1 mL aliquots using three different ultracentrifugation protocols. Co-isolation of RNA carrier protein was assessed by performing Western blots for ApoA-I, ApoB, and Ago2. Small RNA-sequencing was performed on the sEV isolates, and differential detection of small ncRNA was compared across isolation protocols. Reduction from three- to two-ultracentrifuge cycles with no sucrose cushion resulted in a much higher sEV yield but also had the highest levels of lipoprotein and Ago2 contamination. However, the two-ultracentrifugation cycle protocol that incorporated a 30% sucrose cushion into the first cycle resulted in slightly higher sEV yields with lower levels of protein contamination compared to the lengthier three-ultracentrifugation cycle approach, therefore presenting a more efficient alternative approach for isolation of serum sEVs. It was also notable that there were some differences in sEV ncRNA cargo according to protocol, although it was less than expected given the differences in co-isolated RNA carrier proteins. Our results suggest that use of the modified serum sEV isolation protocol with two ultracentrifugation cycles and incorporating a 30% sucrose cushion offers a more efficient approach in terms of efficiency and purity.

An amplification-free electrochemical detection of exosomal miRNA-21 in serum samples

Recent evidence suggests that small non-coding RNAs such as microRNA (miRNA) encapsulated in exosomes represent an important mechanism of communication between the cells. Exosomal miRNAs play an important role in carcinogenesis via enhancing the cell to cell communication and targeting the cell growth molecular pathways which in turn facilitate metastasis in cancers. Despite progressive advances, the current methods for the exosomal miRNA detection mostly rely on labor-intensive sequencing approaches which are often prone to amplification bias and require costly and bulky equipment. Herein, we report an electrochemical approach for the detection of cancer-derived exosomal miRNAs in human serum samples by selectively isolating the target miRNA using magnetic beads pre-functionalized with capture probes and then directly adsorbing the targets onto a gold electrode surface. The level of adsorbed miRNA is detected electrochemically in the presence of an [Fe(CN)6]4-/3- redox system. This method enabled an excellent detection sensitivity of 1.0 pM with a relative standard deviation (%RSD) of <5.5% in cancer cells and serum samples (n = 8) collected from patients with colorectal adenocarcinoma (CRC). We believe that our approach could be useful in clinical settings for the quantification of exosomal miRNA in cancer patients.