Microvesicles Released from Human Renal Cancer Stem Cells Stimulate Angiogenesis and Formation of Lung Premetastatic Niche

Extracellular vesicles provide a capsid-free vector for oncolytic adenoviral DNA delivery

Extracellular vesicles (EVs) have been showcased as auspicious candidates for delivering therapeutic cargo, including oncolytic viruses for cancer treatment. Delivery of oncolytic viruses in EVs could provide considerable advantages, hiding the viruses from the immune system and providing alternative entry pathways into cancer cells. Here we describe the formation and viral cargo of EVs secreted by cancer cells infected with an oncolytic adenovirus (IEVs, infected cell-derived EVs) as a function of time after infection. IEVs were secreted already before the lytic release of virions and their structure resembled normally secreted EVs, suggesting that they were not just apoptotic fragments of infected cells. IEVs were able to carry the viral genome and induce infection in other cancer cells. As such, the role of EVs in the life cycle of adenoviruses may be an important part of a successful infection and may also be harnessed for cancer- and gene therapy.

Novel Aspects of Extracellular Vesicles in the Regulation of Renal Physiological and Pathophysiological Processes

Extracellular vesicles (EV) are nanosized particles released by a large variety of cells. They carry molecules such as proteins, RNA and lipids. While urinary EVs have been longer studied as a source of biomarkers for renal and non-renal disorders, research on EVs as regulatory players of renal physiological and pathological processes has experienced an outbreak recently in the past decade. In general, the microenvironment and (patho)physiological state of the donor cells affect the cargo of the EVs released, which then determines the effect of these EVs once they reach a target cell. For instance, EVs released by renal epithelial cells modulate the expression and function of water and solute transporting proteins in other cells. Also, EVs have been demonstrated to regulate renal organogenesis and blood flow. Furthermore, a dual role of EVs promoting, but also counteracting, disease has also been reported. EVs released by renal tubular cells can reach fibroblasts, monocytes, macrophages, T cells and natural killer cells, thus influencing the pathogenesis and progression of renal disorders like acute kidney injury and fibrosis, nephrolithiasis, renal transplant rejection and renal cancer, among others. On the contrary, EVs may also exert a cytoprotective role upon renal damage and promote recovery of renal function. In the current review, a systematic summary of the key studies from the past 5 years addressing the role of EVs in the modulation of renal physiological and pathophysiological processes is provided, highlighting open questions and discussing the potential of future research.

Extracellular Vesicles as Signaling Mediators and Disease Biomarkers across Biological Barriers

Extracellular vesicles act as shuttle vectors or signal transducers that can deliver specific biological information and have progressively emerged as key regulators of organized communities of cells within multicellular organisms in health and disease. Here, we survey the evolutionary origin, general characteristics, and biological significance of extracellular vesicles as mediators of intercellular signaling, discuss the various subtypes of extracellular vesicles thus far described and the principal methodological approaches to their study, and review the role of extracellular vesicles in tumorigenesis, immunity, non-synaptic neural communication, vascular-neural communication through the blood-brain barrier, renal pathophysiology, and embryo-fetal/maternal communication through the placenta.

Immunoregulatory Potential of Exosomes Derived from Cancer Stem Cells

Head and neck squamous cell carcinomas (HNSCCs) are malignancies that originate in the mucosal lining of the upper aerodigestive tract. Despite advances in therapeutic interventions, survival rates among HNSCC patients have remained static for years. Cancer stem cells (CSCs) are tumor-initiating cells that are highly resistant to treatment, and are hypothesized to contribute to a significant fraction of tumor recurrences. Consequently, further investigations of how CSCs mediate recurrence may provide insights into novel druggable targets. A key element of recurrence involves the tumor's ability to evade immunosurveillance. Recent published reports suggest that CSCs possess immunosuppressive properties, however, the underlying mechanism have yet to be fully elucidated. To date, most groups have focused on the role of CSC-derived secretory proteins, such as cytokines and growth factors. Here, we review the established immunoregulatory role of exosomes derived from mixed tumor cell populations, and propose further study of CSC-derived exosomes may be warranted. Such studies may yield novel insights into new druggable targets, or lay the foundation for future exosome-based diagnostics.

Exosomes as Mediators of Chemical-Induced Toxicity

PURPOSE OF REVIEW

This review provides information regarding how exosomes may contribute to environmental chemical-induced pathogenesis of chronic diseases. In connecting exosome biology to environmental toxicology and disease pathogenesis, we address vital questions regarding what constitutes exosomal cargo, how toxicants influence exosomal cargo, and how environmental stimuli influence exosomal physiological and pathological functions.

RECENT FINDINGS

Recent studies in the field demonstrate that exosomal cargo changes depending on external stimuli, which has consequences for the microenvironment of recipient cells. Based on recent findings, it is evident that exosomal cargo comprises various biological molecules including proteins, nucleic acids, and lipid molecules. Misfolded proteins and miRNA are examples of exosomal cargo molecules that can be altered by toxicants, ultimately changing the microenvironment of recipient cells in ways that are conducive to pathological processes. It will be crucial to map out the key signaling pathways that toxicants target to modulate exosomal cargo and their release.

Extracellular vesicles from human liver stem cells inhibit renal cancer stem cell-derived tumor growth in vitro and in vivo

Cancer stem cells (CSCs) are considered as responsible for initiation, maintenance and recurrence of solid tumors, thus representing the key for tumor eradication. The antitumor activity of extracellular vesicles (EVs) derived from different stem cell sources has been investigated with conflicting results. In our study, we evaluated, both in vitro and in vivo, the effect of EVs derived from human bone marrow mesenchymal stromal cells (MSCs) and from a population of human liver stem cells (HLSCs) of mesenchymal origin on renal CSCs. In vitro, both EV sources displayed pro‐apoptotic, anti‐proliferative and anti‐invasive effects on renal CSCs, but not on differentiated tumor cells. Pre‐treatment of renal CSCs with EVs, before subcutaneous injection in SCID mice, delayed tumor onset. We subsequently investigated the in vivo effect of MSC‐ and HLSC‐EVs systemic administration on progression of CSC‐generated renal tumors. Tumor bio‐distribution analysis identified intravenous treatment as best route of administration. HLSC‐EVs, but not MSC‐EVs, significantly impaired subcutaneous tumor growth by reducing tumor vascularization and inducing tumor cell apoptosis. Moreover, intravenous treatment with HLSC‐EVs improved metastasis‐free survival. In EV treated tumor explants, we observed both the transfer and the induction of miR‐145 and of miR‐200 family members. In transfected CSCs, the same miRNAs affected cell growth, invasion and survival. In conclusion, our results showed a specific antitumor effect of HLSC‐EVs on CSC‐derived renal tumors in vivo, possibly ascribed to the transfer and induction of specific antitumor miRNAs. Our study provides further evidence for a possible clinical application of stem cell‐EVs in tumor treatment.

What's new?

Stem cell‐derived extracellular vesicles (EVs) can reprogram target cells and promote tissue repair by transferring their cargo. However, the anti‐tumor activity of EVs derived from different stem cell sources has been investigated with conflicting results. Here, the authors demonstrate for the first time the anti‐tumor effect of EVs from human liver stem cells (HLSC‐EVs) in a systemic intravenous administration model. HLSC‐EVs had a selective effect on cancer stem cells that could be ascribed to the transfer and induction of anti‐tumor miRNAs. This study highlights the potential clinical use of stem cell‐derived EVs, alone or in combination with other cancer therapies.

Inhibiting WNT and NOTCH in renal cancer stem cells and the implications for human patients

Current treatments for clear cell renal cell cancer (ccRCC) are insufficient because two-thirds of patients with metastases progress within two years. Here we report the identification and characterization of a cancer stem cell (CSC) population in ccRCC. CSCs are quantitatively correlated with tumor aggressiveness and metastasis. Transcriptional profiling and single cell sequencing reveal that these CSCs exhibit an activation of WNT and NOTCH signaling. A significant obstacle to the development of rational treatments has been the discrepancy between model systems and the in vivo situation of patients. To address this, we use CSCs to establish non-adherent sphere cultures, 3D tumor organoids, and xenografts. Treatment with WNT and NOTCH inhibitors blocks the proliferation and self-renewal of CSCs in sphere cultures and organoids, and impairs tumor growth in patient-derived xenografts in mice. These findings suggest that our approach is a promising route towards the development of personalized treatments for individual patients.

Cancer stem cells are thought to be largely resistant to treatment and can be responsible for tumour recurrence. Here, using renal cancer organoids, self-renewing sphere cultures and PDX from patients, the authors show that the proliferation of stem cells within organoids, PDX and spheres can be blocked by the concomitant inhibition of the NOTCH and WNT pathways.

Exosomes derived from Piwil2‑induced cancer stem cells transform fibroblasts into cancer‑associated fibroblasts

Recently, several studies have demonstrated that cancer cell‑derived exosomes can facilitate tumor development and metastasis formation. However, the detailed function of exosomes released by cancer stem cells (CSCs) requires further investigation. The aim of the present study was to investigate the role of CSC‑derived exosomes in tumor development. For this purpose, Piwil2‑induced cancer stem cells (Piwil2‑iCSCs) were used as exosome‑generating cells, while fibroblasts (FBs) served as recipient cells. Exosomes were isolated by the ultracentrifugation of Piwil2‑iCSC‑conditioned medium and identified by transmission electron microscopy, nanoparticle tracking analysis and western blot analysis. To evaluate the effects of the exosomes on cell proliferation, migration and invasion, cell counting assay (CCK‑8), a wound healing assay and a Transwell assay were performed. Protein expression [matrix metalloproteinase (MMP)2, MMP9, α‑smooth muscle actin (α‑SMA) and vimentin and fibroblast‑activating protein (FAP)] was examined in FBs by western blot analysis. It was found that the Piwil2‑iCSC‑derived exosomes (Piwil2‑iCSC‑Exo) were oval or spherical, membrane‑coated vesicles with a uniform size (30‑100 nm in diameter). They are characterized by the surface expression of CD9, CD63, Hsp70 and Piwil2 proteins. Additional results from functional analyses revealed that Piwil2‑iCSC‑Exo enhanced the proliferative, migratory and invasive abilities of FBs, accompanied by the upregulated expression of MMP2 and MMP9. In addition, the increased expression of α‑SMA (P<0.05), vimentin (P<0.01 vs. control group, P<0.05 vs. PBS group) and FAP (P<0.001 vs. control group, P<0.01 vs. PBS group) following exposure to Piwil2‑iCSC‑Exo suggested that the exosomes induced FB transformation into cancer‑associated fibroblasts (CAFs). On the whole, the findings of this study demonstrate that Piwil2‑iCSC‑Exo induce the cancer‑associated phenotype in fibroblasts in vitro, suggesting that CSCs can promote tumor development through the modulation of the tumor microenvironment.

Targeting cancer stem cell pathways for cancer therapy

Since cancer stem cells (CSCs) were first identified in leukemia in 1994, they have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. The biological activities of CSCs are regulated by several pluripotent transcription factors, such as OCT4, Sox2, Nanog, KLF4, and MYC. In addition, many intracellular signaling pathways, such as Wnt, NF-κB (nuclear factor-κB), Notch, Hedgehog, JAK-STAT (Janus kinase/signal transducers and activators of transcription), PI3K/AKT/mTOR (phosphoinositide 3-kinase/AKT/mammalian target of rapamycin), TGF (transforming growth factor)/SMAD, and PPAR (peroxisome proliferator-activated receptor), as well as extracellular factors, such as vascular niches, hypoxia, tumor-associated macrophages, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, extracellular matrix, and exosomes, have been shown to be very important regulators of CSCs. Molecules, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) cells have been developed to specifically target CSCs, and some of these factors are already undergoing clinical trials. This review summarizes the characterization and identification of CSCs, depicts major factors and pathways that regulate CSC development, and discusses potential targeted therapy for CSCs.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Novel Cell-Free Therapy

In recent years, mesenchymal stem/stromal cells (MSCs) have widely been considered as therapeutic tools in basic researches and clinical trials. Accumulating evidence supports the idea that MSCs perform their therapeutic roles in paracrine manner especially through trophic factors and extracellular vesicles (EVs). Compared to cells, EVs have several advantages to be used as therapeutic agents, such as they lack self-replicating capabilities, dangers of ectopic differentiation, and tumor formation, genetic instability, and cellular rejection by the immune system. Since the MSC-derived EVs (MSC-EVs) appear to exert similar therapeutic effects of their parent cells, such as ability to arrive themselves to the site of injury and immunomodulatory properties, MSC-EVs have been widely studied in many animal models, including kidney, liver, cardiovascular, immunological, and neurological diseases. Regarding this, MSC-EVs look to be a novel and interesting approach to be studied in clinical trials of different inflammatory diseases. In this review, we summarize the properties and applications of MSC-EVs in different diseases.

A Comprehensive Picture of Extracellular Vesicles and Their Contents. Molecular Transfer to Cancer Cells

Critical processes such as growth, invasion, and metastasis of cancer cells are sustained via bidirectional cell-to-cell communication in tissue complex environments. Such communication involves the secretion of soluble factors by stromal cells and/or cancer cells within the tumor microenvironment (TME). Both stromal and cancer cells have been shown to export bilayer nanoparticles: encapsulated regulatory molecules that contribute to cell-to-cell communication. These nanoparticles are known as extracellular vesicles (EVs) being classified into exosomes, microvesicles, and apoptotic bodies. EVs carry a vast repertoire of molecules such as oncoproteins and oncopeptides, DNA fragments from parental to target cells, RNA species (mRNAs, microRNAs, and long non-coding RNA), and lipids, initiating phenotypic changes in TME. According to their specific cargo, EVs have crucial roles in several early and late processes associated with tumor development and metastasis. Emerging evidence suggests that EVs are being investigated for their implication in early cancer detection, monitoring cancer progression and chemotherapeutic response, and more relevant, the development of novel targeted therapeutics. In this study, we provide a comprehensive understanding of the biophysical properties and physiological functions of EVs, their implications in TME, and highlight the applicability of EVs for the development of cancer diagnostics and therapeutics.

Extracellular Vesicles and Cancer: A Focus on Metabolism, Cytokines, and Immunity

A better understanding of the mechanisms of cell communication between cancer cells and the tumor microenvironment is crucial to develop personalized therapies. It has been known for a while that cancer cells are metabolically distinct from other non-transformed cells. This metabolic phenotype is not peculiar to cancer cells but reflects the characteristics of the tumor microenvironment. Recently, it has been shown that extracellular vesicles are involved in the metabolic switch occurring in cancer and tumor-stroma cells. Moreover, in an immune system, the metabolic programs of different cell subsets are distinctly associated with their immunological function, and extracellular vesicles could be a key factor in the shift of cell fate modulating cancer immunity. Indeed, during tumor progression, tumor-associated immune cells and fibroblasts acquire a tumor-supportive and anti-inflammatory phenotype due to their interaction with tumor cells and several findings suggest a role of extracellular vesicles in this phenomenon. This review aims to collect all the available evidence so far obtained on the role of extracellular vesicles in the modulation of cell metabolism and immunity. Moreover, we discuss the possibility for extracellular vesicles of being involved in drug resistance mechanisms, cancer progression and metastasis by inducing immune-metabolic effects on surrounding cells.

Rho GTPases and related signaling complexes in cell migration and invasion

Cell migration and invasion play an important role in the development of cancer. Cell migration is associated with several specific actin filament-based structures, including lamellipodia, filopodia, invadopodia and blebs, and with cell-cell adhesion, cell-extracellular matrix adhesion. Migration occurs via different modes, human epithelial cancer cells mainly migrate collectively, while in vivo imaging studies in laboratory animals have found that most cells migrate as single cells. Rho GTPases play an important role in the process of cell migration, and several Rho GTPase-related signaling complexes are also involved. However, the exact mechanism by which these signaling complexes act remains unclear. This paper reviews how Rho GTPases and related signaling complexes interact with other proteins, how their expression is regulated, how tumor microenvironment-related factors play a role in invasion and metastasis, and the mechanism of these complex signaling networks in cell migration and invasion.

Parallels between wound healing, epimorphic regeneration and solid tumors

Striking similarities between wound healing, epimorphic regeneration and the progression of solid tumors have been uncovered by recent studies. In this Review, we discuss systemic effects of tumorigenesis that are now being appreciated in epimorphic regeneration, including genetic, cellular and metabolic heterogeneity, changes in circulating factors, and the complex roles of immune cells and immune modulation at systemic and local levels. We suggest that certain mechanisms enabling regeneration may be co-opted by cancer to promote growth at primary and metastatic sites. Finally, we advocate that working with a unified approach could complement research in both fields.

Cellular microparticles for tumor targeting delivery: from bench to bedside

This feature article summarizes the progress in leveraging microparticles for tumor targeting delivery, from bench to bedside.

Novel Techniques to Study the Bone-Tumor Microenvironment

Many cancers commonly metastasize to bone. After entering the bone, cancer cells can interact with surrounding stromal cells, which ultimately influences metastasis progression. Extracellular vesicles, direct cell contact and gap junctions, and cytokines are all mechanisms of intercellular communication that have been observed to occur in the bone microenvironment. These methods of cellular crosstalk can occur between cancer cells and a variety of stromal cells, with each interaction having a different impact on cancer progression. Communication between cancer cells and bone-resident cells has previously been implicated in processes such as cancer cell trafficking and arrest in bone, cancer cell dormancy, cancer cell reactivation, and proliferation. In this chapter we review innovative techniques and model systems that can be used to study bidirectional crosstalk between cancer cells and stromal cells in the bone, with an emphasis specifically on bone-metastatic breast cancer. Investigating how metastatic cancer cells interact with, and are influenced by, the bone microenvironment is crucial to better understanding of the progression of bone metastasis.

Preliminary evaluation of the diagnostic potential of Schistosoma japonicum extracellular vesicle proteins for Schistosomiasis japonica

Schistosomiasis is a chronic parasitic disease caused by the genus Schistosoma and poses a great threat to human and animal health. Identification of effective biomarkers would facilitate evaluation of drug efficacy and recognition of infected hosts, which are crucial for effective schistosomiasis control. Extracellular vesicle (EV) proteins are considered ideal biomarkers for developing invasive diagnostic tools. In this study, we evaluated the potential of Schistosoma japonicum EV (SjEV) proteins as biomarkers for diagnosing schistosomiasis. Several SjEV proteins were subject to epitope prediction using DNASTAR software, and the diagnostic potential of selected peptides was evaluated using enzyme-linked immunosorbent assay (ELISA). The results indicated that the sera showed detectable antibody levels against the two antigens in mice, rabbits, and humans infected with S. japonicum. Further analysis of the combined epitope protein demonstrated a modest sensitivity for detection of Schistosomiasis japonica. Our preliminary study suggests that S. japonicum EV proteins could serve as potential biomarkers for developing diagnostic tools for schistosomiasis.

The role of tumor-derived exosomes in tumor angiogenesis and tumor progression

Exosomes, belonging to the group of extracellular bodies, are released by healthy as well as cancerous cells and serve as a communication pathway. Tumor-derived exosomes (TEX) possess the capacity to reprogram the function of normal cells owing to their genetic and molecular cargo. Such exosomes target endothelial cells (among others) in the tumor microenvironment to promote angiogenesis. Blood supply is essential in solid tumor growth and metastasis. The potential of pro-angiogenic changes is enhanced by an increased amount of circulating tumor-derived exosomes in the body fluids of cancer patients. A vascular network is important, since the proliferation, as well as the metastatic spread of cancer cells depends on an adequate supply of oxygen and nutrients, and the removal of waste products. New blood vessels and lymphatic vessels are formed through processes called angiogenesis and lymphangiogenesis, respectively. Angiogenesis is regulated by both activator and inhibitor molecules. Thousands of patients have received anti-angiogenic therapy to date. Despite their theoretical efficacy, anti-angiogenic treatments have not proved beneficial in terms of long-term survival. Tumor-derived exosomes carrying pro-angiogenic factors might be a target for new anti-cancer therapy.

Exosomes in Cancer: Circulating Immune-Related Biomarkers

Exosomes, the smallest vesicles (30–100 nm) among multivesicular bodies, are released by all body cells including tumor cells. The cargo they transfer plays an important role in intercellular communication. Tumor-derived exosomes (TEXs) maintain interactions between cancer cells and the microenvironment. Emerging evidence suggests that tumor cells release a large number of exosomes, which may not only influence proximal tumor cells and stromal cells in the local microenvironment but can also exert systemic effects as they are circulating in the blood. TEXs have been shown to boost tumor growth promote progression and metastatic spread via suppression or modification of the immune response towards cancer cells, regulation of tumor neo-angiogenesis, pre-metastatic niche formation, and therapy resistance. In addition, recent studies in patients with cancer suggest that TEXs could serve as tumor biomarker reflecting partially the genetic and molecular content of the parent cancer cell (i.e., as a so-called “liquid biopsy”). Furthermore, recent studies have demonstrated that exosomes may have immunotherapeutic applications, or can act as a drug delivery system for targeted therapies with drugs and biomolecules.

Extracellular vesicles in urological malignancies: an update

Extracellular vesicles (EVs) have an essential functional role in local tumour progression, metastatic spread and the emergence of drug resistance in bladder, kidney and prostate cancer. Thus, EVs could be diagnostic, prognostic and predictive biomarkers for these malignancies. Virtually all biomolecules (including DNA, mRNA, microRNA, long non-coding RNA, proteins and lipids) packaged into EVs have been tested as biomarkers in blood and urine samples. The results are very heterogeneous, but promising biomarker candidates have been identified. Differing methods of EV isolation, characterization and analysis of their content have been used owing to a lack of international consensus; hence, comparing study results is challenging. Furthermore, validation of potential biomarkers in independent cohorts or prospective trials has rarely been performed. Future efforts to establish EV-derived biomarkers need to adequately address these points. In addition, emerging technologies such as mass spectroscopy and chip-based approaches can identify surface markers specific for cancer-associated EVs and will enable specific separation from blood and urine EVs, which probably will improve their performance as biomarkers. Moreover, EVs could be harnessed as therapeutic drug delivery vehicles for precise and effective anticancer therapy.

Decoding the Biology of Exosomes in Metastasis

Metastasis is the leading cause of cancer mortality. Cancer cells must adapt to colonize and thrive at the metastatic site. The modulation of the receptive organ microenvironment is a key event in the adaptation process and is partially accomplished at a distance by the primary tumor. Exosomes, a subclass of extracellular vesicles (EVs), are distal mediators of communication that carry genetic and molecular information to neighboring and distant cells. Cancer exosomes have been involved in restructuring metastatic sites to support cancer cell colonization. In this article, we discuss the role of exosomes in the metastatic process.

From Tumor Metastasis towards Cerebral Ischemia-Extracellular Vesicles as a General Concept of Intercellular Communication Processes

Extracellular vesicles (EVs) have been tremendous carriers in both experimental and translational science. These vesicles—formerly regarded as artifacts of in vitro research—have a heterogeneous population of vesicles derived from virtually all eukaryotic cells. EVs consist of a bilayer lipid structure with a diameter of about 30 to 1000 nm and have a characteristic protein and non-coding RNA content that make up different forms of EVs such as exosomes, microvesicles, and others. Despite recent progress in the EV field, which is known to serve as potential biomarkers and therapeutic tools under various pathological conditions, fundamental questions are yet to be answered. This short review focuses on recently reported data regarding EVs under pathological conditions with a particular emphasis on the role of EVs under such different conditions like tumor formation and cerebral ischemia. The review strives to point out general concepts of EV intercellular communication processes that might be vital to both diagnostic and therapeutic strategies in the long run.

NG2 as an Identity and Quality Marker of Mesenchymal Stem Cell Extracellular Vesicles

The therapeutic potential of mesenchymal stem cell (MSC) extracellular vesicles (EV) is currently under investigation in many pathological contexts. Both adult and perinatal MSC are being considered as sources of EV. Herein, we address antigen expression of cord blood and bone marrow MSC and released EV to define an identity and quality parameter of MSC EV as a medicinal product in the context of clinical applications. The research focuses on EV-shuttled neural/glial antigen 2 (NG2), which has previously been detected as a promising surface marker to distinguish perinatal versus adult MSC. Indeed, NG2 was significantly more abundant in cord blood than bone marrow MSC and MSC EV. Ultracentrifuge-isolated EV were then challenged for their pro-angiogenic properties on an xCELLigence system as quality control. NG2⁺ cord blood MSC EV, but not bone marrow MSC EV, promote bFGF and PDGF-AA proliferative effect on endothelial cells. Likewise, they successfully rescue angiostatin-induced endothelial cell growth arrest. In both cases, the effects are NG2-dependent. These results point at NG2 as an identity and quality parameter for cord blood MSC EV, paving the way for their clinical translation.

Exosomes: New insights into cancer mechanisms

Exosomes are mobile extracellular vesicles with a diameter 40 to 150 nm. They play a critical role in several processes such as the development of cancers, intercellular signaling, drug resistance mechanisms, and cell-to-cell communication by fusion onto the cell membrane of recipient cells. These vesicles contain endogenous proteins and both noncoding and coding RNAs (microRNA and messenger RNAs) that can be delivered to various types of cells. Furthermore, exosomes exist in body fluids such as plasma, cerebrospinal fluid, and urine. Therefore, they could be used as a novel carrier to deliver therapeutic nucleic-acid drugs for cancer therapy. It was recently documented that, hypoxia promotes exosomes secretion in different tumor types leading to the activation of vascular cells and angiogenesis. Cancer cell-derived exosomes (CCEs) have been used as prognostic and diagnostic markers in many types of cancers because exosomes are stable at 4°C and -70°C. CCEs have many functional roles in tumorigenesis, metastasis, and invasion. Consequently, this review presents the data about the therapeutic application of exosomes and the role of CCEs in cancer invasion, drug resistance, and metastasis.

Hepatocyte-derived exosomal MiR-194 activates PMVECs and promotes angiogenesis in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a serious vascular complication in the setting of liver disease. Factors produced by the liver are essential to regulate pulmonary angiogenesis in the pathogenesis of HPS; however, the pathogenic mechanisms of pulmonary angiogenesis are not fully understood. We investigated the role of HPS rat serum exosomes (HEs) and sham-operated rat serum exosomes (SEs) in the regulation of angiogenesis. We found that HEs significantly enhance PMVEC proliferation, migration, and tube formation. We further identified miR-194 was the most notably increased miRNA in HEs compared to SEs. Once released, hepatocyte-derived exosomal miR-194 was internalized by PMVECs, leading to the promotion of PMVEC proliferation, migration, and tube formation through direct targeting of THBS1, STAT1, and LIF. Importantly, the pathogenic role of exosomal miR-194 in initiating angiogenesis was reversed by P53 inhibition, exosome secretion inhibition or miR-194 inhibition. Additionally, high levels of miR-194 were found in serum exosomes and were positively correlated with P(A-a)O₂ in HPS patients and rats. Thus, our results highlight that the exosome/miR-194 axis plays a critical pathologic role in pulmonary angiogenesis, representing a new therapeutic target for HPS.

Identification of Serum Exosomal hsa-circ-0004771 as a Novel Diagnostic Biomarker of Colorectal Cancer

Background: Exosomal circular RNAs (circRNAs) in peripheral blood are considered as emerging diagnostic biomarkers of cancers. Owing to the lack of sensitive and specific biomarkers, a large number of colorectal cancer (CRC) patients were diagnosed in advanced stages leading to high mortality. This study aimed to identify circulating exosomal circRNAs as novel diagnostic biomarkers of CRC.

Materials and Methods: Candidate circRNA was selected by integrating analysis of Gene Expression Omnibus (GEO) database with online program GEO2R. A total of 170 patients and 45 healthy controls were enrolled to assess the diagnostic value of circRNAs for CRC. Exosomes isolated from the serum of participants and cell cultured media were confirmed by transmission electron microscope (TEM), Nanoparticle Tracking Analysis and western blot. The expression and the diagnostic utility of circRNA were tested by qRT-PCR and receiver operating characteristic (ROC) analysis, respectively.

Results: The circulating exosomal hsa-circ-0004771 with most abundant among the top ten differentially expressed circRNAs (fold change ≥1.5) was selected for further study based on the results of GEO dataset analysis. The up-regulated exosomal hsa-circ-0004771 was verified in serum of CRC patients compared to healthy controls (HCs) and patients with benign intestinal diseases (BIDs) by qRT-PCR. The area under the ROC curves (AUCs) of circulating exosomal hsa-circ-0004771 were 0.59 (95%CI, 0.457–0.725), 0.86 (95%CI, 0.785–0.933) and 0.88 (95%CI, 0.815–0.940) to differentiate BIDs, stage I/II CRC patients and CRC patients from HCs, respectively. The AUC was 0.816 (95%CI, 0.728–0.9) to differentiate stage I/II CRC patients from patients with BIDs. In addition, the elevated expression of exosomal hsa-circ-0004771 in the serum of CRC patients was tumor-derived. It was found that the expression of exosomal hsa-circ-0004771 was down-regulated expression of in the serum of postoperative CRC patients as well as cultured media of CRC cells treated with GW4869.

Conclusions: Circulating exosomal hsa-circ-0004771 was significantly up-regulated in CRC patients and served as a novel potential diagnostic biomarker of CRC.

Extracellular vesicles in urologic malignancies-Implementations for future cancer care

Extracellular vesicles (EVs), a heterogeneous group of vesicles differing in size and shape, cargo content and function, are membrane-bound and nano-sized vesicles that could be released by nearly all variations of cells. EVs have gained considerable attention in the past decades for their functions in modulating intercellular signalling and roles as potential pools for the novel diagnostic and prognostic biomarkers, as well as therapeutic targets in several cancers including urological neoplasms. In general, human and animal cells both can release distinct types of EVs, including exosomes, microvesicles, oncosomes and large oncosomes, and apoptotic bodies, while the content of EVs can be divided into proteins, lipids and nucleic acids. However, the lack of standard methods for isolation and detection platforms rein the widespread usage in clinical applications warranted furthermore investigations in the development of reliable, specific and sensitive isolation techniques. Whether and how the EVs work has become pertinent issues. With the aid of high-throughput proteomics or genomics methods, a fully understanding of contents contained in EVs from urogenital tumours, beyond all doubt, will improve our ability to identify the complex genomic alterations in the process of cancer and, in turn, contribute to detect potential therapeutic target and then provide personalization strategy for patient.

Niche origin of mesenchymal stem cells derived microvesicles determines opposing effects on NSCLC: Primary versus metastatic

Novel therapeutic approaches that address the malignant cells in their stroma microenvironment are urgently needed in lung cancer. The stroma resident mesenchymal stem cells (MSCs) interact with cancer cells in diverse ways including microvesicles (MVs) that transfer proteins and RNA species thereby modulating recipient cells' phenotype. Previously, we have demonstrated that MSCs' secretome from the primary non-small cell lung cancer (NSCLC) niche (lung) and metastatic niche (bone marrow (BM)) demonstrate opposite effects on NSCLC cells in a translation initiation (TI) dependent manner. Here, we examined the effect of MVs secreted from BM-MSCs' or lung-MSCs (healthy, NSCLC) to NSCLC phenotype. Briefly, NSCLC cell lines treated with Lung or BM-MSCs' MVs were assayed for viability (WST-1), cell count/death (trypan), migration (scratch), TI status and MAPKs activation (immunoblotting). Corresponding to previous published trends, Lung-MSCs' MVs promoted NSCLC cells' assayed traits whereas, BM-MSCs' MVs suppressed them. Activation of MAPKs and autophagy was registered in lung-MSCs MVs treated NSCLC cell lines only. Furthermore, lung-MSCs' MVs' treated NSCLC cells demonstrated an early (5min) activation of MAPKs and TI factors (peIF4E/peIF4GI) not evident in BM-MSCs MVs treated cells. These observations depict a role for MSCs'-MVs in NSCLC phenotype design and display distinct differences between the primary and metastatic niches that correspond to disease progression. In conclusion, the systemic nature of MVs marks them as attractive therapeutic markers/targets and we propose that identification of specific cargoes/signals that differentiate between MSCs MVs of primary and metastatic niches may introduce fresh therapeutic approaches.

Small Extracellular Vesicles Released from Ovarian Cancer Spheroids in Response to Cisplatin Promote the Pro-Tumorigenic Activity of Mesenchymal Stem Cells

Despite the different strategies used to treat ovarian cancer, around 70% of women/patients eventually fail to respond to the therapy. Cancer stem cells (CSCs) play a role in the treatment failure due to their chemoresistant properties. This capacity to resist chemotherapy allows CSCs to interact with different components of the tumor microenvironment, such as mesenchymal stem cells (MSCs), and thus contribute to tumorigenic processes. Although the participation of MSCs in tumor progression is well understood, it remains unclear how CSCs induce the pro-tumorigenic activity of MSCs in response to chemotherapy. Small extracellular vesicles, including exosomes, represent one possible way to modulate any type of cell. Therefore, in this study, we evaluate if small extracellular vesicle (sEV) derived from ovarian cancer spheroids (OCS), which are enriched in CSCs, can modify the activity of MSCs to a pro-tumorigenic phenotype. We show that sEV released by OCS in response to cisplatin induce an increase in the migration pattern of bone marrow MSCs (BM-MSCs) and the secretion interleukin-6 (IL-6), interleukin-8 (IL-8), and vascular endothelial growth factor A (VEGFA). Moreover, the factors secreted by BM-MSCs induce angiogenesis in endothelial cells and the migration of low-invasive ovarian cancer cells. These findings suggest that cisplatin could modulate the cargo of sEV released by CSCs, and these exosomes can further induce the pro-tumorigenic activity of MSCs.

Proteomic Profiling of Rhabdomyosarcoma-Derived Exosomes Yield Insights into Their Functional Role in Paracrine Signaling

Exosomes are important intercellular communication vehicles, secreted into body fluids by multiple cell types, including tumor cells. They have been demonstrated to contribute to the metastatic progression of tumor cells through paracrine signaling. Tumor exosomes contain intact and functional proteins, mRNA and miRNA that may alter the cellular environment to favor tumor growth. We evaluated the protein cargo of exosomes derived from the childhood tumor rhabdomyosarcoma (RMS) and the molecular pathways they are implicated in to decipher their role in the progression of this aggressive disease. We conducted a mass spectrometry analysis of exosome content isolated from five RMS cell lines: three of embryonal RMS (ERMS) and two of alveolar RMS (ARMS) histology and verified results by multiple reaction monitoring and western blot analyses. Results revealed 161 common proteins in ERMS-derived exosomes and 122 common proteins in ARMS-derived exosomes, of which 81 proteins were common to both subtypes. Using both PANTHER gene classification and Pathway Studio software, we assessed the perturbed biological processes and altered pathways in which the exosomal proteins are involved. The 81 commonly expressed proteins included those involved in "cell-signaling," "cell-movement," and "cancer." Pathways engaging the identified proteins revealed 37 common pathways including "integrin signaling pathway," "inflammation mediated by chemokine and cytokine signaling pathway," and "angiogenesis." Finally, a comparison of exosomal proteins of RMS cells with publicly available datasets from other cancer cells revealed that 36 proteins are specific and endogenous to the RMS-exosomes. Taken together, our results reveal that RMS-derived exosomes carry a protein cargo that contributes to conserved cellular signaling networks across multiple cell lines, and we also identify RMS exosome-specific proteins that should be further evaluated as possible novel biomarkers for this tumor.

Bone-marrow-derived cell-released extracellular vesicle miR-92a regulates hepatic pre-metastatic niche in lung cancer

Metastatic tumors have been shown to establish a supportive pre-metastatic niche (PMN) in distant organs, which in turn determines disseminated tumor cells' targeting of such organs. PMN is formed through the recruitment of bone-marrow-derived cells (BMDCs); however, the role of BMDCs in PMN formation is not fully understood. On the basis of RNA-seq data and bioinformatic analysis, secretion of extracellular vesicle (EV) miR-92a by BMDCs of lung cancer-bearing mice contributes to the establishment of liver PMN. Both BMDC-derived EVs and miR-92a mimics potentiate the activation of hepatic stellate cells (HSCs), subsequently increasing extracellular matrix (ECM) deposition in mice. Consequently, remodeling of the liver microenvironment enhanced immunosuppressive cell accumulation and cancer cell attachment. EVs miR-92a directly suppressed its target SMAD7, leading to the enhancement of transforming growth factor-β signaling in HSC. Elevated levels of circulating miR-92a are found in the sera of lung cancer patients, and EVs isolated from these patients have a similar ability to increase HSCs activation and ECM protein expression. Our study reveals the sequential steps of liver PMN formation in lung cancer, providing critical mediators that prepare PMN in the liver, and identifies new targets that offer valuable options for diagnosis and therapeutic intervention.

Observations on Solitary Versus Multiple Isolated Pancreatic Metastases of Renal Cell Carcinoma: Another Indication of a Seed and Soil Mechanism?

Isolated pancreas metastases are a rare type of metastasis of renal cell carcinoma, characterized by the presence of pancreatic metastases, while all other organs remain unaffected. In a previous study, we determined arguments from the literature which (a) indicate a systemic-haematogenic metastasis route (uniform distribution of the metastases across the pancreas and independence of the metastatic localization in the pancreas of the side of the renal carcinoma); and (b) postulate a high impact of a seed and soil mechanism (SSM) on isolated pancreatic metastasis of renal cell carcinoma (isPM) as an explanation for exclusive pancreatic metastases, despite a systemic haematogenous tumor cell embolization. The objective of the study presented was to search for further arguments in favor of an SSM with isPM. For that purpose, the factor's histology, grading, and singular/multiple pancreas metastases were analyzed on the basis of 814 observations published up to 2018. While histology and grading allowed for no conclusions regarding the importance of an SSM, the comparison of singular/multiple pancreas metastases produced arguments in favor of an SSM: 1. The multiple pancreas metastases observed in 38.1% prove that multiple tumor cell embolisms occur with isPM, the exclusive "maturation" of which in the pancreas requires an SSM; 2. The survival rates (SVR), which are consistent with singular and multiple pancreas metastases (despite the higher total tumor load with the latter), prove that the metastasized tumor cells are not able to survive in all other organs because of an SSM, which results in identical SVR when the pancreatic foci are treated adequately.

Circulating miRNA Profiling in Plasma Samples of Ovarian Cancer Patients

Ovarian cancer is one of the most common cancer types in women characterized by a high mortality rate due to lack of early diagnosis. Circulating miRNAs besides being important regulators of cancer development could be potential biomarkers to aid diagnosis. We performed the circulating miRNA expression analysis in plasma samples obtained from ovarian cancer patients stratified into FIGO I, FIGO III, and FIGO IV stages and from healthy females using the NanoString quantitative assay. Forty-five miRNAs were differentially expressed, out of these 17 miRNAs showed significantly different expression between controls and patients, 28 were expressed only in patients, among them 19 were expressed only in FIGO I patients. Differentially expressed miRNAs were ranked by the network-based analysis to assess their importance. Target genes of the differentially expressed miRNAs were identified then functional annotation of the target genes by the GO and KEGG-based enrichment analysis was carried out. A general and an ovary-specific protein–protein interaction network was constructed from target genes. Results of our network and the functional enrichment analysis suggest that besides HSP90AA1, MYC, SP1, BRCA1, RB1, CFTR, STAT3, E2F1, ERBB2, EZH2, and MET genes, additional genes which are enriched in cell cycle regulation, FOXO, TP53, PI-3AKT, AMPK, TGFβ, ERBB signaling pathways and in the regulation of gene expression, proliferation, cellular response to hypoxia, and negative regulation of the apoptotic process, the GO terms have central importance in ovarian cancer development. The aberrantly expressed miRNAs might be considered as potential biomarkers for the diagnosis of ovarian cancer after validation of these results in a larger cohort of ovarian cancer patients.

Intercellular Crosstalk Via Extracellular Vesicles in Tumor Milieu as Emerging Therapies for Cancer Progression

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Increasing evidence has suggested that extracellular vesicles (EV) mediated bidirectional transfer of functional molecules (such as proteins, different types of RNA, and lipids) between cancer cells and tumor stromal cells (immune cells, endothelial cells, fibroblasts, stem cells) and strongly contributed to the reinforcement of cancer progression. Thus, intercellular EV-mediated signaling in tumor microenvironment (TME) is essential in the modulation of all processes that support and promote tumor development like immune suppression, angiogenesis, invasion and metastasis, and resistance of tumor cells to anticancer treatments.

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Besides EV potential to revolutionize our understanding of the cancer cell-stromal cells crosstalk in TME, their ability to selectively transfer different cargos to recipient cells has created excitement in the field of tumortargeted delivery of specific molecules for anticancer treatments. Therefore, in tight connection with previous findings, this review brought insight into the dual role of EV in modulation of TME. Thus, on one side EV create a favorable phenotype of tumor stromal cells for tumor progression; however, as a future new class of anticancer drug delivery systems EV could re-educate the TME to overcome main supportive processes for malignancy progression.

Endoglin Trafficking/Exosomal Targeting in Liver Cells Depends on N-Glycosylation

Injury of the liver involves a wound healing partial reaction governed by hepatic stellate cells and portal fibroblasts. Individual members of the transforming growth factor-β (TGF-β) superfamily including TGF-β itself and bone morphogenetic proteins (BMP) exert diverse and partially opposing effects on pro-fibrogenic responses. Signaling by these ligands is mediated through binding to membrane integral receptors type I/type II. Binding and the outcome of signaling is critically modulated by Endoglin (Eng), a type III co-receptor. In order to learn more about trafficking of Eng in liver cells, we investigated the membranal subdomain localization of full-length (FL)-Eng. We could show that FL-Eng is enriched in Caveolin-1-containing sucrose gradient fractions. Since lipid rafts contribute to the pool of exosomes, we could consequently demonstrate for the first time that exosomes isolated from cultured primary hepatic stellate cells and its derivatives contain Eng. Moreover, via adenoviral overexpression, we demonstrate that all liver cells have the capacity to direct Eng to exosomes, irrespectively whether they express endogenous Eng or not. Finally, we demonstrate that block of N-glycosylation does not interfere with dimerization of the receptor, but abrogates the secretion of soluble Eng (sol-Eng) and prevents exosomal targeting of FL-Eng.

Pro-survival autophagy: An emerging candidate of tumor progression through maintaining hallmarks of cancer

Autophagy is an evolutionary conserved catabolic process that regulates the cellular homeostasis by targeting damaged cellular contents and organelles for lysosomal degradation and sustains genomic integrity, cellular metabolism, and cell survival during diverse stress and adverse conditions. Recently, the role of autophagy is extremely debated in the regulation of cancer initiation and progression. Although autophagy has a dichotomous role in the regulation of cancer, growing numbers of studies largely indicate the pro-survival role of autophagy in cancer progression and metastasis. In this review, we discuss the detailed mechanisms of autophagy, the role of pro-survival autophagy that positively drives several classical as well as emerging hallmarks of cancer for tumorigenic progression, and also we address various autophagy inhibitors that could be harnessed against pro-survival autophagy for effective cancer therapeutics. Finally, we highlight some outstanding problems that need to be deciphered extensively in the future to unravel the role of autophagy in tumor progression.

Salivary Extracellular Vesicle-Associated exRNA as Cancer Biomarker

Extracellular vesicles (EVs) secreted in biological fluids contain several transcripts of the cell of origin, which may modify the functions and phenotype of proximal and distant cells. Cancer-derived EVs may promote a favorable microenvironment for cancer growth and invasion by acting on stroma and endothelial cells and may favor metastasis formation. The transcripts contained in cancer EVs may be exploited as biomarkers. Protein and extracellular RNA (exRNA) profiling in patient bio-fluids, such as blood and urine, was performed to identify molecular features with potential diagnostic and prognostic values. EVs are concentrated in saliva, and salivary EVs are particularly enriched in exRNAs. Several studies were focused on salivary EVs for the detection of biomarkers either of non-oral or oral cancers. The present paper provides an overview of the available studies on the diagnostic potential of exRNA profiling in salivary EVs.

Exosomes and Their Role in Cancer Progression

Exosomes are a subset of extracellular vesicles and their size is approximately 100 nm in diameter. They are surrounded by a lipid bilayer membrane and secreted from almost all of cells. Exosomes are generated within the endocytic system as ILV (intraluminal membrane vesicle) and secreted during the fusion of MVB (multivesicular body) with the cell membrane. Recently it has been reported that exosomes modulate cell-cell communication contributing to the maintenance of tissue homeostasis by molecules including exosomes. Moreover, exosomes released from cancer cells are involved in cancer progression. Thus, data regarding the role of the exosomes in malignant cancer will lead to development of novel diagnostic and therapeutic methods.

Cancer Stem Cells: Concepts, Challenges, and Opportunities for Cancer Therapy

Cancer stem cells (CSCs) are a subpopulation of cancer cells with self-renewal capacity, that fuel tumor growth and contribute to the heterogeneous nature of tumors. First identified in hematological malignancies, CSC populations have to date been proposed in solid tumors in various organs. In vitro and in vivo assays, mouse genetic models, and more recently single-cell sequencing technologies and other '-omics' methodologies have not only facilitated the identification of novel CSC populations but also revealed and clarified novel properties of CSCs. Increasingly, both cell-autonomous and CSC niche factors are recognized as important contributors of CSC properties. The deepened understanding of CSC properties and characteristics would enable and facilitate the rational design of CSC-specific therapeutics that would, ideally, have high selectivity for cancer cells, eliminate tumor bulk, and prevent tumor recurrence. Addressing these issues would form some of the key challenges of the CSC research field in the coming years.

Involvement of Extracellular Vesicles in Vascular-Related Functions in Cancer Progression and Metastasis

The primary cause of mortality among patients with cancer is the progression of the tumor, better known as cancer invasion and metastasis. Cancer progression involves a series of biologically important steps in which the cross-talk between cancer cells and the cells in the surrounding environment is positioned as an important issue. Notably, angiogenesis is a key tumorigenic phenomenon for cancer progression. Cancer-related extracellular vesicles (EVs) commonly contribute to the modulation of a microenvironment favorable to cancer cells through their function of cell-to-cell communication. Vascular-related cells such as endothelial cells (ECs) and platelets activated by cancer cells and cancer-derived EVs develop procoagulant and proinflammatory statuses, which help excite the tumor environment, and play major roles in tumor progression, including in tumor extravasation, tumor cell microthrombi formation, platelet aggregation, and metastasis. In particular, cancer-derived EVs influence ECs, which then play multiple roles such as contributing to tumor angiogenesis, loss of endothelial vascular barrier by binding to ECs, and the subsequent endothelial-to-mesenchymal transition, i.e., extracellular matrix remodeling. Thus, cell-to-cell communication between cancer cells and ECs via EVs may be an important target for controlling cancer progression. This review describes the current knowledge regarding the involvement of EVs, especially exosomes derived from cancer cells, in EC-related cancer progression.

Extracellular vesicles in cancer - implications for future improvements in cancer care

The sustained growth, invasion, and metastasis of cancer cells depend upon bidirectional cell-cell communication within complex tissue environments. Such communication predominantly involves the secretion of soluble factors by cancer cells and/or stromal cells within the tumour microenvironment (TME), although these cell types have also been shown to export membrane-encapsulated particles containing regulatory molecules that contribute to cell-cell communication. These particles are known as extracellular vesicles (EVs) and include species of exosomes and shed microvesicles. EVs carry molecules such as oncoproteins and oncopeptides, RNA species (for example, microRNAs, mRNAs, and long non-coding RNAs), lipids, and DNA fragments from donor to recipient cells, initiating profound phenotypic changes in the TME. Emerging evidence suggests that EVs have crucial roles in cancer development, including pre-metastatic niche formation and metastasis. Cancer cells are now recognized to secrete more EVs than their nonmalignant counterparts, and these particles can be isolated from bodily fluids. Thus, EVs have strong potential as blood-based or urine-based biomarkers for the diagnosis, prognostication, and surveillance of cancer. In this Review, we discuss the biophysical properties and physiological functions of EVs, particularly their pro-metastatic effects, and highlight the utility of EVs for the development of cancer diagnostics and therapeutics.

Role of extracellular vesicles in stem cell biology

The extracellular vesicles (EVs) are membrane vesicles carrying proteins, nucleic acids, and bioactive lipids of the cell of origin. These vesicles released within the extracellular space and entering into the circulation may transfer their cargo to neighboring or distant cells and induce phenotypical and functional changes that may be relevant in several physiopathological conditions. In an attempt to define the biological properties of EVs, several investigations have focused on their cargo and on the effects elicited in recipient cells. EVs have been involved in modulation of tumor microenvironment and behavior, as well as in the immune and inflammatory response. In the present review, we address the paracrine action of EVs released by stem cells and their potential involvement in the activation of regenerative programs in injured cells.

Basics and applications of tumor-derived extracellular vesicles

Extracellular vesicle (EV)-mediated intercellular communication acts as a critical culprit in cancer development. The selective packaging of oncogenic molecules renders tumor-derived EVs capable of altering the tumor microenvironment and thereby modulating cancer developments that may contribute to drug resistance and cancer recurrence. Moreover, the molecular and functional characteristics of cancer through its development and posttreatment evolve over time. Tumor-derived EVs are profoundly involved in this process and can, therefore, provide valuable real-time information to reflect dynamic changes occurring within the body. Because they bear unique molecular profiles or signatures, tumor-derived EVs have been highlighted as valuable diagnostic and predictive biomarkers as well as novel therapeutic targets. In addition, the use of an advanced EV-based drug delivery system for cancer therapeutics has recently been emphasized in both basic and clinical studies. In this review, we highlight comprehensive aspects of tumor-derived EVs in oncogenic processes and their potential clinical applications.

Malignant ascites-derived exosomes promote peritoneal tumor cell dissemination and reveal a distinct miRNA signature in advanced gastric cancer

Peritoneal dissemination (PD) is the most frequent metastasis with poor prognosis in patients with advanced gastric cancer (GC). However, the molecular mechanisms of PD remain poorly defined. Exosomes play a pivotal role in cancer progression. Thus, this study aims to investigate the effects of malignant ascites (MA)-derived exosomes from GC patients on tumor cells and to elucidate the underlying mechanism. In vitro and in vivo analysis showed that compared to exosome-depleted supernatants, exosomes from MA of GC patients promoted invasion of AGS cells by up-regulation of Epithelial-mesenchymal transition (EMT) signaling. In a mouse abdominal xenograft model, the median survival was shorter after MA-derived exosomes treatment than the control group (35.5 days versus 67 days, p = 0.0005). Moreover, 29 exosomal miRNAs from ascites were identified by high throughput sequencing among 8 paired GC patients before and after peritoneal chemotherapy and 3 individuals with non-malignant disease. In summary, MA-derived exosomes from patients with GC promote EMT signaling in GC cells and in mouse peritoneal tumor model. Differential exosomal miRNAs might be targeted therapeutically for inhibiting peritoneal metastasis, which provides new insights for the molecular mechanisms of PD in GC.

Exosomal miRNA-107 induces myeloid-derived suppressor cell expansion in gastric cancer

  Background: Myeloid-derived suppressor cells (MDSCs) promote immunosuppression in the tumor microenvironment, support tumor growth and survival, and may contribute to immunotherapy resistance. Recent studies showed that tumor-derived exosomes (TDEs) can induce MDSCs accumulation and expansion, the mechanisms of which are largely unknown. Methods: The morphologies and sizes of the exosomes was observed by using a JEM-1400 transmission electron microscope. MicroRNA(miR)-107 and ARG1, DICER1, PTEN, PI3K, AKT, mTOR, and NF-kB mRNAs were quantified by quantitative reverse tanscription PCR. Dual-Luciferase Reports Assay were used to examine the expression of genes which was targeted by miR-107. The expression of proteins were analyzed by using western blot. Results: MiR-107 was not only overexpressed in gastric cancer cells but also enriched in their secreted TDEs. Also, these miR-107 enriched TDEs could be taken up by HLA-DR^-CD33⁺MDSCs, where miR-107 was able to target and suppress expression of DICER1 and PTEN genes. Dampened DICER1 expression supported expansion of MDSCs , while decreased PTEN led to activation of the PI3K pathway, resulting in increased ARG1 expression. Furthemore, gastric cancer-derived miR-107 TDEs, when dosed intravenously into mice, were also capable of inducing expansion of CD11b⁺Gr1^+/high MDSCs in mouse peripheral blood and altering expression of DICER1, PTEN, ARG1, and NOS2 in the MDSCs. Conclusions: Our findings demonstrate for the first time that gastric cancer-secreted exosomes are able to deliver miR-107 to the host MDSCs where they induce their expansion and activition by targeting DICER1 and PTEN genes, thereby may provide novel cancer therapeutics target for gastric cancer.

Exosomes in cancer development, metastasis, and immunity

Exosomes play essential roles in intercellular communications. The exosome was discovered in 1983, when it was found that reticulocytes release 50-nm small vesicles carrying transferrin receptors into the extracellular space. Since then, our understanding of the mechanism and function of the exosome has expanded exponentially that has transformed our perspective of inter-cellular exchanges and the molecular mechanisms that underlie disease progression. Cancer cells generally produce more exosomes than normal cells, and exosomes derived from cancer cells have a strong capacity to modify both local and distant microenvironments. In this review, we summarize the functions of exosomes in cancer development, metastasis, and anti-tumor or pro-tumor immunity, plus their application in cancer treatment and diagnosis/prognosis. Although the exosome field has rapidly advanced, we still do not fully understand the regulation and function of exosomes in detail and still face many challenges in their clinical application. Continued discoveries in this field will bring novel insights on intercellular communications involved in various biological functions and disease progression, thus empowering us to effectively tackle accompanying clinical challenges.

Microvesicles (MIVs) secreted from adipose-derived stem cells (ADSCs) contain multiple microRNAs and promote the migration and invasion of endothelial cells

Extracellular vesicles (EVs) such as microvesicles (MIVs) play an important role in intercellular communications. MIVs are small membrane vesicles sized 100–1000 nm in diameter that are released by many types of cells, such as mesenchymal stem cells (MSCs), tumor cells and adipose-derived stem cells (ADSC). As EVs can carry out autocrine and paracrine functions by controlling multiple cell processes, it is conceivable that EVs can be used as delivery vehicles for treating several clinical conditions, such as to improve cardiac angiogenesis after myocardial infarction (MI). Here, we seek to investigate whether ADSC-derived MIVs contain microRNAs that regulate angiogenesis and affect cell migration of endothelial cells. We first characterized the ADSC-derived MIVs and found that the MIVs had a size range of 100–300 nm, and expressed the MIV marker protein Alix. We then analyzed the microRNAs in ADSCs and ADSC-derived MIVs and demonstrated that ADSC-derived MIVs selectively released a panel of microRNAs, several of which were related to angiogenesis, including two members of the let-7 family. Furthermore, we demonstrated that ADSC-derived MIVs promoted the cell migration and invasion of the HUVEC endothelial cells. The PKH26-labeled ADSC-derived MIVs were effectively uptaken into the cytoplasm of HUVEC cells. Collectively, our results demonstrate that the ADSC-derived MIVs can promote migration and invasion abilities of endothelial cells, suggesting pro-angiogenetic potential. Future studies should focus on investigating the roles and mechanisms through which ADSC-derived MIVs regulate angiogenesis.

Mesenchymal stem cell exosomes: a two-edged sword in cancer therapy

Mesenchymal stem cells (MSCs) are multipotent stromal cells present in various adult tissues. Several studies suggest that MSCs secrete exosomes that perform as mediators in the tumor niche and play several roles in tumorigenesis, angiogenesis, and metastasis. In contrast, there are other studies supporting the tumor-suppressing effects of MSC-derived exosomes. Therefore, the exact association of MSC exosomes and tumor cells remains open to debate. This review aimed to demonstrate the present knowledge of MSC-derived exosomes in cancer research and to illustrate current approaches to make use of modified exosomes as a platform in therapeutic strategies in cancer.