Proteomics characterization of exosome cargo. Methods. 2015;87:75-82. [PMID: 25837312 DOI: 10.1016/j.ymeth.2015.03.018]

Exosomes, metastases, and the miracle of cancer stem cell markers

Cancer-initiating cells (CIC) are the driving force in tumor progression. There is strong evidence that CIC fulfill this task via exosomes (TEX), which modulate and reprogram stroma, nontransformed cells, and non-CIC. Characterization of CIC, besides others, builds on expression of CIC markers, many of which are known as metastasis-associated molecules. We here discuss that the linkage between CIC/CIC-TEX and metastasis-associated molecules is not fortuitously, but relies on the contribution of these markers to TEX biogenesis including loading and TEX target interactions. In addition, CIC markers contribute to TEX binding- and uptake-promoted activation of signaling cascades, transcription initiation, and translational control. Our point of view will be outlined for pancreas and colon CIC highly expressing CD44v6, Tspan8, EPCAM, claudin7, and LGR5, which distinctly but coordinately contribute to tumor progression. Despite overwhelming progress in unraveling the metastatic cascade and the multiple tasks taken over by CIC-TEX, there remains a considerable gap in linking CIC biomarkers, TEX, and TEX-initiated target modulation with metastasis. We will try to outline possible bridges, which could allow depicting pathways for new and expectedly powerful therapeutic interference with tumor progression.

Extracellular Vesicles: Delivery Vehicles of Myokines

Movement and regular physical activity are two important factors that help the human body prevent, reduce and treat different chronic diseases such as obesity, type 2 diabetes, heart diseases, hypertension, sarcopenia, cachexia and cancer. During exercise, several tissues release molecules into the blood stream, and are able to mediate beneficial effects throughout the whole body. In particular, contracting skeletal muscle cells have the capacity to communicate with other organs through the release of humoral factors that play an important role in the mechanisms of adaptation to physical exercise. These muscle-derived factors, today recognized as myokines, act as endocrine and paracrine hormones. Moreover, exercise may stimulate the release of small membranous vesicles into circulation, whose composition is influenced by the same exercise. Combining the two hypotheses, these molecules related to exercise, named exer-kines, might be secreted from muscle cells inside small vesicles (nanovesicles). These could act as messengers in tissue cross talk during physical exercise. Thanks to their ability to deliver useful molecules (such as proteins and miRNA) in both physiological and pathological conditions, extracellular vesicles can be thought of as promising candidates for potential therapeutic and diagnostic applications for several diseases.

Exosomes from mesenchymal stem/stromal cells: a new therapeutic paradigm

Mesenchymal stem/stromal cells (MSCs) have been demonstrated to hold great potential for the treatment of several diseases. Their therapeutic effects are largely mediated by paracrine factors including exosomes, which are nanometer-sized membrane-bound vesicles with functions as mediators of cell-cell communication. MSC-derived exosomes contain cytokines and growth factors, signaling lipids, mRNAs, and regulatory miRNAs. Increasing evidence suggests that MSC-derived exosomes might represent a novel cell-free therapy with compelling advantages over parent MSCs such as no risk of tumor formation and lower immunogenicity. This paper reviews the characteristics of MSC exosomes and their fate after in vivo administration, and highlights the therapeutic potential of MSC-derived exosomes in liver, kidney, cardiovascular and neurological disease. Particularly, we summarize the recent clinical trials performed to evaluate the safety and efficacy of MSC exosomes. Overall, this paper provides a general overview of MSC-exosomes as a new cell-free therapeutic paradigm.

Challenges and opportunities in exosome research-Perspectives from biology, engineering, and cancer therapy

Exosomes are small (∼30-140 nm) lipid bilayer-enclosed particles of endosomal origin. They are a subset of extracellular vesicles (EVs) that are secreted by most cell types. There has been growing interest in exosome research in the last decade due to their emerging role as intercellular messengers and their potential in disease diagnosis. Indeed, exosomes contain proteins, lipids, and RNAs that are specific to their cell origin and could deliver cargo to both nearby and distant cells. As a result, investigation of exosome cargo contents could offer opportunities for disease detection and treatment. Moreover, exosomes have been explored as natural drug delivery vehicles since they can travel safely in extracellular fluids and deliver cargo to destined cells with high specificity and efficiency. Despite significant efforts made in this relatively new field of research, progress has been held back by challenges such as inefficient separation methods, difficulties in characterization, and lack of specific biomarkers. In this review, we summarize the current knowledge in exosome biogenesis, their roles in disease progression, and therapeutic applications and opportunities in bioengineering. Furthermore, we highlight the established and emerging technological developments in exosome isolation and characterization. We aim to consider critical challenges in exosome research and provide directions for future studies.

Exosomes, new biomarkers in early cancer detection

Exosomes are endosomal-derived vesicles, playing a major role in cell-to-cell communication. Multiple cells secret these vesicles to induce and inhibit different cellular and molecular pathways. Cancer-derived exosomes have been shown to affect development of cancer in different stages and contribute to the recruitment and reprogramming of both proximal and distal tissues. The growing interest in defining the clinical relevance of these nano-sized particles in cancers, has led to the identification of either tissue- or disease-specific exosomal contents, such as nucleic acids, proteins and lipids as a source of new biomarkers which propose the diagnostic potentials of exosomes in early detection of cancers. In this review, we have discussed some aspects of exosomes including their contents, applications and isolation techniques in the field of early cancer detection. Although, exosomes are considered as ideal biomarkers in cancer diagnosis, due to their unique characteristics, there is still a long way in the development of exosome-based assays.

Optimizing Size Exclusion Chromatography for Extracellular Vesicle Enrichment and Proteomic Analysis from Clinically Relevant Samples

The field of extracellular vesicle (EV) research has rapidly expanded in recent years, with particular interest in their potential as circulating biomarkers. Proteomic analysis of EVs from clinical samples is complicated by the low abundance of EV proteins relative to highly abundant circulating proteins such as albumin and apolipoproteins. To overcome this, size exclusion chromatography (SEC) has been proposed as a method to enrich EVs whilst depleting protein contaminants; however, the optimal SEC parameters for EV proteomics have not been thoroughly investigated. Here, quantitative evaluation and optimization of SEC are reported for separating EVs from contaminating proteins. Using a synthetic model system followed by cell line-derived EVs, it is found that a 10 mL Sepharose 4B column in PBS produces optimal resolution of EVs from background protein. By spiking-in cancer cell-derived EVs to healthy plasma, it is shown that some cancer EV-associated proteins are detectable by nano-LC-MS/MS when as little as 1% of the total plasma EV number are derived from a cancer cell line. These results suggest that an optimized SEC and nanoLC-MS/MS workflow may be sufficiently sensitive for disease EV protein biomarker discovery from patient-derived clinical samples.

Comparative analysis and characterization of soluble factors and exosomes from cultured adipose tissue and bone marrow mesenchymal stem cells in canine species

The two main sources of mesenchymal stem cell (MSCs) in the canine species are bone marrow (cBM-MSCs) and adipose tissue (cAd-MSCs). The secretion of multitude bioactive molecules, included under the concept of secretome and found in the cultured medium, play a predominant role in the mechanism of action of these cells on tissue regeneration. Although certain features of its characterization are well documented, their secretory profiles remain unknown. We described and compared, for the first time, the secretory profile and exosomes characterization in standard monolayer culture of MSCs from both sources of the same donor as well as its immunomodulatory potential. We found that despite the similarity in surface immunophenotyping and trilineage differentiation, there are several differences in terms of proliferation rate and secretory profile. cAd-MSCs have advantages in proliferative capacity, whereas cBM-MSCs showed a significantly higher secretory production of some soluble factors (IL-10, IL-2, IL-6, IL-8, IL-12p40, IFN-γ, VEGF-A, NGF-β, TGF-β, NO and PGE2) and exosomes under the same standard culture conditions. Proteomics analysis confirm that cBM-MSCs exosomes have a greater number of characterized proteins involved in metabolic processes and in the regulation of biological processes compared to cAd-MSCs. On the other hand, secretome from both sources demonstrate similar immunomodulatory capacity when tested in mitogen stimulated lymphocyte reaction, but not in their exosomes at the dose used. Considering that the use of secretome open as a new therapeutic strategy for different diseases, without the need to implant cells, those biological differences should be considered, when choosing the MSCs source, for either cellular implantation or direct use of secretome for a specific clinical application.

Extracellular Vesicles Released by Human Induced-Pluripotent Stem Cell-Derived Cardiomyocytes Promote Angiogenesis

Although cell survival post-transplantation is very low, emerging evidence using stem cell therapy for myocardial repair points toward a primary role of paracrine signaling mechanisms as the basis for improved cardiac function, decreased fibrosis, and increased angiogenesis. Recent studies have demonstrated that extracellular vesicles (EVs) such as exosomes secreted by stem cells stimulate angiogenesis, provide cytoprotection, and modulate apoptosis. However, the angiogenic potential of EVs secreted from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM), a terminally differentiated cell type, has not been elucidated yet. Therefore, the main objective of this study is to isolate, characterize, and evaluate the in vitro angiogenic potential of EVs collected from hiPSC-CM conditioned media. The hiPSC-CM were cultured for 2 weeks and EVs were isolated from cell culture medium. Isolated EVs were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis, and immunoblotting. Furthermore, the angiogenic potential of these EVs was evaluated by tube formation, wound-healing, and cell-proliferation assays in bovine aortic endothelial cells (BAEC). In addition, gene expression levels of growth factors was evaluated in hiPSC-derived endothelial cells (hiPSC-EC) treated with hiPSC-CM-derived EV (CM-EVs) to assess their role in promoting angiogenesis. TEM imaging of CM-EVs showed a presence of a double-membrane bound structure, which is a characteristic of EV. Nanoparticle tracking analysis further confirmed the size and shape of the secreted particles to be consistent with EVs. Furthermore, EV-specific markers (CD63 and HSP70) were enriched in these particles as illustrated by immunoblotting. Most importantly, BAEC treated with 100 μg/ml of CM-EVs showed significant increases in tube formation, wound closure, and cell proliferation as compared to control (no-EVs). Finally, treatment of hiPSC-EC with CM-EVs induced increased expression of pro-angiogenic growth factors by the endothelial cells. Overall, our results demonstrated that EVs isolated from hiPSC-CM enhance angiogenesis in endothelial cells. This acellular/cell-free approach constitutes a potential translational therapeutic to induce angiogenesis in patients with myocardial infarction.

The Winding Road of Cardiac Regeneration-Stem Cell Omics in the Spotlight

Despite significant progress in treating ischemic cardiac disease and succeeding heart failure, there is still an unmet need to develop effective therapeutic strategies given the persistent high-mortality rate. Advances in stem cell biology hold great promise for regenerative medicine, particularly for cardiac regeneration. Various cell types have been used both in preclinical and clinical studies to repair the injured heart, either directly or indirectly. Transplanted cells may act in an autocrine and/or paracrine manner to improve the myocyte survival and migration of remote and/or resident stem cells to the site of injury. Still, the molecular mechanisms regulating cardiac protection and repair are poorly understood. Stem cell fate is directed by multifaceted interactions between genetic, epigenetic, transcriptional, and post-transcriptional mechanisms. Decoding stem cells’ “panomic” data would provide a comprehensive picture of the underlying mechanisms, resulting in patient-tailored therapy. This review offers a critical analysis of omics data in relation to stem cell survival and differentiation. Additionally, the emerging role of stem cell-derived exosomes as “cell-free” therapy is debated. Last but not least, we discuss the challenges to retrieve and analyze the huge amount of publicly available omics data.

Exosomes for Non-Invasive Cancer Monitoring

Exosomes, membrane-bound phospholipid vesicles having diameters of 50-200 nm, are secreted by all cell types and circulate in human body fluids. These vesicles are known to carry cellular constituents that are specific to the originating cells (e.g., cytoplasmic/membrane proteins, RNA, and DNA). Thus, exosomes, which are both structurally stable and abundant, are robust indicators of cancers and, as a result, they have been utilized to monitor this disease in a manner that is less invasive than gold standard tissue biopsies. In this review, the history of exosomes and the specific biomarkers present in exosomes that enable accurate monitoring of various diseases are described. In addition, methods for analysis of exosomes and identification of biomarkers are presented with special emphasis being given to isolation and signaling strategies. Lastly, integrated, microfluidic systems developed for exosome-based cancer diagnosis are described and future directions that research in this area will likely take are presented.

Tropism of mesenchymal stem cell toward CD133+ stem cell of glioblastoma in vitro and promote tumor proliferation in vivo

Background

Previous studies have demonstrated remarkable tropism of mesenchymal stem cells (MSCs) toward malignant gliomas, making these cells a potential vehicle for delivery of therapeutic agents to disseminated glioblastoma (GBM) cells. However, the potential contribution of MSCs to tumor progression is a matter of concern. It has been suggested that CD133⁺ GBM stem cells secrete a variety of chemokines, including monocytes chemoattractant protein-1 (MCP-1/CCL2) and stromal cell-derived factor-1(SDF-1/CXCL12), which could act in this tropism. However, the role in the modulation of this tropism of the subpopulation of CD133⁺ cells, which initiate GBM and the mechanisms underlying the tropism of MSCs to CD133⁺ GBM cells and their effects on tumor development, remains poorly defined.

Methods/results

We found that isolated and cultured MSCs (human umbilical cord blood MSCs) express CCR2 and CXCR4, the respective receptors for MCP-1/CCL2 and SDF-1/CXCL12, and demonstrated, in vitro, that MCP-1/CCL2 and SDF-1/CXC12, secreted by CD133⁺ GBM cells from primary cell cultures, induce the migration of MSCs. In addition, we confirmed that after in vivo GBM tumor establishment, by stereotaxic implantation of the CD133⁺ GBM cells labeled with Qdots (705 nm), MSCs labeled with multimodal iron oxide nanoparticles (MION) conjugated to rhodamine-B (Rh-B) (MION-Rh), infused by caudal vein, were able to cross the blood-brain barrier of the animal and migrate to the tumor region. Evaluation GBM tumors histology showed that groups that received MSC demonstrated tumor development, glial invasiveness, and detection of a high number of cycling cells.

Conclusions

Therefore, in this study, we validated the chemotactic effect of MCP-1/CCL2 and SDF-1/CXCL12 in mediating the migration of MSCs toward CD133⁺ GBM cells. However, we observed that, after infiltrating the tumor, MSCs promote tumor growth in vivo probably by release of exosomes. Thus, the use of these cells as a therapeutic carrier strategy to target GBM cells must be approached with caution.

Autocrine secretions enhance radioresistance in an exosome‑independent manner in NSCLC cells

Radiotherapy resistance in patient with non‑small cell lung cancer (NSCLC) reduces patient survival and remains a significant challenge for the treatment of NSCLC. Radiation resistance has been demonstrated to be affected by secreted factors, yet it remains unclear how autocrine secretions affect the radioresistance of NSCLC cells. In the present study, the NSCLC cell line, NCI‑H460, was irradiated with γ‑rays (4 Gy) and then cultured in medium from H460 cells or normal medium to examine the potential influence of cell secretions on the radiation resistance of H460 cells. Cell viability, accumulation of reactive oxygen species and DNA repair capacity were all markedly improved in the irradiated H460 cells that were cultured in conditioned medium (CM), compared with those cells cultured in normal medium. In addition, G2/M cell cycle arrest and upregulation of homologous recombination repair proteins were observed in the CM‑treated cells, while exosomes secreted by H460 cells had no influence on the radiation resistance of H460 cells. Taken together, these results indicate that autocrine secretions enhance the radiation resistance of γ‑irradiated H460 cells and that these secretions mainly affect the DNA repair process.

Extracellular histones are the ligands for the uptake of exosomes and hydroxyapatite-nanoparticles by tumor cells via syndecan-4

The mechanisms by which exosomes (nano-vesicular messengers of cells) are taken up by recipient cells are poorly understood. We hypothesized that histones associated with these nanoparticles are the ligands which facilitate their interaction with cell surface syndecan-4 (SDC4) to mediate their uptake. We show that the incubation with fetuin-A (exosome-associated proteins) and histones mediates the uptake of exosomes that are normally not endocytosed. Similarly, hydroxyapatite-nanoparticles incubated with fetuin-A and histones (FNH) are internalized by tumor cells, while nanoparticles incubated with fetuin-A alone (FN) are not. The uptake of exosomes and FNH, both of which move to the perinuclear region of the cell, is attenuated in SDC4-knockdown cells. Data show that FNH can compete with exosomes for uptake and that both use SDC4 as uptake receptors.

Stability of Circulating Exosomal miRNAs in Healthy Subjects

Exosomes are nano-vesicles present in the circulation that are involved in cell-to-cell communication and regulation of different biological processes. MicroRNAs (miRNAs) are part of their cargo and are potential biomarkers. Methods of exosome isolation and the inter-individual and intra-individual variations in circulating miRNA exosomal cargo have been poorly investigated. This study aims for comparing two exosome isolation methods and to assess the stability of eleven plasma exosomal miRNAs over time. In addition to evaluate miRNA variability of both kits, the effect of freezing plasma before exosome isolation or freezing isolated exosomes on miRNA stability was also evaluated. MiRNA levels were tested in 7 healthy subjects who underwent four different blood extractions obtained in 4 consecutive weeks. One of the isolation kits displayed generally better amplification signals, and miRNAs from exosomes isolated after freezing the plasma had the highest levels. Intra-subject and inter-subject coefficients of variance were lower for the same isolation kit after freezing plasma. Finally, miRNAs that showed an acceptable expression level were stable across the consecutive extractions. This study shows for the first time the stability over time of miRNAs isolated from circulating plasma exosomes, establishing a key step in the use of exosomal miRNAs as biomarkers.

Arthropod EVs mediate dengue virus transmission through interaction with a tetraspanin domain containing glycoprotein Tsp29Fb

Dengue virus (DENV) is a mosquito-borne flavivirus that causes dengue fever in humans, worldwide. Using in vitro cell lines derived from Aedes albopictus and Aedes aegypti, the primary vectors of DENV, we report that DENV2/DENV3-infected cells secrete extracellular vesicles (EVs), including exosomes, containing infectious viral RNA and proteins. A full-length DENV2 genome, detected in arthropod EVs, was infectious to naïve mosquito and mammalian cells, including human-skin keratinocytes and blood endothelial cells. Cryo-electron microscopy showed mosquito EVs with a size range from 30 to 250 nm. Treatments with RNase A, Triton X-100, and 4G2 antibody-bead binding assays showed that infectious DENV2-RNA and proteins are contained inside EVs. Viral plaque formation and dilution assays also showed securely contained infectious viral RNA and proteins in EVs are transmitted to human cells. Up-regulated HSP70 upon DENV2 infection showed no role in viral replication and transmission through EVs. In addition, qRT-PCR and immunoblotting results revealed that DENV2 up-regulates expression of a mosquito tetraspanin-domain-containing glycoprotein, designated as Tsp29Fb, in A. aegypti mosquitoes, cells, and EVs. RNAi-mediated silencing and antibody blocking of Tsp29Fb resulted in reduced DENV2 loads in both mosquito cells and EVs. Immunoprecipitation showed Tsp29Fb to directly interact with DENV2 E-protein. Furthermore, treatment with GW4869 (exosome-release inhibitor) affected viral burden, direct interaction of Tsp29Fb with E-protein and EV-mediated transmission of viral RNA and proteins to naïve human cells. In summary, we report a very important finding on EV-mediated transmission of DENV2 from arthropod to mammalian cells through interactions with an arthropod EVs-enriched marker Tsp29Fb.

Uptake Profiles of Human Serum Exosomes by Murine and Human Tumor Cells through Combined Use of Colloidal Nanoplasmonics and Flow Cytofluorimetric Analysis

Understanding extracellular vesicle (EV) internalization mechanisms and pathways in cells is of capital importance for both EV basic biology and clinical translation, but still presents analytical hurdles, such as undetermined purity grade and/or concentration of the EV samples and lack of standard protocols. We report an accessible, robust, and versatile method for resolving dose-dependent uptake profiles of exosomes-the nanosized (30-150 nm) subtypes of EVs of intracellular origin which are more intensively investigated for diagnostic and therapeutic applications-by cultured cells. The method is based on incubating recipient cells with consistently increasing doses of exosomes which are graded for purity and titrated by a COlorimetric NANoplasmonic (CONAN) assay followed by cell flow cytofluorimetric analysis. The proposed method allowed evaluation and comparison of the uptake of human serum exosomes by cancer cell lines of murine (TRAMP-C2) and human (LNCaP, DU145, MDA-MB-231, and A375) origin, setting a firmer footing for better characterization and understanding of exosome biology in different in vitro and (potentially) in vivo models of cancer growth.

Extracellular Vesicles in Oncology: Progress and Pitfalls in the Methods of Isolation and Analysis

The possibility to study solid tumors through the analysis of extracellular vesicles in biological fluids is one of the most exciting and rapidly advancing field in cancer research. The extracellular vesicles are tiny sacs released in both physiological and pathological conditions and can be used to monitor the evolution of several pathological states, including neoplastic diseases. Indeed, these vesicles carry biological informations and can affect the behavior of recipient cells by transferring proteins, DNA, RNA, and microRNA. In this review the authors analyze the methods to collect biological fluid samples (urine, plasma/serum, and cell supernatant), and to isolate and quantify extracellular vesicles highlighting advantages and drawbacks. Moreover, the authors provide an overview on the adoption and the advantages of the methods (such as digital PCR, next generation sequencing, reverse-phase protein microarrays, flow-cytometry, etc.) most frequently used to analyze the molecular content of extracellular vesicles. Despite the great scientific interest on this topic, there is still a great uncertainty about which is the best method for the collection, isolation, quantification, and molecular evaluation of these vesicles and a standardization is needed. The features of EVs make them ideal candidates for liquid biopsy-based biomarkers. However, the small size of EVs makes their analysis very difficult and requires multiple advanced technologies, being therefore a limitation.

Extracellular vesicles as circulating cancer biomarkers: opportunities and challenges

Extracellular vesicles (EVs) are small, lipid-bound particles containing nucleic acid and protein cargo which are excreted from cells under a variety of normal and pathological conditions. EVs have garnered substantial research interest in recent years, due to their potential utility as circulating biomarkers for a variety of diseases, including numerous types of cancer. The following review will discuss the current understanding of the form and function of EVs, their specific role in cancer pathogenesis and their potential for non-invasive disease diagnosis and/or monitoring. This review will also highlight several key issues for this field, including the importance of implementing robust and reproducible sample handling protocols, and the challenge of extracting an EV-specific biomarker signal from a complex biological background.

Ascent of atomic force microscopy as a nanoanalytical tool for exosomes and other extracellular vesicles

Over the last 30 years, atomic force microscopy (AFM) has made several significant contributions to the field of biology and medicine. In this review, we draw our attention to the recent applications and promise of AFM as a high-resolution imaging and force sensing technology for probing subcellular vesicles: exosomes and other extracellular vesicles. Exosomes are naturally occurring nanoparticles found in several body fluids such as blood, saliva, cerebrospinal fluid, amniotic fluid and urine. Exosomes mediate cell-cell communication, transport proteins and genetic content between distant cells, and are now known to play important roles in progression of diseases such as cancers, neurodegenerative disorders and infectious diseases. Because exosomes are smaller than 100 nm (about 30-120 nm), the structural and molecular characterization of these vesicles at the individual level has been challenging. AFM has revealed a new degree of complexity in these nanosized vesicles and generated growing interest as a nanoscale tool for characterizing the abundance, morphology, biomechanics, and biomolecular make-up of exosomes. With the recent interest in exosomes for diagnostic and therapeutic applications, AFM-based characterization promises to contribute towards improved understanding of these particles at the single vesicle and sub-vesicular levels. When coupled with complementary methods like optical super resolution STED and Raman, AFM could further unlock the potential of exosomes as disease biomarkers and as therapeutic agents.

Exosomes in Pancreatic Cancer: from Early Detection to Treatment

BACKGROUND

Pancreatic cancer (PC) remains one of the most fatal forms of cancer worldwide with incidence nearly equal to mortality. This is often attributed to the fact that diagnosis is often not made until later disease stages when treatment proves difficult. Efforts have been made to reduce the mortality of PC through improvements in early screening techniques and treatments of late-stage disease. Exosomes, small extracellular vesicles involved in cellular communication, have shown promise in helping understand PC disease biology.

METHODS

In this review, we discuss current studies of the role of exosomes in PC physiology, and their potential use as diagnostic and treatment tools.

RESULTS

Exosomes have a role in diagnosing pancreatic cancer and in understanding tumor biology including migration, proliferation, chemoresistance, immunosuppression, cachexia and diabetes, and have a potential role in therapy for pancreatic cancer.

CONCLUSIONS

Exosomal analysis is beneficial in demonstrating mechanisms behind PC growth and metastasis, immunosuppression, drug resistance, and paraneoplastic conditions. Furthermore, the use of exosomes can be beneficial in detecting early-stage PC and exosomes have potential applications as therapeutic targets.

"Exosomics"-A Review of Biophysics, Biology and Biochemistry of Exosomes With a Focus on Human Breast Milk

Exosomes are biomolecular nanostructures released from cells. They carry specific biomolecular information and are mainly researched for their exquisite properties as a biomarker source and delivery system. We introduce exosomes in the context of other extracellular vesicles, describe their biophysical isolation and characterisation and discuss their biochemical profiling. Motivated by our interest in early-life nutrition and health, and corresponding studies enrolling lactating mothers and their infants, we zoom into exosomes derived from human breast milk. We argue that these should be more extensively studied at proteomic and micronutrient profiling level, because breast milk exosomes provide a more specific window into breast milk quality from an immunological (proteomics) and nutritional (micronutrient) perspective. Such enhanced breast milk exosome profiling would thereby complement and enrich the more classical whole breast milk analysis and is expected to deliver more functional insights than the rather descriptive analysis of human milk, or larger fractions thereof, such as milk fat globule membrane. We substantiate our arguments by a bioinformatic analysis of two published proteomic data sets of human breast milk exosomes.

Janus-Faced Myeloid-Derived Suppressor Cell Exosomes for the Good and the Bad in Cancer and Autoimmune Disease

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells originally described to hamper immune responses in chronic infections. Meanwhile, they are known to be a major obstacle in cancer immunotherapy. On the other hand, MDSC can interfere with allogeneic transplant rejection and may dampen autoreactive T cell activity. Whether MDSC-Exosomes (Exo) can cope with the dangerous and potentially therapeutic activities of MDSC is not yet fully explored. After introducing MDSC and Exo, it will be discussed, whether a blockade of MDSC-Exo could foster the efficacy of immunotherapy in cancer and mitigate tumor progression supporting activities of MDSC. It also will be outlined, whether application of native or tailored MDSC-Exo might prohibit autoimmune disease progression. These considerations are based on the steadily increasing knowledge on Exo composition, their capacity to distribute throughout the organism combined with selectivity of targeting, and the ease to tailor Exo and includes open questions that answers will facilitate optimizing protocols for a MDSC-Exo blockade in cancer as well as for strengthening their therapeutic efficacy in autoimmune disease.

The functions and clinical applications of tumor-derived exosomes

Exosomes are extracellular vesicles with diameters ranging from 30 to 150 nm. They can be secreted by all cell types and transfer information in the form of their contents, which include proteins, lipids and nucleic acids, to other cells throughout the body. They have roles in normal physiological processes as well as in disease development. Here, we review recent findings regarding tumor-derived exosomes, including methods for their extraction and preservation. We also describe the actions of exosomes in tumorigenesis. The exosomal antigen-presenting effect during antitumor immune responses and its suppressive function in immune tolerance are discussed. Finally, we describe the potential application of exosomes to cancer therapy and liquid biopsy.

Exosomes serve as novel modes of tick-borne flavivirus transmission from arthropod to human cells and facilitates dissemination of viral RNA and proteins to the vertebrate neuronal cells

Molecular determinants and mechanisms of arthropod-borne flavivirus transmission to the vertebrate host are poorly understood. In this study, we show for the first time that a cell line from medically important arthropods, such as ticks, secretes extracellular vesicles (EVs) including exosomes that mediate transmission of flavivirus RNA and proteins to the human cells. Our study shows that tick-borne Langat virus (LGTV), a model pathogen closely related to tick-borne encephalitis virus (TBEV), profusely uses arthropod exosomes for transmission of viral RNA and proteins to the human- skin keratinocytes and blood endothelial cells. Cryo-electron microscopy showed the presence of purified arthropod/neuronal exosomes with the size range of 30 to 200 nm in diameter. Both positive and negative strands of LGTV RNA and viral envelope-protein were detected inside exosomes derived from arthropod, murine and human cells. Detection of Nonstructural 1 (NS1) protein in arthropod and neuronal exosomes further suggested that exosomes contain viral proteins. Viral RNA and proteins in exosomes derived from tick and mammalian cells were secured, highly infectious and replicative in all tested evaluations. Treatment with GW4869, a selective inhibitor that blocks exosome release affected LGTV loads in both arthropod and mammalian cell-derived exosomes. Transwell-migration assays showed that exosomes derived from infected-brain-microvascular endothelial cells (that constitute the blood-brain barrier) facilitated LGTV RNA and protein transmission, crossing of the barriers and infection of neuronal cells. Neuronal infection showed abundant loads of both tick-borne LGTV and mosquito-borne West Nile virus RNA in exosomes. Our data also suggest that exosome-mediated LGTV viral transmission is clathrin-dependent. Collectively, our results suggest that flaviviruses uses arthropod-derived exosomes as a novel means for viral RNA and protein transmission from the vector, and the vertebrate exosomes for dissemination within the host that may subsequently allow neuroinvasion and neuropathogenesis.

Pancreatic Cancer Diagnosis and Management: Has the Time Come to Prick the Bubble?

Pancreatic cancer (PC) is associated with poor prognosis and very dismal survival rates. The most effective possibility of cure is tumor resection, which is only possible in about 15% of patients diagnosed at early stages of disease progression. Recent whole-genome sequencing studies pointed genetic alterations in 12 core signaling pathways in PC. These observations hint at the possibility that the initial mutation in PC might appear nearly 20 years before any symptoms occur, suggesting that a large window of opportunity may exist for early detection. Biomarkers with the potential to identify pre-neoplastic disease or very early stages of cancer are of great promise to improve patient survival. The concept of liquid biopsy refers to a minimally invasive sampling and analysis of liquid biomarkers that can be isolated from body fluids, primarily blood, urine and saliva. A myriad of circulating molecules may be useful as tumor markers, including cell-free DNA (cfDNA), cell-free RNA (cfRNA), circulating tumor cells (CTC), circulating tumor proteins, and extracellular vesicles, more specifically exosomes. In this review, we discuss with more detail the potential role of exosomes in several aspects related to PC, from initiation to tumor progression and its applicability in early detection and treatment. Exosomes are small circulating extracellular vesicles of 50-150 nm in diameter released from the plasma membrane by almost all cells and exhibit some advantages over other biomarkers. Exosomes are central players of intercellular communication and they have been implicated in a series of biological process, including tumorigenesis, migration and metastasis. Several exosomal microRNAs and proteins have been observed to distinguish PC from benign pancreatic diseases and healthy controls. Besides their possible role in diagnosis, understanding exosomes functions in cancer has clarified the importance of microenvironment in PC progression as well as its influence in proliferation, metastasis and resistance to chemotherapy. Increasing knowledge on cancer exosomes provides valuable insights on new therapeutic targets and can potentially open new strategies to treat this disease. Continuous research is needed to ascertain the reliability of using exosomes and their content as potential biomarkers, so that, hopefully, in the near future, they will provide the opportunity for early diagnosis, treatment intervention and increase survival of PC patients.

Post-translational add-ons mark the path in exosomal protein sorting

Extracellular vesicles (EVs) are released by cells to the extracellular environment to mediate inter-cellular communication. Proteins, lipids, nucleic acids and metabolites shuttled in these vesicles modulate specific functions in recipient cells. The enrichment of selected sets of proteins in EVs compared with global cellular levels suggests the existence of specific sorting mechanisms to specify EV loading. Diverse post-translational modifications (PTMs) of proteins participate in the loading of specific elements into EVs. In this review, we offer a perspective on PTMs found in EVs and discuss the specific role of some PTMs, specifically Ubiquitin and Ubiquitin-like modifiers, in exosomal sorting of protein components. The understanding of these mechanisms will provide new strategies for biomedical applications. Examples include the presence of defined PTM marks on EVs as novel biomarkers for the diagnosis and prognosis of certain diseases, or the specific import of immunogenic components into EVs for vaccine generation.

Magnetic Particle-Based Immunoprecipitation of Nanoscale Extracellular Vesicles from Biofluids

Analysis of nanoscale extracellular vesicles (nsEVs) present in blood, cell culture media, and other biofluids has shown tremendous promise in enabling the development of noninvasive blood-based clinical diagnostic tests, predicting and monitoring the efficacy of treatment programs, and providing molecular level insights into pathology that can enlighten new drug targets in the contexts of health conditions such as cancer and Alzheimer's Disease (AD). In this chapter, we present methods for using magnetic particle-based immunoprecipitation to enrich highly purified populations of nsEVs directly from plasma, serum, and other biofluids. These methods enable downstream analysis of nsEV protein and nucleic acid constituents in the contexts of both global omics profiling and quantification of individual protein or nucleic acid species of interest. Additionally, these methods allow the researcher to either enrich total nsEV populations or enrich nsEVs derived from a particular tissue type from the overall nsEV population. The methods described here are compatible with parallel processing of dozens of biofluid samples and can be valuable tools for enabling nsEV analyses that have high translational relevance in the development of both novel therapeutics and noninvasive diagnostic assays.

Insights into the Proteome of Gastrointestinal Stromal Tumors-Derived Exosomes Reveals New Potential Diagnostic Biomarkers

Developing tumors continuously release nano-sized vesicles that represent circulating "fingerprints" of the tumor's identity. In gastrointestinal stromal tumor (GIST), we have previously reported that these tumors release "oncosomes" carrying the constitutively activated tyrosine kinase (TK) receptor KIT. Despite the clinical utility of TK inhibitors, such as imatinib mesylate (IM), recurrence and metastasis are clinical problems that urge the need to identify new tumor-derived molecules. To this aim, we performed the first high quality proteomic study of GIST-derived exosomes (GDEs) and identified 1,060 proteins composing the core GDE proteome (cGDEp). The cGDEp was enriched in diagnostic markers (e.g. KIT, CD34, ANO1, PROM1, PRKCQ, and ENG), as well as proteins encoded by genes previously reported expressed in GIST (e.g. DPP4, FHL1, CDH11, and KCTD12). Many of these proteins were validated using cell lines, patient-derived KIT⁺ exosomes, and GIST tissues. We further show that in vitro and in vivo-derived GDE, carry proteins associated with IM response, such as Sprouty homolog 4 (SPRY4), surfeit 4 (SURF4), ALIX, and the cGMP-dependent 3',5'-cyclic phosphodiesterase 2A (PDE2A). Additionally, we report that the total exosome levels and exosome-associated KIT and SPRY4 protein levels have therapeutic values. In fact, molecular characterization of in vivo-derived KIT⁺ exosomes indicate significant sorting of p-KIT^Tyr719, total KIT, and SPRY4 after IM-treatment of metastatic patients as compared with the pre-IM levels. Our data suggest that analysis of circulating exosomes levels and molecular markers of IM response in GIST patients with primary and metastatic disease is suitable to develop liquid based biopsies for the diagnosis, prognosis, and monitoring of response to treatment of these tumors. In summary, these findings provide the first insight into the proteome of GIST-derived oncosomes and offers a unique opportunity to further understand their oncogenic elements which contribute to tumorigenesis and drug resistance. Data are available via ProteomeXchange with identifier PXD007997.

Extracellular Vesicles in Neurodegenerative Diseases: A Double-Edged Sword

Extracellular vesicles (EVs), a heterogenous group of membrane-bound particles, are virtually secreted by all cells and play important roles in cell-cell communication. Loaded with proteins, mRNAs, non-coding RNAs and membrane lipids from their donor cells, these vesicles participate in normal physiological and pathogenic processes. In addition, these sub-cellular vesicles are implicated in the progression of neurodegenerative disorders. Accumulating evidence suggests that intercellular communication via EVs is responsible for the propagation of key pathogenic proteins involved in the pathogenesis of amyotrophic lateral sclerosis, Parkinson's diseases, Alzheimer's diseases and other neurodegenerative disorders. For therapeutic perspective, EVs present advantage over other synthetic drug delivery systems or cell therapy; ability to cross biological barriers including blood brain barrier (BBB), ability to modulate inflammation and immune responses, stability and longer biodistribution with lack of tumorigenicity. In this review, we summarized the current state of EV research in central nervous system in terms of their values in diagnosis, disease pathology and therapeutic applications.

Technical Advances to Study Extracellular Vesicles

Extracellular vesicles are a heterogeneous and dynamic group of lipid bilayer membrane nanoparticles that can be classified into three different groups depending on their cellular origin: exosomes, microvesicles, and apoptotic bodies. They are produced by different cell types and can be isolated from almost all body fluids. EVs contain a variety of proteins, lipids, nucleic acids, and metabolites which regulate a number of biological and pathological scenarios both locally and systemically. Different techniques have been described in order to determine EV isolation, release, uptake, and cargo. Although standard techniques such as immunoblotting, fluorescent microscopy, and electron microscopy are still being used to characterize and visualize EVs, in the last years, more fine-tuned techniques are emerging. For example, EV uptake can be specifically determined at a single cell level using the Cre reporter methodology and bioluminescence based-methods reports have been employed to determine both EV release and uptake. In addition, techniques for cargo identification have also enormously evolved during these years. Classical mass spectrometry and next generation sequencing have been used in the past, but nowadays, advances in these tools have facilitated a more in depth characterization of the EV content. In this review, we aim to assess the standard and latest technical advances for studying EV biology in different biological systems.

Exosomes Secreted by HeLa Cells Shuttle on Their Surface the Plasma Membrane-Associated Sialidase NEU3

Sialidases are glycohydrolases that remove terminal sialic acid residues from oligosaccharides, glycolipids, and glycoproteins. The plasma membrane-associated sialidase NEU3 is involved in the fine-tuning of sialic acid-containing glycans directly on the cell surface and plays relevant roles in important biological phenomena such as cell differentiation, molecular recognition, and cancer transformation. Extracellular vesicles are membranous structures with a diameter of 0.03-1 μm released by cells and can be detected in blood, urine, and culture media. Among extracellular vesicles, exosomes play roles in intercellular communication and maintenance of several physiological and pathological conditions, including cancer, and could represent a useful diagnostic tool for personalized nanomedicine approaches. Using inducible expression of the murine form of NEU3 in HeLa cells, a study of the association of the enzyme with exosomes released in the culture media has been performed. Briefly, NEU3 is associated with highly purified exosomes and localizes on the external leaflet of these nanovesicles, as demonstrated by enzyme activity measurements, Western blot analysis, and dot blot analysis using specific protein markers. On the basis of these results, it is plausible that NEU3 activity on exosome glycans enhances the dynamic biological behavior of these small extracellular vesicles by modifying the negative charge and steric hindrance of their glycocalyx. The presence of NEU3 on the exosomal surface could represent a useful marker for the detection of these nanovesicles and a tool for improving our understanding of the biology of these important extracellular carriers in physiological and pathological conditions.

The HBx gene of hepatitis B virus can influence hepatic microenvironment via exosomes by transferring its mRNA and protein

The cellular secretory vesicles known as 'exosomes' have emerged as key player in intercellular transport and communication between different eukaryotic in order to maintain body homeostasis. Many pathogenic viruses utilize exosome pathway to efficiently transfer bioactive components from infected cells to naïve cells. Here, we show that HBx can tweak the exosome biogenesis machinery both by enhancing neutral sphingomyelinase2 activity as well as by interacting with exosomal biomarkers such as neutral sphingomyelinase2, CD9 and CD81. The nano particle tracking analysis revealed enhanced secretion of exosomes by the HBx-expressing cells while confocal studies confirmed the co-localization of HBx with CD9 and CD63. Importantly, we observed the encapsulation of HBx mRNA and protein in these exosomes besides some other qualitative changes. The exosomal cargo secreted by HBx-expressing cells had a profound effect on the recipient hepatic cells including creation of a milieu conducive for cellular-transformation. Thus, the present study unfolds a novel role of HBx in intercellular communication by facilitating horizontal transfer of viral gene products and other host factors via exosomes in order to support viral spread and pathogenesis.

Endothelial cell-derived exosomes protect SH-SY5Y nerve cells against ischemia/reperfusion injury

Cerebral ischemia is a leading cause of death and disability. A previous study indicated that remote ischemic postconditioning (RIP) in the treatment of cerebral ischemia reduces ischemia/reperfusion (I/R) injury. However, the underlying mechanism is not well understood. In the present study, the authors hypothesized that the protective effect of RIP on neurological damage is mediated by exosomes that are released by endothelial cells in femoral arteries. To test this, right middle cerebral artery occlusion/reperfusion with RIP was performed in rats. In addition, an I/R injury cell model was tested that included human umbilical vein endothelial cells (HUVECs) and SH-SY5Y cells. Both the in vivo and in vitro models were examined for injury. Markers of exosomes (CD63, HSP70 and TSG101) were assessed by immunohistochemistry, western blot analysis and flow cytometry. Exosomes were extracted from both animal serum and HUVEC culture medium and identified by electron microscopy. They investigated the role of endothelial cell-derived exosomes in the proliferation, apoptosis, cell cycle, migration and invasion of I/R-injured SH-SY5Y cells. In addition, apoptosis-related molecules caspase-3, Bax and Bcl-2 were detected. RIP was determined to increase the number of exosomes and the expression levels of CD63, HSP70 and TSG101 in plasma, but not in brain hippocampal tissue. The size of exosomes released after I/R in HUVECs was similar to the size of exosomes released in rats subjected to RIP. Endothelial cell-derived exosomes partly suppressed the I/R-induced cell cycle arrest and apoptosis, and inhibited cell proliferation, migration and invasion in SH-SY5Y nerve cells. Endothelial cell-derived exosomes directly protect nerve cells against I/R injury, and are responsible for the protective role of RIP in I/R.

Emerging MS-based platforms for the characterization of tumor-derived exosomes isolated from human biofluids: challenges and promises of MudPIT

INTRODUCTION

Exosomes are small extracellular vesicles of endosomal origin that are produced and released by several type of cells. These vesicles contain different macromolecules: proteins, mRNA, miRNA, mitochondrial DNA, and lipids. Exosomes play an important role in cell-to-cell communication, also promoting cancer progression. Areas covered: Various proteomic approaches have been applied to study exosomes isolated from different human biofluids in search of possible cancer biomarkers. The results of these studies are reported, and pros and cons of each employed technique are described. Gel-free and gel-based mass spectrometry systems are discussed, giving particular emphasis on the innovative multidimensional protein identification technology (MudPIT). Expert commentary: Proteomic studies on exosomes as candidate cancer biomarkers from urine and other body fluids in cancer have shown the potential of MS-based techniques. In particular, MudPIT is a promising tool to be applied in clinical proteomics of cancer.

Proteomic analysis of exosomal cargo: the challenge of high purity vesicle isolation

The re-discovery of exosomes as intercellular messengers with high potential for diagnostic and therapeutic utility has led to them becoming a popular topic of research in recent years. One of the essential research areas in this field is the characterization of exosomal cargo, which includes numerous non-randomly packed proteins and nucleic acids. Unexpectedly, a very challenging aspect of exploration of extracellular vesicles has turned out to be their effective and selective isolation. The plurality of developed protocols leads to qualitative and quantitative variability in terms of the obtained exosomes, which significantly affects the results of downstream analyses and makes them difficult to compare, reproduce and interpret between research groups. Currently, there is a general consensus among the exosome-oriented community concerning the urgent need for the optimization and standardization of methods employed for the purification of these vesicles. Hence, we review here several strategies for exosome preparation including ultracentrifugation, chemical precipitation, affinity capturing and filtration techniques. The advantages and disadvantages of different approaches are discussed with special emphasis being placed on their adequacy for proteomics applications, which are particularly sensitive to sample quality. We conclude that certain methods, exemplified by ultracentrifugation combined with iodixanol density gradient centrifugation or gel filtration, although labor-intensive, provide superior quality exosome preparations suitable for reliable analysis by mass spectrometry.

Mesenchymal stem cell-derived exosomes as a new therapeutic strategy for liver diseases

The administration of mesenchymal stem cells (MSCs) as a therapy for liver disease holds great promise. MSCs can differentiate into hepatocytes, reduce liver inflammation, promote hepatic regeneration and secrete protective cytokines. However, the risks of iatrogenic tumor formation, cellular rejection and infusional toxicity in MSC transplantation remain unresolved. Accumulating evidence now suggests that a novel cell-free therapy, MSC-secreted exosomes, might constitute a compelling alternative because of their advantages over the corresponding MSCs. They are smaller and less complex than their parent cells and, thus, easier to produce and store, they are devoid of viable cells, and they present no risk of tumor formation. Moreover, they are less immunogenic than their parent cells because of their lower content in membrane-bound proteins. This paper reviews the biogenesis of MSC exosomes and their physiological functions, and highlights the specific biochemical potential of MSC-derived exosomes in restoring tissue homeostasis. In addition, we summarize the recent advances in the role of exosomes in MSC therapy for various liver diseases, including liver fibrosis, acute liver injury and hepatocellular carcinoma. This paper also discusses the potential challenges and strategies in the use of exosome-based therapies for liver disease in the future.

Diagnostic and Therapeutic Potential of Exosomes in Cancer: The Beginning of a New Tale?

Exosomes have emerged as one of the main players in intercellular communication. These small nano-sized particles have many roles in various physiological pathways in normal and abnormal cells. Exosomes can carry various cargos such as proteins, mRNAs, and miRNAs to recipient cells. Uptake of exosomes and their cargo can induce and/or inhibit different cellular and molecular pathways that lead to the alteration of cell behavior. Multiple lines of evidence have indicated that exosomes released from cancer cells can effect development of cancer in different stages. These particles and their cargo could regulate different processes such as tumor growth, metastasis, drug resistance, angiogenesis, and immune system functioning. It has been observed that exosomes can be used as potential diagnostic biomarkers in various cancer types. Moreover, some studies have used these particles as biological vehicles for delivery of various drugs such as doxorubicin, siRNAs, and miRNAs. Here, we summarized the findings on the role of exosomes in different pathological processes involved in cancer. Moreover, application of these particles as diagnostic and therapeutic biomarkers in different types of cancers is discussed. J. Cell. Physiol. 232: 3251-3260, 2017. © 2016 Wiley Periodicals, Inc.

Preliminary Study of Plasma Exosomal Tau as a Potential Biomarker for Chronic Traumatic Encephalopathy

Background:

Chronic traumatic encephalopathy (CTE) is a tauopathy associated with prior exposure to repetitive head impacts, such as those incurred through American football and other collision sports. Diagnosis is made through neuropathological examination. Many of the clinical features of CTE are common in the general population, with and without a history of head impact exposure, making clinical diagnosis difficult. As is now common in the diagnosis of other neurodegenerative disorders, such as Alzheimer’s disease, there is a need for methods to diagnose CTE during life through objective biomarkers.

Objective:

The aim of this study was to examine tau-positive exosomes in plasma as a potential CTE biomarker.

Methods:

Subjects were 78 former National Football League (NFL) players and 16 controls. Extracellular vesicles were isolated from plasma. Fluorescent nanoparticle tracking analysis was used to determine the number of vesicles staining positive for tau.

Results:

The NFL group had higher exosomal tau than the control group (p <  0.0001). Exosomal tau discriminated between the groups, with 82% sensitivity, 100% specificity, 100% positive predictive value, and 53% negative predictive value. Within the NFL group, higher exosomal tau was associated with worse performance on tests of memory (p = 0.0126) and psychomotor speed (p = 0.0093).

Conclusion:

These preliminary findings suggest that exosomal tau in plasma may be an accurate, noninvasive CTE biomarker.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Progress and potential of exosome analysis for early pancreatic cancer detection

INTRODUCTION

Pancreatic cancer (PaCa) is the most deadly malignancy, due to late diagnosis prohibiting surgery. Thus, strong efforts are taken improving early diagnosis via biomarkers recovered in the serum of PaCa patients.

AREAS COVERED

One promising option are PaCa-derived exosomes in patients' sera. Exosomes, small vesicles delivered by live cells and recovered in all body fluids, are a powerful diagnostic tool due to relative stability and composition covering the whole range of cancer-related biomarkers including proteins, metabolites, DNA, DNA modifications, coding and noncoding RNA. We discuss the mechanisms accounting for the condensed packaging of biomarkers, refer to studies using PaCa serum-exosomes for diagnosis. Based on an extensive literature search, we outline questions that answers may help establishing a serum-exosome-based screening for early PaCa detection. Expert commentary: Improved proteomic and genomic characterization and progress in the biogenesis of exosomes will allow for optimized and unified screening panels for PaCa diagnosis via TEX in body fluids.

Urinary proteomics and metabolomics studies to monitor bladder health and urological diseases

Background

Assays of molecular biomarkers in urine are non-invasive compared to other body fluids and can be easily repeated. Based on the hypothesis that the secreted markers from the diseased organs may locally release into the body fluid in the vicinity of the injury, urine-based assays have been considered beneficial to monitoring bladder health and urological diseases. The urine proteome is much less complex than the serum and tissues, but nevertheless can contain biomarkers for diagnosis and prognosis of diseases. The urine metabolome has a much higher number and concentration of low-molecular metabolites than the serum or tissues, with a far lower lipid concentration, yet informs directly about dietary and microbial metabolism.

Discussion

We here discuss the use of mass spectrometry-based proteomics and metabolomics for urine biomarker assays, specifically with respect to the underlying mechanisms that trigger the pathological condition.

Conclusion

Molecular biomarker profiles, based on proteomics and metabolomics studies, reliably distinguish patients from healthy controls, stratify sub-populations with respect to treatment options, and predict therapeutic response of patients with urological disease.

The epithelial-mesenchymal transition in cancer: a potential critical topic for translational proteomic research

The epithelial-mesenchymal transition (EMT) is a morphogenetic process that results in a loss of epithelial characteristics and the acquisition of a mesenchymal phenotype. First described in embryogenesis, the EMT has been recently implicated in carcinogenesis and tumor progression. In addition, recent evidence has shown that stem-like cancer cells present the hallmarks of the EMT. Some of the molecular mechanisms related to the interrelationships between cancer pathophysiology and the EMT are well-defined. Nevertheless, the precise molecular mechanism by which epithelial cancer cells acquire the mesenchymal phenotype remains largely unknown. This review focuses on various proteomic strategies with the goal of better understanding the physiological and pathological mechanisms of the EMT process.