Isolation of Biologically Active Exosomes from Plasma of Patients with Cancer

Isolation and usage of exosomes in central nervous system diseases

BACKGROUND

Exosomes are vesicles secreted by all types of mammalian cells. They are characterized by a double-layered lipid membrane structure. They serve as carriers for a plethora of signal molecules, including DNA, RNA, proteins, and lipids. Their unique capability of effortlessly crossing the blood-brain barrier underscores their critical role in the progression of various neurological disorders. This includes, but is not limited to, diseases such as Alzheimer's, Parkinson's, and ischemic stroke. Establishing stable and mature methods for isolating exosomes is a prerequisite for the study of exosomes and their biomedical significance. The extraction technologies of exosomes include differential centrifugation, density gradient centrifugation, size exclusion chromatography, ultrafiltration, polymer coprecipitation, immunoaffinity capture, microfluidic, and so forth. Each extraction technology has its own advantages and disadvantages, and the extraction standards of exosomes have not been unified internationally.

AIMS

This review aimed to showcase the recent advancements in exosome isolation techniques and thoroughly compare the advantages and disadvantages of different methods. Furthermore, the significant research progress made in using exosomes for diagnosing and treating central nervous system (CNS) diseases has been emphasized.

CONCLUSION

The varying isolation methods result in differences in the concentration, purity, and size of exosomes. The efficient separation of exosomes facilitates their widespread application, particularly in the diagnosis and treatment of CNS diseases.

Pneumococcal Extracellular Vesicles Mediate Horizontal Gene Transfer via the Transformation Machinery

Bacterial cells secrete extracellular vesicles (EVs), the function of which is a matter of intense investigation. Here, we show that the EVs secreted by the human pathogen Streptococcus pneumoniae (pneumococcus) are associated with bacterial DNA on their surface and can deliver this DNA to the transformation machinery of competent cells. These findings suggest that EVs contribute to gene transfer in Gram-positive bacteria, and in doing so, may promote the spread of drug resistance genes in the population.

Immune capture and protein profiling of small extracellular vesicles from human plasma

Extracellular vesicles (EVs), the key players in inter-cellular communication, are produced by all cell types and are present in all body fluids. Analysis of the proteome content is an important approach in structural and functional studies of these vesicles. EVs circulating in human plasma are heterogeneous in size, cellular origin, and functions. This heterogeneity and the potential presence of contamination with plasma components such as lipoprotein particles and soluble plasma proteins represent a challenge in profiling the proteome of EV subsets by mass spectrometry. An immunocapture strategy prior to mass spectrometry may be used to isolate a homogeneous subpopulation of small EVs (sEV) with a specific endocytic origin from plasma or other biofluids. Immunocapture selectively separates EV subpopulations in biofluids based on the presence of a unique protein carried on the vesicle surface. The advantages and disadvantages of EV immune capture as a preparative step for mass spectrometry are discussed.

Optimization of Isolation Method for Extracellular Vesicles from Pancreatic Juice and Impact of Protease Activity

BACKGROUNDS

Pancreatic juice (PJ) is directly associated with pancreatic lesions, including pancreatic ductal cancer and intraductal papillary mucinous neoplasm-derived cancer. Therefore, EVs secreted from these lesions into PJ can be promising biomarkers for early diagnosis. However, there are limited data from analysis of EVs in PJ samples.

AIMS AND METHODS

We aimed to determine the stability of EVs in PJ collected using endoscopic naso-pancreatic drainage (ENPD) tubes as well as catheter during endoscopic retrograde cholangiography (ERCP), with or without the impact of positive protease activity, and optimize the EV isolation method.

RESULTS

Size exclusion chromatography was found to be an optimal isolation method for EVs in PJ as it achieved higher recovery and purity of EVs compared with differential ultracentrifugation and polymer-based precipitation. Approximately 40% of the PJ samples collected during ERCP and more than 90% of those collected using ENPD tubes had positive protease activity. In vitro exposure to room temperature for less than 3 h was harmless to the structure of double-membrane EVs in PJ and the expression levels of TSG101, even with positive protease activity.

CONCLUSIONS

We clarified the physiobiological status of EVs in PJ and optimized the EV isolation method using suitable PJ samples; these findings can be utilized to discover biomarkers for cancer diagnosis and elucidate their function.

Current status and outlook of advances in exosome isolation

Exosomes are extracellular vesicles with a diameter ranging from 30 to 150 nm, which are an important medium for intercellular communication and are closely related to the progression of certain diseases. Therefore, exosomes are considered promising biomarkers for the diagnosis of specific diseases, and thereby, treatments based on exosomes are being widely examined. For exosome-related research, a rapid, simple, high-purity, and recovery isolation method is the primary prerequisite for exosomal large-scale application in medical practice. Although there are no standardized methods for exosome separation and analysis, various techniques have been established to explore their biochemical and physicochemical properties. In this review, we analyzed the progress in exosomal isolation strategies and proposed our views on the development prospects of various exosomal isolation techniques.

Exosomal CD73 from serum of patients with melanoma suppresses lymphocyte functions and is associated with therapy resistance to anti-PD-1 agents

BACKGROUND

CD73 is an ectonucleotidase producing the immunosuppressor mediator adenosine. Elevated levels of circulating CD73 in patients with cancer have been associated with disease progression and poor response to immunotherapy. Immunosuppressive pathways associated with exosomes can affect T-cell function and the therapeutic efficacy of anti-programmed cell-death protein 1 (anti-PD-1) therapy. Here, we conducted a retrospective pilot study to evaluate levels of exosomal CD73 before and early during treatment with anti-PD-1 agents in patients with melanoma and its potential contribution to affect T-cell functions and to influence the clinical outcomes of anti-PD-1 monotherapy.

METHODS

Exosomes were isolated by mini size exclusion chromatography from serum of patients with melanoma (n=41) receiving nivolumab or pembrolizumab monotherapy. Expression of CD73 and programmed death-ligand 1 (PD-L1) were evaluated on exosomes enriched for CD63 by on-bead flow cytometry. The CD73 AMPase activity was evaluated by mass spectrometry, also in the presence of selective inhibitors of CD73. Interferon (IFN)-γ production and granzyme B expression were measured in CD3/28 activated T cells incubated with exosomes in presence of the CD73 substrate AMP. Levels of CD73 and PD-L1 on exosomes were correlated with therapy response. Exosomes isolated from healthy subjects were used as control.

RESULTS

Isolated exosomes carried CD73 on their surface, which is enzymatically active in producing adenosine. Incubation of exosomes with CD3/28 activated T cells in the presence of AMP resulted in a significant reduction of IFN-γ release, which was reversed by the CD73 inhibitor APCP or by the selective A2A adenosine receptor antagonist ZM241385. Expression levels of exosomal CD73 from serum of patients with melanoma were not significantly different from those in healthy subjects. Early on-treatment, expression levels of both CD73 and PD-L1 on exosomes isolated from patients receiving pembrolizumab or nivolumab monotherapy were significantly increased compared with baseline. Early during therapy exosomal PD-L1 increased in responders, while exosomal CD73 resulted significantly increased in non-responders.

CONCLUSIONS

CD73 expressed on exosomes from serum of patients with melanoma produces adenosine and contributes to suppress T-cell functions. Early on-treatment, elevated expression levels of exosomal CD73 might affect the response to anti-PD-1 agents in patients with melanoma who failed to respond to therapy.

Characterization of Extracellular Vesicles from Bronchoalveolar Lavage Fluid and Plasma of Patients with Lung Lesions Using Fluorescence Nanoparticle Tracking Analysis

The current lack of reliable methods for quantifying extracellular vesicles (EVs) isolated from complex biofluids significantly hinders translational applications in EV research. The recently developed fluorescence nanoparticle tracking analysis (FL-NTA) allows for the detection of EV-associated proteins, enabling EV content determination. In this study, we present the first comprehensive phenotyping of bronchopulmonary lavage fluid (BALF)-derived EVs from non-small cell lung cancer (NSCLC) patients using classical EV-characterization methods as well as the FL-NTA method. We found that EV immunolabeling for the specific EV marker combined with the use of the fluorescent mode NTA analysis can provide the concentration, size, distribution, and surface phenotype of EVs in a heterogeneous solution. However, by performing FL-NTA analysis of BALF-derived EVs in comparison to plasma-derived EVs, we reveal the limitations of this method, which is suitable only for relatively pure EV isolates. For more complex fluids such as plasma, this method appears to not be sensitive enough and the measurements can be compromised. Our parallel presentation of NTA-based phenotyping of plasma and BALF EVs emphasizes the great impact of sample composition and purity on FL-NTA analysis that has to be taken into account in the further development of FL-NTA toward the detection of EV-associated cancer biomarkers.

Nanoparticle-Aided Detection of Colorectal Cancer-Associated Glycoconjugates of Extracellular Vesicles in Human Serum

Extracellular vesicles (EVs) are found in all biological fluids, providing potential for the identification of disease biomarkers such as colorectal cancer (CRC). EVs are heavily glycosylated with specific glycoconjugates such as tetraspanins, integrins, and mucins, reflecting the characteristics of the original cell offering valuable targets for detection of CRC. We report here on europium-nanoparticle (EuNP)-based assay to detect and characterize different surface glycoconjugates of EVs without extensive purification steps from five different CRC and the HEK 293 cell lines. The promising EVs candidates from cell culture were clinically evaluated on small panel of serum samples including early-stage (n = 11) and late-stage (n = 11) CRC patients, benign condition (n = 11), and healthy control (n = 10). The majority of CRC cell lines expressed tetraspanin sub-population and glycovariants of integrins and conventional tumor markers. The subpopulation of CD151 having CD63 expression (CD151^CD63) was significantly (p = 0.001) elevated in early-stage CRC (8 out of 11) without detecting any benign and late-stage samples, while conventional CEA detected mostly late-stage CRC (p = 0.045) and with only four early-stage cases. The other glycovariant assays such as CEA^Con-A, CA125^WGA, CA 19.9^Ma696, and CA 19.9^Con-A further provided some complementation to the CD151^CD63 assay. These results indicate the potential application of CD151^CD63 assay for early detection of CRC patients in human serum.

Role of exosomes in pancreatic cancer

Pancreatic cancer (PC) is a malignant tumour of the human digestive system that has a poor prognosis. Exosomes contain proteins and nucleic acids, and constitute a class of extracellular vesicles defined as membrane-bound nanovesicles of endocytic origin, with a diameter of 40-150 nm. Exosomes are potential diagnostic markers of PC; however, their roles in cancer initiation and progression remain unclear. Previous studies have focused on the molecular mechanisms and functions of exosomes that allow them to accelerate PC cell proliferation, migration and invasion. The present review discusses the interactions between exosomes and the pathophysiology of PC. The potential clinical applications of exosomes are also discussed.

Progress on pivotal role and application of exosome in lung cancer carcinogenesis, diagnosis, therapy and prognosis

Lung cancer is often diagnosed at an advanced stage and has a poor prognosis. Conventional treatments are not effective for metastatic lung cancer therapy. Although some of molecular targets have been identified with favorable response, those targets cannot be exploited due to the lack of suitable drug carriers. Lung cancer cell-derived exosomes (LCCDEs) receive recent interest in its role in carcinogenesis, diagnosis, therapy, and prognosis of lung cancer due to its biological functions and natural ability to carry donor cell biomolecules. LCCDEs can promote cell proliferation and metastasis, affect angiogenesis, modulate antitumor immune responses during lung cancer carcinogenesis, regulate drug resistance in lung cancer therapy, and be now considered an important component in liquid biopsy assessments for detecting lung cancer. Therapeutic deliverable exosomes are emerging as promising drug delivery agents specifically to tumor high precision medicine because of their natural intercellular communication role, excellent biocompatibility, low immunogenicity, low toxicity, long blood circulation ability, biodegradable characteristics, and their ability to cross various biological barriers. Several studies are currently underway to develop novel diagnostic and prognostic modalities using LCCDEs, and to develop methods of exploiting exosomes for use as efficient drug delivery vehicles. Current status of lung cancer and extensive applicability of LCCDEs are illustrated in this review. The promising data and technologies indicate that the approach on LCCDEs implies the potential application of LCCDEs to clinical management of lung cancer patients.

Interrupting Neuron-Tumor Interactions to Overcome Treatment Resistance

Neurons in the tumor microenvironment release neurotransmitters, neuroligins, chemokines, soluble growth factors, and membrane-bound growth factors that solid tumors leverage to drive their own survival and spread. Tumors express nerve-specific growth factors and microRNAs that support local neurons and guide neuronal growth into tumors. The development of feed-forward relationships between tumors and neurons allows tumors to use the perineural space as a sanctuary from therapy. Tumor denervation slows tumor growth in animal models, demonstrating the innervation dependence of growing tumors. Further in vitro and in vivo experiments have identified many of the secreted signaling molecules (e.g., acetylcholine, nerve growth factor) that are passed between neurons and cancer cells, as well as the major signaling pathways (e.g., MAPK/EGFR) involved in these trophic interactions. The molecules involved in these signaling pathways serve as potential biomarkers of disease. Additionally, new treatment strategies focus on using small molecules, receptor agonists, nerve-specific toxins, and surgical interventions to target tumors, neurons, and immune cells of the tumor microenvironment, thereby severing the interactions between tumors and surrounding neurons. This article discusses the mechanisms underlying the trophic relationships formed between neurons and tumors and explores the emerging therapies stemming from this work.

Matrix-Bound Nanovesicles: The Effects of Isolation Method upon Yield, Purity, and Function

Identification of matrix-bound nanovesicles (MBV) as ubiquitous components of the extracellular matrix (ECM) raises questions regarding their biologic functions and their potential theranostic application. Unlike liquid-phase extracellular vesicles (e.g., exosomes), MBV are tightly bound to the ECM, which makes their isolation and harvesting more challenging. The indiscriminate use of different methods to harvest MBV can alter or disrupt their structural and/or functional integrity. The objective of the present study was to compare the effect of various MBV harvesting methods upon yield, purity, and biologic activity. Combinations of four methods to solubilize the ECM (collagenase [COL], liberase [LIB], or proteinase K [PK] and nonenzymatic elution with potassium chloride) and four isolation methods (ultracentrifugation, ultrafiltration [UF], density barrier, and size exclusion chromatography [SEC]) were used to isolate MBV from urinary bladder-derived ECM. All combinations of solubilization and isolation methods allowed for the harvesting of MBV, however, distinct differences were noted. The highest yield, purity, cellular uptake, and biologic activity were seen with MBV isolated by a combination of liberase or collagenase followed by SEC. The combination of proteinase K and UF was shown to have detrimental effects on bioactivity. The results show the importance of selecting appropriate MBV harvesting methods for the characterization and evaluation of MBV and for analysis of their potential theranostic application. Impact statement Identification of matrix-bound nanovesicles (MBV) as ubiquitous components of the extracellular matrix (ECM) has raised questions regarding their biologic functions and their potential theranostic application. This study demonstrates that the harvesting methods used can result in samples with physical and biochemical properties that are unique to the isolation and solubilization methods used. Consequently, developing harvesting methods that minimize sample contamination with ECM remnants and/or solubilization agents will be essential in determining the theranostic potential of MBV in future studies.

The potential role of tumor-derived exosomes in diagnosis, prognosis, and response to therapy in cancer

INTRODUCTION

Small extracellular vesicles (sEV) produced by tumors and called TEX mediate communication and regulate the tumor microenvironment. As a 'liquid tumor biopsy' and with the ability to induce pro-tumor reprogramming, TEX offer a promising approach to monitoring cancer progression or response to therapy.

AREAS COVERED

TEX isolation from body fluids and separation by immunoaffinity capture from other EVs enables TEX molecular and functional characterization in vitro and in vivo. TEX carry membrane-bound PD-L1 and a rich cargo of other proteins and nucleic acids that reflect the tumor content and activity. TEX transfer this cargo to recipient cells, activating various molecular pathways and inducing pro-tumor transcriptional changes. TEX may interfere with immune therapies, and TEX plasma levels correlate with patients' responses to therapy. TEX induce local and systemic alterations in immune cells which may have a prognostic value.

EXPERT OPINION

TEX have a special advantage as potential cancer biomarkers. Their cargo emerges as a correlate of developing or progressing malignant disease; their phenotype mimics that of the tumor; and their functional reprogramming of immune cells provides a reading of the patients' immune status prior and post immunotherapy. Validation of TEX and T-cell-derived sEV as cancer biomarkers is an impending future task.

Glycan Node Analysis of Plasma-Derived Extracellular Vesicles

Blood plasma is a readily accessible source of extracellular vesicles (EVs), i.e., cell-secreted nanosized carriers that contain various biomolecules, including glycans. Previous studies have demonstrated that glycans play a major role in physiological and pathological processes, and certain plasma glycans have been associated with disease conditions. However, glycome studies have been limited by a lack of analytical techniques with the throughput capacity necessary to study hundreds of clinical samples. This study is the first to characterize the EV plasma glycome based on all major glycan classes. The results based on glycan node analysis revealed, as expected, that plasma-derived EVs have distinct glycan features from donor-matched whole plasma. Specifically, glycan nodes corresponding to those observed in chondroitin sulfate, dermatan sulfate, type I keratan sulfate, and type II keratan sulfate were enriched on EVs. The identification of specific differences in glycan features in plasma vs. plasma-derived EVs is relevant for understanding the physiological role of EVs and as a reference for future diagnostic studies. Additionally, the results indicate that EV glycan nodes do not substantially differ among a small set of healthy donors. These results lay the framework for the further evaluation of all EV glycan classes as diagnostic markers, therapeutic targets, and biologically active components in health and disease.

Use of Biomarkers and Imaging for Early Detection of Pancreatic Cancer

Pancreatic cancer remains one of the deadliest cancers worldwide, and it is typically diagnosed late, with a poor prognosis. Early detection is the most important underlying factor for improving the prognosis of pancreatic cancer patients. One of the most effective strategies for detecting cancers at an early stage is screening of the general population. However, because of the low incidence of pancreatic cancer in the general population, the stratification of subjects who need to undergo further examinations by invasive and expensive modalities is important. Therefore, minimally invasive modalities involving biomarkers and imaging techniques that would facilitate the early detection of pancreatic cancer are highly needed. Multiple types of new blood biomarkers have recently been developed, including unique post-translational modifications of circulating proteins, circulating exosomes, microRNAs, and circulating tumor DNA. We previously reported that circulating apolipoprotein A2 undergoes unique processing in the bloodstream of patients with pancreatic cancer and its precancerous lesions. Additionally, we recently demonstrated a new method for measuring pancreatic proton density in the fat fraction using a fat–water magnetic resonance imaging technique that reflects pancreatic steatosis. In this review, we describe recent developments in potential biomarkers and imaging modalities for the early detection and risk stratification of pancreatic cancer, and we discuss current strategies for implementing screening programs for pancreatic cancer.

Diagnostic and Therapeutic Applications of Exosomes in Cancer with a Special Focus on Head and Neck Squamous Cell Carcinoma (HNSCC)

Exosomes are nanovesicles part of a recently described intercellular communication system. Their properties seem promising as a biomarker in cancer research, where more sensitive monitoring and therapeutic applications are desperately needed. In the case of head and neck squamous cell carcinoma (HNSCC), overall survival often remains poor, although huge technological advancements in the treatment of this disease have been made. In the following review, diagnostic and therapeutic properties are highlighted and summarised. Impressive first results have been obtained but more research is needed to implement these innovative techniques into daily clinical routines.

Transcriptomic Analysis in Liquid Biopsy Identifies Circulating PCTAIRE-1 mRNA as a Biomarker in NSCLC

BACKGROUND/AIM

Circulating mRNA can be a useful source of cancer biomarkers. We took advantage of direct transcriptomic analysis in plasma RNA to identify novel mRNA markers for non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Plasma RNA from NSCLC patients and healthy individuals was profiled with cDNA-mediated annealing, selection, extension and ligation (DASL) microarrays. The microarray results were further validated in plasma RNA.

RESULTS

Through RNA profiling and online database mining, four gene transcripts were filtered as candidate markers of NSCLC. After validation, the PCTAIRE-1 transcript was identified as a circulating mRNA marker. The diagnostic potential of PCTAIRE-1 was evaluated by receiver operating characteristic curve analysis, which gave a sensitivity and specificity of 60% and 85%, respectively. In addition, high plasma PCTK1 levels were also correlated with poor progression-free survival (p=0.008).

CONCLUSION

Circulating mRNA can be profiled with the DASL assay. From the profile, PCTAIRE-1 RNA in the plasma we discovered as a novel diagnostic/prognostic biomarker and an indicator of poor survival in NSCLC patients.

From tumor microenvironment communicants to biomarker discovery: Selectively packaged extracellular vesicular cargoes in pancreatic cancer

Virtually all cells release various types of vesicles into the extracellular environment. These extracellular vesicles (EVs) transport molecular cargoes, performing as communicants for information exchange both within the tumor microenvironment (TME) and to distant organs. Thus, understanding the selective packaging of EV cargoes and the mechanistic impact of those cargoes - including metabolites, lipids, proteins, and/or nucleic acids - offers an opportunity to increase our knowledge of cancer biology and identify EV cargoes that might serve as cancer biomarkers in blood, saliva, or urine samples. In this review, we collect and organize recent advances in this field with an emphasis on pancreatic cancer (pancreatic adenocarcinoma, PDAC) and the concept that cells selectively package cargo into EVs. These studies demonstrate PDAC EV cargoes signal to reprogram and remodel the TME and impact distant organs. EV cargoes identified as potential PDAC diagnostic and prognostic biomarkers are summarized.

Melanoma cell-derived exosomes in plasma of melanoma patients suppress functions of immune effector cells

Melanoma patients’ plasma contains exosomes produced by malignant and normal cells. Plasma exosomes were isolated and separated by immunocapture into two fractions: melanoma cell-derived exosomes (MTEX) and normal cell-derived exosomes (non-MTEX). Immunosuppressive effects of MTEX on primary human immune cells were evaluated. Exosomes were isolated from plasma of 12 melanoma patients and six healthy donors (HDs). Expression levels of 19 immunoregulatory proteins in MTEX, non-MTEX and HDs exosomes were evaluated by on-bead flow cytometry. Functional/phenotypic changes induced in CD8⁺ T or natural killer (NK) cells by MTEX or non-MTEX were compared. Plasma protein levels were higher in patients than HDs (P < 0.0009). In patients, MTEX accounted for 23–66% of total exosomes. MTEX were enriched in immunosuppressive proteins (P = 0.03). MTEX, but not HDs exosomes, inhibited CD69 expression (P ≤ 0.0008), induced apoptosis (P ≤ 0.0009) and suppressed proliferation (P ≤ 0.002) in CD8⁺ T cells and downregulated NKG2D expression in NK cells (P = 0.001). Non-MTEX were enriched in immunostimulatory proteins (P = 0.002) and were only weakly immunosuppressive. Elevated MTEX/total exosome ratios and, surprisingly, non-MTEX ability to induce apoptosis of CD8⁺ T cells emerged as positive correlates of disease stage. MTEX emerge as the major mechanism of tumor-induced immune suppression and as an underestimated barrier to successful melanoma immunotherapy.

The Role of Exosomes in Pancreatic Cancer

Pancreatic cancer remains one of the deadliest cancers in the world, as a consequence of late diagnosis, early metastasis and limited response to chemotherapy, under which conditions the potential mechanism of pancreatic cancer progression requires further study. Exosomes are membrane vesicles which are important in the progression, metastasis and chemoresistance in pancreatic cancer. Additionally, they have been verified to be potential as biomarkers, targets and drug carriers for pancreatic cancer treatment. Thus, studying the role of exosomes in pancreatic cancer is significant. This paper focuses on the role of exosomes in the proliferation, metastasis and chemoresistance, as well as their potential applications for pancreatic cancer.

Advances in biomarker detection: Alternative approaches for blood-based biomarker detection

In the clinical setting, a blood sample is typically the starting point for biomarker search and discovery. Mass spectrometry (MS) is a highly sensitive and informative method for characterizing a very wide range of metabolites and proteins and is therefore a potentially powerful tool for biomarker discovery. However, the physicochemical characteristics of blood coupled with very large ranges of protein and metabolite concentrations present a significant technical obstacle for resolving and quantifying putative biomarkers by MS. Blood fractionation procedures are being developed to reduce the proteome/metabolome complexity and concentration ranges, allowing a greater diversity of analytes, including those at very low concentrations, to be quantified. In this chapter, several strategies for enriching and/or isolating specific blood components are summarized, including methods for the analysis of low and high molecular weight compounds, usually neglected in this type of assays, extracellular vesicles, and peripheral blood mononuclear cells (PBMCs). For each method, relevant practical information is presented for effective implementation.

Metabolic reprogramming of stromal fibroblasts by melanoma exosome microRNA favours a pre-metastatic microenvironment

Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear. We investigated whether Human Melanoma-derived exosomes (HMEX) could reprogram human adult dermal fibroblasts (HADF) and cause extracellular acidification. HMEX were isolated from supernatants of six melanoma cell lines (3 BRAF V600E mutant cell lines and 3 BRAF wild-type cell lines) using ultracentrifugation or Size Exclusion Chromatography (SEC). Rapid uptake of exosomes by HADF was demonstrated following 18 hours co-incubation. Exposure of HDAF to HMEX leads to an increase in aerobic glycolysis and decrease in oxidative phosphorylation (OXPHOS) in HADF, consequently increasing extracellular acidification. Using a novel immuno-biochip, exosomal miR-155 and miR-210 were detected in HMEX. These miRNAs were present in HMEX from all six melanoma cell lines and were instrumental in promoting glycolysis and inhibiting OXPHOS in tumour cells. Inhibition of miR-155 and miR-210 activity by transfection of miRNA inhibitors into HMEX reversed the exosome-induced metabolic reprogramming of HADF. The data indicate that melanoma-derived exosomes modulate stromal cell metabolism and may contribute to the creation of a pre-metastatic niche that promotes the development of metastasis.

Exosomes in lung cancer diagnosis and treatment. From the translating research into future clinical practice

Lung cancer is one of the main causes of cancer-related death worldwide. Despite advances in lung cancer pathophysiology, diagnosis and prognosis, a better understanding of the disease is strongly needed in order to establish novel diagnostic and therapeutic approaches that should improve treatment outcomes. Exosomes are a type of cell-secreted extracellular vesicles, which transfer a wide variety of biomolecules, such as proteins, mRNAs, microRNAs, and lipids, are implicated in intercellular communication and modulate tumor-host interactions. The potential value of exosomes and their contents in lung cancer diagnosis, prognosis and prediction of treatment outcome is supported by ample literature. Growing attention has been drawn specifically to the critical role of exosomal miRNAs in lung cancer pathogenesis and their potential clinical utility, especially due to their ability to modulate gene expression post-transcriptionally. Owing to their universal presence in the blood and other bodily fluids, exosomes are considered candidate biomarkers. Furthermore, their ability to deliver biomolecules and drugs to recipient cells renders them possible drug delivery vehicles in lung cancer. Here we review the pathological functions of exosomes in cancer and discuss their possible clinical utility as biomarkers and therapeutic agents in the management of lung cancer.

Contribution of the exosome-associated form of secreted endoplasmic reticulum aminopeptidase 1 to exosome-mediated macrophage activation

Macrophages secrete endoplasmic reticulum aminopeptidase 1 (ERAP1) in response to lipopolysaccharide (LPS) and interferon (IFN)-γ to enhance their phagocytic and nitric oxide (NO) synthetic activities. In this study, we found that a subset of secreted ERAP1 bound to exosomes released from LPS/IFN-γ-treated murine RAW264.7 macrophages compared to untreated cells. ERAP1-bound exosomes enhanced phagocytic and NO synthetic activities of macrophages more efficiently than free ERAP1 and exosomes derived from untreated cells. Deletion of the exon 10 coding sequence in ERAP1 gene resulted in loss of binding to exosomes. By comparing the activities of exosomes derived from wild-type and ERAP1 gene-deficient RAW264.7 cells, we observed that ERAP1 contributed to the exosome-dependent phagocytosis and NO synthesis of the cells. Upon stimulation of RAW264.7 cells with LPS/IFN-γ, TNF-α, IFN-γ, and CCL3 were also associated with the released exosomes. Analyses of cytokine function revealed that while CCL3 in the exosomes was crucial to the phagocytic activity of RAW264.7 cells, TNF-α and IFN-γ primarily contributed to the enhancement of NO synthesis. These results suggest that treatment with LPS/IFN-γ alters the physicochemical properties of exosomes released from macrophages in order to facilitate association with ERAP1 and several cytokines/chemokines. This leads to exosome-mediated enhancement of macrophage functions. It is possible that packaging effector molecules into exosomes upon inflammatory stimuli, facilitates the exertion of effective pathophysiological functions on macrophages. Our data provide the first evidence that ERAP1 associated with exosomes plays important roles in inflammatory processes via activation of macrophages.

Role of exosomes in hepatocellular carcinoma cell mobility alteration

Exosomes have gained increased research focus due to their key roles as messengers. The components of exosomes include proteins and RNAs that may be horizontally transferred between adjacent or distant cells. Hepatocellular carcinoma (HCC) is among the most malignant types of cancer worldwide, with exosomes implicated to play a crucial role in its regulation; however, the possible function of exosomes in modulating the motile ability of tumor cells and key molecules in HCC remain largely unknown. To investigate the regulatory effect of exosomes on the motile ability of HCC cells, exosomes from the culture medium of different HCC origins (high metastatic MHCC97-H and low metastatic MHCC97-L cells) were isolated for in vitro migration and invasion assays. The results indicated that the motile ability of MHCC97-L cells was significantly increased by pretreatment with MHCC97-H-derived exosomes when compared with MHCC97-L-exosome pretreatment (P<0.05). To further characterize the function of exosomes at the molecular level, protein profiling of exosomes from different cell origins was performed, which identified 129 proteins. Among these, adenylyl cyclase-associated protein 1, a protein implicated in HCC metastasis, was significantly enriched in exosomes from cells with high motile ability (P<0.05). The results of the present study validated the regulatory effect of exosomes on the motile ability of HCC cells. Furthermore, systematic analysis of the protein profiles of exosomes from different origins identified potential factors correlated with HCC metastasis, which may provide a basis for future functional analysis of exosomes regarding their involvement in cancer metastasis and recurrence.