High levels of exosomes expressing CD63 and caveolin-1 in plasma of melanoma patients

Exosomes: the future of biomarkers in medicine

Exosomes are nanovesicles secreted into the extracellular environment upon internal vesicle fusion with the plasma membrane. The molecular content of exosomes is a fingerprint of the releasing cell type and of its status. For this reason, and because they are released in easily accessible body fluids such as blood and urine, they represent a precious biomedical tool. A growing body of evidence suggests that exosomes may be used as biomarkers for the diagnosis and prognosis of malignant tumors. This article focuses on the exploitation of exosomes as diagnostic tools for human tumors and discusses possible applications of the same strategies to other pathologies, such as neurodegenerative diseases.

A novel "salting-out" procedure for the isolation of tumor-derived exosomes

The last decade has seen an exponential growth in the number of exosome-related publications. Although many of these studies have used exosomes from biological fluids (blood, and ascites or pleural effusions) the vast majority employed vesicles isolated from large volumes of tissue culture supernatants. While several techniques are available for their isolation, all require a significant reduction in volume to obtain sufficient concentrations for study. One approach is to concentrate the medium before proceeding with their isolation, however, these procedures are very time consuming and require specialized laboratory equipment. Here we provide a new and effective method for the isolation of tumor-derived exosomes based on "charge neutralization" with acetate. We show that titration of tissue culture supernatants with 0.1M acetate to pH4.75 results in immediate precipitation of virtually all the exosomes. The precipitated exosomes can be washed to remove residual media and are readily "resolubilized" upon resuspension in acetate-free buffer at neutral pH. This simple cost effective method significantly increases the yield of exosomes from an unlimited quantity of culture supernatants. Exosomes isolated by this technique are indistinguishable from exosomes recovered by direct ultracentrifugation.

Extracellular vesicles: emerging targets for cancer therapy

Extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, are released by almost all cell types, including tumour cells. Through transfer of their molecular contents, EVs are capable of altering the function of recipient cells. Increasing evidence suggests a key role for EV mediated intercellular communication in a variety of cellular processes involved in tumour development and progression, including immune suppression, angiogenesis, and metastasis. Aspects of EV biogenesis or function are therefore increasingly being considered as targets for anticancer therapy. Here, we summarise the current knowledge on the contributions of EVs to cancer pathogenesis and discuss novel therapeutic strategies to target EVs to prevent tumour growth and spread.

Predictive biomarkers for dasatinib treatment in melanoma

Dasatinib has anti-proliferative and anti-invasive effects in melanoma cell lines. However clinical trials have shown modest activity for dasatinib in metastatic melanoma. Although dasatinib targets SRC kinase, neither expression nor phosphorylation of SRC appears to predict response to dasatinib. Identification of predictive biomarkers for dasatinib may facilitate selection of melanoma patients who are more likely to respond to dasatinib. We correlated the anti-proliferative effects of dasatinib in 8 melanoma cell lines with expression of a previously identified 6-gene biomarker panel. We examined the relationship between response to dasatinib and expression of each gene at both the mRNA and protein level. Dasatinib inhibited growth in 3 of the 8 cell lines tested. mRNA expression of the panel of 6 biomarkers did not correlate with response, whilst elevated protein expression of ANXA1, CAV-1 and EphA2 correlated significantly with response to dasatinib in the panel of cell lines. Expression of ANXA1, CAV-1 and EphA2 were analysed in 124 melanoma samples by immunohistochemistry. ANXA1 protein was detected in 81 % (97/120) of tumours, CAV-1 in 44 % (54/122) of tumours and EphA2 in 74 % (90/121) of tumours. Thirty one % (35/113) of tumours tested expressed all three markers and 19 % (21/112) had moderate or strong expression of ANXA1, CAV-1 and EphA2. Seventeen percent (19/112) of melanoma samples were positive for SRC kinase expression, combined with high expression of ANXA1, CAV-1 and EphA2. This subgroup may represent a population of melanoma patients who would be more likely to derive clinical benefit from dasatinib treatment.

Natural killer cell-mediated shedding of ULBP2

UL16 binding proteins (ULBPs) are a family of cell surface proteins that are present in transformed and stressed cells and ligands for NKG2D. Soluble NKG2D ligands have been found in sera from cancer patients with their protein concentrations correlated with poor cancer prognosis. Here we show, for the first time, that human tumor cells lost their surface expression of ULBP2, but not ULBP1 and ULBP3, during NK cell-mediated cytolysis. In contrast to spontaneous shedding of NKG2D ligands, NK cytolysis-mediated shedding of ULBP2 was linked to target cell apoptosis, although both resulted from metalloproteinase cleavages. Inhibition of ULBP2 shedding by a metalloproteinase inhibitor BB-94 lead to reduced NK cell-mediated cytotoxicity and cytokine production. These results illustrate a regulation of NK cell effector functions through cytolysis-induced NKG2D ligand shedding. Consequently, compounds inhibiting NKG2D ligand shedding may offer therapeutic means to reduce excessive pathogenic NK cell activities.

The carrying pigeons of the cell: exosomes and their role in infectious diseases caused by human pathogens

Exosomes have recently been classified as the newest family members of 'bioactive vesicles' that function to promote intercellular communication. Long ignored and thought to be only a mechanism by which cellular waste is removed, exosomes have garnered a huge amount of interest in recent years as their critical functions in maintaining homeostasis through intercellular communication and also in different types of diseases have been demonstrated. Many groundbreaking studies of exosome functions have been performed in the cancer field and the infectious disease areas of study, revealing the importance and also the fascinating complexity of exosomal packaging, targeting, and functions. Selective packaging of exosomes in response to the type of infection, exosomal modulation of the immune response and host signaling pathways, exosomal regulation of pathogen spread, and effects of exosomes on the degree of pathogenesis have all been well documented. In this review, we provide a synthesis of the current understanding of the role of exosomes during infections caused by human pathogens and discuss the implications of these findings for a better understanding of pathogenic mechanisms and future therapeutic and diagnostic applications.

C. elegans ciliated sensory neurons release extracellular vesicles that function in animal communication

Cells release extracellular vesicles (ECVs) that play important roles in intercellular communication and may mediate a broad range of physiological and pathological processes. Many fundamental aspects of ECV biogenesis and signaling have yet to be determined, with ECV detection being a challenge and obstacle due to the small size (100 nm) of the ECVs. We developed an in vivo system to visualize the dynamic release of GFP-labeled ECVs. We show here that specific Caenorhabdidits elegans ciliated sensory neurons shed and release ECVs containing GFP-tagged polycystins LOV-1 and PKD-2. These ECVs are also abundant in the lumen surrounding the cilium. Electron tomography and genetic analysis indicate that ECV biogenesis occurs via budding from the plasma membrane at the ciliary base and not via fusion of multivesicular bodies. Intraflagellar transport and kinesin-3 KLP-6 are required for environmental release of PKD-2::GFP-containing ECVs. ECVs isolated from wild-type animals induce male tail-chasing behavior, while ECVs isolated from klp-6 animals and lacking PKD-2::GFP do not. We conclude that environmentally released ECVs play a role in animal communication and mating-related behaviors.

Gamma-glutamyltransferase fractions in human plasma and bile: characteristic and biogenesis

Total plasma gamma-glutamyltransferase (GGT) activity is a sensitive, non-specific marker of liver dysfunction. Four GGT fractions (b-, m-, s-, f-GGT) were described in plasma and their differential specificity in the diagnosis of liver diseases was suggested. Nevertheless fractional GGT properties have not been investigated yet. The aim of this study was to characterize the molecular nature of fractional GGT in both human plasma and bile. Plasma was obtained from healthy volunteers; whereas bile was collected from patients undergoing liver transplantation. Molecular weight (MW), density, distribution by centrifugal sedimentation and sensitivity to both detergent (deoxycholic acid) and protease (papain) were evaluated. A partial purification of b-GGT was obtained by ultracentrifugation. Plasma b-GGT fraction showed a MW of 2000 kDa and a density between 1.063-1.210 g/ml. Detergent converted b-GGT into s-GGT, whereas papain alone did not produce any effect. Plasma m-GGT and s-GGT showed a MW of 1,000 and 200 kDa, and densities between 1.006-1.063 g/ml and 1.063-1.210 g/ml respectively. Both fractions were unaffected by deoxycholic acid, while GGT activity was recovered into f-GGT peak after papain treatment. Plasma f-GGT showed a MW of 70 kDa and a density higher than 1.21 g/ml. We identified only two chromatographic peaks, in bile, showing similar characteristics as plasma b- and f-GGT fractions. These evidences, together with centrifugal sedimentation properties and immunogold electronic microscopy data, indicate that b-GGT is constituted of membrane microvesicles in both bile and plasma, m-GGT and s-GGT might be constituted of bile-acid micelles, while f-GGT represents the free-soluble form of the enzyme.

Exosome release and low pH belong to a framework of resistance of human melanoma cells to cisplatin

Intrinsic resistance to cytotoxic drugs has been a main issue in cancer therapy for decades. Microenvironmental acidity is a simple while highly efficient mechanism of chemoresistance, exploited through impairment of drug delivery. The latter is achieved by extracellular protonation and/or sequestration into acidic vesicles. This study investigates the importance of extracellular acidosis and nanovesicle (exosome) release in the resistance of human tumour cell to cisplatin (CisPt); in parallel to proton pump inhibitors (PPI) ability of interfering with these tumour cell features. The results showed that CisPt uptake by human tumour cells was markedly impaired by low pH conditions. Moreover, exosomes purified from supernatants of these cell cultures contained various amounts of CisPt, which correlated to the pH conditions of the culture medium. HPLC-Q-ICP-MS analysis revealed that exosome purified from tumour cell culture supernatants contained CisPt in its native form. PPI pre-treatment increased cellular uptake of CisPt, as compared to untreated cells, in an acidic-depend manner. Furthermore, it induced a clear inhibition of exosome release by tumour cells. Human tumours obtained from xenografts pretreated with PPI contained more CisPt as compared to tumours from xenografts treated with CisPt alone. Further analysis showed that in vivo PPI treatment induced a clear reduction in the plasmatic levels of tumour-derived exosomes which also contained lower level of CisPt. Altogether, these findings point to the identification of a double mechanism that human malignant melanoma use in resisting to a dreadful cellular poison such as cisplatin. This framework of resistance includes both low pH-dependent extracellular sequestration and an exosome-mediated elimination. Both mechanisms are markedly impaired by proton pump inhibition, leading to an increased CisPt-dependent cytotoxicity.

Exosomes: an overview of biogenesis, composition and role in ovarian cancer

Exosomes are tiny membrane-bound vesicles that are over produced by most proliferating cell types during normal and pathological states. Their levels are up-regulated during pregnancy and disease states such as cancer. Exosomes contain a wide variety of proteins, lipids, RNAs, non-transcribed RNAs, microRNAs and small RNAs that are representative to their cellular origin and shuttle from a donor cell to a recipient cell. From intercellular communication to tumor proliferation, exosomes carry out a diverse range of functions, both helpful and harmful. Useful as biomarkers, exosomes may be applicable in diagnostic assessments as well as cell-free anti-tumor vaccines. Exosomes of ovarian cancer contain different set of proteins and miRNAs compared to exosomes of normal, cancer-free individuals. These molecules may be used as multiple “barcode” for the development of a diagnostic tool for early detection of ovarian cancer.

Exosomes: an emerging factor in stress-induced immunomodulation

Cells constitutively release small (40-100 nm) vesicles known as exosomes, but their composition and function changes in response to a variety of physiological challenges, such as injury, infection, and disease. Advances in our understanding of the immunological relevance of exosomes have been made, however, few studies have explored their role in stress physiology. Exposure to a variety of acute stressors facilitates the efficacy of innate immune responses, but the mechanisms for these effects are not fully understood. Since exosomes are emerging as important inflammatory mediators, they likely exhibit a similar role when an organism is exposed to an acute stressor. Here, we review our current knowledge of the basic properties and immunological functions of exosomes and provide emerging data supporting the role of stress-modified exosomes in regulating the innate immune response, potentially enabling long-distance cellular communication and obviating the need for direct cell-to-cell contact.

Zwitterionic polymer-coated immunobeads for blood-based cancer diagnostics

Both total plasma and tumor-derived microvesicle (TMV)-associated miRNAs have been proposed as potential blood-based biomarkers for cancer diagnosis. However, there has been no comparison of the two types of miRNAs for biomarker discovery because of technological challenges of isolating TMVs from human plasma. The effective isolation of TMVs can be hardly achieved with conventional immunobead-based methods due to the high content of plasma proteins. In the current study, zwitterionic sulfobetaine-conjugated immunobeads are prepared using cluster of differentiation 83 (CD83) as a candidate protein marker for breast cancer-derived microvesicles. The zwitterionic immunobeads are more than 10-fold efficient for isolating TMVs from clinical plasma samples by suppressing nonspecific protein binding than conventional immunobeads. Early-stage breast cancer can be distinguished from benign breast disease by using the sulfobetaine-modified immunobeads, whereas conventional immunobeads show poor discriminatory performance. Further, we demonstrate that miRNAs in the form of TMVs offer a major improvement over total plasma miRNAs for early cancer detection. The analyses of miRNA expression levels show that in total, 6 miRNAs are significantly upregulated in the CD83-positive microvesicles of breast cancer patients, whereas differential miRNA expression is not detected on using total plasma RNA. The results indicate that our zwitterionic immunobead platform may constitute a powerful tool to identify circulating biomarkers and open a new avenue for highly sensitive blood-based cancer diagnostics.

Exosomes: a novel pathway of local and distant intercellular communication that facilitates the growth and metastasis of neoplastic lesions

Normal and diseased cells release bilayered membrane-bound nanovesicles into interstitial spaces and into bodily fluids. A subgroup of such microvesicles is called exosomes and is described in blood as 30 to 100 nm in diameter and as spherical to cup-shaped nanoparticles with specific surface molecular characteristics (eg, expression of the tetraspanins CD9, CD81, and CD63). Extracellular microvesicles provide local signals (eg, autocrine and paracrine) and distant endocrine signals to cells via the transfer of their contents, which include signal proteins, lipids, miRNAs, and functional mRNAs. Exosomes and related microvesicles also aid cells in exporting less-needed molecules and potentially harmful molecules, including drugs; in the case of neoplasia, the export of chemotherapeutic drugs may facilitate cellular chemoresistance. Cancers have adapted the exosome and related microvesicles as a pathway by which neoplastic cells communicate with each other (autocrine) and with nonneoplastic cells (paracrine and endocrine); via this pathway, cancer suppresses the immune system and establishes a fertile local and distant environment to support neoplastic growth, invasion, and metastases. Because exosomes mirror and bind to the cells from which they arise, they can be used for delivery of drugs, vaccines, and gene therapy, as biomarkers and targets. We review how exosomes and related extracellular microvesicles facilitate the progression and metastases of cancers and describe how these microvesicles may affect clinical care.

Pancreatic cancer diagnosis by free and exosomal miRNA

Patients with pancreatic adenocarcinoma (PaCa) have a dismal prognosis. This is in part due to late diagnosis prohibiting surgical intervention, which provides the only curative option as PaCa are mostly chemo- and radiation resistance. Hope is raised on a reliable non-invasive/minimally invasive diagnosis that is still missing. Recently two diagnostic options are discussed, serum MicroRNA (miRNA) and serum exosomes. Serum miRNA can be free or vesicle-, particularly, exosomes-enclosed. This review will provide an overview on the current state of the diagnostic trials on free serum miRNA and proceed with an introduction of exosomes that use as a diagnostic tool in serum and other body fluids has not received sufficient attention, although serum exosome miRNA in combination with protein marker expression likely will increase the diagnostic and prognostic power. By their crosstalk with host cells, which includes binding-initiated signal transduction, as well as reprogramming target cells via the transfer of proteins, mRNA and miRNA exosomes are suggested to become a most powerful therapeutics. I will discuss which hurdles have still to be taken as well as the different modalities, which can be envisaged to make therapeutic use of exosomes. PaCa are known to most intensely crosstalk with the host as apparent by desmoplasia and frequent paraneoplastic syndromes. Thus, there is hope that the therapeutic application of exosomes brings about a major breakthrough.

Exosomes in prostate cancer: putting together the pieces of a puzzle

Exosomes have been shown to act as mediators for cell to cell communication and as a potential source of biomarkers for many diseases, including prostate cancer. Exosomes are nanosized vesicles secreted by cells and consist of proteins normally found in multivesicular bodies, RNA, DNA and lipids. As a potential source of biomarkers, exosomes have attracted considerable attention, as their protein content resembles that of their cells of origin, even though it is noted that the proteins, miRNAs and lipids found in the exosomes are not a reflective stoichiometric sampling of the contents from the parent cells. While the biogenesis of exosomes in dendritic cells and platelets has been extensively characterized, much less is known about the biogenesis of exosomes in cancer cells. An understanding of the processes involved in prostate cancer will help to further elucidate the role of exosomes and other extracellular vesicles in prostate cancer progression and metastasis. There are few methodologies available for general isolation of exosomes, however validation of those methodologies is necessary to study the role of exosomal-derived biomarkers in various diseases. In this review, we discuss “exosomes” as a member of the family of extracellular vesicles and their potential to provide candidate biomarkers for prostate cancer.

Molecular lipidomics of exosomes released by PC-3 prostate cancer cells

The molecular lipid composition of exosomes is largely unknown. In this study, sophisticated shotgun and targeted molecular lipidomic assays were performed for in-depth analysis of the lipidomes of the metastatic prostate cancer cell line, PC-3, and their released exosomes. This study, based in the quantification of approximately 280 molecular lipid species, provides the most extensive lipid analysis of cells and exosomes to date. Interestingly, major differences were found in the lipid composition of exosomes compared to parent cells. Exosomes show a remarkable enrichment of distinct lipids, demonstrating an extraordinary discrimination of lipids sorted into these microvesicles. In particular, exosomes are highly enriched in glycosphingolipids, sphingomyelin, cholesterol, and phosphatidylserine (mol% of total lipids). Furthermore, lipid species, even of classes not enriched in exosomes, were selectively included in exosomes. Finally, it was found that there is an 8.4-fold enrichment of lipids per mg of protein in exosomes. The detailed lipid composition provided in this study may be useful to understand the mechanism of exosome formation, release and function. Several of the lipids enriched in exosomes could potentially be used as cancer biomarkers.

Exosomal and Non-Exosomal Transport of Extra-Cellular microRNAs in Follicular Fluid: Implications for Bovine Oocyte Developmental Competence

Cell-cell communication within the follicle involves many signaling molecules, and this process may be mediated by secretion and uptake of exosomes that contain several bioactive molecules including extra-cellular miRNAs. Follicular fluid and cells from individual follicles of cattle were grouped based on Brilliant Cresyl Blue (BCB) staining of the corresponding oocytes. Both Exoquick precipitation and differential ultracentrifugation were used to separate the exosome and non-exosomal fraction of follicular fluid. Following miRNA isolation from both fractions, the human miRCURY LNA™ Universal RT miRNA PCR array system was used to profile miRNA expression. This analysis found that miRNAs were present in both exosomal and non-exosomal fraction of bovine follicular fluid. We found 25 miRNAs differentially expressed (16 up and 9 down) in exosomes and 30 miRNAs differentially expressed (21 up and 9 down) in non-exosomal fraction of follicular fluid in comparison of BCB- versus BCB+ oocyte groups. Expression of selected miRNAs was detected in theca, granulosa and cumulus oocyte complex. To further explore the potential roles of these follicular fluid derived extra-cellular miRNAs, the potential target genes were predicted, and functional annotation and pathway analysis revealed most of these pathways are known regulators of follicular development and oocyte growth. In order to validate exosome mediated cell-cell communication within follicular microenvironment, we demonstrated uptake of exosomes and resulting increase of endogenous miRNA level and subsequent alteration of mRNA levels in follicular cells in vitro. This study demonstrates for the first time, the presence of exosome or non-exosome mediated transfer of miRNA in the bovine follicular fluid, and oocyte growth dependent variation in extra-cellular miRNA signatures in the follicular environment.

Comparative proteomics evaluation of plasma exosome isolation techniques and assessment of the stability of exosomes in normal human blood plasma

Exosomes are nanovesicles released by a variety of cells and are detected in body fluids including blood. Recent studies have highlighted the critical application of exosomes as personalized targeted drug delivery vehicles and as reservoirs of disease biomarkers. While these research applications have created significant interest and can be translated into practice, the stability of exosomes needs to be assessed and exosome isolation protocols from blood plasma need to be optimized. To optimize methods to isolate exosomes from blood plasma, we performed a comparative evaluation of three exosome isolation techniques (differential centrifugation coupled with ultracentrifugation, epithelial cell adhesion molecule immunoaffinity pull-down, and OptiPrep(TM) density gradient separation) using normal human plasma. Based on MS, Western blotting and microscopy results, we found that the OptiPrep(TM) density gradient method was superior in isolating pure exosomal populations, devoid of highly abundant plasma proteins. In addition, we assessed the stability of exosomes in plasma over 90 days under various storage conditions. Western blotting analysis using the exosomal marker, TSG101, revealed that exosomes are stable for 90 days. Interestingly, in the context of cellular uptake, the isolated exosomes were able to fuse with target cells revealing that they were indeed biologically active.

Microparticle drug sequestration provides a parallel pathway in the acquisition of cancer drug resistance

Expanding on our previous findings demonstrating that microparticles (MPs) spread cancer multidrug resistance, we now show that MPs sequester drugs, reducing the free drug concentration available to cells. MPs were isolated from drug-sensitive and drug-resistant sub-clones of a human breast adenocarcinoma cell line and from human acute lymphoblastic leukemia cells. MPs were assessed for size, mitochondria, RNA and phospholipid content, P-glycoprotein (P-gp) expression and orientation and ATPase activity relative to drug sequestration capacity. Of the drug classes examined, MPs sequestered the anthracycline class to a significant degree. The degree of sequestration was likely due to the size of MPs and thus the amount of cargo they contain, to which the anthracyclines bind. Moreover, a proportion of the P-gp present on MPs was inside-out in orientation, enabling it to influx drugs rather than its typical efflux function. This was confirmed by surface immunofluorescence and by assessment of drug-stimulated ATPase activity following MP permeabilization. Thus we determined that breast cancer MPs carried a proportion of their P-gp oriented inside-out, providing active sequestration within the microvesicular compartment. These results demonstrate a capacity for MPs to sequester chemotherapeutic drugs, which has a predominantly active sequestration component for MPs derived from drug-resistant cells and a predominantly passive component for MPs derived from drug-sensitive cells. This reduction in available drug concentration has potential to contribute to a parallel pathway and complements that of the intercellular transfer of P-gp. These findings lend further support to the role of MPs in limiting the successful management of cancer.

MicroRNA and protein profiling of brain metastasis competent cell-derived exosomes

Exosomes are small membrane vesicles released by most cell types including tumor cells. The intercellular exchange of proteins and genetic material via exosomes is a potentially effective approach for cell-to-cell communication and it may perform multiple functions aiding to tumor survival and metastasis. We investigated microRNA and protein profiles of brain metastatic (BM) versus non-brain metastatic (non-BM) cell-derived exosomes. We studied the cargo of exosomes isolated from brain-tropic 70W, MDA-MB-231BR, and circulating tumor cell brain metastasis-selected markers (CTC1BMSM) variants, and compared them with parental non-BM MeWo, MDA-MB-231P and CTC1P cells, respectively. By performing microRNA PCR array we identified one up-regulated (miR-210) and two down-regulated miRNAs (miR-19a and miR-29c) in BM versus non-BM exosomes. Second, we analyzed the proteomic content of cells and exosomes isolated from these six cell lines, and detected high expression of proteins implicated in cell communication, cell cycle, and in key cancer invasion and metastasis pathways. Third, we show that BM cell-derived exosomes can be internalized by non-BM cells and that they effectively transport their cargo into cells, resulting in increased cell adhesive and invasive potencies. These results provide a strong rationale for additional investigations of exosomal proteins and miRNAs towards more profound understandings of exosome roles in brain metastasis biogenesis, and for the discovery and application of non-invasive biomarkers for new therapies combating brain metastasis.

C-src enriched serum microvesicles are generated in malignant plasma cell dyscrasia

Plasma cell dyscrasias are immunosecretory disorders that can lead to hematological malignancies such as Multiple Myeloma (MM). MM accounts for 15% of all hematologic cancers, and those diagnosed with MM typically become severely ill and have a low life expectancy. Monoclonal immunoglobulin Free Light Chains (FLC) are present in the serum and urine of many patients with plasma cell diseases. The biological differences between monoclonal FLCs, produced under malignant or benign dyscrasias, has not yet been characterized. In the present study, we show that endothelial and heart muscle cell lines internalize kappa and lambda FLCs. After internalization, FLCs are rerouted in the extracellular space via microvesicles and exosomes that can be re-internalized in contiguous cells. Only FLCs secreted from malignant B Lymphocytes were carried in Hsp70, annexin V, and c-src positive vesicles. In both MM and AL Amyloidosis patients we observed an increase in microvesicle and exosome production. Isolated serum vesicles from MM, AL Amyloidosis and monoclonal gammopathy of undetermined significance (MGUS) patients contained FLCs. Furthermore MM and AL amyloidosis vesicles were strongly positive for Hsp70, annexin V, and c-src compared to MGUS and control patients. These are the first data implying that FLCs reroute via microvesicles in the blood stream, and also suggest a potential novel mechanism of c-src activation in plasma cell dyscrasia.

Extracellular vesicles as an emerging mechanism of cell-to-cell communication

The concept that extracellular vesicles may act as paracrine/endocrine effectors is based on the evidence that they are able to transport bioactive molecules between cells, either within a defined microenvironment or remotely, by entering the biologic fluids. Extracellular vesicles, including exosomes and microvesicles, may deliver lipids and various functional transcripts, released from the cell of origin, to target cells. Since extracellular vesicles contain defined patterns of mRNA, microRNA, long non-coding RNA, and occasionally genomic DNA, they may transfer genetic information which induces transient or persistent phenotypic changes in recipient cells. In this review, we will discuss potential physiologic and pathological implications of extracellular vesicles, as well as the diagnostic and therapeutic opportunities that they may provide.

Comparative marker analysis of extracellular vesicles in different human cancer types

Several cell types, including tumour cells, secrete extracellular vesicles (EVs), and tumour-derived EVs play a role in cancer initiation and progression. These vesicles include both a common set of membrane and cytosolic proteins and origin-specific subsets of proteins that likely correlated to cell type–associated functions. To confirm the presence of EVs in the preparations, researchers have identified so-called EV marker proteins, including the tetraspanin family proteins and such cytosolic proteins as heat shock 70 kDa protein 4 (HSP70) and tumour susceptibility gene 101 (TSG101). However, studies have shown that some EV markers are not always present in all EVs, which not only complicates the identification of EVs but also precludes the quantitative evaluation of EV proteins. Thus, it is strongly required to explore well-conserved EV marker proteins that are present at similar levels, regardless of their tissue or cellular origin. In this study, we compared the presence of 11 well-known EV marker proteins by immunoblotting using EVs isolated from 4 human prostate cell lines and 5 human breast cell lines, including cancer cells with different phenotypes. We found that all the tested EVs were positive for CD9 and CD81, with similar abundance that was irrespective of the EV origin. In contrast, other EV marker proteins, such as TSG101, Rab-5b and CD63, were detected in an inconsistent manner, depending on the origin of the EVs. Thus, we propose that the detection of CD9 and/or CD81 should ensure the presence of EVs.

In vivo identification of an HLA-G complex as ubiquitinated protein circulating in exosomes

The nonclassical human leukocyte antigen-G (HLA-G) is a tolerogenic molecule that can be released to the circulation by expressing cells. This molecule can form dimers but some other complexed HLA-G forms have been proposed to be present in vivo. Here, we further characterized these other complexed HLA-G forms in vivo. Ascitic and pleural exudates from patients were selected based on positivity for HLA-G by ELISA. Complexed HLA-G was detected in exosomes, which indicates an intracellular origin of these forms. 2D-PAGE analysis of exudates and isolated exosomes showed that these high molecular weight complexes were more heterogeneous than the HLA-G1 expressed by cell cultures. Treatment with deglycosylating enzymes did not change the molecular weight of HLA-G complexes. Immunoblot analysis of exudates and exosomes with an anti-ubiquitin antibody showed that at least some of these structures correspond to ubiquitinated HLA-G. HLA-G ubiquitination could be reproduced in vitro in HLA-G1-transfected cell lines, although with a lower modified/nonmodified protein proportion than in exudates. In summary, we demonstrate new circulating HLA-G forms in vivo that open a new perspective in the study of HLA-G function and analysis.

Exosomes released in vitro from Epstein-Barr virus (EBV)-infected cells contain EBV-encoded latent phase mRNAs

EBV is a human herpesvirus associated with a number of malignancies. Both lymphoblastoid cell lines (LCLs), and EBV-infected nasopharyngeal carcinoma (NPC) cells have been demonstrated to release exosomes containing the EBV-encoded latent membrane protein 1 (LMP1), and mature micro-RNAs (EBV-miRNAs). Here we analyze the EBV protein and nucleic acid content of exosomes from different EBV-infected cells (LCL, 721 and Daudi) and we show for the first time that exosomes released from LCLs and 721 also contain EBV-encoded latent phase mRNAs. This confirms and strengthens exosomes pathogenetic potential, and might provide insights for development of novel diagnostic and therapeutic strategies.

Tumor-cell-derived microvesicles as carriers of molecular information in cancer

PURPOSE OF REVIEW

Exosomes and microvesicles are secreted particles of 30-200  nm in diameter, delimited by a lipid bilayer and containing a wide range of membrane-bound or free proteins and nucleic acids (in particular mRNA and miRNA). Here, we review the properties of tumor-cell-derived microvesicles as carriers of molecular information in relation to cancer progression and promotion of metastasis.

RECENT FINDINGS

Microvesicles from tumor cells operate as signaling platforms that diffuse in the extracellular space to target cells in the microenvironment, modulating the interactions of tumor cells with stromal, inflammatory, dendritic, immune or vascular cells and priming the formation of the metastatic niche.

SUMMARY

Because of their stability, exosomes and microvesicles can be retrieved in bodily fluids as biomarkers for cancer detection and monitoring. They offer a range of molecular targets for controlling cell-cell interactions during invasion and metastasis.

First identification of Ewing's sarcoma-derived extracellular vesicles and exploration of their biological and potential diagnostic implications

BACKGROUND INFORMATION

Exosomes are small RNA- and protein-containing extracellular vesicles (EVs) that are thought to mediate hetero- and homotypic intercellular communication between normal and malignant cells.Tumour-derived exosomes are believed to promote re-programming of the tumour-associated stroma to favour tumour growth and metastasis. Currently, exosomes have been intensively studied in carcinomas. However, little is known about their existence and possible role in sarcomas.

RESULTS

Here, we report on the identification of vesicles with exosomal features derived from Ewing's sarcoma(ES), the second most common soft-tissue or bone cancer in children and adolescents. ES cell line-derived EV shave been isolated by ultracentrifugation and analysed by flow-cytometric assessment of the exosome-associated proteins CD63 and CD81 as well as by electron microscopy. They proved to contain ES-specific transcripts including EWS-FLI1, which were suitable for the sensitive detection of ES cell line-derived exosomes by qRT-PCRin a pre-clinical model for patient plasma. Microarray analysis of ES cell line-derived exosomes revealed that they share a common transcriptional signature potentially involved in G-protein-coupled signalling, neurotransmitter signalling and stemness.

CONCLUSIONS

In summary, our results imply that ES-derived exosomes could eventually serve as biomarkers for minimal residual disease diagnostics in peripheral blood and prompt further investigation of their potential biological role in modification of the ES-associated microenvironment

Exosomes reflect the hypoxic status of glioma cells and mediate hypoxia-dependent activation of vascular cells during tumor development

Hypoxia, or low oxygen tension, is a major regulator of tumor development and aggressiveness. However, how cancer cells adapt to hypoxia and communicate with their surrounding microenvironment during tumor development remain important questions. Here, we show that secreted vesicles with exosome characteristics mediate hypoxia-dependent intercellular signaling of the highly malignant brain tumor glioblastoma multiforme (GBM). In vitro hypoxia experiments with glioma cells and studies with patient materials reveal the enrichment in exosomes of hypoxia-regulated mRNAs and proteins (e.g., matrix metalloproteinases, IL-8, PDGFs, caveolin 1, and lysyl oxidase), several of which were associated with poor glioma patient prognosis. We show that exosomes derived from GBM cells grown at hypoxic compared with normoxic conditions are potent inducers of angiogenesis ex vivo and in vitro through phenotypic modulation of endothelial cells. Interestingly, endothelial cells were programmed by GBM cell-derived hypoxic exosomes to secrete several potent growth factors and cytokines and to stimulate pericyte PI3K/AKT signaling activation and migration. Moreover, exosomes derived from hypoxic compared with normoxic conditions showed increased autocrine, promigratory activation of GBM cells. These findings were correlated with significantly enhanced induction by hypoxic compared with normoxic exosomes of tumor vascularization, pericyte vessel coverage, GBM cell proliferation, as well as decreased tumor hypoxia in a mouse xenograft model. We conclude that the proteome and mRNA profiles of exosome vesicles closely reflect the oxygenation status of donor glioma cells and patient tumors, and that the exosomal pathway constitutes a potentially targetable driver of hypoxia-dependent intercellular signaling during tumor development.

Extracellular vesicles: biology and emerging therapeutic opportunities

Within the past decade, extracellular vesicles have emerged as important mediators of intercellular communication, being involved in the transmission of biological signals between cells in both prokaryotes and higher eukaryotes to regulate a diverse range of biological processes. In addition, pathophysiological roles for extracellular vesicles are beginning to be recognized in diseases including cancer, infectious diseases and neurodegenerative disorders, highlighting potential novel targets for therapeutic intervention. Moreover, both unmodified and engineered extracellular vesicles are likely to have applications in macromolecular drug delivery. Here, we review recent progress in understanding extracellular vesicle biology and the role of extracellular vesicles in disease, discuss emerging therapeutic opportunities and consider the associated challenges.

Timp1 interacts with beta-1 integrin and CD63 along melanoma genesis and confers anoikis resistance by activating PI3-K signaling pathway independently of Akt phosphorylation

BACKGROUND

Anoikis resistance is one of the abilities acquired along tumor progression. This characteristic is associated with metastasis development, since tumorigenic cells must survive independently of cell-matrix interactions in this process. In our laboratory, it was developed a murine melanocyte malignant transformation model associated with a sustained stressful condition. After subjecting melan-a melanocytes to 1, 2, 3 and 4 cycles of anchorage impediment, anoikis resistant cells were established and named 1C, 2C, 3C and 4C, respectively. These cells showed altered morphology and PMA independent cell growth, but were not tumorigenic, corresponding to pre-malignant cells. After limiting dilution of 4C pre-malignant cells, melanoma cell lines with different characteristics were obtained. Previous data from our group showed that increased Timp1 expression correlated with anoikis-resistant phenotype. Timp1 was shown to confer anchorage-independent growth capability to melan-a melanocytes and render melanoma cells more aggressive when injected into mice. However, the mechanisms involved in anoikis regulation by Timp1 in tumorigenic cells are not clear yet.

METHODS

The β1-integrin and Timp1 expression were evaluated by Western blotting and CD63 protein expression by flow cytometry using specific antibodies. To analyze the interaction among Timp1, CD63 and β1-integrin, immunoprecipitation assays were performed, anoikis resistance capability was evaluated in the presence or not of the PI3-K inhibitors, Wortmannin and LY294002. Relative expression of TIMP1 and CD63 in human metastatic melanoma cells was analyzed by real time PCR.

RESULTS

Differential association among Timp1, CD63 and β1-integrins was observed in melan-a melanocytes, 4C pre-malignant melanocytes and 4C11- and 4C11+ melanoma cells. Timp1 present in conditioned medium of melanoma cells rendered melan-a melanocytes anoikis-resistant through PI3-K signaling pathway independently of Akt activation. In human melanoma cell lines, in which TIMP1 and beta-1 integrin were also found to be interacting, TIMP1 and CD63 levels together was shown to correlate significantly with colony formation capacity.

CONCLUSIONS

Our results show that Timp1 is assembled in a supramolecular complex containing CD63 and β1-integrins along melanoma genesis and confers anoikis resistance by activating PI3-K signaling pathway, independently of Akt phosphorylation. In addition, our data point TIMP1, mainly together with CD63, as a potential biomarker of melanoma.

Caveolin-1 as a promoter of tumour spreading: when, how, where and why

Caveolae are non-clathrin invaginations of the plasma membrane in most cell types; they are involved in signalling functions and molecule trafficking, thus modulating several biological functions, including cell growth, apoptosis and angiogenesis. The major structural protein in caveolae is caveolin-1, which is known to act as a key regulator in cancer onset and progression through its role as a tumour suppressor. Caveolin-1 can also promote cell proliferation, survival and metastasis as well as chemo- and radioresistance. Here, we discuss recent findings and novel concepts that support a role for caveolin-1 in cancer development and its distant spreading. We also address the potential application of caveolin-1 in tumour therapy and diagnosis.

Emerging roles of extracellular vesicles in the adaptive response of tumour cells to microenvironmental stress

Cells are constantly subjected to various types of endogenous and exogenous stressful stimuli, which can cause serious and even permanent damage. The ability of a cell to sense and adapt to environmental alterations is thus vital to maintain tissue homeostasis during development and adult life. Here, we review some of the major phenotypic characteristics of the hostile tumour microenvironment and the emerging roles of extracellular vesicles in these events.

Exosomes as nucleic acid nanocarriers

Exosomes are nano-sized vesicles produced naturally by many cell types. They are specifically loaded with nucleic acid cargo, dependent on the exosome-producing cell and its homeostatic state. As natural intercellular shuttles of miRNA, exosomes influence an array of developmental, physiological and pathological processes in the recipient cell or tissue to which they can be selectively targeted by their tetraspanin surface-domains. By a review of current research, we illustrate here why exosomes are ideal nanocarriers for use in the targeted in vivo delivery of nucleic acids.

Imaging exosome transfer from breast cancer cells to stroma at metastatic sites in orthotopic nude-mouse models

Exosomes play an important role in cell-to-cell communication to promote tumor metastasis. In order to image the fate of cancer-cell-derived exosomes in orthotopic nude mouse models of breast cancer, we used green fluorescent protein (GFP)-tagged CD63, which is a general marker of exosomes. Breast cancer cells transferred their own exosomes to other cancer cells and normal lung tissue cells in culture. In orthotopic nude-mouse models, breast cancer cells secreted exosomes into the tumor microenvironment. Tumor-derived exosomes were incorporated into tumor-associated cells as well as circulating in the blood of mice with breast cancer metastases. These results suggest that tumor-derived exosomes may contribute to forming a niche to promote tumor growth and metastasis. Our results demonstrate the usefulness of GFP imaging to investigate the role of exosomes in cancer metastasis.

Roles of exosomes and microvesicles in disease pathogenesis

A variety of cells release membrane vesicles, such as exosomes and microvesicles (MVs), that are thought to play key roles in cell-cell communication, antigen presentation, and the spread of infectious agents throughout the body. There have been considerable efforts to use MVs as diagnostic or prognostic markers because their composition is reflective of minor physiological changes. Furthermore, recent studies demonstrate that MVs derived from infected cells and tumors contribute to disease pathogenesis. This review presents an overview of the potential roles of MVs with respect to clinical diagnosis and disease pathogenesis.

Decorin induces rapid secretion of thrombospondin-1 in basal breast carcinoma cells via inhibition of Ras homolog gene family, member A/Rho-associated coiled-coil containing protein kinase 1

Pathological neovascularization relies on an imbalance between potent proangiogenic agents and equally effective antiangiogenic cues. Collectively, these factors contribute to an angiogenic niche within the tumor microenvironment. Oncogenic events and hypoxia contribute to augmented levels of angiokines, and thereby activate the so-called angiogenic switch to promote aggressive tumorigenic and metastatic growth. Soluble decorin functions as a paracrine pan-inhibitor of receptor tyrosine kinases, such as Met and epidermal growth factor receptor, and thus is capable of suppressing angiogenesis under normoxia. This leads to noncanonical repression of hypoxia-inducible factor 1-alpha and vascular endothelial growth factor A (VEGFA), and concurrent induction of thrombospondin-1. The substantial induction of endogenous tumor cell-derived thrombospondin-1, a potent antiangiogenic effector, led us to the discovery of an unexpected secretory phenotype occurring very rapidly (within 5 min) after decorin treatment of the triple-negative basal breast carcinoma cell line MDA-MB-231. Surprisingly, the effect was not mediated by Met receptor antagonism, as initially hypothesized, but required epidermal growth factor receptor signaling to achieve swift and robust thrombospondin-1 release. Furthermore, this effect was ultimately dependent on the prompt degradation of Ras homolog gene family member A, via the 26S proteasome, leading to direct inactivation of Rho-associated coiled-coil containing protein kinase 1. The latter led to derepression of thrombospondin-1 secretion. Collectively, these data provide a novel mechanistic role for Rho-associated coiled-coil containing protein kinase 1, in addition to providing the first conclusive evidence of decorin exclusively targeting a receptor tyrosine kinase to achieve a specific effect. The overall effects of soluble decorin on the tumor microenvironment would cause an immediately-early as well as a sustained antiangiogenic response in vivo.

Neuronal exosomal miRNA-dependent translational regulation of astroglial glutamate transporter GLT1

Perisynaptic astrocytes express important glutamate transporters, especially excitatory amino acid transporter 2 (EAAT2, rodent analog GLT1) to regulate extracellular glutamate levels and modulate synaptic activation. In this study, we investigated an exciting new pathway, the exosome-mediated transfer of microRNA (in particular, miR-124a), in neuron-to-astrocyte signaling. Exosomes isolated from neuron-conditioned medium contain abundant microRNAs and small RNAs. These exosomes can be directly internalized into astrocytes and increase astrocyte miR-124a and GLT1 protein levels. Direct miR-124a transfection also significantly and selectively increases protein (but not mRNA) expression levels of GLT1 in cultured astrocytes. Consistent with our in vitro findings, intrastriatal injection of specific antisense against miR-124a into adult mice dramatically reduces GLT1 protein expression and glutamate uptake levels in striatum without reducing GLT1 mRNA levels. MiR-124a-mediated regulation of GLT1 expression appears to be indirect and is not mediated by its suppression of the putative GLT1 inhibitory ligand ephrinA3. Moreover, miR-124a is selectively reduced in the spinal cord tissue of end-stage SOD1 G93A mice, the mouse model of ALS. Subsequent exogenous delivery of miR-124a in vivo through stereotaxic injection significantly prevents further pathological loss of GLT1 proteins, as determined by GLT1 immunoreactivity in SOD1 G93A mice. Together, our study characterized a new neuron-to-astrocyte communication pathway and identified miRNAs that modulate GLT1 protein expression in astrocytes in vitro and in vivo.

MARCKS-ED peptide as a curvature and lipid sensor

Membrane curvature and lipid composition regulates important biological processes within a cell. Currently, several proteins have been reported to sense and/or induce membrane curvatures, e.g., Synaptotagmin-1 and Amphiphysin. However, the large protein scaffold of these curvature sensors limits their applications in complex biological systems. Our interest focuses on identifying and designing peptides that can sense membrane curvature based on established elements observed in natural curvature-sensing proteins. Membrane curvature remodeling also depends on their lipid composition, suggesting strategies to specifically target membrane shape and lipid components simultaneously. We have successfully identified a 25-mer peptide, MARCKS-ED, based on the effector domain sequence of the intracellular membrane protein myristoylated alanine-rich C-kinase substrate that can recognize PS with preferences for highly curved vesicles in a sequence-specific manner. These studies further contribute to the understanding of how proteins and peptides sense membrane curvature, as well as provide potential probes for membrane shape and lipid composition.

The role of proteomics in prostate cancer research: biomarker discovery and validation

PURPOSE

Prostate Cancer (PCa) represents the second most frequent type of tumor in men worldwide. Incidence increases with patient age and represents the most important risk factor. PCa is mostly characterized by indolence, however in a small percentage of cases (3%) the disease progresses to a metastatic state. To date, the most important issue concerning PCa research is the difficulty in distinguishing indolent from aggressive disease. This problem frequently results in low-grade PCa patient overtreatment and, in parallel; an effective treatment for distant and aggressive disease is not yet available.

RESULT

Proteomics represents a promising approach for the discovery of new biomarkers able to improve the management of PCa patients. Markers more specific and sensitive than PSA are needed for PCa diagnosis, prognosis and response to treatment. Moreover, proteomics could represent an important tool to identify new molecular targets for PCa tailored therapy. Several possible PCa biomarkers sources, each with advantages and limitations, are under investigation, including tissues, urine, serum, plasma and prostatic fluids. Innovative high-throughput proteomic platforms are now identifying and quantifying new specific and sensitive biomarkers for PCa detection, stratification and treatment. Nevertheless, many putative biomarkers are still far from being applied in clinical practice.

CONCLUSIONS

This review aims to discuss the recent advances in PCa proteomics, emphasizing biomarker discovery and their application to clinical utility for diagnosis and patient stratification.

Tumor-derived microvesicles: the metastasomes

Metastasis is the leading cause of cancer death, yet it is mechanistically considered a very inefficient process suggesting the presence of some sort of (e.g. systemic) routes for fuelling the process. The pre-metastatic niche formation is described as one such metastasis promoting route. Now, the emerging potentials of tumor-derived microvesicles (TDMVs), not only in formulating the pre-metastatic niche, but also conferring neoplastic phenotypes onto normal cells, has integrated new concepts into the field. Here, we note as an ancillary proposition that, exerting functional disturbances in other sites, TDMVs (we have termed them metastasomes) may aid foundation of the secondary lesions via two seemingly interrelated models: (i) tumor-organ-training (TOTr), training a proper niche for the growth of the disseminated tumor cells; (ii) tumor-organ-targeting (TOTa), contribution to the propagation of the transformed phenotype via direct or indirect (TOTr-mediated disturbed stroma) transformation and/or heightened growth/survival states of the normal resident cells in the secondary organs. Respecting the high content of the RNA molecules (particularly microRNAs) identified in the secretory MVs, they may play crucial parts in such "malignant trait" spreading system. That is, the interactions between tumor tissue-specific RNA signatures, being transferred via metastasomes, and the cell-type/tissue-specific RNA stockrooms in other areas may settle a unique outcome in each organ. Thus, serving as tumor-organ matchmakers, the RNA molecules may also play substantial roles in the seeding and tropism of the process.

RNA trafficking by acute myelogenous leukemia exosomes

Extrinsic signaling cues in the microenvironment of acute myelogenous leukemia (AML) contribute to disease progression and therapy resistance. Yet, it remains unknown how the bone marrow niche in which AML arises is subverted to support leukemic persistence at the expense of homeostatic function. Exosomes are cell membrane-derived vesicles carrying protein and RNA cargoes that have emerged as mediators of cell-cell communication. In this study, we examined the role of exosomes in developing the AML niche of the bone marrow microenvironment, investigating their biogenesis with a focus on RNA trafficking. We found that both primary AML and AML cell lines released exosome-sized vesicles that entered bystander cells. These exosomes were enriched for several coding and noncoding RNAs relevant to AML pathogenesis. Furthermore, their uptake by bone marrow stromal cells altered their secretion of growth factors. Proof-of-concept studies provided additional evidence for the canonical functions of the transferred RNA. Taken together, our findings revealed that AML exosome trafficking alters the proliferative, angiogenic, and migratory responses of cocultured stromal and hematopoietic progenitor cell lines, helping explain how the microenvironmental niche becomes reprogrammed during invasion of the bone marrow by AML.

Defining a new role of GW182 in maintaining miRNA stability

GW182 binds to Argonaute (AGO) proteins and has a central role in miRNA-mediated gene silencing. Using lentiviral shRNA-induced GW182 knockdown in HEK293 cells, this study identifies a new role of GW182 in regulating miRNA stability. Stably knocking down GW182 or its paralogue TNRC6B reduces transfected miRNA-mimic half-lives. Replenishment of GW182 family proteins, as well as one of its domain Δ12, significantly restores the stability of transfected miRNA-mimic. GW182 knockdown reduces miRNA secretion via secretory exosomes. Targeted siRNA screening identifies a 3'-5' exoribonuclease complex responsible for the miRNA degradation only when GW182 is knocked down. Immunoprecipitation further confirms that the presence of GW182 in the RISC complex is critical in protecting Argonaute-bound miRNA.

Identifying mRNA, microRNA and protein profiles of melanoma exosomes

BACKGROUND

Exosomes are small membranous vesicles secreted into body fluids by multiple cell types, including tumor cells, and in various disease conditions. Tumor exosomes contain intact and functional mRNAs, small RNAs (including miRNAs), and proteins that can alter the cellular environment to favor tumor growth. Molecular profiling may increase our understanding of the role of exosomes in melanoma progression and may lead to discovery of useful biomarkers.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, we used mRNA array profiling to identify thousands of exosomal mRNAs associated with melanoma progression and metastasis. Similarly, miRNA array profiling identified specific miRNAs, such as hsa-miR-31, -185, and -34b, involved in melanoma invasion. We also used proteomic analysis and discovered differentially expressed melanoma exosomal proteins, including HAPLN1, GRP78, syntenin-1, annexin A1, and annexin A2. Importantly, normal melanocytes acquired invasion ability through molecules transported in melanoma cell-derived exosomes.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that melanoma-derived exosomes have unique gene expression signatures, miRNA and proteomics profiles compared to exosomes from normal melanocytes. To the best of our knowledge, this is the first in-depth screening of the whole transcriptome/miRNome/proteome expression in melanoma exosomes. These results provide a starting point for future more in-depth studies of tumor-derived melanoma exosomes, which will aid our understanding of melanoma biogenesis and new drug-targets that may be translated into clinical applications, or as non-invasive biomarkers for melanoma.

Immune surveillance properties of human NK cell-derived exosomes

Exosomes are nanovesicles released by normal and tumor cells, which are detectable in cell culture supernatant and human biological fluids, such as plasma. Functions of exosomes released by "normal" cells are not well understood. In fact, several studies have been carried out on exosomes derived from hematopoietic cells, but very little is known about NK cell exosomes, despite the importance of these cells in innate and adaptive immunity. In this paper, we report that resting and activated NK cells, freshly isolated from blood of healthy donors, release exosomes expressing typical protein markers of NK cells and containing killer proteins (i.e., Fas ligand and perforin molecules). These nanovesicles display cytotoxic activity against several tumor cell lines and activated, but not resting, immune cells. We also show that NK-derived exosomes undergo uptake by tumor target cells but not by resting PBMC. Exosomes purified from plasma of healthy donors express NK cell markers, including CD56+ and perforin, and exert cytotoxic activity against different human tumor target cells and activated immune cells as well. The results of this study propose an important role of NK cell-derived exosomes in immune surveillance and homeostasis. Moreover, this study supports the use of exosomes as an almost perfect example of biomimetic nanovesicles possibly useful in future therapeutic approaches against various diseases, including tumors.

Comparison of the influence of photodynamic reaction on the Me45 and MEWO cell lines in vitro

Aim of the study

Photodynamic therapy (PDT) is an approved, minimally invasive and highly selective therapeutic approach to a variety of tumors. It is based on specific photosensitizer accumulation in the tumor tissue, followed by irradiation with visible light. The photochemical interactions of the photosensitizer, light and molecular oxygen produce singlet oxygen and other reactive oxygen forms. The imbalance between ROS generation and antioxidant capacity of the body gives rise to oxidative stress in the cell, which initiates cell death in PDT. The aim of this study was to investigate the effect of photodynamic reactions in human melanoma cell lines.

Material and methods

Photofrin^® (Ph) was used for the photodynamic reaction in vitro as a photosensitizer. The primary cell line was MEWO cell line (granular fibroblasts), derived from a human melanoma. As a recurrent cell line we used Me45 cell line, derived from a lymph node metastasis of skin melanoma. We compared cell viability (MTT assay) to determine the effectiveness of applied therapy. The intracellular distribution of photosensitizer (Photofrin) and localization of mitochondria (Mito-Tracker Green) were detected by confocal microscopy.

Results

We observed that Me45 and MEWO cell viability was dependent on the time of incubation after irradiation. In the recurrent cell line Ph accumulated mainly in the mitochondrial membranes and in MEWO cells also in the cytoplasm. The primary melanoma cell line exhibited significantly reduced cellular proliferation (below 50%) after photodynamic reaction with Ph.

Conclusions

The applied photodynamic reaction was more effective in primary melanoma cells. Additionally, mitochondrial localization of Ph can lead to disturbances of mitochondrial transmembrane potential and finally to release of apoptotic proteins.