Differentiation of tumour-promoting stromal myofibroblasts by cancer exosomes. Oncogene. 2015;34:290-302. [PMID: 24441045 DOI: 10.1038/onc.2013.560]

Extracellular vesicles: their role in cancer biology and epithelial-mesenchymal transition

Cell-cell communication is critical across an assortment of physiological and pathological processes. Extracellular vesicles (EVs) represent an integral facet of intercellular communication largely through the transfer of functional cargo such as proteins, messenger RNAs (mRNAs), microRNA (miRNAs), DNAs and lipids. EVs, especially exosomes and shed microvesicles, represent an important delivery medium in the tumour micro-environment through the reciprocal dissemination of signals between cancer and resident stromal cells to facilitate tumorigenesis and metastasis. An important step of the metastatic cascade is the reprogramming of cancer cells from an epithelial to mesenchymal phenotype (epithelial-mesenchymal transition, EMT), which is associated with increased aggressiveness, invasiveness and metastatic potential. There is now increasing evidence demonstrating that EVs released by cells undergoing EMT are reprogrammed (protein and RNA content) during this process. This review summarises current knowledge of EV-mediated functional transfer of proteins and RNA species (mRNA, miRNA, long non-coding RNA) between cells in cancer biology and the EMT process. An in-depth understanding of EVs associated with EMT, with emphasis on molecular composition (proteins and RNA species), will provide fundamental insights into cancer biology.

Extracellular vesicles in the tumor microenvironment: Therapeutic resistance, clinical biomarkers, and targeting strategies

Numerous studies have proved that cell-nonautonomous regulation of neoplastic cells is a distinctive and essential characteristic of tumorigenesis. Two way communications between the tumor and the stroma, or within the tumor significantly influence disease progression and modify treatment responses. In the tumor microenvironment (TME), malignant cells utilize paracrine signaling initiated by adjacent stromal cells to acquire resistance against multiple types of anticancer therapies, wherein extracellular vesicles (EVs) substantially promote such events. EVs are nanoscaled particles enclosed by phospholipid bilayers, and can mediate intercellular communications between cancerous cells and the adjacent microenvironment to accelerate pathological proceeding. Here we review the most recent studies of EV biology and focus on key cell lineages of the TME and their EV cargoes that are biologically active and responsible for cancer resistance, including proteins, RNAs, and other potentially essential components. Since EVs are emerging as novel but critical elements in establishing and maintaining hallmarks of human cancer, timely and insightful understanding of their molecular properties and functional mechanisms would pave the road for clinical diagnosis, prognosis, and effective targeting in the global landscape of precision medicine. Further, we address the potential of EVs as promising biomarkers in cancer clinics and summarize the technical improvements in EV preparation, analysis, and imaging. We highlight the practical issues that should be exercised with caution to guide the development of targeting agents and therapeutic methodologies to minimize cancer resistance driven by EVs, thereby allowing to effectively control the early steps of disease exacerbation.

Small extracellular vesicles secreted from senescent cells promote cancer cell proliferation through EphA2

Cellular senescence prevents the proliferation of cells at risk for neoplastic transformation. However, the altered secretome of senescent cells can promote the growth of the surrounding cancer cells. Although extracellular vesicles (EVs) have emerged as new players in intercellular communication, their role in the function of senescent cell secretome has been largely unexplored. Here, we show that exosome-like small EVs (sEVs) are important mediators of the pro-tumorigenic function of senescent cells. sEV-associated EphA2 secreted from senescent cells binds to ephrin-A1, that is, highly expressed in several types of cancer cells and promotes cell proliferation through EphA2/ephrin-A1 reverse signalling. sEV sorting of EphA2 is increased in senescent cells because of its enhanced phosphorylation resulting from oxidative inactivation of PTP1B phosphatase. Our results demonstrate a novel mechanism of reactive oxygen species (ROS)-regulated cargo sorting into sEVs, which is critical for the potentially deleterious growth-promoting effect of the senescent cell secretome.

Although senescent cell secretome can promote the growth of surrounding cancer cells, the role of extracellular vesicles in this process has not been well understood. Here the authors show that ROS increase the sorting of EphA2 into extracellular vesicles in senescent cells, which promotes proliferation of cancer cells.

Crosstalk between tongue carcinoma cells, extracellular vesicles, and immune cells in in vitro and in vivo models

The crosstalk between immune cells, cancer cells, and extracellular vesicles (EVs) secreted by cancer cells remains poorly understood. We created three-dimensional (3D) cell culture models using human leiomyoma discs and Myogel to study the effects of immune cells on highly (HSC-3) and less (SCC-25) invasive oral tongue squamous cell carcinoma (OTSCC) cell lines. Additionally, we studied the effects of EVs isolated from these cell lines on the cytotoxicity of CD8⁺ T and NK cells isolated from three healthy donors. Our analysis included the effects of these EVs on innate immunity in zebrafish larvae. Activated immune cells significantly decreased the proliferation of both OTSCC cell lines and associated with a diminished invasion area of HSC-3 cells. In general, EVs from SCC-25 increased the cytotoxic activity of CD8⁺ T and NK cells more than those from HSC-3 cells. However, this effect varied depending on the source and the immune and cancer cell subgroups. In zebrafish, the amount of IL-13 mRNA was decreased by SCC-25 EVs. This study describes promising in vitro and in vivo models to investigate interactions between immune cells, cancer cells, and EVs.

MYC Mediates Large Oncosome-Induced Fibroblast Reprogramming in Prostate Cancer

Communication between cancer cells and the tumor microenvironment results in the modulation of complex signaling networks that facilitate tumor progression. Here, we describe a new mechanism of intercellular communication originating from large oncosomes (LO), which are cancer cell-derived, atypically large (1-10 μm) extracellular vesicles (EV). We demonstrate that, in the context of prostate cancer, LO harbor sustained AKT1 kinase activity, nominating them as active signaling platforms. Active AKT1 was detected in circulating EV from the plasma of metastatic prostate cancer patients and was LO specific. LO internalization induced reprogramming of human normal prostate fibroblasts as reflected by high levels of α-SMA, IL6, and MMP9. In turn, LO-reprogrammed normal prostate fibroblasts stimulated endothelial tube formation in vitro and promoted tumor growth in mice. Activation of stromal MYC was critical for this reprogramming and for the sustained cellular responses elicited by LO, both in vitro and in vivo in an AKT1-dependent manner. Inhibition of LO internalization prevented activation of MYC and impaired the tumor-supporting properties of fibroblasts. Overall, our data show that prostate cancer-derived LO powerfully promote establishment of a tumor-supportive environment by inducing a novel reprogramming of the stroma. This mechanism offers potential alternative options for patient treatment. Cancer Res; 77(9); 2306-17. ©2017 AACR.

Predictive role of GSTP1-containing exosomes in chemotherapy-resistant breast cancer

Anthracycline/taxane-based chemotherapy regimens are usually used as neoadjuvant chemotherapies to decrease tumour size and prevent metastasis of advanced breast cancer. However, patients have a high risk of developing chemo-resistance during treatment through still unknown mechanisms. Glutathione S-transferase P1 (GSTP1), which belongs to the family of phase II metabolic enzymes, has been reported to function in detoxifying several anti-cancer drugs by conjugating them with glutathione. Previous studies have identified GSTP1 as a predictor of prognosis and chemo-resistance in breast cancer patients, but the mechanisms governing GSTP1-dependent drug resistance are still unclear. We have found that GSTP1 expression is much higher in adriamycin-resistant cells and their corresponding exosomes. The role of GSTP1-containing exosomes in conferring drug resistance was analysed through cell apoptosis and immunofluorescence staining assays. Furthermore, we analysed 42 cases of paired breast cancer tissues collected before and after anthracycline/taxane-based neoadjuvant chemotherapy by immunohistochemistry. Higher GSTP1 expression was shown in the progressive disease (PD)/stable disease (SD) group than in the partial response (PR)/complete response (CR) group both in the samples collected before and after the chemotherapy treatment. Interestingly, GSTP1 partly re-localized from the cell nucleus to the cytoplasm upon treatment, and similar results were obtained for the exosomal marker Tumour susceptibility gene 101 protein (TSG101), which also increased in the cytoplasm after chemotherapy. After analysing the serum exosomes of 30 patients treated with anthracycline/taxane-based neoadjuvant chemotherapy, we discovered that the levels of GSTP1 in exosomes from patients in the PD/SD group were significantly higher than those in the PR/CR group. Here, for the first time, we investigated a novel role for GSTP1-containing exosomes and their capability to transfer drug resistance and evaluated their clinical use in predicting chemo-resistance.

Characterization of exosomal RNAs derived from human gastric cancer cells by deep sequencing

Exosomes secreted from the cell to the extracellular environment play an important role in intercellular communication. Next-generation sequencing technology, which has achieved great development recently, allows us to detect more complete data and gain even deeper analyses of RNA transcriptomes. In our research, we extracted exosomes from different gastric cancer cell lines and immortalized normal gastric mucosal epithelial cell line and examined the amounts of exosomal proteins and RNAs. Our data showed that the secreted amount of cancer cell-derived exosomes, which contain proteins and RNAs, was much higher than that of normal cell-derived exosomes. Moreover, next-generation sequencing technology confirmed the presence of small non-coding RNAs in exosomes. Based on publicly available databases, we classified small non-coding RNAs. According to the microRNA profiles of exosomes, hsa-miR-21-5p and hsa-miR-30a-5p were two of the most abundant sequences among all libraries. The expression levels of the two microRNAs, miR-100 and miR-148a, in exosomes were validated through reverse transcription polymerase chain reaction. The reverse transcription polymerase chain reaction result, consistent with the trend of sequencing result, indicated a significant difference in exosomes between gastric cancer and gastric mucosal epithelial cell lines. We also predicted novel microRNA candidates but they need to be validated. This research provided an atlas of small non-coding RNA in exosomes and may make a little contribution to the understanding of exosomal RNA composition and finding parts of differential expression of RNAs in exosomes.

Morphological and immunohistochemical characterization of spontaneous endometriosis in rhesus macaques (Macaca mulatta)

Several cases of spontaneous endometriosis in middle-aged to old rhesus macaques (Macaca mulatta) from the breeding colony of the German Primate Center were thoroughly characterized with regards to anatomical distribution and macroscopic appearance, histological differentiation and immunohistochemical profile including somatic markers, hormonal receptors, and proliferation indices. More than half of the examined animals (five of nine) were directly related to one breeding male, supporting a strong genetic predisposition. Histologically, four different types of endometriotic lesions, depending on the degree of ectopic endometrial gland and stromal differentiation (well differentiated, purely stromal, mixed differentiation, poorly differentiated), could be constantly identified within all animals. Immunohistochemistry (IHC) of cytokeratin (CK), vimentin, smooth muscle actin (SMA), desmin, estrogen (ER), and progesterone (PR) receptors as well as of the nuclear proteins Ki67 and p53 revealed varying staining patterns in the four different types of endometriosis differentiation and compared to normal endometrium. Purely stromal, mixed, or poorly differentiated lesions, especially, showed additional cytokeratin-positive stromal cells, whereas epithelial cells of endometriosis with mixed or poor differentiation increasingly expressed mesenchymal markers (vimentin, SMA). Hormonal receptor and Ki67 expression in well-differentiated endometriotic lesions mostly reflected that of normal endometrial tissue according to the cyclic phase of the animal, while the expression gradually diminished with decreasing grade of differentiation. However, increased nuclear accumulations of p53 antigen could only be continuously detected in epithelial cells of mixed or poorly differentiated endometriosis. Altogether, these findings support the pathogenetic theory of coelomic metaplasia, since the expression profiles of somatic markers in less differentiated forms closely resembled that of mesothelial cells. Thus, the four different histological types of endometriosis might display subsequent grades of differentiation in the course of time, with poorly differentiated types representing newly formed, immature lesions and well-differentiated types being older, fully differentiated forms, rather than being the outcome of dedifferentiation processes.

Stemness in Cancer: Stem Cells, Cancer Stem Cells, and Their Microenvironment

Stemness combines the ability of a cell to perpetuate its lineage, to give rise to differentiated cells, and to interact with its environment to maintain a balance between quiescence, proliferation, and regeneration. While adult Stem Cells display these properties when participating in tissue homeostasis, Cancer Stem Cells (CSCs) behave as their malignant equivalents. CSCs display stemness in various circumstances, including the sustaining of cancer progression, and the interaction with their environment in search for key survival factors. As a result, CSCs can recurrently persist after therapy. In order to understand how the concept of stemness applies to cancer, this review will explore properties shared between normal and malignant Stem Cells. First, we provide an overview of properties of normal adult Stem Cells. We thereafter elaborate on how these features operate in CSCs. We then review the organization of microenvironment components, which enables CSCs hosting. We subsequently discuss Mesenchymal Stem/Stromal Cells (MSCs), which, although their stemness properties are limited, represent essential components of the Stem Cell niche and tumor microenvironment. We next provide insights of the therapeutic strategies targeting Stem Cell properties in tumors and the use of state-of-the-art techniques in future research. Increasing our knowledge of the CSCs microenvironment is key to identifying new therapeutic solutions.

Extracellular Vesicles: Unique Intercellular Delivery Vehicles

Extracellular vesicles (EVs) are a heterogeneous collection of membrane-bound carriers with complex cargoes including proteins, lipids, and nucleic acids. While the release of EVs was previously thought to be only a mechanism to discard nonfunctional cellular components, increasing evidence implicates EVs as key players in intercellular and even interorganismal communication. EVs confer stability and can direct their cargoes to specific cell types. EV cargoes also appear to act in a combinatorial manner to communicate directives to other cells. This review focuses on recent findings and knowledge gaps in the area of EV biogenesis, release, and uptake. In addition, we highlight examples whereby EV cargoes control basic cellular functions, including motility and polarization, immune responses, and development, and contribute to diseases such as cancer and neurodegeneration.

The role of exosomes in cancer metastasis

Exosomes are small membrane vesicles with a size ranging from 40 to 100nm. They can serve as functional mediators in cell interaction leading to cancer metastasis. Metastasis is a complex multistep process of cancer cell invasion, survival in blood vessels, attachment to and colonization of the host organ. Exosomes influence every step of this cascade and can be targeted by oncological treatment. This review highlights the role of exosomes in the various steps of the metastatic cascade and how exosome dependent pathways can be targeted as therapeutic approach or used for liquid biopsies.

RAB27A, RAB27B and VPS36 are downregulated in advanced prostate cancer and show functional relevance in prostate cancer cells

Paracrine and long-range signaling via extracellular vesicles, such as exosomes and microvesicles, is deemed crucial for tumorigenesis, invasion and spread of solid tumors. The ESCRT machinery (endosomal sorting complexes required for transport) and Rab-proteins act as key players in vesicular trafficking and secretion. Yet, their role in prostate cancer (PCa) is unknown. Therefore, this study aimed to elucidate the relevance of these components in PCa. In silico reanalysis of genes with known involvement in vesicular trafficking and secretion in an existing microarray dataset revealed low expression of RAB27A, RAB27B and VPS36 to be predictive for reduced BCR-free survival in patients with localized PCa (p=0.033, 0.025 and 0.005). In the same microarray dataset underexpression of RAB27A, RAB27B and VPS36 was seen in distant metastases (p<0.001; p=0.003; p<0.001). This was consistent in two further microarray datasets. qRT-PCR-validation in two independent cohorts of PCa specimens (n=90) showed low expression of VPS36 in PCa tissue (p=0.023), especially in castration-resistant tumors (p=0.002). In all five datasets there were significant correlations between the expression of at least two of the candidates. Upon knockdown of VPS36 an increase of RAB27A and RAB27B expression, but not vice versa, was observed in both prostate and breast cancer cells (PC3, MDA-MB‑231). In PC3 cell knockdown of RAB27B and VPS36 dramatically reduced colony formation (-52.2%, p<0.001; -71.1%, p<0.001) and, controversial to reports in other tumor entities, increased the release of extracellular particles (+25.3%, p=0.014; +45.6%, p<0.001). Taken together RAB27A, RAB27B and VPS36 are frequently underexpressed in advanced PCa and are inversely correlated with PCa outcome. There seems to be a close relationship in the expression of RAB27A, RAB27B and VPS36, with RAB27A and RAB27B being dependent on VPS36. Changes in colony formation and particle release upon RNAi indicate an involvement in paracrine cell-cell communication.

Extracellular vesicles carry microRNA-195 to intrahepatic cholangiocarcinoma and improve survival in a rat model

The cancer microenvironment plays a central role in cancer development, growth, and homeostasis. This paradigm suggests that cancer fibroblasts support cancers, probably in response to stimuli received from the cancer cells. We aimed at investigating whether extracellular vesicles (EVs) can shuttle microRNA (miR) species between cancer-associated fibroblasts (CAFs) and cancer cells. To this end, we extracted EVs according to published protocols. EVs were studied for their miR content by quantitative reverse-transcription polymerase chain reaction. EVs were transfected with select miR species and utilized in vitro as well as in vivo in a rat model of cholangiocarcinoma (CCA). We found that miR-195 is down-regulated in CCA cells, as well as in adjoining fibroblasts. Furthermore, we report that EVs shuttle miR-195 from fibroblasts to cancer cells. Last, we show that fibroblast-derived EVs, loaded with miR-195, can be administered in a rat model of CCA, concentrate within the tumor, decrease the size of cancers, and improve survival of treated rats.

CONCLUSION

EVs play a salient role in trafficking miR species between cancer cells and CAFs in human CCA. Understanding of these mechanisms may allow devising of novel therapeutics. (Hepatology 2017;65:501-514).

New insights into the function of Rab GTPases in the context of exosomal secretion

In the last two decades, extracellular vesicle-mediated communication between cells has become a major field in cell biology. However, the function of extracellular vesicles is far from clear, especially due to the disparity of released vesicles by cells. Basically, one must consider vesicles budding from the cell plasma membrane (ectosomes) and vesicles released upon fusion of an endosomal multivesicular compartment (exosomes). Moreover, even for exosomes, we report and discuss here the possibility that different routes regulated by specific Rab GTPases might produce exosomes having various biologic functions.

Going live with tumor exosomes and microvesicles

Tumor extracellular vesicles (EVs), including exosomes, emerged as key drivers of the pro-tumorigenic dialog between the tumor mass and its microenvironment by mediating long and short distance communication. In vitro studies defined the capacity of tumor EVs to modify the phenotypes of stromal and tumor cells. These studies are now supported by a growing number of functional in vivo experiments. Remarkably, they allowed the identification of a new role for tumor EVs in priming the pre-metastatic niches (PMN). Several molecules transported in tumor EVs (RNAs and proteins) have recently been found to be essential for tumor progression and metastasis in vivo. In parallel, novel EV labeling and tracking strategies have very recently allowed the first descriptions of tumor EVs in vivo and pave the way for a better understanding of their function in realistic pathophysiological contexts. Here, we review the functional approaches and the recent progress in in vivo imaging of EVs, which have refined our understanding of the role played by tumor EVs. Finally, we emphasize the remaining challenges and open questions related to the biology of tumor EVs.

The Multiple Roles of Exosomes in Metastasis

Exosomes are important contributors to cell-cell communication and their role as diagnostic markers for cancer and the pathogenesis for cancer is under intensive investigation. Here, we focus on their role in metastasis-related processes. We discuss their impact regarding promotion of invasion and migration of tumor cells, conditioning of lymph nodes, generation of premetastatic niches and organotropism of metastasis. Furthermore, we highlight interactions of exosomes with bone marrow and stromal components such as fibroblasts, endothelial cells, myeloid- and other immune-related cells in the context of metastases. For all processes as described above, we outline molecular and cellular components for therapeutic intervention with metastatic processes.

Functions of Cancer-Derived Extracellular Vesicles in Immunosuppression

Extracellular vesicles, including exosomes, constitute an important element of intercellular communication by carrying a variety of molecules from producer to target cells. The transport of mRNA and miRNA can directly modulate gene expression in the target cells. The miRNA content in exosomes is characteristic for the cell from which the vesicles were derived enabling the usage of exosomes as biomarkers for the diagnosis various diseases, including cancer. Cancer-derived exosomes support the survival and progression of tumors in many ways and also contribute to the neutralization of the anti-cancer immune response. Exosomes participate in all known mechanisms by which cancer evades the immune system. They influence the differentiation and activation of immune suppressor cells, they modulate antigen presentation, and are able to induce T-cell apoptosis. Although cancer-derived exosomes mainly suppress the immune system and facilitate tumor progression, they are also important sources of tumor antigens with potential clinical application in stimulating immune responses. This review summarizes how exosomes assist cancer to escape immune recognition and to acquire control over the immune system.

Extracellular vesicle communication pathways as regulatory targets of oncogenic transformation

Pathogenesis of human cancers bridges intracellular oncogenic driver events and their impact on intercellular communication. Among multiple mediators of this 'pathological connectivity' the role of extracellular vesicles (EVs) and their subsets (exosomes, ectosomes, oncosomes) is of particular interest for several reasons. The release of EVs from cancer cells represents a unique mechanism of regulated expulsion of bioactive molecules, a process that also mediates cell-to-cell transfer of lipids, proteins, and nucleic acids. Biological effects of these processes have been implicated in several aspects of cancer-related pathology, including tumour growth, invasion, angiogenesis, metastasis, immunity and thrombosis. Notably, the emerging evidence suggests that oncogenic mutations may impact several aspects of EV-mediated cell-cell communication including: (i) EV release rate and protein content; (ii) molecular composition of cancer EVs; (iii) the inclusion of oncogenic and mutant macromolecules in the EV cargo; (iv) EV-mediated release of genomic DNA; (v) deregulation of mechanisms responsible for EV biogenesis (vesiculome) and (vi) mechanisms of EV uptake by cancer cells. Intriguingly, EV-mediated intercellular transfer of mutant and oncogenic molecules between subpopulations of cancer cells, their indolent counterparts and stroma may exert profound biological effects that often resemble (but are not tantamount to) oncogenic transformation, including changes in cell growth, clonogenicity and angiogenic phenotype, or cause cell stress and death. However, several biological barriers likely curtail a permanent horizontal transformation of normal cells through EV-mediated mechanisms. The ongoing analysis and targeting of EV-mediated intercellular communication pathways can be viewed as a new therapeutic paradigm in cancer, while the analysis of oncogenic cargo contained in EVs released from cancer cells into biofluids is being developed for clinical use as a biomarker and companion diagnostics. Indeed, studies are underway to further explore the multiple links between molecular causality in cancer and various aspects of cellular vesiculation.

Extracellular Vesicles: Novel Mediators of Cell Communication In Metabolic Disease

Metabolic homeostasis emerges from the complex, multidirectional crosstalk between key metabolic tissues including adipose tissue, liver, and skeletal muscle. This crosstalk, traditionally mediated by hormones and metabolites, becomes dysregulated in human diseases such as obesity and diabetes. Extracellular vesicles (EVs; including exosomes) are circulating, cell-derived nanoparticles containing proteins and nucleic acids that interact with and modify local and distant cellular targets. Accumulating evidence, reviewed herein, supports a role for extracellular vesicles in obesity-associated metabolic disturbance, particularly the local and systemic inflammation characteristic of adipose and hepatic stress. As the practical and conceptual challenges facing the field are tackled, this emerging and versatile mode of intercellular communication may afford valuable insights and therapeutic opportunities in combatting these major threats to modern human health.

Breast cancer-derived extracellular vesicles stimulate myofibroblast differentiation and pro-angiogenic behavior of adipose stem cells

Adipose-derived stem cells (ASCs) are abundantly present in the mammary microenvironment and can promote breast cancer malignancy by differentiating into myofibroblasts. However, it remains largely unclear which role tumor-derived extracellular vesicles (TEVs) play in this process. Here, we used microfabricated, type I collagen-based 3-D tissue culture platforms to investigate the effect of breast cancer cell-derived TEVs on ASCs myofibroblast differentiation and consequential changes in extracellular matrix remodeling and vascular sprouting. TEVs collected from MDA MB-231 human metastatic breast cancer cells (MDAs) promoted ASC myofibroblast differentiation in both 2-D and 3-D cultures as indicated by increased alpha smooth muscle actin (α-SMA) and fibronectin (Fn) levels. Correspondingly, TEV-treated ASCs were more contractile, secreted more vascular endothelial growth factor (VEGF), and promoted angiogenic sprouting of human umbilical vein endothelial cells (HUVECs). These changes were dependent on transforming growth factor beta (TGF-β)-related signaling and tumor cell glutaminase activity as their inhibition decreased TEV-related myofibroblastic differentiation of ASCs and related functional consequences. In summary, our data suggest that TEVs are important signaling factors that contribute to ASC desmoplastic reprogramming in the tumor microenvironment, and suggest that tumor cell glutamine metabolism may be used as a therapeutic target to interfere with this process.

The Small GTPase Ral orchestrates MVB biogenesis and exosome secretion

Extracellular vesicles are novel mediators of cell-cell communication. They are present in all species and involved in physiological and pathological processes. One class of extracellular vesicles, the exosomes, originate from an endosomal compartment, the MultiVesicular Body (MVB), and are released from the cell upon fusion of the MVB with the plasma membrane. Although different molecular mechanisms have been associated with MVB biogenesis and exosome secretion, how they coordinate remains poorly documented. We recently found that the small GTPase Ral contributes to exosome release in nematodes and mammalian tumor cells. More specifically, we found that C. elegans RAL-1 is required for the biogenesis of MVBs, and later for MVB fusion with the plasma membrane. Here, we discuss our results in relationship with other factors involved in extracellular vesicle production such as the ESCRT complex and Phospholipase 1D. We propose models to explain Ral function in exosome secretion, its conservation in animals, and its possible role in tumor progression.

Tumor Cell-Derived Exosomes from the Prostate Cancer Cell Line TRAMP-C1 Impair Osteoclast Formation and Differentiation

Skeletal metastatic disease is a deleterious consequence of dissemination of tumor cells from numerous primary sites, such as prostate, lung and breast. Skeletal metastases are still incurable, resulting in development of clinical complications and decreased survival for cancer patients with metastatic disease. During the last decade, tumor cell-derived microvesicles have been identified and suggested to be involved in cancer disease progression. Whether cancer exosomes are involved in tumor and bone cell interactions in the metastatic site is still, however, a rather unexplored field. Here we show that exosomes isolated from the murine prostate cancer cell line TRAMP-C1 dramatically decrease fusion and differentiation of monocytic osteoclast precursors to mature, multinucleated osteoclasts. The presence of tumor cell-derived exosomes also clearly decreased the expression of established markers for osteoclast fusion and differentiation, including DC-STAMP, TRAP, cathepsin K, and MMP-9. In contrast, exosomes derived from murine fibroblastic cells did not affect osteoclast formation. Our findings suggest that exosomes released from tumor cells in the tumor-bone interface are involved in pathological regulation of bone cell formation in the metastatic site. This further strengthens the role of tumor cell-derived microvesicles in cancer progression and disease aggressiveness.

Secreted primary human malignant mesothelioma exosome signature reflects oncogenic cargo

Malignant mesothelioma (MM) is a highly-aggressive heterogeneous malignancy, typically diagnosed at advanced stage. An important area of mesothelioma biology and progression is understanding intercellular communication and the contribution of the secretome. Exosomes are secreted extracellular vesicles shown to shuttle cellular cargo and direct intercellular communication in the tumour microenvironment, facilitate immunoregulation and metastasis. In this study, quantitative proteomics was used to investigate MM-derived exosomes from distinct human models and identify select cargo protein networks associated with angiogenesis, metastasis, and immunoregulation. Utilising bioinformatics pathway/network analyses, and correlation with previous studies on tumour exosomes, we defined a select mesothelioma exosomal signature (mEXOS, 570 proteins) enriched in tumour antigens and various cancer-specific signalling (HPGD/ENO1/OSMR) and secreted modulators (FN1/ITLN1/MAMDC2/PDGFD/GBP1). Notably, such circulating cargo offers unique insights into mesothelioma progression and tumour microenvironment reprogramming. Functionally, we demonstrate that oncogenic exosomes facilitate the migratory capacity of fibroblast/endothelial cells, supporting the systematic model of MM progression associated with vascular remodelling and angiogenesis. We provide biophysical and proteomic characterisation of exosomes, define a unique oncogenic signature (mEXOS), and demonstrate the regulatory capacity of exosomes in cell migration/tube formation assays. These findings contribute to understanding tumour-stromal crosstalk in the context of MM, and potential new diagnostic and therapeutic extracellular targets.

How cancer cells dictate their microenvironment: present roles of extracellular vesicles

Intercellular communication plays an important role in cancer initiation and progression through secretory molecules, including growth factors and cytokines. Recent advances have revealed that small membrane vesicles, termed extracellular vesicles (EVs), served as a regulatory agent in the intercellular communication of cancer. EVs enable the transfer of functional molecules, including proteins, mRNA and microRNAs (miRNAs), into recipient cells. Cancer cells utilize EVs to dictate the unique phenotype of surrounding cells, thereby promoting cancer progression. Against such "education" by cancer cells, non-tumoral cells suppress cancer initiation and progression via EVs. Therefore, researchers consider EVs to be important cues to clarify the molecular mechanisms of cancer biology. Understanding the functions of EVs in cancer progression is an important aspect of cancer biology that has not been previously elucidated. In this review, we summarize experimental data that indicate the pivotal roles of EVs in cancer progression.

Single punch, double biopsy

OBJECTIVE

In lethal primary metastatic prostate cancer, biopsy material is often the only accessible cancer tissue. Lack of tissue quantity limited the use of biopsy cores for analyzing higher numbers of molecular markers and standard histopathologic evaluation for clinical diagnosis simultaneously. Recent advances in single cell analytics have paved the way to characterize a tumor in more depth from minute input material such as biopsies. We therefore aimed to develop a biopsy needle, which generates two cores side by side from the same punch: one for standard histopathologic analysis to allow for routine diagnostics and the second one for single cell analytics.

METHODS

On the basis of a conventional punch biopsy needle we have milled two parallel longitudinal rifts into the needles shat which are separated by a 100 µm thick metal sheet. Each rift can harbor a single tissue core.

RESULTS

Two cores from the same punch were generated reproducibly from a radical prostatectomy specimen and showed congruent results in histopathologic analysis. Both cores yielded equally sufficient material for standard H&E staining and histopathological evaluation.

CONCLUSION

Our modified biopsy system will allow for simultaneous acquisition of tissue cores for diagnostic and scientific analysis from solid tumors or metastatic sites.

Extracellular Vesicles from Metastatic Rat Prostate Tumors Prime the Normal Prostate Tissue to Facilitate Tumor Growth

Accumulating data indicates that tumor-derived extracellular vesicles (EVs) are responsible for tumor-promoting effects. However, if tumor EVs also prepare the tumor-bearing organ for subsequent tumor growth, and if this effect is different in low and high malignant tumors is not thoroughly explored. Here we used orthotopic rat Dunning R-3327 prostate tumors to compare the role of EVs from fast growing and metastatic MatLyLu (MLL) tumors with EVs from more indolent and non-metastatic Dunning G (G) tumors. Prostate tissue pre-conditioned with MLL-EVs in vivo facilitated G tumor establishment compared to G-EVs. MLL-EVs increased prostate epithelial proliferation and macrophage infiltration into the prostate compared to G-EVs. Both types of EVs increased macrophage endocytosis and the mRNA expression of genes associated with M2 polarization in vitro, with MLL-EVs giving the most pronounced effects. MLL-EVs also altered the mRNA expression of growth factors and cytokines in primary rat prostate fibroblasts compared to G-EVs, suggesting fibroblast activation. Our findings propose that EVs from metastatic tumors have the ability to prime the prostate tissue and enhance tumor growth to a higher extent than EVs from non-metastatic tumors. Identifying these differences could lead to novel therapeutic targets and potential prognostic markers for prostate cancer.

Exosome cargo reflects TGF-β1-mediated epithelial-to-mesenchymal transition (EMT) status in A549 human lung adenocarcinoma cells

It has been suggested that tumor cells secrete exosomes to modify the local microenvironment, which then promotes intercellular communication and metastasis. Although exosomes derived from cancer cells may contribute to the epithelial-mesenchymal transition (EMT) in untransformed cells, few studies have defined exosome cargo upon induction of EMT. In this study, we investigated the changes in exosomal cargo from the epithelial to mesenchymal cell phenotype by inducing EMT with transforming growth factor (TGF)-β1 in A549 human lung adenocarcinoma cells. The protein content of the exosomes reflects the change in the cell phenotype. In addition, miR-23a was significantly enriched in the exosomes after mesenchymal transition. Following treatment of exosomes from mesenchymal cells via EMT induction with TGF-β1 to the epithelial cell type, phenotypic changes in protein expression level and cell morphology were observed. Autologous treatment of exosomes enhanced the transcriptional activity and abundance of β-catenin. Our results suggest that the exosomal protein and miRNA content reflects the physiological condition of its source and that exosomes induce phenotypic changes via autocrine signaling.

Fibroblast activation in cancer: when seed fertilizes soil

In solid cancers, activated fibroblasts acquire the capacity to provide fertile soil for tumor progression. Specifically, cancer-associated fibroblasts (CAFs) establish a strong relationship with cancer cells. This provides advantages to both cell types: whereas cancer cells initiate and sustain CAF activation, CAFs support cancer cell growth, motility and invasion. This results in tumor progression, metastasis and chemoresistance. Numerous studies have detailed the mechanisms involved in fibroblast activation and cancer progression, some of which are reviewed in this article. Cancer cells and CAFs are "partners in crime", and their interaction is supported by inflammation. An understanding of the enemy, the cancer cell population and its "allies" should provide novel opportunities for targeted-drug development. Graphical Abstract Molecular mechanism of fibroblast activation. a Normal fibroblasts are the most common cell type in the extracellular matrix and are responsible for the synthesis of collagens and fibrilar proteins. Under normal conditions, fibroblasts maintain tissue homeostasis and contribute to proper cell communication and function. Fibroblasts can be activated by a diverse set of factors secreted from cancer or immune cells. Not only growth factors such as TGF-β, PDGF, HGF and FGF but also interleukins, metalloproteinases and reactive oxygen species can promote activation. Likewise, transcriptional factors such as NF-κB and HSF-1 play an important role, as do the gene family of metalloproteinase inhibitors, Timp and the NF-κB subunit, p62. Interestingly, fibroblasts themselves can stimulate cancer cells to support activation further. b Once activated, fibroblasts undergo a phenotype switch and become cancer-associated fibroblasts (CAFs) expressing various markers such as α-SMA, FSP1, vimentin and periostatin. c Recently, the LIF/GP130/IL6-R pathway has been identified as a signaling cascade involved in fibroblast activation. Upon LIF stimulation, JAK is phosphorylated and further activates STAT3, a transcriptional factor that is then translocated into the nucleus where it promotes the transcription of genes responsible for cell growth, differentiation, proliferation and apoptosis. Ruxolitinib can inhibit JAK and prevent STAT3 activation. Further on, the maintenance of JAK activation is supported by epigenetical changes and post-translational modifications. Once pSTAT3 is acetylated by histon acetyltransferase, p300, it leads to the loss of expression of SHP-1, which is a negative regulator of the JAK/STAT pathway. Silencing of SHP-1 steers the constitutive activation of JAK and STAT3.

Exosomes in carcinogenesis: molecular palkis carry signals for the regulation of cancer progression and metastasis

Exosomes, which act as biological cargo vessels, are cell-released, phospholipid-enclosed vesicles. In eukaryotic cells, exosomes carry and exchange biological materials or signals for the benefit or detriment to the cells. Thereby, we consider exosomes to be molecular Palkis (carriers). Although exosomes are currently one of the most popularly researched cellular entities, they have remained largely enigmatic and warrant continued investigation into their structure and functions. These membraned vesicles are between 30 and 150 nm in diameter and are actively secreted by all cell types. While initially considered cellular "trash bags," recent years have revealed exosomes to be dynamic and multi-functional vesicles that may play a crucial role in cancer development, progression and metastasis. Thereby, they have the potential to be used in development of therapeutic modalities for cancer and other diseases. As more research studies emerge, it's becoming evident that exosomes are released by cells with a purpose and are representatives of certain cell types and disease conditions. Hence, they may also be used as biomarkers for the detection of cancer initiation, progression and organotropic metastatic growth of cancer cells. This review will focus on the recent developments achieved in identifying the role of exosomes in cancer development and progression as well as therapeutic implications. The review will also discuss the pitfalls of methodologies used for the extraction of exosomes.

Exosomes from the tumor microenvironment as reciprocal regulators that enhance prostate cancer progression

Distant organ metastasis of prostate cancer is a puzzle, and various theories have successively arisen to explain the mechanism of lethal cancer progression. While perhaps agreeable to many cancer biologists, the very statement of "seed and soil" proposed by Stephan Paget in 1881 is arguably still the major statement for organ-specific cancer metastasis. Since recent studies showed important correlations of regulation of cancer cells and the microenvironment, exosomes from cancer and stromal cells seem to create another important niche for metastasis. Stromal cells pretreated with exosomes from metastatic cancer cells increase the potential of change stromal cells. The poorly metastatic cancer cells could also enhance malignancy through transfer of proteins, microribonucleic acid and messenger ribonucleic acid to recipient cancer cells. Herein, we reviewed extracellular exosomes as a factor involved in cross-talk between stromal and prostate cancer epithelial cells.

Tissue Inhibitor of Metalloproteinase-1 Is Confined to Tumor-Associated Myofibroblasts and Is Increased With Progression in Gastric Adenocarcinoma

The tissue inhibitor of metalloproteinase-1 (TIMP-1) inhibits the extracellular matrix-degrading activity of several matrix metalloproteinases, thereby regulating cancer cell invasion and metastasis. Studies describing the expression pattern and cellular localization of TIMP-1 in gastric cancer are, however, highly discordant. We addressed these inconsistencies by performing immunohistochemistry and in situ hybridization analyses in a set of 49 gastric cancer lesions to reexamine the TIMP-1 localization. In addition, we correlated these findings to clinicopathological parameters. We show that strong expression of TIMP-1 protein and mRNA was observed in a subpopulation of stromal fibroblast-like cells at the periphery of the cancer lesions. In a few cases, a small fraction of cancer cells showed weak expression of TIMP-1 protein and mRNA. The stromal TIMP-1-expressing cells were mainly tumor-associated myofibroblasts. In the normal-appearing mucosa, scattered TIMP-1 protein was only found in chromogranin A positive cells. TIMP-1-positive myofibroblasts at the invasive front of the tumors were more frequently seen in intestinal than in diffuse histological subtype cases (p=0.009). A significant trend to a higher number of cases showing TIMP-1 staining in myofibroblasts with increasing tumor, node, metastasis (TNM) stage was also revealed (p=0.041). In conclusion, tumor-associated myofibroblasts are the main source of increased TIMP-1 expression in gastric cancer.

Stromal dynamic reciprocity in cancer: intricacies of fibroblastic-ECM interactions

Stromal dynamic reciprocity (SDR) consists of the biophysical and biochemical interplay between connective tissue elements that regulate and maintain organ homeostasis. In epithelial cancers, chronic alterations of SDR result in the once tumor-restrictive stroma evolving into a 'new' tumor-permissive environment. This altered stroma, known as desmoplasia, is initiated and maintained by cancer associated fibroblasts (CAFs) that remodel the extracellular matrix (ECM). Desmoplasia fuels a vicious cycle of stromal dissemination enriching both CAFs and desmoplastic ECM. Targeting specific drivers of desmoplasia, such as CAFs, either enhances or halts tumor growth and progression. These conflicting effects suggest that stromal interactions are not fully understood. This review highlights known fibroblastic-ECM interactions in an effort to encourage therapies that will restore cancer-restrictive stromal cues.

Exosome: A Novel Approach to Stimulate Bone Regeneration through Regulation of Osteogenesis and Angiogenesis

The clinical need for effective bone regeneration therapy remains in huge demands. However, the current "gold standard" treatments of autologous and allogeneic bone grafts may result in various complications. Furthermore, safety considerations of biomaterials and cell-based treatment require further clarification. Therefore, developing new therapies with stronger osteogenic potential and a lower incidence of complications is worthwhile. Recently, exosomes, small vesicles of endocytic origin, have attracted attention in bone regeneration field. The vesicles travel between cells and deliver functional cargoes, such as proteins and RNAs, thereby regulating targeted cells differentiation, commitment, function, and proliferation. Much evidence has demonstrated the important roles of exosomes in osteogenesis both in vitro and in vivo. In this review, we summarize the properties, origins and biogenesis of exosomes, and the recent reports using exosomes to regulate osteogenesis and promote bone regeneration.

Exosome-Mediated Metastasis: From Epithelial-Mesenchymal Transition to Escape from Immunosurveillance

Exosomes are extracellular signalosomes that facilitate eukaryotic intercellular communication under a wide range of normal physiological contexts. In malignancies, this regulatory circuit is co-opted to promote cancer cell survival and outgrowth. Tumour-derived exosomes (TDEs) carry a pro-EMT (epithelial-mesenchymal transition) programme including transforming growth factor beta (TGFβ), caveolin-1, hypoxia-inducible factor 1 alpha (HIF1α), and β-catenin that enhances the invasive and migratory capabilities of recipient cells, and contributes to stromal remodelling and premetastatic niche formation. The integrin expression patterns on TDEs appear to dictate their preferential uptake by organ-specific cells, implying a crucial role of this pathway in organotropic metastasis. Through the expression of immunomodulatory molecules such as CD39 and CD73, TDEs modify the immune contexture of the tumour microenvironment, which could have implications for immunotherapy. Hence, targeting TDE dysregulation pathways, such as the heparanase/syndecan-1 axis, could represent novel therapeutic strategies in the quest to conquer cancer.

Tumour cell-derived exosomes endow mesenchymal stromal cells with tumour-promotion capabilities

Mesenchymal stromal cells (MSCs) are a major component of the tumour microenvironment. A plethora of elegant studies focusing on tumour-derived MSCs have shown that they, unlike normal MSCs in other tissue, exhibit a strong ability to promote tumour progression. However, the mechanisms underlying the conversion of normal MSCs into tumour-associated MSCs are unknown. We report here a critical role of tumour cell-derived exosomes in endowing bone marrow-derived MSCs (BM-MSCs) with a tumour-favourable phenotype. Tumour cell-derived exosomes affected neither the growth factor production nor the immunosuppressive property of MSCs; rather, they endowed MSCs with a strong ability to promote macrophage infiltration into B16-F0 melanoma or EL-4 lymphoma. Ablation of macrophages by clodronate liposome administration reversed the tumour-promoting effect of MSCs educated by tumour cell-derived exosomes (TE-MSCs) on the tumour growth. By comparing the chemokine profile of BM-MSCs with that of TE-MSCs, we found that TE-MSCs produced a large amount of CCR2 ligands, CCL2 and CCL7, which are responsible for macrophage recruitment. CCR2-specific inhibitor was found to block the tumour-promoting effect of TE-MSCs. Thus, our investigations demonstrated that tumour cell-derived exosomes confer BM-MSCs the ability to enhance tumour growth. Therefore, we uncovered a novel mechanism underlying the conversion of normal MSCs to tumour-associated MSCs.

Tumor-Derived Exosomes and Their Role in Cancer Progression

Tumor cells actively produce, release, and utilize exosomes to promote tumor growth. Mechanisms through which tumor-derived exosomes subserve the tumor are under intense investigation. These exosomes are information carriers, conveying molecular and genetic messages from tumor cells to normal or other abnormal cells residing at close or distant sites. Tumor-derived exosomes are found in all body fluids. Upon contact with target cells, they alter phenotypic and functional attributes of recipients, reprogramming them into active contributors to angiogenesis, thrombosis, metastasis, and immunosuppression. Exosomes produced by tumors carry cargos that in part mimic contents of parent cells and are of potential interest as noninvasive biomarkers of cancer. Their role in inhibiting the host antitumor responses and in mediating drug resistance is important for cancer therapy. Tumor-derived exosomes may interfere with cancer immunotherapy, but they also could serve as adjuvants and antigenic components of antitumor vaccines. Their biological roles in cancer development or progression as well as cancer therapy suggest that tumor-derived exosomes are critical components of oncogenic transformation.

The biology and function of exosomes in cancer

Humans circulate quadrillions of exosomes at all times. Exosomes are a class of extracellular vesicles released by all cells, with a size range of 40-150 nm and a lipid bilayer membrane. Exosomes contain DNA, RNA, and proteins. Exosomes likely remove excess and/or unnecessary constituents from the cells, functioning like garbage bags, although their precise physiological role remains unknown. Additionally, exosomes may mediate specific cell-to-cell communication and activate signaling pathways in cells they fuse or interact with. Exosomes are detected in the tumor microenvironment, and emerging evidence suggests that they play a role in facilitating tumorigenesis by regulating angiogenesis, immunity, and metastasis. Circulating exosomes can be used as liquid biopsies and noninvasive biomarkers for early detection, diagnosis, and treatment of cancer patients.

Exosome Secretion - More Than Simple Waste Disposal? Implications for Physiology, Diagnostics and Therapeutics

Less than 100 nm in size and spherical in form - exosomes – vesicles expelled and taken up by cells, have ignited a new-found fascination. One which is derived from the sheer variety of exosomal content, ranging from microRNAs to transcription factors, capable of affecting a multitude of processes and pathways simultaneously within a target cell. Initially dismissed in 1983 as a waste disposal mechanism, today they form an entire field of research, being documented thus far in invertebrates, mammals, pathogens and potentially some plants. Many studies have suggested these spherical enigmas may possess a function, being implicated in processes ranging from animal behaviour to viral infection. This review will evaluate the evidence for the role of exosomes in physiology and pathophysiology, as well as their potential for application in the diagnosis and treatment of disease.

Extracellular vesicle transfer of cancer pathogenic components

Extracellular vesicles (EV), known as exosomes and microvesicles, serve as versatile intercellular communication vehicles. Increasing evidence has shown that cancer cell-derived EV carry pathogenic components, such as proteins, messenger RNA (mRNA), microRNA (miRNA), DNA, lipids and transcriptional factors, that can mediate paracrine signaling in the tumor microenvironment. These data suggest that EV transfer of cancer pathogenic components enable long-distance crosstalk between cancer cells and distant organs, resulting in the promotion of the initial steps for pre-metastatic niche formation. Understanding the metastatic mechanisms through EV transfer may open up a new avenue for cancer therapeutic strategies. Furthermore, the circulating EV have also been of interest as a source for liquid biopsies. EV in body fluids provide a reliable source of miRNA and proteins for cancer biomarkers. The tumor-specific components in EV effectively provide various messages on the physiological and pathological status of cancer patients. Although many researchers are searching for EV biomarkers using miRNA microarrays and proteome analyses, the detection technology for circulating EV in body fluids has not yet reached the point of clinical application. In this review, we summarize recent findings regarding EV function, specifically in metastasis through the transfer of cancer pathogenic components. Furthermore, we highlight the potential of using circulating EV for cancer diagnosis.

The emerging roles of exosomes in tumor-stroma interaction

PURPOSE

The tumor-stroma interaction is critical for the development and progression of cancer. Cancer-associated fibroblasts (CAFs), one of the major components of the tumor stroma, can promote tumor growth and metastasis. Exosomes are secreted microvesicles that mediate cell-to-cell communication. Exosomal contents, including proteins, nucleic acids, and lipids, can be shuttled from donor cells to target cells. Recent studies suggest that exosomes play important roles in the tumor-stroma interaction. Herein, we review the multifaceted roles of exosomes in the tumor-stroma interaction and the underlying molecular mechanisms.

METHODS

Literature search for all relevant publications was performed on PubMed databases. The keywords of exosomes, tumor, stroma, CAFs, mesenchymal stem cells (MSCs) and other closely related terms were used for searching.

RESULTS

Tumor cell-derived exosomes induce the differentiation of fibroblasts and MSCs into CAFs. In turn, exosomes secreted by CAFs promote tumor growth, metastasis, and drug resistance through distinct mechanisms. Moreover, exosomes from stromal cells can be used as therapeutic vehicles for the delivery of anticancer drugs.

CONCLUSIONS

Tumor cells communicate with CAFs through exosomes, which establishes a bidirectional cross talk to promote tumor growth, metastasis, and drug resistance. Targeting exosomes in tumor-stroma interaction may have important implications for anticancer therapy.

Energy-requiring uptake of prostasomes and PC3 cell-derived exosomes into non-malignant and malignant cells

Epithelial cells lining the prostate acini release, in a regulated manner (exocytosis), nanosized vesicles called prostasomes that belong to the exosome family. Prostate cancer cells have preserved this ability to generate and export exosomes to the extracellular space. We previously demonstrated that human prostasomes have an ATP-forming capacity. In this study, we compared the capacity of extracellular vesicles (EVs) to generate ATP between normal seminal prostasomes and exosomes secreted by PC3 cells (PC3 exosomes), a prostate cancer cell line. Proteomic analyses identified enzymes of the glycolytic chain in both prostasomes and PC3 exosomes, and we found that both of them were capable of generating ATP when supplied with substrates. Notably, the net production of extracellular ATP was low for prostasomes due to a high ATPase activity contrary to an elevated net ATP level for PC3 exosomes because of their low ATPase activity. The uptake of the 2 types of EVs by normal prostate epithelial cells (CRL2221) and prostate cancer cells (PC3) was visualized and measured, demonstrating differential kinetics. Interestingly, this uptake was dependent upon an ongoing glycolytic flux involving extracellular ATP formation by EVs and/or intracellular ATP produced from the recipient cells. We conclude that the internalization of EVs into recipient cells is an energy-requiring process also demanding an active V-ATPase and the capacity of EVs to generate extracellular ATP may play a role in this process.

Large oncosomes contain distinct protein cargo and represent a separate functional class of tumor-derived extracellular vesicles

Large oncosomes (LO) are atypically large (1-10μm diameter) cancer-derived extracellular vesicles (EVs), originating from the shedding of membrane blebs and associated with advanced disease. We report that 25% of the proteins, identified by a quantitative proteomics analysis, are differentially represented in large and nano-sized EVs from prostate cancer cells. Proteins enriched in large EVs included enzymes involved in glucose, glutamine and amino acid metabolism, all metabolic processes relevant to cancer. Glutamine metabolism was altered in cancer cells exposed to large EVs, an effect that was not observed upon treatment with exosomes. Large EVs exhibited discrete buoyant densities in iodixanol (OptiPrep^TM) gradients. Fluorescent microscopy of large EVs revealed an appearance consistent with LO morphology, indicating that these structures can be categorized as LO. Among the proteins enriched in LO, cytokeratin 18 (CK18) was one of the most abundant (within the top 5^th percentile) and was used to develop an assay to detect LO in the circulation and tissues of mice and patients with prostate cancer. These observations indicate that LO represent a discrete EV type that may play a distinct role in tumor progression and that may be a source of cancer-specific markers.

Extracellular Vesicles and Their Role in Urologic Malignancies

CONTEXT

Research has increased significantly on small vesicles secreted by healthy and diseased cells. Recent discoveries have revealed their functional and biomarker roles in urologic diseases. Whether and how this knowledge of extracellular vesicles (EVs) affects translational research and clinical practices have become pertinent questions.

OBJECTIVE

To provide an overview of the currently available literature on the rising field of EVs, focusing on function and pathogenesis in urologic cancers and the usefulness of EVs as biomarkers.

EVIDENCE ACQUISITION

A systematic literature search was conducted using PubMed to identify original articles, review articles, and editorials regarding EVs in different types of urologic tumor diseases. Articles published between 2005 and 2015 were reviewed and selected with the consensus of all authors.

EVIDENCE SYNTHESIS

Besides soluble factors, different types of EVs are involved in the complex cross talk between different cell types. EVs regulate normal physiologic processes like spermatogenesis and renal function, as well as disease-specific processes including bladder, kidney, and prostate cancer. The content of EVs is derived from the cytoplasm of the donor cell. The proteins and RNAs within these EVs can be isolated from body fluids (eg, urine and blood) and represent potential diagnostic and prognostic biomarkers. EVs are also candidate therapeutic targets and potentially useful as therapeutic vehicles.

CONCLUSIONS

The current data suggest that EVs are important regulators of cell-cell communication. The growing knowledge about their roles in urologic malignancies provides the basis for novel therapeutic strategies. In addition, nucleic acid and the protein content of EVs holds promise for the discovery of urine- or serum-based biomarkers for kidney, bladder, and prostate cancer.

PATIENT SUMMARY

Normal and cancer cells secrete small vesicles that contain proteins and RNAs from the cell of origin. Changes in the diseased cells can be detected by examining the altered content of these vesicles when secreted in body fluids, for example, blood and urine. The recently discovered roles of extracellular vesicles (EVs) provide new options to detect malignancy in the urine and blood. The uptake of EVs may be blocked therapeutically and thereby potentially impede cancer progression.

Focus on Extracellular Vesicles: New Frontiers of Cell-to-Cell Communication in Cancer

Extracellular Vesicles (EVs) have received considerable attention in recent years, both as mediators of intercellular communication pathways that lead to tumor progression, and as potential sources for discovery of novel cancer biomarkers. For many years, research on EVs has mainly investigated either the mechanism of biogenesis and cargo selection and incorporation, or the methods of EV isolation from available body fluids for biomarker discovery. Recent studies have highlighted the existence of different populations of cancer-derived EVs, with distinct molecular cargo, thus pointing to the possibility that the various EV populations might play diverse roles in cancer and that this does not happen randomly. However, data attributing cancer specific intercellular functions to given populations of EVs are still limited. A deeper functional, biochemical and molecular characterization of the various EV classes might identify more selective clinical markers, and significantly advance our knowledge of the pathogenesis and disease progression of many cancer types.

Whom to blame for metastasis, the epithelial-mesenchymal transition or the tumor microenvironment?

Changes in the tumor microenvironment (TME) can trigger the activation of otherwise non-malignant cells to become highly aggressive and motile. This is evident during initial tumor growth when the poor vascularization in tumors generates hypoxic regions that trigger the latent embryonic program, epithelial-to-mesenchymal transition (EMT), in epithelial carcinoma cells (e-cars) leading to highly motile mesenchymal-like carcinoma cells (m-cars), which also acquire cancer stem cell properties. After that, specific bidirectional interactions take place between m-cars and the cellular components of TME at different stages of metastasis. These interactions include several vicious positive feedback loops in which m-cars trigger a phenotypic switch, causing normal stromal cells to become pro-tumorigenic, which then further promote the survival, motility, and proliferation of m-cars. Accordingly, there is not a single culprit accounting for metastasis. Instead both m-cars and the TME dynamically interact, evolve and promote metastasis. In this review, we discuss the current status of the known interactions between m-cars and the TME during different stages of metastasis and how these interactions promote the metastatic activity of highly malignant m-cars by promoting their invasive mesenchymal phenotype and CSC properties.