Exosome-Mediated Signaling in Epithelial to Mesenchymal Transition and Tumor Progression

Extracellular vesicles regulate metastable phenotypes of lymphangioleiomyomatosis cells via shuttling ATP synthesis to pseudopodia and activation of integrin adhesion complexes

Pulmonary lymphangioleiomyomatosis (LAM) is metastatic sarcoma but mechanisms regulating LAM metastasis are unknown. Extracellular vesicle (EV) regulate cancer metastasis but their roles in LAM have not yet been investigated. Here, we report that EV biogenesis is increased in LAM and LAM EV cargo is enriched with lung tropic integrins, metalloproteinases, and cancer stem cell markers. LAM-EV increase LAM cell migration and invasion via the ITGα6/β1-c-Src-FAK-AKT axis. Metastable (hybrid) phenotypes of LAM metastasizing cells, pivotal for metastasis, are regulated by EV from primary tumor or metastasizing LAM cells via shuttling ATP synthesis to cell pseudopodia or activation of integrin adhesion complex, respectively. In mouse models of LAM, LAM-EV increase lung metastatic burden through mechanisms involving lung extracellular matrix remodeling. Collectively, these data provide evidence for the role of EV in promoting LAM lung metastasis and identify novel EV-dependent mechanisms regulating metastable phenotypes of tumor cells. Clinical impact of research is that it establishes LAM pathway as novel target for LAM therapy.

Role of Extracellular Vesicles in the Progression of Brain Tumors

Brain tumors, and, in particular, glioblastoma (GBM), are among the most aggressive forms of cancer. In spite of the advancement in the available therapies, both diagnosis and treatments are still unable to ensure pathology-free survival of the GBM patients for more than 12-15 months. At the basis of the still poor ability to cope with brain tumors, we can consider: (i) intra-tumor heterogeneity; (ii) heterogeneity of the tumor properties when we compare different patients; (iii) the blood-brain barrier (BBB), which makes difficult both isolation of tumor-specific biomarkers and delivering of therapeutic drugs to the brain. Recently, it is becoming increasingly clear that cancer cells release large amounts of extracellular vesicles (EVs) that transport metabolites, proteins, different classes of RNAs, DNA, and lipids. These structures are involved in the pathological process and characterize any particular form of cancer. Moreover, EVs are able to cross the BBB in both directions. Starting from these observations, researchers are now evaluating the possibility to use EVs purified from organic fluids (first of all, blood and saliva), in order to obtain, through non-invasive methods (liquid biopsy), tumor biomarkers, and, perhaps, also for obtaining nanocarriers for the targeted delivering of drugs.

Exosomes in asthma: Underappreciated contributors to the pathogenesis and novel therapeutic tools

OBJECTIVE

Asthma, a chronic inflammatory disease with diverse pathomechanisms, presents challenges in developing personalized diagnostic and therapeutic approaches. This review aims to provide a comprehensive overview of the role of exosomes, small extracellular vesicles, in asthma pathophysiology and explores their potential as diagnostic biomarkers and therapeutic tools.

METHODS

A literature search was conducted to identify recent studies investigating the involvement of exosomes in asthma. The retrieved articles were analyzed to extract relevant information on the role of exosomes in maintaining lung microenvironment homeostasis, regulating inflammatory responses, and their diagnostic and therapeutic potential for asthma.

RESULTS

Exosomes secreted by various cell types, have emerged as crucial mediators of intercellular communication in healthy and diseased conditions. Evidence suggest that exosomes play a significant role in maintaining lung microenvironment homeostasis and contribute to asthma pathogenesis by regulating inflammatory responses. Differential exosomal content between healthy individuals and asthmatics holds promise for the development of novel asthma biomarkers. Furthermore, exosomes secreted by immune and nonimmune cells, as well as those detected in biofluids, demonstrate potential in promoting or regulating immune responses, making them attractive candidates for designing new treatment strategies for inflammatory conditions such as asthma.

CONCLUSION

Exosomes, with their ability to modulate immune responses and deliver therapeutic cargo, offer potential as targeted therapeutic tools in asthma management. Further research and clinical trials are required to fully understand the mechanisms underlying exosome-mediated effects and translate these findings into effective diagnostic and therapeutic strategies for asthma patients.

Exosomes derived from programmed cell death: mechanism and biological significance

Exosomes are nanoscale extracellular vesicles present in bodily fluids that mediate intercellular communication by transferring bioactive molecules, thereby regulating a range of physiological and pathological processes. Exosomes can be secreted from nearly all cell types, and the biological function of exosomes is heterogeneous and depends on the donor cell type and state. Recent research has revealed that the levels of exosomes released from the endosomal system increase in cells undergoing programmed cell death. These exosomes play crucial roles in diseases, such as inflammation, tumors, and autoimmune diseases. However, there is currently a lack of systematic research on the differences in the biogenesis, secretion mechanisms, and composition of exosomes under different programmed cell death modalities. This review underscores the potential of exosomes as vital mediators of programmed cell death processes, highlighting the interconnection between exosome biosynthesis and the regulatory mechanisms governing cell death processes. Furthermore, we accentuate the prospect of leveraging exosomes for the development of innovative biomarkers and therapeutic strategies across various diseases.

Recent Progress in the Application of Exosome Analysis in Ovarian Cancer Management

Exosomes are very small (nano-sized) vesicles participating in tumor development by involvement in intercellular communication mediated by transferring biocomponents. Exosomes appear to play vital roles in various cancer development, such as ovarian cancer, a common malignancy in women. Several hallmarks of ovarian cancer are reported to be affected by the exosomemediated cellular cross-talk, including modulating peritoneal dissemination and chemoresistance. Since the expression of some biomolecules, such as miRNAs and mRNA, is changed in ovarian cancer, these exo-biomolecules can be applied as prognostic, diagnostic, and therapeutic biomarkers. Also, the selective loading of specific chemotherapeutic agents into exosomes highlights these biocarries as potential delivery devices. Exosomes could be artificially provided and engineered to better target the site of interest in ovarian cancer. In the present review, we summarize the notable achievement of exosome application in ovarian cancer management to gain applicable transitional insight against this cancer.

Down-regulation of COL1A1 inhibits tumor-associated fibroblast activation and mediates matrix remodeling in the tumor microenvironment of breast cancer

We investigated the effects of collagen type I alpha 1 (COL1A1) on tumor-associated fibroblast activation and matrix remodeling in the tumor microenvironment of breast cancer. Cells were divided into the blank control, negative control, and siRNA-COL1A1 groups, or HKF control, HKF + exosomes (EXO), HKF + siRNA negative control-EXO, and HKF + siRNA-COL1A1-EXO co-culture groups. Western blot and quantitative real-time PCR detected gene expressions. COL Ⅰ, COL Ⅲ, and TGF-β1 were detected by enzyme-linked immunosorbent assay. We found that compared with blank and negative control groups, COL1A1 expression and the secretion of exosomes by breast cancer cells were inhibited in the siRNA-COL1A1 group. Compared with the HKF control group, the COL Ⅰ, COL Ⅲ, TGF-β1, α-SMA, and fibroblast activation protein (FAP) were increased, while the E-cadherin and CAV-1 were decreased in the HKF + EXO, HKF + siRNA negative control-EXO, and HKF + siRNA-COL1A1-EXO co-culture groups. Compared with HKF + EXO and HKF + siRNA negative control-EXO co-culture groups, the COL Ⅰ, COL Ⅲ, TGF-β1, α-SMA, and FAP were decreased, and the E-cadherin and CAV-1 were increased in the HKF + siRNA-COL1A1-EXO co-culture group. Collectively, COL1A1 down-regulation may inhibit exosome secretion possibly via inhibiting COL Ⅰ and upregulating CAV-1, thereby inhibiting tumor-associated fibroblast activation and matrix remodeling in the tumor microenvironment.

Engineering a tunable micropattern-array assay to sort single extracellular vesicles and particles to detect RNA and protein in situ

The molecular heterogeneity of extracellular vesicles (EVs) and the co-isolation of physically similar particles, such as lipoproteins (LPs), confounds and limits the sensitivity of EV bulk biomarker characterization. Herein, we present a single-EV and particle (siEVP) protein and RNA assay (siEVP PRA) to simultaneously detect mRNAs, miRNAs, and proteins in subpopulations of EVs and LPs. The siEVP PRA immobilizes and sorts particles via positive immunoselection onto micropatterns and focuses biomolecular signals in situ. By detecting EVPs at a single-particle resolution, the siEVP PRA outperformed the sensitivities of bulk-analysis benchmark assays for RNA and protein. To assess the specificity of RNA detection in complex biofluids, EVs from various glioma cell lines were processed with small RNA sequencing, whereby two mRNAs and two miRNAs associated with glioblastoma multiforme (GBM) were chosen for cross-validation. Despite the presence of single-EV-LP co-isolates in serum, the siEVP PRA detected GBM-associated vesicular RNA profiles in GBM patient siEVPs. The siEVP PRA effectively examines intravesicular, intervesicular, and interparticle heterogeneity with diagnostic promise.

The lncRNA HOTAIR: a pleiotropic regulator of epithelial cell plasticity

The epithelial-to-mesenchymal transition (EMT) is a trans-differentiation process that endows epithelial cells with mesenchymal properties, including motility and invasion capacity; therefore, its aberrant reactivation in cancerous cells represents a critical step to gain a metastatic phenotype. The EMT is a dynamic program of cell plasticity; many partial EMT states can be, indeed, encountered and the full inverse mesenchymal-to-epithelial transition (MET) appears fundamental to colonize distant secondary sites. The EMT/MET dynamics is granted by a fine modulation of gene expression in response to intrinsic and extrinsic signals. In this complex scenario, long non-coding RNAs (lncRNAs) emerged as critical players. This review specifically focuses on the lncRNA HOTAIR, as a master regulator of epithelial cell plasticity and EMT in tumors. Molecular mechanisms controlling its expression in differentiated as well as trans-differentiated epithelial cells are highlighted here. Moreover, current knowledge about HOTAIR pleiotropic functions in regulation of both gene expression and protein activities are described. Furthermore, the relevance of the specific HOTAIR targeting and the current challenges of exploiting this lncRNA for therapeutic approaches to counteract the EMT are discussed.

Migrasomes, a new mode of intercellular communication

Migrasomes are newly discovered extracellular vesicles (EVs) that are formed in migrating cells and mediate intercellular communication. However, their size, biological generation, cargo packaging, transport, and effects on recipient cells by migrasomes are different from those of other EVs. In addition to mediating organ morphogenesis during zebrafish gastrulation, discarding damaged mitochondria, and lateral transport of mRNA and proteins, growing evidence has demonstrated that migrasomes mediate a variety of pathological processes. In this review, we summarize the discovery, mechanisms of formation, isolation, identification, and mediation of cellular communication in migrasomes. We discuss migrasome-mediated disease processes, such as osteoclast differentiation, proliferative vitreoretinopathy, tumor cell metastasis by PD-L1 transport, immune cell chemotaxis to the site of infection by chemokines, angiogenesis promotion via angiogenic factors by immune cells, and leukemic cells chemotaxis to the site of mesenchymal stromal cells. Moreover, as new EVs, we propose the potential of migrasomes for disease diagnosis and treatment. Video Abstract.

Exosomes as crucial emerging tools for intercellular communication with therapeutic potential in ovarian cancer

More than two-thirds of epithelial ovarian cancer (EOC) patients are diagnosed at advanced stages due to the lack of sensitive biomarkers. Currently, exosomes are intensively investigated as non-invasive cancer diagnostic markers. Exosomes are nanovesicles released in the extracellular milieu with the potential to modulate recipient cells' behavior. EOC cells release many altered exosomal cargoes that exhibit clinical relevance to tumor progression. Exosomes represent powerful therapeutic tools (drug carriers or vaccines), posing a promising option in clinical practice for curing EOC in the near future. In this review, we highlight the importance of exosomes in cell–cell communication, epithelial–mesenchymal transition (EMT), and their potential to serve as diagnostic and prognostic factors, particularly in EOC.

The exosome: a review of current therapeutic roles and capabilities in human reproduction

Exosomes are nano-vesicles (30-150 nm) which may be useful as therapeutic delivery vehicles and as diagnostic biomarkers. Exosomes are produced naturally within the human body and therefore are not prone to immunogenicity effects which would otherwise destroy unelicited foreign bodies. Clinically, they have been regarded as ideal candidates for applications relating to biomarker developments for the early detection of different diseases. Furthermore, exosomes may be of interest as potential drug delivery vehicles, which may improve factors such as bioavailability of loaded molecular cargo, side effect profiles, off-target effects, and pharmacokinetics of drug molecules. In this review, the therapeutic potential of exosomes and their use as clinical biomarkers for early diagnostics will be explored, alongside exosomes as therapeutic delivery vehicles. This review will evaluate techniques for cargo loading, and the capacity of loaded exosomes to improve various reproductive disease states. It becomes important, therefore, to consider factors such as loading efficiency, loading methods, cell viability, exosomal sources, exosome isolation, and the potential therapeutic benefits of exosomes. Issues related to targeted drug delivery will also be discussed. Finally, the variety of therapeutic cargo and the application of appropriate loading methods is explored, in the context of establishing clinical utility. Exosomes have more recently been widely accpeted as potential tools for disease diagnostics and the targeted delivery of certain therapeutic molecules-and in due time exosomes will be utilised more commonly within the clinical setting. Specifically, exosomal biomarkers can be identified and related to various detrimental conditions which occur during pregnancy. Considering, this review will explore the potential future of exosomes as both diagnostic tools and therapeutic delivery vehicles to treat related conditions, including the challenges which exist towards incorporating exosomes within the clinical environment to benefit patients.

Exosomes in Breast Cancer: Involvement in Tumor Dissemination and Prospects for Liquid Biopsy

In women, breast cancer (BC) is the most commonly diagnosed cancer (24.5%) and the leading cause of cancer death (15.5%). Understanding how this heterogeneous disease develops and the confirm mechanisms behind tumor progression is of utmost importance. Exosomes are long-range message vesicles that mediate communication between cells in physiological conditions but also in pathology, such as breast cancer. In recent years, there has been an exponential rise in the scientific studies reporting the change in morphology and cargo of tumor-derived exosomes. Due to the transfer of biologically active molecules, such as RNA (microRNA, long non-coding RNA, mRNA, etc.) and proteins (transcription factors, enzymes, etc.) into recipient cells, these lipid bilayer 30-150 nm vesicles activate numerous signaling pathways that promote tumor development. In this review, we attempt to shed light on exosomes' involvement in breast cancer pathogenesis (including epithelial-to-mesenchymal transition (EMT), tumor cell proliferation and motility, metastatic processes, angiogenesis stimulation, and immune system repression). Moreover, the potential use of exosomes as promising diagnostic biomarkers for liquid biopsy of breast cancer is also discussed.

Chick cranial neural crest cells release extracellular vesicles that are critical for their migration

The content and activity of extracellular vesicles purified from cell culture media or bodily fluids have been studied extensively; however, the physiological relevance of exosomes within normal biological systems is poorly characterized, particularly during development. Although exosomes released by invasive metastatic cells alter migration of neighboring cells in culture, it is unclear whether cancer cells misappropriate exosomes released by healthy differentiated cells or reactivate dormant developmental programs that include exosome cell-cell communication. Using chick cranial neural fold cultures, we show that migratory neural crest cells, a developmentally critical cell type and model for metastasis, release and deposit CD63-positive 30-100 nm particles into the extracellular environment. Neural crest cells contain ceramide-rich multivesicular bodies and produce larger vesicles positive for migrasome markers as well. We conclude that neural crest cells produce extracellular vesicles including exosomes and migrasomes. When Rab27a plasma membrane docking is inhibited, neural crest cells become less polarized and rounded, leading to a loss of directional migration and reduced speed. These results indicate that neural crest cell exosome release is critical for migration.

Exosome-Associated circRNAs as Key Regulators of EMT in Cancer

Epithelial-to-mesenchymal transition (EMT) is a dynamic program of cell plasticity aberrantly reactivated in cancer. The crosstalk between tumor cells and the tumoral microenvironment (TME) has a pivotal importance for the induction of the EMT and the progression toward a malignant phenotype. Notably, exosomes are key mediators of this crosstalk as vehicles of specific molecular signals that include the class of circular RNAs (circRNAs). This review specifically focuses on the role of exosome-associated circRNAs as key regulators of EMT in cancer. The relevance of these molecules in regulating the intercellular communication in TME and tumor progression is highlighted. Moreover, the here-presented evidence indicates that exosome-associated circRNA modulation should be taken in account for cancer diagnostic and therapeutic approaches.

Emerging roles of exosome-derived biomarkers in cancer theranostics: messages from novel protein targets

Effective biomarkers that guide therapeutics with limited adverse effects, have emerged as attractive research topics in cancer diagnosis and treatment. Cancer-derived exosomes, a type of extracellular vesicles representing molecular signatures of cells of origin, could serve as stable reservoirs for potential biomarkers (i.e., proteins, nucleic acids) in non-invasive cancer diagnosis and prognosis. In this review, the physiological and pathological roles of exosomes and their protein components in facilitating tumorigenesis are highlighted. Exosomes carrying proteins can participate in tumor development and progression through multiple signaling pathways, including EMT, invasion and metastasis. Meanwhile, the practical applications of exosomal proteins in detecting and monitoring several solid-tumor cancers (including lung, breast, pancreatic, colorectal and prostate cancers) were also summarized. More clinically relevant, exosomal proteins play pivotal roles in transmitting oncogenic potential or resistance to therapies in recipient cells, which might further support therapeutic strategy determinations.

Exosomal LBH inhibits epithelial-mesenchymal transition and angiogenesis in nasopharyngeal carcinoma via downregulating VEGFA signaling

The limb-bud and heart (LBH) gene was reported to suppress nasopharyngeal carcinoma (NPC) progression in our previous study. Distant metastasis predominantly accounts for the unsatisfactory prognosis of NPC treatment, in which epithelial-mesenchymal transition (EMT) and tumor angiogenesis are of great significance. The roles of exosomes in mediating NPC progression have been highlighted in recent researches, and attempts have been made to explore the clinical application of NPC exosomes. Here we investigated the function of the LBH gene in NPC exosomes, and its potential mechanism. NPC xenografts were constructed, showing that vascular endothelial growth factor A (VEGFA) expression and neovascularity were attenuated by LBH overexpression, together with diminished EMT progression. NPC-derived exosomes were isolated, identified and applied for in vitro/in vivo experiments, and the exosomal distribution of LBH was elevated in exosomes derived from LBH-upregulated cells. Ectopic LBH, αB-crystallin (CRYAB) and VEGFA expression was induced by lentiviral infection or plasmid transfection to explore their functions in modulating EMT and angiogenesis in NPC. The addition of LBH+ NPC exosomes during a Matrigel plug assay in mice suppressed in vivo angiogenesis, and the treatment of human umbilical vein endothelial cells (HUVECs) with LBH+ NPC exosomes inhibited cellular proliferation, migration and tube formation. The interactions among LBH, CRYAB and VEGFA were confirmed by colocalization and fluorescence resonance energy transfer (FRET) assays, and extracellular VEGFA secretion from both HUVECs and NPC cells under the treatment with LBH+ NPC exosomes was diminished according to ELISA results. We concluded that exosomal LBH inhibits EMT progression and angiogenesis in the NPC microenvironment, and that its effects are partially implemented by modulation of VEGFA expression, secretion and related signaling. Thus, LBH could serve as a promising therapeutic target in VEGFA-focused NPC treatment.

Extracellular vesicle-mediated transport: Reprogramming a tumor microenvironment conducive with breast cancer progression and metastasis

•

Extracellular vesicles’ (EVs) role in breast tumor microenvironment and pre-metastatic niche development.

•

Breast cancer EV-mediated transmission of pro-metastatic and drug-resistant phenotypes.

•

Precision medicine with EVs as biomarkers and delivery vehicles for drug and anticancer genetic material.

Breast cancer metastatic progression to critical secondary sites is the second leading cause of cancer-related mortality in women. While existing therapies are highly effective in combating primary tumors, metastatic disease is generally deemed incurable with a median survival of only 2, 3 years. Extensive efforts have focused on identifying metastatic contributory targets for therapeutic antagonism and prevention to improve patient survivability. Excessive breast cancer release of extracellular vesicles (EVs), whose contents stimulate a metastatic phenotype, represents a promising target. Complex breast cancer intercellular communication networks are based on EV transport and transference of molecular information is in bulk resulting in complete reprogramming events within recipient cells. Other breast cancer cells can acquire aggressive phenotypes, endothelial cells can be induced to undergo tubule formation, and immune cells can be neutralized. Recent advancements continue to implicate the critical role EVs play in cultivating a tumor microenvironment tailored to cancer proliferation, metastasis, immune evasion, and conference of drug resistance. This literature review serves to frame the role of EV transport in breast cancer progression and metastasis. The following five sections will be addressed: (1) Intercellular communication in developing a tumor microenvironment & pre-metastatic niche. (2) Induction of the epithelial-to-mesenchymal transition (EMT). (3). Immune suppression & evasion. (4) Transmission of drug resistance mechanisms. (5) Precision medicine: clinical applications of EVs.

Extracellular Vesicles Tropism: A Comparative Study between Passive Innate Tropism and the Active Engineered Targeting Capability of Lymphocyte-Derived EVs

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of phenomena responsible for cell proliferation and death. To this purpose, here, a thorough immuno-phenotypic characterization of B-cell EV membranes is presented. Furthermore, the cellular membrane of B lymphocytes, Burkitt lymphoma, and human myeloid leukemic cells were characterized through cytofluorimetry assays and fluorescent microscopy analysis. Through cytotoxicity and internalization tests, the tropism of B lymphocyte-derived EVs was investigated toward the parental cell line and two different cancer cell lines. In this study, an innate capability of passive targeting of the native EVs was distinguished from the active targeting capability of monoclonal antibody-engineered EVs, able to selectively drive the vesicles, enhancing their internalization into the target cancer cells. In particular, the specific targeting ability of anti-CD20 engineered EVs towards Daudi cells, highly expressing CD20 marker on their cell membrane, was proved, while almost no internalization events were observed in HL60 cells, since they did not express an appreciable amount of the CD20 marker on their plasma membranes.

Hsp70-containing extracellular vesicles are capable of activating of adaptive immunity in models of mouse melanoma and colon carcinoma

The release of Hsp70 chaperone from tumor cells is found to trigger the full-scale anti-cancer immune response. Such release and the proper immune reaction can be induced by the delivery of recombinant Hsp70 to a tumor and we sought to explore how the endogenous Hsp70 can be transported to extracellular space leading to the burst of anti-cancer activity. Hsp70 transport mechanisms were studied by analyzing its intracellular tracks with Rab proteins as well as by using specific inhibitors of membrane domains. To study Hsp70 forms released from cells we employed the assay consisting of two affinity chromatography methods. Hsp70 content in culture medium and extracellular vesicles (EVs) was measured with the aid of ELISA. The properties and composition of EVs were assessed using nanoparticle tracking analysis and immunoblotting. The activity of immune cells was studied using an assay of cytotoxic lymphocytes, and for in vivo studies we employed methods of affinity separation of lymphocyte fractions. Analyzing B16 melanoma cells treated with recombinant Hsp70 we found that the chaperone triggered extracellular transport of its endogenous analog in soluble and enclosed in EVs forms; both species efficiently penetrated adjacent cells and this secondary transport was corroborated with the strong increase of Natural Killer (NK) cell toxicity towards melanoma. When B16 and CT-26 colon cancer cells before their injection in animals were treated with Hsp70-enriched EVs, a powerful anti-cancer effect was observed as shown by a two-fold reduction in tumor growth rate and elevation of life span. We found that the immunomodulatory effect was due to the enhancement of the CD8-positive response and anti-tumor cytokine accumulation; supporting this there was no delay in CT-26 tumor growth when Hsp70-enriched EVs were grafted in nude mice. Importantly, pre-treatment of B16 cells with Hsp70-bearing EVs resulted in a decline of arginase-1-positive macrophages, showing no generation of tumor-associated macrophages. In conclusion, Hsp70-containing EVs generated by specifically treated cancer cells give a full-scale and effective pattern of anti-tumor immune responses.

Exosomes and Brain Metastases: A Review on Their Role and Potential Applications

Brain metastases (BM) are a frequent complication in patients with advanced stages of cancer, associated with impairment of the neurological function, quality of life, prognosis, and survival. BM treatment consists of a combination of the available cancer therapies, such as surgery, radiotherapy, chemotherapy, immunotherapy and targeted therapies. Even so, cancer patients with BM are still linked to poor prognosis, with overall survival being reported as 12 months or less. Intercellular communication has a pivotal role in the development of metastases, therefore, it has been extensively studied not only to better understand the metastization process, but also to further develop new therapeutic strategies. Exosomes have emerged as key players in intercellular communication being potential therapeutic targets, drug delivery systems (DDS) or biomarkers. In this Review, we focus on the role of these extracellular vesicles (EVs) in BM formation and their promising application in the development of new BM therapeutic strategies.

Exosomes and organ-specific metastasis

The transmission of information between tumor cells and other cell types in the tumor microenvironment plays an important role in tumor metastasis and is critically modulated by exosomes and other mediators. Tumor-derived exosomes can promote epithelial-mesenchymal transition, angiogenesis, immune escape, formation of the pre-metastatic microenvironment, and transmission of drug-resistant molecules, thereby promoting tumor growth, invasion, and metastasis. Integrins are important regulatory molecules on exosomes that can locate metastatic cells at the initial stage of metastasis and show good organotropism. This fact suggests that a clear understanding of the roles of exosomal integrins will be beneficial for future clinical applications. Follow-up studies on exosomes using continuously updated purification techniques and identification methods are extremely important. In addition to their potential as cancer biomarkers, exosomes also provide new research directions for precision medicine. Currently, exosomes have potential value in disease treatment and provide clinicians with more meaningful judgment standards.

Integration of Functional Imaging, Cytometry, and Unbiased Proteomics Reveals New Features of Endothelial-to-Mesenchymal Transition in Ischemic Mitral Valve Regurgitation in Human Patients

Background: Following myocardial infarction, mitral regurgitation (MR) is a common complication. Previous animal studies demonstrated the association of endothelial-to-mesenchymal transition (EndMT) with mitral valve (MV) remodeling. Nevertheless, little is known about how MV tissue responds to ischemic heart changes in humans.

Methods: MVs were obtained by the Cardiothoracic Surgical Trials Network from 17 patients with ischemic mitral regurgitation (IMR). Echo-doppler imaging assessed MV function at time of resection. Cryosections of MVs were analyzed using a multi-faceted histology and immunofluorescence examination of cell populations. MVs were further analyzed using unbiased label-free proteomics. Echo-Doppler imaging, histo-cytometry measures and proteomic analysis were then integrated.

Results: MVs from patients with greater MR exhibited proteomic changes associated with proteolysis-, inflammatory- and oxidative stress-related processes compared to MVs with less MR. Cryosections of MVs from patients with IMR displayed activated valvular interstitial cells (aVICs) and double positive CD31+ αSMA+ cells, a hallmark of EndMT. Univariable and multivariable association with echocardiography measures revealed a positive correlation of MR severity with both cellular and geometric changes (e.g., aVICs, EndMT, leaflet thickness, leaflet tenting). Finally, proteomic changes associated with EndMT showed gene-ontology enrichment in vesicle-, inflammatory- and oxidative stress-related processes. This discovery approach indicated new candidate proteins associated with EndMT regulation in IMR.

Conclusion: We describe an atypical cellular composition and distinctive proteome of human MVs from patients with IMR, which highlighted new candidate proteins implicated in EndMT-related processes, associated with maladaptive MV fibrotic remodeling.

Tumor-derived exosomal circRNA051239 promotes proliferation and migration of epithelial ovarian cancer

Recent studies have shown the involvement of exosomes in intercellular communication during tumor progression. Circular RNAs (circRNAs) can be packaged into exosomes for extracellular communication, however, the possible effects of exosomal circRNAs in epithelial ovarian cancer (EOC) cells with high metastatic potential have been rarely studied. In this study, we identified exosomal circRNA051239 from high-metastatic ovarian cancer SKOV3.ip cells and subsequently analyzed circRNA051239 levels in both EOC tissues and exosomes derived from plasma and cells by qRT-PCR. A variety of in vitro assays were employed to observe the effects of exosomal circRNA051239 derived from high-metastatic ovarian cancer SKOV3.ip cells on low-metastatic ovarian cancer SKOV3 cells. Bioinformatics analysis and luciferase activity assays were further utilized to confirm the relationship between circRNA051239, miR-509-5p and PRSS3. As a result, circRNA051239 expression was increased in tissues and plasma exosomes from EOC patients. Moreover, si-circRNA051239-Exo (exosomes derived from circRNA051239 knockdown SKOV3.ip cells) inhibited the proliferation, migration as well as invasion of SKOV3 cells. Mechanistically, circRNA051239 functioned as a competitive endogenous RNA (ceRNA) by sponging miR-509-5p to facilitate PRSS3 expression. Exosomal circRNA051239 derived from high-metastatic ovarian cancer SKOV3.ip cells promoted the progression of low-metastatic ovarian cancer SKOV3 cells. Collectively, these outcomes implicated that higher metastatic EOC cells can confer this potential to lower metastatic potential via exosomal circRNA051239, causing enhanced proliferative, migratory and invasive capacities in recipient cells.

Non-invasive detection of epithelial mesenchymal transition phenotype and metastatic dissemination of lung cancer by liquid biopsy

The occurrence of phenotype switch from an epithelial to a mesenchymal cell state during the activation of the epithelial mesenchymal transition (EMT) program in cancer cells has been closely associated with the generation of invasive tumor cells that contribute to metastatic dissemination and treatment failure. Liquid biopsy represents an emergent non-invasive tool that may improve our understanding of the molecular events leading to cancer progression and initiating the metastatic cascade through the dynamic analysis of tumor-derived components isolated from body fluids. The present review will primarily focus on the applications of liquid biopsy in lung cancer patients for identifying EMT signature, elucidating molecular mechanisms underlying the acquisition of an invasive phenotype and detecting new targets for therapy.

High-Throughput Simultaneous mRNA Profiling Using nCounter Technology Demonstrates That Extracellular Vesicles Contain Different mRNA Transcripts Than Their Parental Prostate Cancer Cells

Extracellular vesicles (EVs) are nano-sized lipid bilayer encapsulated particles with a molecular cargo that appears to play important roles within the human body, such as in cell-to-cell communication. Unraveling the composition of EV cargos remains one of the most fundamental steps toward understanding the role of EVs in intercellular communication and the discovery of new biomarkers. One of the unmet needs in this field is the lack of a robust, sensitive, and multiplexed method for EV mRNA profiling. We established a new protocol using the NanoString low RNA input nCounter assay by which the targeted mRNA transcripts in EVs can be efficiently and specifically amplified and then assayed for 770 mRNAs in one reaction. Prostate cancer cells with epithelial (PC3-Epi) or mesenchymal (PC3-EMT) phenotypes and their progeny EVs were analyzed by the same panel. Among these mRNAs, 157 were detected in PC3-Epi EVs and 564 were detected in PC3-EMT EVs. NOTCH1 was the most significantly abundant mRNA transcripts in PC3-EMT EVs compared to PC3-Epi EVs. Our results demonstrated that when cells undergo epithelial-to-mesenchymal transition (EMT), a more active loading of cancer progression-related mRNA transcripts may occur. The mRNA cargos of EVs derived from mesenchymal prostate cancer cells may contribute to the pro-EMT function. We found that mRNA transcripts are different in progeny EVs compared to parental cells. EV cargos are not completely reflective of their cell origin, and the underlying mechanism of cargo sorting is complicated and needs to be further elucidated.

Hypoxia-driven secretion of extracellular matrix proteins in the exosomes reflects the asymptomatic pathology of rotator cuff tendinopathies

The major hallmark of rotator cuff tendinopathies (RCT) is the disorganization of the tendon extracellular matrix (ECM), which is due to a decrease in the ratio of collagen I to collagen III. In addition, the pathology of the tendon matrisome remains asymptomatic, and hypoxia has been identified to be the priming signal to initiate the molecular pathology of RCT. Also, the secretome content of hypoxia-challenged tendon cells (tenocytes) reflects the pathological status of RCT. With this background, the present study was designed to establish the expression status and molecular crosstalk of the ECM component proteins contained in the exosomes of the hypoxia-challenged swine tenocytes. The mass spectrometry analysis revealed the upregulation of COL1A2, P4HA1, PRDX2, P3H1, COL6A1, PPIB, LCN1, and COL3A1 and the downregulation of COLA12, PDIA4, COLG, FN1, CTSK, and TNC in the exosomes of hypoxic tenocytes. These proteins interact with diverse proteins and operate multiple pathways associated with ECM homeostasis and repair as determined by NetworkAnalyst. The functional analysis of these proteins reflects the pathology of tendon ECM, which is correlated with the asymptomatic phase of RCT. Understanding the signaling mediated by these proteins would reveal the underlying molecular pathology and offers translational significance in the diagnosis and management of RCT.

Extracellular Vesicles Regulate Cancer Metastasis

Metastatic cancer is a complex disease associated with poor prognosis and accounts for the majority of cancer related deaths. To date, many of the molecular mechanisms driving metastatic disease remain elusive and require further investigation for the development of effective treatment strategies. Recent studies have shown that extracellular vesicles (EVs) can be exploited by tumors to assist in cancer cell growth, proliferation, migration, invasion and metastasis. Cancer cells have proven efficient in educating fibroblasts, within their microenvironment, to secrete EVs as communicative vessels for mediating phenotypic changes in recipient cells. Using this vesicular delivery system, cancer cells can establish a new metastatic niche within distant sites, away from the primary tumor, thus favoring cancer progression. These findings demonstrate the availability of a new route for therapeutic intervention in the inhibition of cancer dissemination. Although, several approaches to target cancer cell secretion of EVs are detailed in the literature, there is still no defined way to currently apply them in clinical settings. Hence, further studies are required to unravel the molecular mechanisms of metastasis - governed by the establishment and release of cancer associated EVs.

Therapeutic Potential of Exosomes in Pulmonary Fibrosis

Pulmonary fibrosis is closely associated with the recruitment of fibroblasts from capillary vessels with damaged endothelial cells, the epithelial mesenchymal transition (EMT) of type II alveolar epithelial cells, and the transformation of fibroblasts to myofibroblasts. Recent studies suggest that EMT is a key factor in the pathogenesis of pulmonary fibrosis, as the disruption of EMT-related effector molecules can inhibit the occurrence and development of PF. With the numerous advancements made in molecular biology in recent years, researchers have discovered that exosomes and their cargos, such as miRNAs, lncRNAs, and proteins, can promote or inhibit the EMT, modulate the transformation of fibroblasts into myofibroblasts, contribute to the proliferation of fibroblasts and promote immunoregulatory and mitochondrial damage during pulmonary fibrosis. Exosomes are key factors regulating the differentiation of bone marrow mesenchymal stem cells (BMSCs) into myofibroblasts. Interestingly, exosomes derived from BMSCs under pathological and physiological conditions may promote or inhibit the EMT of type II alveolar epithelial cells and the transformation of fibroblasts into myofibroblasts to regulate pulmonary fibrosis. Thus, exosomes may become a new direction in the study of drugs for the treatment of pulmonary fibrosis.

Mechanisms of Action of EGFR Tyrosine Kinase Receptor Incorporated in Extracellular Vesicles

EGFR and some of the cognate ligands extensively traffic in extracellular vesicles (EVs) from different biogenesis pathways. EGFR belongs to a family of four homologous tyrosine kinase receptors (TKRs). This family are one of the major drivers of cancer and is involved in several of the most frequent malignancies such as non-small cell lung cancer, breast cancer, colorectal cancer and ovarian cancer. The carrier EVs exert crucial biological effects on recipient cells, impacting immunity, pre-metastatic niche preparation, angiogenesis, cancer cell stemness and horizontal oncogene transfer. While EV-mediated EGFR signalling is important to EGFR-driven cancers, little is known about the precise mechanisms by which TKRs incorporated in EVs play their biological role, their stoichiometry and associations to other proteins relevant to cancer pathology and EV biogenesis, and their means of incorporation in the target cell. In addition, it remains unclear whether different subtypes of EVs incorporate different complexes of TKRs with specific functions. A raft of high spatial and temporal resolution methods is emerging that could solve these and other questions regarding the activity of EGFR and its ligands in EVs. More importantly, methods are emerging to block or mitigate EV activity to suppress cancer progression and drug resistance. By highlighting key findings and areas that remain obscure at the intersection of EGFR signalling and EV action, we hope to cross-fertilise the two fields and speed up the application of novel techniques and paradigms to both.

Cancer-Associated Fibroblasts Differentiated by Exosomes Isolated from Cancer Cells Promote Cancer Cell Invasion

Cancer-associated fibroblasts (CAFs) in the cancer microenvironment play an essential role in metastasis. Differentiation of endothelial cells into CAFs is induced by cancer cell-derived exosomes secreted from cancer cells that transfer molecular signals to surrounding cells. Differentiated CAFs facilitate migration of cancer cells to different regions through promoting extracellular matrix (ECM) modifications. However, in vitro models in which endothelial cells exposed to cancer cell-derived exosomes secreted from various cancer cell types differentiate into CAFs or a microenvironmentally controlled model for investigating cancer cell invasion by CAFs have not yet been studied. In this study, we propose a three-dimensional in vitro cancer cell invasion model for real-time monitoring of the process of forming a cancer invasion site through CAFs induced by exosomes isolated from three types of cancer cell lines. The invasiveness of cancer cells with CAFs induced by cancer cell-derived exosomes (eCAFs) was significantly higher than that of CAFs induced by cancer cells (cCAFs) through physiological and genetic manner. In addition, different genetic tendencies of the invasion process were observed in the process of invading cancer cells according to CAFs. Our 3D microfluidic platform helps to identify specific interactions among multiple factors within the cancer microenvironment and provides a model for cancer drug development.

Total Blood Exosomes in Breast Cancer: Potential Role in Crucial Steps of Tumorigenesis

Exosomes are crucial players in cell-to-cell communication and are involved in tumorigenesis. There are two fractions of blood circulating exosomes: free and cell-surface-associated. Here, we compared the effect of total blood exosomes (contain plasma exosomes and blood cell-surface-associated exosomes) and plasma exosomes from breast cancer patients (BCPs, n = 43) and healthy females (HFs, n = 35) on crucial steps of tumor progression. Exosomes were isolated by ultrafiltration, followed by ultracentrifugation, and characterized by cryo-electron microscopy (cryo-EM), nanoparticle tracking analysis, and flow cytometry. Cryo-EM revealed a wider spectrum of exosome morphology with lipid bilayers and vesicular internal structures in the HF total blood in comparison with plasma. No differences in the morphology of both exosomes fractions were detected in BCP blood. The plasma exosomes and total blood exosomes of BCPs had different expression levels of tumor-associated miR-92a and miR-25-3p, induced angiogenesis and epithelial-to-mesenchymal transition (EMT), and increased the number of migrating pseudo-normal breast cells and the total migration path length of cancer cells. The multidirectional effects of HF total blood exosomes on tumor dissemination were revealed; they suppress the angiogenesis and total migration path length of MCF10A, but stimulate EMT and increase the number of migrating MCF10A and the total path length of SKBR3 cells. In addition, HF plasma exosomes enhance the metastasis-promoting properties of SKBR3 cells and stimulate angiogenesis. Both cell-free and blood cell-surface-associated exosomes are involved in the crucial stages of carcinogenesis: the initiation of EMT and the stimulation of proliferation, cell migration, and angiogenesis. Thus, for the estimation of the diagnostic/prognostic significance of circulating exosomes in the blood of cancer patients more correctly, the total blood exosomes, which consist of plasma exosomes and blood cell-surface-associated exosomes should be used.

Detection of EGFR Mutations Using Bronchial Washing-Derived Extracellular Vesicles in Patients with Non-Small-Cell Lung Carcinoma

Simple Summary

Considering the spatiotemporal heterogeneity, more frequent monitoring of the disease progress using less-invasive liquid biopsy technologies is highly desired. Here, we demonstrate that epidermal growth factor receptor (EGFR) mutations could be readily detected from minimally invasive bronchial washing (BW)-derived EVs with good accuracy. The acquisition of T790M resistance mutation was detected earlier in BW-derived EVs than in plasma or tissue samples. The longitudinal analysis of BW-derived EVs showed excellent correlation with the disease progression measured by CT images. We demonstrate the clinical potential of BW-derived EVs as a liquid-biopsy sample for prognosis and precision medicine in patients with lung cancer.

Abstract

The detection of epidermal growth factor receptor (EGFR) mutation, based on tissue biopsy samples, provides a valuable guideline for the prognosis and precision medicine in patients with lung cancer. In this study, we aimed to examine minimally invasive bronchial washing (BW)-derived extracellular vesicles (EVs) for EGFR mutation analysis in patients with lung cancer. A lab-on-a-disc equipped with a filter with 20-nm pore diameter, Exo-Disc, was used to enrich EVs in BW samples. The overall detection sensitivity of EGFR mutations in 55 BW-derived samples was 89.7% and 31.0% for EV-derived DNA (EV-DNA) and EV-excluded cell free-DNA (EV-X-cfDNA), respectively, with 100% specificity. The detection rate of T790M in 13 matched samples was 61.5%, 10.0%, and 30.8% from BW-derived EV-DNA, plasma-derived cfDNA, and tissue samples, respectively. The acquisition of T790M resistance mutation was detected earlier in BW-derived EVs than plasma or tissue samples. The longitudinal analysis of BW-derived EVs showed excellent correlation with the disease progression measured by CT images. The EGFR mutations can be readily detected in BW-derived EVs, which demonstrates their clinical potential as a liquid-biopsy sample that may aid precise management, including assessment of the treatment response and drug resistance in patients with lung cancer.

Detection of mitochondria-pertinent components in exosomes

We screened cell line and plasma-derived exosomes for molecules that localize to mitochondria or that reflect mitochondrial integrity. SH-SY5Y cell-derived exosomes contained humanin, citrate synthase, and fibroblast growth factor 21 protein, and plasma-derived exosomes contained humanin, voltage-dependent anion-selective channel 1, and transcription factor A protein. Nuclear mitochondrial (NUMT) DNA complicated analyses of mitochondrial DNA (mtDNA), which otherwise suggested exosomes contain at most very low amounts of extended mtDNA sequences but likely contain degraded pieces of mtDNA. Cell and plasma-derived exosomes contained several mtDNA-derived mRNA sequences, including those for ND2, CO2, and humanin. These results can guide exosome-focused, mitochondria-pertinent biomarker development.

Interplay Between V-ATPase G1 and Small EV-miRNAs Modulates ERK1/2 Activation in GBM Stem Cells and Nonneoplastic Milieu

The ATP6V1G1 subunit (V1G1) of the vacuolar proton ATPase (V-ATPase) pump is crucial for glioma stem cells (GSC) maintenance and in vivo tumorigenicity. Moreover, V-ATPase reprograms the tumor microenvironment through acidification and release of extracellular vesicles (EV). Therefore, we investigated the role of V1G1 in GSC small EVs and their effects on primary brain cultures. To this end, small EVs were isolated from patients-derived GSCs grown as neurospheres (NS) with high (V1G1^HIGH-NS) or low (V1G1^LOW-NS) V1G1 expression and analyzed for V-ATPase subunits presence, miRNA contents, and cellular responses in recipient cultures. Our results show that NS-derived small EVs stimulate proliferation and motility of recipient cells, with small EV derived from V1G1^HIGH-NS showing the most pronounced activity. This involved activation of ERK1/2 signaling, in a response reversed by V-ATPase inhibition in NS-producing small EV. The miRNA profile of V1G1^HIGH-NS-derived small EVs differed significantly from that of V1G1^LOW-NS, which included miRNAs predicted to target MAPK/ERK signaling. Mechanistically, forced expression of a MAPK-targeting pool of miRNAs in recipient cells suppressed MAPK/ERK pathway activation and blunted the prooncogenic effects of V1G1^HIGH small EV. These findings propose that the GSC influences the brain milieu through a V1G1-coordinated EVs release of MAPK/ERK-targeting miRNAs. Interfering with V-ATPase activity could prevent ERK-dependent oncogenic reprogramming of the microenvironment, potentially hampering local GBM infiltration. IMPLICATIONS: Our data identify a novel molecular mechanism of gliomagenesis specific of the GBM stem cell niche, which coordinates a V-ATPase-dependent reprogramming of the brain microenvironment through the release of specialized EVs.

Intrinsic and Extrinsic Modulators of the Epithelial to Mesenchymal Transition: Driving the Fate of Tumor Microenvironment

The epithelial to mesenchymal transition (EMT) is an evolutionarily conserved process. In cancer, EMT can activate biochemical changes in tumor cells that enable the destruction of the cellular polarity, leading to the acquisition of invasive capabilities. EMT regulation can be triggered by intrinsic and extrinsic signaling, allowing the tumor to adapt to the microenvironment demand in the different stages of tumor progression. In concomitance, tumor cells undergoing EMT actively interact with the surrounding tumor microenvironment (TME) constituted by cell components and extracellular matrix as well as cell secretome elements. As a result, the TME is in turn modulated by the EMT process toward an aggressive behavior. The current review presents the intrinsic and extrinsic modulators of EMT and their relationship with the TME, focusing on the non-cell-derived components, such as secreted metabolites, extracellular matrix, as well as extracellular vesicles. Moreover, we explore how these modulators can be suitable targets for anticancer therapy and personalized medicine.

Tumor-Derived Exosomes in Immunosuppression and Immunotherapy

Tumor-derived exosomes (TEX) are involved in cancer development, metastasis, and disease progression. They can modulate angiogenesis to elevate the malignant degree of tumor cells. TEX carry immunosuppressive factors affecting the antitumor activities of immune cells. Tumor cells as well as immune cells secrete immunologically active exosomes which affect intercellular communication, antigen presentation, activation of immune cells, and immune surveillance. Cell proliferation and immune response suppression create a favorable microenvironment for tumor. TEX can inhibit immune cell proliferation, induce apoptosis of activated CD8+ Teffs, suppress NK cell activity, interfere with monocyte differentiation, and promote Treg as well as MDSC expansion. Exosomes of microenvironment cells may also contribute to the development of drug resistance in cancer therapy. An important role of TEX in modulating the sensitivity of tumor cells to immunotherapy is a promising area of research to make the cancer therapy more successful.

Long filopodia and tunneling nanotubes define new phenotypes of breast cancer cells in 3D cultures

Cancer cell invasion into the surrounding extracellular matrix (ECM) takes place when cell-cell junctions are disrupted upon epithelial-to-mesenchymal transition (EMT). Both cancer cell-stroma and cell-cell crosstalk are essential to support the continuous tumor invasion. Cancer cells release microvesicles and exosomes containing bioactive molecules and signal peptides, which are recruited by neighboring cells or carried to distant sites, thus supporting intercellular communication and cargo transfer. Besides this indirect communication mode, cancer cells can develop cytoplasmic intercellular protrusions or tunneling nanotubes (TNTs), which allow the direct communication and molecular exchange between connected distinct cells. Using scanning electron microscopy (SEM) we show for the first time that MDA-MB-231 (high metastatic potential) and shERβ MDA-MB-231 (low metastatic potential) breast cancer cells cultured on fibronectin and collagen type I or 17β-estradiol (E2) develop TNTs and very long flexible filopodia. Interestingly, the less aggressive shERβ MDA-MB-231 cells treated with E2 in 3D collagen matrix showed the highest development of TNTs and filopodia. TNTs were often associated to adhering exosomes and microvesicles surfing from one cell to another, but no filopodia exhibited vesicle-like cytoplasmic structures on their surface. Moreover, E2 affected the expression of matrix macromolecules and cell effectors mostly in the presence of ERβ. Our novel data highlights the significance of matrix substrates and the presence of E2 and ERβ in the formation of cellular protrusion and the production of surface structures, defining novel phenotypes that unravel nodal reports for breast cancer progression.

Revisiting Cancer Stem Cells as the Origin of Cancer-Associated Cells in the Tumor Microenvironment: A Hypothetical View from the Potential of iPSCs

The tumor microenvironment (TME) has an essential role in tumor initiation and development. Tumor cells are considered to actively create their microenvironment during tumorigenesis and tumor development. The TME contains multiple types of stromal cells, cancer-associated fibroblasts (CAFs), Tumor endothelial cells (TECs), tumor-associated adipocytes (TAAs), tumor-associated macrophages (TAMs) and others. These cells work together and with the extracellular matrix (ECM) and many other factors to coordinately contribute to tumor growth and maintenance. Although the types and functions of TME cells are well understood, the origin of these cells is still obscure. Many scientists have tried to demonstrate the origin of these cells. Some researchers postulated that TME cells originated from surrounding normal tissues, and others demonstrated that the origin is cancer cells. Recent evidence demonstrates that cancer stem cells (CSCs) have differentiation abilities to generate the original lineage cells for promoting tumor growth and metastasis. The differentiation of CSCs into tumor stromal cells provides a new dimension that explains tumor heterogeneity. Using induced pluripotent stem cells (iPSCs), our group postulates that CSCs could be one of the key sources of CAFs, TECs, TAAs, and TAMs as well as the descendants, which support the self-renewal potential of the cells and exhibit heterogeneity. In this review, we summarize TME components, their interactions within the TME and their insight into cancer therapy. Especially, we focus on the TME cells and their possible origin and also discuss the multi-lineage differentiation potentials of CSCs exploiting iPSCs to create a society of cells in cancer tissues including TME.

The Emerging Roles of Exosomes as EMT Regulators in Cancer

Epithelial–mesenchymal transition (EMT) causes epithelial cells to lose their polarity and adhesion property, and endows them with migratory and invasive properties to enable them to become mesenchymal stem cells. EMT occurs throughout embryonic development, during wound healing, and in various pathological processes, including tumor progression. Considerable research in the last few decades has revealed that EMT is invariably related to tumor aggressiveness and metastasis. Apart from the interactions between numerous intracellular signaling pathways known to regulate EMT, extracellular modulators in the tumor microenvironment also influence tumor cells to undergo EMT, with extracellular vesicles (EVs) receiving increasing attention as EMT inducers. EVs comprise exosomes and microvesicles that carry proteins, nucleic acids, lipids, and other small molecules to stimulate EMT in cells. Among EVs, exosomes have been investigated in many studies, and their role has been found to be significant with respect to regulating intercellular communications. In this review, we summarize recent studies on exosomes and their cargoes that induce cancer-associated EMT. Furthermore, we describe the possible applications of exosomes as promising therapeutic strategies.

Exosomes in Prostate Cancer Diagnosis, Prognosis and Therapy

Prostate cancer (PCa) is the second most common cause of cancer-related mortality among men in the developed world. Conventional anti-PCa therapies are not effective for patients with advanced and/or metastatic disease. In most cases, cancer therapies fail due to an incomplete depletion of tumor cells, resulting in tumor relapse. Exosomes are involved in tumor progression, promoting the angiogenesis and migration of tumor cells during metastasis. These structures contribute to the dissemination of pathogenic agents through interaction with recipient cells. Exosomes may deliver molecules that are able to induce the transdifferentiation process, known as “epithelial to mesenchymal transition”. The composition of exosomes and the associated possibilities of interacting with cells make exosomes multifaceted regulators of cancer development. Extracellular vesicles have biophysical properties, such as stability, biocompatibility, permeability, low toxicity and low immunogenicity, which are key for the successful development of an innovative drug delivery system. They have an enhanced circulation stability and bio-barrier permeation ability, and they can therefore be used as effective chemotherapeutic carriers to improve the regulation of target tissues and organs. Exosomes have the capacity to deliver different types of cargo and to target specific cells. Chemotherapeutics, natural products and RNA have been encapsulated for the treatment of prostate cancers.

Tspan8-Tumor Extracellular Vesicle-Induced Endothelial Cell and Fibroblast Remodeling Relies on the Target Cell-Selective Response

Tumor cell-derived extracellular vesicles (TEX) expressing tetraspanin Tspan8-alpha4/beta1 support angiogenesis. Tspan8-alpha6/beta4 facilitates lung premetastatic niche establishment. TEX-promoted target reprogramming is still being disputed, we explored rat endothelial cell (EC) and lung fibroblast (Fb) mRNA and miRNA profile changes after coculture with TEX. TEX were derived from non-metastatic BSp73AS (AS) or metastatic BSp73ASML (ASML) rat tumor lines transfected with Tspan8 (AS-Tspan8) or Tspan8-shRNA (ASML-Tspan8kd). mRNA was analyzed by deep sequencing and miRNA by array analysis of EC and Fb before and after coculture with TEX. EC and Fb responded more vigorously to AS-Tspan8- than AS-TEX. Though EC and Fb responses differed, both cell lines predominantly responded to membrane receptor activation with upregulation and activation of signaling molecules and transcription factors. Minor TEX-initiated changes in the miRNA profile relied, at least partly, on long noncoding RNA (lncRNA) that also affected chromosome organization and mRNA processing. These analyses uncovered three important points. TEX activate target cell autonomous programs. Responses are initiated by TEX targeting units and are target cell-specific. The strong TEX-promoted lncRNA impact reflects lncRNA shuttling and location-dependent distinct activities. These informations urge for an in depth exploration on the mode of TEX-initiated target cell-specific remodeling including, as a major factor, lncRNA.

Phosphorylated Rasal2 facilitates breast cancer progression

BACKGROUND

Rasal2 has diametric effects on progression of oestrogen receptor-positive (ER+) and -negative (ER-) breast cancers. The relevant causes are unknown. It is also unknown whether the effects of Rasal2 are mediated by an exosome-transport process.

METHODS

Exosomes were purified from breast cancer cells and identified by transmission electron microscopy and flow cytometry analysis. In vivo and in vitro experiments were conducted to investigate the role of Rasal2 in exosome-mediated breast cancer progression. Western blot analysis was performed to detect Rasal2 and p-Rasal2 (phosphorylated Rasal2) expression in ER+/ER- breast cancer cells and in exosomes, cancer tissues and blood of patients with ER+ or ER- breast cancer.

FINDINGS

Phosphorylation of Rasal2 at Serine 237 promoted tumour growth in both ER+ and ER- tumour cells and tissues. The functions of both p-Rasal2 and non-p-Rasal2 (non-phosphorylated-Rasal2) in the modulation of breast cancer progression are exosome-mediated. p-Rasal2 expression in ER+ breast cancer cells and exosomes, cancer tissues and blood was significantly lower than in ER- tumour cells and patients.

INTERPRETATION

p-Rasal2 facilitates tumour progression in both ER+ and ER- breast cancers. The ratio of p-Rasal2/non-p-Rasal2 in ER+ and ER- breast cancers is one of the factors deciding the role of Rasal2 (or total Rasal2) as a suppressor in ER+ breast cancers or as a promoter in ER- breast cancers. Targeting the phosphorylation of Rasal2 machinery may therefore be useful as a therapy to restrain breast cancer progression by reducing p-Rasal2/non-p-Rasal2 ratio, especially in ER- breast cancers. FUND: NSFC and Hong Kong Research Grants Council.

The Molecular Mechanism of Epithelial-Mesenchymal Transition for Breast Carcinogenesis

The transforming growth factor-β (TGF-β) signaling pathway plays multiple regulatory roles in the tumorigenesis and development of cancer. TGF-β can inhibit the growth and proliferation of epithelial cells and induce apoptosis, thereby playing a role in inhibiting breast cancer. Therefore, the loss of response in epithelial cells that leads to the inhibition of cell proliferation due to TGF-β is a landmark event in tumorigenesis. As tumors progress, TGF-β can promote tumor cell invasion, metastasis, and drug resistance. At present, the above-mentioned role of TGF-β is related to the interaction of multiple signaling pathways in the cell, which can attenuate or abolish the inhibition of proliferation and apoptosis-promoting effects of TGF-β and enhance its promotion of tumor progression. This article focuses on the molecular mechanisms through which TGF-β interacts with multiple intracellular signaling pathways in tumor progression and the effects of these interactions on tumorigenesis.

Emerging role of exosomes as promising diagnostic tool for cancer

The incidence of cancer is experiencing a steep rise in recent times. A survey report produced by GLOBOCAN 2018 estimates about 18.1 million new cases of cancer across 20 regions of the world. The bewildering number of people afflicted with cancer demands rapid diagnosis and treatment strategy. The current methods used for diagnosis of cancer are expensive, invasive, and time consuming. Hence, a new diagnostic panel has to be laid down to make the process less invasive, cost-effective, and rapid. A venture into identifying potential diagnostic targets introduced exosomes to the scientific community. A plethora of roles being packed into these biological cargoes makes them attractive targets for both therapeutic and diagnostic applications. Exosomes are membrane-bound extracellular vesicles packed with DNA, RNA, and proteins. Their presence in a wide array of body fluids such as breast milk, blood plasma, saliva, urine, serum, and cerebrospinal fluid makes them an excellent source of potential biomarkers. These nano-scale structures are capable of crossing hypoxic regions, systemic circulation and the territories of blood vessel barriers. In line with the above facts, the present review focuses on the therapeutic and diagnostic applications of exosomes in cancer.

Role of the Exosome in Ovarian Cancer Progression and Its Potential as a Therapeutic Target

Peritoneal dissemination is a distinct form of metastasis in ovarian cancer that precedes hematogenic or lymphatic metastasis. Exosomes are extracellular vesicles of 30–150 nm in diameter secreted by different cell types and internalized by target cells. There is emerging evidence that exosomes facilitate the peritoneal dissemination of ovarian cancer by mediating intercellular communication between cancer cells and the tumor microenvironment through the transfer of nucleic acids, proteins, and lipids. Furthermore, therapeutic applications of exosomes as drug cargo delivery are attracting research interest because exosomes are stabilized in circulation. This review highlights the functions of exosomes in each process of the peritoneal dissemination of ovarian cancer and discusses their potential for cancer therapeutics.

MiR-145 inhibits EGF-induced epithelial-to-mesenchymal transition via targeting Smad2 in human glioblastoma

Background/Aims: MiR-145 and Smad2 have been widely reported in the development and progression of human malignancies. In the present study, we investigated the correlation between miR-145 and Smad2 in human glioblastoma multiforme (GBM).

Methods: The epithelial–mesenchymal transition (EMT) biomarkers and Smad2 were assessed by Western blot. The silencing of Smad2 was conducted by transfection of Smad2 siRNAs. The cell migration and invasion were evaluated using Transwell assays, respectively. The dual luciferase reporter assay was performed to identify whether Smad2 is a direct target of miR-145.

Results: The epidermal growth factor (EGF) activated the phosphorylation of Smad2 in U87 and U251 cells in a time- and dose-dependent manner. However, treatment with silencing of Smad2 or overexpression of miR-145 significantly inhibited the expressions of total Smad2, N-cadherin, Vimentin and matrix metallopeptidase 9, but induced the expression of E-cadherin. In addition, silencing of Smad2 or overexpression of miR-145 also inhibited the migration and invasion of U87 and U251 cells. Mechanistically, Smad2 was confirmed to be a target gene of miR-145 by bioinformatics analysis and luciferase reporter assay. Restored Smad2 expression also reversed miR-145-induced inhibition of EMT in U87 and U251 cells.

Conclusion: MiR-145 inhibits EGF-induced EMT via targeting Smad2 in human GBM. Therefore, miR-145 may be a promising biomarker and therapeutic target for GBM patients.

Targeting Tumor Microenvironment for Cancer Therapy

Cancer development is highly associated to the physiological state of the tumor microenvironment (TME). Despite the existing heterogeneity of tumors from the same or from different anatomical locations, common features can be found in the TME maturation of epithelial-derived tumors. Genetic alterations in tumor cells result in hyperplasia, uncontrolled growth, resistance to apoptosis, and metabolic shift towards anaerobic glycolysis (Warburg effect). These events create hypoxia, oxidative stress and acidosis within the TME triggering an adjustment of the extracellular matrix (ECM), a response from neighbor stromal cells (e.g., fibroblasts) and immune cells (lymphocytes and macrophages), inducing angiogenesis and, ultimately, resulting in metastasis. Exosomes secreted by TME cells are central players in all these events. The TME profile is preponderant on prognosis and impacts efficacy of anti-cancer therapies. Hence, a big effort has been made to develop new therapeutic strategies towards a more efficient targeting of TME. These efforts focus on: (i) therapeutic strategies targeting TME components, extending from conventional therapeutics, to combined therapies and nanomedicines; and (ii) the development of models that accurately resemble the TME for bench investigations, including tumor-tissue explants, “tumor on a chip” or multicellular tumor-spheroids.