Exosomes Derived From Natural Killer Cells Exert Therapeutic Effect in Melanoma

A Snapshot of The Tumor Microenvironment in Colorectal Cancer: The Liquid Biopsy

The molecular profile of liquid biopsies is emerging as an alternative to tissue biopsies in the clinical management of malignant diseases. In colorectal cancer, significant liquid biopsy-based biomarkers have demonstrated an ability to discriminate between asymptomatic cancer patients and healthy controls. Furthermore, this non-invasive approach appears to provide relevant information regarding the stratification of tumors with different prognoses and the monitoring of treatment responses. This review focuses on the tumor microenvironment components which are detected in blood samples of colorectal cancer patients and might represent potential biomarkers. Exosomes released by tumor and stromal cells play a major role in the modulation of cancer progression in the primary tumor microenvironment and in the formation of an inflammatory pre-metastatic niche. Stromal cells-derived exosomes are involved in driving mechanisms that promote tumor growth, migration, metastasis, and drug resistance, therefore representing substantial signaling mediators in the tumor-stroma interaction. Besides, recent findings of specifically packaged exosome cargo in Cancer-Associated Fibroblasts of colorectal cancer patients identify novel exosomal biomarkers with potential clinical applicability. Furthermore, additional different signals emitted from the tumor microenvironment and also detectable in the blood, such as soluble factors and non-tumoral circulating cells, arise as novel promising biomarkers for cancer diagnosis, prognosis, and treatment response prediction. The therapeutic potential of these factors is still limited, and studies are in their infancy. However, innovative strategies aiming at the inhibition of tumor progression by systemic exosome depletion, exosome-mediated circulating tumor cell capturing, and exosome-drug delivery systems are currently being studied and may provide considerable advantages in the near future.

Small extracellular vesicle loading systems in cancer therapy: Current status and the way forward

Systemic chemotherapy is a conventional and important strategy for inhibition of cancer progression, but it is usually accompanied by various adverse effects. Targeting drug delivery systems, effective tools to avoid the adverse effects of chemotherapy, have been intensively studied and developed. Recently, the emerging application of exosomes and exosome-mimics (small extracellular vesicles [sEVs]) in targeted drug delivery and therapeutics has been widely appreciated. The sEVs-based delivery system comprises three basic components: vesicles, cargoes and surface decorations. In this article, we review the current status, existing challenges and future directions in this field from the following aspects: selection and production of vesicles; cargoes and methods to load them into vesicles; modifications to the surfaces of vesicles; as well as ways to prolong the half-life of sEVs in the circulation. Existing and emerging data indicate that sEVs are promising nanocarriers for clinical use, but additional efforts are needed to translate research findings into therapeutic products.

Natural Killer Cell-Derived Vesicular miRNAs: A New Anticancer Approach?

Natural killer (NK) cells are cytotoxic lymphocytes targeting virus-infected cells and cancer cells. Specific pro- and antikilling signals modulate the overall ability of NK cells to kill cancer cells, however, several immune-escape mechanisms can be enacted by cancer cells to avoid NK-mediated killing. Recently, increasing evidence has shown that extracellular vesicles (EV) released by NK cells carry proteins and miRNAs able to exert an antitumoral effect, even within a highly immune-suppressive tumor microenvironment. These recent findings suggest a possible use of NK-derived EVs as anticancer agents and propel the development of new strategies to enrich EVs with the most effective anticancer cargo as a promising new anticancer approach.

The role of exosomal PD-L1 in tumor progression and immunotherapy

Programmed death ligand 1 (PD-L1), a type I transmembrane protein, binds to its receptor PD-1 to suppress the activation of T cells, thereby maintaining immunological homeostasis. In contrast, tumor cells highly express PD-L1, which binds to receptor PD-1 expressed on activated T cells, leading to immune escape. Anti-PD-1/PD-L1 immune checkpoint therapy blocks the binding of PD-1/PD-L1 to reinvigorate the exhausted T cells, thereby inhibiting tumor growth. Exosomes are biologically active lipid-bilayer nanovesicles secreted by various cell types that mediate intercellular signal communication. Numerous studies have shown that tumor cells are able to promote tumor epithelial-mesenchymal transition, angiogenesis, and immune escape by releasing exosomes. Recent studies imply that tumor-derived exosomes could carry PD-L1 in the same membrane topology as the cell surface, thereby resisting immune checkpoint therapy. In this review, we mainly discuss the role of exosomes in the regulation of tumor progression and the potential resistance mechanism to immunotherapy via exosomal PD-L1. In addition, we propose that exosomal PD-L1 may have the potential to be a target to overcome resistance to anti-PD-1/PD-L1 antibody therapy.

Cocktail Strategy Based on NK Cell-Derived Exosomes and Their Biomimetic Nanoparticles for Dual Tumor Therapy

Successful cancer therapy requires drugs being precisely delivered to tumors. Nanosized drugs have attracted considerable recent attention, but their toxicity and high immunogenicity are important obstacles hampering their clinical translation. Here we report a novel “cocktail therapy” strategy based on excess natural killer cell-derived exosomes (NKEXOs) in combination with their biomimetic core–shell nanoparticles (NNs) for tumor-targeted therapy. The NNs were self- assembled with a dendrimer core loading therapeutic miRNA and a hydrophilic NKEXOs shell. Their successful fabrication was confirmed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The resulting NN/NKEXO cocktail showed highly efficient targeting and therapeutic miRNA delivery to neuroblastoma cells in vivo, as demonstrated by two-photon excited scanning fluorescence imaging (TPEFI) and with an IVIS Spectrum in vivo imaging system (IVIS), leading to dual inhibition of tumor growth. With unique biocompatibility, we propose this NN/NKEXO cocktail as a new avenue for tumor therapy, with potential prospects for clinical applications.

Blood TfR+ exosomes separated by a pH-responsive method deliver chemotherapeutics for tumor therapy

Blood transferrin receptor-positive (TfR+) exosomes are a kind of optimized drug delivery vector compared with other kinds of exosomes due to their easy access and high bio-safety. Their application facilitates the translation from bench to bedside of exosome-based delivery vehicles.

Methods: In this study, a pH-responsive superparamagnetic nanoparticles cluster (denoted as SMNC)-based method was developed for the precise and mild separation of blood TfR+ exosomes. Briefly, multiple superparamagnetic nanoparticles (SPMNs) labeled with transferrins (Tfs) could precisely bind to blood TfR+ exosomes to form an exosome-based cluster due to the specific recognition of TfR by Tf. They could realize the precise magnetic separation of blood TfR+ exosomes. More importantly, the pH-responsive dissociation characteristic of Tf and TfR led to the mild collapse of clusters to obtain pure blood TfR+ exosomes.

Results: Blood TfR+ exosomes with high purity and in their original state were successfully obtained through the pH-responsive SMNC-based method. These can load Doxorubicin (DOX) with a loading capacity of ~10% and dramatically increase the tumor accumulation of DOX in tumor-bearing mice because of their innate passive-targeting ability. In addition, blood TfR+ exosomes changed the biodistribution of DOX leading to the reduction of side effects. Compared with free DOX, DOX-loaded blood TfR+ exosomes showed much better tumor inhibition effects on tumor-bearing mice.

Conclusion: Taking advantage of the pH-responsive binding and disaggregation characteristics of Tf and TfR, the SMNC-based method can precisely separate blood TfR+ exosomes with high purity and in their original state. The resulting blood TfR+ exosomes showed excellent bio-safety and enable the efficient delivery of chemotherapeutics to tumors, facilitating the clinical translation of exosome-based drug delivery systems.

Exosomes: Versatile Nano Mediators of Immune Regulation

One of many types of extracellular vesicles (EVs), exosomes are nanovesicle structures that are released by almost all living cells that can perform a wide range of critical biological functions. Exosomes play important roles in both normal and pathological conditions by regulating cell-cell communication in cancer, angiogenesis, cellular differentiation, osteogenesis, and inflammation. Exosomes are stable in vivo and they can regulate biological processes by transferring lipids, proteins, nucleic acids, and even entire signaling pathways through the circulation to cells at distal sites. Recent advances in the identification, production, and purification of exosomes have created opportunities to exploit these structures as novel drug delivery systems, modulators of cell signaling, mediators of antigen presentation, as well as biological targeting agents and diagnostic tools in cancer therapy. This review will examine the functions of immunocyte-derived exosomes and their roles in the immune response under physiological and pathological conditions. The use of immunocyte exosomes in immunotherapy and vaccine development is discussed.

Possible roles of exosomal miRNAs in the pathogenesis of oral lichen planus

The etiology and pathogenesis of oral lichen planus have not achieved a consensus yet. This study aimed to explore the possible roles of exosomal miRNAs in the pathogenesis of oral lichen planus. Bioactive components from exosomes regulate intercellular communications that may be closely related to the occurrence and development of diseases, including oral lichen planus. Further, exosomes are expected to be a biomarker for the diagnosis and treatment of oral lichen planus. In this study, new advanced views about the biological characteristics, clinical significance, and involvement of exosomes in oral lichen planus were reviewed.

Melanoma and autoimmunity: spontaneous regressions as a possible model for new therapeutic approaches

Until now, malignancy has been considered a cellular problem represented by the perturbed (uncontrolled) division of the cells associated with invasion and metastasis. Contrary to this classical approach, a new perspective suggests that cancerous disease is, in fact, a supracellular problem represented by inadequate evolution of complex supracellular processes (embryogenesis, development, regeneration, etc.). Such complex processes would be disconnected from the real needs of the body, inducing unnecessary or even dangerous events such as an exacerbated rate of the cell division, angiogenesis, immunosuppression (specific to embryogenesis and melanoma), invasion (mediated by trophoblastic/placental factors in melanoma), and migration (specific to neural crest cells, which generate melanocytes - the most common origin for melanoma). As a result, a correct and comprehensive interpretation of cancer (causes, evolution, therapy, and prevention) should be conducted from a supracellular perspective. After presenting the supracellular perspective, this article further investigates the favorable evolution of malignant melanoma in two distinct situations: in patients receiving no therapy and in patients treated with immune-checkpoint inhibitors. In patients receiving no therapy, spontaneous regressions of melanoma could be the result of several autoimmune reactions (inducing not only melanoma regression but also vitiligo, an autoimmune event frequently associated with melanoma). Patients treated with immune-checkpoint inhibitors develop similar autoimmune reactions, which are clearly correlated with better therapeutic results. The best example is vitiligo, which is considered a positive prognostic factor for patients receiving immune-checkpoint inhibitors. This finding indicates that immune-checkpoint inhibitors induce distinct types of autoimmune events, some corresponding to specific favorable autoimmune mechanisms (favoring tumor regression) and others to common unfavorable adverse reactions (which should be avoided or minimized). In conclusion, the spectrum of autoimmune reactions induced by immune-checkpoint inhibitors should be restricted in the near future to only these specific favorable autoimmune mechanisms. In this way, the unnecessary autoimmune reactions/autoaggressions could be avoided (a better quality of life), and treatment specificity and efficiency should increase (a higher response rate for melanoma therapy).

Exosomes derived from cardiac parasympathetic ganglionic neurons inhibit apoptosis in hyperglycemic cardiomyoblasts

Diabetic cardiomyopathy is known to involve two forms of cardiac cell death: apoptosis and necrosis. However, it remains unknown whether hyperglycemia-induced apoptosis in the H9c2 cell culture system is inhibited by parasympathetic ganglionic neurons (PGN) derived exosomes (exos). We isolated PGN and sympathetic ganglionic neurons (SGN) from the right stellate ganglion in rats, and derived exos from these sources. H9c2 cells were divided into 4 groups: (1) Control, (2) H9c2 + Glucose (100 mmol/L), (3) H9c2 + Glucose + PGN-exos, and (4) H9c2 + Glucose + SGN-exos. We determined cell proliferation and viability with an MTT assay kit, and assessed apoptotic cell death with TUNEL staining and ELISA. Data were further confirmed by analyzing the presence of pro-apoptotic proteins Caspase-3 and Bax, and anti-apoptotic protein Bcl-2. Glucose exposed H9c2 cells significantly reduced cell viability, which was improved by PGN-exos, but not by SGN-exos. Furthermore, increased apoptosis in hyperglycemia in H9c2 cells was confirmed with TUNEL staining and cell death ELISA which demonstrated significantly (p < 0.05) reduction with PGN-exos treatment, but not with SGN-exos. Moreover, high expression of pro-apoptotic proteins Caspase-3 and Bax was reduced following treatment with PGN-exos; however, SGN-exos were unable to reduce the expression. Significantly reduced anti-apoptotic protein Bcl-2 following glucose treatment was improved with PGN-exos. Therefore, our data suggest that hyperglycemia induces apoptosis in H9c2 cells and decreases cell viability, and that PGN-exos are able to inhibit apoptosis, improve cell viability, and restore levels of anti-apoptotic protein Bcl-2.

Functions of Exosomes in the Triangular Relationship between the Tumor, Inflammation, and Immunity in the Tumor Microenvironment

Exosomes are extracellular vesicles that contain diverse components such as genetic materials, proteins, and lipids. Owing to their distinct derivation and tissue specificity, exosomes act as double-edged swords during the development of neoplasms. On the one hand, tumor-derived exosomes can modulate the immune system during tumorigenesis by regulating inflammatory cell infiltration and oxidative stress and by promoting epithelial-to-mesenchymal transition and immune-induced tumor dormancy. On the other hand, components of specific immune cell-derived exosomes may contribute to the efficacy of antitumor immunotherapy. In this review, we demonstrate the pivotal role of exosomes in the triangular relationship in the tumor microenvironment between the tumor, inflammation, and immunity, which may provide potential strategies for tumor immunotherapy at genetic and cellular levels.

Exosomes and their role in tumorigenesis and anticancer drug resistance

Exosomes are a class of extracellular vesicles ranging in size from 40 to 100 nm, which are secreted by both cancer cells and multiple stromal cells in the tumor microenvironment. Following their secretion, exosomes partake in endocrine, paracrine and autocrine signaling. Internalization of exosomes by tumor cells influences several cellular pathways which alter cancer cell physiology. Tumor-derived exosomes secreted by cancer or stromal cells can also confer anticancer drug-resistant traits upon cancer cells. These exosomes promote chemoresistance by transferring their cargo which includes nucleic acids, proteins, and metabolites to cancer cells or act as a decoy for immunotherapeutic targets. Depletion of exosomes can reverse some of the detrimental effects on tumor metabolism and restore drug sensitivity to chemotherapeutic treatment. Herein we discuss various approaches that have been developed to deplete exosomes for therapeutic purposes. The natural composition, low immunogenicity and cytotoxicity of exosomes, along with their ability to specifically target tumor cells, render them an appealing platform for drug delivery. The ability of exosomes to mediate autocrine and paracrine signaling in target cells, along with their natural structure and low immunogenicity render them an attractive vehicle for the delivery of anticancer drugs to tumors.

Ku80 promotes melanoma growth and regulates antitumor effect of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway

Melanoma is one of the most malignant and aggressive cancers with high cancer-related deaths. However, it is unclear whether Ku80 regulates tumor growth in human melanoma. In this study, we screened a siRNA library targeting 6024 human genes and identified Ku80 as a potential therapeutic target in melanoma cells. Knockdown of Ku80 significantly suppressed melanoma cell proliferation and induced apoptosis, as well as enhanced the antitumor effect of melatonin in melanoma in vitro and in vivo. Overexpression of Ku80, however, promoted melanoma growth and increased the insensitivity of melanoma cells to melatonin. Mechanistically, we found that Ku80 bound to the PDK1 promoter and activated the transcription of PDK1. Moreover, we showed that the binding of Ku80 at the PDK-1 promoter was HIF1-α dependent, and melatonin degraded HIF1-α in melanoma cells. Furthermore, clinical data revealed that the expression of Ku80 and PDK-1 proteins were positively correlated and elevated in the tumor tissues of melanoma patients, and high expression of Ku80 predicted a poor prognosis in melanoma. Collectively, our study demonstrated that Ku80 promoted melanoma growth and regulated antitumor activity of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway, suggesting that Ku80 may be a potential molecular target for melanoma treatment.

Cancer Immunotherapy Based on Natural Killer Cells: Current Progress and New Opportunities

Cancer immunotherapy has been firmly established as a new milestone for cancer therapy, with the development of multiple immune cells as therapeutic tools. Natural killer (NK) cells are innate immune cells endowed with potent cytolytic activity against tumors, and meanwhile act as regulatory cells for the immune system. The efficacy of NK cell-mediated immunotherapy can be enhanced by immune stimulants such as cytokines and antibodies, and adoptive transfer of activated NK cells expanded ex vivo. In addition, NK cells can arm themselves with chimeric antigen receptors (CARs), which may greatly enhance their anti-tumor activity. Most recently, extracellular vesicles (EVs) derived from NK cells show promising anti-tumor effects in preclinical studies. Herein, we carefully review the current progress in these NK cell-based immunotherapeutic strategies (NK cells combined with stimulants, adoptive transfer of NK cells, CAR-NK cells, and NK EVs) for the treatment of cancers, and discussed the challenges and opportunities for opening a new horizon for cancer immunotherapy.

The Role of Extracellular Vesicles as Modulators of the Tumor Microenvironment, Metastasis and Drug Resistance in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide, with high morbidity and mortality rates. A number of factors including modulation of the tumor microenvironment, high metastatic capability, and resistance to treatment have been associated with CRC disease progression. Recent studies have documented that tumor-derived extracellular vesicles (EVs) play a significant role in intercellular communication in CRC via transfer of cargo lipids, proteins, DNA and RNAs to the recipient tumor cells. This transfer influences a number of immune-related pathways leading to activation/differentiation/expression of immune cells and modulation of the tumor microenvironment that plays a significant role in CRC progression, metastasis, and drug resistance. Furthermore, tumor-derived EVs are secreted in large amounts in biological fluids of CRC patients and as such the expression analysis of EV cargoes have been associated with prognosis or response to therapy and may be a source of therapeutic targets. This review aims to provide a comprehensive insight into the role of EVs in the modulation of the tumor microenvironment and its effects on CRC progression, metastasis, and drug resistance. On the other hand, the potential role of CRC derived EVs as a source of biomarkers of response and therapeutic targets will be discussed in detail to understand the dynamic role of EVs in CRC diagnosis, treatment, and management.

Malignant Melanoma: Autoimmunity and Supracellular Messaging as New Therapeutic Approaches

OPINION STATEMENT

Melanoma is one of the most aggressive forms of cancer, with a high mortality rate in the absence of a safe and curable therapy. As a consequence, several procedures have been tested over time, with the most recent (immunological and targeted) therapies proving to be effective in some patients. Unfortunately, these new treatment options continue to generate debate related to the therapeutic strategy (intended to maximize the long-term results of patients with melanoma), not only about the monotherapy configuration but also regarding association/succession between distinct therapeutic procedures. As an example, targeted therapy with BRAF inhibitors proved to be effective in advanced BRAF-mutant melanoma. However, such treatments with BRAF inhibitors lead to therapy resistance in half of patients after approximately 6 months. Even if most benign nevi incorporate oncogenic BRAF mutations, they rarely become melanoma; therefore, targeted therapy with BRAF inhibitors should be viewed as an incomplete or perfectible therapy. Another example is related to the administration of immune checkpoint inhibitors/ICIs (anti-CTLA-4 antibodies, anti-PD-1/PD-L1 antibodies), which are successfully used in metastatic melanoma. It is currently believed that CTLA-4 and PD-1 blockade would favor a strong immune response against cancer cells. The main side effects of ICIs are represented by the development of immune-related adverse events, which in some cases can be lethal. These ICI side effects would thus be not only therapeutically counterproductive but also potentially dangerous. Surprisingly, a subset of immune-related adverse events (especially autoimmune toxicity) seems to be clearly correlated with better therapeutic results, perhaps due to an additional therapeutic effect (currently insufficiently studied/exploited). Contrary to the classical approach of cancer (considered until now an uncontrolled division of cells), a very recent and comprehensive theory describes malignancy as a supracellular disease. Cancerous disease would therefore be a disturbed supracellular process (embryogenesis, growth, development, regeneration, etc.), which imposes/coordinates an increased rhythm of cell division, angiogenesis, immunosuppression, etc. Melanoma is presented from such a supracellular perspective to be able to explain the beneficial role of autoimmunity in cancer (autoimmune abortion/rejection of the melanoma-embryo phenotype) and to create premises to better optimize the newly emerging therapeutic options. Finally, it is suggested that the supracellular evolution of malignancy implies complex supracellular messaging (between the cells and host organism), which would be interfaced especially by the extracellular matrix and noncoding RNA. Therefore, understanding and manipulating supracellular messaging in cancer could open new treatment perspectives in the form of digitized (supracellular) therapy.

Exosome-orchestrated hypoxic tumor microenvironment

Hypoxic tumor microenvironment is a common feature of solid tumors and is associated with aggressiveness and poor patient outcomes. A continuous interference between cancer cells and stromal cells within the hypoxic microenvironment has been uncovered for its importance in cancer development and treatment responsiveness. Exosomes, initially considered as “garbage bins” for unwanted material from cells, are now elucidated to perform a variety of functions that involve interactions within the cellular microenvironment due to their ability to carry numerous cargoes, including lipids, proteins, nucleic acids, and metabolites. Exosome-mediated continuous interference between cancer cells and stroma are believed to regulate hypoxia-adaptation and to rebuild the microenvironment in return. In this review, we will discuss the knowledge in literature with respect to the exosome-mediated multi-directional and mutual signal transmission among the variety of cell types within hypoxic cancer microenvironment.

Extracellular vesicles in the tumor microenvironment: old stories, but new tales

Mammalian cells synthesize and release heterogeneous extracellular vesicles (EVs) which can be generally recognized as subclasses including exosomes, microvesicles (MVs), and apoptotic bodies (ABs), each differing in their biogenesis, composition and biological functions from others. EVs can originate from normal or cancer cells, transfer bioactive cargoes to both adjacent and distant sites, and orchestrate multiple key pathophysiological events such as carcinogenesis and malignant progression. Emerging as key messengers that mediate intercellular communications, EVs are being paid substantial attention in various disciplines including but not limited to cancer biology and immunology. Increasing lines of research advances have revealed the critical role of EVs in the establishment and maintenance of the tumor microenvironment (TME), including sustaining cell proliferation, evading growth suppression, resisting cell death, acquiring genomic instability and reprogramming stromal cell lineages, together contributing to the generation of a functionally remodeled TME. In this article, we present updates on major topics that document how EVs are implicated in proliferative expansion of cancer cells, promotion of drug resistance, reprogramming of metabolic activity, enhancement of metastatic potential, induction of angiogenesis, and escape from immune surveillance. Appropriate and insightful understanding of EVs and their contribution to cancer progression can lead to new avenues in the prevention, diagnosis and treatment of human malignancies in future medicine.

Exosomes: The Indispensable Messenger in Tumor Pathogenesis and the Rising Star in Antitumor Applications

As natural secreted nanovesicles through the endolysosomal pathway, exosomes have attracted increasing attention over the past decades. An overwhelming number of studies have provided evidence for the intriguing roles that exosomes play in intercellular communication. They are widely involved in the transmission of biomolecule cargos between original cells and neighboring/distant cells in normal physiological processes. In addition, it has also been demonstrated that exosomes play vital roles in multiple biological pathways in the development of numerous diseases including cancer. Moreover, both natural and modified exosomes showed promising potential in serving as a versatile nanoplatform for cancer diagnosis and cancer therapy. This review aims to present a comprehensive and critical overview on the recent advances in exosome nanoscience and nanotechnology, ranging from their biogenesis, secretion, isolation, and biological function in tumor pathogenesis to their extensive antitumor applications.

Extracellular vesicles derived from natural killer cells use multiple cytotoxic proteins and killing mechanisms to target cancer cells

Extracellular vesicles (EVs) are secreted membrane vesicles, which play complex physiological and pathological functions in intercellular communication. Recently, we isolated natural killer (NK) cell-derived EVs (NK-EVs) from ex vivo expansion of NK cell cultures. The isolated NK-EVs contained cytotoxic proteins and several activated caspases, and they induced apoptosis in target cells. In this report, the protein levels of cytotoxic proteins from NK-EV isolates were analysed by ELISA. The mean values of perforin (PFN, 550 ng/mL), granzyme A (GzmA, 185 ng/mL), granzyme B (GzmB, 23.4 ng/mL), granulysin (GNLY, 56 ng/mL), and FasL (2.5 ng/mL) were obtained from >60 isolations using dot plots. The correlation between cytotoxicity and cytotoxic protein levels was examined by linear regression. PFN, GzmA, GzmB, GNLY all had a positive, moderate correlation with cytotoxicity, suggesting that there is not a single cytotoxic protein dominantly involved in killing and that all of these proteins may contribute to cytotoxicity. To further explore the possible killing mechanisms, cells were treated with NK-EVs, proteins extracted and lysates assessed by Western blotting. The levels of Gzm A substrates, SET and HMG2, were diminished in targeted cells, indicating that GzmA may induce a caspase-independent death pathway. Also, cytochrome C was released from mitochondria, a central hallmark of caspase-dependent death pathways. In addition, several ER-associated proteins were altered, suggesting that NK-EVs may induce ER stress resulting in cell death. Our results indicate that multiple killing mechanisms are activated by NK-derived EVs, including caspase-independent and -dependent cell death pathways, which can mediate cytotoxicity against cancer cells. Abbreviations: NK: natural killer cells; aNK: activated NK cells; EV: extracellular vesicles; ER: endoplasmic reticulum; ALL: acute lymphoblastic leukaemia; FBS: foetal bovine serum. GzmA: granzyme A; GzmB: granzyme B; GNLY: granulysin; PFN: perforin.

Enhancement of antitumor potency of extracellular vesicles derived from natural killer cells by IL-15 priming

PURPOSE

Natural killer (NK) cells are the key subset of innate-immunity lymphocytes; they possess antitumor activities and are used for cancer immunotherapy. In a previous study, extracellular vehicles (EVs) from NK-92MI cells were isolated and exploited for their ability to kill human cancer cells in vitro and in vivo (multiple injection methods). Here, the potential of NK-cell-derived EVs (NK-EVs) for immunotherapy was improved by priming with interleukin (IL)-15.

METHODS

NK-EVs were isolated from the culture medium without or with IL-15 (NK-EVsIL-15) by ultracentrifugation and were purified via density gradient ultracentrifugation. In addition, NK-EVs and NK-EVsIL-15 were characterized by transmission electron microscopy, nanoparticle-tracking analysis, and western blotting. Flow cytometry, bioluminescence imaging, and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed for apoptosis, protein expression, cell proliferation, and cytotoxicity analyses. Furthermore, xenograft tumor-bearing mice were injected with PBS, NK-EVs, or NK-EVsIL-15 intravenously five times. Tumor growth was monitored using calipers and bioluminescence imaging. Toxicity of the nanoparticles was evaluated by measuring the body weight of the mice.

RESULTS

NK-EVsIL-15 showed significantly higher cytolytic activity toward human cancer cell lines (glioblastoma, breast cancer, and thyroid cancer) and simultaneously increased the expression of molecules associated with NK-cell cytotoxicity. When compared with NK-EVs, NK-EVsIL-15 significantly inhibited the growth of glioblastoma xenograft cells in mice. In addition, both NK-EVs and NK-EVsIL-15 were not significantly toxic to either normal cells or mice.

CONCLUSION

IL-15 may improve the immunotherapeutic effects of NK-EVs, thus improving the applications of NK-EVs in the future.

Exosome Biochemistry and Advanced Nanotechnology for Next-Generation Theranostic Platforms

Recent marked technological advances in the field of exosome nanotechnology have provided unprecedented opportunities to bloom the developments of exosome-related biology, chemistry, pathology, and therapeutics, which have laid a solid basis for scientific community to design exosome-based nanotheranostic platforms. The unique structural/compositional/morphological characteristics of exosomes as natural nanocarriers, as well as their fascinating physicochemical/biochemical properties, which underpin their special physiopathological roles, have triggered the concept that these cell-derived nanovesicles with intrinsic biological functions can be highly competent for the establishment of next-generation nanomedicine. Herein, efforts are made to give a comprehensive overview on the recent advances of exosome nanotechnology based on the representative examples of the current state of the art of exosome-based research, ranging from their formation, biological function, preparation, and characterization to their extensive nanomedical applications. It is highly expected that the better and clearer elucidation of the fundamental principles for advanced nanotechnology in constructing exosome-based theranostic nanoplatforms, as well as integrating the intrinsic advantages of exosomes as endogenous cell-derived nanocarriers with the advanced design methodology of traditional nanomedicine, will help to unlock the innate powers of exosomes for the establishment of next-generation theranostic nanoplatforms.

The role of exosomal long non-coding RNAs in cancer drug resistance

One of the major challenges in oncology is drug resistance, which triggers relapse and shortens patients’ survival. In order to promote drug desensitization, cancer cells require the establishment of an ideal tumor microenvironment that accomplishes specific conditions. To achieve this objective, cellular communication is a key factor. Classically, cells were believed to restrictively communicate by ligand-receptor binding, physical cell-to-cell interactions and synapses. Nevertheless, the crosstalk between tumor cells and stroma cells has also been recently reported to be mediated through exosomes, the smallest extracellular vesicles, which transport a plethora of functionally active molecules, such as: proteins, lipids, messenger RNA, DNA, microRNA or long non-coding RNA (lncRNAs). LncRNAs are RNA molecules greater than 200 base pairs that are deregulated in cancer and other diseases. Exosomal lncRNAs are highly stable and can be found in several body fluids, being considered potential biomarkers for tumor liquid biopsy. Exosomal lncRNAs promote angiogenesis, cell proliferation and drug resistance. The role of exosomal lncRNAs in drug resistance affects the main treatment strategies in oncology: chemotherapy, targeted therapy, hormone therapy and immunotherapy. Overall, knowing the molecular mechanisms by which exosomal lncRNA induce pharmacologic resistance could improve further drug development and identify drug resistance biomarkers.

NK Cell-Based Glioblastoma Immunotherapy

Glioblastoma (GB) is the most aggressive and most common malignant primary brain tumor diagnosed in adults. GB shows a poor prognosis and, unfortunately, current therapies are unable to improve its clinical outcome, imposing the need for innovative therapeutic approaches. The main reason for the poor prognosis is the great cell heterogeneity of the tumor mass and its high capacity for invading healthy tissues. Moreover, the glioblastoma microenvironment is capable of suppressing the action of the immune system through several mechanisms such as recruitment of cell modulators. Development of new therapies that avoid this immune evasion could improve the response to the current treatments for this pathology. Natural Killer (NK) cells are cellular components of the immune system more difficult to deceive by tumor cells and with greater cytotoxic activity. Their use in immunotherapy gains strength because they are a less toxic alternative to existing therapy, but the current research focuses on mimicking the NK attack strategy. Here, we summarize the most recent studies regarding molecular mechanisms involved in the GB and immune cells interaction and highlight the relevance of NK cells in the new therapeutic challenges.

Natural Killer-Derived Exosomal miR-186 Inhibits Neuroblastoma Growth and Immune Escape Mechanisms

In neuroblastoma, the interplay between immune cells of the tumor microenvironment and cancer cells contributes to immune escape mechanisms and drug resistance. In this study, we show that natural killer (NK) cell-derived exosomes carrying the tumor suppressor microRNA (miR)-186 exhibit cytotoxicity against MYCN-amplified neuroblastoma cell lines. The cytotoxic potential of these exosomes was partly dependent upon expression of miR-186. miR-186 was downregulated in high-risk neuroblastoma patients, and its low expression represented a poor prognostic factor that directly correlated with NK activation markers (i.e., NKG2D and DNAM-1). Expression of MYCN, AURKA, TGFBR1, and TGFBR2 was directly inhibited by miR-186. Targeted delivery of miR-186 to MYCN-amplified neuroblastoma or NK cells resulted in inhibition of neuroblastoma tumorigenic potential and prevented the TGFβ1-dependent inhibition of NK cells. Altogether, these data support the investigation of a miR-186-containing nanoparticle formulation to prevent tumor growth and TGFβ1-dependent immune escape in high-risk neuroblastoma patients as well as the inclusion of ex vivo-derived NK exosomes as a potential therapeutic option alongside NK cell-based immunotherapy.Significance: These findings highlight the therapeutic potential of NK cell-derived exosomes containing the tumor suppressor miR-186 that inhibits growth, spreading, and TGFβ-dependent immune escape mechanisms in neuroblastoma.

γδTDEs: An Efficient Delivery System for miR-138 with Anti-tumoral and Immunostimulatory Roles on Oral Squamous Cell Carcinoma

In this study, we sought to investigate the potential application of γδ T cell-derived extracellular vesicles (γδTDEs) as drug delivery system (DDS) for miR-138 in the treatment of oral squamous cell carcinoma (OSCC). Our data showed that overexpression of miR-138 in γδ T cells obtained miR-138-rich γδTDEs accompanying increased expansion and cytotoxicity of γδ T cells. γδTDEs inherited the cytotoxic profile of γδ T cells and could efficiently deliver miR-138 to OSCC cells, resulting in synergetic inhibition on OSCC both in vitro and in vivo. The pre-immunization by miR-138-rich γδTDEs inhibited the growth of OSCC tumors in immunocompetent C3H mice, but not in nude mice, suggesting an immunomodulatory role by miR-13-rich γδTDEs. γδTDEs and miR-138 additively increased the proliferation, interferon-γ (IFN-γ) production, and cytotoxicity of CD8⁺ T cells against OSCC cells. Only delivered by γδTDEs can miR-138 efficiently target programmed cell death 1 (PD-1) and CTLA-4 in CD8⁺ T cells. We conclude that γδTDEs delivering miR-138 could achieve synergetic therapeutic effects on OSCC, which is benefited from the individual direct anti-tumoral effects on OSCC and immunostimulatory effects on T cells by both γδTDEs and miR-138; γδTDEs could serve as an efficient DDS for microRNAs (miRNAs) in the treatment of cancer.

Harmonization of exosome isolation from culture supernatants for optimized proteomics analysis

Exosomes, the smallest subset of extracellular vesicles (EVs), have recently attracted much attention in the scientific community. Their involvement in intercellular communication and molecular reprogramming of different cell types created a demand for a stringent characterization of the proteome which exosomes carry and deliver to recipient cells. Mass spectrometry (MS) has been extensively used for exosome protein profiling. Unfortunately, no standards have been established for exosome isolation and their preparation for MS, leading to accumulation of artefactual data. These include the presence of high-abundance exosome-contaminating serum proteins in culture media which mask low-abundance exosome-specific components, isolation methods that fail to yield “pure” vesicles or variability in protein solubilization protocols. There is an unmet need for the development of standards for exosome generation, harvesting, and isolation from cellular supernatants and for optimization of protein extraction methods before proteomics analysis by MS. In this communication, we illustrate the existing problems in this field and provide a set of recommendations that are expected to harmonize exosome processing for MS and provide the faithful picture of the proteomes carried by exosomes. The recommended workflow for effective and specific identification of proteins in exosomes released by the low number of cells involves culturing cells in medium with a reduced concentration of exosome-depleted serum, purification of exosomes by size-exclusion chromatography, a combination of different protein extraction method and removal of serum-derived proteins from the final dataset using an appropriate sample of cell-unexposed medium as a control. Application of this method allowed detection of >250 vesicle-specific proteins in exosomes from 10 mL of culture medium.

New Optical Imaging Reporter-labeled Anaplastic Thyroid Cancer-Derived Extracellular Vesicles as a Platform for In Vivo Tumor Targeting in a Mouse Model

Extracellular vesicles (EVs), originating from multivesicular bodies by invagination of the endosomal membrane, are communication channels between distant cells. They are natural carriers of exogeneous cellular materials and have been exploited as drug delivery carriers in various diseases. Here, we found that tumor cell-derived EVs can be used as efficient targets in tumors by monitoring with an optical reporter system. Anaplastic thyroid cancer (CAL62) cell-derived EVs with Renilla luciferase (Rluc) were used to target CAL62 tumors in a mouse model. Optical imaging revealed that cancer cell-derived EVs (EV-CAL62/Rluc) targeted the original tumor (CAL62) in mice within 30 min after systemic injection. Furthermore, fluorescence imaging revealed that EV-CAL62/Rluc were internalized into CAL62 tumors in the mice. Ex vivo Optical imaging further confirmed the in vivo finding. Here, we successfully monitored the tumor targeting ability of tumor cell-derived EVs by optical imaging. Based on these results, tumor cell-derived EVs are highly effective natural carriers for drug delivery for cancer therapies.

Mass-Spectrometric Analysis of Proteome of Microvesicles Produced by NK-92 Natural Killer Cells

Membrane extracellular microvesicles serve as carriers of a wide range of molecules, the most important among these are proteins, lipids, and nucleic acids. Cytotoxic proteins of natural killer cells play a key role in the realization of their cytolytic functions. An important stage in understanding of the distant communication of cells and mechanisms of its regulation is analysis of the proteome composition of microvesicles. We studied the proteomic composition of microvesicles produced by NK-92 natural killer cells. Granzyme A, a specific protein of cytotoxic cells, has been identified in the microvesicles by QTOF-mass spectrometry. It was shown that heat shock proteins, components of the ubiquitin-proteasome system, enzymes of protein biosynthesis and energy metabolism, nuclear and serum proteins, as well as cytoskeleton proteins are associated with the microvesicles.

Novel alternatives to extracellular vesicle-based immunotherapy - exosome mimetics derived from natural killer cells

Exosomes are endogenous nanocarriers that can deliver biological information between cells. They are secreted by all cell types, including immune cells such as natural killer (NK) cells. However, mammalian cells release low quantities of exosomes, and the purification of exosomes is difficult. Here, nanovesicles were developed by extrusion of NK cells through filters with progressively smaller pore sizes to obtain exosome mimetics (NK-EM). The anti-tumour effect of the NK-EM was confirmed in vitro and in vivo. The morphological features of the NK-EM were revealed by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and Western blot. In vitro, the cytotoxicity of the NK-EM to cancer cells (glioblastoma, breast carcinoma, anaplastic thyroid cancer and hepatic carcinoma) was assessed using bioluminescence imaging (BLI) and CCK-8 assay. For in vivo study, a xenograft glioblastoma mouse model was established. The anti-tumour activity of NK-EM was confirmed in vivo by the significant decreases of BLI, size and weight (all p < .001) of the tumour compared with the control group. Moreover, NK-EM cytotoxicity for glioblastoma cells that related with decreased levels of the cell survival markers p-ERK and p-AKT, and increased levels of apoptosis protein markers cleaved-caspase 3, cytochrome-c and cleaved-PARP was confirmed. All those results suggest that NK-EM exert stronger killing effects to cancer cells compared with the traditional NK-Exo, at the same time, the tumour targeting ability of the NK-EM was obtained in vivo. Therefore, NK-EM might be a promising immunotherapeutic agent for treatment of cancer.

Exosomes in cancer: Small transporters with big functions

Exosomes are nanosized membrane-bound vesicles containing abundant proteins, DNA, mRNA, and non-coding RNAs. Exosomes are now considered as an additional mechanism for intercellular communication, allowing cells to exchange proteins, lipids and genetic material. Increasing studies have shown that exosomes play an important role in tumour initiation, growth, progression, metastasis, drug resistance and immune escape. In this article, we review recent advances in the biology of exosomes. We elaborate the specific mechanism by which exosomes affect the communication between tumours and the microenvironment. Finally, we report that exosomes may provide promising biomarkers for cancer diagnosis and represent new targets for cancer therapy.

In vivo Non-invasive Imaging of Radio-Labeled Exosome-Mimetics Derived From Red Blood Cells in Mice

Exosomes are natural nano-sized membrane vesicles that have garnered recent interest owing to their potential as drug delivery vehicles. Though exosomes are effective drug carriers, their production and in vivo biodistribution are still not completely elucidated. We analyzed the production of exosome mimetics (EMs) from red blood cells (RBCs) and the radio-labeling of the RBC-EMs for in vivo imaging. Engineered EMs from RBCs were produced in large-scale by a one-step extrusion method, and further purified by density-gradient centrifugation. RBC-EMs were labeled with technetium-99m (99mTc). For non-invasive imaging, 99mTc (free) or 99mTc-RBC-EMs were injected in mice, and their biodistribution was analyzed by gamma camera imaging. Animals were sacrificed, and organs were collected for further biodistribution analysis. RBC-EMs have similar characteristics as the RBC exosomes but have a 130-fold higher production yield in terms of particle numbers. Radiochemical purity of 99mTc-RBC-EMs was almost 100% till 2 h reduced to 97% at 3 h. Radio-labeling did not affect the size and morphology of RBC-EMs. In contrast to free 99mTc, in vivo imaging of 99mTc-RBC-EMs in mice showed higher uptake in the liver and spleen, and no uptake in the thyroid. Ex vivo imaging confirmed the in vivo findings. Furthermore, fluorescent imaging confirmed the nuclear imaging findings. Immunofluorescent imaging revealed that the hepatic uptake of RBC-EMs was significantly mediated by kupffer cells (resident hepatic macrophages). Our results demonstrate a simple yet large-scale production method for a novel type of RBC-EMs, which can be effectively labeled with 99mTc, and feasibly monitored in vivo by nuclear imaging. The RBC-EMs may be used as in vivo drug delivery vehicles.

Development and MPI tracking of novel hypoxia-targeted theranostic exosomes

Treating the hypoxic region of the tumor remains a significant challenge. The goals of this study are to develop an exosome platform that can target regions of tumor hypoxia and that can be monitored in vivo using magnetic particle imaging (MPI). Four types of exosomes (generated under hypoxic or normoxic conditions, and with or without exposure to X-ray radiation) were isolated from MDA-MB-231 human breast cancer cells. Exosomes were labeled by DiO, a fluorescent lipophilic tracer, to quantify their uptake by hypoxic cancer cells. Subsequently, the exosomes were modified to carry SPIO (superparamagnetic iron oxide) nanoparticles and Olaparib (PARP inhibitor). FACS and fluorescence microscopy showed that hypoxic cells preferentially take up exosomes released by hypoxic cells, compared with other exosome formulations. In addition, the distribution of SPIO-labeled exosomes was successively imaged in vivo using MPI. Finally, the therapeutic efficacy of Olaparib-loaded exosomes was demonstrated by increased apoptosis and slower tumor growth in vivo. Our novel theranostic platform could be used as an effective strategy to monitor exosomes in vivo and deliver therapeutics to hypoxic tumors.

Circulating MicroRNA Biomarkers in Melanoma: Tools and Challenges in Personalised Medicine

Effective management of melanoma depends heavily on early diagnosis. When detected in early non-metastatic stages, melanoma is almost 100% curable by surgical resection, however when detected in late metastatic stages III and IV, 5-year survival rates drop to ~50% and 10–25%, respectively, due to limited efficacy of current treatment options. This presents a pressing need to identify biomarkers that can detect patients at high risk of recurrence and progression to metastatic disease, which will allow for early intervention and survival benefit. Accumulating evidence over the past few decades has highlighted the potential use of circulating molecular biomarkers for melanoma diagnosis and prognosis, including lactate dehydrogenase (LDH), S100 calcium-binding protein B (S100B) and circulating tumor DNA (ctDNA) fragments. Since 2010, circulating microRNAs (miRNAs) have been increasingly recognised as more robust non-invasive biomarkers for melanoma due to their structural stability under the harsh conditions of the blood and different conditions of sample processing and isolation. Several pre-analytical and analytical variables challenge the accurate quantification of relative miRNA levels between serum samples or plasma samples, leading to conflicting findings between studies on circulating miRNA biomarkers for melanoma. In this review, we provide a critical summary of the circulating miRNA biomarkers for melanoma published to date.

Targeting and Therapy of Glioblastoma in a Mouse Model Using Exosomes Derived From Natural Killer Cells

OBJECTIVE

Glioblastoma is a highly aggressive primary brain tumor that is resistant to radiotherapy and chemotherapy. Natural killer (NK) cells have been used to treat incurable cancers. Recent studies have investigated the effectiveness of NK-cell-derived exosomes (NK-Exo) for treating incurable cancers such as melanoma, leukemia, and neuroblastoma; however, NK-Exo have not been used to treat glioblastoma. In the present study, we investigated the antitumor effects of NK-Exo against aggressive glioblastoma both in vitro and in vivo and determined the tumor-targeting ability of NK-Exo by performing fluorescence imaging.

METHODS

U87/MG cells were transfected with the enhanced firefly luciferase (effluc) and thy1.1 genes; thy1.1-positive cells were selected using microbeads. U87/MG/F cells were assessed by reverse transcription polymerase chain reaction (RT-PCR), western blotting, and luciferase-activity assays. NK-Exo were isolated by ultracentrifugation, purified by density gradient centrifugation, and characterized by transmission electron microscopy, dynamic light scattering (DLS), nanoparticle-tracking analysis (NTA), and western blotting. Cytokine levels in NK-Exo were compared to those in NK cells and NK-cell medium by performing an enzyme-linked immunosorbent assay (ELISA). NK-Exo-induced apoptosis of cancer cells was confirmed by flow cytometry and western blotting. In vivo therapeutic effects and specificity of NK-Exo against glioblastoma were assessed in a xenograft mouse model by fluorescence imaging. Xenograft mice were treated with NK-Exo, which was administered seven times through the tail vein. Tumor growth was monitored by bioluminescence imaging (BLI), and tumor volume was measured by ultrasound imaging. The mice were intraperitoneally injected with dextran sulfate 2 h before NK-Exo injection to decrease the liver uptake and increase the tumor specificity of NK-Exo.

RESULTS

RT-PCR and western blotting confirmed the gene and protein expression of effluc in U87/MG/F cells, with the bioluminescence activity of U87/MG/F cells increasing with an increase in cell number. NTA and DLS results indicated that the size of NK-Exo was ~100 nm, and the western blot results confirmed that NK-Exo expressed exosome markers CD63 and Alix. We confirmed the in vitro cytotoxic effects of NK-Exo on U87/MG/F cells by performing BLI, and the killing effect on U87/MG and U87MG/F cells was measured by CCK-8 and MTT assays (p < 0.001). ELISA results indicated that NK-Exo contained tumor necrosis factor-α and granzyme B. In vivo NK-Exo treatment inhibited tumor growth compared to in control mice (p < 0.001), and pretreatment of xenograft mice with dextran sulfate 2 h before NK-Exo treatment increased the antitumor effect of NK-Exo (p < 0.01) compared to in control and NK-Exo-alone-treated mice.

CONCLUSION

NK-Exo targeted and exerted antitumor effects on glioblastoma cells both in vitro and in vivo, suggesting their utility in treating incurable glioblastoma.

Extracellular Vesicles: A New Perspective in Tumor Therapy

In recent years, the study of extracellular vesicles has been booming across various industries. Extracellular vesicles are considered one of the most important physiological endogenous carriers for the specific delivery of molecular information (nucleonic acid, cytokines, enzymes, etc.) between cells. It has been discovered that they perform a critical role in promoting tumor cell growth, proliferation, tumor cell invasion, and metastatic ability and regulating the tumor microenvironment to promote tumor cell communication and metastasis. In this review, we will discuss (1) the mechanism of extracellular vesicles generation, (2) their role in tumorigenesis and cancer progression (cell growth and proliferation, tumor microenvironment, epithelial-mesenchymal transition (EMT), invasion, and metastasis), (3) the role of extracellular vesicles in immune therapy, (4) extracellular vesicles targeting in tumor therapy, and (5) the role of extracellular vesicles as biomarkers. It is our hope that better knowledge and understanding of the extracellular vesicles will offer a wider range of effective therapeutic targets for experimental tumor research.

Exosomes in melanoma: a role in tumor progression, metastasis and impaired immune system activity

Exosomes (Exo) are small vesicles produced by melanoma cells and the accessory cells of the tumor microenvironment. They emerge via both classical and direct pathways and actively participate in tumor colonisation of distant tissues. The proteins, nucleic acids, cytokines and growth factors engulfed by Exo are transferred to recipient cells, where they drive numerous functions required for the tumor escape from immune system control and tumor progression. By positively or negatively modulating immune cell properties, Exo provoke immune suppression and, in turn, defective dendritic cell (DC) functions. Together, these effects limit the cytotoxicity of T-cells and expand both T-regulatory and myeloid-derived suppressor populations. They also hinder perforin and granzyme production by natural killer cells. Finally, Exo also control the organotropism of melanoma cells. The distinct phenotypic properties of Exo can be exploited both for diagnostic purposes and in the early identification of melanoma patients likely to respond to immunotherapy. The potential therapeutic application of Exo derived from DCs has been demonstrated in vaccination trials, which showed an increase in anti-melanoma activity with respect to circulating tumor cells. However, additional studies are required before Exo can be effectively used in diagnostic and therapeutic applications in melanoma.

The role of extracellular vesicles when innate meets adaptive

Innate immune cells are recognized for their rapid and critical contribution to the body's first line of defense against invading pathogens and harmful agents. These actions can be further amplified by specific adaptive immune responses adapted to the activating stimulus. Recently, the awareness has grown that virtually all innate immune cells, i.e., mast cells, neutrophils, macrophages, eosinophils, basophils, and NK cells, are able to communicate with dendritic cells (DCs) and/or T and B cells, and thereby significantly contribute to the orchestration of adaptive immune responses. The means of communication that are thus far primarily associated with this function are cell-cell contacts and the release of a broad range of soluble mediators. Moreover, the possible contribution of innate immune cell-derived extracellular vesicles (EVs) to the modulation of adaptive immunity will be outlined in this review. EVs are submicron particles composed of a lipid bilayer, proteins, and nucleic acids released by cells in a regulated fashion. EVs are involved in intercellular communication between multiple cell types, including those of the immune system. A good understanding of the mechanisms by which innate immune cell-derived EVs influence adaptive immune responses, or vice versa, may reveal novel insights in the regulation of the immune system and can open up new possibilities for EVs (or their components) in controlling immune responses, either as a therapy, target, or as an adjuvant in future immune modulating treatments.

Regulated Mesenchymal Stem Cells Mediated Colon Cancer Therapy Assessed by Reporter Gene Based Optical Imaging

Colorectal cancer is the most common cancer in both men and women and the second most common cause of cancer-related deaths. Suicide gene-based therapy with suicide gene-transduced mesenchymal stem cells (MSCs) is a promising therapeutic strategy. A tetracycline-controlled Tet-On inducible system used to regulate gene expression may be a useful tool for gene-based therapies. The aim of this study was to develop therapeutic MSCs with a suicide gene that is induced by an artificial stimulus, to validate therapeutic gene expression, and to monitor the MSC therapy for colon cancer using optical molecular imaging. For our study, we designed the Tet-On system using a retroviral vector and developed a response plasmid RetroX-TRE (tetracycline response element) expressing a mutant form of herpes simplex virus thymidine kinase (HSV1-sr39TK) with dual reporters (eGFP-Fluc2). Bone marrow-derived MSCs were transduced using a RetroX-Tet3G (Clontech, CA, USA) regulatory plasmid and RetroX-TRE-HSV1-sr39TK-eGFP-IRES-Fluc2, for a system with a Tet-On (MSC-Tet-TK/Fluc2 or MSC-Tet-TK) or without a Tet-On (MSC-TK/Fluc2 or MSC-TK) function. Suicide gene engineered MSCs were co-cultured with colon cancer cells (CT26/Rluc) in the presence of the prodrug ganciclovir (GCV) after stimulation with or without doxycycline (DOX). Treatment efficiency was monitored by assessing Rluc (CT26/Rluc) and Fluc (MSC-Tet-TK and MSC-TK) activity using optical imaging. The bystander effect of therapeutic MSCs was confirmed in CT26/Rluc cells after GCV treatment. Rluc activity in CT26/Rluc cells decreased significantly with GCV treatment of DOX(+) cells (p < 0.05 and 0.01) whereas no significant changes were observed in DOX(-) cells. In addition, Fluc activity in also decreased significantly with DOX(+) MSC-Tet-TK cells, but no signal was observed in DOX(-) cells. In addition, an MSC-TK bystander effect was also confirmed. We assessed therapy with this system in a colon cancer xenograft model (CT26/Rluc). We successfully transduced cells and developed a Tet-On system with the suicide gene HSV1-sr39TK. Our results confirmed the therapeutic efficiency of a suicide gene with the Tet-On system for colon cancer. In addition, our results provide an innovative therapeutic approach using the Tet-On system to eradicate tumors by administration of MSC-Tet-TK cells with DOX and GCV.

Exosomes derived from cancerous and non-cancerous cells regulate the anti-tumor response in the tumor microenvironment

The tumor microenvironment (TME) is a unique platform of cancer biology that considers the local cellular environment in which a tumor exists. Increasing evidence points to the TME as crucial for either promoting immune tumor rejection or protecting the tumor. The TME includes surrounding blood vessels, the extracellular matrix (ECM), a variety of immune and regulatory cells, and signaling factors. Exosomes have emerged to be molecular contributors in cancer biology, and to modulate and affect the constituents of the TME. Exosomes are small (40-150 nm) membrane vesicles that are derived from an endocytic nature and are later excreted by cells. Depending on the cells from which they originate, exosomes can play a role in tumor suppression or tumor progression. Tumor-derived exosomes (TDEs) have their own unique phenotypic functions. Evidence points to TDEs as key players involved in tumor growth, tumorigenesis, angiogenesis, dysregulation of immune cells and immune escape, metastasis, and resistance to therapies, as well as in promoting anti-tumor response. General exosomes, TDEs, and their influence on the TME are an area of promising research that may provide potential biomarkers for therapy, potentiation of anti-tumor response, development of exosome-based vaccines, and exosome-derived nanocarriers for drugs.

An Update on in Vivo Imaging of Extracellular Vesicles as Drug Delivery Vehicles

Extracellular vesicles (EVs) are currently being considered as promising drug delivery vehicles. EVs are naturally occurring vesicles that exhibit many characteristics favorable to serve as drug delivery vehicles. In addition, EVs have inherent properties for treatment of cancers and other diseases. For research and clinical translation of use of EVs as drug delivery vehicles, in vivo tracking of EVs is essential. The latest molecular imaging techniques enable the tracking of EVs in living animals. However, each molecular imaging technique has its certain advantages and limitations for the in vivo imaging of EVs; therefore, understanding the molecular imaging techniques is essential to select the most appropriate imaging technology to achieve the desired imaging goal. In this review, we summarize the characteristics of EVs as drug delivery vehicles and the molecular imaging techniques used in visualizing and monitoring EVs in in vivo environments. Furthermore, we provide a perceptual vision of EVs as drug delivery vehicles and in vivo monitoring of EVs using molecular imaging technologies.

Exosome-Based Cell-Cell Communication in the Tumor Microenvironment

Tumors are not isolated entities, but complex systemic networks involving cell-cell communication between transformed and non-transformed cells. The milieu created by tumor-associated cells may either support or halt tumor progression. In addition to cell-cell contact, cells communicate through secreted factors via a highly complex system involving characteristics such as ligand concentration, receptor expression and integration of diverse signaling pathways. Of these, extracellular vesicles, such as exosomes, are emerging as novel cell-cell communication mediators in physiological and pathological scenarios. Exosomes, membrane vesicles of endocytic origin released by all cells (both healthy and diseased), ranging in size from 30 to 150 nm, transport all the main biomolecules, including lipids, proteins, DNAs, messenger RNAs and microRNA, and perform intercellular transfer of components, locally and systemically. By acting not only in tumor cells, but also in tumor-associated cells such as fibroblasts, endothelium, leukocytes and progenitor cells, tumor- and non-tumor cells-derived exosomes have emerged as new players in tumor growth and invasion, tumor-associated angiogenesis, tissue inflammation and immunologic remodeling. In addition, due to their property of carrying molecules from their cell of origin to the peripheral circulation, exosomes have been increasingly studied as sources of tumor biomarkers in liquid biopsies. Here we review the current literature on the participation of exosomes in the communication between tumor and tumor-associated cells, highlighting the role of this process in the setup of tumor microenvironments that modulate tumor initiation and metastasis.

A new bioluminescent reporter system to study the biodistribution of systematically injected tumor-derived bioluminescent extracellular vesicles in mice

In vivo biodistribution and fate of extracellular vesicles (EVs) are still largely unknown and require reliable in vivo tracking techniques. In this study, in vivo bioluminescence imaging (BLI) using Renilla luciferase (Rluc) was developed and applied to monitoring of EVs derived from thyroid cancer (CAL-62 cells) and breast cancer (MDA-MB-231) in nude mice after intravenous administration and was compared with a dye-based labeling method for EV derived from CAL-62 cells. The EVs were successfully labeled with Rluc and visualized by BLI in mice. In vivo distribution of the EVs, as measured by BLI, was consistent with the results of ex vivo organ analysis. EV-CAL-62/Rluc showed strong signals at lung followed by liver, spleen & kidney (P < 0.05). EV-MDA-MB-231/Rluc showed strong signals at liver followed by lung, spleen & kidney (P < 0.05). EV-CAL-62/Rluc and EV-MDA-MB-231/Rluc stayed in animal till day 9 and 3, respectively; showed a differential distribution. Spontaneous EV-CAL-62/Rluc shown distributed mostly to lung followed by liver, spleen & kidney. The new BLI system used to show spontaneous distribution of EV-CAL-62/Rluc in subcutaneous CAL-62/Rluc bearing mice. Dye (DiR)-labeled EV-CAL-62/Rluc showed a different distribution in vivo & ex vivo compared to EV-CAL-62/Rluc. Fluorescent signals were predominately detected in the liver (P < 0.05) and spleen (P < 0.05) regions. The bioluminescent EVs developed in this study may be used for monitoring of EVs in vivo. This novel reporter-imaging approach to visualization of EVs in real time is expected to pave the way for monitoring of EVs in EV-based treatments.

Extracellular vesicles derived from MSCs activates dermal papilla cell in vitro and promotes hair follicle conversion from telogen to anagen in mice

Hair loss is a common medical problem. In this study, we investigated the proliferation, migration, and growth factor expression of human dermal papilla (DP) cells in the presence or absence of treatment with mesenchymal stem cell extracellular vesicles (MSC-EVs). In addition, we tested the efficacy of MSC-EV treatment on hair growth in an animal model. MSC-EV treatment increased DP cell proliferation and migration, and elevated the levels of Bcl-2, phosphorylated Akt and ERK. In addition; DP cells treated with MSC-EVs displayed increased expression and secretion of VEGF and IGF-1. Intradermal injection of MSC-EVs into C57BL/6 mice promoted the conversion from telogen to anagen and increased expression of wnt3a, wnt5a and versican was demonstrated. The first time our results suggest that MSC-EVs have a potential to activate DP cells, prolonged survival, induce growth factor activation in vitro, and promotes hair growth in vivo.

Extracellular vesicles from mesenchymal stem cells activates VEGF receptors and accelerates recovery of hindlimb ischemia

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) are potential therapies for various diseases, but their angiogenic mechanisms of therapeutic efficacy remain unclear. Here, we describe how MSC-EVs, activates VEGF receptors and downstream angiogenesis pathways. Mouse MSC-EVs were isolated from cell culture medium and characterized using transmission electron microscopy, nanoparticle analysis, and western blotting. In vitro migration, proliferation, and tube formation assays using endothelial cells were used to assess the angiogenic potential of MSC-EVs, and revealed higher levels of cellular migration, proliferation, and tube formation after treatment. qRT-PCR and western blotting (WB) revealed higher protein and mRNA expression of the angiogenic genes VEGFR1 and VEGFR2 in mouse SVEC-4 endothelial cells after MSC-EVs treatment. Additionally, other vital pro-angiogenic pathways (SRC, AKT, and ERK) were activated by in vitro MSC-EV treatment. WB and qRT-PCR revealed enriched presence of VEGF protein and miR-210-3p in MSC-EV. The hindlimb ischemia mouse model was established and MSC-EVs with or without Matrigel (EV-MSC+Gel) were injected into the ischemic area and blood reperfusion was monitored using molecular imaging techniques. The in vivo administration of MSC-EVs increased both blood reperfusion and the formation of new blood vessels in the ischemic limb, with the addition of matrigel enhancing this effect further by releasing EVs slowly. MSC-EVs enhance angiogenesis in ischemic limbs, most likely via the overexpression of VEGFR1 and VEGFR2 in endothelial cells. These findings reveal a novel mechanism of activating receptors by MSC-EVs influence the angiogenesis.