Exosomes from myeloid-derived suppressor cells carry biologically active proteins

Exosome may be the next generation of promising cell-free vaccines

Traditional vaccines have limits against some persistent infections and pathogens. The development of novel vaccine technologies is particularly critical for the future. Exosomes play an important role in physiological and pathological processes. Exosomes present many advantages, such as inherent capacity being biocompatible, non-toxic, which make them a more desirable candidate for vaccines. However, research on exosomes are in their infancy and the barriers of low yield, low purity, and weak targeting of exosomes limit their applications in vaccines. Accordingly, further exploration is necessary to improve these problems and subsequently facilitate the functional studies of exosomes. In this study, we reviewed the origin, classification, functions, modifications, separation and purification, and characterization methods of exosomes. Meanwhile, we focused on the role and mechanism of exosomes for cancer and COVID-19 vaccines.

Extracellular vesicles derived from immune cells: Role in tumor therapy

Extracellular vesicles (EVs), which have a lipid nano-sized structure, are known to contain the active components of parental cells and play a crucial role in intercellular communication. The progression and metastasis of tumors are influenced by EVs derived from immune cells, which can simultaneously stimulate and suppress immune responses. In the past few decades, there has been a considerable focus on EVs due to their potential in various areas such as the development of vaccines, delivering drugs, making engineered modifications, and serving as biomarkers for diagnosis and prognosis. This review focuses on the substance information present in EVs derived from innate and adaptive immune cells, their effects on the immune system, and their applications in cancer treatment. While there are still challenges to overcome, it is important to explore the composition of immune cells released vesicles and their potential therapeutic role in tumor therapy. The review also highlights the current limitations and future prospects in utilizing EVs for treatment purposes.

The role of extracellular vesicles in immune cell exhaustion and resistance to immunotherapy

INTRODUCTION

Extracellular vesicles (EVs) are membrane-bound nanoparticles for intercellular communication. Subtypes of EVs, namely exosomes and microvesicles transfer diverse, bioactive cargo to their target cells and eventually interfere with immune responses. Despite being a promising approach, cancer immunotherapy currently faces several challenges including immune resistance. EVs secreted from various sources in the tumor microenvironment provoke immune cell exhaustion and lower the efficacy of immunological treatments, such as CAR T cells and immune checkpoint inhibitors.

AREAS COVERED

This article goes through the mechanisms of action of various types of EVs in inhibiting immune response and immunotherapies, and provides a comprehensive review of EV-based treatments.

EXPERT OPINION

By making use of the distinctive features of EVs, natural or modified EVs are innovatively utilized as novel cancer therapeutics. They are occasionally coupled with currently established treatments to overcome their inadequacies. Investigating the properties and interactions of EVs and EV-based treatments is crucial for determining future steps in cancer therapeutics.

Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.

Systematic review and bioinformatics analysis of plasma and serum extracellular vesicles proteome in type 2 diabetes

Background

Type 2 diabetes (T2D) is a complex metabolic ailment marked by a global high prevalence and significant attention in primary healthcare settings due to its elevated morbidity and mortality rates. The pathophysiological mechanisms underlying the onset and progression of this disease remain subjects of ongoing investigation. Recent evidence underscores the pivotal role of the intricate intercellular communication network, wherein cell-derived vesicles, commonly referred to as extracellular vesicles (EVs), emerge as dynamic regulators of diabetes-related complications. Given that the protein cargo carried by EVs is contingent upon the metabolic conditions of the originating cells, particular proteins may serve as informative indicators for the risk of activating or inhibiting signaling pathways crucial to the progression of T2D complications.

Methods

In this study, we conducted a systematic review to analyze the published evidence on the proteome of EVs from the plasma or serum of patients with T2D, both with and without complications (PROSPERO: CRD42023431464).

Results

Nine eligible articles were systematically identified from the databases, and the proteins featured in these articles underwent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. We identified changes in the level of 426 proteins, with CST6, CD55, HBA1, S100A8, and S100A9 reported to have high levels, while FGL1 exhibited low levels.

Conclusion

These proteins are implicated in pathophysiological mechanisms such as inflammation, complement, and platelet activation, suggesting their potential as risk markers for T2D development and progression. Further studies are required to explore this topic in greater detail.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

Biological mass spectrometry enables spatiotemporal 'omics: From tissues to cells to organelles

Biological processes unfold across broad spatial and temporal dimensions, and measurement of the underlying molecular world is essential to their understanding. Interdisciplinary efforts advanced mass spectrometry (MS) into a tour de force for assessing virtually all levels of the molecular architecture, some in exquisite detection sensitivity and scalability in space-time. In this review, we offer vignettes of milestones in technology innovations that ushered sample collection and processing, chemical separation, ionization, and 'omics analyses to progressively finer resolutions in the realms of tissue biopsies and limited cell populations, single cells, and subcellular organelles. Also highlighted are methodologies that empowered the acquisition and analysis of multidimensional MS data sets to reveal proteomes, peptidomes, and metabolomes in ever-deepening coverage in these limited and dynamic specimens. In pursuit of richer knowledge of biological processes, we discuss efforts pioneering the integration of orthogonal approaches from molecular and functional studies, both within and beyond MS. With established and emerging community-wide efforts ensuring scientific rigor and reproducibility, spatiotemporal MS emerged as an exciting and powerful resource to study biological systems in space-time.

Effects of extracellular vesicle-derived noncoding RNAs on pre-metastatic niche and tumor progression

A pre-metastatic niche (PMN) is a protective microenvironment that facilitates the colonization of disseminating tumor cells in future metastatic organs. Extracellular vesicles (EVs) play a role in intercellular communication by delivering cargoes, such as noncoding RNAs (ncRNAs). The pivotal role of extracellular vesicle-derived noncoding RNAs (EV-ncRNAs) in the PMN has attracted increasing attention. In this review, we summarized the effects of EV-ncRNAs on the PMN in terms of immunosuppression, vascular permeability and angiogenesis, inflammation, metabolic reprogramming, and fibroblast alterations. In particular, we provided a comprehensive overview of the effects of EV-ncRNAs on the PMN in different cancers. Finally, we discussed the promising clinical applications of EV-ncRNAs, including their potential as diagnostic and prognostic markers and therapeutic targets.

S100A8/A9: An emerging player in sepsis and sepsis-induced organ injury

Sepsis, the foremost contributor to mortality in intensive care unit patients, arises from an uncontrolled systemic response to invading infections, resulting in extensive harm across multiple organs and systems. Recently, S100A8/A9 has emerged as a promising biomarker for sepsis and sepsis-induced organ injury, and targeting S100A8/A9 appeared to ameliorate inflammation-induced tissue damage and improve adverse outcomes. S100A8/A9, a calcium-binding heterodimer mainly found in neutrophils and monocytes, serves as a causative molecule with pro-inflammatory and immunosuppressive properties, which are vital in the pathogenesis of sepsis. Therefore, improving our comprehension of how S100A8/A9 acts as a pathological player in the development of sepsis is imperative for advancing research on sepsis. Our review is the first-to the best of our knowledge-to discuss the biology of S100A8/A9 and its release mechanisms, summarize recent advances concerning the vital roles of S100A8/A9 in sepsis and the consequential organ damage, and underscore its potential as a promising diagnostic biomarker and therapeutic target for sepsis.

MDSCs-derived GPR84 induces CD8+ T-cell senescence via p53 activation to suppress the antitumor response

BACKGROUNDS

G-protein-coupled receptor 84 (GPR84) marks a subset of myeloid-derived suppressor cells (MDSCs) with stronger immunosuppression in the tumor microenvironment. Yet, how GPR84 endowed the stronger inhibition of MDSCs to CD8+ T cells function is not well established. In this study, we aimed to identify the underlying mechanism behind the immunosuppression of CD8+ T cells by GPR84+ MDSCs.

METHODS

The role and underlying mechanism that MDSCs or exosomes (Exo) regulates the function of CD8+ T cells were investigated using immunofluorescence, fluorescence activating cell sorter (FACS), quantitative real-time PCR, western blot, ELISA, Confocal, RNA-sequencing (RNA-seq), etc. In vivo efficacy and mechanistic studies were conducted with wild type, GPR84 and p53 knockout C57/BL6 mice.

RESULTS

Here, we showed that the transfer of GPR84 from MDSCs to CD8+ T cells via the Exo attenuated the antitumor response. This inhibitory effect was also observed in GPR84-overexpressed CD8+ T cells, whereas depleting GPR84 elevated CD8+ T cells proliferation and function in vitro and in vivo. RNA-seq analysis of CD8+ T cells demonstrated the activation of the p53 signaling pathway in CD8+ T cells treated with GPR84+ MDSCs culture medium. While knockout p53 did not induce senescence in CD8+ T cells treated with GPR84+ MDSCs. The per cent of GPR84+ CD8+ T cells work as a negative indicator for patients' prognosis and response to chemotherapy.

CONCLUSIONS

These data demonstrated that the transfer of GPR84 from MDSCs to CD8+ T cells induces T-cell senescence via the p53 signaling pathway, which could explain the strong immunosuppression of GPR84 endowed to MDSCs.

Haematopoietic cell-derived exosomes in cancer development and therapeutics: From basic science to clinical practice

BACKGROUND

The tumour microenvironment (TME) is a specialised niche involving intercellular communication among cancer cells and various host cells. Among the host cells, the quantity and quality of immune cells within the TME play essential roles in cancer development and management. The immunologically suppressive, so-called 'cold' TME established by a series of tumour-host interactions, including generating immunosuppressive cytokines and recruiting regulatory host immune cells, is associated with resistance to therapies and worse clinical outcomes.

MAIN BODY

Various therapeutic approaches have been used to target the cold TME, including immune checkpoint blockade therapy and adoptive T-cell transfer. A promising, less explored therapeutic strategy involves targeting TME-associated exosomes. Exosomes are nanometer-sized, extracellular vesicles that transfer material from donor to recipient cells. These particles can reprogram the recipient cells and modulate the TME. In particular, exosomes from haematopoietic cells are known to promote or suppress cancer progression under specific conditions. Understanding the effects of haematopoietic cell-secreted exosomes may foster the development of therapeutic exosomes (tExos) for personalised cancer treatment. However, the development of exosome-based therapies has unique challenges, including scalable production, purification, storage and delivery of exosomes and controlling batch variations. Clinical trials are being conducted to verify the safety, feasibility, availability and efficacy of tExos.

CONCLUSION

This review summarises our understanding of how haematopoietic cell-secreted exosomes regulate the TME and antitumour immunity and highlights present challenges and solutions for haematopoietic cell-derived exosome-based therapies.

Extracellular Vesicles from Immune Cells: A Biomedical Perspective

Research on the role of extracellular vesicles (sEV) in physiology has demonstrated their undoubted importance in processes such as the transportation of molecules with significance for cell metabolism, cell communication, and the regulation of mechanisms such as cell differentiation, inflammation, and immunity. Although the role of EVs in the immune response is actively investigated, there is little literature revising, in a comprehensive manner, the role of small EVs produced by immune cells. Here, we present a review of studies reporting the release of sEV by different types of leukocytes and the implications of such observations on cellular homeostasis. We also discuss the function of immune cell-derived sEV and their relationship with pathological states, highlighting their potential application in the biomedical field.

Targeting tumor-derived exosome-mediated premetastatic niche formation: The metastasis-preventive value of traditional Chinese medicine

Tumor-derived exosome (TDE)-mediated premetastatic niche (PMN) formation is a potential mechanism underlying the organotropic metastasis of primary tumors. Traditional Chinese medicine (TCM) has shown considerable success in preventing and treating tumor metastasis. However, the underlying mechanisms remain elusive. In this review, we discussed PMN formation from the perspectives of TDE biogenesis, cargo sorting, and TDE recipient cell alterations, which are critical for metastatic outgrowth. We also reviewed the metastasis-preventive effects of TCM, which act by targeting the physicochemical materials and functional mediators of TDE biogenesis, regulating the cargo sorting machinery and secretory molecules in TDEs, and targeting the TDE-recipient cells involved in PMN formation.

Myeloid-derived suppressor cells (MDSCs): what do we currently know about the effect they have against anti-PD-1/PD-L1 therapies?

Recent advances in cancer treatment such as PD-1/PD-L1 checkpoint inhibitors have prompted multiple research studies to determine all of the factors that influence response or failure to these new treatments. One of those identified factors is myeloid-derived suppressor cells (MDSCs). These cells were identified and described for the first time in 2007 in laboratory mice and cancer patients. Previous studies showed that a greater number of MDSCs was directly related to a greater tumour volume. There are two clearly identified subpopulations: Mononuclear-type myeloid-derived suppressor cells (M-MDSCs) and polymorphonuclear (PMN-MDSCs). These cell population subtypes play a very important role, depending on the type of cancer, since they have the particularity of expressing PD-L1, which interacts with PD-1, inhibiting the expansion of cytotoxic T lymphocytes, promoting resistance to these treatments.

TMT-Based Quantitative Proteomic and Physiological Analyses on Serums of Chinese Patients with Active Vitiligo

Purpose

Vitiligo is an acquired depigmented skin disorder. Though genetic background, autoimmune dysregulation, and oxidative stress were reported involved in the development of vitiligo, the exact pathogenesis remains largely unknown. This study aimed to investigate potential functional proteins, pathways, and serum biomarkers involved in active vitiligo.

Patients and Methods

Tandem Mass Tags (TMT) method was used to determine differentially expressed proteins (DEPs) in serum samples between 11 active vitiligo patients and 7 healthy controls of Chinese Han population.

Results

A total of 31 DEPs were identified (P < 0.05, fold change >1.2), with 21 proteins upregulated and 10 proteins downregulated in the vitiligo group. DEPs were enriched in GO terms such as "extracellular exosome" and "immunoglobulin receptor binding", as well as KEGG pathways including "cysteine and methionine metabolism" and other immune-related pathways. Furthermore, ALDH1A1 and EEF1G achieved areas under receiver-operating characteristic (ROC) curve of 0.9221 and 0.8571, respectively. The expression levels of these 2 proteins were validated in another active vitiligo patient group.

Conclusion

Our research provided novel insight into serum proteomic profile for vitiligo patients, detecting ALDH1A1 and EEF1G as potential biomarkers for active vitiligo and therapeutic intervention. Our work also detected several DEPs and associated pathways in the serum of active vitiligo patients, reinforcing the roles of retinoic acid and exosome processes in vitiligo pathogenesis.

The immunomodulatory role of exosomal microRNA networks in the crosstalk between tumor-associated myeloid-derived suppressor cells and tumor cells

Myeloid-derived suppressor cells (MDSCs) are considered a heterogeneous group of immature myeloid cells engaging in aggressive tumor progression and metastasis in the tumor microenvironment (TME) of patients diagnosed with cancer, through downregulation of anti-tumor immune responses. Exosomes are small vesicles carrying specific cargos, including proteins, lipids, and MicroRNA (miRNAs). Such exosomal miRNAs delivered by MDSCs and tumor cells are short noncoding RNAs mediating some of the immunosuppressive characteristics of MDSCs in the TME. However, when it comes to cancer diseases, how these miRNAs interact with MDSCs and encourage MDSCs differentiation and function need further investigations. In this review, we discuss MDSC-derived exosomal miRNAs and those derived from tumor cells (TDE) could modulate anti-tumor immunity and regulate the interaction between tumor cells and MDSCs in the TME. Afterward, we focus on dividing miRNAs, as an important substance interacting with MDSCs and tumor cells in the TME, into those have an immunosuppressive or stimulating effect not only on MDSCs expansion, differentiation, and suppressive function but also on tumor evasion.

Evolving strategies and application of proteins and peptide therapeutics in cancer treatment

Several proteins and peptides have therapeutic potential and can be used for cancer therapy. By binding to cell surface receptors and other indicators uniquely linked with or overexpressed on tumors compared to healthy tissue, protein biologics enhance the active targeting of cancer cells, as opposed to the passive targeting of cells by conventional small-molecule chemotherapeutics. This study focuses on peptide medications that exist to slow or stop tumor growth and the spread of cancer, demonstrating the therapeutic potential of peptides in cancer treatment. As an alternative to standard chemotherapy, peptides that selectively kill cancer cells while sparing healthy tissue are developing. A mountain of clinical evidence supports the efficacy of peptide-based cancer vaccines. Since a single treatment technique may not be sufficient to produce favourable results in the fight against cancer, combination therapy is emerging as an effective option to generate synergistic benefits. One example of this new area is the use of anticancer peptides in combination with nonpeptidic cytotoxic drugs or the combination of immunotherapy with conventional therapies like radiation and chemotherapy. This review focuses on the different natural and synthetic peptides obtained and researched. Discoveries, manufacture, and modifications of peptide drugs, as well as their contemporary applications, are summarized in this review. We also discuss the benefits and difficulties of potential advances in therapeutic peptides.

Here, There, and Everywhere: Myeloid-Derived Suppressor Cells in Immunology

Myeloid-derived suppressor cells (MDSCs) were initially identified in humans and mice with cancer where they profoundly suppress T cell- and NK cell-mediated antitumor immunity. Inflammation is a central feature of many pathologies and normal physiological conditions and is the dominant driving force for the accumulation and function of MDSCs. Therefore, MDSCs are present in conditions where inflammation is present. Although MDSCs are detrimental in cancer and conditions where cellular immunity is desirable, they are beneficial in settings where cellular immunity is hyperactive. Because MDSCs can be generated ex vivo, they are being exploited as therapeutic agents to reduce damaging cellular immunity. In this review, we discuss the detrimental and beneficial roles of MDSCs in disease settings such as bacterial, viral, and parasitic infections, sepsis, obesity, trauma, stress, autoimmunity, transplantation and graft-versus-host disease, and normal physiological settings, including pregnancy and neonates as well as aging. The impact of MDSCs on vaccination is also discussed.

Formation of pre-metastatic niches induced by tumor extracellular vesicles in lung metastasis

There are a number of malignant tumors that metastasize into the lung as one of their most common sites of dissemination. The successful infiltration of tumor cells into distant organs is the result of the cooperation between tumor cells and distant host cells. When tumor cells have not yet reached distant organs, in situ tumor cells secrete extracellular vesicles (EVs) carrying important biological information. In recent years, scholars have found that tumor cells-derived EVs act as the bridge between orthotopic tumors and secondary metastases by promoting the formation of a pre-metastatic niche (PMN), which plays a key role in awakening dormant circulating tumor cells and promoting tumor cell colonization. This review provides an overview of multiple routes and mechanisms underlying PMN formation induced by EVs and summaries study findings that underline a potential role of EVs in the intervention of lung PMN, both as a target or a carrier for drug design. In this review, the underlying mechanisms of EVs in lung PMN formation are highlighted as well as potential applications to lung metastasis diagnosis and treatment.

Myeloid-Derived Suppressor Cells in Cancer and COVID-19 as Associated with Oxidative Stress

Myeloid-derived suppressor cells MDSCs are a heterogeneous population of cells that expand beyond their physiological regulation during pathologies such as cancer, inflammation, bacterial, and viral infections. Their key feature is their remarkable ability to suppress T cell and natural killer NK cell responses. Certain risk factors for severe COVID-19 disease, such as obesity and diabetes, are associated with oxidative stress. The resulting inflammation and oxidative stress can negatively impact the host. Similarly, cancer cells exhibit a sustained increase in intrinsic ROS generation that maintains the oncogenic phenotype and drives tumor progression. By disrupting endoplasmic reticulum calcium channels, intracellular ROS accumulation can disrupt protein folding and ultimately lead to proteostasis failure. In cancer and COVID-19, MDSCs consist of the same two subtypes (PMN-MSDC and M-MDSC). While the main role of polymorphonuclear MDSCs is to dampen the response of T cells and NK killer cells, they also produce reactive oxygen species ROS and reactive nitrogen species RNS. We here review the origin of MDSCs, their expansion mechanisms, and their suppressive functions in the context of cancer and COVID-19 associated with the presence of superoxide anion •O2- and reactive oxygen species ROS.

The role of myeloid derived suppressor cells in musculoskeletal disorders

The immune system is closely linked to bone homeostasis and plays a pivotal role in several pathological and inflammatory conditions. Through various pathways it modulates various bone cells and subsequently sustains the physiological bone metabolism. Myeloid-derived suppressor cells (MDSCs) are a group of heterogeneous immature myeloid-derived cells that can exert an immunosuppressive function through a direct cell-to-cell contact, secretion of anti-inflammatory cytokines or specific exosomes. These cells mediate the innate immune response to chronic stress on the skeletal system. In chronic inflammation, MDSCs act as an inner offset to rebalance overactivation of the immune system. Moreover, they have been found to be involved in processes responsible for bone remodeling in different musculoskeletal disorders, autoimmune diseases, infection, and cancer. These cells can not only cause bone erosion by differentiating into osteoclasts, but also alleviate the immune reaction, subsequently leading to long-lastingly impacted bone remodeling. In this review, we discuss the impact of MDSCs on the bone metabolism under several pathological conditions, the involved modulatory pathways as well as potential therapeutic targets in MDSCs to improve bone health.

The roles of small extracellular vesicles in cancer and immune regulation and translational potential in cancer therapy

Extracellular vesicles (EVs) facilitate the extracellular transfer of proteins, lipids, and nucleic acids and mediate intercellular communication among multiple cells in the tumour environment. Small extracellular vesicles (sEVs) are defined as EVs range in diameter from approximately 50 to 150 nm. Tumour-derived sEVs (TDsEVs) and immune cell-derived sEVs have significant immunological activities and participate in cancer progression and immune responses. Cancer-specific molecules have been identified on TDsEVs and can function as biomarkers for cancer diagnosis and prognosis, as well as allergens for TDsEVs-based vaccination. Various monocytes, including but not limited to dendritic cells (DCs), B cells, T cells, natural killer (NK) cells, macrophages, and myeloid-derived suppressor cells (MDSCs), secrete sEVs that regulate immune responses in the complex immune network with either protumour or antitumour effects. After engineered modification, sEVs from immune cells and other donor cells can provide improved targeting and biological effects. Combined with their naïve characteristics, these engineered sEVs hold great potential as drug carriers. When used in a variety of cancer therapies, they can adjunctly enhance the safety and antitumor efficacy of multiple therapeutics. In summary, both naïve sEVs in the tumour environment and engineered sEVs with effector cargoes are regarded as showing promising potential for use in cancer diagnostics and therapeutics.

Emerging innovations on exosome-based onco-therapeutics

Exosomes, nano-sized extracellular vesicles for intercellular communications, are gaining rapid momentum as a novel strategy for the diagnosis and therapeutics of a spectrum of diseases including cancers. Secreted by various cell sources, exosomes pertain numerous functionalities from their parental cells and have enhanced stability that enable them with many features favorable for clinical use and commercialization. This paper focuses on the possible roles of exosomes in cancer therapeutics and reviews current exosome-based innovations toward enhanced cancer management and challenges that limit their clinical translation. Importantly, this paper casts insights on how cold atmospheric plasma, an emerging anticancer strategy, may aid in innovations on exosome-based onco-therapeutics toward improved control over cancers.

Recent advances in conventional and unconventional vesicular secretion pathways in the tumor microenvironment

All cells in the changing tumor microenvironment (TME) need a class of checkpoints to regulate the balance among exocytosis, endocytosis, recycling and degradation. The vesicular trafficking and secretion pathways regulated by the small Rab GTPases and their effectors convey cell growth and migration signals and function as meditators of intercellular communication and molecular transfer. Recent advances suggest that Rab proteins govern conventional and unconventional vesicular secretion pathways by trafficking widely diverse cargoes and substrates in remodeling TME. The mechanisms underlying the regulation of conventional and unconventional vesicular secretion pathways, their action modes and impacts on the cancer and stromal cells have been the focus of much attention for the past two decades. In this review, we discuss the current understanding of vesicular secretion pathways in TME. We begin with an overview of the structure, regulation, substrate recognition and subcellular localization of vesicular secretion pathways. We then systematically discuss how the three fundamental vesicular secretion processes respond to extracellular cues in TME. These processes are the conventional protein secretion via the endoplasmic reticulum-Golgi apparatus route and two types of unconventional protein secretion via extracellular vesicles and secretory autophagy. The latest advances and future directions in vesicular secretion-involved interplays between tumor cells, stromal cell and host immunity are also described.

Exosomes derived from myeloid-derived suppressor cells facilitate castration-resistant prostate cancer progression via S100A9/circMID1/miR-506-3p/MID1

Background

Castration-resistant prostate cancer (CRPC) is a major cause of recurrence and mortality among prostate cancer (PCa) patients. Myeloid-derived suppressor cells (MDSCs) regulate castration resistance in PCa. Previously, it was shown that intercellular communication was efficiently mediated by exosomes (Exos), but the role and the mechanism of MDSC-derived Exos in CRPC progression was unclear.

Methods

In this study, the circRNA expression profiles in PC3 cells treated with MDSC-Exo and control cells were investigated using a circRNA microarray.

Results

The data showed that circMID1 (hsa_circ_0007718) expression was elevated in PC3 cells treated with MDSC-Exo. Moreover, high circMID1 expression was found in PCa compared with benign prostatic hyperplasia (BPH) tissues and in CRPC patients compared with hormone sensitive prostate cancer (HSPC) patients. Further studies showed that MDSC-Exo accelerated PCa cell proliferation, migration, and invasion, while circMID1 deficiency inhibited MDSC-Exo-regulated CRPC progression in vitro and in vivo. Mechanistically, MDSC-derived exosomal S100A9 increased circMID1 expression to sponge miR-506-3p, leading to increased MID1 expression and accelerated tumor progression.

Conclusion

Together, our results showed that a S100A9/circMID1/miR-506-3p/MID1 axis existed in MDSC-Exo-regulated CRPC progression, which provided novel insights into MDSC-Exo regulatory mechanisms in CRPC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03494-5.

Exosome-Mediated Immunosuppression in Tumor Microenvironments

Exosomes are membranous structures secreted by nearly all cell types. As critical messengers for intercellular communication, exosomes deliver bioactive cargoes to recipient cells and are involved in multiple physiopathological processes, including immunoregulation. Our pioneering study revealed that cancer cells release programmed death-ligand 1-positive exosomes into the circulation to counter antitumor immunity systemically via T cells. Tumor cell-derived exosomes (TDEs) also play an immunosuppressive role in other immunocytes, including dendritic cells (DCs), macrophages, natural killer (NK) cells, and myeloid-derived suppressor cells (MDSCs). Moreover, exosomes secreted by nontumor cells in the tumor microenvironments (TMEs) also exert immunosuppressive effects. This review systematically provides a summary of the immunosuppression induced by exosomes in tumor microenvironments, which modulates tumor growth, invasion, metastasis, and immunotherapeutic resistance. Additionally, therapeutic strategies targeting the molecular mechanism of exosome-mediated tumor development, which may help overcome several obstacles, such as immune tolerance in oncotherapy, are also discussed. Detailed knowledge of the specific functions of exosomes in antitumor immunity may contribute to the development of innovative treatments.

In vivo imaging of microenvironmental and anti-PD-L1-mediated dynamics in cancer using S100A8/S100A9 as an imaging biomarker

PURPOSE

As a promotor of tumor invasion and tumor microenvironment (TME) formation, the protein complex S100A8/S100A9 is associated with poor prognosis. Our aim was to further evaluate its origin and regulatory effects, and to establish an imaging biomarker for TME activity.

METHODS

S100A9-/-cells (ko) were created from syngeneic murine breast cancer 4T1 (high malignancy) and 67NR (low malignancy) wildtype (wt) cell lines and implanted into either female BALB/c wildtype or S100A9-/- mice (n = 10 each). Anti-S100A9-Cy5.5-targeted fluorescence reflectance imaging was performed at 0 h and 24 h after injection. Potential early changes of S100A9-presence under immune checkpoint inhibition (anti-PD-L1, n = 7 vs. rat IgG2b as isotype control, n = 3) were evaluated.

RESULTS

In S100A9-/-mice contrast-to-noise-ratios were significantly reduced for wt and S100A9-/-tumors. No significant differences were detected for 4T1 ko and 67NR ko cells as compared to wildtype cells. Under anti-PD-L1 treatment S100A9 presence significantly decreased compared with the control group.

CONCLUSION

Our results confirm a secretion of S100A8/S100A9 by the TME, while tumor cells do not apparently release the protein. Under immune checkpoint inhibition S100A9-imaging reports an early decrease of TME activity. Therefore, S100A9-specific imaging may serve as an imaging biomarker for TME formation and activity.

Exosomes for Regulation of Immune Responses and Immunotherapy

Exosomes are membrane-enveloped nanosized (30–150 nm) extracellular vesicles of endosomal origin produced by almost all cell types and encompass a multitude of functioning biomolecules. Exosomes have been considered crucial players of cell-to-cell communication in physiological and pathological conditions. Accumulating evidence suggests that exosomes can modulate the immune system by delivering a plethora of signals that can either stimulate or suppress immune responses, which have potential applications as immunotherapies for cancer and autoimmune diseases. Here, we discuss the current knowledge about the active biomolecular components of exosomes that contribute to exosomal function in modulating different immune cells and also how these immune cell-derived exosomes play critical roles in immune responses. We further discuss the translational potential of engineered exosomes as immunotherapeutic agents with their advantages over conventional nanocarriers for drug delivery and ongoing clinical trials.

Roles of the Exosomes Derived From Myeloid-Derived Suppressor Cells in Tumor Immunity and Cancer Progression

Tumor immunity is involved in malignant tumor progression. Myeloid-derived suppressor cells (MDSCs) play an irreplaceable role in tumor immunity. MDSCs are composed of immature myeloid cells and exhibit obvious immunomodulatory functions. Exosomes released by MDSCs (MDSCs-Exos) have similar effects to parental MDSCs in regulating tumor immunity. In this review, we provided a comprehensive description of the characteristics, functions and mechanisms of exosomes. We analyzed the immunosuppressive, angiogenesis and metastatic effects of MDSCs-Exos in different tumors through multiple perspectives. Immunotherapy targeting MDSCs-Exos has demonstrated great potential in cancers and non-cancerous diseases.

Targeting S100A9-ALDH1A1-retinoic acid signaling to suppress brain relapse in EGFR-mutant lung cancer

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib has significantly prolonged progression-free survival (PFS) in EGFR-mutant lung cancer patients, including those with brain metastases. However, despite striking initial responses, osimertinib-treated patients eventually develop lethal metastatic relapse, often to the brain. Although osimertinib-refractory brain relapse is a major clinical challenge, its underlying mechanisms remain poorly understood. Using metastatic models of EGFR-mutant lung cancer, we show that cancer cells expressing high intracellular S100A9 escape osimertinib and initiate brain relapses. Mechanistically, S100A9 upregulates ALDH1A1 expression and activates the retinoic acid (RA) signaling pathway in osimertinib-refractory cancer cells. We demonstrate that the genetic repression of S100A9, ALDH1A1, or RA receptors (RAR) in cancer cells, or treatment with a pan-RAR antagonist, dramatically reduces brain metastasis. Importantly, S100A9 expression in cancer cells correlates with poor PFS in osimertinib-treated patients. Our study therefore identifies a novel, therapeutically targetable S100A9-ALDH1A1-RA axis that drives brain relapse.

Polymorphonuclear Myeloid-Derived Suppressor Cells Are Abundant in Peripheral Blood of Cancer Patients and Suppress Natural Killer Cell Anti-Tumor Activity

Tumor microenvironment (TME) includes a wide variety of cell types and soluble factors capable of suppressing immune-responses. While the role of NK cells in TME has been analyzed, limited information is available on the presence and the effect of polymorphonuclear (PMN) myeloid-derived suppressor cells, (MDSC). Among the immunomodulatory cells present in TME, MDSC are potentially efficient in counteracting the anti-tumor activity of several effector cells. We show that PMN-MDSC are present in high numbers in the PB of patients with primary or metastatic lung tumor. Their frequency correlated with the overall survival of patients. In addition, it inversely correlated with low frequencies of NK cells both in the PB and in tumor lesions. Moreover, such NK cells displayed an impaired anti-tumor activity, even those isolated from PB. The compromised function of NK cells was consequent to their interaction with PMN-MDSC. Indeed, we show that the expression of major activating NK receptors, the NK cytolytic activity and the cytokine production were inhibited upon co-culture with PMN-MDSC through both cell-to-cell contact and soluble factors. In this context, we show that exosomes derived from PMN-MDSC are responsible of a significant immunosuppressive effect on NK cell-mediated anti-tumor activity. Our data may provide a novel useful tool to implement the tumor immunoscore. Indeed, the detection of PMN-MDSC in the PB may be of prognostic value, providing clues on the presence and extension of both adult and pediatric tumors and information on the efficacy not only of immune response but also of immunotherapy and, possibly, on the clinical outcome.

Extracellular heat shock proteins in cancer: From early diagnosis to new therapeutic approach

In cancer, human cells lose the ability to properly control the series of events that occur constantly during cell growth and division, including protein expression, stability, and dynamics. Heat shock proteins (Hsps) are key molecules in these events, constitutively expressed at high levels and could furthermore be induced by the response to cancer-induced stress. In tumor cells, Hsps have been shown to be implicated in the regulation of apoptosis, immune responses, angiogenesis and metastasis; in some cases, they can be overexpressed and dysregulated, representing important cancer hallmarks. In the past few years, it has been demonstrated that Hsps can be released by tumor cells through several secreting pathways, including the extracellular vesicles (EVs), thus modulating the tumor microenvironment as well as long-distance intercellular communication and metastatization. In this review, we discuss the role of extracellular Hsps in cancer, with a particular interest in Hsps in EVs. We would also like to highlight the importance of fully understanding of the role of extracellular Hsps released by EVs and encourage further research in this field the use of Hsps as early cancer biomarkers and therapeutic targets.

Extracellular vesicles in anti-tumor immunity

To what extent extracellular vesicles (EVs) can impact anti-tumor immune responses has only started to get unraveled. Their nanometer dimensions, their growing number of subtypes together with the difficulties in defining their origin hamper their investigation. The existence of tumor cell lines facilitated advance in cancer EV understanding, while capturing information about phenotypes and functions of immune cell EVs in this context is more complex. The advent of immunotherapy with immune checkpoint inhibitors has further deepened the need to dissect the impact of EVs during immune activation and response, not least to contribute unraveling and preventing the generation of resistance occurring in the majority of patients. Here we discuss the factors that influence anddrive the immune response in cancer patients in the context of cancer therapeutics and the roles or possible functions that EVs can have in this scenario. With immune cell-derived EVs as leitmotiv, we will journey from EV discovery and subtypes through physiological and pathological functions, from similarities with tumor EVs to measures to revert detrimental consequences on immune responses to cancer.

Proteomic signatures of myeloid derived suppressor cells from liver and lung metastases reveal functional divergence and potential therapeutic targets

Myeloid-derived suppressor cells (MDSCs) promote immunosuppressive activities in the tumor microenvironment (TME), resulting in increased tumor burden and diminishing the anti-tumor response of immunotherapies. While primary and metastatic tumors are typically the focal points of therapeutic development, the immune cells of the TME are differentially programmed by the tissue of the metastatic site. In particular, MDSCs are programmed uniquely within different organs in the context of tumor progression. Given that MDSC plasticity is shaped by the surrounding environment, the proteomes of MDSCs from different metastatic sites are hypothesized to be unique. A bottom-up proteomics approach using sequential window acquisition of all theoretical mass spectra (SWATH-MS) was used to quantify the proteome of CD11b⁺ cells derived from murine liver metastases (LM) and lung metastases (LuM). A comparative proteomics workflow was employed to compare MDSC proteins from LuM (LuM-MDSC) and LM (LM-MDSC) while also elucidating common signaling pathways, protein function, and possible drug-protein interactions. SWATH-MS identified 2516 proteins from 200 µg of sample. Of the 2516 proteins, 2367 have matching transcriptomic data. Upregulated proteins from lung and liver-derived murine CD11b⁺ cells with matching mRNA transcriptomic data were categorized based on target knowledge and level of drug development. Comparative proteomic analysis demonstrates that liver and lung tumor-derived MDSCs have distinct proteomes that may be subject to pharmacologic manipulation.

Exosomes in Inflammatory Bowel Disease: What Have We Learned So Far?

Inflammatory bowel disease (IBD) is an immune-mediated chronic inflammatory disease. Although the etiology is uncertain, there is marked disbalance of mucosal immune responses in part shaped by genetic susceptibility and intestinal microbial dysbiosis. Suppressing inflammatory activity adequately and maintaining this suppression are the main goals of current therapies. However, corticosteroids are only suitable for therapy of active disease, and the effects of immunosuppressive agents are mainly limited to maintenance of remission. Biologics have become widely available and provide therapeutic benefits to IBD patients. However, only a part of patients benefits from them. Thus, there is an urgent need for the development of new substances in the therapy of IBD. Exosomes are nanosized lipid vesicles identified recently. They are secreted from all living cells and then distributed in various human body fluids. The components, such as microRNAs and functional proteins, secreted by exosomes in different cells have been reported to be involved in the pathogenesis of IBD. Therefore, exosomes have the potential to become appealing particles in treating IBD as a cell-free therapeutic approach as well as biomarkers for diagnosis and monitoring disease status. Further studies are needed to investigate the practicality, safety and desirable effects of exosomes in clinical applications in IBD.

Characterization of systemic immunosuppression by IDH mutant glioma small extracellular vesicles

BACKGROUND

Gliomas are the most common primary brain tumors and are universally fatal. Mutations in the isocitrate dehydrogenase genes (IDH1 and IDH2) define a distinct glioma subtype associated with an immunosuppressive tumor microenvironment. Mechanisms underlying systemic immunosuppression in IDH mutant (mutIDH) gliomas are largely unknown. Here, we define genotype-specific local and systemic tumor immunomodulatory functions of tumor-derived glioma exosomes (TEX).

METHODS

TEX produced by human and murine wildtype and mutant IDH glioma cells (wtIDH and mutIDH, respectively) were isolated by size exclusion chromatography (SEC). TEX morphology, size, quantity, molecular profiles and biodistribution were characterized. TEX were injected into naive and tumor-bearing mice, and the local and systemic immune microenvironment composition was characterized.

RESULTS

Using in vitro and in vivo glioma models, we show that mutIDH TEX are more numerous, possess distinct morphological features and are more immunosuppressive than wtIDH TEX. mutIDH TEX cargo mimics their parental cells, and induces systemic immune suppression in naive and tumor-bearing mice. TEX derived from mutIDH gliomas and injected into wtIDH tumor-bearing mice reduce tumor-infiltrating effector lymphocytes, dendritic cells and macrophages, and increase circulating monocytes. Astonishingly, mutIDH TEX injected into brain tumor-bearing syngeneic mice accelerate tumor growth and increase mortality compared with wtIDH TEX.

CONCLUSIONS

Targeting of mutIDH TEX represents a novel therapeutic approach in gliomas.

Exosomes: Innocent Bystanders or Critical Culprits in Neurodegenerative Diseases

Extracellular vesicles (EVs) are nano-sized membrane-enclosed particles released by cells that participate in intercellular communication through the transfer of biologic material. EVs include exosomes that are small vesicles that were initially associated with the disposal of cellular garbage; however, recent findings point toward a function as natural carriers of a wide variety of genetic material and proteins. Indeed, exosomes are vesicle mediators of intercellular communication and maintenance of cellular homeostasis. The role of exosomes in health and age-associated diseases is far from being understood, but recent evidence implicates exosomes as causative players in the spread of neurodegenerative diseases. Cells from the central nervous system (CNS) use exosomes as a strategy not only to eliminate membranes, toxic proteins, and RNA species but also to mediate short and long cell-to-cell communication as carriers of important messengers and signals. The accumulation of protein aggregates is a common pathological hallmark in many neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and prion diseases. Protein aggregates can be removed and delivered to degradation by the endo-lysosomal pathway or can be incorporated in multivesicular bodies (MVBs) that are further released to the extracellular space as exosomes. Because exosome transport damaged cellular material, this eventually contributes to the spread of pathological misfolded proteins within the brain, thus promoting the neurodegeneration process. In this review, we focus on the role of exosomes in CNS homeostasis, their possible contribution to the development of neurodegenerative diseases, the usefulness of exosome cargo as biomarkers of disease, and the potential benefits of plasma circulating CNS-derived exosomes.

Immunosuppressive Effects of Myeloid-Derived Suppressor Cells in Cancer and Immunotherapy

The primary function of myeloid cells is to protect the host from infections. However, during cancer progression or states of chronic inflammation, these cells develop into myeloid-derived suppressor cells (MDSCs) that play a prominent role in suppressing anti-tumor immunity. Overcoming the suppressive effects of MDSCs is a major hurdle in cancer immunotherapy. Therefore, understanding the mechanisms by which MDSCs promote tumor growth is essential for improving current immunotherapies and developing new ones. This review explores mechanisms by which MDSCs suppress T-cell immunity and how this impacts the efficacy of commonly used immunotherapies.

Combined Effects of Myeloid Cells in the Neuroblastoma Tumor Microenvironment

Despite multimodal treatment, survival chances for high-risk neuroblastoma patients remain poor. Immunotherapeutic approaches focusing on the activation and/or modification of host immunity for eliminating tumor cells, such as chimeric antigen receptor (CAR) T cells, are currently in development, however clinical trials have failed to reproduce the preclinical results. The tumor microenvironment is emerging as a major contributor to immune suppression and tumor evasion in solid cancers and thus has to be overcome for therapies relying on a functional immune response. Among the cellular components of the neuroblastoma tumor microenvironment, suppressive myeloid cells have been described as key players in inhibition of antitumor immune responses and have been shown to positively correlate with more aggressive disease, resistance to treatments, and overall poor prognosis. This review article summarizes how neuroblastoma-driven inflammation induces suppressive myeloid cells in the tumor microenvironment and how they in turn sustain the tumor niche through suppressor functions, such as nutrient depletion and generation of oxidative stress. Numerous preclinical studies have suggested a range of drug and cellular therapy approaches to overcome myeloid-derived suppression in neuroblastoma that warrant evaluation in future clinical studies.

Alarming Cargo: The Role of Exosomes in Trauma-Induced Inflammation

Severe polytraumatic injury initiates a robust immune response. Broad immune dysfunction in patients with such injuries has been well-documented; however, early biomarkers of immune dysfunction post-injury, which are critical for comprehensive intervention and can predict the clinical course of patients, have not been reported. Current circulating markers such as IL-6 and IL-10 are broad, non-specific, and lag behind the clinical course of patients. General blockade of the inflammatory response is detrimental to patients, as a certain degree of regulated inflammation is critical and necessary following trauma. Exosomes, small membrane-bound extracellular vesicles, found in a variety of biofluids, carry within them a complex functional cargo, comprised of coding and non-coding RNAs, proteins, and metabolites. Composition of circulating exosomal cargo is modulated by changes in the intra- and extracellular microenvironment, thereby serving as a homeostasis sensor. With its extensively documented involvement in immune regulation in multiple pathologies, study of exosomal cargo in polytrauma patients can provide critical insights on trauma-specific, temporal immune dysregulation, with tremendous potential to serve as unique biomarkers and therapeutic targets for timely and precise intervention.

Role of Exosomes in Prostate Cancer Metastasis

Prostate cancer remains a life-threatening disease among men worldwide. The majority of PCa-related mortality results from metastatic disease that is characterized by metastasis of prostate tumor cells to various distant organs, such as lung, liver, and bone. Bone metastasis is most common in prostate cancer with osteoblastic and osteolytic lesions. The precise mechanisms underlying PCa metastasis are still being delineated. Intercellular communication is a key feature underlying prostate cancer progression and metastasis. There exists local signaling between prostate cancer cells and cells within the primary tumor microenvironment (TME), in addition to long range signaling wherein tumor cells communicate with sites of future metastases to promote the formation of pre-metastatic niches (PMN) to augment the growth of disseminated tumor cells upon metastasis. Over the last decade, exosomes/ extracellular vesicles have been demonstrated to be involved in such signaling. Exosomes are nanosized extracellular vesicles (EVs), between 30 and 150 nm in thickness, that originate and are released from cells after multivesicular bodies (MVB) fuse with the plasma membrane. These vesicles consist of lipid bilayer membrane enclosing a cargo of biomolecules, including proteins, lipids, RNA, and DNA. Exosomes mediate intercellular communication by transferring their cargo to recipient cells to modulate target cellular functions. In this review, we discuss the contribution of exosomes/extracellular vesicles in prostate cancer progression, in pre-metastatic niche establishment, and in organ-specific metastases. In addition, we briefly discuss the clinical significance of exosomes as biomarkers and therapeutic agents.

Myeloid-Derived Suppressor Cells: Facilitators of Cancer and Obesity-Induced Cancer

Immature myeloid cells at varied stages of differentiation, known as myeloid-derived suppressor cells (MDSC), are present in virtually all cancer patients. MDSC are profoundly immune-suppressive cells that impair adaptive and innate antitumor immunity and promote tumor progression through nonimmune mechanisms. Their widespread presence combined with their multitude of protumor activities makes MDSC a major obstacle to cancer immunotherapies. MDSC are derived from progenitor cells in the bone marrow and traffic through the blood to infiltrate solid tumors. Their accumulation and suppressive potency are driven by multiple tumor- and host-secreted proinflammatory factors and adrenergic signals that act via diverse but sometimes overlapping transcriptional pathways. MDSC also accumulate in response to the chronic inflammation and lipid deposition characteristic of obesity and contribute to the more rapid progression of cancers in obese individuals. This article summarizes the key aspects of tumor-induced MDSC with a focus on recent progress in the MDSC field.

Exosomal proteins: Key players mediating pre‑metastatic niche formation and clinical implications (Review)

Tumor metastasis is a destructive characteristic of malignant tumors and the fundamental reason why malignant tumors are difficult to cure. The concept of a pre‑metastatic niche (PMN) provides a novel way to elucidate the molecular mechanism of tumor metastasis. At present, the PMN has been considered as a critical determinant priming distal sites for metastasis. Accumulating evidence has suggested that exosomes are cellular communicators serving a pivotal role in mediating tumor cell metastasis by establishing the PMN. Among exosomal cargos, non‑coding RNAs and proteins are two commonly studied components; however, the latter has received less attention. The present review aimed to summarize the findings regarding cargo proteins selectively loaded in malignant tumor‑derived exosomes. Metastasis‑associated proteins have been demonstrated to be selectively enriched in malignant tumor‑derived exosomes. Exosomal proteins promote PMN formation to mediate the site‑specific metastasis of tumor cells by inducing lymphangiogenesis, angiogenesis and permeability, educating stromal cells, remodeling the extracellular matrix, and suppressing the antitumor immune response. These exosomal proteins have great potential in predicting organ‑directed metastasis and prognosis, as well as in cancer therapy.

Pathogenic Roles of S100A8 and S100A9 Proteins in Acute Myeloid and Lymphoid Leukemia: Clinical and Therapeutic Impacts

Deregulations of the expression of the S100A8 and S100A9 genes and/or proteins, as well as changes in their plasma levels or their levels of secretion in the bone marrow microenvironment, are frequently observed in acute myeloblastic leukemias (AML) and acute lymphoblastic leukemias (ALL). These deregulations impact the prognosis of patients through various mechanisms of cellular or extracellular regulation of the viability of leukemic cells. In particular, S100A8 and S100A9 in monomeric, homodimeric, or heterodimeric forms are able to modulate the survival and the sensitivity to chemotherapy of leukemic clones through their action on the regulation of intracellular calcium, on oxidative stress, on the activation of apoptosis, and thanks to their implications, on cell death regulation by autophagy and pyroptosis. Moreover, biologic effects of S100A8/9 via both TLR4 and RAGE on hematopoietic stem cells contribute to the selection and expansion of leukemic clones by excretion of proinflammatory cytokines and/or immune regulation. Hence, the therapeutic targeting of S100A8 and S100A9 appears to be a promising way to improve treatment efficiency in acute leukemias.

Characterization of the perioperative changes of exosomal immune-related cytokines induced by prostatectomy in early-stage prostate cancer patients

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are relevant in prostate cancer microenvironment collaborating in tumor development. The main tumor marker used in this disease, prostate-specific antigen (PSA), does not provide information related to this tumor microenvironment. Cancer cells secrete exosomes carrying bioactive molecules contributing to MDSCs recruitment and induction. The aim of this study was to characterize the perioperative changes of exosomal cytokines relevant in MDSCs recruitment induced by prostatectomy in prostate cancer patients.

METHODS

Blood was drawn from 26 early-stage prostate cancer patients before and after radical prostatectomy and from 16 healthy volunteers. Serum exosomes were separated by precipitation. Cytokines related with MDSC cell recruitment and activation CCL2, CXCL2, CXCL5, CXCL8, CXCL12, MIF, S100A9 and TGF-ß were measured in serum and serum-derived exosomes using immunometric assays.

RESULTS

All cytokines were detected both in serum and exosomes, except for CXCL12, which was detected only in serum. Exosomes were enriched specially in MIF, TGF-ß and CXCL2. Presurgical MIF levels in exosomes correlated negatively with serum PSA. Also, presurgical TGF-ß decreased both in serum and exosomes as Gleason score rises. Patientś presurgical exosomes had increased CCL2, CXCL5 and TGF-ß levels than exosomes from healthy controls. These differences were not observed when cytokines were analyzed in serum, except for TGF-ß. Cytokine levels of CCL2, CXCL5 decreased in patients' postsurgical exosomes, while TGF-ß further increased. On the contrary, S100A9 levels were lower in patientś presurgical exosomes but increased after radical prostatectomy.

CONCLUSIONS

Blood exosomal content in cytokines constitute an attractive source to evaluate MDSCs immunomodulators providing additional information related to tumor microenvironment in prostate cancer.

Dark-Side of Exosomes

Exosomes are nanoscale extracellular vesicles that can transport cargos of proteins, lipids, DNA, various RNA species and microRNAs (miRNAs). Exosomes can enter cells and deliver their contents to recipient cell. Owing to their cargo exosomes can transfer different molecules to the target cells and change the phenotype of these cells. The fate of the contents of an exosome depends on its target destination. Various mechanisms for exosome uptake by target cells have been proposed, but the mechanisms responsible for exosomes internalization into cells are still debated. Exosomes exposed cells produce labeled protein kinases, which are expressed by other cells. This means that these kinases are internalized by exosomes, and transported into the cytoplasm of recipient cells. Many studies have confirmed that exosomes are not only secreted by living cells, but also internalized or accumulated by the other cells. The "next cell hypothesis" supports the notion that exosomes constitute communication vehicles between neighboring cells. By this mechanism, exosomes participate in the development of diabetes and its associated complications, critically contribute to the spreading of neuronal damage in Alzheimer's disease, and non-proteolysed form of Fas ligand (mFasL)-bearing exosomes trigger the apoptosis of T lymphocytes. Furthermore, exosomes derived from human B lymphocytes induce antigen-specific major histocompatibility complex (MHC) class II-restricted T cell responses. Interestingly, exosomes secreted by cancer cells have been demonstrated to express tumor antigens, as well as immune suppressive molecules. This process is defined as "exosome-immune suppression" concept. The interplay via the exchange of exosomes between cancer cells and between cancer cells and the tumor stroma promote the transfer of oncogenes and onco-miRNAs from one cell to other. Circulating exosomes that are released from hypertrophic adipocytes are effective in obesity-related complications. On the other hand, the "inflammasome-induced" exosomes can activate inflammatory responses in recipient cells. In this chapter protein kinases-related checkpoints are emphasized considering the regulation of exosome biogenesis, secretory traffic, and their impacts on cell death, tumor growth, immune system, and obesity.

Interaction Between MDSC and NK Cells in Solid and Hematological Malignancies: Impact on HSCT

Myeloid derived suppressor cells (MDSC) are heterogeneous populations that through the release of soluble factors and/or by cell-to-cell interactions suppress both innate and adaptive immune effector cells. In pathological conditions, characterized by the presence of inflammation, a partial block in the differentiation potential of myeloid precursors causes an accumulation of these immunosuppressive cell subsets both in peripheral blood and in tissues. On the contrary, NK cells represent a major player of innate immunity able to counteract tumor growth. The anti-tumor activity of NK cells is primarily related to their cytolytic potential and to the secretion of soluble factors or cytokines that may act on tumors either directly or indirectly upon the recruitment of other cell types. NK cells have been shown to play a fundamental role in haploidentical hemopoietic stem cell transplantation (HSCT), for the therapy of high-risk leukemias. A deeper analysis of MDSC functional effects demonstrated that these cells are capable, through several mechanisms, to reduce the potent GvL activity exerted by NK cells. It is conceivable that, in this transplantation setting, the MDSC-removal or -inactivation may represent a promising strategy to restore the anti-leukemia effect mediated by NK cells. Thus, a better knowledge of the cellular interactions occurring in the tumor microenvironment could promote the development of novel therapeutic strategies for the treatment of solid and hematological malignances.

Molecular cargo in myeloid-derived suppressor cells and their exosomes

Collaborative research is reviewed in which mass spectrometry-based proteomics and next generation sequencing were used qualitatively and quantitatively to interrogate proteins and RNAs carried in intact myeloid-derived suppressor cells (MDSC) and exosomes shed in vitro by MDSC. In aggregate exosomes more than 4000 proteins were identified, including annexins and immunosuppressive mediators. Bioassays showed that exosomes induce MDSC chemotaxis dependent on S100A8 and S100A9 in their cargo. Surface selective chemistry identified glycoproteins on MDSC and exosome surfaces, including CD47 and thrombospondin 1, which both facilitate exosome-catalyzed chemotaxis. Large numbers of mRNAs and microRNAs were identified in aggregate exosomes, whose potential functions in receptor cells include angiogenesis, and proinflammatory and immunosuppressive activities. Inflammation was found to have asymmetric effects on MDSC and exosomal cargos. Collectively, our findings indicate that the exosomes shed by MDSC provide divergent and complementary functions that support the immunosuppression and tumor promotion activities of MDSC.

Interaction Between MDSC and NK Cells in Solid and Hematological Malignancies: Impact on HSCT

Myeloid derived suppressor cells (MDSC) are heterogeneous populations that through the release of soluble factors and/or by cell-to-cell interactions suppress both innate and adaptive immune effector cells. In pathological conditions, characterized by the presence of inflammation, a partial block in the differentiation potential of myeloid precursors causes an accumulation of these immunosuppressive cell subsets both in peripheral blood and in tissues. On the contrary, NK cells represent a major player of innate immunity able to counteract tumor growth. The anti-tumor activity of NK cells is primarily related to their cytolytic potential and to the secretion of soluble factors or cytokines that may act on tumors either directly or indirectly upon the recruitment of other cell types. NK cells have been shown to play a fundamental role in haploidentical hemopoietic stem cell transplantation (HSCT), for the therapy of high-risk leukemias. A deeper analysis of MDSC functional effects demonstrated that these cells are capable, through several mechanisms, to reduce the potent GvL activity exerted by NK cells. It is conceivable that, in this transplantation setting, the MDSC-removal or -inactivation may represent a promising strategy to restore the anti-leukemia effect mediated by NK cells. Thus, a better knowledge of the cellular interactions occurring in the tumor microenvironment could promote the development of novel therapeutic strategies for the treatment of solid and hematological malignances.