Separation of plasma-derived exosomes into CD3(+) and CD3(-) fractions allows for association of immune cell and tumour cell markers with disease activity in HNSCC patients

The role of extracellular vesicle immune checkpoints in cancer

Immune checkpoints (ICPs) play a crucial role in regulating the immune response. In the tumor, malignant cells can hijack the immunosuppressive effects of inhibitory ICPs to promote tumor progression. Extracellular vesicles (EVs) are produced by a variety of cells and contain bioactive molecules on their surface or within their lumen. The expression of ICPs has also been detected in EVs. In vitro and in vivo studies have shown that extracellular vesicle immune checkpoints (EV ICPs) have immunomodulatory effects and are involved in tumor immunity. EV ICPs isolated from the peripheral blood of cancer patients are closely associated with the tumor progression and the prognosis of cancer patients. Blocking inhibitory ICPs has been recognized as an effective strategy in cancer treatment. However, the efficacy of immune checkpoint inhibitors (ICIs) in cancer treatment is hindered by the emergence of therapeutic resistance, which limits their widespread use. Researchers have demonstrated that EV ICPs are correlated with clinical response to ICIs therapy and were involved in therapeutic resistance. Therefore, it is essential to investigate the immunomodulatory effects, underlying mechanisms, and clinical significance of EV ICPs in cancer. This review aims to comprehensively explore these aspects. We have provided a comprehensive description of the cellular origins, immunomodulatory effects, and clinical significance of EV ICPs in cancer, based on relevant studies.

Exosomal PD-L1 in cancer and other fields: recent advances and perspectives

PD-1/PD-L1 signaling is a key factor of local immunosuppression in the tumor microenvironment. Immune checkpoint inhibitors targeting PD-1/PD-L1 signaling have achieved tremendous success in clinic. However, several types of cancer are particularly refractory to the anti-PD-1/PD-L1 treatment. Recently, a series of studies reported that IFN-γ can stimulate cancer cells to release exosomal PD-L1 (exoPD-L1), which possesses the ability to suppress anticancer immune responses and is associated with anti-PD-1 response. In this review, we introduce the PD-1/PD-L1 signaling, including the so-called 'reverse signaling'. Furthermore, we summarize the immune treatments of cancers and pay more attention to immune checkpoint inhibitors targeting PD-1/PD-L1 signaling. Additionally, we review the action mechanisms and regulation of exoPD-L1. We also introduce the function of exoPD-L1 as biomarkers. Finally, we review the methods for analyzing and quantifying exoPD-L1, the therapeutic strategies targeting exoPD-L1 to enhance immunotherapy and the roles of exoPD-L1 beyond cancer. This comprehensive review delves into recent advances of exoPD-L1 and all these findings suggest that exoPD-L1 plays an important role in both cancer and other fields.

The link between intracellular calcium signaling and exosomal PD-L1 in cancer progression and immunotherapy

Exosomes are small membrane vesicles containing microRNA, RNA, DNA fragments, and proteins that are transferred from donor cells to recipient cells. Tumor cells release exosomes to reprogram the factors associated with the tumor microenvironment (TME) causing tumor metastasis and immune escape. Emerging evidence revealed that cancer cell-derived exosomes carry immune inhibitory molecule program death ligand 1 (PD-L1) that binds with receptor program death protein 1 (PD-1) and promote tumor progression by escaping immune response. Currently, some FDA-approved monoclonal antibodies are clinically used for cancer treatment by blocking PD-1/PD-L1 interaction. Despite notable treatment outcomes, some patients show poor drug response. Exosomal PD-L1 plays a vital role in lowering the treatment response, showing resistance to PD-1/PD-L1 blockage therapy through recapitulating the effect of cell surface PD-L1. To enhance therapeutic response, inhibition of exosomal PD-L1 is required. Calcium signaling is the central regulator of tumorigenesis and can regulate exosome biogenesis and secretion by modulating Rab GTPase family and membrane fusion factors. Immune checkpoints are also connected with calcium signaling and calcium channel blockers like amlodipine, nifedipine, lercanidipine, diltiazem, and verapamil were also reported to suppress cellular PD-L1 expression. Therefore, to enhance the PD-1/PD-L1 blockage therapy response, the reduction of exosomal PD-L1 secretion from cancer cells is in our therapeutic consideration. In this review, we proposed a therapeutic strategy by targeting calcium signaling to inhibit the expression of PD-L1-containing exosome levels that could reduce the anti-PD-1/PD-L1 therapy resistance and increase the patient's drug response rate.

Arginase-1 in Plasma-Derived Exosomes as Marker of Metastasis in Patients with Head and Neck Squamous Cell Carcinoma

Immunoregulatory Arginase-1 (Arg-1) is present in the tumor microenvironment of solid tumors. Its association to clinicopathology and its prognostic impact are inconsistent among different tumor types and biological fluids. This study evaluated Arg-1 protein levels in tumors and the circulation of patients with head and neck squamous cell carcinoma (HNSCC) in relation to clinical stage and prognosis. Tumor Arg-1 expression was monitored via immunohistochemistry while plasma Arg-1 levels via ELISA in 37 HNSCC patients. Arg-1 presence in plasma-derived exosomes was assessed using Western blots in 20 HNSCC patients. High tumor Arg-1 expression correlated with favorable clinicopathology and longer recurrence-free survival (RFS), while high plasma Arg-1 levels were associated with unfavorable clinicopathology. All patients with low tumor and high plasma Arg-1 had nodal metastases and developed recurrence. This discrepancy was attributed to the presence of Arg-1-carrying exosomes. Arg-1 was found in plasma-derived exosomes from all HNSCC patients. High exosomal Arg-1 levels were associated with positive lymph nodes and short RFS. Circulating Arg-1+ exosomes represent a mechanism of active Arg-1 export from the tumor to the periphery. Exosomes reflected biologically relevant Arg-1 levels in metastatic HNSCC and emerged as potentially more accurate biomarkers of metastatic disease and RFS than tissue or plasma Arg-1 levels.

Landscape of tumor and immune system cells-derived exosomes in lung cancer: mediators of antitumor immunity regulation

The immune system plays a critical role in cancer, including lung cancer, which is the leading cause of cancer-related deaths worldwide. Immunotherapy, particularly immune checkpoint blockade, has revolutionized the treatment of lung cancer, but a large subset of patients either do not respond or develop resistance. Exosomes, essential mediators of cell-to-cell communication, exert a profound influence on the tumor microenvironment and the interplay between cancer and the immune system. This review focuses on the role of tumor-derived exosomes and immune cells-derived exosomes in the crosstalk between these cell types, influencing the initiation and progression of lung cancer. Depending on their cell of origin and microenvironment, exosomes can contain immunosuppressive or immunostimulatory molecules that can either promote or inhibit tumor growth, thus playing a dual role in the disease. Furthermore, the use of exosomes in lung cancer immunotherapy is discussed. Their potential applications as cell-free vaccines and drug delivery systems make them an attractive option for lung cancer treatment. Additionally, exosomal proteins and RNAs emerge as promising biomarkers that could be employed for the prediction, diagnosis, prognosis and monitoring of the disease. In summary, this review assesses the relationship between exosomes, lung cancer, and the immune system, shedding light on their potential clinical applications and future perspectives.

Immunosuppressive effect of small extracellular vesicle PD-L1 is restricted by co-expression of CD80

BACKGROUND

The PD-L1 on tumor cell-derived small extracellular vesicles (sEVs) can suppress the proliferation and cytokine production of T cells. However, PD-L1 can also be expressed by non-tumor cells. The present study is designed to test whether immunocytes release immunosuppressive PD-L1-positive sEVs.

METHODS

sEVs were isolated from different clinical samples of head and neck squamous cell carcinoma (HNSCC) patients, the level and cellular origins of PD-L1-positive sEVs were assessed. Co-expression of CD80 on PD-L1-positive sEVs was examined to evaluate the immunosuppressive and tumor-promotive effects.

RESULTS

PD-L1-positive sEVs in HNSCC patients had various cellular origins, including tumor cell, T cell, B cell, dendritic cell and monocyte/macrophage. However, PD-L1-positive sEVs derived from immune cells did not exert immunosuppressive functions due to the co-expression of CD80. It was verified that co-expression of CD80 disrupted the binding of sEV PD-L1 to its receptor PD-1 on T cells and attenuated the immunosuppression mediated by sEV PD-L1 both in vitro and in vivo.

CONCLUSION

The study suggests that PD-L1-positive sEVs have the cellular origin and functional heterogeneity. Co-expression of CD80 could restrict the immunosuppressive effect of sEV PD-L1. A greater understanding of PD-L1-positive sEV subsets is required to further improve their clinical application.

Immune capture and protein profiling of small extracellular vesicles from human plasma

Extracellular vesicles (EVs), the key players in inter-cellular communication, are produced by all cell types and are present in all body fluids. Analysis of the proteome content is an important approach in structural and functional studies of these vesicles. EVs circulating in human plasma are heterogeneous in size, cellular origin, and functions. This heterogeneity and the potential presence of contamination with plasma components such as lipoprotein particles and soluble plasma proteins represent a challenge in profiling the proteome of EV subsets by mass spectrometry. An immunocapture strategy prior to mass spectrometry may be used to isolate a homogeneous subpopulation of small EVs (sEV) with a specific endocytic origin from plasma or other biofluids. Immunocapture selectively separates EV subpopulations in biofluids based on the presence of a unique protein carried on the vesicle surface. The advantages and disadvantages of EV immune capture as a preparative step for mass spectrometry are discussed.

Tumor-Derived Exosomes and the Role of Liquid Biopsy in Human Papillomavirus Oropharyngeal Squamous Cell Carcinoma

ABSTRACT

The global incidence of human papillomavirus-positive (HPV+) head and neck squamous cell carcinoma (HNSCC) has surged in recent decades, with HPV+ HNSCC accounting for >70% of oropharynx cancers in the United States. Its incidence in men has surpassed that of HPV+ cervical cancer in women, and reliable assays are needed for early detection and to monitor response to therapy. Human papillomavirus-positive OPSCC has a more favorable response to therapy and prognosis than HPV-negative (HPV-) HNSCC, motivating regimens to deintensify curative surgery or chemoradiotherapy protocols. A barrier to deintensifying and personalizing therapy is lack of reliable predictive biomarkers. Furthermore, HPV- HNSCC survival rates are static without reliable surveillance biomarkers available. The emergence of circulating plasma-based biomarkers reflecting the tumor-immune microenvironment heralds a new era in HNSCC diagnosis and therapy. We review evidence on tumor-derived extracellular vesicles (exosomes) as biomarkers for diagnosis, prognostication, and treatment in HPV+ and HPV- HNSCC.

Plasma-derived small extracellular vesicles unleash the angiogenic potential in head and neck cancer patients

BACKGROUND

In Head and neck cancer (HNC) angiogenesis is essential for tumor progression and metastasis. Small extracellular vesicles (sEVs) from HNC cell lines alter endothelial cell (EC) functions towards a pro-angiogenic phenotype. However, the role of plasma sEVs retrieved from HNC patients in this process is not clear so far.

METHODS

Plasma sEVs were isolated on size exclusion chromatography columns from 32 HNC patients (early-stage UICC I/II: 8, advanced-stage UICC III/IV: 24), 12 patients with no evident disease after therapy (NED) and 16 healthy donors (HD). Briefly, sEVs were characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), BCA protein assays and Western blots. Levels of angiogenesis-associated proteins were determined using antibody arrays. The interaction of fluorescently-labeled sEVs with human umbilical vein ECs was visualized by confocal microscopy. The functional effect of sEVs on tubulogenesis, migration, proliferation and apoptosis of ECs was assessed.

RESULTS

The internalization of sEVs by ECs was visualized using confocal microscopy. Based on antibody arrays, all plasma sEVs were enriched in anti-angiogenic proteins. HNC sEVs contained more pro-angiogenic MMP-9 and anti-angiogenic proteins (Serpin F1) than HD sEVs. Interestingly, a strong inhibition of EC function was observed for sEVs from early-stage HNC, NED and HD. In contrast, sEVs from advanced-stage HNC showed a significantly increased tubulogenesis, migration and proliferation and induced less apoptosis in ECs than sEVs from HD.

CONCLUSIONS

In general, plasma sEVs carry a predominantly anti-angiogenic protein cargo and suppress the angiogenic properties of ECs, while sEVs from (advanced-stage) HNC patients induce angiogenesis compared to HD sEVs. Thus, tumor-derived sEVs within the plasma of HNC patients might shift the angiogenic switch towards angiogenesis.

Exosome-Based Liquid Biopsy Approaches in Bone and Soft Tissue Sarcomas: Review of the Literature, Prospectives, and Hopes for Clinical Application

The knowledge of exosome impact on sarcoma development and progression has been implemented in preclinical studies thanks to technological advances in exosome isolation. Moreover, the clinical relevance of liquid biopsy is well established in early diagnosis, prognosis prediction, tumor burden assessment, therapeutic responsiveness, and recurrence monitoring of tumors. In this review, we aimed to comprehensively summarize the existing literature pointing out the clinical relevance of detecting exosomes in liquid biopsy from sarcoma patients. Presently, the clinical utility of liquid biopsy based on exosomes in patients affected by sarcoma is under debate. The present manuscript collects evidence on the clinical impact of exosome detection in circulation of sarcoma patients. The majority of these data are not conclusive and the relevance of liquid biopsy-based approaches in some types of sarcoma is still insufficient. Nevertheless, the utility of circulating exosomes in precision medicine clearly emerged and further validation in larger and homogeneous cohorts of sarcoma patients is clearly needed, requiring collaborative projects between clinicians and translational researchers for these rare cancers.

Evaluating tumor cell- and T cell-derived extracellular vesicles as potential biomarkers of cancer and immune cell competence

INTRODUCTION

Extracellular vesicles (EVs) produced by tumors, also called tumor-derived exosomes (TEX), have been implicated in inducing immune cell suppression in vitro and in vivo. The development of a novel category of noninvasive biomarkers for precision oncology remains an unmet need, and TEX emerge as a promising liquid tumor biopsy component.

AREAS COVERED

TEX play a critical role in monitoring cancer presence/progression and in reprograming of anti-tumor effector T cells to producers of EVs with pro-tumor activity. TEX are a subset of circulating EVs. Their separation by immune capture from EVs derived from nonmalignant cells allows for TEX phenotypic/functional assessments. TEX cross-talking with CD3(+) T cells induce the release of CD3(+) small EV (sEV), whose cargo of suppressor proteins resembles that of TEX and further contributes to cancer-induced immune suppression. While TEX recapitulate the genetic/molecular phenotype of tumor cells, CD3(+) sEV might serve as 'T cell liquid biopsy.'

EXPERT OPINION

Preclinical explorations of the role in cancer body fluids of TEX and CD3(+) sEV as cancer biomarkers suggest that these EV subsets may qualify as liquid tumor biopsy noninvasive components in the near future. Their potential to simultaneously serve as noninvasive liquid tumor biopsy and T cell biopsy remains to be validated in future clinical trials.

Tumor extracellular vesicles mediate anti-PD-L1 therapy resistance by decoying anti-PD-L1

PD-L1⁺ tumor-derived extracellular vesicles (TEVs) cause systemic immunosuppression and possibly resistance to anti-PD-L1 antibody (αPD-L1) blockade. However, whether and how PD-L1⁺ TEVs mediate αPD-L1 therapy resistance is unknown. Here, we show that PD-L1⁺ TEVs substantially decoy αPD-L1 and that TEV-bound αPD-L1 is more rapidly cleared by macrophages, causing insufficient blockade of tumor PD-L1 and subsequent αPD-L1 therapy resistance. Inhibition of endogenous production of TEVs by Rab27a or Coro1a knockout reverses αPD-L1 therapy resistance. Either an increased αPD-L1 dose or macrophage depletion mediated by the clinical drug pexidartinib abolishes αPD-L1 therapy resistance. Moreover, in the treatment cycle with the same total treatment dose of αPD-L1, high-dose and low-frequency treatment had better antitumor effects than low-dose and high-frequency treatment, induced stronger antitumor immune memory, and eliminated αPD-L1 therapy resistance. Notably, in humanized immune system mice with human xenograft tumors, both increased αPD-L1 dose and high-dose and low-frequency treatment enhanced the antitumor effects of αPD-L1. Furthermore, increased doses of αPD-L1 and αPD-1 had comparable antitumor effects, but αPD-L1 amplified fewer PD-1⁺ Treg cells, which are responsible for tumor hyperprogression. Altogether, our results reveal a TEV-mediated mechanism of αPD-L1-specific therapy resistance, thus providing promising strategies to improve αPD-L1 efficacy.

Prognostic value of PD-1, PD-L1 and PD-L2 deserves attention in head and neck cancer

Head and neck cancer has high heterogeneity with poor prognosis, and emerging researches have been focusing on the prognostic markers of head and neck cancer. PD-L1 expression is an important basis for strategies of immunosuppressive treatment, but whether it has prognostic value is still controversial. Although meta-analysis on PD-L1 expression versus head and neck cancer prognosis has been performed, the conclusions are controversial. Since PD-L1 and PD-L2 are two receptors for PD-1, here we summarize and analyze the different prognostic values of PD-1, PD-L1, and PD-L2 in head and neck cancer in the context of different cell types, tissue localization and protein forms. We propose that for head and neck cancer, the risk warning value of PD-1/PD-L1 expression in precancerous lesions is worthy of attention, and the prognostic value of PD-L1 expression at different subcellular levels as well as the judgment convenience of prognostic value of PD-1, PD-L1, PD-L2 should be fully considered. The PD-L1 evaluation systems established based on immune checkpoint inhibitors (ICIs) are not fully suitable for the evaluation of PD-L1 prognosis in head and neck cancer. It is necessary to establish a new PD-L1 evaluation system based on the prognosis for further explorations. The prognostic value of PD-L1, PD-L2 expression in head and neck cancer may be different for early-stage and late-stage samples, and further stratification is required.

Comparison of plasma- and saliva-derived exosomal miRNA profiles reveals diagnostic potential in head and neck cancer

Background: Head and neck squamous cell carcinomas (HNSCC) lack tumor-specific biomarkers. Exosomes from HNSCC patients carry immunomodulatory molecules, and correlate with clinical parameters. We compared miRNA profiles of plasma- and saliva-derived exosomes to reveal liquid biomarker candidates for HNSCC.

Methods: Exosomes were isolated by differential ultracentrifugation from corresponding plasma and saliva samples from 11 HNSCC patients and five healthy donors (HD). Exosomal miRNA profiles, as determined by nCounter^® SPRINT technology, were analyzed regarding their diagnostic and prognostic potential, correlated to clinical data and integrated into network analysis.

Results: 119 miRNAs overlapped between plasma- and saliva-derived exosomes of HNSCC patients, from which 29 tumor-exclusive miRNAs, associated with TP53, TGFB1, PRDM1, FOX O 1 and CDH1 signaling, were selected. By intra-correlation of tumor-exclusive miRNAs from plasma and saliva, top 10 miRNA candidates with the strongest correlation emerged as diagnostic panels to discriminate cancer and healthy as well as potentially prognostic panels for disease-free survival (DFS). Further, exosomal miRNAs were differentially represented in human papillomavirus (HPV) positive and negative as well as low and high stage disease.

Conclusion: A plasma- and a saliva-derived panel of tumor-exclusive exosomal miRNAs hold great potential as liquid biopsy for discrimination between cancer and healthy as well as HPV status and disease stage. Exosomal miRNAs from both biofluids represent a promising tool for future biomarker studies, emphasizing the possibility to substitute plasma by less-invasive saliva collection.

Emerging role of mesenchymal stromal cells (MSCs)-derived exosome in neurodegeneration-associated conditions: a groundbreaking cell-free approach

Accumulating proofs signify that pleiotropic effects of mesenchymal stromal cells (MSCs) are not allied to their differentiation competencies but rather are mediated mainly by the releases of soluble paracrine mediators, making them a reasonable therapeutic option to enable damaged tissue repair. Due to their unique immunomodulatory and regenerative attributes, the MSC-derived exosomes hold great potential to treat neurodegeneration-associated neurological diseases. Exosome treatment circumvents drawbacks regarding the direct administration of MSCs, such as tumor formation or reduced infiltration and migration to brain tissue. Noteworthy, MSCs-derived exosomes can cross the blood–brain barrier (BBB) and then efficiently deliver their cargo (e.g., protein, miRNAs, lipid, and mRNA) to damaged brain tissue. These biomolecules influence various biological processes (e.g., survival, proliferation, migration, etc.) in neurons, oligodendrocytes, and astrocytes. Various studies have shown that the systemic or local administration of MSCs-derived exosome could lead to the favored outcome in animals with neurodegeneration-associated disease mainly by supporting BBB integrity, eliciting pro-angiogenic effects, attenuating neuroinflammation, and promoting neurogenesis in vivo. In the present review, we will deliver an overview of the therapeutic benefits of MSCs-derived exosome therapy to ameliorate the pathological symptoms of acute and chronic neurodegenerative disease. Also, the underlying mechanism behind these favored effects has been elucidated.

Cargo and Functional Profile of Saliva-Derived Exosomes Reveal Biomarkers Specific for Head and Neck Cancer

Background

Exosomes contribute to immunosuppression in head and neck squamous cell carcinoma (HNSCC), a tumor entity which lacks specific tumor biomarkers. Plasma-derived exosomes from HNSCC patients correlate with clinical parameters and have potential as liquid biopsy. Here, we investigate the cargo and functional profile of saliva-derived exosomes from HNSCC patients and their potential as non-invasive biomarkers for disease detection and immunomodulation.

Methods

Exosomes were isolated from saliva of HNSCC patients (n = 21) and healthy donors (HD, n = 12) by differential ultracentrifugation. Surface values of immune checkpoints and tumor associated antigens on saliva-derived exosomes were analyzed by bead-based flow cytometry using CD63 capture. Upon co-incubation with saliva-derived exosomes, activity and proliferation of T cells were assessed by flow cytometry (CD69 expression, CFSE assay). Adenosine levels were measured by mass spectrometry after incubation of saliva-derived exosomes with exogenous ATP. miRNA profiling of saliva-derived exosomes was performed using the nCounter^® SPRINT system.

Results

Saliva-derived, CD63-captured exosomes from HNSCC patients carried high amounts of CD44v3, PDL1 and CD39. Compared to plasma, saliva was rich in tumor-derived, CD44v3⁺ exosomes and poor in hematopoietic cell-derived, CD45⁺ exosomes. CD8⁺ T cell activity was attenuated by saliva-derived exosomes from HNSCC patients, while proliferation of CD4⁺ T cells was not affected. Further, saliva-derived exosomes produced high levels of immunosuppressive adenosine. 62 HD- and 31 HNSCC-exclusive miRNAs were identified. Samples were grouped in "Healthy" and "Cancer" based on their saliva-derived exosomal miRNA profile, which was further found to be involved in RAS/MAPK, NF-κB complex, Smad2/3, and IFN-α signaling.

Conclusions

Saliva-derived exosomes from HNSCC patients were enriched in tumor-derived exosomes whose cargo and functional profile reflected an immunosuppressive TME. Surface values of CD44v3, PDL1 and CD39 on CD63-captured exosomes, adenosine production and the miRNA cargo of saliva-derived exosomes emerged as discriminators of disease and emphasized their potential as liquid biomarkers specific for HNSCC.

Small extracellular vesicle PD-L1 in cancer: the knowns and unknowns

According to the conventional wisdom, programmed death protein 1 ligand (PD-L1)-mediated immunosuppression was based on the physical contact between tumor cells and T cells in the tumor microenvironment. Recent studies demonstrated that PD-L1 was also highly expressed on the surface of tumor cell-derived small extracellular vesicles (sEVs). PD-L1 on sEVs, which could also directly bind to PD-1 on T cells, has a vital function in immunosuppression and immunotherapy resistance. Due to the heterogeneity and dynamic changes of PD-L1 expression on tumor cells, developing sEV PD-L1 as a predictive biomarker for the clinical responses to immunotherapy could be an attractive option. In this review, we summarized and discussed the latest researches and advancements on sEV PD-L1, including the biogenesis and secretion mechanisms, isolation and detection strategies, as well as the biological functions of sEV PD-L1. In the meantime, we highlighted the application potential of sEV PD-L1 as diagnostic and prognostic markers in tumor, especially for predicting the clinical responses to anti-PD-1/PD-L1 immunotherapies. In particular, with the gradual deepening of the studies, challenges and problems regarding the further understanding and application of sEV PD-L1 have begun to emerge. Based on the current research status, we summarized the potential challenges and possible solutions, and prospected several key directions for future studies of sEV PD-L1. Collectively, by highlighting the important knowns and unknowns of sEV PD-L1, our present review would help to light the way forward for the field of sEV PD-L1 and to avoid unnecessary blindness and detours.

Proteomic and Metabolomic Profiles of T Cell-Derived Exosomes Isolated from Human Plasma

Exosomes that are released by T cells are key messengers involved in immune regulation. However, the molecular profiling of these vesicles, which is necessary for understanding their functions, requires their isolation from a very heterogeneous mixture of extracellular vesicles that are present in the human plasma. It has been shown that exosomes that are produced by T cells could be isolated from plasma by immune capture using antibodies that target the CD3 antigen, which is a key component of the TCR complex that is present in all T lymphocytes. Here, we demonstrate that CD3(+) exosomes that are isolated from plasma can be used for high-throughput molecular profiling using proteomics and metabolomics tools. This profiling allowed for the identification of proteins and metabolites that differentiated the CD3(+) from the CD3(-) exosome fractions that were present in the plasma of healthy donors. Importantly, the proteins and metabolites that accumulated in the CD3(+) vesicles reflected the known molecular features of T lymphocytes. Hence, CD3(+) exosomes that are isolated from human plasma by immune capture could serve as a "T cell biopsy".

Exosomes: Potential Biomarkers and Functions in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC), originating from the mucosal epithelial cells of the oral cavity, pharynx, and larynx, is a lethal malignancy of the head and neck. Patients with advanced and recurrent HNSCC have poor outcomes due to limited therapeutic options. Exosomes have active roles in the pathophysiology of tumors and are suggested as a potential therapeutic target of HNSCC. Exosomes in HNSCC have been intensively studied for disease activity, tumor staging, immunosuppression, and therapeutic monitoring. In this review, the biological mechanisms and the recent clinical application of exosomes are highlighted to reveal the potential of exosomes as biomarkers and therapeutic targets for HNSCC.

Plasma-Enabled Smart Nanoexosome Platform as Emerging Immunopathogenesis for Clinical Viral Infection

Smart nanoexosomes are nanosized structures enclosed in lipid bilayers that are structurally similar to the viruses released by a variety of cells, including the cells lining the respiratory system. Of particular importance, the interaction between smart nanoexosomes and viruses can be used to develop antiviral drugs and vaccines. It is possible that nanoexosomes will be utilized and antibodies will be acquired more successfully for the transmission of an immune response if reconvalescent plasma (CP) is used instead of reconvalescent plasma exosomes (CPExo) in this concept. Convalescent plasma contains billions of smart nanoexosomes capable of transporting a variety of molecules, including proteins, lipids, RNA and DNA among other viral infections. Smart nanoexosomes are released from virus-infected cells and play an important role in mediating communication between infected and uninfected cells. Infections use the formation, production and release of smart nanoexosomes to enhance the infection, transmission and intercellular diffusion of viruses. Cell-free smart nanoexosomes produced by mesenchymal stem cells (MSCs) could also be used as cell-free therapies in certain cases. Smart nanoexosomes produced by mesenchymal stem cells can also promote mitochondrial function and heal lung injury. They can reduce cytokine storms and restore the suppression of host antiviral defenses weakened by viral infections. This study examines the benefits of smart nanoexosomes and their roles in viral transmission, infection, treatment, drug delivery and clinical applications. We also explore some potential future applications for smart nanoexosomes in the treatment of viral infections.

Serum exosomal proteomics analysis of lung adenocarcinoma to discover new tumor markers

BACKGROUND

Among the most aggressive and rapidly lethal types of lung cancer, lung adenocarcinoma is the most common type. Exosomes, as a hot area, play an influential role in cancer. By using proteomics analysis, we aimed to identify potential markers of lung adenocarcinoma in serum.

METHODS

In our study, we used the ultracentrifugation method to isolate serum exosomes. The Liquid chromatography-mass spectrometry (LC-MS) and bioinformatics analysis were used to identify potential serum exosomal proteins with altered expression among patients with advanced lung adenocarcinoma, early lung adenocarcinoma, and healthy controls. A western blot (WB) was performed to confirm the above differential expression levels in a separate serum sample-isolated exosome, and immunohistochemistry (IHC) staining was conducted to detect expression levels of the above differential proteins of serum exosomes in lung adenocarcinoma tissues and adjacent tissues. Furthermore, we compared different expression models of the above differential proteins in serum and exosomes.

RESULT

According to the ITGAM (Integrin alpha M chain) and CLU (Clusterin) were differentially expressed in serum exosomes among different groups as well as tumor tissues and adjacent tissues. ITGAM was significantly and specifically enriched in exosomes. As compared to serum, CLU did not appear to be significantly enriched in exosomes. ITGAM and CLU were identified as serum exosomal protein markers of lung adenocarcinoma.

CONCLUSIONS

This study can provide novel ideas and a research basis for targeting lung adenocarcinoma treatment as a preliminary study.

Evaluation of Immunoregulatory Biomarkers on Plasma Small Extracellular Vesicles for Disease Progression and Early Therapeutic Response in Head and Neck Cancer

Head and Neck Cancers (HNCs) have highly immunosuppressive properties. Small extracellular vesicles (sEVs), including exosomes, nanosized mediators of intercellular communication in the blood, carry immunosuppressive proteins and effectively inhibit anti-tumor immune responses in HNCs. This study evaluates immunosuppressive markers on sEVs from 40 HNC patients at different disease stages and 3- and 6-month follow-up after surgery and/or chemoradiotherapy. As controls, sEVs from normal donors (NDs) are examined. Immunoregulatory surface markers on sEVs were detected as relative fluorescence intensity (RFI) using on-bead flow cytometry, and their expression levels were monitored in the early and late stages of HNC and during follow-up. In parallel, the sEV-mediated apoptosis of CD8⁺ Jurkat cells was assessed. Together with TGF-β1 and PD-L1 abundance, total sEV proteins are elevated with disease progression. In contrast, total sEV protein, including TGF-β1, PD-1 and PD-L1, decrease upon therapy response during follow-up. Overall survival analysis implies that high sEV PD-1/PD-L1 content is an unfavorable prognostic marker in HNC. Consistently, the sEV-mediated induction of apoptosis in CD8⁺ T cells correlates with the disease activity and therapy response. These findings indicate that a combination of immunoregulatory marker profiles should be preferred over a single marker to monitor disease progression and therapy response in HNC.

Development of an exosomal gene signature to detect residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning

Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal messenger RNAs (mRNAs). The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by real-time quantitative reverse transcription PCR (qRT-PCR), while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups ("healthy", "osteosarcoma", "other bone tumor", or "non-neoplastic disease"). Pre-treatment samples from osteosarcoma cases were used as the training set, and a validation set from post-treatment samples was used for testing, classifying as "osteosarcoma detected" or "osteosarcoma-NOT detected". Dogs in a validation set whose post-treatment samples were classified as "osteosarcoma-NOT detected" had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof of concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.

Tumor-derived exosomal PD-L1 in progression of cancer and immunotherapy

Cancer is a gravely important health issue all over the world and has been spreading fast. In recent years immune checkpoint treatment options have been used extensively as a primary line of treatment for different cancer types. PD-1 and its ligand, PD-L1, are members of the immune-checkpoints superfamily. Anti-PD-L1 and anti-PD-1 antibodies have shown efficacy against different cancer types, but fewer than 30% of patients have shown robust therapeutic responses and, therefore, it is hypothesized that exosomal PD-L1 is the mechanism to blame for failure in primary immune checkpoint therapy. The identical membrane topology of exosomal PD-L1 with tumor cell membrane-type provides the possibility to mimic immunosuppressive effects of tumor cell membrane PD-L1. In this review, it is discussed whether exosomal PD-L1 binds to antibodies and hence resistance to immunotherapy will be developed, and targeting exosome biogenesis inhibition can provide a new strategy to overcome tumor resistance to anti-PD-L1 therapy. Diagnostic and prognostic values of exosomal PD-L1 in different cancer types are discussed. Multiple clinical studies conclude that the level of tumor-derived exosomes (TEXs) as a biomarker for diagnosis could distinguish cancer patients from healthy controls. Elevated exosomal PD-L1 levels may be predictive of advanced disease stages, cancer metastasis, lower response to anti-PD-1/PD-L1 therapy, lower overall survival rates, and poor tumor prognosis. These novel findings of TEXs serve as promising therapeutic targets for early diagnosis and prevention of cancer progression.

The Hidden Link of Exosomes to Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) represents an aggressive and heterogenous group of cancers whose pathologies remain largely unresolved. Despite recent advances in HNSCC therapeutic strategies, the overall survival of HNSCC patients remains poor and continues to prompt efforts to develop more effective therapies. Exosomes are a subtype of extracellular vesicles secreted by a variety of cells that have begun to spark significant interest in their roles in cancer. As membranous vesicles, spanning from 30-150 nm in diameter, exosomes mediate the transport of various molecules, such as proteins, nucleic acids, and lipids, intercellularly throughout the body. In doing so, exosomes not only act to deliver materials to cancer cells but also as signals that can confer their progression. Accumulating evidence shows the direct correlation between exosomes and the aggressiveness of HNSCC. However, more research is warranted in this field to further our understanding. In this review, we attempt to highlight the tumor-supporting roles and therapeutic potential of exosomes in HNSCC. We introduce first the biogenesis and component features of exosomes, followed by their involvement in HNSCC proliferation and metastasis. We then move on to discuss HNSCC-derived exosomes' influence on the tumor microenvironment and their function in tumor drug resistance. Finally, we explore the promising potential of exosomes as HNSCC biomarkers and therapeutic targets and drug carriers for HNSCC treatments.

Changes in circulating exosome molecular profiles following surgery/(chemo)radiotherapy: early detection of response in head and neck cancer patients

BACKGROUND

Head and neck cancers (HNSCC) are highly immunosuppressive. Plasma-derived exosomes of HNSCC patients carry immunomodulatory molecules, and their cargo correlates with clinical parameters. Here, we evaluated the exosomal molecular profile for early detection of treatment failure in locally advanced HNSCC patients treated with conventional therapy.

METHODS

Plasma from 17 HNSCC patients was collected before, during, and after treatment by surgery with adjuvant (chemo)radiation and at recurrence. Exosomes were isolated by size-exclusion chromatography. Total exosomal protein (TEP) was used to estimate exosome load and on-bead flow cytometry to evaluate relative fluorescence intensity (RFI) of tumour-associated and immunoregulatory proteins on exosomes. Exosomal effects on the activity of and adenosine production by T cells was assessed by flow cytometry and mass spectrometry.

RESULTS

TEP and the ratio of tumour-/immune-cell-derived exosomes varied during and after therapy with an overall decrease in the tumour-free follow-up but an increase at recurrence. RFI values of immunoregulatory proteins on exosomes, their ability for T cell inhibition and adenosine production changed during and after therapy. PD-L1 was the earliest discriminator for treatment failure and disease-free survival.

CONCLUSIONS

Monitoring of plasma exosomes during therapy represents a promising opportunity for early detection of treatment failure and risk stratification to delay/avoid recurrence.

Extracellular Vesicles (Exosomes) as Immunosuppressive Mediating Variables in Tumor and Chronic Inflammatory Microenvironments

Exosomes are extracellular vesicles released by most of the eukaryotic cells. Exosomes’ components include proteins, lipids, microRNA, circular RNA, long noncoding RNA, DNA, etc. Exosomes may carry both pro and anti-inflammatory cargos; however, exosomes are predominantly filled with immunosuppressive cargos such as enzymes and microRNAs in chronic inflammation. Exosomes have surfaced as essential participants in physiological and pathological intercellular communication. Exosomes may prevent or promote the formation of an aggressive tumor and chronic inflammatory microenvironments, thus influencing tumor and chronic inflammatory progression as well as clinical prognosis. Exosomes, which transmit many signals that may either enhance or constrain immunosuppression of lymphoid and myeloid cell populations in tumors, are increasingly becoming recognized as significant mediators of immune regulation in cancer. In this review, we outline the function of exosomes as mediators of immunosuppression in tumor and chronic inflammatory microenvironments, with the aim to improve cancer therapy.

Tumor-Derived Exosomes: Hidden Players in PD-1/PD-L1 Resistance

Simple Summary

Immunotherapies such as anti-PD-1/PD-L1 have garnered increasing importance in cancer therapy, leading to substantial improvements in patient care and survival. However, a certain proportion of patients present tumors that resist these treatments. Exosomes, small vesicles secreted by almost every cell, including tumor cells, have proven to be key actors in this resistance. In this review, we describe the involvement of immune checkpoints and immune modulators in tumor-derived exosomes (TEXs) in the context of cancer. We will focus on the most promising proteins under scrutiny for use in combination with PD-1 blockade therapy in a clinical setting: PD-L1, CTLA-4, TIM-3, CD73/39, LAG-3, and TIGIT. Finally, we will discuss how they can change the game in immunotherapy, notably through their role in immunoresistance and how they can guide therapeutic decisions, as well as the current obstacles in the field.

Abstract

Recently, immunotherapy has garnered increasing importance in cancer therapy, leading to substantial improvements in patient care and survival. By blocking the immune checkpoints—protein regulators of the immune system—immunotherapy prevents immune tolerance toward tumors and reactivates the immune system, prompting it to fight cancer cell growth and diffusion. A widespread strategy for this is the blockade of the interaction between PD-L1 and PD-1. However, while patients generally respond well to immunotherapy, a certain proportion of patients present tumors that resist these treatments. This portion can be very high in some cancers and hinders cancer curability. For this reason, current efforts are focusing on combining PD-1/PD-L1 immunotherapy with the targeting of other immune checkpoints to counter resistance and achieve better results. Exosomes, small vesicles secreted by almost any cell, including tumor cells, have proven to be key actors in this resistance. The exosomes released by tumor cells spread the immune-suppressive properties of the tumor throughout the tumor microenvironment and participate in establishing metastatic niches. In this review, we will describe immune checkpoints and immune modulators whose presence in tumor-derived exosomes (TEXs) has been established. We will focus on the most promising proteins under scrutiny for use in combination with PD-1 blockade therapy in a clinical setting, such as PD-L1, CTLA-4, TIM-3, CD73/39, LAG-3, and TIGIT. We will explore the immunosuppressive impact of these exosomal proteins on a variety of immune cells. Finally, we will discuss how they can change the game in immunotherapy and guide therapeutic decisions, as well as the current limits of this approach. Depending on the viewpoint, these exosomal proteins may either provide key missing information on tumor growth and resistance mechanisms or they may be the next big challenge to overcome in improving cancer treatment.

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.

Exosomes in Lung Cancer: Actors and Heralds of Tumor Development

Lung cancer is a leading cause of cancer-related death worldwide and in most cases, diagnosis is reached when the tumor has already spread and prognosis is quite poor. For that reason, the research for new biomarkers that could improve early diagnosis and its management is essential. Exosomes are microvesicles actively secreted by cells, especially by tumor cells, hauling molecules that mimic molecules of the producing cells. There are multiple methods for exosome isolation and analysis, although not standardized, and cancer exosomes from biological fluids are especially difficult to study. Exosomes' cargo proteins, RNA, and DNA participate in the communication between cells, favoring lung cancer development by delivering signals for growth, metastasis, epithelial mesenchymal transition, angiogenesis, immunosuppression and even drug resistance. Exosome analysis can be useful as a type of liquid biopsy in the diagnosis, prognosis and follow-up of lung cancer. In this review, we will discuss recent advances in the role of exosomes in lung cancer and their utility as liquid biopsy, with special attention to isolating methods.

Tumor-Derived Exosomes (TEX) and Their Role in Immuno-Oncology

Extracellular vesicles (EVs) play a key role in health and disease, including cancer. Tumors produce a mix of EVs differing in size, cellular origin, biogenesis and molecular content. Small EVs (sEV) or exosomes are a subset of 30-150 nm (virus-size) vesicles originating from the multivesicular bodies (MVBs) and carrying a cargo that in its content and topography approximates that of a parent cell. Tumor-derived exosomes (TEX) present in all body fluids of cancer patients, are considered promising candidates for a liquid tumor biopsy. TEX also mediate immunoregulatory activities: they maintain a crosstalk between the tumor and various non-malignant cells, including immunocytes. Effects that EVs exert on immune cells may be immunosuppressive or immunostimulatory. Here, we review the available data for TEX interactions with immunocytes, focusing on strategies that allow isolation from plasma and separation of TEX from sEV produced by non-malignant cells. Immune effects mediated by either of the subsets can now be distinguished and measured. The approach has allowed for the comparison of molecular and functional profiles of the two sEV fractions in plasma of cancer patients. While TEX carried an excess of immunosuppressive proteins and inhibited immune cell functions in vitro and in vivo, the sEV derived from non-malignant cells, including CD3(+)T cells, were variably enriched in immunostimulatory proteins and could promote functions of immunocytes. Thus, sEV in plasma of cancer patients are heterogenous, representing a complex molecular network which is not evident in healthy donors' plasma. Importantly, TEX appear to be able to reprogram functions of non-malignant CD3(+)T cells inducing them to produce CD3(+)sEV enriched in immunosuppressive proteins. Ratios of stimulatory/inhibitory proteins carried by TEX and by CD3(+)sEV derived from reprogrammed non-malignant cells vary broadly in patients and appear to negatively correlate with disease progression. Simultaneous capture from plasma and functional/molecular profiling of TEX and the CD3(+)sEV fractions allows for defining their role as cancer biomarkers and as monitors of cancer patients' immune competence, respectively.

Extracellular Vesicle Capture by AnTibody of CHoice and Enzymatic Release (EV-CATCHER): A customizable purification assay designed for small-RNA biomarker identification and evaluation of circulating small-EVs

Circulating nucleic acids, encapsulated within small extracellular vesicles (EVs), provide a remote cellular snapshot of biomarkers derived from diseased tissues, however selective isolation is critical. Current laboratory-based purification techniques rely on the physical properties of small-EVs rather than their inherited cellular fingerprints. We established a highly-selective purification assay, termed EV-CATCHER, initially designed for high-throughput analysis of low-abundance small-RNA cargos by next-generation sequencing. We demonstrated its selectivity by specifically isolating and sequencing small-RNAs from mouse small-EVs spiked into human plasma. Western blotting, nanoparticle tracking, and transmission electron microscopy were used to validate and quantify the capture and release of intact small-EVs. As proof-of-principle for sensitive detection of circulating miRNAs, we compared small-RNA sequencing data from a subset of small-EVs serum-purified with EV-CATCHER to data from whole serum, using samples from a small cohort of recently hospitalized Covid-19 patients. We identified and validated, only in small-EVs, hsa-miR-146a and hsa-miR-126-3p to be significantly downregulated with disease severity. Separately, using convalescent sera from recovered Covid-19 patients with high anti-spike IgG titers, we confirmed the neutralizing properties, against SARS-CoV-2 in vitro, of a subset of small-EVs serum-purified by EV-CATCHER, as initially observed with ultracentrifuged small-EVs. Altogether our data highlight the sensitivity and versatility of EV-CATCHER.

Serum Exosomes and Their miRNA Load-A Potential Biomarker of Lung Cancer

Early detection of lung cancer in screening programs is a rational way to reduce mortality associated with this malignancy. Low-dose computed tomography, a diagnostic tool used in lung cancer screening, generates a relatively large number of false-positive results, and its complementation with molecular biomarkers would greatly improve the effectiveness of such programs. Several biomarkers of lung cancer based on different components of blood, including miRNA signatures, were proposed. However, only a few of them have been positively validated in the context of early cancer detection yet, which imposes a constant need for new biomarker candidates. An emerging source of cancer biomarkers are exosomes and other types of extracellular vesicles circulating in body fluids. Hence, different molecular components of serum/plasma-derived exosomes were tested and showed different levels in lung cancer patients and healthy individuals. Several studies focused on the miRNA component of these vesicles. Proposed signatures of exosome miRNA had promising diagnostic value, though none of them have yet been clinically validated. These signatures involved a few dozen miRNA species overall, including a few species that recurred in different signatures. It is worth noting that all these miRNA species have cancer-related functions and have been associated with lung cancer progression. Moreover, a few of them, including known oncomirs miR-17, miR-19, miR-21, and miR-221, appeared in multiple miRNA signatures of lung cancer based on both the whole serum/plasma and serum/plasma-derived exosomes.

Exosomes in Immune Regulation

Exosomes, small extracellular vesicles mediate intercellular communication by transferring their cargo including DNA, RNA, proteins and lipids from cell to cell. Notably, in the immune system, they have protective functions. However in cancer, exosomes acquire new, immunosuppressive properties that cause the dysregulation of immune cells and immune escape of tumor cells supporting cancer progression and metastasis. Therefore, current investigations focus on the regulation of exosome levels for immunotherapeutic interventions. In this review, we discuss the role of exosomes in immunomodulation of lymphoid and myeloid cells, and their use as immune stimulatory agents to elicit specific cytotoxic responses against the tumor.

Subpopulations of exosomes purified via different exosomal markers carry different microRNA contents

The heterogeneity of exosome populations presents a great challenge to their study. The current study was designed to investigate the potential heterogeneity miRNA contents in circulating exosomes purified via different exosomal markers. In this study, exosomes from the serum of C57BL/6 mice after cecum ligation and perforation (CLP) or sham operation were isolated by precipitation using ExoQuick-TC and affinity purified with anti-Rab5b, anti-CD9, anti-CD31, and anti-CD44 antibodies using the Exo-Flow Exosome Capture kit to collect exosome subpopulations. RNA extracted from the exosomes isolated by ExoQuick-TC were profiled by next-generation sequencing (NGS). Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) was also employed to determine the expression profiles of four representative exosomal miRNAs (mmu-miR-486-5p, mmu-miR-10a-5p, mmu-miR-143-3p, and mmu-miR-25-3p) selected from the NGS analysis. The results revealed that the expression patterns of these miRNAs in exosomes isolated by ExoQuick-TC as determined by RT-qPCR and NGS were similar, showing upregulation of mmu-miR-10a-5p and mmu-miR-143-3p but downregulation of mmu-miR-25-3p and mmu-miR-486-5p following CLP when compared to the levels in exosomes from sham control mice. However, their expression levels in the antibody-captured exosome subpopulations varied. The miRNAs in the exosomes captured by anti-Rab5b or anti-CD9 antibodies were more similar to those isolated by ExoQuick-TC than to those captured by anti-CD44 antibodies. However, there were no significant differences in these four miRNAs in CD31-captured exosomes. This study demonstrated that purification with different exosomal markers allows the collection of different exosome subpopulations with various miRNA contents. The results of this study demonstrate the heterogeneity of circulating exosomes and suggest the importance of stratifying exosome subpopulations when using circulating exosomes as biomarkers or investigating exosome function. In addition, this study also emphasized the necessity of using a consistent exosome marker across different samples as detecting biomarkers.

Immunoaffinity-Based Isolation of Melanoma Cell-Derived and T Cell-Derived Exosomes from Plasma of Melanoma Patients

Tumor-derived exosomes (TEX), a subset of small extracellular vesicles (EVs) which originate from the endocytic compartment of tumor cells, are emerging as key players in cancer progression. TEX circulate freely in patients' body fluids and transfer bioactive cargos from tumor to various recipient cells. The molecular cargo of melanoma cell-derived exosomes (MTEX) mimics that of the tumor, and MTEX serve as a liquid biopsy that provides potentially useful information for cancer diagnosis, prognosis, or responses to therapy. Plasma of melanoma patients contains a mix of MTEX and exosomes produced by nonmalignant cells (NMTEX). Isolation of these exosome subtypes from the bulk of plasma exosomes is necessary to evaluate contributions of each as potential biomarkers of melanoma progression and outcome. Here, methods for separation of MTEX from T cell-derived exosomes from a single small volume of plasma and their subsequent molecular and functional characterization are described. Following size exclusion chromatography (SEC) to isolate total plasma exosomes, immune affinity-based capture of MTEX with anti-CSPG4 antibody and then of exosomes produced by T cells with anti-CD3 antibody is used to sequentially isolate the two subsets. This immune capture method enables the recovery of MTEX and CD3+ exosomes in quantities sufficient both for molecular profiling by flow cytometry or western blotting and for functional analyses.

Tumor-derived exosomes in the PD-1/PD-L1 axis: Significant regulators as well as promising clinical targets

Programmed cell death-1 (PD-1) is a negative coreceptor mainly expressed on the surface of activated T cells. The binding of PD-1 to its ligand PD-L1 significantly induces non-reactivity of T cells to maintain the balance of autoimmunity and immune tolerance. It is reported that tumor cells highly express PD-L1 to restrict cellular immune response, which is one of the most important mechanisms for tumor to mediate immune escape. Cancer immunotherapy targeting PD-1/PD-L1 has achieved remarkable success so far. Tumor-derived exosomes (TEXs) are lipid bilayer vesicles released by tumor cells in an endosome-dependent manner, mediating communication between tumor cells and adjacent cells in the tumor microenvironment. Through signals transmitted by TEXs, tumor can alter the biological characteristics of these cells to promote tumor growth and metastasis. Recent studies have demonstrated that TEXs not only carry tumor-derived PD-L1, but are also closely related to PD-1/PD-L1 expression on target cells. The primary focus of this review will be on how TEXs regulate the PD-1/PD-L1 axis to promote tumor progression, and the promising clinical applications targeting TEXs and exosomal PD-L1.

Extracellular Vesicle Identification Using Label-Free Surface-Enhanced Raman Spectroscopy: Detection and Signal Analysis Strategies

Extracellular vesicles (EVs) have been widely investigated as promising biomarkers for the liquid biopsy of diseases, owing to their countless roles in biological systems. Furthermore, with the notable progress of exosome research, the use of label-free surface-enhanced Raman spectroscopy (SERS) to identify and distinguish disease-related EVs has emerged. Even in the absence of specific markers for disease-related EVs, label-free SERS enables the identification of unique patterns of disease-related EVs through their molecular fingerprints. In this review, we describe label-free SERS approaches for disease-related EV pattern identification in terms of substrate design and signal analysis strategies. We first describe the general characteristics of EVs and their SERS signals. We then present recent works on applied plasmonic nanostructures to sensitively detect EVs and notable methods to interpret complex spectral data. This review also discusses current challenges and future prospects of label-free SERS-based disease-related EV pattern identification.

Role of exosome in autoimmunity, with a particular emphasis on rheumatoid arthritis

Cell-derived exosomes are identified as carriers of lipids, proteins, and genetic materials that participate in cell-cell signal communication, biological process, and cell signaling. Also, their involvement has been reported in a vast array of disorders and inflammatory conditions such as autoimmune diseases. Rheumatoid arthritis (RA), a common cause of joint disorder, is an inflammation-based disease in which the precise understanding of its pathogenesis needs to be further investigated. Also, there is only a palliative care approach for the alleviation of RA symptoms. This paper discusses the recent advances in the biology of exosomes in autoimmune disorders especially in RA, and also provides a new line of research for arthritis therapy using exosomes.

Blood-based PD-L1 analysis in tumor-derived extracellular vesicles: Applications for optimal use of anti-PD-1/PD-L1 axis inhibitors

Monoclonal antibodies that inhibit the programmed cell death protein 1 axis (anti-PD-1/PD-L1) are part of a new pharmacological strategy aimed at reinforcing the immune response to cancer. Despite the success in several cancer types, a significant percentage of patients do not benefit from treatment with these drugs due to intrinsic or acquired resistance or the occurrence of immune-related adverse reactions. Assessment of PD-L1 expression in tumor tissues is currently used to predict drug response in the clinics; however, there is a growing interest in identifying blood-based biomarkers that, owing to the minimally-invasive nature, can allow a dynamic monitoring of drug response in daily clinical practice. In the current review article, we discuss whether the assessment of PD-L1 mRNA and protein levels in circulating extracellular vesicles may have the potential to predict the likelihood of tumor response to anti-PD-1/PD-L1 antibodies.

Size-Exclusion Chromatography as a Technique for the Investigation of Novel Extracellular Vesicles in Cancer

Simple Summary

Extracellular vesicles (EVs) are small particles that are released by cancer cells, and they may hold vital information for researchers looking for early markers for diagnosis. Size-exclusion chromatography (SEC) is a classical technique that has become increasingly popular and can be used for rapid isolation and investigation of both their cargo and functionality. This systematic review highlights its main technical aspects, the type of materials involved and by covering the findings of the identified papers hopes to demonstrate the utility of this method in cancer research to date.

Abstract

Cancer cells release extracellular vesicles, which are a rich target for biomarker discovery and provide a promising mechanism for liquid biopsy. Size-exclusion chromatography (SEC) is an increasingly popular technique, which has been rediscovered for the purposes of extracellular vesicle (EV) isolation and purification from diverse biofluids. A systematic review was undertaken to identify all papers that described size exclusion as their primary EV isolation method in cancer research. In all, 37 papers were identified and discussed, which showcases the breadth of applications in which EVs can be utilised, from proteomics, to RNA, and through to functionality. A range of different methods are highlighted, with Sepharose-based techniques predominating. EVs isolated using SEC are able to identify cancer cells, highlight active pathways in tumourigenesis, clinically distinguish cohorts, and remain functionally active for further experiments.

Extracellular vesicles in cancer progression: are they part of the problem or part of the solution?

Extracellular vesicles (EVs) are released especially by cancer cells. They modulate the tumor microenvironment by interacting with immune cells while carrying immunosuppressive or immunostimulatory molecules. In this review, we will explore some conflicting reports regarding the immunological outcomes of EVs in cancer progression, in which they might initiate an antitumor immune response or an immunosuppressive response. Concerning immunosuppression, the role of tumor-derived EVs' in the adenosinergic system is underexplored. The enhancement of adenosine (ADO) levels in the tumor microenvironment impairs T-cell function and cytokine release. However, some tumor-derived EVs may deliver immunostimulatory factors, promoting immunogenic activity, even with ADO production. The modulatory role of ADO over the tumor progression represents a piece in an intricate microenvironment with anti and pro tumoral seesaw-like mechanisms.

[Exosomes as immune regulators in head and neck cancer]

Exosomes, virus-sized nanovesicles, are utilized as messenger systems of our body to communicate with other body cells and regulate immune functions. Almost all cells produce exosomes and are able to interact with immune cells in the blood stream and peripheral body areas. Different markers on the surface of exosomes are necessary for immune cell adhesion and interaction. Furthermore, many types of exosome-immune cell interaction, such as surface receptor contact and phagocytosis, are known. As carriers of different cargos, exosomes affect different immune cell types in head and neck cancers: So far, T cells, natural killer cells, macrophages, and dendritic cells have been described in this context. For diagnostic purposes, a combined analysis of different parameters including protein amount, nucleic acid/protein expression, and the immunosuppressive impact of exosomes could empower exosomes as useful tools for evaluation of tumor promotion and progression in the future.

The Evolving Landscape of PD-1/PD-L1 Pathway in Head and Neck Cancer

Over the past 10 years, cancer immunotherapy has made significant progress in multiple cancer types and has been gradually been applied to clinical cancer care, in which the programmed cell death protein-1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway is one of the most attractive targets. Compared with traditional therapies, the emerging PD-1/PD-L1 blockade immunotherapy exhibited more satisfactory curative effects and lower toxicity for patients with advanced head and neck squamous cell carcinoma (HNSCC). This review analyzes the expression characteristics and clinical significance of PD-1/PD-L1 in HNSCC, the immunosuppressive roles of tumor cell and stromal cell expressing PD-1/PD-L1 in this disease, and presents the development landscape of PD-1/PD-L1 inhibitors, which may provide new curative alternatives for recurrent or metastatic HNSCC.

The potential role of tumor-derived exosomes in diagnosis, prognosis, and response to therapy in cancer

INTRODUCTION

Small extracellular vesicles (sEV) produced by tumors and called TEX mediate communication and regulate the tumor microenvironment. As a 'liquid tumor biopsy' and with the ability to induce pro-tumor reprogramming, TEX offer a promising approach to monitoring cancer progression or response to therapy.

AREAS COVERED

TEX isolation from body fluids and separation by immunoaffinity capture from other EVs enables TEX molecular and functional characterization in vitro and in vivo. TEX carry membrane-bound PD-L1 and a rich cargo of other proteins and nucleic acids that reflect the tumor content and activity. TEX transfer this cargo to recipient cells, activating various molecular pathways and inducing pro-tumor transcriptional changes. TEX may interfere with immune therapies, and TEX plasma levels correlate with patients' responses to therapy. TEX induce local and systemic alterations in immune cells which may have a prognostic value.

EXPERT OPINION

TEX have a special advantage as potential cancer biomarkers. Their cargo emerges as a correlate of developing or progressing malignant disease; their phenotype mimics that of the tumor; and their functional reprogramming of immune cells provides a reading of the patients' immune status prior and post immunotherapy. Validation of TEX and T-cell-derived sEV as cancer biomarkers is an impending future task.

Exosomal vesicles enhance immunosuppression in chronic inflammation: Impact in cellular senescence and the aging process

Exosomes represent an evolutionarily conserved signaling pathway which can act as an alarming mechanism in responses to diverse stresses, e.g. chronic inflammation activates the budding of exosomal vesicles in both immune and non-immune cells. Exosomes can contain both pro- and anti-inflammatory cargos but in chronic inflammation, exosomes mostly carry immunosuppressive cargos, e.g. enzymes and miRNAs. The aging process is associated with chronic low-grade inflammation and the accumulation of pro-inflammatory senescent cells into tissues. There is clear evidence that aging increases the number of exosomes in both the circulation and tissues. Especially, the secretion of immunosuppressive exosomes robustly increases from senescent cells. There are observations that the exosomes from senescent cells are involved in the expansion of senescence into neighbouring cells. Interestingly, the age-related exosomes contain immune suppressive cargos which enhance the immunosuppression within recipient immune cells, i.e. tissue-resident and recruited immune cells including M2 macrophages, myeloid-derived suppressor cells (MDSC), and regulatory T cells (Treg). It seems that increased immunosuppression with aging impairs the clearance of senescent cells and their accumulation within tissues augments the aging process.

Evaluation of Exosome Proteins by on-Bead Flow Cytometry

Exosomes, recently re-named "small extracellular vesicles" or "sEV," are emerging as an intercellular communication system. Quantification of the molecular cargo exosomes carry by on-bead flow cytometry is needed for defining their role in information transfer and in human disease. Exosomes (sEV) isolated from cell supernatants or plasma of cancer patients by size-exclusion chromatography were captured by biotinylated antibodies specific for antigens in the exosome cargo (e.g., tetraspanins) and placed on streptavidin-labeled beads. Detection was performed with pretitered fluorochrome-labeled antibodies of desired specificity. The data were acquired in a conventional cytometer, and molecules of equivalent soluble fluorochrome (MESF) beads were used to quantify the number of fluorescent molecules bound per bead. Isotype antibody controls were obligatory. The mean fluorescence intensity (MFI) value of each sample was converted into MESF units, and the separation index (SI), which quantifies separation of stained and isotype control beads, was determined. Various proteins identified by labeled antibodies were quantified on the surface of tumor cell-derived exosomes. To identify intravesicular cargo, such as cytokines or chemokines, exosomes were lysed with 0.3% Triton-100, and the proteins in lysates were loaded on aldehyde/sulfate latex beads for flow cytometry. Examples of quantitative surface and/or intravesicular on-bead flow cytometry for exosomes produced by various cells or present in body fluids of cancer patients are provided. On-bead flow cytometry standardized for use with conventional cytometers is a useful method for protein detection and quantitation in exosomes isolated from supernatants of cell lines or plasma of patients with cancer. © 2020 International Society for Advancement of Cytometry.

Ewing sarcoma family of tumors-derived small extracellular vesicle proteomics identify potential clinical biomarkers

PURPOSE

Ewing Sarcoma Family of Tumors (ESFT), the second most common pediatric osseous malignancy, are characterized by the pathognomonic chromosomal EWS-ETS translocation. Outside of tumor biopsy, no clinically relevant ESFT biomarkers exist. Additionally, tumor burden assessment at diagnosis, monitoring of disease responsiveness to therapy, and detection of disease recurrence are limited to radiographic imaging. To identify new, clinically relevant biomarkers we evaluated the proteome of a subset of ESFT-derived small extracellular vesicles (sEVs).

MATERIALS AND METHODS

We performed the first high quality proteomic study of ESFT-derived sEVs from 5 ESFT cell lines representing the most common EWS-ETS fusion types and identified 619 proteins composing the core ESFT sEV proteome. We compared these core proteins to databases of common plasma-based proteins and sEV-associated proteins found within healthy plasma to identify proteins unique or enriched within ESFT.

RESULTS

From these analyses, two membrane bound proteins with biomarker potential were selected, CD99/MIC2 and NGFR, to develop a liquid-based assay enriching of ESFT-associated sEVs and detection of sEV mRNA cargo (i.e., EWS-ETS transcripts). We employed this immuno-enrichment approach to diagnosis of ESFT utilizing plasma (250 μl) from both localized and metastatic ESFT pediatric patients and cancer-free controls, and showed significant diagnostic power [AUC = 0.92, p = 0.001 for sEV numeration, with a PPV = 1.00, 95% CI = (0.63, 1.00) and a NPV = 0.67, 95% CI = (0.30, 0.93)].

CONCLUSIONS

In this study, we demonstrate utilization of circulating ESFT-associated sEVs in pediatric patients as a source of minimally invasive diagnostic and potentially prognostic biomarkers.

Circulating Exosomes Inhibit B Cell Proliferation and Activity

(1) Background: Head and neck squamous cell carcinoma (HNSCC) is characterized by a distinctive suppression of the anti-tumor immunity, both locally in the tumor microenvironment (TME) and the periphery. Tumor-derived exosomes mediate this immune suppression by directly suppressing T effector function and by inducing differentiation of regulatory T cells. However, little is known about the effects of exosomes on B cells. (2) Methods: Peripheral B cells from healthy donors and HNSCC patients were isolated and checkpoint receptor expression was analyzed by flow cytometry. Circulating exosomes were isolated from the plasma of HNSCC patients (n = 21) and healthy individuals (n = 10) by mini size-exclusion chromatography. B cells from healthy individuals were co-cultured with isolated exosomes for up to 4 days. Proliferation, viability, surface expression of checkpoint receptors, and intracellular signaling were analyzed in B cells by flow cytometry. (3) Results: Expression of the checkpoint receptors PD-1 and LAG3 was increased on B cells from HNSCC patients. The protein concentration of circulating exosomes was increased in HNSCC patients as compared to healthy donors. Both exosomes from healthy individuals and HNSCC patients inhibited B cell proliferation and survival, in vitro. Surface expression of inhibitory and stimulatory checkpoint receptors on B cells was modulated in co-culture with exosomes. In addition, an inhibitory effect of exosomes on B cell receptor (BCR) signaling was demonstrated in B cells. (4) Conclusions: Plasma-derived exosomes show inhibitory effects on the function of healthy B cells. Interestingly, these inhibitory effects are similar between exosomes from healthy individuals and HNSCC patients, suggesting a physiological B cell inhibitory role of circulating exosomes.

Immune Suppressive Effects of Plasma-Derived Exosome Populations in Head and Neck Cancer

Plasma-derived exosomes of head and neck squamous cell carcinoma (HNSCC) patients carry inhibitory factors mediating immune suppression. Separation of tumor-derived exosomes (TEX) and non-TEX may assist in a better understanding of their respective parental cells. Here, we evaluate the impact of TEX or hematopoietic-derived exosomes on immune suppression. We evaluated apoptosis in CD8+ T cells, conversion of CD4+ T cells to regulatory T cells (T_reg), and adenosine production by TEX, non-TEX, or total exosomes. Exosome protein cargo was significantly higher in total and CD45(−) exosomes from high stage compared to low stage patients. Furthermore, total and CD45(−) exosomes of high stage patients induced more apoptosis in CD8+ T cells than their low stage counterparts. CD69 suppression, a marker of reduced CD8+ T cell activation, was only mediated by CD45(−) exosomes. All fractions induced T_reg differentiation, defined by CD39 expression, but only CD45(−) exosomes showed a stage-dependent conversion. CD45(−) exosomes produced higher adenosine concentrations than CD45(+) exosomes, concluding that adenosine production measured in total exosomes mainly derives from TEX. The presented results show significant induction of immune suppression by TEX in HNSCC. This immunosuppressive effect supports the potential role of exosomes as liquid biomarkers for disease stage and level of immune suppression.