Exosomes derived from hypoxic epithelial ovarian cancer cells deliver microRNAs to macrophages and elicit a tumor-promoted phenotype

Tumor-Associated Macrophages in Pancreatic Ductal Adenocarcinoma: Origin, Polarization, Function, and Reprogramming

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy. PDAC is only cured by surgical resection in its early stage, but there remains a relatively high possibility of recurrence. The development of PDAC is closely associated with the tumor microenvironment. Tumor-associated macrophages (TAMs) are one of the most abundant immune cell populations in the pancreatic tumor stroma. TAMs are inclined to M2 deviation in the tumor microenvironment, which promotes and supports tumor behaviors, including tumorigenesis, immune escape, metastasis, and chemotherapeutic resistance. Herein, we comprehensively reviewed the latest researches on the origin, polarization, functions, and reprogramming of TAMs in PDAC.

Fine-Tuning the Tumour Microenvironment: Current Perspectives on the Mechanisms of Tumour Immunosuppression

Immunotherapy has revolutionised the treatment of cancers by harnessing the power of the immune system to eradicate malignant tissue. However, it is well recognised that some cancers are highly resistant to these therapies, which is in part attributed to the immunosuppressive landscape of the tumour microenvironment (TME). The contexture of the TME is highly heterogeneous and contains a complex architecture of immune, stromal, vascular and tumour cells in addition to acellular components such as the extracellular matrix. While understanding the dynamics of the TME has been instrumental in predicting durable responses to immunotherapy and developing new treatment strategies, recent evidence challenges the fundamental paradigms of how tumours can effectively subvert immunosurveillance. Here, we discuss the various immunosuppressive features of the TME and how fine-tuning these mechanisms, rather than ablating them completely, may result in a more comprehensive and balanced anti-tumour response.

The Role of Exosomes in the Female Reproductive System and Breast Cancers

Exosomes are nanoscale extracellular vesicles released by nearly all cell types. Exosomes were originally considered as waste receptacles for discarding unwanted cellular products; however, these organelles are now considered to be important for cell communication by delivering biologically active molecules such as proteins, DNA, non-coding RNA and mRNA. Studies have revealed that exosomes are closely related to several diseases, especially cancers. Exosomes are indispensable for the emergence and progression of tumor. Here, we review the status of research on exosomes in the female reproductive system cancers and breast cancer, focusing on their biological roles in chemical resistance and immune responses, as well as their underlying applications in drug delivery and nanotherapy and as biological markers for tumor diagnosis.

Hypoxic exosomes orchestrate tumorigenesis: molecular mechanisms and therapeutic implications

The solid tumor microenvironment possesses a hypoxic condition, which promotes aggressiveness and resistance to therapies. Hypoxic tumor cells undergo broadly metabolic and molecular adaptations and communicate with surrounding cells to provide conditions promising for their homeostasis and metastasis. Extracellular vesicles such as exosomes originating from the endosomal pathway carry different types of biomolecules such as nucleic acids, proteins, and lipids; participate in cell-to-cell communication. The exposure of cancer cells to hypoxic conditions, not only, increases exosomes biogenesis and secretion but also alters exosomes cargo. Under the hypoxic condition, different signaling pathways such as HIFs, Rab-GTPases, NF-κB, and tetraspanin are involved in the exosomes biogenesis. Hypoxic tumor cells release exosomes that induce tumorigenesis through promoting metastasis, angiogenesis, and modulating immune responses. Exosomes from hypoxic tumor cells hold great potential for clinical application and cancer diagnosis. Besides, targeting the biogenesis of these exosomes may be a therapeutic opportunity for reducing tumorigenesis. Exosomes can serve as a drug delivery system transferring therapeutic compounds to cancer cells. Understanding the detailed mechanisms involved in biogenesis and functions of exosomes under hypoxic conditions may help to develop effective therapies against cancer.

Tumor-associated macrophage-targeted therapeutics in ovarian cancer

Ovarian cancer is one of the most common gynecological malignancies. The tumor microenvironment plays an important role in regulating the progression of ovarian cancer. Macrophages, which are important immune cells in the tumor microenvironment, participate in the regulation of various biological behaviors and influence the prognosis of ovarian cancer. A large number of studies have targeted macrophages for the treatment of ovarian cancer. In addition, macrophages also play a regulatory role by interacting with other immune cells, including T cells and mesothelial cells, in the ovarian cancer microenvironment. In this review, we discuss the progress made in macrophage-targeted therapy for ovarian cancer. Although there are still several challenges in using this treatment, targeted macrophage therapy is still a promising treatment for ovarian cancer.

Comparison of Exosomes Derived from Non- and Gamma-Irradiated Melanoma Cancer Cells as a Potential Antigenic and Immunogenic Source for Dendritic Cell-Based Immunotherapeutic Vaccine

Cancer cells can secrete exosomes under various stressful conditions, whose functions are involved in the delivery of various biologically active materials into host cells and/or modulation of host immune responses. Therefore, an improved understanding of the immunological interventions that stress-induced tumor exosomes have may provide novel therapeutic approaches and more effective vaccine designs. Here, we confirmed the phenotypical and functional alterations of dendritic cells (DCs), which act as a bridge between the innate and adaptive arms of immunity, following non-irradiated (N-exo) and gamma-irradiated melanoma cancer cell-derived exosome (G-exo) stimulation, and evaluated the N-exo- and G-exo-stimulated DCs as therapeutic cancer vaccine candidates. We demonstrated that G-exo-stimulated DCs result in DC maturation by the upregulation of surface molecule expression, pro-inflammatory cytokine release, and antigen-presenting ability, and the downregulation of endocytic capacity. In addition, these cells promoted T cell proliferation and the generation of T helper type 1 (Th1) and interferon (IFN)-γ-producing CD8⁺ T cells. However, N-exo-stimulated DCs induced semi-mature phenotypes and functions, eventually inhibiting T cell proliferation, decreasing IFN-γ, and increasing IL-10-producing CD4⁺ T cells. In addition, although N-exo and G-exo stimulations showed similar levels of antigen-specific IFN-γ production, which served as tumor antigen sources in melanoma-specific T cells, G-exo-stimulated DC vaccination conferred a stronger tumor growth inhibition than N-exo-stimulated DC vaccination; further, this was accompanied by a high frequency of tumor-specific, multifunctional effector T cells. These results suggest that gamma irradiation could provide important clues for designing and developing effective exosome vaccines that can induce strong immunogenicity, especially tumor-specific multifunctional T cell responses.

Role of Extracellular Vesicles in Epithelial Ovarian Cancer: A Systematic Review

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived submicron vesicles released under physiological or pathological conditions. EVs mediate the cellular crosstalk, thus contributing to defining the tumor microenvironment, including in epithelial ovarian cancer (EOC). The available literature investigating the role of EVs in EOC has been reviewed following PRISMA guidelines, focusing on the role of EVs in early disease diagnosis, metastatic spread, and the development of chemoresistance in EOC. Data were identified from searches of Medline, Current Contents, PubMed, and from references in relevant articles from 2010 to 1 April 2020. The research yielded 194 results. Of these, a total of 36 papers, 9 reviews, and 27 original types of research were retained and analyzed. The literature findings demonstrate that a panel of EV-derived circulating miRNAs may be useful for early diagnosis of EOC. Furthermore, it appears clear that EVs are involved in mediating two crucial processes for metastatic and chemoresistance development: the epithelial–mesenchymal transition, and tumor escape from the immune system response. Further studies, more focused on in vivo evidence, are urgently needed to clarify the role of EV assessment in the clinical management of EOC patients.

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

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

Protein Cargo of Extracellular Vesicles From Bovine Follicular Fluid and Analysis of Their Origin From Different Ovarian Cells

Follicular fluid (FF) fills the interior portion of the ovarian antral follicle and provides a suitable microenvironment for the growth of the enclosed oocyte through molecular factors that originate from plasma and the secretions of follicular cells. FF contains extracellular nanovesicles (ffEVs), including 30-100-nm membrane-coated exosomes, which carry different types of RNA, proteins, and lipids and directly influence oocyte competence to develop embryo. In the present study, we aimed to characterize the protein cargo of EVs from the FF of 3-6-mm follicles and uncover the origins of ffEVs by assessing expression levels of corresponding mRNAs in bovine follicular cells and oocyte and cell proteomes. Isolated exosome-like ffEVs were 53.6 + 23.3 nm in size and could be internalized by cumulus-oocyte complex. Proteomes of ffEVs and granulosa cells (GC) were assessed using nanoflow liquid chromatography coupled with high-resolution tandem mass spectrometry after the gel fractionation of total proteins. In total, 460 protein isoforms corresponding to 322 unique proteins were identified in ffEVs; among them, 190 were also identified via GC. Gene Ontology terms related to the ribosome, protein and RNA folding, molecular transport, endocytosis, signal transduction, complement and coagulation cascades, apoptosis, and developmental biology pathways, including PI3K-Akt signaling, were significantly enriched features of ffEV proteins. FfEVs contain numerous ribosome and RNA-binding proteins, which may serve to compact different RNAs to regulate gene expression and RNA degradation, and might transfer ribosomal constituents to the oocyte. Majority of genes encoding ffEV proteins expressed at different levels in follicular cells and oocyte, corroborating with numerous proteins, which were reported in bovine oocyte and cumulus cells in other studies thus indicating possible origin of ffEV proteins. The limited abundance of several mRNAs within follicular cells indicated that corresponding ffEV proteins likely originated from circulating exosomes released by other tissues. Analysis of bovine ffEV transcriptome revealed that mRNAs present in ffEV accounted for only 18.3% of detected ffEV proteins. In conclusion, our study revealed numerous proteins within ffEVs, which originated from follicular and other cells. These proteins are likely involved in the maintenance of follicular homeostasis and may affect oocyte competence.

Anchor, Spacer, and Ligand-Modified Engineered Exosomes for Trackable Targeted Therapy

Exosomes have been widely demonstrated as an effective anticancer therapeutic moiety. However, their clinical translation has been limited by the requirement of prohibitively high therapeutic doses due to their lack of specificity in delivery and, consequently, short systemic half-life. To overcome these challenges, we engineered a platform for modifying exosomes with an active targeting modality composed of membrane Anchor (BODIPY)-Spacer (PEG)-targeting Ligands (cyclic RGD peptide) (ASL). Herein, we show that the intramembrane incorporation of a trackable, targeting system renders ASL exosomes (AExs) a modular platform. AExs significantly overcome challenges associated with exosome modification, including potential damage for functionalization, or destabilizing interactions between dyes and drugs. ASL-modification not only enhanced stability in imparting active targeting but also introduced a built-in bioimaging modality. Our studies show that AExs target B16F10 melanoma tumor sites by the specific interaction of cyclic RGD and integrin. Doxorubicin encapsulated AExs (dAExs) significantly inhibited the growth of melanoma in vitro and in vivo. Thus, we conclude that ASL-modification allows exosomes to be transformed into a novel therapeutic vehicle uniquely integrating in vivo tracking and robust targeting with drug delivery. We anticipate that the therapeutic, targeting, and diagnostic modularity provided by ASL will potentiate translational applications of exosome-based vehicles beyond anticancer therapy.

Role of extracellular vesicles in tumour microenvironment

In recent years, it has been demonstrated that extracellular vesicles (EVs) can be released by almost all cell types, and detected in most body fluids. In the tumour microenvironment (TME), EVs serve as a transport medium for lipids, proteins, and nucleic acids. EVs participate in various steps involved in the development and progression of malignant tumours by initiating or suppressing various signalling pathways in recipient cells. Although tumour-derived EVs (T-EVs) are known for orchestrating tumour progression via systemic pathways, EVs from non-malignant cells (nmEVs) also contribute substantially to malignant tumour development. Tumour cells and non-malignant cells typically communicate with each other, both determining the progress of the disease. In this review, we summarise the features of both T-EVs and nmEVs, tumour progression, metastasis, and EV-mediated chemoresistance in the TME. The physiological and pathological effects involved include but are not limited to angiogenesis, epithelial-mesenchymal transition (EMT), extracellular matrix (ECM) remodelling, and immune escape. We discuss potential future directions of the clinical application of EVs, including diagnosis (as non-invasive biomarkers via liquid biopsy) and therapeutic treatment. This may include disrupting EV biogenesis and function, thus utilising the features of EVs to repurpose them as a therapeutic tool in immunotherapy and drug delivery systems. We also discuss the overall findings of current studies, identify some outstanding issues requiring resolution, and propose some potential directions for future research. Video abstract.

Four genes relevant to pathological grade and prognosis in ovarian cancer

BACKGROUND: Ovarian cancer is the common tumor in female, the prognostic of which is influenced by a series of factors. In this study, 4 genes relevant to pathological grade in ovarian cancer were screened out by the construction of weighted gene co-expression network analysis. METHODS: GSE9891 with 298 ovarian cancer cases had been used to construct co-expression networks. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses was used to analyze the possible mechanism of genes involved in the malignant process of ovarian cancer. Hub genes were validated in other independent datasets, such as GSE63885, GSE26193 and GSE30161. Survival analysis based on the hub genes was performed by website of Kaplan Meier-plotter. RESULTS: The result based on weighted gene co-expression network analysis indicated that turquoise module has the highest association with pathological grade. Gene Ontology enrichment analysis revealed that the genes in turquoise module main enrichment in inflammatory response and immune response. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that the genes in turquoise module main enrichment in cytokine-cytokine receptor interaction and chemokine signaling pathway. In turquoise module, a total of 4 hub genes (MS4A4A, CD163, CPR65, MS4A6A) were identified. Then, 4 hub genes were effectively verified in the test datasets (GSE63885, GSE26193 and GSE30161) and tissue samples from Shengjing Hospital of China Medical University. Survival analysis indicated that the 4 hub genes were associated with poor progression-free survival of ovarian cancer. CONCLUSIONS: In conclusion, 4 hub genes (MS4A4A, CD163, CPR65, MS4A6A) were verified associated with pathological grade of ovarian cancer. Moreover, MS4A4A, CD163, MS4A6A may serve as a surface marker for M2 macrophages. Targeting the 4 hub genes may can improve the prognosis of ovarian cancer.

Hypoxia and extracellular vesicles: A review on methods, vesicular cargo and functions

Hypoxia is an essential hallmark of several serious diseases such as cardiovascular and metabolic disorders and cancer. A decline in the tissue oxygen level induces hypoxic responses in cells which strive to adapt to the changed conditions. A failure to adapt to prolonged or severe hypoxia can trigger cell death. While some cell types, such as neurons, are highly vulnerable to hypoxia, cancer cells take advantage of a hypoxic environment to undergo tumour growth, angiogenesis and metastasis. Hypoxia-induced processes trigger complex intercellular communication and there are now indications that extracellular vesicles (EVs) play a fundamental role in these processes. Recent developments in EV isolation and characterization methodology have increased the awareness of the importance of EV purity in functional and cargo studies. Cell death, a hallmark of severe hypoxia, is a known source of intracellular contaminants in isolated EVs. In this review, methodological aspects of studies investigating hypoxia-induced EVs are critically evaluated. Key concerns and gaps in the current knowledge are highlighted and future directions for studies are set. To accelerate and advance research, an in-depth analysis of the functions and cargo of hypoxic EVs, compared to normoxic EVs, is provided with the focus on the altered microRNA contents of the EVs.

MicroRNAs: As Critical Regulators of Tumor- Associated Macrophages

Emerging shreds of evidence suggest that tumor-associated macrophages (TAMs) modulate various hallmarks of cancer during tumor progression. Tumor microenvironment (TME) prime TAMs to execute important roles in cancer development and progression, including angiogenesis, matrix metalloproteinases (MMPs) secretion, and extracellular matrix (ECM) disruption. MicroRNAs (miRNAs) are critical epigenetic regulators, which modulate various functions in diverse types of cells, including macrophages associated with TME. In this review article, we provide an update on miRNAs regulating differentiation, maturation, activation, polarization, and recruitment of macrophages in the TME. Furthermore, extracellular miRNAs are secreted from cancerous cells, which control macrophages phenotypic plasticity to support tumor growth. In return, TAMs also secrete various miRNAs that regulate tumor growth. Herein, we also describe the recent updates on the molecular connection between tumor cells and macrophages. A better understanding of the interaction between miRNAs and TAMs will provide new pharmacological targets to combat cancer.

The Role of Exosomes in Stemness and Neurodegenerative Diseases-Chemoresistant-Cancer Therapeutics and Phytochemicals

Exosomes exhibit a wide range of biological properties and functions in the living organisms. They are nanometric vehicles and used for delivering drugs, as they are biocompatible and minimally immunogenic. Exosomal secretions derived from cancer cells contribute to metastasis, immortality, angiogenesis, tissue invasion, stemness and chemo/radio-resistance. Exosome-derived microRNAs (miRNAs) and long non-coding RNAs (lnc RNAs) are involved in the pathophysiology of cancers and neurodegenerative diseases. For instance, exosomes derived from mesenchymal stromal cells, astrocytes, macrophages, and acute myeloid leukemia (AML) cells are involved in the cancer progression and stemness as they induce chemotherapeutic drug resistance in several cancer cells. This review covered the recent research advances in understanding the role of exosomes in cancer progression, metastasis, angiogenesis, stemness and drug resistance by illustrating the modulatory effects of exosomal cargo (ex. miRNA, lncRNAs, etc.) on cell signaling pathways involved in cancer progression and cancer stem cell growth and development. Recent reports have implicated exosomes even in the treatment of several cancers. For instance, exosomes-loaded with novel anti-cancer drugs such as phytochemicals, tumor-targeting proteins, anticancer peptides, nucleic acids are known to interfere with drug resistance pathways in several cancer cell lines. In addition, this review depicted the need to develop exosome-based novel diagnostic biomarkers for early detection of cancers and neurodegenerative disease. Furthermore, the role of exosomes in stroke and oxidative stress-mediated neurodegenerative diseases including Alzheimer’s disease (AD), and Parkinson’s disease (PD) is also discussed in this article.

Engineering of Exosomes: Steps Towards Green Production of Drug Delivery System

Targeting of therapeutic agents to their specific site of action not only increases the treatment efficacy, but also reduces systemic toxicity. Therefore, various drug delivery systems (DDSs) have been developed to achieve this target. However, most of those DDSs have several issues regarding biocompatibility and environmental hazard. In contrast to the synthetic DDSs, exosome-based natural carriers are biocompatible, biodegradable and safe for the environment. Since exosomes play a role in intercellular communication, they have been widely utilized as carriers for different therapeutic agents. This article was aimed to provide an overview of exosomes as an environment-friendly DDS in terms of engineering, isolation, characterization, application and limitation.

Exosomes from different cells: Characteristics, modifications, and therapeutic applications

Exosomes are cystic vesicles secreted by living cells with a phospholipid bilayer membrane. Importantly, these vesicles could serve to carry lipids, proteins, genetic materials, and transmit biological information in vivo. The cell-specific proteins and genetic materials in exosomes are capable of reflecting their cell origin and physiological status. Based on the different tissues and cells (macrophage, dendritic cells, tumor cells, mesenchymal stem cells, various body fluids, and so on), exosomes exhibit different characteristics and functions. Furthermore, owing to their high delivery efficiency, biocompatibility, and multifunctional properties, exosomes are expected to become a new means of drug delivery, disease diagnosis, immunotherapy, and precise treatment. At the same time, in order to supplement or enhance the therapeutic applicability of exosomes, chemical or biological modifications can be used to broaden, change or improve their therapeutic capabilities. This review focuses on three aspects: the characteristics and original functions of exosomes secreted by different cells, the modification and transformation of exosomes, and the application of exosomes in different diseases.

Ovarian cancer derived PKR1 positive exosomes promote angiogenesis by promoting migration and tube formation in vitro

Cancer cell derived exosomes play important roles in cancer progression and modulation of the tumour microenvironment. This study aims to investigate the role of prokineticin receptor 1 (PKR1) positive exosomes on angiogenesis. In the present study, PKR1 expression in tumour samples from ovarian cancer patients were examined firstly. Then, two ovarian cancer cell lines, namely A2780 and HO-8910 cells, were used to isolate and obtain the PKR1 positive exosomes from the serum free medium. The function analysis of PKR1 positive exosomes on angiogenesis was conducted by cell proliferation and migration assay, tube formation analysis, and tumour volume assay. The results showed that PKR1 expression was down regulated in tumour samples of ovarian cancer patients compared with adjacent normal tissues. The intracellular expression of PKR1 could be detected in A2780 and HO-8910 cells. And, the isolated exosomes from the serum free medium were confirmed by transmission electron microscopic and NTA analysis, as well as the co-presence of PKR1 with exosome marker CD63. The function analysis of PKR1 positive exosomes on angiogenesis demonstrated the uptake of PKR1 positive exosomes by human umbilical vein endothelial cells through immunofluorescence staining. The angiogenesis assays in vitro indicated that PKR1 positive exosomes promoted migration and tube formation of HUVECs but not proliferation. The endogenous PKR1 was also verified to help to enhance migration and promote tube formation of vascular endothelial cells, which might involved in the phosphorylation of STAT3. Additionally, The tumour volume from exosomes treated A2780 tumour-bearing mice was significantly increased compared with the control group, accompanied with the induced PKR1 expression and phosphorylation of STAT3 level. SIGNIFICANCE OF THE STUDY: This study proved the important role of PKR1 positive exosomes released from ovarian cancer cells on promoting angiogenesis. The data indicated that PKR1 derived from ovarian cancer cells could act as an important tumour associated antigen and biomolecular factor for cellular communication in tumour microenvironment.

Macrophage‑derived exosomes attenuate the susceptibility of oral squamous cell carcinoma cells to chemotherapeutic drugs through the AKT/GSK‑3β pathway

Although chemotherapy is initially effective in debulking tumor mass in a number of different types of malignancy, tumor cells gradually acquire chemoresistance and frequently progress to advanced clinical stage. Accumulating evidence has indicated that the tumor sensitivity to several chemotherapeutic drugs is regulated by tumor stromal cells including macrophages. However, the role of macrophages in the efficacy of chemotherapeutics on oral squamous cell carcinoma (OSCC) cells is poorly understood. In the present study, the effects of macrophage-secreted exosomes on the sensitivity of OSCC cells towards chemotherapeutic agents were examined. Specifically, the effects of exosomes derived from THP-1 cells and primary human macrophages (PHM) were assessed on the chemosensitivity of OSC-4 cells treated with 5-fluorouracil (5-FU) and cis-diamminedichloroplatinum (CDDP). The THP-1- and PHM-derived exosomes promoted dose-dependent proliferation, decreased the proliferative inhibitory effects of 5-FU and CDDP and decreased apoptosis in OSC-4 cells through activation of the AKT/glycogen synthase kinase-3β signaling pathway. LY294002, a PI3K inhibitor, and MK-2206, an AKT inhibitor, were both able to suppress the observed decrease in sensitivity to chemotherapeutic agents induced by exosomes. Overall, the data from the present study suggested that the macrophage-derived exosomes may decrease the sensitivity to chemotherapeutic agents in OSCC cells. Thus, targeting the interaction between OSCC cells and macrophage-derived exosomes may be considered as a therapeutic approach to improve the chemosensitivity of the tumor microenvironment in oral cancer.

Exosomes: A Potential Therapeutic Tool Targeting Communications between Tumor Cells and Macrophages

Exosomes comprise extracellular vesicles (EVs) with diameters between 30 and 150 nm. They transfer proteins, RNA, and other molecules from cell to cell, playing an important role in the interactions between cells. The tumor microenvironment (TME) has been found to contain various cells and molecules that have an important impact on tumor development. In the TME, macrophages have been found to have an important relationship with tumor cells, with tumors recruiting and inducing macrophages to become tumor-associated macrophages (TAMs), which promote tumor development. Recently, exosomes have been found to play a critical role in the interaction between tumor cells and macrophages. Thus, in this review, we summarize the roles and mechanisms of exosomes in the interaction between tumor cells and macrophages and the potential methods by which exosomes are used to target the communication between tumor cells and macrophages to treat cancer.

Tumor-derived extracellular vesicles: Regulators of tumor microenvironment and the enlightenment in tumor therapy

In recent decades, extracellular vesicles (EVs) have been proven to establish an important bridge of communication between cells or cells and their microenvironment. It is well known that EVs play crucial roles in many human diseases, especially in tumors. Tumor-derived EVs (TEVs) are not only involved in epithelial-mesenchymal transition and extracellular matrix remodeling to promote the invasion and metastasis, but also contribute to the suppression of antitumor immune responses by carrying different inhibitory molecules. In this review, we mainly discuss the effects of TEVs on the remodeling of tumor microenvironment through immune and non-immune associated mechanisms. We summarize the latest studies about utilizing EVs in clinical diagnosis and therapeutic drug delivery as well. In addition, the perspective of tumor therapy by targeting EVs is discussed in this review.

The clinical impact of intra- and extracellular miRNAs in ovarian cancer

Ovarian cancer is the most lethal gynecological cancer due to lack of early screening methods and acquired drug resistance. MicroRNAs (miRNAs) are effective post‐transcriptional regulators that are transferred by extracellular vesicles, such as exosomes. Numerous studies have revealed that miRNAs are differentially expressed in epithelial ovarian cancer and act either as oncogenes or tumor suppressor genes. Cancer cells secrete exosomes containing miRNAs, which exert various effects on the components of the tumor microenvironment, including cancer‐associated fibroblasts, macrophages, and adipocytes. Conversely, cancer cells also receive exosomes from these cells. As a result of cell‐to‐cell communication, epithelial ovarian cancer acquires a more aggressive phenotype and resistance to multiple drugs. In addition, some circulating miRNAs are protected from RNase degradation in the peripheral blood and can be potential non‐invasive biomarkers. In particular, the combination of several circulating miRNAs enhances the accuracy of cancer screening. Likewise, comprehensive analyses revealed specific miRNA signatures in non‐epithelial ovarian tumors and several miRNAs contributing to alterations of carcinogenic pathways. Overall, miRNAs play a crucial role in ovarian cancer progression. In this review, we discuss the emerging roles of intra‐ and extracellular miRNAs in ovarian cancers. In the near future, miRNAs will be practical biomarkers and computational deep learning will help in the clinical application of miRNAs. Moreover, miRNAs are potential therapeutic targets and agents, and there are ongoing clinical trials of miRNA replacement therapy. Therefore, accelerating research on miRNA might improve the prognosis of patients with ovarian cancer.

Metabolic reprograming of tumor-associated macrophages

A large body of scientific evidence corroborated by clinical and animal model experiments indicates that tumor-associated macrophages (TAMs) play a crucial role in tumor development and progression. TAMs are a key immune cell type present in tumor microenvironment (TME) and associated with poor prognosis, drug resistance, enhanced angiogenesis and metastasis in cancer. TAMs are a phenotypically diverse population of myeloid cells which display tremendous plasticity and dynamic metabolic nature. A complete interpretation of pro-tumoral and anti-tumoral metabolic switch in TAMs is essential to understand immune evasion mechanisms in cancer. Recent studies have also implicated epigenetic mechanisms as significantly regulators of TAM functions. In this review we provide an overview of metabolic circuitry in TAMs, its impact on immune effector cells and interventions aimed at rewiring the metabolic circuits in TAMs. Mechanisms responsible for TAM polarization in cancer are also discussed.

Critical steps to tumor metastasis: alterations of tumor microenvironment and extracellular matrix in the formation of pre-metastatic and metastatic niche

For decades, cancer metastasis has been a heated topic for its high mortality. Previous research has shown that pre-metastatic niche and metastatic niche are the 2 crucial steps in cancer metastasis, assisting cancerous cells' infiltration, survival, and colonization at target sites. More recent studies have unraveled details about the specific mechanisms related to the modification of pro-invasion environments. Here, we will review literatures on extracellular matrix (ECM) alterations, general cancer metastasis, organ specificity, pre-metastatic niche, metastatic niche, colony formation and impact on the course of metastasis. Respectively, the metastatic mechanisms like effect of hypoxia or inflammation on pre-metastatic niche construction, as well as the interaction between cancer cells and local milieu will be discussed. Based on the evidences of metastatic niches, we revisit and discussed the "Seed and Soil" hypothesis by Paget. This review will seek to provide insight into the mechanism of metastatic organ specificity which pre-metastatic niche and metastatic niche might suggest from an evolutionary aspect.

Distinct Cargos of Small Extracellular Vesicles Derived from Hypoxic Cells and Their Effect on Cancer Cells

Hypoxia is a common hallmark of solid tumors and is associated with aggressiveness, metastasis and poor outcome. Cancer cells under hypoxia undergo changes in metabolism and there is an intense crosstalk between cancer cells and cells from the tumor microenvironment. This crosstalk is facilitated by small extracellular vesicles (sEVs; diameter between 30 and 200 nm), including exosomes and microvesicles, which carry a cargo of proteins, mRNA, ncRNA and other biological molecules. Hypoxia is known to increase secretion of sEVs and has an impact on the composition of the cargo. This sEV-mediated crosstalk ultimately leads to various biological effects in the proximal tumor microenvironment but also at distant, future metastatic sites. In this review, we discuss the changes induced by hypoxia on sEV secretion and their cargo as well as their effects on the behavior and metabolism of cancer cells, the tumor microenvironment and metastatic events.

Exosomes: From garbage bins to translational medicine

Exosomes are lipid bilayer-enclosed vesicles of endosomal origin, which initially considered as garbage bins to dispose unwanted cellular components, but they are now emerged as an intercellular communication system involved in several physiological and pathological conditions. With the increasing understanding that the healthy patients release exosomes with distinct proteins and RNAs, exosomes have been exploited as biomarkers for disease diagnosis and prognosis. Owing to the intrinsic immunomodulatory in a tumor microenvironment, exosomes have also been vaccinated into patients against malignant diseases. Moreover, the nano-metered exosomes are relatively stable in extracellular fluids. Thus they appear attractive in delivering "cargo" to destined cells with enhanced efficiency. In this review, we outline the current knowledge in exosomal biogenesis and isolation. Furthermore, the biological activities of exosomes are also discussed with a focus on their potentials to be employed in translational medicine, especially as biomarkers, vaccines and therapeutic delivery system.

Role of Exosomal miRNAs and the Tumor Microenvironment in Drug Resistance

Tumor microenvironment (TME) is composed of different cellular populations, such as stromal, immune, endothelial, and cancer stem cells. TME represents a key factor for tumor heterogeneity maintenance, tumor progression, and drug resistance. The transport of molecules via extracellular vesicles emerged as a key messenger in intercellular communication in the TME. Exosomes are small double-layered lipid extracellular vesicles that can carry a variety of molecules, including proteins, lipids, and nucleic acids. Exosomal miRNA released by cancer cells can mediate phenotypical changes in the cells of TME to promote tumor growth and therapy resistance, for example, fibroblast- and macrophages-induced differentiation. Cancer stem cells can transfer and enhance drug resistance in neighboring sensitive cancer cells by releasing exosomal miRNAs that target antiapoptotic and immune-suppressive pathways. Exosomes induce drug resistance by carrying ABC transporters, which export chemotherapeutic agents out of the recipient cells, thereby reducing the drug concentration to suboptimal levels. Exosome biogenesis inhibitors represent a promising adjunct therapeutic approach in cancer therapy to avoid the acquisition of a resistant phenotype. In conclusion, exosomal miRNAs play a crucial role in the TME to confer drug resistance and survivability to tumor cells, and we also highlight the need for further investigations in this promising field.

Exosomal MicroRNAs as Mediators of Cellular Interactions Between Cancer Cells and Macrophages

Tumor microenvironment consists of cancer cells and various stromal cells such as endothelial cells, cancer-associated fibroblasts (CAFs), myeloid-derived suppressor cells (MDSCs), neutrophils, macrophages, and other innate and adaptive immune cells. Of these innate immune cells, macrophages are an extremely heterogeneous population, and display both pro-inflammatory and anti-inflammatory functions. While M1 macrophages (classically activated macrophages) display anti-tumoral and pro-inflammatory functions, M2 macrophages display pro-tumoral and anti-inflammatory functions. Cellular interactions and molecular factors in the tumor microenvironment affect the polarization of macrophages. We review molecules and immune cells that influence the polarization status of macrophages. Tumor-associated macrophages (TAMs) generally express M2 phenotype, and mediate many processes that include tumor initiation, angiogenesis, and metastasis. A high number of TAMs has been associated with the poor prognosis of cancers. MicroRNAs (miRNAs) have been known to regulate cellular interactions that involve cancer cells and macrophages. Tumor-derived exosomes play critical roles in inducing the M1 or M2-like polarization of macrophages. The roles of exosomal miRNAs from tumor cells in the polarization of macrophages are also discussed and the targets of these miRNAs are presented. We review the effects of exosomal miRNAs from TAMs on cancer cell invasion, growth, and anti-cancer drug resistance. The relevance of exosomal microRNAs (miRNAs) as targets for the development of anti-cancer drugs is discussed. We review recent progress in the development of miRNA therapeutics aimed at elevating or decreasing levels of miRNAs.

Non-coding RNAs shuttled via exosomes reshape the hypoxic tumor microenvironment

Exosomes are small extracellular vesicles secreted by almost all the cells. Molecular cargos of exosomes can partially reflect the characteristics of originating cells. Exosome-mediated cell-to-cell interactions in the microenvironment are critical in cancer progression. Hypoxia, a key pro-cancerous feature of the tumor microenvironment, alters the releasing and contents of exosomes. A growing body of evidence shows that hypoxia induces more aggressive phenotypes in cancer. Of note, non-coding RNAs shuttled in hypoxic tumor-derived exosomes have been demonstrated as fundamental molecules in regulating cancer biology and remodeling tumor microenvironment. Furthermore, these hypoxic tumor-derived exosomal non-coding RNAs can be detected in the body fluids, serving as promising diagnostic and prognostic biomarkers. The current review discusses changes in cancer behaviors regulated by exosomes-secreted non-coding RNAs under hypoxic conditions.

The Role of Tumor-Associated Macrophages in the Progression and Chemoresistance of Ovarian Cancer

Tumor-associated macrophages (TAMs) constitute the main population of immune cells present in the ovarian tumor microenvironment. These cells are characterized by high plasticity and can be easily polarized by colony-stimulating factor-1, which is released by tumor cells, into an immunosuppressive M2-like phenotype. These cells are strongly implicated in both the progression and chemoresistance of ovarian cancer. The main pro-tumoral function of M2-like TAMs is the secretion of a variety of cytokines, chemokines, enzymes and exosomes that reach microRNAs, directly inducing the invasion potential and chemoresistance of ovarian cancer cells by triggering their pro-survival signaling pathways. The M2-like TAMs are also important players in the metastasis of ovarian cancer cells in the peritoneum through their assistance in spheroid formation and attachment of cancer cells to the metastatic area—the omentum. Moreover, TAMs interplay with other immune cells, such as lymphocytes, natural killer cells, and dendritic cells, to inhibit their responsiveness, resulting in the development of immunosuppression. The detrimental character of the M2-like type of TAMs in ovarian tumors has been confirmed by a number of studies, demonstrating the positive correlation between their high level in tumors and low overall survival of patients.

Exosomes derived from endoplasmic reticulum-stressed liver cancer cells enhance the expression of cytokines in macrophages via the STAT3 signaling pathway

Previous studies have shown that endoplasmic reticulum (ER) stress serves an important role in shaping the immunosuppressive microenvironment by modulating resident immune cells. However, the communication between ER-stressed tumor cells and immune cells is not fully understood. Exosomes have been reported to play a vital role in intercellular communication. Therefore, in order to investigate the role of ER stress-related exosomes in liver cancer cells mediated macrophage function remodeling, immunohistochemical analysis, western-blotting immunofluorescence and cytokine bead array analyses were performed. The results demonstrated that glucose-regulated protein 78 (GRP78) expression was upregulated in human liver cancer tissue. Moreover, 69.09% of GRP78-positive liver cancer tissues possessed macrophages expressing CD68⁺ (r=0.55; P<0.001). In addition to these CD68⁺ macrophages, interleukin (IL)-10 and IL-6 expression levels were increased in liver cancer tissues. It was also demonstrated that exosomes released by ER-stressed HepG2 cells significantly enhanced the expression levels of several cytokines, including IL-6, monocyte chemotactic protein-1, IL-10 and tumor necrosis factor-α in macrophages. Furthermore, incubation of cells with ER stress-associated exosomes resulted inactivation of the Janus kinase 2/STAT3 pathway, and inhibition of STAT3 using S3I-201 in RAW264.7 cells significantly reduced cytokine production. Collectively, the present study identified a novel function of ER stress-associated exosomes in mediating macrophage cytokine secretion in the liver cancer microenvironment, and also indicated the potential of treating liver cancer via an ER stress-exosomal-STAT3 pathway.

LncRNA BCRT1 promotes breast cancer progression by targeting miR-1303/PTBP3 axis

Background

Long noncoding RNAs (lncRNAs) play crucial roles in tumor progression and are aberrantly expressed in various cancers. However, the functional roles of lncRNAs in breast cancer remain largely unknown.

Methods

Based on public databases and integrating bioinformatics analyses, the overexpression of lncRNA BCRT1 in breast cancer tissues was detected and further validated in a cohort of breast cancer tissues. The effects of lncRNA BCRT1 on proliferation, migration, invasion and macrophage polarization were determined by in vitro and in vivo experiments. Luciferase reporter assay and RNA immunoprecipitation (RIP) were carried out to reveal the interaction between lncRNA BCRT1, miR-1303, and PTBP3. Chromatin immunoprecipitation (ChIP) and RT-PCR were used to evaluate the regulatory effect of hypoxia-inducible factor-1α (HIF-1α) on lncRNA BCRT1.

Results

LncRNA BCRT1 was significantly upregulated in breast cancer tissues, which was correlated with poor prognosis in breast cancer patients. LncRNA BCRT1 knockdown remarkably suppressed tumor growth and metastasis in vitro and in vivo. Mechanistically, lncRNA BCRT1 could competitively bind with miR-1303 to prevent the degradation of its target gene PTBP3, which acts as a tumor-promoter in breast cancer. LncRNA BCRT1 overexpression could promote M2 polarization of macrophages, mediated by exosomes, which further accelerated breast cancer progression. Furthermore, lncRNA BCRT1 was upregulated in response to hypoxia, which was attributed to the binding of HIF-1α to HREs in the lncRNA BCRT1 promoter.

Conclusions

Collectively, these results reveal a novel HIF-1α/lncRNA BCRT1/miR-1303/PTBP3 pathway for breast cancer progression and suggest that lncRNA BCRT1 might be a potential biomarker and therapeutic target for breast cancer.

microRNAs as biomarkers of ovarian cancer

Introduction: Ovarian carcinoma (OC) is the leading cause of death in women with gynecologic cancers. Most patients are diagnosed at an advanced stage with a low five-year survival rate of 20-30%. Discovering novel biomarkers for early detection and outcome prediction of OC is an urgent medical need. miRNAs, a group of small non-coding RNAs, play critical roles in multiple biologic processes and cancer pathogenesis.Areas covered: We provide an in-depth look at the functions of miRNAs in OC, particularly focusing on their roles in chemoresistance and metastasis in OC. We also discuss the biological and clinical significance of miRNAs in exosomes and expand on long non-coding RNA which acts as ceRNA of miRNAs.Expert opinion: miRNAs participate in many biological processes including proliferation, apoptosis, chemoresistance, metastasis, epithelial-mesenchymal transition, and cancer stem cell. They will substantially contribute to our understanding of OC pathogenesis. Given their resistance to the degradation of ribonucleases and availability in plasma exosomes, miRNAs may serve as emerging biomarkers for cancer detection, therapeutic assessment, and prognostic prediction. Being a messenger, exosomal miRNAs are crucial for the crosstalk between cancer cells and stromal cells in tumor microenvironment.

Breast cancer-derived exosomes transmit lncRNA SNHG16 to induce CD73+γδ1 Treg cells

γδT cells have been reported to exert immunosuppressive functions in multiple solid malignant diseases, but their immunosuppressive functional subpopulation in breast cancer (BC) is still undetermined. Here, we collected 40 paired BC and normal tissue samples from Chinese patients for analysis. First, we showed that γδT1 cells comprise the majority of CD3+ T cells in BC; next, we found that CD73+γδT1 cells were the predominant regulatory T-cell (Treg) population in BC, and that their prevalence in peripheral blood was also related to tumour burden. In addition, CD73+γδT1 cells exert an immunosuppressive effect via adenosine generation. We also found that BC could modulate CD73 expression on γδT cells in a non-contact manner. The microarray analysis and functional experiments indicated that breast tumour cell-derived exosomes (TDEs) could transmit lncRNA SNHG16, which upregulates CD73 expression, to Vδ1 T cells. Regarding the mechanism, SNHG16 served as a ceRNA by sponging miR-16–5p, which led to the derepression of its target gene SMAD5 and resulted in potentiation of the TGF-β1/SMAD5 pathway to upregulate CD73 expression in Vδ1 T cells. Our results showed that the BC-derived exosomal SNHG16/miR-16–5p/SMAD5-regulatory axis potentiates TGF-β1/SMAD5 pathway activation, thus inducing CD73 expression in Vδ1 T cells. Our results first identify the significance of CD73+Vδ1 Tregs in BC, and therapy targeting this subpopulation or blocking TDEs might have potential for BC treatment in the future.

Exosomal miRNAs in tumor microenvironment

Tumor microenvironment (TME) is the internal environment in which tumor cells survive, consisting of tumor cells, fibroblasts, endothelial cells, and immune cells, as well as non-cellular components, such as exosomes and cytokines. Exosomes are tiny extracellular vesicles (40-160nm) containing active substances, such as proteins, lipids and nucleic acids. Exosomes carry biologically active miRNAs to shuttle between tumor cells and TME, thereby affecting tumor development. Tumor-derived exosomal miRNAs induce matrix reprogramming in TME, creating a microenvironment that is conducive to tumor growth, metastasis, immune escape and chemotherapy resistance. In this review, we updated the role of exosomal miRNAs in the process of TME reshaping.

Mammary epithelial cell derived exosomal MiR-221 mediates M1 macrophage polarization via SOCS1/STATs to promote inflammatory response

Lactational mastitis seriously alters the normal physiological function of mammary gland and activates the innate immune. Mammary epithelial cells (MECs) secret cytokines and regulate the function of immune system. However, the mechanism MECs mediated crosstalk with immune cells, such as macrophages, during mastitis is unclear. In this study, mouse mammary epithelial cells (HC11), treated with Lipoteichoic acid (LTA), and macrophages (RAW264.7) were used to mimic intercellular communication. Our results showed that exosomal miR-221 level was up-regulated and reached the peak at 12 h after infected by LTA. The expression of miR-211, CD11b protein and TNF-α mRNA were upregulated and the expression of CD206 protein and Arg-1 mRNA were inhibited in RAW264.7 treated with exosomes. In addition, miR-221 mimics and inhibitors enhanced and depressed HC11-derived exosomal miR-221 level, respectively. After treatment of Exo(mimic) in RAW264.7, the expression of CD11b protein and TNF-α mRNA were up-regulated, the expression of CD206 and Arg-1 mRNA were down-regulated. Additionally, Exo(inhibitor) enhanced CD206 protein and Arg-1 mRNA levels and inhibited CD11b protein and TNF-α mRNA levels. Furthermore, SOCS1 was identified to be a target gene of miR-221 by using Luciferase assays. And western blot assays showed that the expression of p-STAT1 and p-STAT3 were elevated and repressed, respectively. Taken together, we suggest that exosomal miR-221 promotes polarization of M1 macrophages via SOCS1, STAT1 and STAT3. And we reveal a novel crosstalk signaling pathway between mammary epithelial cells and macrophages in the process of inflammation.

The role of cancer-derived microRNAs in cancer immune escape

During malignant transformation, accumulated somatic mutations endow cancer cells with increased invasiveness and immunogenicity. Under selective pressure, these highly immunogenic cancer cells develop multiple strategies to evade immune attack. It has been well established that cancer cells could downregulate the expression of major histocompatibility complex, acquire alterations in interferon pathway, and upregulate the activities of immune checkpoint pathways. Besides, cancer cells secret numerous cytokines, exosomes, and microvesicles to regulate the functions and abundances of components in the tumor microenvironment including immune effector cells and professional antigen presentation cells. As the vital determinant of post-transcriptional regulation, microRNAs (miRNAs) not only participate in cancer initiation and progression but also regulate anti-cancer immune response. For instance, some miRNAs affect cancer immune surveillance and immune escape by interfering the expression of immune attack-associated molecules. A growing body of evidence indicated that cancer-derived immune modulatory miRNAs might be promising targets to counteract cancer immune escape. In this review, we summarized the role of some miRNAs in cancer immune escape and discussed their potential clinical application as treatment targets.

Pathophysiological Role and Potential Therapeutic Exploitation of Exosomes in Ovarian Cancer

Exosomes are extracellular vesicles involved in several biological and pathological molecules and can carry many bioactive materials to target cells. They work as important mediators of cell-cell communication and play essential roles in many diseases, especially in cancer. Ovarian cancer is one of the most common gynecological malignancies. Most patients are diagnosed at advanced stages involving widespread peritoneal dissemination, resulting in poor prognosis. Emerging evidence has shown that exosomes play vital roles throughout the progression of ovarian cancer. Moreover, the development of engineered exosome-based therapeutic applications— including drug delivery systems, biomolecular targets and immune therapy—has increased drastically. Herein, we review the functional features of exosomes in ovarian cancer progression and the therapeutic application potential of exosomes as novel cancer treatments.

Impact of neural stem cell-derived extracellular vesicles on mitochondrial dysfunction, sirtuin 1 level, and synaptic deficits in Alzheimer's disease

Small extracellular vesicles (EVs), including exosomes, play multiple physiological roles. In neurodegenerative diseases, EVs can be pivotal in dispersing neuropathogenic proteins. This study investigates the role of neural stem cell (NSC)-derived EVs in a transgenic (Tg) mouse model of Alzheimer's disease (AD). Five weeks following treatment on 9-month-old APP/PS1 mice, the effects of NSC-derived EVs on cognitive behavior, mitochondrial function, sirtuin1 (SIRT1), synaptic function and morphology, quantification of amyloid-β (Aβ) level, and inflammatory response were investigated. The results showed that mice in the Tg-NSCs-ev group exhibited significant improvement in cognitive performance compared with Tg-Veh group. Furthermore, the expression of mitochondrial function-related factors (peroxisome proliferator-activated receptor-γ coactivator-1α [PGC1α], nuclear respiratory factor 1 and 2 [NRF1 and 2], and fission 1 [Fis1]), SIRT1 as well as synaptic proteins (growth-associated protein 43 [GAP43], synaptophysin [SYP], post-synaptic density 95 [PSD95] and microtubule-associated protein 2 [MAP2]) were significantly higher in the Tg-NSCs-ev group, when compared with the Tg-Veh group. In addition, oxidative damage markers (anti-4-Hydroxynonenal [4-HNE] and anti-3 nitrotyrosine [3-NT]), inflammatory cytokines and the microglial marker (Iba1) were significantly lower in the Tg-NSCs-ev group, compared to the Tg-Veh group. Moreover, synaptic morphology was distinctly improved in the Tg-NSCs-ev group, whereas the Aβ level was not altered. Our study provides novel evidences that NSC-derived EVs enhanced mitochondrial function, SIRT1 activation, synaptic activity, decreased inflammatory response, and rescued cognitive deficits in AD like mice.

The function and clinical application of extracellular vesicles in innate immune regulation

The innate immune system plays a crucial role in the host defense against viral and microbial infection. Exosomes constitute a subset of extracellular vesicles (EVs) that can be released by almost all cell types. Owing to their capacity to shield the payload from degradation and to evade recognition and subsequent removal by the immune system, exosomes efficiently transport functional components to recipient cells. Accumulating evidence has recently shown that exosomes derived from tumor cells, host cells and even bacteria and parasites mediate the communication between the invader and innate immune cells and thus play an irreplaceable function in the dissemination of pathogens and donor cell-derived molecules, modulating the innate immune responses of the host. In this review, we describe the current understanding of EVs (mainly focusing on exosomes) and summarize and discuss their crucial roles in determining innate immune responses. Additionally, we discuss the potential of using exosomes as biomarkers and cancer vaccines in diagnostic and therapeutic applications.

Hypoxia in tumor microenvironment regulates exosome biogenesis: Molecular mechanisms and translational opportunities

Hypoxia is a key feature of solid tumors, associated with disease aggressiveness and poor outcome. Besides undergoing broad intracellular molecular and metabolic adaptations, hypoxic tumor cells extensively communicate with their microenvironment to concoct conditions favorable for their survival, growth and metastatic spread. This mode of communication is through diverse secretory factors including exosomes (extracellular vesicles of endosomal origin and ~30-150 nm in diameter) which could carry package of molecular information including proteins, nucleic acids, lipids, and metabolites wrapped in lipid bilayer. Numerous studies have concluded that hypoxia promotes exosomes secretion by cancer cells. Moreover, exosomal cargo is considerably altered under hypoxia, dictating tumor cells communication with its local and distant microenvironment. In this review, we have summarized the effects of hypoxia on exosomes (Exo^Hypoxic) secretion and cargo sorting (miRNAs, proteins, lipids and metabolites) as well as their biological effects in local and distant microenvironment. We have described the key molecular mechanisms (e.g. HIF-1α, ceramides, RAB GTPases, tetraspanins, oxidative stress etc) involved in the production of Exo^Hypoxic. Lastly, we have highlighted the potential usefulness of Exo^Hypoxic in cancer prognosis as well as therapeutic opportunities in targeting Exo^Hypoxic.

Long non-coding RNA RHPN1-AS1 promotes tumorigenesis and metastasis of ovarian cancer by acting as a ceRNA against miR-596 and upregulating LETM1

Background: In recent decades, long non-coding RNAs (lncRNAs) have been reported as crucial functional regulators involved in ovarian cancer. In the present study, we explored how lncRNA RHPN1-AS1 influences the progression of epithelial ovarian cancer (EOC) through tumor cell-dependent mechanisms.

Results: The expression of RHPN1-AS1 in EOC tissues was higher than that in para-cancerous control tissues. High expression of RHPN1-AS1 was closely associated with poor prognosis in EOC patients. N6-methyladenosine (m6A) improved the stability of RHPN1-AS1 methylation transcript by reducing RNA degradation, which resulted in upregulation of RHPN1-AS1 in EOC. In vitro and in vivo functional experiments showed that RHPN1-AS1 promoted EOC cell proliferation and metastasis. RHPN1-AS1 acted as a ceRNA to sponge miR-596, consequently increasing LETM1 expression and activating the FAK/PI3K/Akt signaling pathway.

Conclusion: RHPN1-AS1-miR-596-LETM1 axis plays a crucial role in EOC progression. Our findings may provide promising drug targets for EOC treatment.

Methods: We determined the aberrantly expressed lncRNAs in EOC via microarray analysis and validated RHPN1-AS1 expression by qRT-PCR. The RHPN1-AS1-miR-596-LETM1 axis was examined by dual-luciferase reporter assay and RIP assay. The mechanism of RHPN1-AS1 was investigated through gain- and loss-of-function studies both in vivo and in vitro.

Tumor-derived extracellular vesicles and microRNAs: Functional roles, diagnostic, prognostic and therapeutic options

In the last few years cancer research more and more highlighted the importance of cell to cell communication in tumor progression. Among many other functional mechanisms, results evidenced the importance of miRNAs loaded into exosomes and their actions as mediators in intercellular communication, either in the tumor microenvironment or at distant sites. Deregulation of miRNA levels is a prerogative of cancer cells and is reflected in the miRNA cargo of tumor derived exosomes. Thus, learning of circulating miRNA activities add the missing piece we need to understand some unclear aspects of cancer biology. Here we summarized the current knowledge on exosome transfer capabilities between cancer cells and all the cells constituting tumor microenvironment with a particular focus on their miRNA cargos and regulatory functions. The clinical relevance of these molecular aspects is emphasized by numerous cell interactions that ultimately result in normal cell function defeat, relevant to increase tumor malignancy. The quantitative and qualitative evaluation of circulating miRNAs offers new perspective for better diagnosis and prognosis of cancer patients, eventually improving their management.

Inhibition of miR-214-3p Aids in Preventing Epithelial Ovarian Cancer Malignancy by Increasing the Expression of LHX6

In human epithelial ovarian cancer (EOC), various miRNAs can function as either oncogenes or tumor suppressor genes. We investigated miRNAs known to be involved in EOC progression and analyzed their expression in tissues and serum-derived exosomes from benign serous cystadenoma, borderline serous tumor, low-grade serous ovarian cancer, and high-grade serous ovarian cancer patients (HGSO). The HGSO group was divided based on the platinum-free interval, which is defined as the duration from the completion of platinum-based chemotherapy to recurrence. We also analyzed the mRNA levels of target genes that candidate miRNAs might regulate in patient tissues. miR-214-3p was highly expressed in tissues and exosomes derived from EOC with high malignancy and also found to regulate the expression of LIM homeobox domain 6 (LHX6) mRNA. Serum exosomal levels of miR-214-3p were significantly increased in platinum-resistant HGSO (25.2-fold, p < 0.001) compared to the exosomal expression of benign tumor patients. On transfection of miR-214-3p inhibitor in EOC cells, cell proliferation was inhibited while apoptotic cell death was increased. Collectively, we suggest that miR-214-3p in serum exosomes can be a potential biomarker for the diagnosis and prognosis of ovarian tumor, and its inhibition can be a supportive treatment for EOC.

Extracellular Vesicles in Cancer Immune Microenvironment and Cancer Immunotherapy

Extracellular vesicles (EVs) are secreted by almost all cells. They contain proteins, lipids, and nucleic acids which are delivered from the parent cells to the recipient cells. Thereby, they function as mediators of intercellular communication and molecular transfer. Recent evidences suggest that exosomes, a small subset of EVs, are involved in numerous physiological and pathological processes and play essential roles in remodeling the tumor immune microenvironment even before the occurrence and metastasis of cancer. Exosomes derived from tumor cells and host cells mediate their mutual regulation locally or remotely, thereby determining the responsiveness of cancer therapies. As such, tumor-derived circulating exosomes are considered as noninvasive biomarkers for early detection and diagnosis of tumor. Exosome-based therapies are also emerging as cutting-edge and promising strategies that could be applied to suppress tumor progression or enhance anti-tumor immunity. Herein, the current understanding of exosomes and their key roles in modulating immune responses, as well as their potential therapeutic applications are outlined. The limitations of current studies are also presented and directions for future research are described.

MicroRNA-A Tumor Trojan Horse for Tumor-Associated Macrophages

MicroRNAs (miRs) significantly contribute to the regulation of gene expression, by virtue of their ability to interact with a broad, yet specific set of target genes. MiRs are produced and released by almost every cell type and play an important role in horizontal gene regulation in the tumor microenvironment (TME). In the TME, both tumor and stroma cells cross-communicate via diverse factors including miRs, which are taking central stage as a therapeutic target of anti-tumor therapy. One of the immune escape strategies adopted by tumor cells is to release miRs as a Trojan horse to hijack circulating or tumor-localized monocytes/macrophages to tune them for pro-tumoral functions. On the other hand, macrophage-derived miRs exert anti-tumor functions. The transfer of miRs from host to recipient cells depends on the supramolecular structure and composition of miR carriers, which determine the distinct uptake mechanism by recipient cells. In this review, we provide a recent update on the miR-mediated crosstalk between tumor cells and macrophages and their mode of uptake in the TME.

miRNAs deregulation in serum of mice is associated with lung cancer related pathway deregulation induced by PM2.5

Ambient fine particulate matter (PM2.5) as an environmental pollution has been associated with the lung cancer. However, the mechanism of epigenetics such as miRNAs deregulation between PM2.5-exposure and lung cancer has not been elucidated clearly. Twenty C57BL/6 mice were divided randomly into 2 groups and exposed to the filtered air (FA) and the concentrated air (CA), respectively. The FA mice were exposed to filtered air in chambers with a high-efficient particulate air filter (HEPA-filter), and the CA mice were exposed to concentration ambient PM2.5. The total duration of exposure was performed 6 h per day from December 1st, 2017 to January 27th, 2018. The mice exposed 900.21 μg/m³ PM2.5 for 6 h per day in CA chamber, which was nearly equaled to 225.05 μg/m³ for 24-h calculatingly. After exposure, the serum miRNAs levels were detected by microarray. Genetic and pathological alterations in lung of mice with/without PM2.5 exposure were detected. 38 differential miRNAs in serum of mice were found after PM2.5 exposure for 8 weeks. Among of them, 13 miRNAs related with lung cancer were consistent in serum and lung of mice. The target genes of 13 deregulated miRNAs including CRK, NR2F2, VIM, RASSF1, CCND2, PRKCA, SIRT1, CDK6, MAP3K7, HIF1A, UBE2V2, ATG10, BAX, E2F1, RASSF5 and CTNNB1, could involve in the pathway of lung cancer developing. Compared with the FA group, the significantly increases of histopathological changes, ROS and DNA damage were observed in lung of mice in CA group. Our study suggested that miRNAs in serum could be identified as candidate biomarkers to predict the lung cancer development during early PM2.5 exposure.

Exosomes promote pre-metastatic niche formation in ovarian cancer

Ovarian cancer is one of the most common gynecological malignancies. Upon initial diagnosis, the majority of patients present with widespread metastatic growth within the peritoneal cavity. This metastatic growth occurs in stages, with the formation of a pre-metastatic niche occurring prior to macroscopic tumor cell invasion. Exosomes released by the primary ovarian tumor are small extracellular vesicles which prepare the distant tumor microenvironment for accelerated metastatic invasion. They regulate intercellular communication between tumor cells and normal stroma, cancer-associated fibroblasts, and local immune cells within the tumor microenvironment. In this review, we highlight the emerging roles of ovarian cancer exosomes as coordinators of pre-metastatic niche formation, biomarkers amenable to liquid biopsy, and targets of chemotherapy.

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

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