Exosomes enriched in stemness/metastatic-related mRNAS promote oncogenic potential in breast cancer

Applications of Exosome Vesicles in Different Cancer Types as Biomarkers

One of the biggest challenges in the fight against cancer is early detection. Early diagnosis is vital, but there are some barriers such as economic, cultural, and personal factors. Considering the disadvantages of radiological imaging techniques or serological analysis methods used in cancer diagnosis, such as being expensive, requiring expertise, and being time-consuming, there is a need to develop faster, more reliable, and cost-effective diagnostic methods for use in cancer diagnosis. Exosomes, which are responsible for intercellular communication with sizes ranging from 30-120 nm, are naturally produced biological nanoparticles. Thanks to the cargo contents they carry, they are a potential biomarker to be used in the diagnosis of cancer. Exosomes, defined as extracellular vesicles of endosomal origin, are effective in cancer growth, progression, metastasis, and drug resistance, and changes in microenvironmental conditions during tumor development change exosome secretion. Due to their high cellular activity, tumor cells produce much higher exosomes than healthy cells. Therefore, it is known that the number of exosomes in body fluids is significantly rich compared to other cells and can act as a stand-alone diagnostic biomarker. Cancer- derived exosomes have received great attention in recent years for the early detection of cancer and the evaluation of therapeutic response. In this article, the content, properties, and differences of exosomes detected in common types of cancer (lung, liver, pancreas, ovaries, breast, colorectal), which are the leading causes of cancer-related deaths, are reviewed. We also discuss the potential utility of exosome contents as a biomarker for early detection, which is known to be important in targeted cancer therapy.

The Diversity of Liquid Biopsies and Their Potential in Breast Cancer Management

Analyzing blood as a so-called liquid biopsy in breast cancer (BC) patients has the potential to adapt therapy management. Circulating tumor cells (CTCs), extracellular vesicles (EVs), cell-free DNA (cfDNA) and other blood components mirror the tumoral heterogeneity and could support a range of clinical decisions. Multi-cancer early detection tests utilizing blood are advancing but are not part of any clinical routine yet. Liquid biopsy analysis in the course of neoadjuvant therapy has potential for therapy (de)escalation.Minimal residual disease detection via serial cfDNA analysis is currently on its way. The prognostic value of blood analytes in early and metastatic BC is undisputable, but the value of these prognostic biomarkers for clinical management is controversial. An interventional trial confirmed a significant outcome benefit when therapy was changed in case of newly emerging cfDNA mutations under treatment and thus showed the clinical utility of cfDNA analysis for therapy monitoring. The analysis of PIK3CA or ESR1 variants in plasma of metastatic BC patients to prescribe targeted therapy with alpesilib or elacestrant has already arrived in clinical practice with FDA-approved tests available and is recommended by ASCO. The translation of more liquid biopsy applications into clinical practice is still pending due to a lack of knowledge of the analytes' biology, lack of standards and difficulties in proving clinical utility.

Organic Electronic Platform for Real-Time Phenotypic Screening of Extracellular-Vesicle-Driven Breast Cancer Metastasis

Tumor-derived extracellular vesicles (TEVs) induce the epithelial-to-mesenchymal transition (EMT) in nonmalignant cells to promote invasion and cancer metastasis, representing a novel therapeutic target in a field severely lacking in efficacious antimetastasis treatments. However, scalable technologies that allow continuous, multiparametric monitoring for identifying metastasis inhibitors are absent. Here, the development of a functional phenotypic screening platform based on organic electrochemical transistors (OECTs) for real-time, noninvasive monitoring of TEV-induced EMT and screening of antimetastatic drugs is reported. TEVs derived from the triple-negative breast cancer cell line MDA-MB-231 induce EMT in nonmalignant breast epithelial cells (MCF10A) over a nine-day period, recapitulating a model of invasive ductal carcinoma metastasis. Immunoblot analysis and immunofluorescence imaging confirm the EMT status of TEV-treated cells, while dual optical and electrical readouts of cell phenotype are obtained using OECTs. Further, heparin, a competitive inhibitor of cell surface receptors, is identified as an effective blocker of TEV-induced EMT. Together, these results demonstrate the utility of the platform for TEV-targeted drug discovery, allowing for facile modeling of the transient drug response using electrical measurements, and provide proof of concept that inhibitors of TEV function have potential as antimetastatic drug candidates.

Deciphering the Functional Status of Breast Cancers through the Analysis of Their Extracellular Vesicles

Breast cancer (BC) accounts for the highest incidence of tumor-related mortality among women worldwide, justifying the growing search for molecular tools for the early diagnosis and follow-up of BC patients under treatment. Circulating extracellular vesicles (EVs) are membranous nanocompartments produced by all human cells, including tumor cells. Since minimally invasive methods collect EVs, which represent reservoirs of signals for cell communication, these particles have attracted the interest of many researchers aiming to improve BC screening and treatment. Here, we analyzed the cargoes of BC-derived EVs, both proteins and nucleic acids, which yielded a comprehensive list of potential markers divided into four distinct categories, namely, (i) modulation of aggressiveness and growth; (ii) preparation of the pre-metastatic niche; (iii) epithelial-to-mesenchymal transition; and (iv) drug resistance phenotype, further classified according to their specificity and sensitivity as vesicular BC biomarkers. We discuss the therapeutic potential of and barriers to the clinical implementation of EV-based tests, including the heterogeneity of EVs and the available technologies for analyzing their content, to present a consistent, reproducible, and affordable set of markers for further evaluation.

Paper-based biosensors as point-of-care diagnostic devices for the detection of cancers: a review of innovative techniques and clinical applications

The development and rapid progression of cancer are major social problems. Medical diagnostic techniques and smooth clinical care of cancer are new necessities that must be supported by innovative diagnostic methods and technologies. Current molecular diagnostic tools based on the detection of blood protein markers are the most common tools for cancer diagnosis. Biosensors have already proven to be a cost-effective and accessible diagnostic tool that can be used where conventional laboratory methods are not readily available. Paper-based biosensors offer a new look at the world of analytical techniques by overcoming limitations through the creation of a simple device with significant advantages such as adaptability, biocompatibility, biodegradability, ease of use, large surface-to-volume ratio, and cost-effectiveness. In this review, we covered the characteristics of exosomes and their role in tumor growth and clinical diagnosis, followed by a discussion of various paper-based biosensors for exosome detection, such as dipsticks, lateral flow assays (LFA), and microfluidic paper-based devices (µPADs). We also discussed the various clinical studies on paper-based biosensors for exosome detection.

Extracellular Vesicles in Breast Cancer: From Biology and Function to Clinical Diagnosis and Therapeutic Management

Breast cancer (BC) is the first worldwide most frequent cancer in both sexes and the most commonly diagnosed in females. Although BC mortality has been thoroughly declining over the past decades, there are still considerable differences between women diagnosed with early BC and when metastatic BC is diagnosed. BC treatment choice is widely dependent on precise histological and molecular characterization. However, recurrence or distant metastasis still occurs even with the most recent efficient therapies. Thus, a better understanding of the different factors underlying tumor escape is mainly mandatory. Among the leading candidates is the continuous interplay between tumor cells and their microenvironment, where extracellular vesicles play a significant role. Among extracellular vesicles, smaller ones, also called exosomes, can carry biomolecules, such as lipids, proteins, and nucleic acids, and generate signal transmission through an intercellular transfer of their content. This mechanism allows tumor cells to recruit and modify the adjacent and systemic microenvironment to support further invasion and dissemination. By reciprocity, stromal cells can also use exosomes to profoundly modify tumor cell behavior. This review intends to cover the most recent literature on the role of extracellular vesicle production in normal and cancerous breast tissues. Specific attention is paid to the use of extracellular vesicles for early BC diagnosis, follow-up, and prognosis because exosomes are actually under the spotlight of researchers as a high-potential source of liquid biopsies. Extracellular vesicles in BC treatment as new targets for therapy or efficient nanovectors to drive drug delivery are also summarized.

Optimization of a method for the clinical detection of serum exosomal miR-940 as a potential biomarker of breast cancer

Serum exosomal microRNAs (miRNAs) are potential biomarkers for tumor diagnosis. Clinically, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) can be used to determine the expression of exosomal miRNAs in the serum of breast cancer patients. The prerequisites for obtaining meaningful serum exosomal miRNA data of breast cancer patients include a suitable extraction method for exosomes and RT-qPCR data standardized by internal reference genes. However, the appropriate methods for the extraction of exosomes and the applicability of reference genes for analyzing exosomal miRNAs in breast cancer patients remain to be studied. This study compared the effects of three exosome extraction methods as well as the expression of exosomal miRNA in different initial serum amounts and at different serum states to identify the selection of the best method for serum exosome extraction. Five candidate reference genes including miR-16, miR-484, miR-1228, miR-191 and miR-423 for standardizing serum exosomal miRNAs were screened using five algorithms and were used for the quantification of serum exosomal miR-940. Significant downregulation of serum exosomal miR-940 expression in breast cancer was detected using miR-191 and miR-1228, whereas no significant down or up regulation was observed with miR-484, miR-423 and miR-16. Previous studies have shown that the expression level of miR-940 is downregulated in breast cancer tissues. The absolute quantitative results showed that miR-940 was significantly downregulated in breast cancer serum exosomes, which was consistent with the results from the analysis using miR-191 or miR-1228 as reference genes. Therefore, miR-191 and miR-1228 could serve as reference genes for the relative quantification of serum exosomal miRNAs. This finding indicated the importance of rigorously evaluating the stability of reference genes and standardization for serum exosomal miRNA expression. Moreover, the level of serum exosomal miR-940 in breast cancer could reflect the presence of lymph node metastasis and the status of HER2/neu, which indicates its potential as a biomarker for breast cancer metastasis. In summary, an optimized protocol for the detection of serum exosomal miR-940 as a breast cancer marker was preliminarily established.

Extracellular vesicles and particles impact the systemic landscape of cancer

Intercellular cross talk between cancer cells and stromal and immune cells is essential for tumor progression and metastasis. Extracellular vesicles and particles (EVPs) are a heterogeneous class of secreted messengers that carry bioactive molecules and that have been shown to be crucial for this cell-cell communication. Here, we highlight the multifaceted roles of EVPs in cancer. Functionally, transfer of EVP cargo between cells influences tumor cell growth and invasion, alters immune cell composition and function, and contributes to stromal cell activation. These EVP-mediated changes impact local tumor progression, foster cultivation of pre-metastatic niches at distant organ-specific sites, and mediate systemic effects of cancer. Furthermore, we discuss how exploiting the highly selective enrichment of molecules within EVPs has profound implications for advancing diagnostic and prognostic biomarker development and for improving therapy delivery in cancer patients. Altogether, these investigations into the role of EVPs in cancer have led to discoveries that hold great promise for improving cancer patient care and outcome.

Small extracellular vesicles: from promoting pre-metastatic niche formation to therapeutic strategies in breast cancer

Breast cancer is the most common cancer in females, and to date, the mortality rate of breast cancer metastasis cannot be ignored. The metastasis of breast cancer is a complex, staged process, and the pattern of metastatic spread is not random. The pre-metastatic niche, as an organ-specific home for metastasis, is a favourable environment for tumour cell colonization. As detection techniques improve, the role of the pre-metastatic niche in breast cancer metastasis is being uncovered. sEVs (small extracellular vesicles) can deliver cargo, which is vital for the formation of pre-metastatic niches. sEVs participate in multiple aspects of creating a distant microenvironment to promote tumour invasion, including the secretion of inflammatory molecules, immunosuppression, angiogenesis and enhancement of vascular permeability, as well as regulation of the stromal environment. Here, we discuss the multifaceted mechanisms through which breast cancer-derived sEVs contribute to pre-metastatic niches. In addition, sEVs as biomarkers and antimetastatic therapies are also discussed, particularly their use in transporting exosomal microRNAs. The study of sEVs may provide insight into immunotherapy and targeted therapies for breast cancer, and we also provide an overview of their potential role in antitumour metastasis.

Circulating Exosome Cargoes Contain Functionally Diverse Cancer Biomarkers: From Biogenesis and Function to Purification and Potential Translational Utility

Although diagnostic and therapeutic treatments of cancer have tremendously improved over the past two decades, the indolent nature of its symptoms has made early detection challenging. Thus, inter-disciplinary (genomic, transcriptomic, proteomic, and lipidomic) research efforts have been focused on the non-invasive identification of unique "silver bullet" cancer biomarkers for the design of ultra-sensitive molecular diagnostic assays. Circulating tumor biomarkers, such as CTCs and ctDNAs, which are released by tumors in the circulation, have already demonstrated their clinical utility for the non-invasive detection of certain solid tumors. Considering that exosomes are actively produced by all cells, including tumor cells, and can be found in the circulation, they have been extensively assessed for their potential as a source of circulating cell-specific biomarkers. Exosomes are particularly appealing because they represent a stable and encapsulated reservoir of active biological compounds that may be useful for the non-invasive detection of cancer. T biogenesis of these extracellular vesicles is profoundly altered during carcinogenesis, but because they harbor unique or uniquely combined surface proteins, cancer biomarker studies have been focused on their purification from biofluids, for the analysis of their RNA, DNA, protein, and lipid cargoes. In this review, we evaluate the biogenesis of normal and cancer exosomes, provide extensive information on the state of the art, the current purification methods, and the technologies employed for genomic, transcriptomic, proteomic, and lipidomic evaluation of their cargoes. Our thorough examination of the literature highlights the current limitations and promising future of exosomes as a liquid biopsy for the identification of circulating tumor biomarkers.

Exosome-Associated circRNAs as Key Regulators of EMT in Cancer

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

Identification of Potential mRNA Biomarkers in Milk Small Extracellular Vesicles of Enzootic Bovine Leukosis Cattle

Enzootic bovine leukosis (EBL) is a disease caused by bovine leukemia virus (BLV); only a small percentage of BLV-infected cattle develop EBL and present with B-cell lymphosarcoma. There is no vaccine against BLV, treatment for EBL, or method for predicting the possibility of EBL onset, thus making EBL control difficult. Herein, to explore biomarkers for EBL in milk, we examined the mRNA profiles of small extracellular vesicles (sEVs) in milk from four BLV-uninfected and four EBL cattle by microarray analysis. It was revealed that 14 mRNAs were encapsulated in significantly higher quantities, and these mRNAs were therefore selected as biomarker candidates. Primers for these mRNAs were designed, and nine primer sets were available for quantitative real-time PCR. Nine mRNAs were evaluated for their availability as biomarkers for EBL using sEVs from newly-collected milk of 7 uninfected and 10 EBL cattle. The quantities of eight mRNAs (TMEM156, SRGN, CXCL8, DEFB4A, FABP5, LAPTM5, LGALS1, and VIM) were significantly higher in milk sEVs of EBL cattle than in those of uninfected cattle. Therefore, our findings indicate that these eight mRNAs in milk sEVs can be used as potential EBL biomarkers with combination use, although single mRNA use is not enough. Consequently, cattle at risk of EBL onset can be identified by monitoring the fluctuation in quantities of these mRNAs in milk before they develop EBL.

Combinatorial Power of cfDNA, CTCs and EVs in Oncology

Liquid biopsy is a promising technique for clinical management of oncological patients. The diversity of analytes circulating in the blood useable for liquid biopsy testing is enormous. Circulating tumor cells (CTCs), cell-free DNA (cfDNA) and extracellular vesicles (EVs), as well as blood cells and other soluble components in the plasma, were shown as liquid biopsy analytes. A few studies directly comparing two liquid biopsy analytes showed a benefit of one analyte over the other, while most authors concluded the benefit of the additional analyte. Only three years ago, the first studies to examine the value of a characterization of more than two liquid biopsy analytes from the same sample were conducted. We attempt to reflect on the recent development of multimodal liquid biopsy testing in this review. Although the analytes and clinical purposes of the published multimodal studies differed significantly, the additive value of the analytes was concluded in almost all projects. Thus, the blood components, as liquid biopsy reservoirs, are complementary rather than competitive, and orthogonal data sets were even shown to harbor synergistic effects. The unmistakable potential of multimodal liquid biopsy testing, however, is dampened by its clinical utility, which is yet to be proven, the lack of methodical standardization and insufficiently mature reimbursement, logistics and data handling.

The Role of Small Extracellular Vesicles in the Progression of Colorectal Cancer and Its Clinical Applications

Colorectal cancer (CRC) is one of the most common cancers worldwide and a longstanding critical challenge for public health. Screening has been suggested to effectively reduce both the incidence and mortality of CRC. However, the drawback of the current screening modalities, both stool-based tests and colonoscopies, is limited screening adherence, which reduces the effectiveness of CRC screening. Blood tests are more acceptable than stool tests or colonoscopy as a first-line screening approach. Therefore, identifying blood biomarkers for detecting CRC and its precancerous neoplasms is urgently needed to fulfill the unmet clinical need. Currently, many kinds of blood contents, such as circulating tumor cells, circulating tumor nucleic acids, and extracellular vesicles, have been investigated as biomarkers for CRC detection. Among these, small extracellular vesicles (sEVs) have been demonstrated to detect CRC effectively in recent reports. sEVs enable intercellular shuttling—for instance, trafficking between recipient cancer cells and stromal cells—which can affect tumor initiation, proliferation, angiogenesis, immune regulation; metastasis, the cancer-specific molecules, such as proteins, microRNAs, long noncoding RNAs, and circular RNAs, loaded into cancer-derived sEVs may serve as biomarkers for the detection of cancers, including CRC. Indeed, accumulating evidence has shown that nucleic acids and proteins contained in CRC-derived sEVs are effective as blood biomarkers for CRC detection. However, investigations of the performance of sEVs for diagnosing CRC in clinical trials remains limited. Thus, the effectiveness of sEV biomarkers for diagnosing CRC needs further validation in clinical trials.

Exosomes in breast cancer management. Where do we stand? A literature review

BACKGROUND

Exosomes constitute cellular molecular fingertips that participate in intercellular communication both in health and disease states. Hence, exosomes emerge as critical mediators of cancer development and progression, as well as potential biomarkers and novel therapeutic targets.

OBJECTIVE

To review literature data regarding applications of circulating exosomes in breast cancer management.

METHODS

This is a literature review of relevant published studies until April 2020 in PubMed and Google Scholar databases. Original papers in the English language concerning exosome related studies were included.

RESULTS

Exosomes represent molecular miniatures of their parent cells. Several homeostatic mechanisms control exosomal secretion and synthesis. Exosomal exchange among cells creates an intricate intercellular crosstalk orchestrating almost every tissue process, as well as carcinogenesis. Available data highlight exosomes as major mediators of cancer development and progression. The secretion of specific exosomal molecules, particularly miRNAs, correlates with the underlying processes and can be used as a means of tumor detection and prognostic assessment.

CONCLUSIONS

Exosomal miRNAs expression profiles and levels closely relate to cancer extent, type and prognosis. Deep comprehension of such correlations and systematization of experimental outcomes will offer a novel approach in cancer detection and management. This article is protected by copyright. All rights reserved.

AMIGO2 contained in cancer cell-derived extracellular vesicles enhances the adhesion of liver endothelial cells to cancer cells

Adhesion of cancer cells to vascular endothelial cells in target organs is an initial step in cancer metastasis. Our previous studies revealed that amphoterin-induced gene and open reading frame 2 (AMIGO2) promotes the adhesion of tumor cells to liver endothelial cells, followed by the formation of liver metastasis in a mouse model. However, the precise mechanism underlying AMIGO2-promoted the adhesion of tumor cells and liver endothelial cells remains unknown. This study was conducted to explore the role of cancer cell-derived AMIGO2-containing extracellular vesicles (EVs) in the adhesion of cancer cells to human hepatic sinusoidal endothelial cells (HHSECs). Western blotting indicated that AMIGO2 was present in EVs from AMIGO2-overexpressing MKN-28 gastric cancer cells. The efficiency of EV incorporation into HHSECs was independent of the AMIGO2 content in EVs. When EV-derived AMIGO2 was internalized in HHSECs, it significantly enhanced the adhesion of HHSECs to gastric (MKN-28 and MKN-74) and colorectal cancer cells (SW480), all of which lacked AMIGO2 expression. Thus, we identified a novel mechanism by which EV-derived AMIGO2 released from AMIGO2-expressing cancer cells stimulates endothelial cell adhesion to different cancer cells for the initiate step of liver metastasis.

Tumor-Derived Exosomal Non-Coding RNAs: The Emerging Mechanisms and Potential Clinical Applications in Breast Cancer

Breast cancer (BC) is the most frequent malignancy and is ranking the leading cause of cancer-related death among women worldwide. At present, BC is still an intricate challenge confronted with high invasion, metastasis, drug resistance, and recurrence rate. Exosomes are membrane-enclosed extracellular vesicles with the lipid bilayer and recently have been confirmed as significant mediators of tumor cells to communicate with surrounding cells in the tumor microenvironment. As very important orchestrators, non-coding RNAs (ncRNAs) are aberrantly expressed and participate in regulating gene expression in multiple human cancers, while the most reported ncRNAs within exosomes in BC are microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Notably, ncRNAs containing exosomes are novel frontiers to shape malignant behaviors in recipient BC cells such as angiogenesis, immunoregulation, proliferation, and migration. It means that tumor-derived ncRNAs-containing exosomes are pluripotent carriers with intriguing and elaborate roles in BC progression via complex mechanisms. The ncRNAs in exosomes are usually excavated based on specific de-regulated expression verified by RNA sequencing, bioinformatic analyses, and PCR experiments. Here, this article will elucidate the recent existing research on the functions and mechanisms of tumor-derived exosomal miRNA, lncRNA, circRNA in BC, especially in BC cell proliferation, metastasis, immunoregulation, and drug resistance. Moreover, these tumor-derived exosomal ncRNAs that existed in blood samples are proved to be excellent diagnostic biomarkers for improving diagnosis and prognosis. The in-depth understanding of tumor-derived exosomal ncRNAs in BC will provide further insights for elucidating the BC oncogenesis and progress and exploring novel therapeutic strategies for combating BC.

Emerging role of tumor microenvironment derived exosomes in therapeutic resistance and metastasis through epithelial-to-mesenchymal transition

The tumor microenvironment (TME) constitutes multiple cell types including cancerous and non-cancerous cells. The intercellular communication between these cells through TME derived exosomes may either enhance or suppress the tumorigenic processes. The tumor-derived exosomes could convert an anti-tumor environment into a pro-tumor environment by inducing the differentiation of stromal cells into tumor-associated cells. The exosomes from tumor-associated stromal cells reciprocally trigger epithelial-to-mesenchymal transition (EMT) in tumor cells, which impose therapeutic resistance and metastasis. It is well known that these exosomes contain the signals of EMT, but how these signals execute chemoresistance and metastasis in tumors remains elusive. Understanding the significance and molecular signatures of exosomes transmitting EMT signals would aid in developing appropriate methods of inhibiting them. In this review, we focus on molecular signatures of exosomes that shuttle between cancer cells and their stromal populations in TME to explicate their impact on therapeutic resistance and metastasis through EMT. Especially Wnt signaling is found to be involved in multiple ways of exosomal transport and hence we decipher the biomolecules of Wnt signaling trafficked through exosomes and their potential in serving as therapeutic targets.

Tumor-derived exosomal components: the multifaceted roles and mechanisms in breast cancer metastasis

Breast cancer (BC) is the most frequently invasive malignancy and the leading cause of tumor-related mortality among women worldwide. Cancer metastasis is a complex, multistage process, which eventually causes tumor cells to colonize and grow at the metastatic site. Distant organ metastases are the major obstacles to the management of advanced BC patients. Notably, exosomes are defined as specialized membrane-enclosed extracellular vesicles with specific biomarkers, which are found in a wide variety of body fluids. Recent studies have demonstrated that exosomes are essential mediators in shaping the tumor microenvironment and BC metastasis. The transferred tumor-derived exosomes modify the capability of invasive behavior and organ-specific metastasis in recipient cells. BC exosomal components, mainly including noncoding RNAs (ncRNAs), proteins, lipids, are the most investigated components in BC metastasis. In this review, we have emphasized the multifaceted roles and mechanisms of tumor-derived exosomes in BC metastasis based on these important components. The underlying mechanisms mainly include the invasion behavior change, tumor vascularization, the disruption of the vascular barrier, and the colonization of the targeted organ. Understanding the significance of tumor-derived exosomal components in BC metastasis is critical for yielding novel routes of BC intervention.

Integrative statistical analyses of multiple liquid biopsy analytes in metastatic breast cancer

Background

Single liquid biopsy analytes (LBAs) have been utilized for therapy selection in metastatic breast cancer (MBC). We performed integrative statistical analyses to examine the clinical relevance of using multiple LBAs: matched circulating tumor cell (CTC) mRNA, CTC genomic DNA (gDNA), extracellular vesicle (EV) mRNA, and cell-free DNA (cfDNA).

Methods

Blood was drawn from 26 hormone receptor-positive, HER2-negative MBC patients. CTC mRNA and EV mRNA were analyzed using a multi-marker qPCR. Plasma from CTC-depleted blood was utilized for cfDNA isolation. gDNA from CTCs was isolated from mRNA-depleted CTC lysates. CTC gDNA and cfDNA were analyzed by targeted sequencing. Hierarchical clustering was performed within each analyte, and its results were combined into a score termed Evaluation of multiple Liquid biopsy analytes In Metastatic breast cancer patients All from one blood sample (ELIMA.score), which calculates the contribution of each analyte to the overall survival prediction. Singular value decomposition (SVD), mutual information calculation, k-means clustering, and graph-theoretic analysis were conducted to elucidate the dependence between individual analytes.

Results

A combination of two/three/four LBAs increased the prevalence of patients with actionable signals. Aggregating the results of hierarchical clustering of individual LBAs into the ELIMA.score resulted in a highly significant correlation with overall survival, thereby bolstering evidence for the additive value of using multiple LBAs. Computation of mutual information indicated that none of the LBAs is independent of the others, but the ability of a single LBA to describe the others is rather limited—only CTC gDNA could partially describe the other three LBAs. SVD revealed that the strongest singular vectors originate from all four LBAs, but a majority originated from CTC gDNA. After k-means clustering of patients based on parameters of all four LBAs, the graph-theoretic analysis revealed CTC ERBB2 variants only in patients belonging to one particular cluster.

Conclusions

The additional benefits of using all four LBAs were objectively demonstrated in this pilot study, which also indicated a relative dominance of CTC gDNA over the other LBAs. Consequently, a multi-parametric liquid biopsy approach deconvolutes the genomic and transcriptomic complexity and should be considered in clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-021-00902-1.

Exosomes and Cancer Stem Cells in Cancer Immunity: Current Reports and Future Directions

Cancer stem cells (CSCs), which have the capacity to self-renew and differentiate into various types of cells, are notorious for their roles in tumor initiation, metastasis, and therapy resistance. Thus, underlying mechanisms for their survival provide key insights into developing effective therapeutic strategies. A more recent focus has been on exosomes that play a role in transmitting information between CSCs and non-CSCs, resulting in activating CSCs for cancer progression and modulating their surrounding microenvironment. The field of CSC-derived exosomes (CSCEXs) for different types of cancer is still under exploration. A deeper understanding and further investigation into CSCEXs’ roles in tumorigenicity and the identification of novel exosomal components are necessary for engineering exosomes for the treatment of cancer. Here, we review the features of CSCEXs, including surface markers, cargo, and biological or physiological functions. Further, reports on the immunomodulatory effects of CSCEXs are summarized, and exosome engineering for CSC-targeting is also discussed.

Breast Cancer Microenvironment Cross Talk through Extracellular Vesicle RNAs

Exploration of extracellular communication has been at the forefront of research efforts in recent years. However, the mechanisms of cell-to-cell communication in complex tissues are poorly understood. What is clear is that cells do not exist in isolation, that they are constantly interacting and communicating with cells in the immediate vicinity and with cells at a distance. Intercellular communication by the release of small extracellular vesicles, called exosomes, loaded with RNAs is one mechanism by which cells communicate. In recent years, research has shown that exosomes, a class of extracellular vesicles, can play a major role in the pathogenesis of breast cancer. Specifically, exosomes have been demonstrated to play a role in promoting primary cancer development, invasion, metastasis, and chemotherapeutic resistance. This review summarizes what is known about the mechanisms of exosome-mediated transfer of RNAs among cells in the breast microenvironment and discusses outstanding questions and the potential for new therapeutic intervention targeted at these interactions.

Understanding the function of the tumor microenvironment, and compounds from marine organisms for breast cancer therapy

The pathology and physiology of breast cancer (BC), including metastasis, and drug resistance, is driven by multiple signaling pathways in the tumor microenvironment (TME), which hamper antitumor immunity. Recently, long non-coding RNAs have been reported to mediate pathophysiological develop-ments such as metastasis as well as immune suppression within the TME. Given the complex biology of BC, novel personalized therapeutic strategies that address its diverse pathophysiologies are needed to improve clinical outcomes. In this review, we describe the advances in the biology of breast neoplasia, including cellular and molecular biology, heterogeneity, and TME. We review the role of novel molecules such as long non-coding RNAs in the pathophysiology of BC. Finally, we provide an up-to-date overview of anticancer compounds extracted from marine microorganisms, crustaceans, and fishes and their synergistic effects in combination with other anticancer drugs. Marine compounds are a new discipline of research in BC and offer a wide range of anti-cancer effects that could be harnessed to target the various pathways involved in BC development, thus assisting current therapeutic regimens.

Current Status of Circulating Tumor Cells, Circulating Tumor DNA, and Exosomes in Breast Cancer Liquid Biopsies

Breast cancer is the most common cancer among women worldwide. Although the five-, ten- and fifteen-year survival rates are good for breast cancer patients diagnosed with early-stage disease, some cancers recur many years after completion of primary therapy. Tumor heterogeneity and clonal evolution may lead to distant metastasis and therapy resistance, which are the main causes of breast cancer-associated deaths. In the clinic today, imaging techniques like mammography and tissue biopsies are used to diagnose breast cancer. Even though these methods are important in primary diagnosis, they have limitations when it comes to longitudinal monitoring of residual disease after treatment, disease progression, therapy responses, and disease recurrence. Over the last few years, there has been an increasing interest in the diagnostic, prognostic, and predictive potential of circulating cancer-derived material acquired through liquid biopsies in breast cancer. Thanks to the development of sensitive devices and platforms, a variety of tumor-derived material, including circulating cancer cells (CTCs), circulating DNA (ctDNA), and biomolecules encapsulated in extracellular vesicles, can now be extracted and analyzed from body fluids. Here we will review the most recent studies on breast cancer, demonstrating the clinical potential and utility of CTCs and ctDNA. We will also review literature illustrating the potential of circulating exosomal RNA and proteins as future biomarkers in breast cancer. Finally, we will discuss some of the advantages and limitations of liquid biopsies and the future perspectives of this field in breast cancer management.

Lung Carcinoma Cells Secrete Exosomal MALAT1 to Inhibit Dendritic Cell Phagocytosis, Inflammatory Response, Costimulatory Molecule Expression and Promote Dendritic Cell Autophagy via AKT/mTOR Pathway

Objective

To investigate the potential mechanism underlying the effect of lung carcinoma cell-derived exosomes on dendritic cell function.

Materials and Methods

C57BL/6 (B6) mice were randomly divided into five groups: control, dendritic cell (DC), DC-NC, DC-siMALAT1, and siMALAT1. Tumor cell proliferation was measured by Ki-67 staining. LLC cells were divided into control, NC, and si-MALAT1 groups, and exosomes secreted by each group were labeled as PEX, PEXN, and PEX-si, respectively. Exosomes and autophagic vacuoles were observed by transmission electron microscopy. MALAT1 expression in LLC, A549, and Beas-2b cells was examined by RT-PCR. The expression of IFN-γ, IL-12, IL-10, and TGF-β was observed by Elisa assay. Flow cytometry was used to observe the phagocytic function of DCs, costimulatory molecule expression, and T cell proliferation and differentiation. The protein expression of p-AKT, AKT, p-mTOR, mTOR, ALIX, TSG101, and CD63 was detected by Western blot.

Results

Compared with Beas-2b cells, MALAT1 expression was significantly increased in both LLC and A549 cells and in their secreted exosomes, and LLC cells showed the highest expression of MALAT1 (P < 0.05). Tumor cell proliferation and tumor volume were significantly decreased in the siMALAT1 and DC-siMALAT1 groups compared to those in the control group. DC phagocytosis, inflammatory response, costimulatory molecule expression, and T cell proliferation in the siMALAT1 and PEX-si groups were significantly enhanced (P < 0.05), while DC autophagy and T cell differentiation were reduced (P < 0.05). The levels of p-AKT, AKT, p-mTOR, and mTOR in the PEX and PEXN groups were increased compared with those in the control group, while those in the siMALAT1 and PEX-si groups were significantly decreased (P < 0.05).

Conclusion

Inhibition of MALAT1 expression in LLC-derived exosomes promoted DC function and T cell proliferation and suppressed DC autophagy and T cell differentiation, suggesting that MALAT1 inhibition may be a potential strategy for the clinical treatment of lung cancer.

Liquid Biopsies to Evaluate Immunogenicity of Gynecological/Breast Tumors: On the Way to Blood-Based Biomarkers for Immunotherapies

BACKGROUND

Despite the assumption of breast cancer (BC) as a cold, non-immunogenic tumor, immune checkpoint inhibitor (ICI) therapy is favorable for a subgroup of patients. Immunohistochemical assessment of the programmed cell death ligand 1 (PD-L1) is the only approved companion diagnostic for anti-PD-L1 therapy in metastatic triple-negative BC; however, challenges regarding the standardization of PD-L1 scoring in tumor tissue still remain. Consequently, to select patients most likely to respond to ICI, blood-based biomarkers are urgently needed.

SUMMARY AND KEY MESSAGES

Liquid biopsy, comprising circulating immune cells, circulating tumor cells and extracellular vesicles, as well as their surface proteins, is of high potential, and these analytes were already shown to be molecular correlates or regulators of the evasion from antitumoral immune reaction. Liquid biopsy, also enabling the evaluation of tumor mutational burden (TMB), microsatellite instability, and the T-cell receptor repertoire, allows serial sampling for monitoring purposes and reflects intra-tumoral heterogeneity which qualifies as marker for immunogenicity. Only a very few studies have already elucidated the potential of these analytes as biomarkers under ICI therapy. Nonetheless, the topic is of growing interest and has high relevance for the future. However, for clinical implementation, these multifarious analytes first need to pass robust standardization and validation procedures.

Extracellular Vesicles: New Endogenous Shuttles for miRNAs in Cancer Diagnosis and Therapy?

Extracellular Vesicles (EVs) represent a heterogeneous population of membranous cell-derived structures, including cargo-oriented exosomes and microvesicles. EVs are functionally associated with intercellular communication and play an essential role in multiple physiopathological conditions. Shedding of EVs is frequently increased in malignancies and their content, including proteins and nucleic acids, altered during carcinogenesis and cancer progression. EVs-mediated intercellular communication between tumor cells and between tumor and stromal cells can modulate, through cargo miRNA, the survival, progression, and drug resistance in cancer conditions. These consolidated suggestions and EVs’ stability in bodily fluids have led to extensive investigations on the potential employment of circulating EVs-derived miRNAs as tumor biomarkers and potential therapeutic vehicles. In this review, we highlight the current knowledge about circulating EVs-miRNAs in human cancer and the application limits of these tools, discussing their clinical utility and challenges in functions such as in biomarkers and instruments for diagnosis, prognosis, and therapy.

Mesenchymal stem cell-derived extracellular vesicle-based therapies protect against coupled degeneration of the central nervous and vascular systems in stroke

Stem cell-based treatments have been suggested as promising candidates for stroke. Recently, mesenchymal stem cells (MSCs) have been reported as potential therapeutics for a wide range of diseases. In particular, clinical trial studies have suggested MSCs for stroke therapy. The focus of MSC treatments has been directed towards cell replacement. However, recent research has lately highlighted their paracrine actions. The secretion of extracellular vesicles (EVs) is offered to be the main therapeutic mechanism of MSC therapy. However, EV-based treatments may provide a wider therapeutic window compared to tissue plasminogen activator (tPA), the traditional treatment for stroke. Exosomes are nano-sized EVs secreted by most cell types, and can be isolated from conditioned cell media or body fluids such as plasma, urine, and cerebrospinal fluid (CSF). Exosomes apply their effects through targeting their cargos such as microRNAs (miRs), DNAs, messenger RNAs, and proteins at the host cells, which leads to a shift in the behavior of the recipient cells. It has been indicated that exosomes, in particular their functional cargoes, play a significant role in the coupled pathogenesis and recovery of stroke through affecting the neurovascular unit (NVU). Therefore, it seems that exosomes could be utilized as diagnostic and therapeutic tools in stroke treatment. The miRs are small endogenous non-coding RNA molecules which serve as the main functional cargo of exosomes, and apply their effects as epigenetic regulators. These versatile non-coding RNA molecules are involved in various stages of stroke and affect stroke-related factors. Moreover, the involvement of aging-induced changes to specific miRs profile in stroke further highlights the role of miRs. Thus, miRs could be utilized as diagnostic, prognostic, and therapeutic tools in stroke. In this review, we discuss the roles of stem cells, exosomes, and their application in stroke therapy. We also highlight the usage of miRs as a therapeutic choice in stroke therapy.

Connexin-46 Contained in Extracellular Vesicles Enhance Malignancy Features in Breast Cancer Cells

Under normal conditions, almost all cell types communicate with their neighboring cells through gap junction channels (GJC), facilitating cellular and tissue homeostasis. A GJC is formed by the interaction of two hemichannels; each one of these hemichannels in turn is formed by six subunits of transmembrane proteins called connexins (Cx). For many years, it was believed that the loss of GJC-mediated intercellular communication was a hallmark in cancer development. However, nowadays this paradigm is changing. The connexin 46 (Cx46), which is almost exclusively expressed in the eye lens, is upregulated in human breast cancer, and is correlated with tumor growth in a Xenograft mouse model. On the other hand, extracellular vesicles (EVs) have an important role in long-distance communication under physiological conditions. In the last decade, EVs also have been recognized as key players in cancer aggressiveness. The aim of this work was to explore the involvement of Cx46 in EV-mediated intercellular communication. Here, we demonstrated for the first time, that Cx46 is contained in EVs released from breast cancer cells overexpressing Cx46 (EVs-Cx46). This EV-Cx46 facilitates the interaction between EVs and the recipient cell resulting in an increase in their migration and invasion properties. Our results suggest that EV-Cx46 could be a marker of cancer malignancy and open the possibility to consider Cx46 as a new therapeutic target in cancer treatment.

Cancer-Derived Exosomes: Their Role in Cancer Biology and Biomarker Development

Exosomes are a subset of tiny extracellular vesicles manufactured by all cells and are present in all body fluids. They are produced actively in tumor cells, which are released and utilized to facilitate tumor growth. Their characteristics enable them to assist major cancer hallmarks, leveraged by cancer cells in fostering cancer growth and spread while implementing ways to escape elimination from the host environment. This review updates on the latest progress on the roles of cancer-derived exosomes, of 30-100 nm in size, in deregulating paracrine trafficking in the tumor microenvironment and circulation. Thus, exosomes are being exploited in diagnostic biomarker development, with its potential in clinical applications as therapeutic targets utilized in exosome-based nanoparticle drug delivery strategies for cancer therapy. Ongoing studies were retrieved from PubMed^® and Scopus database and ClinicalTrials.gov registry for review, highlighting how cancer cells from entirely different cell lines rely on genetic information carried by their exosomes for homotypic and heterotypic intercellular communications in the microenvironment to favor proliferation and invasion, while establishing a pre-metastatic niche in welcoming cancer cells' arrival. We will elaborate on the trafficking of tumor-derived exosomes in fostering cancer proliferation, invasion, and metastasis in hematopoietic (leukemia and myeloma), epithelial (breast cancer), and mesenchymal (soft tissue sarcoma and osteosarcoma) cancers. Cancer-derived exosomal trafficking is observed in several types of liquid or solid tumors, confirming their role as cancer hallmark enabler. Their enriched genetic signals arising from their characteristic DNA, RNA, microRNA, and lncRNA, along with specific gene expression profiles, protein, or lipid composition carried by the exosomal cargo shed into blood, saliva, urine, ascites, and cervicovaginal lavage, are being studied as a diagnostic, prognostic, or predictive cancer biomarker. We reveal the latest research efforts in exploiting the use of nanoparticles to improve the overall cancer diagnostic capability in the clinic.

Exosomes: New insights into cancer mechanisms

Exosomes are mobile extracellular vesicles with a diameter 40 to 150 nm. They play a critical role in several processes such as the development of cancers, intercellular signaling, drug resistance mechanisms, and cell-to-cell communication by fusion onto the cell membrane of recipient cells. These vesicles contain endogenous proteins and both noncoding and coding RNAs (microRNA and messenger RNAs) that can be delivered to various types of cells. Furthermore, exosomes exist in body fluids such as plasma, cerebrospinal fluid, and urine. Therefore, they could be used as a novel carrier to deliver therapeutic nucleic-acid drugs for cancer therapy. It was recently documented that, hypoxia promotes exosomes secretion in different tumor types leading to the activation of vascular cells and angiogenesis. Cancer cell-derived exosomes (CCEs) have been used as prognostic and diagnostic markers in many types of cancers because exosomes are stable at 4°C and -70°C. CCEs have many functional roles in tumorigenesis, metastasis, and invasion. Consequently, this review presents the data about the therapeutic application of exosomes and the role of CCEs in cancer invasion, drug resistance, and metastasis.

Cancer Testis Antigen Promotes Triple Negative Breast Cancer Metastasis and is Traceable in the Circulating Extracellular Vesicles

Triple negative breast cancer (TNBC) has poor survival, exhibits rapid metastases, lacks targeted therapies and reliable prognostic markers. Here, we examined metastasis promoting role of cancer testis antigen SPANXB1 in TNBC and its utility as a therapeutic target and prognostic biomarker. Expression pattern of SPANXB1 was determined using matched primary cancer, lymph node metastatic tissues and circulating small extracellular vesicles (sEVs). cDNA microarray analysis of TNBC cells stably integrated with a metastasis suppressor SH3GL2 identified SPANXB1 as a potential target gene. TNBC cells overexpressing SH3GL2 exhibited decreased levels of both SPANXB1 mRNA and protein. Silencing of SPANXB1 reduced migration, invasion and reactive oxygen species production of TNBC cells. SPANXB1 depletion augmented SH3GL2 expression and decreased RAC-1, FAK, A-Actinin and Vinculin expression. Phenotypic and molecular changes were reversed upon SPANXB1 re-expression. SPANXB1 overexpressing breast cancer cells with an enhanced SPANXB1:SH3GL2 ratio achieved pulmonary metastasis within 5 weeks, whereas controls cells failed to do so. Altered expression of SPANXB1 was detected in the sEVs of SPANXB1 transduced cells. Exclusive expression of SPANXB1 was traceable in circulating sEVs, which was associated with TNBC progression. SPANXB1 represents a novel and ideal therapeutic target for blocking TNBC metastases due to its unique expression pattern and may function as an EV based prognostic marker to improve TNBC survival. Uniquely restricted expression of SPANXB1 in TNBCs, makes it an ideal candidate for targeted therapeutics and prognostication.

Basics and applications of tumor-derived extracellular vesicles

Extracellular vesicle (EV)-mediated intercellular communication acts as a critical culprit in cancer development. The selective packaging of oncogenic molecules renders tumor-derived EVs capable of altering the tumor microenvironment and thereby modulating cancer developments that may contribute to drug resistance and cancer recurrence. Moreover, the molecular and functional characteristics of cancer through its development and posttreatment evolve over time. Tumor-derived EVs are profoundly involved in this process and can, therefore, provide valuable real-time information to reflect dynamic changes occurring within the body. Because they bear unique molecular profiles or signatures, tumor-derived EVs have been highlighted as valuable diagnostic and predictive biomarkers as well as novel therapeutic targets. In addition, the use of an advanced EV-based drug delivery system for cancer therapeutics has recently been emphasized in both basic and clinical studies. In this review, we highlight comprehensive aspects of tumor-derived EVs in oncogenic processes and their potential clinical applications.

Extracellular vesicles induce minimal hepatotoxicity and immunogenicity

Extracellular vesicles (EVs) mediate cellular communication through the transfer of active biomolecules, raising interest in using them as biological delivery vehicles for therapeutic drugs. For drug delivery applications, it is important to understand the intrinsic safety and toxicity liabilities of EVs. Nanoparticles, including EVs, typically demonstrate significant accumulation in the liver after systemic administration in vivo. We confirmed uptake of EVs derived from Expi293F cells into HepG2 cells and did not detect any signs of hepatotoxicity measured by cell viability, functional secretion of albumin, plasma membrane integrity, and mitochondrial and lysosomal activity even at high exposures of up to 5 × 1010 EVs per mL. Whole genome transcriptome analysis was used to measure potential effects on the gene expression in the recipient HepG2 cells at 24 h following exposure to EVs. Only 0.6% of all genes were found to be differentially expressed displaying less than 2-fold expression change, with genes related to inflammation or toxicity being unaffected. EVs did not trigger any proinflammatory cytokine response in HepG2 cells. However, minor changes were noted in human blood for interleukin (IL)-8, IL-6, and monocyte chemotactic protein 1 (MCP-1). Administration of 5 × 1010 Expi293F-derived EVs to BALB/c mice did not result in any histopathological changes or increases of liver transaminases or cytokine levels, apart from a modest increase in keratinocyte chemoattractant (KC). The absence of any significant toxicity associated with EVs in vitro and in vivo supports the prospective use of EVs for therapeutic applications and for drug delivery.

Current Progresses of Exosomes as Cancer Diagnostic and Prognostic Biomarkers

Cancer related exosomes are nano-size membrane vesicles that play important roles in tumor microenvironment. Emerging evidence indicates that exosomes can load unique cargoes, including proteins and nucleic acids that reflect the condition of tumor. Therefore, exosomes are being used as diagnostic and prognostic biomarkers for various cancers. In this review, we describe the current progresses of cancer related exosomes, including their biogenesis, molecular contents, biological functions, sources where they are derived from, and methods for their detection. We will also discuss the current exosomal biomarkers and the utilization of them for early diagnosis and prognostics in cancer.

Extracellular Vesicles as Conduits of Non-Coding RNA Emission and Intercellular Transfer in Brain Tumors

Non-coding RNA (ncRNA) species have emerged in as molecular fingerprints and regulators of brain tumor pathogenesis and progression. While changes in ncRNA levels have been traditionally regarded as cell intrinsic there is mounting evidence for their extracellular and paracrine function. One of the key mechanisms that enables ncRNA to exit from cells is their selective packaging into extracellular vesicles (EVs), and trafficking in the extracellular space and biofluids. Vesicular export processes reduce intracellular levels of specific ncRNA in EV donor cells while creating a pool of EV-associated ncRNA in the extracellular space and biofluids that enables their uptake by other recipient cells; both aspects have functional consequences. Cancer cells produce several EV subtypes (exosomes, ectosomes), which differ in their ncRNA composition, properties and function. Several RNA biotypes have been identified in the cargo of brain tumor EVs, of which microRNAs are the most studied, but other species (snRNA, YRNA, tRNA, and lncRNA) are often more abundant. Of particular interest is the link between transforming oncogenes and the biogenesis, cargo, uptake and function of tumor-derived EV, including EV content of oncogenic RNA. The ncRNA repertoire of EVs isolated from cerebrospinal fluid and serum is being developed as a liquid biopsy platform in brain tumors.

Circulating pancreatic cancer exosomal RNAs for detection of pancreatic cancer

Diagnostic biomarkers for the early diagnosis of pancreatic cancer are needed to improve prognosis for this disease. The aim of this study was to investigate differences in the expression of four messenger RNAs (mRNAs: CCDC88A,ARF6, Vav3, and WASF2) and five small nucleolar RNAs (snoRNAs: SNORA14B,SNORA18,SNORA25,SNORA74A, and SNORD22) in serum of patients with pancreatic cancer and control participants for use in the diagnosis of pancreatic cancer. Results were compared with the expression of sialylated Lewis (a) blood group antigen CA19‐9, the standard clinical tumor biomarker. Reverse transcription quantitative real‐time PCR showed that all of the mRNAs and snoRNAs, except CCDC88A, were encapsulated in exosomes and secreted from cultured pancreatic cancer cells, and present in cell culture medium. In a discovery‐stage clinical study involving 27 pancreatic cancer patients and 13 controls, the area under the receiver operating characteristic curve (AUC) of two mRNAs (WASF2 and ARF6) and two snoRNAs (SNORA74A and SNORA25) was > 0.9 for distinguishing pancreatic cancer patients from controls; the AUC of CA19‐9 was 0.897. Comparing serum levels of WASF2,ARF6,SNORA74A,SNORA25, and CA19‐9 revealed that levels of WASF2 were the most highly correlated with the risk of pancreatic cancer. The AUCs of WASF2,ARF6,SNORA74A, and SNORA25 in serum from patients in the early stages of pancreatic cancer (stages 0, I, and IIA) were > 0.9, compared with an AUC of 0.93 for the level of CA19‐9. The results of this study suggest that WASF2,ARF6,SNORA74A, and SNORA25 may be useful tools for the early detection of pancreatic cancer. Monitoring serum levels of WASF2 mRNA may be particularly useful, as it was the most highly correlated with pancreatic cancer risk.

Molecular assessment of circulating exosomes toward liquid biopsy diagnosis of Ewing sarcoma family of tumors

Ewing sarcoma was first described in 1921 in the Proceedings of the New York Pathological Society by an eminent American pathologist from Cornell named James R. Ewing as a "diffuse endothelioma of bone." Since this initial description, more has been discovered regarding Ewing sarcoma and in the 1980's both Ewing sarcoma and peripheral primitive neuroectodermal tumors due to their similar features and shared identical genetic abnormality were grouped into a class of cancers entitled Ewing sarcoma family of tumors (ESFTs). Ewing sarcoma is the second most common pediatric osseous malignancy followed by osteosarcoma, with highest incidence among 10-20 years old. Ewing sarcoma is consistently associated with chromosomal translocation and functional fusion of the EWSR1 gene to any of several structurally related transcription factor genes of the E26 transformation-specific family. These tumor-specific molecular rearrangements are useful for primary diagnosis, may provide prognostic information, and present potential therapeutic targets. Therefore, ways to rapidly and efficiently detect these defining genomic alterations are of clinical relevance. Within the past decade, liquid biopsies including extracellular vesicles (EVs), have emerged as a promising alternative and/or complimentary approach to standard tumor biopsies. It was recently reported that fusion mRNAs from tumor-specific chromosome translocations can be detected in Ewing sarcoma cell-derived exosomes. Within this review, we overview the current advances in Ewing sarcoma and the opportunities and challenges in exploiting circulating exosomes, primarily small bioactive EVs (30-180 nm), as developing sources of biomarkers for diagnosis and therapeutic response monitoring in children and young adult patients with ESFT.

Functional Role of miRNAs in the Progression of Breast Ductal Carcinoma in Situ

miRNAs are small RNAs that influence gene expression by targeting mRNAs. Depending on the function of their target genes, miRNAs may regulate the expression of oncogenes and tumor suppressors, thereby contributing to the promotion or inhibition of tumor progression. Ductal carcinoma in situ (DCIS), although often diagnosed as breast cancer, is a potential precursor to invasive ductal carcinoma. Many of the genetic events required for the invasive progression of DCIS occur at the preinvasive stage, and these events include changes in the expression of miRNAs. Aberrant expression of miRNAs can influence specific oncogenic or tumor-suppressive pathways required for breast cancer progression. miRNAs in DCIS have been shown to influence hormone signaling, cell-cell adhesion, epithelial-to-mesenchymal transition, transforming growth factor β signaling, maintenance of cancer stem cells, and modulation of the extracellular matrix. Additionally, extracellular DCIS miRNAs, such as those found in exosomes, may promote invasive progression by modifying the tumor microenvironment. Here, we review the miRNAs that have been identified in DCIS and how they may contribute to the progression to invasive disease. We also touch on the current state of miRNA therapy development, including the current challenges, and discuss the key future perspectives for research into miRNA function for the purpose of miRNA therapy development for DCIS.

Exosomes Regulate the Transformation of Cancer Cells in Cancer Stem Cell Homeostasis

In different biological model systems, exosomes are considered mediators of cell-cell communication between different cell populations. Exosomes, as extracellular vesicles, participate in physiological and pathological processes by transmitting signaling molecules such as proteins, nucleic acids, and lipids. The tumor's microenvironment consists of many types of cells, including cancer stem cells and mesenchymal cells. It is well known that these cells communicate with each other and thereby regulate the progression of the tumor. Recent studies have provided evidence that exosomes mediate the interactions between different types of cells in the tumor microenvironment, providing further insight into how these cells interact through exosome signaling. Cancer stem cells are a small kind of heterogeneous cells that existed in tumor tissues or cancer cell lines. These cells possess a stemness phenotype with a self-renewal ability and multipotential differentiation which was considered the reason for the failure of conventional cancer therapies and tumor recurrence. However, a highly dynamic equilibrium was found between cancer stem cells and cancer cells, and this indicates that cancer stem cells are no more special target and blocking the transformation of cancer stem cells and cancer cells seem to be a more significant therapy strategy. Whether exosomes, as an information transforming carrier between cells, regulated cancer cell transformation in cancer stem cell dynamic equilibrium and targeting exosome signaling attenuated the formation of cancer stem cells and finally cure cancers is worthy of further study.

Failure to detect functional transfer of active K-Ras protein from extracellular vesicles into recipient cells in culture

Exosomes, extracellular nanovesicles that carry nucleic acids, lipids, and proteins, have been the subject of several studies to assess their ability to transfer functional cargoes to cells. We recently characterized extracellular nanovesicles released from glioblastoma cells that carry active Ras in complex with proteins regulating exosome biogenesis. Here, we investigated whether a functional transfer of Ras from exosomes to other cells can initiate intercellular signaling. We observed that treatment of serum-starved, cultured glioblastoma cells with exogenous glioblastoma exosomes caused a significant increase in cellular viability over time. Moreover, we detected fluorescent signal transfer from lipophilic dye-labeled exogenous glioblastoma exosomes into cultured glioblastoma cells. To probe possible signaling from cell-to-cell, we utilized bimolecular luciferase complementation to examine the ability of K-Ras in exosomes to interact with the Raf-Ras Binding domain (Raf-RBD) expressed in a recipient cell line. Although the K-Ras/Raf-RBD interaction was readily detectable upon co-expression in a single cell line, or following lysis of co-cultured cell lines separately expressing K-Ras and RBD, bearing in mind the limitations of our assay, we were unable to detect the interaction in the intact, co-cultured cell lines or upon treatment of the Raf-RBD-expressing cells with exosomes containing K-Ras. Furthermore, HA-Tag-BFP fused to the K-Ras hypervariable region and CAAX sequence failed to be transferred at significant levels from extracellular vesicles into recipient cells, but remained detectable in the cell supernatants even after 96 hours of culture of naïve cells with extracellular vesicles. We conclude that if transfer of functional K-Ras from extracellular vesicles into the cytoplasm of recipient cells occurs, it must do so at an extremely low efficiency and therefore is unlikely to initiate Ras-ERK MAP kinase pathway signaling. These results suggest that studies claiming functional transfer of protein cargoes from exosomes should be interpreted with caution.

Exosome-mediated cell-cell communication in tumor progression

Exosomes, which are 30-150 nm lipid bilayer vehicles, have been recognized as one of the most crucial components of the tumor microenvironment. Exosomes transfer specific lipid, nucleic acids, proteins and other bioactive molecules from the donor cells to the recipient cells. Accumulating evidence has suggested that cancer cells and the tumor associated stromal cells can release and receive exosomes, inside of which the components and amounts are greatly changed. Pioneering studies have revealed that these exosomes play essential roles in tumor progression. Here we summarize the recent advances in this field, by focusing on the exosome biogenesis in the cancer condition, and their biological function in angiogenesis, metastasis and chemo-resistance of tumor. The review would not only provide a summary of this field, but also insights and perspectives on exosome-based strategies in cancer diagnoses, prevention and therapy.

Emerging role of exosome signalling in maintaining cancer stem cell dynamic equilibrium

Cancer stem cells (CSCs) are a small subset of heterogeneous cells existed in tumour tissues or cancer cell lines with self-renewal and differentiation potentials. CSCs were considered to be responsible for the failure of conventional therapy and tumour recurrence. However, CSCs are not a static cell population, CSCs and non-CSCs are maintained in dynamic interconversion state by their self-differentiation and dedifferentiation. Therefore, targeting CSCs for cancer therapy is still not enough,exploring the mechanism of dynamic interconversion between CSCs and non-CSCs and blocking the interconversion seems to be imperative. Exosomes are 30-100 nm size in diameter extracellular vesicles (EVs) secreted by multiple living cells into the extracellular space. They contain cell-state-specific bioactive materials, including DNA, mRNA, ncRNA, proteins, lipids, etc. with their specific surface markers, such as, CD63, CD81, Alix, Tsg101, etc. Exosomes have been considered as information carriers in cell communication between cancer cells and non-cancer cells, which affect gene expressions and cellular signalling pathways of recipient cells by delivering their contents. Now that exosomes acted as information carriers, whether they played role in maintaining dynamic equilibrium state between CSCs and non-CSCs and their mechanism of activity are unknown. This review summarized the current research advance of exosomes' role in maintaining CSC dynamic interconversion state and their possible mechanism of action, which will provide a better understanding the contribution of exosomes to dedifferentiation and stemness acquisition of non-CSCs, and highlight that exosomes might be taken as the attractive target approaches for cancer therapeutics.

Perspective: bidirectional exosomal transport between cancer stem cells and their fibroblast-rich microenvironment during metastasis formation

Carcinomas are complex structures composed of hierarchically organized distinct cell populations such as cancer stem cells and non-stem (bulk) cancer cells. Their genetic/epigenetic makeup and the dynamic interplay between the malignant cell populations and their stromal fibroblasts are important determinants of metastatic tumor invasion. Important mediators of these interactions are the small, membrane-enclosed extracellular vesicles, in particular exosomes. Both cancer cell and fibroblast-derived exosomes carry a set of regulatory molecules, including proteins and different species of RNA, which cooperatively support metastatic tumor spread. Here, we briefly overview potential links between cancer stem cells and the exosome-mediated fibroblast-enriched metastatic niche formation to discuss their role in the promotion of tumor growth and metastatic expansion in breast carcinoma models.

RNA Profiles of Circulating Tumor Cells and Extracellular Vesicles for Therapy Stratification of Metastatic Breast Cancer Patients

BACKGROUND

Liquid biopsies are discussed to provide surrogate markers for therapy stratification and monitoring. We compared messenger RNA (mRNA) profiles of circulating tumor cells (CTCs) and extracellular vesicles (EVs) in patients with metastatic breast cancer (MBC) to estimate their utility in therapy management.

METHODS

Blood was collected from 35 hormone receptor-positive/HER2-negative patients with MBC at the time of disease progression and at 2 consecutive staging time points. CTCs were isolated from 5 mL of blood by positive immunomagnetic selection, and EVs from 4 mL of plasma by a membrane affinity-based procedure. mRNA was reverse transcribed, preamplified, and analyzed for 18 genes by multimarker quantitative polymerase chain reaction (qPCR) assays. RNA profiles were normalized to healthy donor controls (n = 20), and results were correlated with therapy outcome.

RESULTS

There were great differences in mRNA profiles of EVs and CTCs, with only 5% (21/403) of positive signals identical in both fractions. Transcripts involved in the PI3K signaling pathway were frequently overexpressed in CTCs, and AURKA, PARP1, and SRC signals appeared more often in EVs. Of all patients, 40% and 34% showed ERBB2 and ERBB3 signals, respectively, in CTCs, which was significantly associated with disease progression (P = 0.007). Whereas MTOR signals in CTCs significantly correlated with response (P = 0.046), signals in EVs indicated therapy failure (P = 0.011). The presence of AURKA signals in EVs seemed to be a marker for the indication of unsuccessful treatment of bone metastasis.

CONCLUSIONS

These results emphasize the potential of CTCs and EVs for therapy monitoring and the need for critical evaluation of the implementation of any liquid biopsy in clinical practice.

Extracellular vesicles as circulating cancer biomarkers: opportunities and challenges

Extracellular vesicles (EVs) are small, lipid-bound particles containing nucleic acid and protein cargo which are excreted from cells under a variety of normal and pathological conditions. EVs have garnered substantial research interest in recent years, due to their potential utility as circulating biomarkers for a variety of diseases, including numerous types of cancer. The following review will discuss the current understanding of the form and function of EVs, their specific role in cancer pathogenesis and their potential for non-invasive disease diagnosis and/or monitoring. This review will also highlight several key issues for this field, including the importance of implementing robust and reproducible sample handling protocols, and the challenge of extracting an EV-specific biomarker signal from a complex biological background.

Roles of Extracellular Vesicles in Metastatic Breast Cancer

Cells can secrete extracellular vesicles (EVs) to communicate with neighboring or distant cells by EVs which are composed of a lipid bilayer containing transmembrane proteins and enclosing cytosolic proteins, lipids, and nucleic acids. Breast Cancer is the most frequently diagnosed malignancy with more than 1 million new cases each year and ranks the leading cause of cancer mortality in women worldwide. In this review, we will discuss recent progresses of the roles and mechanisms of cancer-derived EVs in metastatic breast cancer, with a special attention on tumor microenvironment construction, progression, and chemo/radiotherapy responses. This review also covers EV roles as biomarker and therapeutic target in clinical application.

The multifaceted role of exosomes in cancer progression: diagnostic and therapeutic implications [corrected]

BACKGROUND

Recent advances in cancer biology have highlighted the relevance of exosomes and nanovesicles as carriers of genetic and biological messages between cancer cells and their immediate and/or distant environments. It has been found that these molecular cues may play significant roles in cancer progression and metastasis. Cancer cells secrete exosomes containing diverse molecules that can be transferred to recipient cells and/or vice versa to induce a plethora of biological processes, including angiogenesis, metastasis formation, therapeutic resistance, epithelial-mesenchymal transition and epigenetic/stemness (re)programming. While exosomes interact with cells within the tumour microenvironment to promote tumour growth, these vesicles can also facilitate the process of distant metastasis by mediating the formation of pre-metastatic niches. Next to their tumour promoting effects, exosomes have been found to serve as potential tools for cancer diagnosis and therapy. The ease of isolating exosomes and their content from different body fluids has led to the identification of diagnostic and prognostic biomarker signatures, as well as to predictive biomarker signatures for therapeutic responses. Exosomes can also be used as cargos to deliver therapeutic anti-cancer drugs, and they can be engineered to serve as vaccines for immunotherapy. Additionally, it has been found that inhibition of exosome secretion, and thus the transfer of oncogenic molecules, holds promise for inhibiting tumour growth. Here we provide recent information on the diverse roles of exosomes in various cellular and systemic processes governing cancer progression, and discuss novel strategies to halt this progression using exosome-based targeted therapies and methods to inhibit exosome secretion and the transfer of pro-tumorigenic molecules.

CONCLUSIONS

This review highlights the important role of exosomes in cancer progression and its implications for (non-invasive) diagnostics and the development of novel therapeutic strategies, as well as its current and future applications in clinical trials.

Glycosylated extracellular vesicles released by glioblastoma cells are decorated by CCL18 allowing for cellular uptake via chemokine receptor CCR8

Cancer cells release extracellular vesicles (EVs) that contain functional biomolecules such as RNA and proteins. EVs are transferred to recipient cancer cells and can promote tumour progression and therapy resistance. Through RNAi screening, we identified a novel EV uptake mechanism involving a triple interaction between the chemokine receptor CCR8 on the cells, glycans exposed on EVs and the soluble ligand CCL18. This ligand acts as bridging molecule, connecting EVs to cancer cells. We show that glioblastoma EVs promote cell proliferation and resistance to the alkylating agent temozolomide (TMZ). Using in vitro and in vivo stem-like glioblastoma models, we demonstrate that EV-induced phenotypes are neutralised by a small molecule CCR8 inhibitor, R243. Interference with chemokine receptors may offer therapeutic opportunities against EV-mediated cross-talk in glioblastoma.

Concentration of circulating miRNA-containing particles in serum enhances miRNA detection and reflects CRC tissue-related deregulations

The emerging potential of miRNAs as biomarkers for cancer detection demands parallel evaluation of strategies for reliable identification of disease-related signatures from easily accessible and pertinent body compartments. Here, we addressed whether efficient concentration of circulating miRNA-carrying particles is a rationale for miRNA biomarker discovery. We systematically compared miRNA signatures in 93 RNA preparations from three serum entities (whole serum, particle-concentrated, and particle-depleted fractions) and corresponding tissue samples from patients with colorectal cancer (CRC) as a model disease. Significant differences between whole sera and particle-concentrated serum fractions of CRC patients emerged for 45 of 742 tested miRNAs. Twenty-eight of these 45 miRNAs were differentially expressed between particle-concentrated serum fractions of metastatic CRC- and healthy individuals. Over half of these candidates (15 of 28) showed deregulations only in concentrated serum fractions, but not in whole sera, compared to the respective controls.Our results also provided evidence of a consistent downregulation of miR-486 and miR-92a, and further showed a possible "strand-specific" deregulation of extracellular miRNAs in CRC. More importantly, most of the identified miRNAs in the enriched sera reflected the patterns of the corresponding tumor tissues and showed links to cancer-related inflammation. Further investigation of seven serum pools revealed a subset of potential extracellular miRNA candidates to be implicated in both neoplastic and inflammatory bowel disease.Our findings demonstrate that enrichment and sensitive detection of miRNA carriers is a promising approach to detect CRC-related pathological changes in liquid biopsies, and has potential for clinical diagnostics.