Exosome-Mediated Transfer of Cancer Cell Resistance to Antiestrogen Drugs

Exosomal signaling in cancer metastasis: Molecular insights and therapeutic opportunities

Exosomes are membrane-bound extracellular vesicles that play a role in exchanging biological products across membranes and serve as intermediaries in intercellular communication to maintain normal homeostasis. Numerous molecules, including lipids, proteins, and nucleic acids are enclosed in exosomes. Exosomes are constantly released into the extracellular environment and exhibit distinct characteristics based on the secreted cells that produce them. Exosome-mediated cell-to-cell communication has reportedly been shown to affect multiple cancer hallmarks, such as immune response modulation, pre-metastatic niche formation, angiogenesis, stromal cell reprogramming, extracellular matrix architecture remodeling, or even drug resistance, and eventually the development and metastasis of cancer cells. Exosomes can be used as therapeutic targets and possible diagnostic biomarkers by selectively loading oncogenic molecules into them. We highlight the important roles that exosomes play in cancer development in this review, which may lead to the development of fresh approaches for future clinical uses.

Tumour-derived exosome SNHG17 induced by oestrogen contributes to ovarian cancer progression via the CCL13-CCR2-M2 macrophage axis

Oestrogen is known to be strongly associated with ovarian cancer. There was much work to show the importance of lncRNA SNHG17 in ovarian cancer. However, no study has revealed the molecular regulatory mechanism and functional effects between oestrogen and SNHG17 in the development and metastasis of ovarian cancer. In this study, we found that SNHG17 expression was significantly increased in ovarian cancer and positively correlated with oestrogen treatment. Oestrogen could promote M2 macrophage polarization as well as ovarian cancer cells SKOV3 and ES2 cell exosomal SNHG17 expression. When exposure to oestrogen, exosomal SNHG17 promoted ovarian cancer cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) in vitro, and tumour growth and lung metastasis in vivo by accelerating M2-like phenotype of macrophages. Mechanically, exosomal SNHG17 could facilitate the release of CCL13 from M2 macrophage via the PI3K-Akt signalling pathway. Moreover, CCL13-CCR2 axis was identified to be involved in ovarian cancer tumour behaviours driven by oestrogen. There results demonstrate a novel mechanism that exosomal SNHG17 exerts an oncogenic effect on ovarian cancer via the CCL13-CCR2-M2 macrophage axis upon oestrogen treatment, of which SNHG17 may be a potential biomarker and therapeutic target for ovarian cancer responded to oestrogen.

Drug resistance in breast cancer is based on the mechanism of exocrine non-coding RNA

Breast cancer (BC) ranks first among female malignant tumors and involves hormonal changes and genetic as well as environmental risk factors. In recent years, with the improvement of medical treatment, a variety of therapeutic approaches for breast cancer have emerged and have strengthened to accommodate molecular diversity. However, the primary way to improve the effective treatment of breast cancer patients is to overcome treatment resistance. Recent studies have provided insights into the mechanisms of resistance to exosome effects in BC. Exosomes are membrane-bound vesicles secreted by both healthy and malignant cells that facilitate intercellular communication. Specifically, exosomes released by tumor cells transport their contents to recipient cells, altering their properties and promoting oncogenic components, ultimately resulting in drug resistance. As important coordinators, non-coding RNAs (ncRNAs) are involved in this process and are aberrantly expressed in various human cancers. Exosome-derived ncRNAs, including microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), have emerged as crucial components in understanding drug resistance in breast cancer. This review provides insights into the mechanism of exosome-derived ncRNAs in breast cancer drug resistance, thereby suggesting new strategies for the treatment of BC.

Biological Roles and Clinical Applications of Exosomes in Breast Cancer: A Brief Review

Breast cancer (BC) is a global health risk for women and has a high prevalence rate. The drug resistance, recurrence, and metastasis of BC affect patient prognosis, thus posing a challenge to scientists. Exosomes are extracellular vesicles (EVs) that originate from various cells; they have a double-layered lipid membrane structure and contain rich biological information. They mediate intercellular communication and have pivotal roles in tumor development, progression, and metastasis and drug resistance. Exosomes are important cell communication mediators in the tumor microenvironment (TME). Exosomes are utilized as diagnostic and prognostic biomarkers for estimating the treatment efficacy of BC and have the potential to function as tools to enable the targeted delivery of antitumor drugs. This review introduces recent progress in research on how exosomes influence tumor development and the TME. We also present the research progress on the application of exosomes as prognostic and diagnostic biomarkers and drug delivery tools.

Research progress of exosomes in drug resistance of breast cancer

Since breast cancer is a heterogeneous disease, there are currently a variety of treatment methods available, including chemotherapy, endocrine therapy, molecular targeted therapy, immunotherapy, radiation therapy, etc. Breast cancer recurrence and metastasis, despite many treatment modalities, constitute a considerable threat to patients' survival time and pose a clinical challenge that is difficult to tackle precisely. Exosomes have a very special and crucial role in the treatment of drug resistance in breast cancer as a carrier of intercellular communication in the tumor microenvironment. Exosomes and breast cancer treatment resistance have been linked in a growing number of clinical investigations in recent years. This paper covers the status of research on exosomes in the treatment of breast cancer drug resistance and offers theoretical guidance for investigating new strategies to treat breast cancer drug resistance.

Tumor-derived exosomes RNA expression profiling identifies the prognosis, immune characteristics, and treatment in HR+/HER2-breast cancer

Exosomes play crucial roles in intercellular communication and are involved in the onset and progression of various types of cancers, including breast cancer. However, the RNA composition of breast cancer-derived exosomes has not been comprehensively explored. We conducted microarray assays on exosomes isolated from breast cancer and healthy breast epithelial cells from three patients with hormone receptor (HR) +/ human epidermal growth factor receptor (HER2) - breast cancer and identified 817 differentially expressed genes (DEGs). Among these, 315 upregulated tumor-derived exosome genes (UTEGs) were used to classify HR+/HER2- breast cancers into two categories, revealing a difference in survival rates between the groups. We developed and validated a novel prognostic exosome score (ES) model consisting of four UTEGs that provides a refined prognosis prediction in HR+/HER2-breast cancer. ES reflects various immune-related features, including somatic variation, immunogenicity, and tumor immune infiltrate composition. Our findings indicate a considerable positive correlation between the ES and drug sensitivity values for vincristine, paclitaxel, and docetaxel. However, ES was remarkably higher in the endocrine therapy non-responder group than in the responder group. Immunohistochemistry confirmed the remarkable expression of the four model genes in tumor tissues, and their expression in MCF-7 cell exosomes was higher than that in MCF10A cells, as verified via qPCR. In summary, tumor-derived exosome genes provide novel insights into the subtyping, prognosis, and treatment of HR+/HER2-breast cancer.

Identification of Exo-miRNAs: A Summary of the Efforts in Translational Studies Involving Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) accounts for about 10-15% of all breast cancers (BC) in the US and its diagnosis is associated with poor survival outcomes. A better understanding of the disease etiology is crucial to identify target treatment options to improve patient outcomes. The role of exo-miRNAs in TNBC has been studied for more than two decades. Although some studies have identified exo-miR candidates in TNBC using clinical samples, consensus regarding exo-miR candidates has not been achieved. The purpose of this review is to gather information regarding exo-miR candidates reported in TNBC translational studies along with the techniques used to isolate and validate the potential targets. The techniques suggested in this review are based on the use of commercially available materials for research and clinical laboratories. We expect that the information included in this review can add additional value to the recent efforts in the development of a liquid biopsy to identify TNBC cases and further improve their survival outcomes.

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.

Exosomes: The Role in Tumor Tolerance and the Potential Strategy for Tumor Therapy

Drug and radiotherapy resistance is the primary cause of treatment failure and poor prognosis in patients with tumors. Exosomes are extracellular vesicles loaded with substances such as nucleic acids, lipids, and proteins that transmit information between cells. Studies have found that exosomes are involved in tumor therapy resistance through drug efflux, promotion of drug resistance phenotypes, delivery of drug-resistance-related molecules, and regulation of anti-tumor immune responses. Based on their low immunogenicity and high biocompatibility, exosomes have been shown to reduce tumor therapy resistance by loading nucleic acids, proteins, and drugs inside xosomes or expressing tumor-specific antigens, target peptides, and monoclonal antibodies on their phospholipid bimolecular membranes. Consequently, future research on genetically engineered exosomes is expected to eliminate resistance to tumor treatment, improving the overall prognosis of patients with tumors.

The Role of Exosomes in Human Carcinogenesis and Cancer Therapy-Recent Findings from Molecular and Clinical Research

Exosomes are biological nanoscale spherical lipid bilayer vesicles, 40-160 nm in diameter, produced by most mammalian cells in both physiological and pathological conditions. Exosomes are formed via the endosomal sorting complex required for transport (ESCRT). The primary function of exosomes is mediating cell-to-cell communication. In terms of cancer, exosomes play important roles as mediators of intercellular communication, leading to tumor progression. Moreover, they can serve as biomarkers for cancer detection and progression. Therefore, their utilization in cancer therapies has been suggested, either as drug delivery carriers or as a diagnostic tool. However, exosomes were also reported to be involved in cancer drug resistance via transferring information of drug resistance to sensitive cells. It is important to consider the current knowledge regarding the role of exosomes in cancer, drug resistance, cancer therapies, and their clinical application in cancer therapies.

MicroRNA-484 / Akt axis in the regulation of breast cancer cells sensitivity to antitumor drugs

The development of acquired resistance of malignant tumors to specific drugs, such as target and hormonal drugs, is usually associated with a rearrangement of the intracellular signaling network and activation of unblocked growth pathways. Epigenetic regulators, in particular, non-coding miRNAs that control the level of expression of specific signaling proteins, are directly involved in the development and maintenance of such changes. We have previously shown that the development of resistance of breast cancer cells to mTOR (mammalian target of rapamycin) inhibitors and hormonal drugs is accompanied by constitutive activation of protein kinase Akt, the key anti-apoptotic protein.Aim. To study the role of microRNAs in the regulation of Akt expression and the formation of a resistant phenotype of breast cancer cells.We have shown that Akt activation in the tamoxifen- or rapamycin-resistant MCF-7 sublines is associated with a decrease in the level of miRNA-484, one of the Akt suppressors. Transfection of microRNA-484 into MCF-7 cells does not affect the activity of estrogen signaling, but leads to a marked decrease in Akt expression and is accompanied by an increase in cell sensitivity to tamoxifen and rapamycin. The obtained data demonstrate the involvement of the miRNA-484 / Akt axis in the breast cancer cells’ sensitization to target and hormonal drugs, which allows us to consider miRNA-484 as a potential candidate for drug development to cure resistant cancers.

The history of small extracellular vesicles and their implication in cancer drug resistance

Small extracellular vesicles (EVs) in the last 20 years are demonstrated to possess promising properties as potential new drug delivery systems, biomarkers, and therapeutic targets. Moreover, EVs are described to be involved in the most important steps of tumor development and progression including drug resistance. The acquired or intrinsic capacity of cancer cells to resist chemotherapies is one of the greatest obstacles to overcome to improve the prognosis of many patients. EVs are involved in this mechanism by exporting the drugs outside the cells and transferring the drug efflux pumps and miRNAs in recipient cells, in turn inducing drug resistance. In this mini-review, the main mechanisms by which EVs are involved in drug resistance are described, giving a rapid and clear overview of the field to the readers.

Exosome-Mediated Response to Cancer Therapy: Modulation of Epigenetic Machinery

Exosomes, the extracellular vesicles produced in the endosomal compartments, facilitate the transportation of proteins as well as nucleic acids. Epigenetic modifications are now considered important for fine-tuning the response of cancer cells to various therapies, and the acquired resistance against targeted therapies often involves dysregulated epigenetic modifications. Depending on the constitution of their cargo, exosomes can affect several epigenetic events, thus impacting post-transcriptional regulations. Thus, a role of exosomes as facilitators of epigenetic modifications has come under increased scrutiny in recent years. Exosomes can deliver methyltransferases to recipient cells and, more importantly, non-coding RNAs, particularly microRNAs (miRNAs), represent an important exosome cargo that can affect the expression of several oncogenes and tumor suppressors, with a resulting impact on cancer therapy resistance. Exosomes often harbor other non-coding RNAs, such as long non-coding RNAs and circular RNAs that support resistance. The exosome-mediated transfer of all this cargo between cancer cells and their surrounding cells, especially tumor-associated macrophages and cancer-associated fibroblasts, has a profound effect on the sensitivity of cancer cells to several chemotherapeutics. This review focuses on the exosome-induced modulation of epigenetic events with resulting impact on sensitivity of cancer cells to various therapies, such as, tamoxifen, cisplatin, gemcitabine and tyrosine kinase inhibitors. A better understanding of the mechanisms by which exosomes can modulate response to therapy in cancer cells is critical for the development of novel therapeutic strategies to target cancer drug resistance.

Overview and Update on Extracellular Vesicles: Considerations on Exosomes and Their Application in Modern Medicine

In recent years, there has been a rapid growth in the knowledge of cell-secreted extracellular vesicle functions. They are membrane enclosed and loaded with proteins, nucleic acids, lipids, and other biomolecules. After being released into the extracellular environment, some of these vesicles are delivered to recipient cells; consequently, the target cell may undergo physiological or pathological changes. Thus, extracellular vesicles as biological nano-carriers, have a pivotal role in facilitating long-distance intercellular communication. Understanding the mechanisms that mediate this communication process is important not only for basic science but also in medicine. Indeed, extracellular vesicles are currently seen with immense interest in nanomedicine and precision medicine for their potential use in diagnostic, prognostic, and therapeutic applications. This paper aims to summarize the latest advances in the study of the smallest subtype among extracellular vesicles, the exosomes. The article is divided into several sections, focusing on exosomes' nature, characteristics, and commonly used strategies and methodologies for their separation, characterization, and visualization. By searching an extended portion of the relevant literature, this work aims to give a quick outline of advances in exosomes' extensive nanomedical applications. Moreover, considerations that require further investigations before translating them to clinical applications are summarized.

Applications of Extracellular Vesicles in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive and refractory subtype of breast cancer, often occurring in younger patients with poor clinical prognosis. Given the current lack of specific targets for effective intervention, the development of better treatment strategies remains an unmet medical need. Over the last decade, the field of extracellular vesicles (EVs) has grown tremendously, offering immense potential for clinical diagnosis/prognosis and therapeutic applications. While TNBC-EVs have been shown to play an important role in tumorigenesis, chemoresistance and metastasis, they could be repurposed as potential biomarkers for TNBC diagnosis and prognosis. Furthermore, EVs from various cell types can be utilized as nanoscale drug delivery systems (NDDS) for TNBC treatment. Remarkably, EVs generated from specific immune cell subsets have been shown to delay solid tumour growth and reduce tumour burden, suggesting a new immunotherapy approach for TNBC. Intrinsically, EVs can cross the blood-brain barrier (BBB), which holds great potential to treat the brain metastases diagnosed in one third of TNBC patients that remains a substantial clinical challenge. In this review, we present the most recent applications of EVs in TNBC as diagnostic/prognostic biomarkers, nanoscale drug delivery systems and immunotherapeutic agents, as well as discuss the associated challenges and future directions of EVs in cancer immunotherapy.

Enigmatic role of exosomes in breast cancer progression and therapy

Breast cancer (BC) is reported to be the leading cause of mortality in females worldwide. At the beginning of the year 2021, about 7.8 million women were diagnosed with BC in past 5 years. High prevalence and poor neoadjuvant chemotherapeutic efficacy has motivated the scientists around the globe to investigate alternative management strategies. In recent years, there has been an exponential rise in the scientific studies reporting the role of tumor derived exosomes (TDEs) in the BC pathophysiology and management. TDEs play an important role in the intercellular communication and transportation of biomolecules. This manuscript reviews the role of exosomes in the BC pathophysiology, diagnosis, and therapy. Role of TDEs in the mechanistic pathways of BC metastasis, immunosuppression, migration, dormancy and chemo-resistance is extensively reviewed. We have also highlighted the epigenetic modulations orchestrated by exosomal miRNAs and long noncoding RNAs (lnc RNAs) in the BC environment. Liquid biopsies analyzing blood circulating exosomes for early and accurate detection of the BC have been discussed. Characterization of exosomes, strategies to use them in BC chemotherapy, BC immunotherapy and potential challenges that will present themselves in translating exosomes based technologies to market are discussed.

Plasma Exosomes of Patients with Breast and Ovarian Tumors Contain an Inactive 20S Proteasome

Exosomes are directly involved in governing of physiological and pathological conditions of an organism through the transfer of information from producing to receiving cells. It can be assumed that exosomes are one of the key players of tumor dissemination since they are very stable and small enough to penetrate from various tissues into biological fluids and then back, thus interacting with tissue target cells. We evaluated the enzymatic activity and the level of 20S proteasome in tissue and exosomes of healthy females (n = 39) and patients with ovarian (n = 50) and breast (n = 108) tumors to reveal the critical role of exosomal cargo in the mediation of different types of metastases. Exosomes from plasma and ascites were isolated and characterized in according to International Society for Extracellular Vesicles guidelines. The level of 20S proteasome in tissue and exosomes was determined using Western blot analysis. Chymotrypsin- and caspase-like (ChTL and CL, respectively) peptidase activities of the proteasomes were determined using fluorogenic Suc-LLVY-AMC and Cbz-LLG-AMC substrates, respectively. We observed increased levels of 20S proteasome in ovarian cancer tissue and luminal B subtype breast cancer tissue as well as in plasma exosomes from cancer patients. Moreover, the level of the 20S proteasome in plasma exosomes and ascites exosomes in patients with ovarian tumors is comparable and higher in ovarian cancer patients with low volume ascites than in patients with moderate and high-volume ascites. We also found increased ChTL and CL activities in breast cancer and ovarian cancer tissues, as well as in peritoneal metastases in ovarian cancer, while proteasomal activity in exosomes from plasma of healthy females and all patients, as well as from ascites of ovarian tumor patients were lower than detection limit of assay. Thus, regardless of the type of tumor metastasis (lymphogenous or peritoneal), the exosomes of cancer patients were characterized by an increased level of 20S proteasome, which do not exhibit enzymatic activity.

Towards Unravelling the Role of ERα-Targeting miRNAs in the Exosome-Mediated Transferring of the Hormone Resistance

Hormone therapy is one of the most effective breast cancer treatments, however, its application is limited by the progression of hormonal resistance, both primary or acquired. The development of hormonal resistance is caused either by an irreversible block of hormonal signalling (suppression of the activity or synthesis of hormone receptors), or by activation of oestrogen-independent signalling pathways. Recently the effect of exosome-mediated intercellular transfer of hormonal resistance was revealed, however, the molecular mechanism of this effect is still unknown. Here, the role of exosomal miRNAs (microRNAs) in the transferring of hormonal resistance in breast cancer cells has been studied. The methods used in the work include extraction, purification and RNAseq of miRNAs, transfection of miRNA mimetics, immunoblotting, reporter analysis and the MTT test. Using MCF7 breast cancer cells and MCF7/T tamoxifen-resistant sub-line, we have found that some miRNAs, suppressors of oestrogen receptor signalling, are overexpressed in the exosomes of the resistant breast cancer cells. The multiple (but not single) transfection of one of the identified miRNA, miR-181a-2, into oestrogen-dependent MCF7 cells induced the irreversible tamoxifen resistance associated with the continuous block of the oestrogen receptor signalling and the activation of PI3K/Akt pathway. We suppose that the miRNAs-ERα suppressors may act as trigger agents inducing the block of oestrogen receptor signalling and breast cancer cell transition to an aggressive oestrogen-independent state.

Estrogen inhibits the growth of colon cancer in mice through reversing extracellular vesicle-mediated immunosuppressive tumor microenvironment

Postmenopausal women taking estrogen supplements are at a lower risk of advanced colorectal cancer, but the underlying mechanism remains unclear. Thus, this study examined the role of estrogen in colorectal cancer. Estrogen receptor expression levels in in situ colorectal cancer tissue from female patients increased significantly, indicating their estrogen sensitivity. Compared with the sham-operated group, the growth of MC38 tumors was enhanced in ovariectomized mice, which was reversed in ovariectomized mice with E2 supplementation. The PD-L1⁺ M2-like macrophage, regulatory T (Treg) cell, and myeloid-derived suppressor cell (MDSC) populations significantly increased, and the population of cytotoxic CD8⁺ T cells declined in MC38 tumors in ovariectomized mice, which were all reversed in ovariectomized mice with E2 supplementation. MC38 cell-derived extracellular vesicles (MC38-EVs), but not EVs derived from MC38 cells treated with E2 (E2-MC38-EVs), were involved in the establishment of immunosuppressive tumor microenvironment. E2-MC38-EVs contained lower TGF-β1 levels and were less capable of inducing Treg cells than MC38-EVs in vitro. Overall, these results show that estrogen treatment prevents MC38 tumor growth via regulating the tumor immune microenvironment through MC38-EVs.

miR-224-5p Carried by Human Umbilical Cord Mesenchymal Stem Cells-Derived Exosomes Regulates Autophagy in Breast Cancer Cells via HOXA5

Objective: In this study, we focused on the potential mechanism of miRNAs carried by human umbilical cord mesenchymal stem cells-derived exosomes (hUCMSCs-exo) in breast cancer (BC).

Methods: RT-qPCR was conducted for the expression of miR-224-5p and HOXA5 in tissues and cells. After co-culture of exosomes and MCF-7 or MDA-MB-231 cells, the cell proliferation was observed by MTT and cell colony formation assay, while apoptosis was measured by flow cytometry. In addition, the expression of HOXA5 and autophagy pathway-related proteins LC3-II, Beclin-1 and P62 was detected by western blotting. And immunofluorescence was applied for detection of LC3 spots. The binding of miR-224-5p to HOXA5 was verified by the luciferase reporter gene assay and RNA-binding protein immunoprecipitation assay. Finally, in vivo experiment was performed to investigate the effect of miR-224-5p on BC growth.

Results: MiR-224-5p was up-regulated and HOXA5 was down-regulated in BC tissues and cells. HOXA5 was confirmed to be the target gene of miR-224-5p. MiR-224-5p carried by hUCMSCs-exo was able to promote the proliferation and autophagy of BC cells, while inhibited apoptosis. Bases on xenograft models in nude mice, it was also revealed that miR-224-5p carried by hUCMSCs-exo could regulate autophagy and contribute to the occurrence and development of BC in vivo.

Conclusion: MiR-224-5p carried by hUCMSCs-exo can regulate autophagy via inhibition of HOXA5, thus affecting the proliferation and apoptosis of BC cells.

Secretion of Mutant DNA and mRNA by the Exosomes of Breast Cancer Cells

Exosomes are the small vesicles that are secreted by different types of normal and tumour cells and can incorporate and transfer their cargo to the recipient cells. The main goal of the present work was to study the tumour exosomes’ ability to accumulate the parent mutant DNA or RNA transcripts with their following transfer to the surrounding cells. The experiments were performed on the MCF7 breast cancer cells that are characterized by the unique coding mutation in the PIK3CA gene. Using two independent methods, Sanger sequencing and allele-specific real-time PCR, we revealed the presence of the fragments of the mutant DNA and RNA transcripts in the exosomes secreted by the MCF7 cells. Furthermore, we demonstrated the MCF7 exosomes’ ability to incorporate into the heterologous MDA-MB-231 breast cancer cells supporting the possible transferring of the exosomal cargo into the recipient cells. Sanger sequencing of the DNA from MDA-MB-231 cells (originally bearing a wild type of PIK3CA) treated with MCF7 exosomes showed no detectable amount of mutant DNA or RNA; however, using allele-specific real-time PCR, we revealed a minor signal from amplification of a mutant allele, showing a slight increase of mutant DNA in the exosome-treated MDA-MB-231 cells. The results demonstrate the exosome-mediated secretion of the fragments of mutant DNA and mRNA by the cancer cells and the exosomes’ ability to transfer their cargo into the heterologous cells.

Molecular Mechanisms of Endocrine Resistance in Estrogen-Positive Breast Cancer

The estrogen receptor is a vital receptor for therapeutic targets in estrogen receptor-positive breast cancer. The main strategy for the treatment of estrogen receptor-positive breast cancers is blocking the estrogen action on estrogen receptors by endocrine therapy but this can be restricted via endocrine resistance. Endocrine resistance occurs due to both de novo and acquired resistance. This review focuses on the mechanisms of the ligand-dependent and ligand-independent pathways and other coregulators, which are responsible for endocrine resistance. It concludes that combinatorial drugs that target different signaling pathways and coregulatory proteins together with endocrine therapy could be a novel therapeutic modality to stop endocrine resistance.

The Emerging Role of Extracellular Vesicles in Endocrine Resistant Breast Cancer

Simple Summary

Two-thirds of breast cancer patients present an estrogen receptor–positive tumor at diagnosis, and the main treatment options for these patients are endocrine therapies such as aromatase inhibitors, selective modulators of estrogen receptor activity or selective estrogen receptor down-regulators. Although endocrine therapies have high efficacy in early-stage breast cancers, the failure of the therapeutic response to these hormonal treatments remains the major clinical challenge. Recently, extracellular vesicles (EVs) have emerged as a novel mechanism of drug resistance. Indeed, EVs isolated from tumor and stromal cells act as key messengers in intercellular communications able to propagate traits of resistance and/or educate the microenvironment to sustain a breast cancer resistant phenotype. Understanding the EV-mediated molecular mechanisms involved in hormonal resistance can provide the rationale for novel and effective treatment modalities and allow for the identification of potential biomarkers to monitor therapy response in ER-positive breast cancer patients.

Abstract

Breast cancer is the most common solid malignancy diagnosed in females worldwide, and approximately 70% of these tumors express estrogen receptor α (ERα), the main biomarker of endocrine therapy. Unfortunately, despite the use of long-term anti-hormone adjuvant treatment, which has significantly reduced patient mortality, resistance to the endocrine treatments often develops, leading to disease recurrence and limiting clinical benefits. Emerging evidence indicates that extracellular vesicles (EVs), nanosized particles that are released by all cell types and responsible for local and systemic intercellular communications, might represent a newly identified mechanism underlying endocrine resistance. Unraveling the role of EVs, released by transformed cells during the tumor evolution under endocrine therapy, is still an open question in the cancer research area and the molecular mechanisms involved should be better defined to discover alternative therapeutic approaches to overcome resistance. In this review, we will provide an overview of recent findings on the involvement of EVs in sustaining hormonal resistance in breast cancer and discuss opportunities for their potential use as biomarkers to monitor the therapeutic response and disease progression.

ScanEV - A neural network-based tool for the automated detection of extracellular vesicles in TEM images

Transmission electron microscopy (TEM) is the most widely accepted method for visualization of extracellular vesicles (EVs), and particularly, exosomes. TEM images provide us with information about the size and morphology of the EVs. We have developed an online tool ScanEV (Scanner for the Extracellular Vesicles, available at https://bioeng.ru/scanev), for the rapid and automated processing of such images. ScanEV is based on a convolutional neural network; it detects the «cup-shaped» particles in the images and calculates their morphometric parameters. This tool will be useful for researchers who study EVs and use TEM for their characterization.

Landscape of extracellular vesicles in the tumour microenvironment: Interactions with stromal cells and with non-cell components, and impacts on metabolic reprogramming, horizontal transfer of neoplastic traits, and the emergence of therapeutic resistance

Extracellular vesicles (EVs) are increasingly recognised as a pivotal player in cell-cell communication, an attribute of EVs that derives from their ability to transport bioactive cargoes between cells, resulting in complex intercellular signalling mediated by EVs, which occurs under both physiological and pathological conditions. In the context of cancer, recent studies have demonstrated the versatile and crucial roles of EVs in the tumour microenvironment (TME). Here, we revisit EV biology, and focus on EV-mediated interactions between cancer cells and stromal cells, including fibroblasts, immune cells, endothelial cells and neurons. In addition, we focus on recent reports indicating interactions between EVs and non-cell constituents within the TME, including the extracellular matrix. We also review and summarise the intricate cancer-associated network modulated by EVs, which promotes metabolic reprogramming, horizontal transfer of neoplastic traits, and therapeutic resistance in the TME. We aim to provide a comprehensive and updated landscape of EVs in the TME, focusing on oncogenesis, cancer progression and therapeutic resistance, together with our future perspectives on the field.

The emerging roles of exosomes in anti-cancer drug resistance and tumor progression: An insight towards tumor-microenvironment interaction

The tumor microenvironment (TME) is a complex network of cellular organization consisting of fibroblasts, adipocytes, pericytes, immune cells endothelial cells, and extracellular matrix proteins. Besides communicating with each other, tumor cells are also involved in the tumor stroma interaction. Presently, most of the studies have focused on the contribution of TME in supporting tumor growth through intercellular communication by physical contact between the cells or through paracrine signaling cascades of growth factors and cytokines. The crosstalk between the tumor and TME has a pivotal role in the development of anti-cancer drug resistance. Drug resistance, be it against targeted or non-targeted drugs, has emerged as a major hurdle in the successful therapeutic intervention of cancer. Among the several mechanisms involved in the development of the resistance to anti-cancer therapies, exosomes have recently come into the limelight. Exosomes are the nano-sized vesicles, originated from the endolysosomal compartments and have the inherent potential to shuttle diverse biomolecules like proteins, lipids, and nucleic acids to the recipient cells. There are also instances where the pharmacological compounds are transferred between the cells via exosomes. For instance, the transfer of the cargoes from the drug-resistant tumor cells immensely affects the recipient drug-sensitive cells in terms of their proliferation, survival, migration, and drug resistance. In this review, we have discussed multiple aspects of the exosome-mediated bidirectional interplay between tumor and TME. Furthermore, we have also emphasized the contribution of exosomes promoting drug resistance and therapeutic strategies to mitigate the exosome induced drug resistance as well.

Exosomes and breast cancer drug resistance

Drug resistance is a daunting challenge in the treatment of breast cancer (BC). Exosomes, as intercellular communicative vectors in the tumor microenvironment, play an important role in BC progression. With the in-depth understanding of tumor heterogeneity, an emerging role of exosomes in drug resistance has attracted extensive attention. The functional proteins or non-coding RNAs contained in exosomes secreted from tumor and stromal cells mediate drug resistance by regulating drug efflux and metabolism, pro-survival signaling, epithelial–mesenchymal transition, stem-like property, and tumor microenvironmental remodeling. In this review, we summarize the underlying associations between exosomes and drug resistance of BC and discuss the unique biogenesis of exosomes, the change of exosome cargo, and the pattern of release by BC cells in response to drug treatment. Moreover, we propose exosome as a candidate biomarker in predicting and monitoring the therapeutic drug response of BC and as a potential target or carrier to reverse the drug resistance of BC.

Metformin Increases Exosome Biogenesis and Secretion in U87 MG Human Glioblastoma Cells: A Possible Mechanism of Therapeutic Resistance

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor. Metformin, an anti-diabetic drug, can suppress tumor cells. Exosomes from GBM cells contribute to intercellular communication, tumor aggressiveness, and therapeutic resistance. We studied the effect of metformin on the exosomal secretory pathway in U87 MG cells.

METHODS

Cell survival against metformin was investigated using MTT assay. Expression of miRNA-21, miRNA-155, and miRNA-182, as well as the genes involved in exosome biogenesis and secretion such as Rab27a, Rab27b, Rab11, CD63, and Alix were calculated by real time-PCR. The expression of CD63 protein was analyzed by western blotting, while the subcellular distribution of CD63 protein was monitored by flow cytometry. Exosomes were characterized by transmission and scanning electron microscopes, and flow cytometry. Amount of exosomes was assayed using acetylcholinesterase activity assay and ELISA. The expression of autophagic markers LC3 and P62 were assessed using ELISA.

RESULTS

Data showed that metformin decreased cell survival and expression of miRNA-21, miRNA-155, and miRNA-182 (p <0.05). Expression of Rab27a, Rab27b, Rab11, CD63, and Alix as well as protein level of CD63 up-regulated in treated cells (p <0.05). Concurrently, flow cytometry analysis showed that surface CD63/total CD63 ratio was increased in treated cells (p <0.05). We found that acetylcholinesterase activity and CD63 protein of exosomes from treated cells increased (p <0.05). The expression of LC3 and P62 was not affected by metformin (p >0.05).

CONCLUSION

Data indicates metformin could promote exosome biogenesis and secretion in U87 MG cells, proposing the therapeutic response against metformin.

Stomatin is highly expressed in exosomes of different origin and is a promising candidate as an exosomal marker

Proteins involved in the organizing of lipid rafts can be found in exosomes, as shown for caveolin-1, and they could contribute to exosomal cargo sorting, as shown for flotillins. Stomatin belongs to the same stomatin/prohibitin/flotillin/HflK/C family of lipid rafts proteins, but it has never been studied in exosomes except for extracellular vesicles (EVs) originating from blood cells. Here we first show the presence of stomatin in exosomes produced by epithelial cancer cells (non-small cell lung cancer, breast, and ovarian cancer cells) as well as in EVs from biological fluids, including blood plasma, ascitic fluids, and uterine flushings. A high abundance of stomatin in EVs of various origins and its enrichment in exosomes make stomatin a promising exosomal marker. Comparison with other lipid raft proteins and exosomal markers showed that the level of stomatin protein in exosomes from different sources corresponds well to that of CD9, while it differs essentially from flotillin-1 and flotillin-2 homologs, which in turn are present in exosomes in nearly equal proportions. In contrast, the level of vesicular caveolin-1 as well as its EV-to-cellular ratio vary drastically depending on cell type.

Upregulation of Akt/Raptor signaling is associated with rapamycin resistance of breast cancer cells

mTOR inhibitors are considered today to be one of the most promising anticancer drugs. Here to study the mechanism of the acquired resistance of MCF-7 breast cancer cells to mTOR inhibitors two different models of the cell resistance were used: rapamycin-resistant MCF-7/Rap subline developed under long-term rapamycin treatment, and metformin-resistant MCF-7/M subline obtained by long-term metformin treatment. We have found that both resistant sublines were characterized by common features: increased expression of mTOR-interacting Raptor protein, increased phosphorylation of Akt, and activation of growth-related transcriptional factor AP-1. Cell response to mTOR inhibitors was partially restored under treatment with PI3K inhibitor wortmannin supporting the direct connection between Akt activation and poor cell response to therapeutic drugs. Transfection of mir-181c, one of the positive regulators of Akt and mTOR, led to an increase in the cell resistance to both mTOR inhibitors, rapamycin and metformin, which correlated with Raptor overexpression and activation of Akt/AP-1 signaling. In general, the effect of Raptor overexpression in the resistant cells, as well as the ability of mir-181c to modulate the Raptor expression, can open novel perspectives in the treatment of rapalogues-resistant cancers, based on the drugs design targeting mir-181c/Raptor axis.

Evidence for Enhanced Exosome Production in Aromatase Inhibitor-Resistant Breast Cancer Cells

Aromatase inhibitors (AIs) represent the standard anti-hormonal therapy for post-menopausal estrogen receptor-positive breast cancer, but their efficacy is limited by the emergence of AI resistance (AI^R). Exosomes act as vehicles to engender cancer progression and drug resistance. The goal of this work was to study exosome contribution in AI^R mechanisms, using estrogen-dependent MCF-7 breast cancer cells as models and MCF-7 LTED (Long-Term Estrogen Deprived) subline, modeling AI^R. We found that exosome secretion was significantly increased in MCF-7 LTED cells compared to MCF-7 cells. MCF-7 LTED cells also exhibited a higher amount of exosomal RNA and proteins than MCF-7 cells. Proteomic analysis revealed significant alterations in the cellular proteome. Indeed, we showed an enrichment of proteins frequently identified in exosomes in MCF-7 LTED cells. The most up-regulated proteins in MCF-7 LTED cells were represented by Rab GTPases, important vesicle transport-regulators in cancer, that are significantly mapped in “small GTPase-mediated signal transduction”, “protein transport” and “vesicle-mediated transport” Gene Ontology categories. Expression of selected Rab GTPases was validated by immunoblotting. Collectively, we evidence, for the first time, that AI^R breast cancer cells display an increased capability to release exosomes, which may be associated with an enhanced Rab GTPase expression. These data provide the rationale for further studies directed at clarifying exosome’s role on endocrine therapy, with the aim to offer relevant markers and druggable therapeutic targets for the management of hormone-resistant breast cancers.

Exosomes Mediated Transfer of Circ_UBE2D2 Enhances the Resistance of Breast Cancer to Tamoxifen by Binding to MiR-200a-3p

Background

Circular RNA UBE2D2 (circ_UBE2D2) has been found to be involved in the progression of breast cancer. Exosomes are critical mediators of intercellular communication, however, the function of exosomal circ_UBE2D2 in breast cancer remains vague.

Material/Methods

Cell viability was measured by Cell Counting Kit-8 assay. Western blot was used to detect the levels of estrogen receptor alpha (ERα), E-cadherin, vimentin, CD9, and CD63. Migrated and invaded cells were examined using Transwell assay. Circ_UBE2D2 and microRNA (miR)-200a-3p levels were detected using quantitative real-time polymerase chain reaction. Exosomes were isolated by ultracentrifugation method. The interaction between circ_UBE2D2 and miR-200a-3p was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay. Murine xenograft model was established to conduct in vivo experiments.

Results

We found that circ_UBE2D2 was upregulated in breast cancer tamoxifen-resistant tissues and cell lines, and circ_UBE2D2 deletion mitigated tamoxifen resistance in breast cancer cells. Circ_UBE2D2 was also significantly loaded in exosomes isolated from resistant cells and could be transferred to parental cells. MiR-200a-3p was a target of circ_UBE2D2, and we demonstrated that exosomes mediated transfer of circ_UBE2D2 interacted with miR-200a-3p to enhance tamoxifen resistance of breast cancer cells by regulating cell viability, metastasis, and the level of ERα in vivo and in vitro.

Conclusions

Exosomes mediated transfer of circ_UBE2D2 reinforced tamoxifen resistance in breast cancer by binding to miR-200a-3p, providing new insights into the boost of the effectiveness of tamoxifen on breast cancer patients.

Exosomes as drug delivery vehicle and contributor of resistance to anticancer drugs

Exosomes are small membranous vesicles implicated in intercellular signalling. Through their uncanny ability to carry and deliver donor cellular cargo (biomolecules) to target cells, they exert a profound effect on the regular functioning of healthy cells and play a significant role in pathogenesis and progression of several diseases, including cancer. The composition and number of endogenously circulating exosomes frequently vary, which is often reflective of the pathophysiological status of the cell. Applicability of exosomes derived from normal cells as a drug carrier with or without modifying their intraluminal and surface components are generally tested. Conversely, exosomes also are reported to contribute to resistance towards several anti-cancer therapies. Therefore, it is necessary to carefully evaluate the role of exosomes in cancer progression, resistance and the potential use of exosomes as a delivery vehicle of cancer therapeutics. In this review, we summarize the recent advancements in the exploitation of exosomes as a drug delivery vehicle. We also discuss the role of exosomes in conferring resistance to anti-cancer therapeutics. While this review is focused on cancer, the exosome-based drug delivery and resistance is also applicable to other human diseases.

Phenotypic Switching of Naïve T Cells to Immune-Suppressive Treg-Like Cells by Mutant KRAS

Oncogenic (mutant) Ras protein Kirsten rat sarcoma viral oncogene homolog (KRAS) promotes uncontrolled proliferation, altered metabolism, and loss of genome integrity in a cell-intrinsic manner. Here, we demonstrate that CD4⁺ T cells when incubated with tumor-derived exosomes from mutant (MT) KRAS non-small-cell lung cancer (NSCLC) cells, patient sera, or a mouse xenograft model, induce phenotypic conversion to FOXP3⁺ Treg-like cells that are immune-suppressive. Furthermore, transfecting T cells with MT KRAS cDNA alone induced phenotypic switching and mathematical modeling supported this conclusion. Single-cell sequencing identified the interferon pathway as the mechanism underlying the phenotypic switch. These observations highlight a novel cytokine-independent, cell-extrinsic role for KRAS in T cell phenotypic switching. Thus, targeting this new class of Tregs represents a unique therapeutic approach for NSCLC. Since KRAS is the most frequently mutated oncogene in a wide variety of cancers, the findings of this investigation are likely to be of broad interest and have a large scientific impact.

Recent advancements in the study of breast cancer exosomes as mediators of intratumoral communication

Breast cancer is a heterogeneous disease, with a morbidity rate of 27.8% and a mortality rate of 15% among women population worldwide. Understanding how this cancer develops and the mechanisms behind tumor progression and chemoresistance is of utmost importance. Exosomes mediate communication in a population of heterogeneous tumoral cells. They have a cargo composed of oncogenes and oncomiRs which change the transcriptomic scenario of their targeted cells and activate numerous tumor-promoting signaling pathways. Exosomes secreted by breast cancer cells lead to enhanced cell proliferation, replicative immortality, angiogenesis, invasion, migration, and chemoresistance. Studying exosomes from this perspective offers more in depth understanding of breast malignancy and may aid in the future development of early diagnostic, prognostic and therapeutic options. We present the latest findings in this area and offer practical solutions which may further stimulate the much-needed research of exosome in breast cancer.

Molecular insights into cancer drug resistance from a proteomics perspective

INTRODUCTION

Resistance to chemotherapy and development of specific and effective molecular targeted therapies are major obstacles facing current cancer treatment. Comparative proteomic approaches have been employed for the discovery of putative biomarkers associated with cancer drug resistance and have yielded a number of candidate proteins, showing great promise for both novel drug target identification and personalized medicine for the treatment of drug-resistant cancer. Areas covered: Herein, we review the recent advances and challenges in proteomics studies on cancer drug resistance with an emphasis on biomarker discovery, as well as understanding the interconnectivity of proteins in disease-related signaling pathways. In addition, we highlight the critical role that post-translational modifications (PTMs) play in the mechanisms of cancer drug resistance. Expert opinion: Revealing changes in proteome profiles and the role of PTMs in drug-resistant cancer is key to deciphering the mechanisms of treatment resistance. With the development of sensitive and specific mass spectrometry (MS)-based proteomics and related technologies, it is now possible to investigate in depth potential biomarkers and the molecular mechanisms of cancer drug resistance, assisting the development of individualized therapeutic strategies for cancer patients.

Metalloproteinases at the surface of small extrcellular vesicles in advanced ovarian cancer: Relationships with ascites volume and peritoneal canceromatosis index

Metalloproteinases and their extracellular matrix metalloproteinase inducer (EMMPRIN) play an essential role in the regulation of signaling from growth factors receptors and adhesion molecules, cell motility and extracellular matrix degradation. The aim of the study was to evaluate the relationship between the levels of small extracellular vesicles (sEVs) metalloproteinases, such as ADAM10, ADAM17, MMP2, MMP9 and EMMPRIN and ascites volume and peritoneal canceromatosis index in advanced ovarian cancer patients (OCPs). The subpopulations of metalloproteinases at the surface of sEVs of borderline ovarian tumor patients (BOTPs) (n = 20, 36.5 ± 2.5 years) and previously untreated advanced OCPs (n = 35, 56.5 ± 2.5 years) were evaluated using flow cytometry. The metalloproteinase subpopulations of CD9-positive sEVs isolated from plasma of BOTPs and OCPs appeared to be quite similar. However, a significant difference in the expression of ADAM-metalloproteinases in ascites sEVs was found between BOTPs and OCPs. The level of sEVs metalloproteinases in OCPs significantly depended on the ascites volume. A statistically significant relationship between the level of ADAM10+/ADAM17- subpopulation in plasma sEVs and the peritoneal canceromatosis index was found (R = 0.66, p < .05). The levels of metalloproteinases and EMMPRIN in circulating sEVs, as well as the assessment of individual subpopulations may be promising approaches to OCPs managing.

Pathways to Endocrine Therapy Resistance in Breast Cancer

Breast cancers with positive expression of Estrogen Receptor (ER+) are treated with anti-hormone/endocrine therapy which targets the activity of the receptor, the half-life of the receptor or the availability of estrogen. This has significantly decreased mortality in women with ER+ breast cancer, however, about 25-30% of treated women run the risk or recurrence due to either intrinsic or acquired resistance to endocrine therapies. While ER itself is a predictor of response to such therapies, there exists a need to find more biomarkers and novel targets to treat resistant tumors. In this review, we summarize the known mechanisms and describe the ability of genomics in unraveling rare mutations and gene rearrangements that may impact the development of resistance and therefore treatment of ER+ breast cancer in the near future.

A Litopenaeus vannamei Hemocyanin-Derived Antimicrobial Peptide (Peptide B11) Attenuates Cancer Cells' Proliferation

Antimicrobial peptides play important roles in the immune response to pathogens and tumor cells; for this reason, they are being exploited for therapeutic use. In this study, we describe a Litopenaeus vannamei hemocyanin-derived peptide, denoted B11, which shares similar features with other anticancer peptides and attenuates the proliferation of cancer cells. Cell viability assay revealed that B11 significantly inhibited the proliferation of human cervical (HeLa), human hepatocellular carcinoma (HepG2), and human esophageal cancer (EC109) cancer cell lines, but not normal liver cell lines (T-antigen-immortalized human liver epithelial (THLE) cells or THLE-3), by inducing morphological changes, nuclear condensation, and margination, features which are indicative of apoptosis. Besides, peptide B11-induced apoptosis was confirmed by isothiocyanate-labeled Annexin V/propidium iodide (Annexin V-FITC/PI) double staining of HeLa cells. Moreover, cell uptake studies, confocal microscopy, and Western blot analysis revealed that rhodamine-labeled B11 permeated HeLa cells and localized to the mitochondria, causing mitochondria dysfunction through lost mitochondrial membrane potential, which consequently triggered the induction of apoptosis. Increased expression levels of caspase-9, caspase-3, and Bax (Bcl-2-associated X) proteins, coupled with a decrease in Bcl-2 (B-cell lymphoma 2) protein, confirmed that peptide B11 induced apoptosis via the mitochondrial pathway. Thus, the hemocyanin-derived peptide, B11, inhibits the proliferation of cancer cells by causing mitochondrial dysfunction and inducing apoptotic cell death, for which reason it could be explored as an anticancer peptide.

Extracellular vesicles: translational challenges and opportunities

Extracellular vesicles (EVs) are a heterogeneous group of small lipid-enclosed structures with myriad roles in physiology and disease. The recent surge of interest in EVs has led to greater understanding of their biology and appreciation of how they might be utilised as diagnostic and therapeutic tools. There remain, however, a number of challenges that must be overcome before EVs may be used routinely in the clinic. In this review we will discuss the translational potential of EVs and the current technologies available to isolate, purify and analyse EVs and their contents.