Breast Cancer-derived Extracellular Vesicles Research Articles

Abstract 2436: In-depth analysis of microRNA signature in breast cancer derived extracellular vesicles: A potential biomarker repository for breast cancer diagnosis

Abstract Breast cancer remains one of the leading causes of cancer-related mortality among women worldwide. With the rising incidence of breast cancer, early and accurate diagnosis is pivotal in improving survival rates and patient outcomes. Our study addresses to identify vesicles associated with breast cancer in scope of miRNA signature. We focused on isolating breast cancer-derived extracellular vesicles (BEVs) from the bloodstream with immune affinity capture techniques. Then, we analyzed the miRNA profiles of BEVs in plasma samples from 120 breast cancer patients, 46 individuals with benign tumors, and 45 healthy controls. In this study, we analyzed to discover miRNA candidates for diagnosis of breast cancer with The Gene Expression Omnibus (GEO) database and found 379 down-regulated and 584 up-regulated differentially expressed miRNAs (DEMs) in tissue samples across 5 GEO datasets, and 28 down-regulated and 80 up-regulated DEMS in blood samples. Subsequently, we measured the expression levels of these 10 candidate miRNAs in BEVs from breast cancer cells and compared them with EVs from human mammary cells (MCF10a), using our BEV isolation method. The expression profiles of these miRNAs in BEVs were significantly elevated, supporting their potential as surrogate markers for breast cancer diagnosis. When comparing the AUC values of 10 candidate miRNAs through ROC analysis, 5 EV miRNAs (miR-21, miR-106b, miR-181a, miR-484, and miR-1260b) showed a high AUC values above 0.8. Subsequently, we verified a distinct signature of 5 EV miRNAs that effectively differentiate breast cancer patients from normal controls with 57.14% of sensitivity and 95% of specificity. Overall, our study not only complements existing diagnostic methods with high accuracy but also provides a deeper understanding of the molecular aspects of breast cancer, heralding a significant advancement in precision medicine and personalized cancer care. Citation Format: Jee Ye Kim, Min Woo Kim, Young Kim, Sol Moon, Suji Lee, Hyojung Lee, Joon Ye Kim, Seung Il Kim. In-depth analysis of microRNA signature in breast cancer derived extracellular vesicles: A potential biomarker repository for breast cancer diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2436.

Abstract 1500: Breast cancer-derived extracellular vesicles modulate the endocytic metabolism and morphodynamics of the endothelial cells of the blood-brain barrier

Abstract Breast cancer, particularly the triple-negative subtype, is the primary cause of brain metastasis in women, affecting 10-20% of breast cancer patients. Breast cancer patients who develop brain metastasis have few treatment options and a dismal prognosis with a median survival time of 6-16 months. We demonstrated, for the first time, that EVs derived from brain-seeking breast cancer cells (BrEVs) breach the intact blood-brain barrier (BBB) via transcytosis and cause a significantly increased incidence of breast-to-brain metastasis. Within this context, we are now studying the interactions between BrEVs and the endothelial cells (ECs) of the BBB. BrEVs were isolated by ultracentrifugation, characterized following the latest guidelines published by the International Society of Extracellular Vesicles (MISEV 2018) and tested in vitro using primary human brain ECs and in vivo using our mouse model of breast-to-brain metastasis. ECs were treated with BrEVs and analyzed using antibody-based assays, impedance measurements, genetic engineering and fixed and live cell imaging. The imaging results were analyzed using novel machine learning approaches to detect and describe, for the first time, EV-mediated morphodynamic changes at the brain EC barrier level. In vivo, we administered BrEVs intravenously to our models of breast-to-brain metastasis, followed by the analysis of mouse brains and their cerebral microvessels to examine microscopic structure and protein expression. Our studies show that (1) BrEVs target BBB ECs both in vitro and in vivo, causing significant variations of multiple proteins involved in the intracytoplasmic vesicles' long-recycling loop, (2) BrEVs are responsible for specific EC barrier function and morphodynamic changes and (3) BrEVs mediate, at least in part, their effect(s) through the delivery of specific micro RNAs. Taken together, our studies demonstrate that BrEVs have a significant impact on brain EC endocytic metabolism and morphodynamics, promoting transcytosis and sustaining breast-to-brain metastasis. Our findings increase our understanding of the early events that facilitate brain metastasis and have the potential to identify key regulators of brain metastasis formation. These results also inform and contribute to the development of EV-based therapeutic and diagnostic strategies for brain metastasis. (This work was supported by NIH R21 CA253051-01, the Breast Cancer Research Foundation, NIH T32 5T32HL007917-22 and the Nile Albright Research Foundation.) Citation Format: Sara Busatto, Golnaz Morad, Marsha A Moses. Breast cancer-derived extracellular vesicles modulate the endocytic metabolism and morphodynamics of the endothelial cells of the blood-brain barrier [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1500.

Abstract 3758: Evaluation of breast cancer-derived extracellular vesicles as diagnostic indicator for HER2 status

Abstract HER2-low is a new distinct type of breast cancer that is characterized by low levels of the HER2 protein. As treatment paradigms for HER2-low breast cancer are rapidly evolving with the approval of antibody-drug conjugates, identification of HER2-low breast cancer with more sensitive and reproducible HER2 assays is needed. We aimed to investigate the utility of liquid biopsy in isolating tumor-derived extracellular vesicles (TDEs) for diagnosis of HER2 status. We adopted an affinity-based approach to isolate TDEs and performed CNV analysis of the ERBB2/neu genes using the tumor DNA present in TDEs (etDNA). HER2 status of etDNA had been determined by droplet digital PCR using HER2/EIF2C ratio, a highly accurate method to quantify DNA copy number. In our study, we utilized a variety of breast cancer cell lines categorized as HER2-low (MDA-MB-231, MCF7, ZR-75-1) and HER2-high (MDA-MB-453, BT-474, SK-BR-3) to confirm HER2 expression in extracellular vesicles (EVs) by flow cytometry. This analysis successfully demonstrated that EVs effectively reflect the HER2 status of the tumor cells, evidenced by a strong Pearson correlation coefficient (r=0.987, p<0.001). Further clinical validation was conducted with plasma samples from 22 breast cancer patients. In the clinical study, we observed a significant correlation between the CNV of tumor DNA present in TDEs and the HER2 status of primary tumors (p<0.01). Additionally, the Receiver Operating Characteristic (ROC) analysis yielded an impressive area under the curve (AUC) value of 0.838 (p<0.01), demonstrating a high level of accuracy in differentiating between high and low HER2 groups, with a sensitivity of 55.6% and a specificity of 100%. In summary, we show potential diagnostic tools for real-time, less invasive determination of HER2 status in primary tumors, providing continuous monitoring methods for HER2 status. Although further validation in larger cohorts and prospective studies is needed, our study indicates that TDE analysis could contribute to the assays for identification of the HER2 status in breast cancer patients. Citation Format: Sol Moon, Min Woo Kim, Young Kim, Suji Lee, Hyojung Lee, Joon Ye Kim, Seung Il Kim, Jee Ye Kim. Evaluation of breast cancer-derived extracellular vesicles as diagnostic indicator for HER2 status [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3758.

Influence of Extracellular Vesicles on Lung Stromal Cells during Breast Cancer Metastasis.

Breast cancer is a prominent cause of cancer diagnosis and death in women globally, with over 90% of deaths being attributed to complications that arise from metastasis. One of the common locations for breast cancer metastasis is the lung, which is associated with significant morbidity and mortality. Curative treatments for metastatic breast cancer patients are not available and the molecular mechanisms that underlie lung metastasis are not fully understood. In order to better treat these patients, identifying events that occur both prior to and during metastatic spread to the lung is essential. Several studies have demonstrated that breast cancer-derived extracellular vesicles secreted from the primary breast tumor play a key role in establishing the lung pre-metastatic niche to support colonization of metastatic tumor cells. In this review, we summarize recent work supporting the influence of extracellular vesicles on stromal components of the lung to construct the pre-metastatic niche and support metastasis. Furthermore, we discuss the potential clinical applications of utilizing extracellular vesicles for diagnosis and treatment. Together, this review highlights the dynamic nature of extracellular vesicles, their roles in breast cancer metastasis to the lung, and their value as potential biomarkers and therapeutics for cancer prevention.

Triple-Negative Breast Cancer-Derived Extracellular Vesicles Promote a Hepatic Premetastatic Niche via a Cascade of Microenvironment Remodeling.

Our data provides previously unknown cascades regarding the molecular education of premetastatic niche in liver for TNBC.

Monitoring Of Breast Cancer Treatment Response By Analysis Of Breast Cancer-Derived Extracellular Vesicles

Monitoring Of Breast Cancer Treatment Response By Analysis Of Breast Cancer-Derived Extracellular Vesicles

Breast cancer-derived extracellular vesicles are the source of functional metabolic enzymes as potential targets for cancer therapy

In this work, intracellular vesicles (MVs) of breast cancer were studied. These vesicles are a source of potential targets for breast cancer therapy. This study shows that MVs carry functional metabolic enzymes and provides a framework for future studies of their biological role in BC and potential in therapeutic applications

Protein biomarkers in breast cancer-derived extracellular vesicles for use in liquid biopsies.

Breast cancer is the most common malignant disease in women worldwide. Early diagnosis and treatment can greatly improve the management of breast cancer. Liquid biopsies are becoming convenient detection methods for diagnosing and monitoring breast cancer due to their noninvasiveness and ability to provide real-time feedback. A range of liquid biopsy markers, including circulating tumor proteins, circulating tumor cells, and circulating tumor nucleic acids, have been implemented for breast cancer diagnosis and prognosis, with each having its own advantages and limitations. Circulating extracellular vesicles are messengers of intercellular communication that are packed with information from mother cells and are found in a wide variety of bodily fluids; thus, they are emerging as ideal candidates for liquid biopsy biomarkers. In this review, we summarize extracellular vesicle protein markers that can be potentially used for the early diagnosis and prognosis of breast cancer or determining its specific subtypes.

Abstract 459: Lipidomic analysis of extracellular vesicles and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis

Abstract Background: Tumor-derived Extracellular Vesicles (EVs) are found in body fluids of cancer patients. These EVs include exosomes and microvesicles, which play an important role in tumor development and metastasis. Although EVs have great potential as liquid biopsies for early detection of breast cancer, the lipid composition of breast cancer-derived EVs is unknown. Here, we studied the lipid composition of EVs and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis. Methods: The lipid composition of EVs and their parental cells were evaluated for nine breast cancer and two non-cancerous mammary cell lines. EVs were isolated by size-exclusion chromatography (SEC). Furthermore, ten blood plasma samples were studied from women diagnosed with primary breast cancer before surgery, nine samples from patients with progressive metastatic breast cancer and ten samples from healthy women who neither had pre-existing medical conditions nor infections at the time the samples were collected or in the previous weeks. EVs were obtained from blood plasma samples by a combination of density gradient ultracentrifugation and SEC. Lipids were extracted from EVs and analyzed by reverse-phase liquid chromatography mass-spectrometry (LC-MS). Results: We found that EVs produced by breast cancer cell lines were enriched in sphingomyelins and ceramides when compared to their parental cells. Furthermore, phospholipids such as phosphatidylcholine and phosphatidylethanolamine were found to be abundant in these EVs. Multivariate analyses showed that EVs released by breast cancer cells can be distinguished from those released by non-cancerous cells based on their phospholipid and sphingolipid composition (AUCROC=0.99, p<0.001). A key finding of this study is that we also found significant differences in the phospholipid and sphingolipid composition between EVs found in blood plasma from breast cancer patients and healthy volunteers (AUCROC=0.99, p<0.001). Importantly with respect to the practical applications of this study for early diagnosis of breast cancer, these differences in EV's lipid content were also significant between EVs from primary breast cancer patients and healthy volunteers (AUCROC=0.99, p<0.001). Annotation of specific lipid species are currently being carried out by MS/MS analysis. Conclusion: Our findings demonstrate the potential of the lipid content of cancer-derived EVs for the identification of lipid biomarkers for breast cancer diagnosis and its use for the development of non-invasive (or minimally invasive) diagnostic methods based on blood plasma analysis. Citation Format: Erika Dorado, M Luisa Doria, Anika Nagelkerke, James S McKenzie, Stefania Maneta-Stavrakaki, Charlotte Ion, Thomas Whittaker, Jeremy Nicholson, Molly M Stevens, R Charles Coombes, Zoltan Takats. Lipidomic analysis of extracellular vesicles and its potential for the identification of body fluid-based biomarkers for breast cancer diagnosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 459.

Extracellular Vesicle-Mediated Purinergic Signaling Contributes to Host Microenvironment Plasticity and Metastasis in Triple Negative Breast Cancer.

Metastasis accounts for over 90% of cancer-related deaths, yet the mechanisms guiding this process remain unclear. Secreted nucleoside diphosphate kinase A and B (NDPK) support breast cancer metastasis. Proteomic evidence confirms their presence in breast cancer-derived extracellular vesicles (EVs). We investigated the role of EV-associated NDPK in modulating the host microenvironment in favor of pre-metastatic niche formation. We measured NDPK expression and activity in EVs isolated from triple-negative breast cancer (MDA-MB-231) and non-tumorigenic mammary epithelial (HME1) cells using flow cytometry, western blot, and ATP assay. We evaluated the effects of EV-associated NDPK on endothelial cell migration, vascular remodeling, and metastasis. We further assessed MDA-MB-231 EV-induced proteomic changes in support of pre-metastatic lung niche formation. NDPK-B expression and phosphotransferase activity were enriched in MDA-MB-231 EVs that promote vascular endothelial cell migration and disrupt monolayer integrity. MDA-MB-231 EV-treated mice demonstrate pulmonary vascular leakage and enhanced experimental lung metastasis, whereas treatment with an NDPK inhibitor or a P2Y1 purinoreceptor antagonist blunts these effects. We identified perturbations to the purinergic signaling pathway in experimental lungs, lending evidence to support a role for EV-associated NDPK-B in lung pre-metastatic niche formation and metastatic outgrowth. These studies prompt further evaluation of NDPK-mediated EV signaling using targeted genetic silencing approaches.

Three-Dimensional Human Liver-Chip Emulating Premetastatic Niche Formation by Breast Cancer-Derived Extracellular Vesicles.

The liver is one of the most common sites of breast cancer metastasis and is associated with high lethality. Although the interaction between tumor cells and their microenvironment at metastatic sites has been recognized as a key regulator of tumor progression, the underlying mechanism is not fully elucidated. Here, we describe a three-dimensional (3D) microfluidic human liver-on-a-chip (liver-chip) that emulates the formation of a premetastatic niche to investigate the roles of breast cancer-derived extracellular vesicles (EVs) in liver metastasis. We demonstrate that breast cancer-derived EVs activate liver sinusoidal endothelial cells (LSECs) in the liver-chip, inducing endothelial to mesenchymal transition and destruction of vessel barriers. In addition, we show that transforming growth factor β1 (TGFβ1) in breast cancer-derived EVs upregulates fibronectin, an adhesive extracellular matrix protein, on LSECs, which facilitates the adhesion of breast cancer cells to the liver microenvironment. Furthermore, we observed that EVs isolated from triple-negative breast cancer (TNBC) patients with liver metastasis contain higher TGFβ1 levels and induce adhesion of more breast cancer cells to the 3D human liver-chip than do EVs isolated from healthy donors or nonmetastatic TNBC patients. These findings provide a better understanding of the mechanisms through which breast cancer-derived EVs guide secondary metastasis to the liver. Furthermore, the 3D human liver-chip described in this study provides a platform to investigate the mechanisms underlying secondary metastasis to the liver and possible therapeutic strategies.

Cdc42-Dependent Transfer of mir301 from Breast Cancer-Derived Extracellular Vesicles Regulates the Matrix Modulating Ability of Astrocytes at the Blood–Brain Barrier

Breast cancer brain metastasis is a major clinical challenge and is associated with a dismal prognosis. Understanding the mechanisms underlying the early stages of brain metastasis can provide opportunities to develop efficient diagnostics and therapeutics for this significant clinical challenge. We have previously reported that breast cancer-derived extracellular vesicles (EVs) breach the blood–brain barrier (BBB) via transcytosis and can promote brain metastasis. Here, we elucidate the functional consequences of EV transport across the BBB. We demonstrate that brain metastasis-promoting EVs can be internalized by astrocytes and modulate the behavior of these cells to promote extracellular matrix remodeling in vivo. We have identified protein and miRNA signatures in these EVs that can lead to the interaction of EVs with astrocytes and, as such, have the potential to serve as targets for development of diagnostics and therapeutics for early detection and therapeutic intervention in breast cancer brain metastasis.

Triple-Negative Primary Breast Tumors Induce Supportive Premetastatic Changes in the Extracellular Matrix and Soluble Components of the Lung Microenvironment.

The lung is one of the deadliest sites of breast cancer metastasis, particularly in patients with triple-negative (TN) disease. We hypothesized that the presence of a TN primary breast tumor induces changes in the extracellular matrix (ECM) and soluble components of the lung microenvironment that support metastatic behavior. SUM159 (TN) and MCF7 (luminal A) breast cancer cells were injected into mice, and primary breast tumors were established prior to assessing metastatic niche changes. We observed increased CD117+ hematopoietic progenitor cells in the bone marrow of SUM159 mice versus MCF7 or control mice (p < 0.05). Relative to mice bearing MCF7 tumors and non-tumor controls, mice bearing SUM159 tumors demonstrated enhanced expression of ECM proteins in the lung (fibronectin, tenascin-c and periostin), with similar changes observed in lung fibroblasts treated with extracellular vesicles (EVs) from TN breast cancer cells (p < 0.05). Exposure to lung-conditioned media (LCM) from SUM159 tumor-bearing mice resulted in increased migration/proliferation of both SUM159 and MCF7 cells relative to the control (p < 0.05). In contrast, LCM from MCF-7 tumor-bearing mice had no such effect. LCM from SUM159 tumor-bearing mice contained 16 unique proteins relative to other LCM conditions, including the metastasis-associated proteins CCL7, FGFR4, GM-CSF, MMP3, thrombospondin-1 and VEGF. These findings suggest for the first time that the TN breast cancer molecular subtype may be an important determinant of premetastatic changes to both the ECM and soluble components of the lung, potentially mediated via breast cancer-derived EVs.

Breast cancer-derived extracellular vesicles stimulate myofibroblast differentiation and pro-angiogenic behavior of adipose stem cells

Adipose-derived stem cells (ASCs) are abundantly present in the mammary microenvironment and can promote breast cancer malignancy by differentiating into myofibroblasts. However, it remains largely unclear which role tumor-derived extracellular vesicles (TEVs) play in this process. Here, we used microfabricated, type I collagen-based 3-D tissue culture platforms to investigate the effect of breast cancer cell-derived TEVs on ASCs myofibroblast differentiation and consequential changes in extracellular matrix remodeling and vascular sprouting. TEVs collected from MDA MB-231 human metastatic breast cancer cells (MDAs) promoted ASC myofibroblast differentiation in both 2-D and 3-D cultures as indicated by increased alpha smooth muscle actin (α-SMA) and fibronectin (Fn) levels. Correspondingly, TEV-treated ASCs were more contractile, secreted more vascular endothelial growth factor (VEGF), and promoted angiogenic sprouting of human umbilical vein endothelial cells (HUVECs). These changes were dependent on transforming growth factor beta (TGF-β)-related signaling and tumor cell glutaminase activity as their inhibition decreased TEV-related myofibroblastic differentiation of ASCs and related functional consequences. In summary, our data suggest that TEVs are important signaling factors that contribute to ASC desmoplastic reprogramming in the tumor microenvironment, and suggest that tumor cell glutamine metabolism may be used as a therapeutic target to interfere with this process.

Abstract 3152: Breast cancer-derived extracellular vesicles: clinical and prognostic impact

Abstract Background: Extracellular vesicles (EVs) are released from cancer cells into the tumor microenvironment, there participating in intercellular communication by altering recipient cell function. Breast cancer (BC) derived EVs are hypothesized to have an impact on tumor growth, immunosuppression or metastatic development, indicating analytical significance of EV concentrations in BC patients. For this reason, we investigated plasmatic EV numbers from locally advanced, neoadjuvant treated (NACT) BC patients in association with clinical parameters and prognostic impact. Material and methods: Plasmatic extracellular vesicles were isolated using ExoQuick™ precipitation reagent (SBI Inc., Mountain View, CA, USA), according to manufacturer's instructions, from locally advanced BC patients before (n = 142) and after (n = 156) NACT as well as from healthy female controls (n = 16). Subsequently, number and EV particle size were analyzed using ZetaView Laser Scattering Video Microscope (Particle Metrix GmbH, Microtrac, Meerbusch, Germany). Samples were 1:50.000 in PBS pre-diluted to obtain particle concentrations of approx. 1 × 10⁁6 particles per ml. Circulating tumor cells (CTCs) and stem cell-like circulating tumor cells (slCTCs) were evaluated using the AdnaTests BreastCancer, StemCell and EMT, respectively (QIAGEN Hannover GmbH, Germany). Results: EV particle concentrations (mean ± SEM in 10⁁9/ml) were significantly (p &amp;lt; 0.0001) elevated in BC patients (n = 104, respectively) before (2370 ± 170) and after (3524 ± 523) NACT compared to healthy females (90 ± 19). Paired analysis before and after NACT revealed higher EV levels after NACT (p = 0.008). In association studies, high EV numbers before NACT were related to less differentiated carcinomas and to lymph node spread. ROC analysis showed optimal cut-off values of EV levels (i) before NACT: 3540 × 10⁁9/ml (sensitivity: 66.7%; specificity: 78.1%; AUC = 0.706) and (ii) after NACT: 2480 × 10⁁9/ml (sensitivity: 100%; specificity: 44,3%; AUC = 0.654). In Kaplan-Meier analysis, a decreased 3-year PFS was significantly associated with EV particle concentrations after NACT &amp;gt; 2480 × 10⁁9/ml (p = 0.005). A reduced OS of BC patients was significantly associated with (i) EV levels before NACT &amp;gt; 3540 × 10⁁9/ml) (p = 0.001) and (ii) EV levels after NACT &amp;gt; 2480 × 109/ml) (p = 0.003). Decreased EV levels were found in BC patients after NACT with CTCs expressing ERCC1 (p = 0.025) or the stem cell marker ALDH1 (p = 0.004). Conclusion: In conclusion, BC patients showed elevated plasmatic EV levels compared to healthy females, while increased EV levels after NACT might be due to therapeutic effects. The association between EV particle concentrations and clinical parameters as well as their prognostic impact on clinical outcome in BC indicate the importance of EVs as a mediator in the BC tumor microenvironment. Therefore, determination of plasmatic EV particle amount might serve as a biomarker for BC monitoring. Citation Format: Lisa König, Vera Rebmann, Oliver Hoffmann, Ann-Kathrin Bittner, Bettina Wagner, Luis Felipe Santos Manvailer, Sabine Schramm, Agnes Bankfalvi, Bernd Giebel, Rainer Kimmig, Peter A. Horn, Sabine Kasimir-Bauer. Breast cancer-derived extracellular vesicles: clinical and prognostic impact. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3152.

Breast Cancer-Derived Extracellular Vesicles: Characterization and Contribution to the Metastatic Phenotype.

The study of extracellular vesicles (EVs) in cancer progression is a complex and rapidly evolving field. Whole categories of cellular interactions in cancer which were originally presumed to be due solely to soluble secreted molecules have now evolved to include membrane-enclosed extracellular vesicles (EVs), which include both exosomes and shed microvesicles (MVs), and can contain many of the same molecules as those secreted in soluble form but many different molecules as well. EVs released by cancer cells can transfer mRNA, miRNA, and proteins to different recipient cells within the tumor microenvironment, in both an autocrine and paracrine manner, causing a significant impact on signaling pathways, mRNA transcription, and protein expression. The transfer of EVs to target cells, in turn, supports cancer growth, immunosuppression, and metastasis formation. This review focuses exclusively on breast cancer EVs with an emphasis on breast cancer-derived exosomes, keeping in mind that breast cancer-derived EVs share some common physical properties with EVs of other cancers.