Role Of Tumor-derived Exosomes Research Articles

New roles of tumor-derived exosomes in tumor microenvironment.

Throughout tumorigenesis, the co-evolution of tumor cells and their surrounding microenvironment leads to the development of malignant phenotypes. Cellular communication within the tumor microenvironment (TME) plays a critical role in influencing various aspects of tumor progression, including invasion and metastasis. The release of exosomes, a type of extracellular vesicle, by most cell types in the body, is an essential mediator of intercellular communication. A growing body of research indicates that tumor-derived exosomes (TDEs) significantly expedite tumor progression through multiple mechanisms, inducing epithelial-mesenchymal transition and macrophage polarization, enhancing angiogenesis, and aiding in the immune evasion of tumor cells. Herein, we describe the formation and characteristics of the TME, and summarize the contents of TDEs and their diverse functions in modulating tumor development. Furthermore, we explore potential applications of TDEs in tumor diagnosis and treatment.

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

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

Role of tumor-derived exosomes in metastasis, drug resistance and diagnosis of clear cell renal cell carcinoma.

Renal cancer is one of the most extensively studied human tumors today, with clear cell renal cell carcinoma accounting for approximately 80% of all cases. Despite recent advances in research on clear cell renal cell carcinoma, advanced distant metastasis of the disease, delay in diagnosis, as well as drug resistance remain major problems. In recent years, as an important mediator of material and information exchange between cells in the tumor microenvironment, exosomes have attracted widespread attention for their role in tumor development. It has been reported that tumor-derived exosomes may act as regulators and have an important effect on the metastasis, drug resistance formation, and providing targets for early diagnosis of clear cell renal cell carcinoma. Therefore, the extensive study of tumour-derived exosomes will provide a meaningful reference for the development of the diagnostic and therapeutic field of clear cell renal cell carcinoma. This article reviews the biological role and research progress of tumor-derived exosomes in different aspects of premetastatic niche formation, tumor angiogenesis, and epithelial-mesenchymal transition during the progression of clear cell renal cell carcinoma. In addition, the role of tumor-derived exosomes in the development of drug resistance in clear cell renal cell carcinoma is also addressed in this review. Furthermore, recent studies have found that cargoes of exosomes in serum and urine, for example, a series of miRNAs, have the potential to be biological markers of clear cell renal cell carcinoma and provide meaningful targets for early diagnosis and monitoring of tumors, which is also covered in this article.

Tumor-derived exosomal non-coding RNAs as diagnostic biomarkers in cancer.

Almost all clinical oncologists agree that the discovery of reliable, accessible, and non-invasive biomarkers is necessary to decrease cancer mortality. It is possible to employ reliable biomarkers to diagnose cancer in the early stages, predict the patient prognosis, follow up the response to treatment, and estimate the risk of disease recurrence with high sensitivity and specificity. Extracellular vesicles (EVs), especially exosomes, have been the focus of translational research to develop such biomarkers over the past decade. The abundance and distribution of exosomes in bodily fluids, including serum, saliva, and urine, as well as their ability to transport various biomolecules (nucleic acids, proteins, and lipids) derived from their parent cells, make exosomes reliable, accessible, and potent biomarkers for diagnosis and follow-up of solid and hematopoietic tumors. In addition, exosomes play a vital role in various cellular processes, including tumor progression, by participating in intercellular communication. Although these advantages underline the high potential of tumor-derived exosomes as diagnostic biomarkers, the lack of standardized effective methods for their isolation, identification, and precise characterization makes their application challenging in clinical settings. We discuss the importance of non-coding RNAs (ncRNAs) in cellular processes, and the role of tumor-derived exosomes containing ncRNAs as potential biomarkers in several types of cancer. In addition, the advantages and challenges of these studies for translation into clinical applications are covered.

Exosomal circular RNA hsa_circ_007293 promotes proliferation, migration, invasion, and epithelial–mesenchymal transition of papillary thyroid carcinoma cells through regulation of the microRNA-653-5p/paired box 6 axis

ABSTRACT Circular RNAs (circRNAs) or exosomes have been reported to exert key regulatory and/or communication functions in human cancer. Nevertheless, current literature on the effects of exosomal circRNAs on tumor invasion and metastasis in thyroid cancer is incomplete. The role of tumor-derived exosomes in driving in vitro papillary thyroid carcinoma (PTC) progression and metastasis requires further investigation. In our study, Exosomes were harvested from PTC patient serum and PTC cell culture medium. Gene expression analysis in PTC cell lines and exosomes was performed with quantitative reverse-transcription polymerase chain reaction. Transwell, wound healing, Western blot assays, and the cell counting kit-8 were applied for functional analysis. Dual-luciferase reporter assay was used to examine the interaction between hsa_circ_007293 (circ007293), microRNA (miR)-653-5p, and paired box 6 (PAX6). Results showed that circ007293 was enriched in exosomes derived from PTC patient serum and cell culture media. Moreover, circ007293 could enter PTC cells through exosomes, and exosomal circ007293 promoted PTC cell epithelial–mesenchymal transition, invasion, migration, and proliferation. circ007293 knockdown reversed the malignant phenotype of PTC cells in vitro. Additionally, circ007293 could competitively bind with miR-653-5p to regulate PAX6 expression. Notably, miR-653-5p overexpression or PAX6 inhibition suppressed the malignant effects of exosomal circ007293. These results evidenced that exosomal circ007293 induced EMT and augmented the invasive and migratory abilities of PTC cells via the miR-653-5p/PAX6 axis, suggesting that it may serve as a promising biomarker for cancer progression.

The Role of Tumor-Derived Exosomes (TEX) in Shaping Anti-Tumor Immune Competence.

Emerging studies suggest that extracellular vesicles (EVs) mediating intercellular communication in the tumor microenvironment (TME) play a key role in driving cancer progression. Tumor-derived small EVs or exosomes (TEX) enriched in immunosuppressive proteins or in microRNAs targeting suppressive pathways in recipient cells contribute to reprogramming the TME into a cancer-promoting milieu. The adenosinergic pathway is an acknowledged major contributor to tumor-induced immune suppression. TEX carry the components of this pathway and utilize ATP to produce adenosine (ADO). TEX-associated ADO emerges as a key factor in the suppression of T cell responses to therapy. Here, the significance of the ADO pathway in TEX is discussed as a highly effective mechanism of cancer-driven immune cell suppression and of resistance to immune therapies.

Exosomes from cervical cancer cells facilitate pro-angiogenic endothelial reconditioning through transfer of Hedgehog\u2013GLI signaling components

BackgroundAngiogenic switch is a hallmark feature of transition from low-grade to high-grade cervical intraepithelial neoplasia (CIN) in cervical cancer progression. Therefore, early events leading to locally-advanced cervical metastatic lesions demand a greater understanding of the underlying mechanisms. Recent leads indicate the role of tumor-derived exosomes in altering the functions of endothelial cells in cervical cancer, which needs further investigation.MethodsExosomes isolated from cervical cancer cell lines were assessed for their angiogenic effect on the human umbilical vein endothelial cells (HUVEC) using tube formation and wound healing assay. The exosomal uptake by HUVEC cells was monitored using PKH-67 labelling followed by fluorescence microscopy. Alterations in Hh-GLI signaling components, PTCH1 and GLI1, in HUVEC were measured by immunoblotting. Changes in angiogenesis-related transcripts of vascular endothelial growth factor VEGF-A, VEGF-B, VEGFR2 and angiopoietin-1, angiopoietin-2, osteopontin were measured in exosome-treated HUVEC and in the exosomal RNA by RT-PCR.ResultsEnhanced tube formation, with an increased number of nodes and branching was observed in HUVEC’s treated with exosomes derived from different cervical cancer cell lines. HPV-positive (SiHa and HeLa) cells’ exosomes were more angiogenic. Exosome-treated HUVEC showed increased migration rate. PKH-67 labelled exosomes were found internalized in HUVEC. A high level of PTCH1 protein was detected in the exosome—treated endothelial cells. Subsequent RT-PCR analysis showed increased transcripts of Hh-GLI downstream target genes VEGF-A, VEGFR2, angiopoietin-2, and decreased expression of VEGF-B, and angiopoietin-1, suggestive of active Hh-GLI signaling. These effects were more pronounced in HUVEC’s treated with exosomes of HPV-positive cells. However, these effects were independent of tumor-derived VEGF-A as exosomal cargo lacked VEGF-A transcripts or proteins.ConclusionOverall, the data showed cervical cancer exosomes promote pro-angiogenic response in endothelial cells via upregulation of Hh-GLI signaling and modulate downstream angiogenesis-related target genes. The study provides a novel exosome-mediated mechanism potentially favoring cervical angiogenesis and thus identifies the exosomes as potential pharmacological targets against locally-advanced metastatic cervical lesions.Graphic abstract

The Role of Tumor-Derived Exosomes in the Abscopal Effect and Immunotherapy.

Exosomes are microvesicles that can be secreted by various cells and carry a variety of contents; thus, they play multiple biological functions. For instance, the tumor-derived exosomes (TEXs) have been proven to have the effect of immunostimulatory in addition to immunosuppression, making TEXs attractive in clinical immunotherapy and targeted therapy for cancer patients. In addition, TEXs as biomarkers have important clinical diagnostic and prognostic value. Recently, TEXs have been recognized to play important roles in the abscopal effect (AbE), a newly discovered mechanism by which the distant tumors are effectively targeted and repressed during immunotherapy and radiotherapy. Therefore, TEXs has demonstrated great clinical potential in the diagnosis, prognosis and treatment of cancer patients in the future. This review summarizes and discusses the role of TEXs in clinical therapy and their role in AbE in recent studies.

The role of tumor-derived exosomes in tumor immune escape: A concise review

Exosomes are small vesicles secreted by viable cells into the microenvironment. These vesicles bring various compositions, including lipids, RNAs and proteins, which carry information from producer cells to target cells. Cancer cells also produce exosomes, termed as tumor-derived exosomes (TDEs), which play important roles in immune modulation, angiogenesis and metastasis of tumors. This review summarizes the roles of TDEs in tumor immune escape mechanisms. TDEs affect all kinds of tumor-associated immune cells, including natural killer (NK) cells, dendritic cells (DCs), T and B lymphocytes, and myeloid-derived suppressor cells (MDSCs). Generally, TDEs suppress the immune system to promote tumor immune escape, thereby significantly contributing to tumorigenesis and metastasis.

EL4-derived Exosomes Carry Functional TNF-related Apoptosis-inducing Ligand that are Able to Induce Apoptosis and Necrosis in the Target Cells.

Exosomes released by tumor cells play critical roles in tumor progression, immune cell suppression, and cancer metastasis. The aim of the present study was to investigate whether the exosomes released by EL4 cells carry a functional TNF-related apoptosis-inducing ligand (TRAIL) molecule. Exosomes were harvested from the supernatants of EL4 cell culture, and the shape, size, and identity of EL4-derived exosomes were evaluated by utilizing scanning electron microscopy, dynamic light scattering, and dot-blot method. The expression of mRNA and TRAIL protein in EL4 cells and EL4-exosomes were investigated using real-time PCR method and dot-blot analysis. Moreover, the effects of EL4-derived exosomes on cell death in a TRAIL-sensitive cell line (4T1) were studied by using flow cytometry (annexin V/propidium iodide (PI) staining) and fluorescent microscopy analyses (acridine orange/ethidium bromide staining). The results showed that EL4 cells continuously and without the need for stimulation, produce exosomes that carry TRAIL protein. In addition, EL4-derived exosomes were capable to induce apoptosis as well as necrosis in 4T1 cells. It was ultimately revealed that EL4 cells express TRAIL protein and release exosomes containing functional TRAIL. Moreover, the released exosomes were able to induce apoptosis and necrosis in a TRAIL-sensitive cell line. Further studies are needed to reveal the potential roles of tumor-derived exosomes in the pathogenesis of cancers.

The role of tumor-derived exosomes in tumor angiogenesis and tumor progression

Abstract Exosomes, belonging to the group of extracellular bodies, are released by healthy as well as cancerous cells and serve as a communication pathway. Tumor-derived exosomes (TEX) possess the capacity to reprogram the function of normal cells owing to their genetic and molecular cargo. Such exosomes target endothelial cells (among others) in the tumor microenvironment to promote angiogenesis. Blood supply is essential in solid tumor growth and metastasis. The potential of pro-angiogenic changes is enhanced by an increased amount of circulating tumor-derived exosomes in the body fluids of cancer patients. A vascular network is important, since the proliferation, as well as the metastatic spread of cancer cells depends on an adequate supply of oxygen and nutrients, and the removal of waste products. New blood vessels and lymphatic vessels are formed through processes called angiogenesis and lymphangiogenesis, respectively. Angiogenesis is regulated by both activator and inhibitor molecules. Thousands of patients have received anti-angiogenic therapy to date. Despite their theoretical efficacy, anti-angiogenic treatments have not proved beneficial in terms of long-term survival. Tumor-derived exosomes carrying pro-angiogenic factors might be a target for new anti-cancer therapy.

Exosomes Derived from Human Primary and Metastatic Colorectal Cancer Cells Contribute to Functional Heterogeneity of Activated Fibroblasts by Reprogramming Their Proteome.

Cancer-associated fibroblasts (CAFs) are a heterogeneous population of activated fibroblasts that constitute a dominant cellular component of the tumor microenvironment (TME) performing distinct functions. Here, the role of tumor-derived exosomes (Exos) in activating quiescent fibroblasts into distinct functional subtypes is investigated. Proteomic profiling and functional dissection reveal that early- (SW480) and late-stage (SW620) colorectal cancer (CRC) cell-derived Exos both activated normal quiescent fibroblasts (α-SMA- , CAV+ , FAP+ , VIM+ ) into CAF-like fibroblasts (α-SMA+ , CAV- , FAP+ , VIM+ ). Fibroblasts activated by early-stage cancer-exosomes (SW480-Exos) are highly pro-proliferative and pro-angiogenic and display elevated expression of pro-angiogenic (IL8, RAB10, NDRG1) and pro-proliferative (SA1008, FFPS) proteins. In contrast, fibroblasts activated by late-stage cancer-exosomes (SW620-Exos) display a striking ability to invade through extracellular matrix through upregulation of pro-invasive regulators of membrane protrusion (PDLIM1, MYO1B) and matrix-remodeling proteins (MMP11, EMMPRIN, ADAM10). Conserved features of Exos-mediated fibroblast activation include enhanced ECM secretion (COL1A1, Tenascin-C/X), oncogenic transformation, and metabolic reprogramming (downregulation of CAV-1, upregulation of glycogen metabolism (GAA), amino acid biosynthesis (SHMT2, IDH2) and membrane transporters of glucose (GLUT1), lactate (MCT4), and amino acids (SLC1A5/3A5)). This study highlights the role of primary and metastatic CRC tumor-derived Exos in generating phenotypically and functionally distinct subsets of CAFs that may facilitate tumor progression.

Tumor-derived exosomes: Potential biomarkers and therapeutic target in the treatment of colorectal cancer.

Colorectal cancer (CRC) is the third most common cause of cancer-related death in men and women in many countries. Early detection of CRC helps to prevent the advanced stages of the disease, and may thereby improve the survival of these patients. A noninvasive test with high specificity and sensitivity is required for this. Exosomes are lipid bilayer membrane nanovesicles that are released into most body fluids and especially in the microenvironment of cancer. They carry various proteins, lipids, and nucleic materials such as DNA, RNA, messenger RNA (mRNA), and microRNA (miRNA), and may also alter the function of target cells. In this review, we aimed to describe the biogenesis, composition, function, and the role of tumor-derived exosomes in cancer progression. Moreover, their applications in tumor diagnosis and treatment are described, with a particular focus on CRC.

Role of tumor-derived exosomes in facilitating pre-metastatic niche formation

Role of tumor-derived exosomes in facilitating pre-metastatic niche formation

The role of tumor-derived exosomes in the formation of a pre-metastatic niche in cancer

Abstract Purpose Determine if tumor derived exosomes (TDE) can drive cancer progression through polarization of immunosuppressive cell phenotypes capable of restricting αβ T cell functioning. Preliminary data shows that exosome stimulation differentially upregulates PD-L1 (programmed-death-ligand-1) expression on peritoneal macrophages and lung resident γδ T cells while also upregulating PD-1 expression on αβ T cells. The ultimate goal is to assess whether elimination of TDE can synergize with current PD-1/PD-L1 treatments by removing antagonizing factors and improving clinical outcomes. Methods TDE were isolated using serial ultracentrifugation from Lewis Lung Carcinoma cells. Exosome stimulated peritoneal macrophages and γδ T cells were co-cultured with ova-transgenic –I (CD8+) T-cells to assay for suppressive function. Anti-PD-1 antibody was added to the culture to confirm that the PD-1/PDL-1 axis mediates the immune suppression. The effect of TDE on γδ T cell metabolism was also investigated. Lastly, human peripheral blood samples from lung cancer and anti-PD-1 treated lung cancer patients were compared via flow cytometry for γδ/PD-L1 expression profiling. Results The results suggest that TDE play a role in tumor metastasis by polarizing γδ T cells and macrophages to an immunosuppressive PD-L1+ phenotype capable of restricting αβ T cell effector functioning. Discussion/Conclusion TDE could be directly antagonizing the effects of immune checkpoint therapies. Therefore, future experiments will focus on eliminating exosome secretion by using siRNARab27 inhibition and the small drug compound, cambinol, concurrently with anti-PD-1 or anti-PD-L1 monoclonal antibody in efforts to increase progression free survival.

Tumor-derived exosomes educate dendritic cells to promote tumor metastasis via HSP72/HSP105-TLR2/TLR4 pathway

ABSTRACTHow the tumor microenvironment educates dendritic cells (DCs) to promote tumorigenesis remains largely unknown, and the role of tumor-derived exosomes (TEXs) in tumorigenesis is controversial. Here, we report that in addition to the activation of DCs, TEXs induce DCs to produce increased interleukin-6 (IL-6), which dramatically promotes tumor invasion by increasing signal transducer and activator of transcription 3 (STAT3)-dependent matrix metalloproteinases 9 transcription activity in tumor cells. HSP72 and HSP105 on the TEX surface induce IL-6 secretion of DCs in a TLR2- and TLR4-dependent manner. In addition, HSP72 and HSP105 are predominantly present on exosomes from sera of tumor patients but not healthy people, indicating their value in tumor prediction. Furthermore, TEXs are powerful activators of DCs, and the depletion of IL-6 converts TEXs from tumor promoters to tumor inhibitors in vivo. Therefore, our results reveal a novel mechanism for the TEX-mediated education of DCs and shed light on the conundrum that TEXs present by playing dual roles in tumorigenesis.

Abstract 5808: The role of breast cancer-derived exosomes in brain metastasis

Abstract The development of brain metastasis is associated with a significant reduction in the survival rate of breast cancer patients. Improving the prognosis of women with brain metastasis from breast cancer relies on the elucidation of the mechanisms underlying this process. Our group and others have shown that the formation of brain metastases occurs along the abluminal side of brain vessels, a process called “vessel co-option”. These observations prompted our hypothesis that the cellular and extracellular matrix (ECM) components of the blood-brain-barrier (BBB) can serve as a pre-metastatic niche for breast cancer brain metastases. The role of tumor-derived exosomes (TEx) in the preparation of a pre-metastatic niche in distant organs has been shown in a number of cancers. To investigate the mechanisms driving the vessel co-option of breast cancer brain metastases, we studied the role of breast cancer-derived exosomes in preparation of the BBB for metastasis formation. Exosomes were isolated from the MDA-MB-231 breast cancer cell line, a brain-seeking variant of these cells, and a bone-seeking variant as a non-brain metastatic control. Brain endothelial cells, astrocytes, and brain vascular pericytes, the three components of the BBB, were treated with exosomes for 3 days to recapitulate the continuous exposure of cells to the circulating TEx in vivo. The treated cells were analyzed for cellular activities relevant to pre-metastatic niche preparation in the brain such as the integrity of the BBB, expression of cytokines, and modulation of the ECM. An initial screen was performed using cytokine antibody arrays and PCR arrays for ECM and adhesion molecules and results were validated in three separate experiments using western blots, ELISA, and Multiplex assays. Exosomes derived from brain-seeking cells significantly increased astrocyte migration and decreased the expression of Integrin β1 in brain endothelial cells, both of which can lead to the disruption of the BBB integrity. Moreover, the expression of Interleukin 8 was increased by TEx in astrocytes. TEx also increased the expression of MMP-3 and -9 (Matrix Metalloproteinases) from an undetectable baseline level and decreased the expression of TIMP-1 and -2 (Tissue Inhibitors of MMPs) in astrocytes. While the importance of these two MMPs for brain metastasis from breast cancer has been previously reported, our study is the first to demonstrate that secretion of these MMPs is triggered by TEx. Surprisingly, we did not observe any significant TEx-derived modulations in the expression of cytokines, ECM, and adhesion molecules in brain pericytes. These findings indicate that within the BBB, astrocytes and endothelial cells, but not pericytes, can be affected by breast cancer-derived exosomes in such a way that can potentially lead to preparation of a suitable niche for future metastasis formation along the brain vasculature. (This work is supported by the Breast Cancer Research Foundation.) Citation Format: Golnaz Morad, Jiang Yang, Marsha A. Moses. The role of breast cancer-derived exosomes in brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5808. doi:10.1158/1538-7445.AM2017-5808

The role of tumor-derived exosomes in epithelial mesenchymal transition (EMT).

Exosomes are membrane-bound small vesicles (30–150 nm) produced by all cell types and present in all body fluids (1). They are a part of the intercellular communication system that is evolutionarily conserved and operates in bacteria as well as all multicellular organisms (2). Tumor cells produce and release masses of exosomes into the extracellular space. These exosomes carry information in the form of molecular signals and/or genetic materials (mRNA, miRNA, DNA) from the parent tumor cell to locally- or distantly-located recipient cells. Exosome-mediated transfer of information results in re-programming of the recipient cell genome and proteome and ultimately leads to the acquisition of new cellular functions (3).

The roles and implications of exosomes in sarcoma.

Better diagnostic biomarkers and therapeutic options are still necessary for patients with sarcomas due to the current limitations of diagnosis and treatment. Exosomes are small extracellular membrane vesicles that are released by various cells and are found in most body fluids. Tumor-derived exosomes have been proven to mediate tumorigenesis, intercellular communication, microenvironment modulation, and metastasis in different cancers, including in sarcomas. Recently, exosomes have been considered as potential biomarkers for sarcoma diagnosis and prognosis, and as possible targets for sarcoma therapy. Moreover, due to their specific cell tropism and bioavailability, exosomes can also be engineered as vehicles for drug delivery. In this review, we discuss recent advances in the roles of tumor-derived exosomes in sarcoma and their potential clinical applications.

Abstract 5205: Docosahexaenoic acid (DHA) alters breast cancer exosome-mediated microRNA signaling

Abstract DHA is a long-chain omega-3 polyunsaturated fatty acid that has anticancer properties, including the ability to suppress tumor angiogenesis. However, the precise mechanism of DHAs anti-angiogenic activity is not well defined. It is recognized that the intercommunication between cancer cells and their microenvironment is essential to tumor angiogenesis. Exosomes are nanometer-sized extracellular vesicles that are important mediators of intercellular communication and in recent years, the role of tumor-derived exosomes in cancer progression has been realized. However, ways to limit or alter their influence on cancer progression has not been demonstrated. At this time, very little is known about the role of breast cancer derived exosomes in contributing to breast cancer progression and whether these exosomes mediate DHAs anticancer activity. To investigate, breast cancer exosomes were collected from the conditioned media of MCF7 and MDA-MB-231 breast cancer cells engineered to express GFP-tagged CD63 after treatment with DHA. We observed an increase in exosome secretion from the DHA-treated cells. Total RNA was extracted from the DHA-treated and control MCF7-derived exosomes and analyzed by small RNA sequencing. The expression of 83 exosome microRNAs was altered by DHA (>2-fold) and several of the most abundant exosomal microRNAs (miR-23b, miR-27a/b, miR-21, and miR-320b) are known to have anti-angiogenic activity. When DHA-treated MCF7 cells were co-cultured with or the collected exosomes were directly applied to endothelial cell cultures, we observed an increase in the expression of these microRNAs in endothelial cells. Furthermore, overexpression of miR-23b and miR-320b in endothelial cells decreased the expression of their pro-angiogenic target genes (PLAU, AMOTL1, NRP1 and ETS2) and significantly inhibited tube formation by endothelial cells, an effect that could be reversed by inhibition of exosome secretion via Rab27A knockdown. These results suggest that the microRNAs transferred by exosomes mediate DHAs anti-angiogenic action. Our data demonstrates that DHA alters breast cancer exosome secretion and microRNA contents that leads to the inhibition of endothelial tube formation. These results provide insight into the future possibility of developing new cancer therapeutic strategies targeting exosome secretion and content transmission. Citation Format: Bethany N. Hannafon, Karla Carpenter, William Berry, Ralf Janknecht, William Dooley, Wei-Qun Ding. Docosahexaenoic acid (DHA) alters breast cancer exosome-mediated microRNA signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5205. doi:10.1158/1538-7445.AM2015-5205