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Secreted extracellular vesicles (EVs) influence the tumor microenvironment and promote distal metastasis. Here we analyzed the involvement of melanoma-secreted EVs in lymph node pre-metastatic niche formation in murine models. We found that small EVs (sEVs) derived from metastatic melanoma cell lines were enriched in nerve growth factor (NGF) receptor (NGFR, p75NTR), spread through the lymphatic system and were taken up by lymphatic endothelial cells, reinforcing lymph node metastasis. Remarkably, sEVs enhanced lymphangiogenesis and tumor cell adhesion by inducing ERK kinase, nuclear factor (NF)-κB activation and intracellular adhesion molecule (ICAM)-1 expression in lymphatic endothelial cells. Importantly, ablation or inhibition of NGFR in sEVs reversed the lymphangiogenic phenotype, decreased lymph node metastasis and extended survival in pre-clinical models. Furthermore, NGFR expression was augmented in human lymph node metastases relative to that in matched primary tumors, and the frequency of NGFR+ metastatic melanoma cells in lymph nodes correlated with patient survival. In summary, we found that NGFR is secreted in melanoma-derived sEVs, reinforcing lymph node pre-metastatic niche formation and metastasis. we apologize to those authors whose work could not be cited due to size restrictions. We thank M. S. Soengas and the members of her laboratory for melanoma cells, primary melanocyte preparations and helpful discussions. We thank M. Detmar and S. Proulx for the mouse B16-F1R2 cell line. We are grateful to M. Yañez-Mo and M. Valés for antibodies against sEV markers. We thank D. Grela and A. Escobar from IESMAT for their support with the Zetasizer analysis. We thank G. Roncador, L. Maestre and J. L. Martinez Torrecuadrada for their help with the development and characterization of anti-NGFR antibodies and C. Villarroya Beltri for her help in flow cytometry analysis. This work was funded by the Starr Cancer Consortium (B.J.M., D.L. and H.P.), the US NIH (R01-CA169416), the Nancy C. and Daniel P. Paduano Foundation, the Children’s Cancer and Blood Foundation (H.P. and D.L.), the Melanoma Research Alliance, the Feldstein Foundation, RETOS SAF2017-82924-R (AEI/10.13039/501100011033/FEDER-UE), the Fundación Ramón Areces, the Fundación Bancaria ‘la Caixa’ (HR18-00256), ATRES-MEDIA AXA Foundation (CONSTANTES Y VITALES, una iniciativa de laSexta y Fundación AXA) and the Fundación Científica AECC (LABAE19027PEIN, GCB15152978SOEN-HP) (H.P.), the Malcolm Hewitt Wiener Foundation, the AHEPA Fifth District Cancer Research Foundation, the Hartwell Foundation and the Manning Foundation (D.L.). We are also grateful for the support of the Translational Network for the Clinical Application of Extracellular Vesicles (TeNTaCLES), RED2018-102411-T (AEI/10.13039/501100011033), the Ramón y Cajal Programme, the FERO Foundation, Comunidad of Madrid 2017-T2/BMD6026 (L.N.) and La Caixa Foundation (ID100010434, fellowship LCF/BQ/ES17/11600007) (A.H.-B.). The CNIO, certified as a Severo Ochoa Excellence Centre, is supported by the Spanish government through the ISCIII. No

EMILIN-1; Melanoma; Metàstasi EMILIN-1; Melanoma; Metástasis EMILIN-1; Melanoma; Metastasis Several studies have demonstrated that melanoma-derived extracellular vesicles (EVs) are involved in lymph node metastasis; however, the molecular mechanisms involved are not completely defined. Here, we found that EMILIN-1 is proteolyzed and secreted in small EVs (sEVs) as a novel mechanism to reduce its intracellular levels favoring metastasis in mouse melanoma lymph node metastatic cells. Interestingly, we observed that EMILIN-1 has intrinsic tumor and metastasis suppressive-like properties reducing effective migration, cell viability, primary tumor growth, and metastasis. Overall, our analysis suggests that the inactivation of EMILIN-1 by proteolysis and secretion in sEVs reduce its intrinsic tumor suppressive activities in melanoma favoring tumor progression and metastasis. The authors gratefully acknowledge the support of the following sources of funding: Fundación Ramon Areces, MINECO (SAF2014-54541-R), Ramón y Cajal Programme, Asociación Española Contra el Cáncer, Constantes y Vitales (ATRES MEDIA/AXA Foundation) and FERO Foundation. We are also grateful for the support of the support of the Translational NeTwork for the CLinical application of Extracellular VesicleS, TeNTaCLES. RED2018-102411-T (AEI/10.13039/501100011033) and MINECO-Severo Ochoa predoctoral program to support A.A.L thesis and short term stay in Italy to perform this study. The CNIO, certified as Severo Ochoa Excellence Centre, is supported by the Spanish Government through the Instituto de Salud Carlos III (ISCIII).

García-Silva et al. show for the first time that extracellular vesicles isolated from the exudative seroma obtained from the lymphatic drainage implanted in melanoma patients after lymphadenectomy can be interrogated for melanoma markers and BRAF mutations. Profiling the BRAFV600E mutation in this biofluid is a novel approach to predict disease relapse., Liquid biopsies from cancer patients have the potential to improve diagnosis and prognosis. The assessment of surrogate markers of tumor progression in circulating extracellular vesicles could be a powerful non-invasive approach in this setting. We have characterized extracellular vesicles purified from the lymphatic drainage also known as exudative seroma (ES) of stage III melanoma patients obtained after lymphadenectomy. Proteomic analysis showed that seroma-derived exosomes are enriched in proteins resembling melanoma progression. In addition, we found that the BRAFV600E mutation can be detected in ES-derived extracellular vesicles and its detection correlated with patients at risk of relapse., Graphical Abstract

International audience; Tumor extracellular vesicles (EVs) mediate the communication between tumor and stromal cells mostly to the benefit of tumor progression. Notably, tumor EVs travel in the bloodstream, reach distant organs, and locally modify the microenvironment. However, visualizing these events in vivo still faces major hurdles. Here, we describe an approach for tracking circulating tumor EVs in a living organism: we combine chemical and genetically encoded probes with the zebrafish embryo as an animal model. We provide a first description of tumor EVs’ hemodynamic behavior and document their intravascular arrest. We show that circulating tumor EVs are rapidly taken up by endothelial cells and blood patrolling macrophages and subsequently stored in degradative compartments. Finally, we demonstrate that tumor EVs activate macrophages and promote metastatic outgrowth. Overall, our study proves the usefulness and prospects of zebrafish embryo to track tumor EVs and dissect their role in metastatic niches formation in vivo.

SummaryTumor extracellular vesicles (tumor EVs) mediate the communication between tumor and stromal cells mostly to the benefit of tumor progression. Notably, tumor EVs have been reported to travel in the blood circulation, reach specific distant organs and locally modify the microenvironment. However, visualizing these eventsin vivostill faces major hurdles. Here, we show a new method for tracking individual circulating tumor EVs in a living organism: we combine novel, bright and specific fluorescent membrane probes, MemBright, with the transparent zebrafish embryo as an animal model. We provide the first description of tumor EVs’ hemodynamic behavior and document their arrest before internalization. Using transgenic lines, we show that circulating tumor EVs are uptaken by endothelial cells and blood patrolling macrophages, but not by leukocytes, and subsequently stored in acidic degradative compartments. Finally, we prove that the MemBright can be used to follow naturally released tumor EVsin vivo. Overall, our study demonstrates the usefulness and prospects of zebrafish embryo to track tumor EVsin vivo.HighlightsMemBright, a new family of membrane probes, allows for bright and specific staining of EVsZebrafish melanoma EVs are very similar to human and mouse melanoma EVs in morphology and protein contentThe zebrafish embryo is an adapted model to precisely track tumor EVs dynamics and fate in a living organism from light to electron microscopyCirculating tumor EVs are rapidly uptaken by endothelial cells and patrolling macrophagesCorrelated light and electron microscopy can be used in zebrafish to identify cells and compartments uptaking tumor EVsBlurbDispersion of tumor extracellular vesicles (EVs) throughout the body promotes tumor progression. However the behavior of tumor EVs in body fluids remains mysterious due to their small size and the absence of adapted animal model. Here we show that the zebrafish embryo can be used to track circulating tumor EVsin vivoand provide the first high-resolution description of their dissemination and uptake.

Liquid biopsies from cancer patients have the potential to improve diagnosis and prognosis. The assessment of surrogate markers of tumor progression in circulating extracellular vesicles could be a powerful non-invasive approach in this setting. We have characterized extracellular vesicles purified from the lymphatic drainage also known as exudative seroma (ES) of stage III melanoma patients obtained after lymphadenectomy. Proteomic analysis showed that seroma-derived exosomes are enriched in proteins resembling melanoma progression. In addition, we found that the

During metastasis, tumour cells must communicate with their microenvironment by secreted soluble factors and extracellular vesicles. Different stromal cell types (e.g. bone marrow–derived cells, endothelial cells and fibroblasts) influence the growth and progression of tumours. In recent years, interest has extended to other cell types in the tumour microenvironment such as adipocytes and adipose tissue–derived mesenchymal stem cells. Indeed, obesity is becoming pandemic in some developing countries and it is now considered to be a risk factor for cancer progression. However, the true impact of obesity on the metastatic behaviour of tumours is still not yet fully understood. In this ‘Perspective’ article, we will discuss the potential influence of obesity on tumour metastasis, mainly in melanoma, breast and ovarian cancer. We summarize the main mechanisms involved with special attention to the role of extracellular vesicles in this process. We envisage that besides having a direct impact on tumour cells, obesity systemically preconditions the tumour microenvironment for future metastasis by favouring the formation of pro-inflammatory niches. This article is part of the discussion meeting issue ‘Extracellular vesicles and the tumour microenvironment’.

Neuroblastoma (NB) is the most common extracranial pediatric solid tumor. Around 70% of patients with metastatic disease at diagnosis present bone-marrow infiltration, which is considered a marker of poor outcome; however, the mechanism underlying this specific tropism has to be elucidated. Tumor-derived exosomes may support metastatic progression in several tumors by interacting with the microenvironment, and may serve as tumor biomarkers. The main objective of this study is to identify an exosomal signature associated with NB metastatic bone-marrow dissemination. Therefore, the proteomic cargo of exosomes isolated from NB cell lines derived from primary tumor and bone-marrow metastasis is characterized. The comparison among exosomal proteins show 15 proteins exclusively present in primary tumor-derived exosomes, mainly involved in neuronal development, and 6 proteins in metastasis-derived exosomes related to cancer progression. Significant proteins obtain with statistical analysis performed between the two groups, reveal that primary tumor exosomes contain a higher level of proteins involved in extra-cellular matrix (ECM) assembly and adhesion, as well as in neuronal development. Exosomes isolated from bone-marrow metastasis exhibit proteins involved in ameboidal cell migration and mitochondrial activity. This work suggests that proteomic profiling of NB-derived exosomes reflects the tumor stage and may be considered as potential tumor biomarker.