Melanoma-derived small extracellular vesicles induce lymphangiogenesis and metastasis through an NGFR-dependent mechanism.

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 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.