Uveal Melanoma Exosomes Induce a Prometastatic Microenvironment through Macrophage Migration Inhibitory Factor

Uveal melanoma is a rare melanoma subtype different from cutaneous melanoma, with high incidence of liver metastasis and poor prognosis. Cancer cell-derived extracellular vesicles have been shown to induce proinflammatory and prometastatic signaling in the tumor microenvironment and at distant sites. The characterization of uveal melanoma exosome cargo and its role in metastatic spread is essential to identify targets and intervene in the early stages of metastatic development. Our study characterizes the proteomic content of uveal melanoma exosomes and identified the presence of markers with metastatic properties. We demonstrated that uveal melanoma exosomes induce activation of cell signaling pathways and the release of cytokines and growth factors from hepatocytes. These exosome-stimulated liver cells could in turn induce migration of uveal melanoma cells, confirming that the exosomes have a functional role in the cross-talk between these two cell types. We found that the proinflammatory cytokine macrophage migration inhibitory factor (MIF) was a major player in these mechanisms and its blockade inhibited cell migration in coculture with exosome-stimulated hepatocytes and prevented the development of metas-tases in vivo. Targeting MIF in the early stages of metastasis may represent a novel adjuvant drug therapy to prevent metastatic spread in uveal melanoma.