TNF and melanoma: Exo recruited into lymph nodes up-regulate the proteases that degrade the ECM as well as the pro-angiogenic factors tumor necrosis factor (TNF)-α, VEGF, hypoxia-inducible factor (HIF)-1 and urokinase plasminogen activator, thus enhancing melanoma cell recruitment, trapping and growth (Figure 2E) within the metastatic niche [56, 57].