GDF15 and metastatic melanoma: Indeed, the brain metastatic melanoma-microglia interaction altered the secretion of vascularization-promoting factors including angiopoietin-2 or IL-8 from melanoma cells, and of GDF15 (growth/differentiation factor 15, also known as Macrophage inhibitory cytokine-1 or MIC-1) and other inflammation-related cytokines from microglia cells, favoring the metastatic process [100,101,102].