For instance, the occurrence of melanoma brain metastasis was significantly hindered under microglia and macrophages elimination with PLX3397, a CSF-1R inhibitor; their depletion effectively inhibited the expression of matrix metalloproteinase 3 (MMP3) and the decrease of tight junction protein zonula occludens-1 (ZO-1), correlated with myeloid cells activation (171). This evidence concerns the gene MMP3 and melanoma.