Melanoma (B16-F10) and breast (MDA-MB-231) cancer cell lines increase the permeability of lung blood vessels before metastasis by the production of vasoactive factors such as angiopoietin (Angpt) 2 and 4, matrix metalloproteinases (MMP) 1, 2, 3, and 10 and downstream effectors of VEGF (epiregulin and cyclooxygenase 2). This evidence concerns the gene PTGS2 and melanoma.