Also, acidic microenvironments affect the expression of some genes, such as MMP-9 [74,75] and acidic sphingomyelinase in mouse B16 melanoma [74], platelet-derived endothelial cell growth factor (thymidine phosphorylase) in human breast cancer cells [76], the inducible isoform of nitric oxide synthase (iNOS) in macrophages [77], VEGF-A in glioma [78] and glioblastoma [79] cells, and IL-8 expression in human pancreatic adenocarcinoma [80-82] and ovarian carcinoma cells [83]. This evidence concerns the gene MMP9 and melanoma.