MMP9 and glioma: Lactic acidosis induces production of matrix metalloproteinase-9 (MMP-9) in mouse B16 melanoma (67), VEGF-A in glioma and glioblastoma cells (68, 69), and IL-8 expression in pancreatic adenocarcinoma (70, 71) and ovarian carcinoma cells (72), all making the tumor microenvironment even more complex.