MMP9 and glioblastoma: For example, Chiu et al. reported that 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation, through the activation of protein kinase C (PKC) and ERKs, increased the COX-2 gene expression; elevated PGE2 production; and promoted matrix metalloproteinase-9 (MMP-9) activation, which induced in vitro migration/invasion in U87 glioblastoma cells [110].