MMP9 and central nervous system cancer: Considering the volume average of each individual band, we observed that enzymatic activity of both monomeric and multimeric forms of MMP-9 are significantly higher in high-grade glioma, in low- and high-grade meningioma samples as well as in metastasis specimens compared to healthy individuals (p < 0.001) (Fig. 1, panel b, and Table 4).