MMP9 and central nervous system cancer: Since we previously found that MMP9 and MUC4 were upregulated in the tissue of patients with higher glioma grades (Fig. 1), we further assessed the protein levels of these two proteins in the serum of 30 patients (10 benign non-glioma tumors (controls), 10 glioma grade III, and 10 glioma grade IV) using ELISA immunoassays.