MMP9 and glioblastoma: In the present study, we comparatively analyzed the MMP family members based on whole-gene expression profiling from multiple databases (Table 1), and found that MMP9 expression is correlated with glioma grade (p<0.0001, Fig 1A) and that low MMP9 expression is an independent prognostic factor for better survival in primary GBM patients (OS: p = 0.027 and PFS: p = 0.032).