MMP9 and central nervous system cancer: Based on the assessment of POSTN, CHI3L1, SAA1, and MMP9 expression levels in patients with glioma, the risk score was computed for each patient, leading to the classification of patients into high-risk and low-risk categories; the cut-off to determine high and low risk was set as the median risk score obtained from TCGA cohort (Fig. 3E).