MMP2 and central nervous system cancer: It was found that MMP-2 expression in patients with high-grade gliomas was significantly higher than that in patients with low-grade gliomas (n = 24, OR = 6.54, CI = 4.98–8.60), and there was no significant heterogeneity in the meta-analysis (I2 = 0 %, P = 0.911) (Fig. 2).