Moreover, the results of the pooled analysis indicated that there was no association between TIMP-2 expression and the WHO grade of gliomas (n = 7, OR = 1.02, 95 % CI = 0.68–1.54; I2 = 71.4 %, P = 0.002), but the ratio of MMP-2 and TIMP-2 (MMP-2/TIMP-2) rose with the increase of the WHO grade of gliomas. The gene discussed is MMP2; the disease is central nervous system cancer.