Among all these studies, the correlation between the ratio of MMP-2 and TIMP-2 (MMP-2/TIMP-2) and the WHO grade of gliomas was offered in two studies [16, 39] and two studies [24, 27] provided the data of age and gender which were associated with the WHO grade of gliomas, and only one study [41] about MMP-2 expression reported the overall survival (OS) of patients. The gene discussed is MMP2; the disease is central nervous system cancer.