GFAP and central nervous system cancer: The measured GFAP and MMP-9 expression levels showed that the high-grade cell lines (U87/U118/U251) possessed a lower level of differentiation and a higher invasion ability than the low-grade cell lines (CHG5/SHG44), indicative of the consistency between the malignant degree of cell lines and the pathology grades of their glioma tissues after continuous subculture in vitro.