In addition to being a marker of matured astrocytes, GFAP is considered to be important for the induction and maintenance of astrocyte differentiation, because introduction of GFAP to C6 cells and human astrocytoma induced morphological changes, and suppressed their proliferation and invasive potential (Rutka and Smith, 1993; Toda et al, 1994). This evidence concerns the gene GFAP and astrocytoma (excluding glioblastoma).