Suppression of glial tumor growth by expression of glial fibrillary acidicprotein

We examined the effect of expression of glial fibrillary acidic -protein (G FAP) on the tumor growth of astrocytoma in vivo. When rat astrocytoma C6 ce lls were injected subcutaneously in athymic mice, the cells produced tumors that grew rapidly. The tumor growth of C6 cells transfected with GFAP cDNA was significantly reduced compared to that of control NeoC6 cells transfec ted only with the neomycin resistant gene. After implantation of C6 cells t ransfected with mutated GFAP cDNA at the phosphorylation sites, the tumor g rowth was suppressed similar to that of the wild GFAP transfectants. To det ermine whether the cell growth suppression by GFAP is specific for astrogli al cells, we assessed the effect of GFAP on the cell growth of an L cell of fibroblast origin in vitro. By GFAP cDNA transfection, L cells showed morp hological changes, but the cell growth was not reduced. These results sugge st that GFAP is a critical regulator of the tumor growth of astrocytoma.