EX-VIVO MALIGNANT GLIOMA-CELLS ARE SENSITIVE TO FAS (CD95 APO-1) LIGAND-MEDIATED APOPTOSIS/

Fas (also known as CD95/APO-1) is a cell surface receptor and member o f the tumor necrosis factor receptor superfamily which mediates apopto sis in sensitive cells upon oligomerization by specific antibodies or by its ligand (FasL). Recently, human glioma cell lines were found to be susceptible to Fas-mediated apoptosis triggered by cu-Fas antibodie s. However, whether the Fas system can also be targeted in ex vivo hig h grade gliomas is at present unknown. In the present investigation, a -Fas antibodies and Fast were tested in short-term monolayer cultures or in colony forming assays established from freshly resected tumors o f patients with anaplastic astrocytomas (WHO grade III) and glioblasto ma multiforme (WHO grade IV). Anti-Fas antibodies induced only moderat e apoptosis in four of the 19 tested glioma cell cultures. This contra sts Fast which induced apoptosis in all of the 19 tumor cell cultures analyzed. Mean cytotoxicity of glioma cell cultures treated for 48 h w ith alpha-Fas antibodies or FasL was 9.6% and 44.3%, respectively. Irr espective of whether alpha-Fas antibodies or FasL were used, pretreatm ent with recombinant hu (rhu) IFN-gamma and rhuTNF-alpha for 48 h did not sensitize glioma cells to Fas-mediated cytotoxicity. The long-term effect by Fast on tumor colony formation was more striking. Fast trea tment resulted in more than 90% inhibition of clonal tumor cell growth of all the eight high grade gliomas analyzed. These results suggest t hat Fas targeting by FasL but not by alpha-Fas antibodies may provide a promising approach for locoregional glioma treatment. (C) 1998 Elsev ier Science B.V. All rights reserved.