Adenovirus-mediated overexpression of Fas induces apoptosis of gliomas

Gliomas express a higher amount of Fas than normal brain tissue. It is of i nterest to know whether expression of the Fas receptor is unfavorable to th e antiapoptotic pathways in gliomas. In this study, we introduced the Fas g ene via an adenovirus vector (Adeno-Fas) into the A-172, U251, and U-373 MG glioma cell lines, each of which expresses Fas on the cell surface. infect ion of Adeno-Fas induced apoptosis in each glioma cell line. In U251 cells and A-172 cells that express the same level of Fas as a result of infection with Adeno-fas, a much higher percentage of U251 cells underwent apoptosis than did A-172 cells. This suggests that each glioma cell line has its own threshold of Fas expression, above which apoptosis is induced, and that th e constitutive expression of Fas is below the level of this threshold. It w as found that the constitutive expression of the anti-apoptotic gene Bcl-X- L is higher in A-172 cells than in U251 cells. Adenovirus-mediated transduc tion of the Bcl-X-L gene into U251 cells effectively suppressed Adeno-Fas-m ediated apoptosis. These data indicate that the Bcl-X-L gene is one of the important determinants of the threshold for Fas-mediated apoptosis. When U2 51 and U-373 MG eel Is were transduced with the Fas gene controlled by the myelin basic protein promoter, which had been shown to be active in gliomas but not in neural tissues, the cells underwent markedly enhanced apoptosis . Taken together, these results indicate that the overexpression of Fas alo ne induced apoptosis in each glioma cell line. The degree of Fas-mediated a poptosis was attenuated by the expression of an anti-apoptotic gene, Bcl-X- L. The adenovirus-mediated induction of Fas gene controlled by a tissue-spe cific promoter (e.g., myelin basic protein promoter) would be a promising t herapeutic approach for malignant glioma.