Fas Ligand-independent, FADD-mediated Activation of the Fas Death Pathway by Anticancer Drugs

• Published in: The Journal of biological chemistry 1999-03, Vol.274 (12), p.7987-7992
• Main Authors: Micheau, O, Solary, E, Hammann, A, Dimanche-Boitrel, M T
• Format: Article
• Language: English
• Subjects: Antigens, Surface - metabolism; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Arabidopsis Proteins; Cisplatin - pharmacology; Etoposide - pharmacology; Fas Ligand Protein; fas Receptor - metabolism; Fatty Acid Desaturases - biosynthesis; Fatty Acid Desaturases - genetics; Fatty Acid Desaturases - metabolism; Flow Cytometry; Gene Expression Regulation - drug effects; Humans; Jurkat Cells; Ligands; Membrane Glycoproteins - metabolism; Oligonucleotides, Antisense - metabolism; Plant Proteins - biosynthesis; Plant Proteins - genetics; Plant Proteins - metabolism; Receptors, Tumor Necrosis Factor - metabolism; Transfection; Tumor Cells, Cultured; U937 Cells; Vinblastine - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.12.7987

Trimerization of the Fas receptor (CD95, APO-1), a membrane bound protein, triggers cell death by apoptosis. The main death pathway activated by Fas receptor involves the adaptor protein FADD (for F as- a ssociated d eath d omain) that connects Fas receptor to the caspase cascade. Anticancer drugs have been shown to enhance both Fas receptor and Fas ligand expression on tumor cells. The contribution of Fas ligand-Fas receptor interactions to the cytotoxic activity of these drugs remains controversial. Here, we show that neither the antagonistic anti-Fas antibody ZB4 nor the Fas-IgG molecule inhibit drug-induced apoptosis in three different cell lines. The expression of Fas ligand on the plasma membrane, which is identified in untreated U937 human leukemic cells but remains undetectable in untreated HT29 and HCT116 human colon cancer cell lines, is not modified by exposure to various cytotoxic agents. These drugs induce the clustering of Fas receptor, as observed by confocal laser scanning microscopy, and its interaction with FADD, as demonstrated by co-immunoprecipitation. Overexpression of FADD by stable transfection sensitizes tumor cells to drug-induced cell death and cytotoxicity, whereas down-regulation of FADD by transient transfection of an antisense construct decreases tumor cell sensitivity to drug-induced apoptosis. These results were confirmed by transient transfection of constructs encoding either a FADD dominant negative mutant or MC159 or E8 viral proteins that inhibit the FADD/caspase-8 pathway. These results suggest that drug-induced cell death involves the Fas/FADD pathway in a Fas ligand-independent fashion.