title: Sensitization of osteosarcoma cells to death receptor-mediated apoptosis by HDAC inhibitors through downregulation of cellular FLIP.
abstract: Fas-mediated apoptosis plays an important role in elimination of tumor cells in vivo, but some tumor-derived cells are resistant to this mechanism. Here, we show that treatment with the histone deacetylase (HDAC) inhibitor FR901228 renders Fas-resistant osteosarcoma cell lines sensitive to Fas-mediated apoptosis by downregulating expression of cellular FLIP (cellular FLICE-inhibitory protein), an inhibitor of Fas-mediated activation of caspase-8. Moreover, sensitization to Fas-mediated apoptosis was also induced in Fas-resistant osteosarcoma cells by suppressing FLIP expression using FLIP-specific RNA interference. HDAC inhibitors including FR901228 were shown to induce downregulation of cellular FLIP through inhibiting generation of FLIP mRNA, rather than stimulating degradation at either protein or mRNA level, and the inhibition was independent of de novo protein synthesis. These results clearly indicate that some tumor cells exhibit a phenotype resistant to death receptor-mediated apoptosis by expressing cellular FLIP, and that HDAC inhibitors sensitize such resistant tumor cells by directly downregulating cellular FLIP mRNA.
authors.affiliation: Graduate School of Biostudies and Institute for Virus Research, Kyoto University, Kyoto, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.forename: K
authors.initials: K
authors.lastname: Okamoto
authors.forename: S
authors.initials: S
authors.lastname: Yonehara
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D045744:Cell Line, Tumor; D047630:Depsipeptides / Q000494:pharmacology; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology; D014176:Protein Biosynthesis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D019014:fas Receptor / Q000502:physiology*
chemical_list: D000903:Antibiotics, Antineoplastic; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D047630:Depsipeptides; D056572:Histone Deacetylase Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019014:fas Receptor; C087123:romidepsin