title: Vorinostat and sorafenib increase ER stress, autophagy and apoptosis via ceramide-dependent CD95 and PERK activation.
abstract: We recently noted that low doses of sorafenib and vorinostat interact in a synergistic fashion to kill carcinoma cells by activating CD95, and this drug combination is entering phase I trials. The present studies mechanistically extended our initial observations. Low doses of sorafenib and vorinostat, but not the individual agents, caused an acidic sphingomyelinase and fumonisin B1-dependent increase in CD95 surface levels and CD95 association with caspase 8. Knock down of CD95 or FADD expression reduced sorafenib/vorinostat lethality. Signaling by CD95 caused PERK activation that was responsible for both promoting caspase 8 association with CD95 and for increased eIF2alpha phosphorylation; suppression of eIF2alpha function abolished drug combination lethality. Cell killing was paralleled by PERK-and eIF2alpha-dependent lowering of c-FLIP-s protein levels and overexpression of c-FLIP-s maintained cell viability. In a CD95-, FADD- and PERK-dependent fashion, sorafenib and vorinostat increased expression of ATG5 that was responsible for enhanced autophagy. Expression of PDGFRbeta and FLT3 were essential for high dose single agent sorafenib treatment to promote autophagy. Suppression of PERK function reduced sorafenib and vorinostat lethality whereas suppression of ATG5 levels elevated sorafenib and vorinostat lethality. Overexpression of c-FLIP-s blocked apoptosis and enhanced drug-induced autophagy. Thus sorafenib and vorinostat promote ceramide-dependent CD95 activation followed by induction of multiple downstream survival regulatory signals: ceramide-CD95-PERK-FADD-pro-caspase 8 (death); ceramide-CD95-PERK-eIF2alpha- downward arrowc-FLIP-s (death); ceramide-CD95-PERK-ATG5-autophagy (survival).
authors.affiliation: Department of Biochemistry, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Park
authors.forename: Guo
authors.initials: G
authors.lastname: Zhang
authors.forename: Aditi Pandya
authors.initials: AP
authors.lastname: Martin
authors.forename: Hossein
authors.initials: H
authors.lastname: Hamed
authors.forename: Clint
authors.initials: C
authors.lastname: Mitchell
authors.forename: Philip B
authors.initials: PB
authors.lastname: Hylemon
authors.forename: Martin
authors.initials: M
authors.lastname: Graf
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Kevin
authors.initials: K
authors.lastname: Ryan
authors.forename: Xiang
authors.initials: X
authors.lastname: Liu
authors.forename: Sarah
authors.initials: S
authors.lastname: Spiegel
authors.forename: James
authors.initials: J
authors.lastname: Norris
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fisher
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001343:Autophagy; D001557:Benzenesulfonates / Q000494:pharmacology*; D053181:Caspase 8 / Q000378:metabolism; D002470:Cell Survival; D002518:Ceramides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D008954:Models, Biological; D009154:Mutation; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D011725:Pyridines / Q000494:pharmacology*; D000077157:Sorafenib; D016896:Treatment Outcome; D000077337:Vorinostat; D019892:eIF-2 Kinase / Q000096:biosynthesis*; D019014:fas Receptor / Q000096:biosynthesis*
chemical_list: D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D053181:Caspase 8; D002518:Ceramides; D015852:Eukaryotic Initiation Factor-2; D006877:Hydroxamic Acids; D009536:Niacinamide; D010671:Phenylurea Compounds; D011725:Pyridines; D000077157:Sorafenib; D000077337:Vorinostat; D019892:eIF-2 Kinase; D019014:fas Receptor
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