title: Sorafenib and vorinostat kill colon cancer cells by CD95-dependent and -independent mechanisms.
abstract: We examined the interaction between the multikinase inhibitor sorafenib and histone deacetylase inhibitors. Sorafenib and vorinostat synergized (sorafenib + vorinostat) to kill HCT116 and SW480 cells. In SW480 cells, sorafenib + vorinostat increased CD95 plasma membrane levels and promoted death-inducing signal complex (DISC) formation, and drug toxicity was blocked by knockdown of CD95 or overexpression of cellular FLICE-like inhibitory protein (c-FLIP-s). In SW620 cells that are patient-matched to SW480 cells, sorafenib + vorinostat toxicity was significantly lower, which correlated with a lack of CD95 activation and lower expression of ceramide synthase 6 (LASS6). Overexpression of LASS6 in SW620 cells enhanced drug-induced CD95 activation and enhanced tumor cell killing, whereas knockdown of LASS6 in SW480 cells suppressed CD95 activation. Knocking down LASS6 expression also suppressed CD95 activation in hepatoma, pancreatic, and ovarian cancer cells. In HCT116 cells, sorafenib + vorinostat treatment caused DISC formation without reducing c-FLIP-s expression and did not increase CD95 plasma membrane levels; sorafenib + vorinostat exposure killed HCT116 cells via an intrinsic pathway/caspase 9-dependent mechanism. In HCT116 cells, knockdown of CD95 enhanced sorafenib + vorinostat lethality, which correlated with less drug-induced CD95-dependent autophagy. Sorafenib + vorinostat treatment activated the c-Jun NH(2)-terminal kinase pathway, which was causal in promoting dissociation of Beclin1 from BCL-2, and in promoting autophagy. Knockdown of Beclin1 expression blocked autophagy and enhanced drug toxicity. Our data demonstrate that treatment of colon cancer cells with sorafenib + vorinostat activates CD95 via de novo ceramide synthesis that promotes viability via autophagy or degrades survival via either the extrinsic or intrinsic pathways.
authors.affiliation: Department of Biochemistry and Molecular Biology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
authors.forename: Teneille
authors.initials: T
authors.lastname: Walker
authors.forename: Clint
authors.initials: C
authors.lastname: Mitchell
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Park
authors.forename: Adly
authors.initials: A
authors.lastname: Yacoub
authors.forename: Martin
authors.initials: M
authors.lastname: Graf
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Houghton
authors.forename: Christina
authors.initials: C
authors.lastname: Voelkel-Johnson
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000633:toxicity*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D001557:Benzenesulfonates / Q000633:toxicity*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D045325:HCT116 Cells; D006801:Humans; D006877:Hydroxamic Acids / Q000633:toxicity*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives; D010088:Oxidoreductases / Q000378:metabolism; D010671:Phenylurea Compounds; D011725:Pyridines / Q000633:toxicity*; D000077157:Sorafenib; D000077337:Vorinostat
chemical_list: D015703:Antigens, CD; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D001557:Benzenesulfonates; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D006877:Hydroxamic Acids; D008565:Membrane Proteins; D010671:Phenylurea Compounds; D011725:Pyridines; D009536:Niacinamide; D000077337:Vorinostat; D000077157:Sorafenib; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D048031:JNK Mitogen-Activated Protein Kinases; D053453:Caspase 9