title: BCL-2 family inhibitors enhance histone deacetylase inhibitor and sorafenib lethality via autophagy and overcome blockade of the extrinsic pathway to facilitate killing.
abstract: We examined whether the multikinase inhibitor sorafenib and histone deacetylase inhibitors (HDACI) interact to kill pancreatic carcinoma cells and determined the impact of inhibiting BCL-2 family function on sorafenib and HDACI lethality. The lethality of sorafenib was enhanced in pancreatic tumor cells in a synergistic fashion by pharmacologically achievable concentrations of the HDACIs vorinostat or sodium valproate. Overexpression of cellular FLICE-like inhibitory protein (c-FLIP-s) or knockdown of CD95 suppressed the lethality of the sorafenib/HDACI combination (sorafenib + HDACI). In immunohistochemical analyses or using expression of fluorescence-tagged proteins, treatment with sorafenib and vorinostat together (sorafenib + vorinostat) promoted colocalization of CD95 with caspase 8 and CD95 association with the endoplasmic reticulum markers calnexin, ATG5, and Grp78/BiP. In cells lacking CD95 expression or in cells expressing c-FLIP-s, the lethality of sorafenib + HDACI exposure was abolished and was restored when cells were coexposed to BCL-2 family inhibitors [ethyl [2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)]-4H-chromene-3-carboxylate (HA14-1), obatoclax (GX15-070)]. Knockdown of BCL-2, BCL-XL, and MCL-1 recapitulated the effects of GX15-070 treatment. Knockdown of BAX and BAK modestly reduced sorafenib + HDACI lethality but abolished the effects of GX15-070 treatment. Sorafenib + HDACI exposure generated a CD95- and Beclin1-dependent protective form of autophagy, whereas GX15-070 treatment generated a Beclin1-dependent toxic form of autophagy. The potentiation of sorafenib + HDACI killing by GX15-070 was suppressed by knockdown of Beclin1 or of BAX + BAK. Our data demonstrate that pancreatic tumor cells are susceptible to sorafenib + HDACI lethality and that in tumor cells unable to signal death from CD95, use of a BCL-2 family antagonist facilitates sorafenib + HDACI killing via autophagy and the intrinsic pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
authors.forename: Aditi Pandya
authors.initials: AP
authors.lastname: Martin
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Park
authors.forename: Clint
authors.initials: C
authors.lastname: Mitchell
authors.forename: Teneille
authors.initials: T
authors.lastname: Walker
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Andrew
authors.initials: A
authors.lastname: Thorburn
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
authors.forename: Roland
authors.initials: R
authors.lastname: Reinehr
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects*; D001557:Benzenesulfonates / Q000494:pharmacology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000378:metabolism*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D007150:Immunohistochemistry; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D000077157:Sorafenib; D014162:Transfection; D019014:fas Receptor / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C000717247:HSPA5 protein, human; D056572:Histone Deacetylase Inhibitors; D010671:Phenylurea Compounds; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D034741:RNA, Small Interfering; D019014:fas Receptor; D009536:Niacinamide; D000077157:Sorafenib