BCL-2 family inhibitors enhance histone deacetylase inhibitor and sorafenib lethality via autophagy and overcome blockade of the extrinsic pathway to facilitate killing.
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.
Martin
Aditi Pandya
AP
Department of Biochemistry and Molecular Biology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0035, USA.
Park
Margaret A
MA
Mitchell
Clint
C
Walker
Teneille
T
Rahmani
Mohamed
M
Thorburn
Andrew
A
Häussinger
Dieter
D
Reinehr
Roland
R
Grant
Steven
S
Dent
Paul
P
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
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