title: Novel mechanisms of apoptosis induced by histone deacetylase inhibitors.
abstract: Histone deacetylase inhibitors (HDACIs) are a new class of chemotherapeutic drugs able to induce tumor cell apoptosis and/or cell cycle arrest; however, the molecular mechanisms underpinning their anticancer effects are poorly understood. Herein, we assessed the apoptotic pathways activated by three HDACIs, suberoylanilide hydroxamic acid, oxamflatin, and depsipeptide. We determined that all three drugs induced the accumulation of cells with a 4n DNA content and apoptosis mediated by the intrinsic apoptotic pathway. HDACI-induced mitochondrial membrane damage and apoptosis were inhibited by overexpression of Bcl-2, but not by the polycaspase inhibitor N-tert-butoxy-carbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk). Moreover, induction of a G(1)-S checkpoint through overexpression of p16(INK4A) or suppression of de novo protein synthesis also inhibited HDACI-induced cell death. Proteolytic cleavage of caspase-2, which is poorly inhibited by zVAD-fmk, was concomitant with HDACI-induced death; however, full processing of caspase-2 to the p19 active form was blocked by Bcl-2. Whereas all three drugs induce the activation of the proapoptotic Bcl-2 protein Bid upstream of mitochondrial membrane disruption, Bid cleavage in response to depsipeptide was significantly attenuated by zVAD-fmk. Suberoylanilide hydroxamic acid and oxamflatin could kill both P-glycoprotein (P-gp)(+) MDR cells and their P-gp(-) counterparts, whereas depsipeptide was shown to be a substrate for P-gp and was less effective in killing P-gp(+) cells. These data provide insight into the functional profile of three HDACIs and are important for the development of more rational approaches to chemotherapy, where information regarding the genetic profile of the tumor is matched with the functional profile of a given chemotherapeutic drug to promote favorable clinical responses.
authors.affiliation: Cancer Immunology Program, The Peter MacCallum Cancer Institute, East Melbourne 3002, Victoria, Australia.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Peart
authors.forename: Kellie M
authors.initials: KM
authors.lastname: Tainton
authors.forename: Astrid A
authors.initials: AA
authors.lastname: Ruefli
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Dear
authors.forename: Karin A
authors.initials: KA
authors.lastname: Sedelies
authors.forename: Lorraine A
authors.initials: LA
authors.lastname: O'Reilly
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Waterhouse
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Trapani
authors.forename: Ricky W
authors.initials: RW
authors.lastname: Johnstone
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D061945:Caspase Inhibitors; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D019938:Cyclin D1 / Q000096:biosynthesis / Q000502:physiology; D003574:Cytochrome c Group / Q000378:metabolism; D047630:Depsipeptides; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D010456:Peptides, Cyclic / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000077337:Vorinostat
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D047630:Depsipeptides; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D010456:Peptides, Cyclic; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C100692:oxamflatin; D019938:Cyclin D1; D000077337:Vorinostat; C087123:romidepsin