title: The proteasome inhibitor bortezomib interacts synergistically with histone deacetylase inhibitors to induce apoptosis in Bcr/Abl+ cells sensitive and resistant to STI571.
abstract: Interactions between the proteasome inhibitor bortezomib and histone deacetylase inhibitors (HDIs) have been examined in Bcr/Abl+ human leukemia cells (K562 and LAMA 84). Coexposure of cells (24-48 hours) to minimally toxic concentrations of bortezomib + either suberoylanilide hydroxamic acid (SAHA) or sodium butyrate (SB) resulted in a striking increase in mitochondrial injury, caspase activation, and apoptosis, reflected by caspases-3 and -8 cleavage and poly(adenosine diphosphate-ribose) polymerase (PARP) degradation. These events were accompanied by down-regulation of the Raf-1/mitogen-induced extracellular kinase (MEK)/extracellular signal-related kinase (ERK) pathway as well as diminished expression of Bcr/Abl and cyclin D1, cleavage of p21CIP1 and phosphorylation of the retinoblastoma protein (pRb), and induction of the stress-related kinases Jun kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Transient transfection of cells with a constitutively active MEK construct significantly protected them from bortezomib/SAHA-mediated lethality. Coadministration of bortezomib and SAHA resulted in increased reactive oxygen species (ROS) generation and diminished nuclear factor kappa B (NF-kappa B) activation; moreover, the free radical scavenger L-N-acetylcyteine (LNAC) blocked bortezomib/SAHA-related ROS generation, induction of JNK and p21CIP1, and apoptosis. Lastly, this regimen potently induced apoptosis in STI571 (imatinib mesylate)-resistant K562 cells and CD34+ mononuclear cells obtained from a patient with STI571-resistant disease, as well as in Bcr/Abl- leukemia cells (eg, HL-60, U937, Jurkat). Together, these findings raise the possibility that combined proteasome/histone deacetylase inhibition may represent a novel strategy in leukemia, including apoptosis-resistant Bcr/Abl+ hematologic malignancies.
authors.affiliation: Department of Medicine, Virginia Commonweatlth University, Medical College of Virginia, Richmond VA, 23298, USA.
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yu
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Daniel
authors.initials: D
authors.lastname: Conrad
authors.forename: Mark
authors.initials: M
authors.lastname: Subler
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002087:Butyrates / Q000494:pharmacology; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016044:Fusion Proteins, bcr-abl; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000473:pathology*; D010879:Piperazines / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology; D011719:Pyrazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D000077337:Vorinostat
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D001897:Boronic Acids; D002087:Butyrates; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D010879:Piperazines; D011480:Protease Inhibitors; D011719:Pyrazines; D011743:Pyrimidines; D017382:Reactive Oxygen Species; D000077337:Vorinostat; D000069286:Bortezomib; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl