title: Bcl-2 antagonists interact synergistically with bortezomib in DLBCL cells in association with JNK activation and induction of ER stress.
abstract: Mechanisms underlying interactions between the proteasome inhibitor bortezomib and small molecule Bcl-2 antagonists were examined in GC- and ABC-type human DLBCL (diffuse lymphocytic B-cell lymphoma) cells. Concomitant or sequential exposure to non- or minimally toxic concentrations of bortezomib or other proteasome inhibitors and either HA14-1 or gossypol resulted in a striking increase in Bax/Bak conformational change/translocation, cytochrome c release, caspase activation and synergistic induction of apoptosis in both GC- and ABC-type cells. These events were associated with a sharp increase in activation of the stress kinase JNK and evidence of ER stress induction (e.g., eIF2alpha phosphorylation, activation of caspases-2 and -4, and Grp78 upregulation). Pharmacologic or genetic (e.g., shRNA knockdown) interruption of JNK signaling attenuated HA14-1/bortezomib lethality and ER stress induction. Genetic disruption of the ER stress pathway (e.g., in cells expressing caspase-4 shRNA or DN-eIF2alpha) significantly attenuated lethality. The toxicity of this regimen was independent of ROS generation. Finally, HA14-1 significantly increased bortezomib-mediated JNK activation, ER stress induction, and lethality in bortezomib-resistant cells. Collectively these findings indicate that small molecule Bcl-2 antagonists promote bortezomib-mediated mitochondrial injury and lethality in DLBCL cells in association with enhanced JNK activation and ER stress induction. They also raise the possibility that such a strategy may be effective in different DLBCL sub-types (e.g., GC- or ABC), and in bortezomib-resistant disease.
authors.affiliation: Department of Medicine, Massey Cancer Center, Virginia Commonwealth University Health Systems, Richmond, VA 23298, USA.
authors.forename: Girija
authors.initials: G
authors.lastname: Dasmahapatra
authors.forename: Dmitry
authors.initials: D
authors.lastname: Lembersky
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Lora
authors.initials: L
authors.lastname: Kramer
authors.forename: Jonathan
authors.initials: J
authors.lastname: Friedberg
authors.forename: Richard I
authors.initials: RI
authors.lastname: Fisher
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001578:Benzopyrans / Q000008:administration & dosage / Q000494:pharmacology*; D001897:Boronic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D009570:Nitriles / Q000008:administration & dosage / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology*; D015398:Signal Transduction
chemical_list: D001578:Benzopyrans; D001897:Boronic Acids; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; C000717247:HSPA5 protein, human; D009570:Nitriles; D011480:Protease Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; C456800:ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate; D000069286:Bortezomib; D048031:JNK Mitogen-Activated Protein Kinases