title: A novel paradigm for rapid ABT-737-induced apoptosis involving outer mitochondrial membrane rupture in primary leukemia and lymphoma cells.
abstract: Primary chronic lymphocytic leukemia (CLL) cells are exquisitely sensitive to ABT-737, a small molecule BCL2-antagonist, which induces many of the classical biochemical and ultrastructural features of apoptosis, including BAX/BAK oligomerization, cytochrome c release, caspase activation and chromatin condensation. Surprisingly, ABT-737 also induces mitochondrial inner membrane permeabilization (MIMP) resulting in mitochondrial matrix swelling and rupture of the outer mitochondrial membrane (OMM), so permitting the rapid efflux of cytochrome c from mitochondrial cristae and facilitating rapid caspase activation and apoptosis. BAX and BAK appear to be involved in the OMM discontinuities as they localize to the OMM break points. Notably, ABT-737 induced mitochondrial matrix swelling and OMM discontinuities in other primary B-cell malignancies, including mantle cell, follicular and marginal zone lymphoma cells but not in several cell lines studied. Thus, we describe a new paradigm of apoptosis in primary B-cell malignancies, whereby targeting of BCL2 results in all the classical features of apoptosis together with OMM rupture independent of caspase activation. This mechanism may be far more prevalent than hitherto recognized due to the failure of most methods, used to measure apoptosis, to recognize such a mechanism.
authors.affiliation: MRC Toxicology Unit, University of Leicester, Leicester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Vogler
authors.forename: D
authors.initials: D
authors.lastname: Dinsdale
authors.forename: X-M
authors.initials: XM
authors.lastname: Sun
authors.forename: K W
authors.initials: KW
authors.lastname: Young
authors.forename: M
authors.initials: M
authors.lastname: Butterworth
authors.forename: P
authors.initials: P
authors.lastname: Nicotera
authors.forename: M J S
authors.initials: MJ
authors.lastname: Dyer
authors.forename: G M
authors.initials: GM
authors.lastname: Cohen
mesh_terms: D000328:Adult; D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001713:Biphenyl Compounds / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism* / Q000473:pathology; D051336:Mitochondrial Membranes / Q000187:drug effects* / Q000648:ultrastructure; D009596:Nitrophenols / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors; D013449:Sulfonamides / Q000494:pharmacology*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C501332:ABT-737; D000590:Amino Acid Chloromethyl Ketones; D001713:Biphenyl Compounds; D015853:Cysteine Proteinase Inhibitors; D009596:Nitrophenols; D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone