title: Induction of apoptosis by bleomycin in p53-null HL-60 leukemia cells.
abstract: The role of p53 in apoptosis and the contrasting p53 status in tumors prompted us to investigate the bleomycin-induced apoptosis in p53-null human leukemia HL-60 cells (bleomycin at 160 microM for 7.5 h). Cells with apoptotic phenotype increased from 0.87% in controls to 9.40% in bleomycin-treated cells. Both the enzymes, caspase-3 and -8, were activated. Furthermore, the apoptotic phenotypes totally disappeared with zVAD-fmk, a caspase inhibitor. Besides, cytochrome c release from mitochondria happened simultaneously to apoptotic phenotypes, shrinkage of mitochondria but being independent of the mitochondrial permeability transition, since cyclosporine A and bongkrekic acid were inefficient on induced apoptosis. On the other hand, incubations with bleomycin (BLM) did not result in detectable changes in the expression of Bcl-2- and Bax-mRNA neither Bcl-2- or Bax-proteins. In conclusion, we suggest that BLM can produce apoptosis independently of p53 through three mechanisms: i) at the nuclear level by its endonuclease activities; ii) at the cell membrane, by activating caspases; and iii) at the mitochondria by releasing cytochrome c. These results indicate that BLM-induced apoptosis in HL-60 cells results from the activation of a mitochondria-dependent caspase cascade which includes also the activation of the initiator caspase-8.
authors.affiliation: Secteur Prevention, Institut Jean Godinot, BP 171, 51 056 Reims Cedex, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Gimonet
authors.forename: Emilie
authors.initials: E
authors.lastname: Landais
authors.forename: Helene
authors.initials: H
authors.lastname: Bobichon
authors.forename: Paul
authors.initials: P
authors.lastname: Coninx
authors.forename: Françoise
authors.initials: F
authors.lastname: Liautaud-Roger
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D001761:Bleomycin / Q000494:pharmacology*; D015153:Blotting, Western; D001865:Bongkrekic Acid / Q000494:pharmacology; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D016158:Genes, p53; D018922:HL-60 Cells; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000473:pathology*; D008854:Microscopy, Electron; D008928:Mitochondria / Q000473:pathology; D010641:Phenotype; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000964:Antimetabolites, Antineoplastic; C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D001761:Bleomycin; D001865:Bongkrekic Acid; D012313:RNA; D016572:Cyclosporine; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases