Bryostatin 1 and UCN-01 potentiate 1-beta-D-arabinofuranosylcytosine-induced apoptosis in human myeloid leukemia cells through disparate mechanisms.
The effects of the PKC activator and down-regulator bryostatin 1 and the PKC and Chk1 inhibitor 7-hydroxystaurosporine (UCN-01) were compared with respect to potentiation of 1-beta-D-arabinofuranosylcytosine (ara-C)-induced apoptosis in human myelomonocytic leukemia cells (U937). Whereas bryostatin 1 and UCN-01 both markedly enhanced ara-C-induced mitochondrial injury (e.g., cytochrome c and Smac/DIABLO release, loss of mitochondrial membrane potential), caspase activation, and apoptosis, ectopic expression of an N-terminal loop-deleted Bcl-2 mutant protein protected cells from ara-C/UCN-01- but not ara-C/bryostatin 1-mediated lethality. Conversely, ectopic expression of CrmA or dominant-negative caspase-8 abrogated potentiation of ara-C-mediated apoptosis by bryostatin 1 but not by UCN-01. Exposure of cells to ara-C and bryostatin 1 (but not UCN-01) resulted in sustained release of tumor necrosis factor (TNF) alpha; moreover, potentiation of ara-C lethality by bryostatin 1 (but not by UCN-01) was reversed by coadministration of TNF soluble receptors or the selective PKC inhibitor bisindolylmaleimide (1 microM). Finally, similar events were observed in the human promyelocytic leukemia cell line HL-60. Together, these findings suggest that potentiation of ara-C lethality in human myeloid leukemia cells by bryostatin 1 but not UCN-01 involves activation of the extrinsic, receptor-mediated apoptotic pathway, and represents a consequence of bryostatin 1-mediated release of TNF-alpha. They also argue that the mechanism by which bryostatin 1 promotes ara-C-induced mitochondrial injury, caspase activation, and apoptosis involves factors other than or in addition to PKC down-regulation or modulation of Bcl-2 phosphorylation status.
Wang
Shujie
S
Division of Hematology/Oncology, Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
Wang
Zhiliang
Z
Grant
Steven
S
D000470:Alkaloids / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D054713:Bryostatins; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D003561:Cytarabine / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D017353:Gene Deletion; D018922:HL-60 Cells; D006801:Humans; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D007783:Lactones / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000473:pathology*; D018942:Macrolides; D008301:Maleimides; D024101:Mitochondrial Proteins / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D019311:Staurosporine / Q000031:analogs & derivatives; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D020298:U937 Cells
D000470:Alkaloids; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D054713:Bryostatins; D002352:Carrier Proteins; D003574:Cytochrome c Group; C412403:DIABLO protein, human; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D007783:Lactones; D018942:Macrolides; D008301:Maleimides; D024101:Mitochondrial Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D003561:Cytarabine; C046785:bryostatin 1; C054852:7-hydroxystaurosporine; D011493:Protein Kinase C; D020169:Caspases; D019311:Staurosporine; C070515:bisindolylmaleimide I