title: Selective inhibition of apoptosis by TPA-induced differentiation of U937 leukemic cells.
abstract: U937 leukemic cells treated for 24 h with 16 nM 12-O-tetradecanoylphorbol 13-acetate (TPA), that induces their macrophagic terminal differentiation, become resistant to etoposide-induced apoptosis. Exposure of undifferentiated U937 cells to 50 microM etoposide for 6 h, that triggers apoptosis in 80% cells, activates procaspase-2L, -3 and -8, induces the mitochondrial release of cytochrome c and decreases Mcl-1 expression without modifying Bcl-2, Bcl-xL and Bax protein levels. All these events are inhibited in TPA-differentiated U937 cells that are also resistant to vinblastine-induced and Fas-mediated cell death. Interestingly, these cells are not inherently resistant to apoptosis induction. Exposure of TPA-differentiated U937 cells to 0.8 microg/ml cycloheximide for 24 h, that triggers apoptosis in 50% cells, activates procaspase-2L, -3 and -8, induces the mitochondrial release of cytochrome c and decreases Bcl-xL expression without modifying Bcl-2, Mcl-1 and Bax protein levels. All these events are not observed in undifferentiated cells treated in similar conditions. These results indicate that the apoptotic pathway that involves the release of cytochrome c from mitochondria and the cleavage of procaspases remains functional in TPA-differentiated cells.
authors.affiliation: Department of Biology and Therapy of Cancer, INSERM U517, JE 515, Faculty of Medicine & Pharmacy, 7, boulevard Jeanne d'Arc, 21033 Dijon, France.
authors.forename: O
authors.initials: O
authors.lastname: Sordet
authors.forename: A
authors.initials: A
authors.lastname: Bettaieb
authors.forename: J M
authors.initials: JM
authors.lastname: Bruey
authors.forename: B
authors.initials: B
authors.lastname: Eymin
authors.forename: N
authors.initials: N
authors.lastname: Droin
authors.forename: M
authors.initials: M
authors.lastname: Ivarsson
authors.forename: C
authors.initials: C
authors.lastname: Garrido
authors.forename: E
authors.initials: E
authors.lastname: Solary
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002273:Carcinogens / Q000494:pharmacology*; D053143:Caspase 2; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004792:Enzyme Precursors / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D053222:Fas Ligand Protein; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D020298:U937 Cells; D014747:Vinblastine / Q000494:pharmacology; D051020:bcl-X Protein
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C494811:BCL2L1 protein, human; D002273:Carcinogens; D003574:Cytochrome c Group; D004792:Enzyme Precursors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D011500:Protein Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D014747:Vinblastine; D005047:Etoposide; D003513:Cycloheximide; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053143:Caspase 2; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D013755:Tetradecanoylphorbol Acetate