title: Ectopic expression of Bcl-2 and Bcl-xL inhibits apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL) through suppression of caspases-8, 7, and 3 and BID cleavage in human acute myelogenous leukemia cell line HL-60.
abstract: Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is one of the latest members of the TNF superfamily known to induce apoptosis in a wide variety of tumor cells. Some cell types, however, are quite resistant to TRAIL. We investigated the effect of ectopic expression of Bcl-2 and Bcl-xL on TRAIL-induced apoptosis in human acute myelogenous leukemia HL-60 cells. We found that HL-60 cells, which express TRAIL receptors (also called death receptor, DR) DR4, DR5, and Dc (decoy) R2, are highly sensitive to TRAIL-induced cytotoxicity. Greater than 90% killing occurred within 24 h of TRAIL treatment. The expression of Bcl-2 and Bcl-xL, however, completely abolished the TRAIL-induced cytotoxic effects. Treatment of HL-60 cells with TRAIL induced caspase-8 activation within 2-4 h, but no activation could be seen in Bcl-2-expressing or Bcl-xL-expressing cells. TRAIL also induced cleavage of BID, which was also abolished by Bcl-2 and Bcl-xL. Similarly, TRAIL activated caspase-3 and caspase-7 in control cells but not in cells expressing Bcl-2 or Bcl-xL. Cleavage of the caspase-3 substrate poly(ADP-ribose) polymerase (PARP), was abrogated by ectopic expression of Bcl-2 and Bcl-xL. Inhibition of caspases by the pan-caspase inhibitor, benzyloxycarbonyl-valine-alanine-aspartate-fluoromethylketone (zVAD-fmk) abolished the TRAIL-induced apoptosis. Overall, these results indicate that TRAIL-induced apoptosis involves activation of caspase-8, caspase-7, caspase-3, and BID cleavage, and Bcl-2 and Bcl-xL prevents TRAIL-induced apoptosis by abrogating caspase activation and BID cleavage.
authors.affiliation: Cytokine Research Section, Department of Bioimmunotherapy, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030-4009, USA.
authors.forename: Betty
authors.initials: B
authors.lastname: Lamothe
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D053148:Caspase 3; D053179:Caspase 7; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D002470:Cell Survival / Q000276:immunology; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000494:pharmacology; D051020:bcl-X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053179:Caspase 7; D053181:Caspase 8; D053453:Caspase 9