title: Sensitization to TRAIL-induced apoptosis and modulation of FLICE-inhibitory protein in B chronic lymphocytic leukemia by actinomycin D.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent activator of the cell death pathway and exerts tumoricidal activity in vivo with minimal toxicity. In order to investigate the therapeutic potential of TRAIL in B chronic lymphocytic leukemia (B-CLL) we have analyzed the expression of TRAIL receptors (TRAIL-Rs) in leukemic cells from B-CLL patients and their in vitro sensitivity to apoptosis induced by recombinant human TRAIL. We have found TRAIL-R1 and -R2 death receptor, and TRAIL-R3 and -R4 decoy receptor mRNA expression in most of the 57 B-CLL patients studied (R1 82%, R2 100%, R3 96% and R4 82%). TRAIL-R1 and R2 proteins were expressed on the surface and within the cells, whereas R3 and R4 decoy receptors were almost exclusively expressed in the cytoplasm. Despite TRAIL death receptor expression, B-CLL cells were relatively resistant to induction of apoptosis by recombinant human TRAIL (300 ng/ml). However, the susceptibility to TRAIL-induced apoptosis was increased by treatment of B-CLL cells with actinomycin D (Act D). Western blot analysis showed higher constitutive expression of the long form of FLICE-inhibitory protein (FLIP(L)) in B-CLL as compared to normal tonsillar B cells. Act D treatment down-regulated both long and short FLIP expression, which was correlated with the increase in B-CLL sensitivity to TRAIL. Although the surface TRAIL death receptor expression was up-regulated both by cell culture and by Act D treatment, the changes were not correlated with a gain in susceptibility to TRAIL. In addition, neither decoy receptors nor Bcl-2 expression were affected by Act D. Our findings suggest the possible involvement of FLIP in regulating TRAIL-mediated apoptosis in B-CLL.
authors.affiliation: Microbiology and Tumor Biology Center, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Olsson
authors.forename: T
authors.initials: T
authors.lastname: Diaz
authors.forename: M
authors.initials: M
authors.lastname: Aguilar-Santelises
authors.forename: A
authors.initials: A
authors.lastname: Osterborg
authors.forename: F
authors.initials: F
authors.lastname: Celsing
authors.forename: M
authors.initials: M
authors.lastname: Jondal
authors.forename: L M
authors.initials: LM
authors.lastname: Osorio
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000187:drug effects*; D003609:Dactinomycin / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D058851:GPI-Linked Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000494:pharmacology*; D008875:Middle Aged; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D053221:TNF-Related Apoptosis-Inducing Ligand; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D058851:GPI-Linked Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C108661:TNFRSF10C protein, human; C505653:TNFSF10 protein, human; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin