title: Intracellular regulation of TRAIL-induced apoptosis in human melanoma cells.
abstract: The observation that TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF cytokine family, induces apoptosis in a number of different tumor cell types led us to compare the tumoricidal effects of TRAIL to those of other TNF family molecules on human melanoma cells. We found that a high proportion of the melanoma cell lines tested were killed by TRAIL, whereas all the melanoma lines were resistant to the other TNF family cytokines tested. TRAIL-induced death was characterized by caspase activation and cellular protein cleavage within minutes of TRAIL addition, and death could be completely inhibited by the caspase inhibitors Ile-Glu-Thr-Asp (IETD) and Val-Ala-Asp (VAD), indicating the presence of a TRAIL receptor signaling pathway similar to that identified for Fas and TNF receptors. Specific TRAIL receptor expression was determined by RT-PCR, and the presence of mRNA encoding the "protective" TRAIL receptors did not correspond to resistance or sensitivity to TRAIL-induced apoptosis. Addition of protein synthesis inhibitors to TRAIL-resistant melanomas rendered them sensitive to TRAIL, indicating that the presence or the absence of intracellular apoptosis inhibitors may mediate resistance or sensitivity to TRAIL-mediated apoptosis. Expression of one such inhibitor, FLICE-inhibitory protein (FLIP), was highest in the TRAIL-resistant melanomas, while being low or undetectable in the TRAIL-sensitive melanomas. Furthermore, addition of actinomycin D to TRAIL-resistant melanomas resulted in decreased intracellular concentrations of FLIP, which correlated with their acquisition of TRAIL sensitivity. Collectively, our results indicate that TRAIL-induced apoptosis occurs through a caspase signaling cascade and that resistance is controlled by intracellular regulators of apoptosis.
authors.affiliation: Department of Immunobiology, Immunex Corp., Seattle, WA 98101, USA. tgriffith@immunex.com
authors.forename: T S
authors.initials: TS
authors.lastname: Griffith
authors.forename: W A
authors.initials: WA
authors.lastname: Chin
authors.forename: G C
authors.initials: GC
authors.lastname: Jackson
authors.forename: D H
authors.initials: DH
authors.lastname: Lynch
authors.forename: M Z
authors.initials: MZ
authors.lastname: Kubin
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D007424:Intracellular Fluid / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008545:Melanoma / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis; D053221:TNF-Related Apoptosis-Inducing Ligand; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D011500:Protein Synthesis Inhibitors; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D003546:Cysteine Endopeptidases