title: Role of NF-kappaB activity in apoptotic response of keratinocytes mediated by interferon-gamma, tumor necrosis factor-alpha, and tumor-necrosis-factor-related apoptosis-inducing ligand.
abstract: An important step in tumorigenesis involves loss of sensitivity to various apoptotic signals by malignant cells, imbuing them with an enhanced survival phenotype. NF-kappaB also regulates epidermal thickness, susceptibility to apoptosis, and tumor formation in skin. Keratinocytes were examined for their susceptibility to apoptosis using cytokines produced during an immunologic response to tumor antigens, i.e., interferon-gamma and/or tumor necrosis factor-alpha (TNF-alpha). The role for NF-kappaB in this response was examined using a retroviral vector containing a degradation-resistant form of IkappaBalpha. Whereas interferon-gamma and TNF-alpha either alone or in combination did not induce apoptosis in keratinocytes, after infection with the retrovirus to block NF-kappaB activation they became susceptible to TNF-alpha but not Fas-induced apoptosis. Moreover, when keratinocytes with repressed NF-kappaB activity were simultaneously treated with interferon-gamma, there was a synergistic induction of apoptosis by TNF-alpha that was dependent on FADD, tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL), and caspase activation. Molecular abnormalities accompanying repressed NF-kappaB activity included failure to induce TNF-RII receptor together with enhanced levels of TRAIL death receptor 4. The ability of interferon-gamma when combined with TNF-alpha to mediate keratinocyte apoptosis included induction of TRAIL coupled with diminished capacity of keratinocytes with repressed NF-kappaB activity to increase the TRAIL decoy receptor-1, as well as lower levels of several NF-kappaB-dependent antiapoptotic proteins accompanied by enhanced caspase 8 levels. These results indicate that interferon-gamma and TNF-alpha synergistically induce keratinocyte apoptosis when concomitant induction of NF-kappaB is blocked. Participants in the apoptotic response mediated by NF-kappaB, besides cell-survival proteins, include modulation of TRAIL and both death and decoy receptors. Thus, not only does NF-kappaB signaling influence the intrinsic survival pathway for keratinocytes in normal skin, but it may also play a role in determining the apoptotic response to cytokines generated during an immune response via TRAIL produced by the keratinocytes themselves.
authors.affiliation: Department of Pathology, Skin Cancer Research Program, Loyola University Medical Center, Loyola University of Chicago, Chicago, Illinois, USA.
authors.forename: J Z
authors.initials: JZ
authors.lastname: Qin
authors.forename: P
authors.initials: P
authors.lastname: Bacon
authors.forename: V
authors.initials: V
authors.lastname: Chaturvedi
authors.forename: B J
authors.initials: BJ
authors.lastname: Nickoloff
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004338:Drug Combinations; D053200:Fas-Associated Death Domain Protein; D005799:Genes, Dominant; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D015603:Keratinocytes / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology* / Q000502:physiology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D004338:Drug Combinations; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D020672:I-kappa B Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma