title: Pathways involved in proliferating, senescent and immortalized keratinocyte cell death mediated by two different TRAIL preparations.
abstract: Properly regulated keratinocyte cell death is fundamentally important to maintain structural integrity and homeostatic function of epidermis. Moreover, from an oncological perspective, therapeutic approaches selectively targeting apoptosis of malignant cell types while sparing normal keratinocytes in surrounding skin is desirable. Apo2Ligand/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) has been observed to preferentially induce cytopathic effects on transformed/malignant cell types compared with their non-neoplastic counterparts. In this report, two different biologically active preparations of Apo2L/TRAIL, a non-tagged version, NT-Apo2L/TRAIL, and a leucine zipper fusion protein, LZ-Apo2L/TRAIL, were examined for their ability to trigger apoptosis in normal human keratinocytes, and in an immortalized cell line (HaCaT cells). Differences between these preparations were observed, including: NT-Apo2L/TRAIL induced less keratinocyte apoptosis compared with LZ-Apo2L/TRAIL; NT-Apo2L/TRAIL also induced less apoptosis of HaCaT cells compared with LZ-Apo2L/TRAIL; LZ-Apo2L/TRAIL but not NT-Apo2L/TRAIL induced cytotoxic effects when keratinocytes became growth arrested due to undergoing spontaneous replicative senescence--a biological state previously observed to be resistant to UV-light-induced apoptosis. Similarities between preparations included: an enhanced ability for both Apo2L/TRAIL preparations to kill a greater relative percentage of HaCaT cells compared with keratinocytes; enhanced cytotoxicity towards keratinocytes that had their NF-B activity inhibited; a dependence of both Apo2L/TRAIL preparations on FADD and caspase activation; triggering of the same caspase cascades including caspase 8 and 3; and an ability to induce apoptosis even when HaCaT cells and keratinocytes were transduced to overexpress either Bcl-2 or Bcl-x(L) (survival factors that reduce susceptibility to UV-light-induced apoptosis). These results indicate that while both preparations of Apo2L/TRAIL possess biological activity, there are important differences as regards their ability to induce apoptosis in normal and immortalized keratinocytes. Moreover, the death receptor pathway triggered by LZ-Apo2L/TRAIL can overcome the apoptotic resistance normally observed in response to UV-light mediated by Bcl-2/Bcl-x(L), as well as by the state of cellular senescence. Unraveling the molecular basis for these differential biological effects may reveal a new strategic role for these death receptor/ligands linked to apoptosis in maintaining the dynamic balance of keratinocyte proliferation, differentiation, and cell death necessary to achieve a homeostatic thickness and function of normal skin. In addition, it may be possible to utilize these Apo2L/TRAIL preparations for the treatment of various sun-induced skin cancers as they can differentially trigger apoptosis of transformed keratinocytes, or keratinocytes with abnormal NF-kappaB signaling, while sparing adjacent normal keratinocytes.
authors.affiliation: Loyola University Medical Center, Skin Cancer Research Laboratory, Cardinal Bernardin Cancer Center, Maywood, IL 60153, USA. bnickol@lumc.edu
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Qin
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Bacon
authors.forename: Vijaya
authors.initials: V
authors.lastname: Chaturvedi
authors.forename: Brian
authors.initials: B
authors.lastname: Bonish
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Nickoloff
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D002455:Cell Division; D002461:Cell Line, Transformed / Q000187:drug effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D016328:NF-kappa B / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000502:physiology; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051020:bcl-X Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; C448905:LZ-TRAIL protein, recombinant; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D011493:Protein Kinase C; D020169:Caspases