title: p53-dependent DNA damage-induced apoptosis requires Fas/APO-1-independent activation of CPP32beta.
abstract: In many cell types, the p53 tumor suppressor protein is required for the induction of apoptosis by DNA-damaging chemotherapy or radiation. Therefore, identification of the molecular determinants of p53-dependent cell death may aid in the design of effective therapies of p53-deficient cancers. We investigated whether p53-dependent apoptosis requires activation of CPP32beta (caspase 3), a cysteine protease that has been found to mediate apoptosis in response to ligation of the Fas molecule or to granzyme B, a component of CTL lytic granules. Irradiation-induced apoptosis was associated with p53-dependent activation of CPP32beta-related proteolysis, and normal thymocytes were protected from irradiation by Acetyl-Asp-Glu-Val-Asp-CHO (Ac-DEVD-CHO), a specific inhibitor of CPP32beta. We next examined whether the Fas system is required for p53-dependent apoptosis and whether stimuli that induce activation of CPP32beta induce apoptosis in p53-deficient cells. Thymocytes or activated T cells from Fas-deficient mice were resistant to apoptosis induced by ligation of Fas or CD3, respectively, but remained normally susceptible to irradiation. Thymocytes from p53-deficient mice, although resistant to DNA damage, remained sensitive to CPP32beta-mediated apoptosis induced by ligation of Fas or CD3, or by exposure to cytotoxic T cells. These results demonstrate that DNA damage-induced apoptosis of T cells requires p53-mediated activation of CPP32beta by a mechanism independent of Fas/FasL interactions and suggest that immunological or molecular methods of activating CPP32beta may be effective at inducing apoptosis in p53-deficient cancers that are resistant to conventional chemotherapy or irradiation.
authors.affiliation: Johns Hopkins Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Fuchs
authors.forename: K A
authors.initials: KA
authors.lastname: McKenna
authors.forename: A
authors.initials: A
authors.lastname: Bedi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004249:DNA Damage / Q000528:radiation effects; D004792:Enzyme Precursors / Q000502:physiology; D053804:Granzymes; D051379:Mice; D018345:Mice, Knockout; D012697:Serine Endopeptidases / Q000502:physiology; D013601:T-Lymphocytes / Q000502:physiology; D013950:Thymus Gland / Q000166:cytology / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000502:physiology*; D019014:fas Receptor / Q000502:physiology*
chemical_list: D004792:Enzyme Precursors; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases