title: Genetic determinants that influence hypoxia-induced apoptosis.
abstract: The p53 tumour suppressor gene is capable of activating both death receptor and mitochondrial-signalled forms of apoptotic cell death in response to diverse stimuli. Studies have suggested that impairment of the mitochondrial-signalled Apaf/caspase 9 pathway and not the death receptor Fas pathway results in almost complete resistance to apoptotic cell death induced by a low oxygen environment. However, it is unclear how p53 signals the activation of this pathway and whether it is through already identified p53 effector genes such as the pro-apoptotic gene bax, or through novel effectors such as BNIP-3/BNIP-3L. Comparison of cell lines genetically matched at the bax, cytochrome c, apaf, caspase 9 and caspase 3 loci indicated that except for bax, all of these genes were essential for hypoxia induced apoptosis both in cell culture and in transplanted tumours. These data imply that cytochrome c plays a pivotal role in signalling cell death by apoptosis under hypoxic conditions, and that the release of cytochrome c is independent of both Bax and p53. In contrast to cytochrome c, p53 modulates the magnitude of apoptosis under hypoxic conditions, but in itself is not required for the activation of the caspase cascade.
authors.affiliation: Stanford University School of Medicine, Department of Radiation Oncology, Division of Radiation & Cancer Biology, CA 94305-5152, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Alarcon
authors.forename: N C
authors.initials: NC
authors.lastname: Denko
authors.forename: A J
authors.initials: AJ
authors.lastname: Giaccia
mesh_terms: D000332:Aerobiosis; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D002460:Cell Line; D003574:Cytochrome c Group / Q000378:metabolism; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology*; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
chemical_list: C494827:Bax protein, mouse; D003574:Cytochrome c Group; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; C506434:Casp9 protein, mouse; D053453:Caspase 9; D020169:Caspases