title: Selective loss of CDC2 and CDK2 induction by tumor necrosis factor-alpha in senescent human diploid fibroblasts.
abstract: Normal human diploid fibroblasts undergo a finite number of doublings in culture. This process of senescence is accompanied by a loss in the ability to respond to proliferative stimuli and is therefore distinct from the quiescent state induced by nutrient deprivation. We have studied changes in gene expression induced in these cells following exposure to the cytokine, tumor necrosis factor-alpha (TNF). We observed that TNF induced CDC2 and CDK2 expression in early-passage quiescent WI-38 fibroblasts. However, as cells approached senescence, their ability to induce CDC2 and CDK2, as well as stimulate DNA synthesis in response to TNF, progressively declined, with minimal to absent induction in senescent cells. This occurred despite the TNF-dependent induction of such proliferation-independent genes as manganese superoxide dismutase and interleukin-6 in senescent and quiescent cells. Serum was similarly unable to induce CDC2 or CDK2 expression in senescent cells. These results demonstrate that senescent cells are selectively deficient in TNF-mediated induction of CDC2 and CDK2, genes crucial to DNA synthesis and mitosis.
authors.affiliation: Department of Medicine, Stanford University School of Medicine, California 94305.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsuji
authors.forename: J
authors.initials: J
authors.lastname: Ninomiya-Tsuji
authors.forename: S V
authors.initials: SV
authors.lastname: Torti
authors.forename: F M
authors.initials: FM
authors.lastname: Torti
mesh_terms: D016203:CDC2 Protein Kinase / Q000096:biosynthesis* / Q000235:genetics; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D016922:Cellular Senescence; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004790:Enzyme Induction / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics; D011494:Protein Kinases / Q000096:biosynthesis* / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D015850:Interleukin-6; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D013482:Superoxide Dismutase; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases