Potent inhibitors of cyclin-dependent kinase 2 induce nuclear accumulation of wild-type p53 and nucleolar fragmentation in human untransformed and tumor-derived cells.
The cdk2 gene has been identified as a human cdc2/CDC28-related gene that encodes a protein kinase essential for the G1/S transition in mammalian cells, but not for the G2/M transition, which requires Cdk1, another p34cdc2/CDC28 homolog. Novel potential functions of Cdk2 have been uncovered by using two potent and specific inhibitors of its kinase activity, roscovitine and olomoucine, on human wt p53-expresser untransformed and tumor-derived cells. At concentrations equal or superior to respectively 30- and 20-fold their in vitro IC50 values for cyclin B/Cdk1, cyclin A/Cdk2 and cyclin E/Cdk2, the Cdk inhibitors precipitately induce a dramatic nuclear accumulation of wt p53 and a delocalization of nucleolin from the nucleolus in all interphase cells, whatever their cell cycle status, acting in this way like the DNA-damaging drug, mitomycin C (7 microg/ml). These early events are soon followed by a nucleolar fragmentation in both normal and tumor cells in the presence of the Cdk inhibitors but not in the presence of the DNA-damaging drug. Yet, treatment with either type of compounds eventually triggers rapidly the death of the tumor cells and, much more slowly, that of the normal cells. The Cdk inhibitors, however, stimulate cell death from any stage of the cell cycle, whereas the DNA-damaging drug kills more efficaciously S phase cells. These observations provide a hint that the Cdk2 kinase might be involved in controlling the nuclear levels of the tumor suppressor wt p53 protein and in maintaining the nucleolar integrity and function, linking in this way the cell division cycle machinery to survival functions and overall cell metabolism via the control of nucleocytoplasmic transport and of ribosome production.
David-Pfeuty
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UMR 146 du CNRS, Institut Curie-Recherche, Bâtiment 110, Centre Universitaire, 91405 Orsay Cédex, France.
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology; D042846:CDC2-CDC28 Kinases; D002277:Carcinoma / Q000188:drug therapy / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line / Q000187:drug effects; D002461:Cell Line, Transformed; D002466:Cell Nucleolus / Q000235:genetics; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D007701:Kinetin; D016685:Mitomycin / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011687:Purines / Q000494:pharmacology; D016601:RNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D000077546:Roscovitine; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000378:metabolism*; D000097796:Nucleolin
D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D004791:Enzyme Inhibitors; D007701:Kinetin; D016685:Mitomycin; D019384:Nucleic Acid Synthesis Inhibitors; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011687:Purines; D016601:RNA-Binding Proteins; D000077546:Roscovitine; D016159:Tumor Suppressor Protein p53; D000097796:Nucleolin; C090046:olomoucine; C495894:CDK2 protein, human