1. P21Waf1/Cip1 dysfunction in neuroblastoma: a novel mechanism of attenuating G0-G1 cell cycle arrest.
- Author
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McKenzie PP, Danks MK, Kriwacki RW, and Harris LC
- Subjects
- Child, Cyclin-Dependent Kinase 2, Cyclin-Dependent Kinase 4, Cyclin-Dependent Kinase Inhibitor p21, Cyclin-Dependent Kinases metabolism, Cyclins genetics, G1 Phase, Genetic Vectors, Humans, Protein Serine-Threonine Kinases metabolism, Recombinant Proteins metabolism, Resting Phase, Cell Cycle, Transfection, CDC2-CDC28 Kinases, Cell Cycle physiology, Cyclins metabolism, Neuroblastoma pathology, Proto-Oncogene Proteins
- Abstract
In normal cells in which DNA has been damaged, p53 induces the expression of p21(Waf1/Cip1); p21, in turn, binds to cyclin-dependent kinase 2 (cdk2) and inhibits its function. Inhibition of cdk2 results in cell cycle arrest in G(0)-G(1). Although p53 is transcriptionally active and induces p21 expression in neuroblastoma (NB) cells, the G(0)-G(1) checkpoint is attenuated. Here we report that the mechanism that mediates this defect in NB cells is the inability of p21 to bind to, or inhibit the activity of cdk2. However, when recombinant p21 protein was added to NB cell extracts in vitro, the protein inhibited the activity of cdk2. This finding suggests that endogenous p21 protein in NB cells is inactive and may be bound either to a protein complex or in a conformation that precludes its binding to cdk2. The dysfunction of p21 in NB cells represents a novel mechanism by which the G(0)-G(1) cell cycle checkpoint can be inactivated. This mechanism may be important in regulating the growth of NB and potentially other types of tumors. Cdk inhibitors currently being developed for clinical use may be useful therapy for tumors such as NB in which endogenous cdk inhibitors are defective.
- Published
- 2003