1. Inhibitors of cyclin-dependent kinases induce features of replicative senescence in early passage human diploid fibroblasts.
- Author
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McConnell BB, Starborg M, Brookes S, and Peters G
- Subjects
- Animals, Cells, Cultured, Cellular Senescence physiology, Cyclin-Dependent Kinase Inhibitor p15, Cyclin-Dependent Kinase Inhibitor p16 metabolism, Cyclin-Dependent Kinase Inhibitor p21, Cyclin-Dependent Kinase Inhibitor p27, Cyclins metabolism, Enzyme Inhibitors administration & dosage, Fluorescent Antibody Technique, Humans, Microtubule-Associated Proteins metabolism, Phenotype, RNA, Time Factors, Transcription Factors metabolism, Cell Cycle Proteins, Cyclin-Dependent Kinases antagonists & inhibitors, Fibroblasts physiology, Tumor Suppressor Proteins
- Abstract
After a limited number of population doublings (PDs), cultures of normal mammalian diploid cells undergo an irreversible growth arrest known as replicative senescence [1]. As well as contributing to cellular ageing, senescence is viewed as an important mechanism of tumour suppression by preventing the emergence of immortal cell clones [2-4]. Senescent cells have a number of characteristics that distinguish them from cycling or quiescent cells including elevated levels of two cyclin-dependent kinase (Cdk) inhibitors, p16INK4a and p21CIP1 [5-11]. Here, we demonstrate that both of these Cdk inhibitors, as well as other members of their protein families (the INK4 and CIP/KIP families, respectively [12]), induce several facets of the senescent phenotype when ectopically expressed in young human diploid fibroblasts. These include a reduced proliferative capacity, an altered size and shape, the presence of underphosphorylated retinoblastoma protein (pRb), increased expression of plasminogen activator inhibitor (PAI-1) and the appearance of senescence-associated beta-galactosidase (SA-beta-gal) activity [2,3,13-15]. A 20 amino acid peptide from p16INK4a that inhibits Cdks active in the G1 phase of the cell cycle [16] produces similar effects in a dose-dependent manner suggesting that, in primary fibroblasts, inhibition of G1-specific Cdk activity is sufficient to induce phenotypic changes that normally occur at the end of their finite lifespan.
- Published
- 1998
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