title: Reversal of human cellular senescence: roles of the p53 and p16 pathways.
abstract: Telomere erosion and subsequent dysfunction limits the proliferation of normal human cells by a process termed replicative senescence. Replicative senescence is thought to suppress tumorigenesis by establishing an essentially irreversible growth arrest that requires activities of the p53 and pRB tumor suppressor proteins. We show that, depending on expression of the pRB regulator p16, replicative senescence is not necessarily irreversible. We used lentiviruses to express specific viral and cellular proteins in senescent human fibroblasts and mammary epithelial cells. Expression of telomerase did not reverse the senescence arrest. However, cells with low levels of p16 at senescence resumed robust growth upon p53 inactivation, and limited growth upon expression of oncogenic RAS. In contrast, cells with high levels of p16 at senescence failed to proliferate upon p53 inactivation or RAS expression, although they re-entered the cell cycle without growth after pRB inactivation. Our results indicate that the senescence response to telomere dysfunction is reversible and is maintained primarily by p53. However, p16 provides a dominant second barrier to the unlimited growth of human cells.
authors.affiliation: Lawrence Berkeley National Laboratory, MS 84-171, 1 Cyclotron Road, Berkeley, CA 94720, USA.
authors.forename: Christian M
authors.initials: CM
authors.lastname: Beauséjour
authors.forename: Ana
authors.initials: A
authors.lastname: Krtolica
authors.forename: Francesco
authors.initials: F
authors.lastname: Galimi
authors.forename: Masashi
authors.initials: M
authors.lastname: Narita
authors.forename: Scott W
authors.initials: SW
authors.lastname: Lowe
authors.forename: Paul
authors.initials: P
authors.lastname: Yaswen
authors.forename: Judith
authors.initials: J
authors.lastname: Campisi
mesh_terms: D001940:Breast / Q000166:cytology; D002460:Cell Line; D016922:Cellular Senescence / Q000502:physiology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism / Q000821:virology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000821:virology; D011905:Genes, ras; D049452:Green Fluorescent Proteins; D006801:Humans; D016180:Lentivirus Infections / Q000821:virology; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D015398:Signal Transduction; D019098:Telomerase / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D008164:Luminescent Proteins; D016159:Tumor Suppressor Protein p53; D049452:Green Fluorescent Proteins; D019098:Telomerase