title: INK4a-deficient human diploid fibroblasts are resistant to RAS-induced senescence.
abstract: The CDKN2A tumour suppressor locus encodes two distinct proteins, p16(INK4a) and p14(ARF), both of which have been implicated in replicative senescence, the state of permanent growth arrest provoked in somatic cells by aberrant proliferative signals or by cumulative population doublings in culture. Here we describe primary fibroblasts from a member of a melanoma-prone family who is homozygous for an intragenic deletion in CDKN2A. Analyses of the resultant gene products imply that the cells are p16(INK4a) deficient but express physiologically relevant levels of a frameshift protein that retains the known functions of p14(ARF). Although they have a finite lifespan, the cells are resistant to arrest by oncogenic RAS. Indeed, ectopic expression of RAS and telomerase (hTERT) results in outgrowth of anchorage-independent colonies that have essentially diploid karyotypes and functional p53. We find that in human fibroblasts, ARF is not induced demonstrably by RAS, pointing to significant differences between the proliferative barriers implemented by the CDKN2A locus in different cell types or species.
authors.affiliation: Molecular Oncology and Human Cytogenetics Laboratories, Cancer Research UK London Research Institute, Lincolns Inn Fields, London WC2A 3PX, UK.
authors.forename: Sharon
authors.initials: S
authors.lastname: Brookes
authors.forename: Janice
authors.initials: J
authors.lastname: Rowe
authors.forename: Margarida
authors.initials: M
authors.lastname: Ruas
authors.forename: Susana
authors.initials: S
authors.lastname: Llanos
authors.forename: Paula A
authors.initials: PA
authors.lastname: Clark
authors.forename: Martine
authors.initials: M
authors.lastname: Lomax
authors.forename: Marion C
authors.initials: MC
authors.lastname: James
authors.forename: Radost
authors.initials: R
authors.lastname: Vatcheva
authors.forename: Stewart
authors.initials: S
authors.lastname: Bates
authors.forename: Karen H
authors.initials: KH
authors.lastname: Vousden
authors.forename: David
authors.initials: D
authors.lastname: Parry
authors.forename: Nelleke
authors.initials: N
authors.lastname: Gruis
authors.forename: Nico
authors.initials: N
authors.lastname: Smit
authors.forename: Wilma
authors.initials: W
authors.lastname: Bergman
authors.forename: Gordon
authors.initials: G
authors.lastname: Peters
mesh_terms: D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D002648:Child; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects; D017353:Gene Deletion; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D019098:Telomerase; D018631:ras Proteins