title: Spontaneous immortalization of human epidermal cells with naturally elevated telomerase.
abstract: This work explores spontaneous immortalization in keratinocytes, derived from two skin samples, that display naturally elevated telomerase activity. Serially passaged with 3T3 feeder layer support, the keratinocytes were examined for colony-forming ability, telomerase activity, telomere length, and finally gene expression using Affymetrix DNA microarrays. The cells initially exhibited normal karyotypes and low colony-forming efficiencies typical of normal epidermal cells, but after 40 passages (approximately 400 generations) colony-forming ability increased markedly, yielding immortalized lines exhibiting a small number of chromosomal aberrations and functionally normal p53. An improved protocol for analysis of microarray data permitted detection of 707 transcriptional changes accompanying immortalization including reduced p16(INK4A) mRNA. Telomerase activity was clearly elevated in cells even at low passage from both samples, and telomerase catalytic subunit mRNA was greatly elevated in those with elevated colony-forming ability. The data raise the possibility of an unusual natural phenotype in which aberrant telomerase regulation extends keratinocyte lifespan until rare variants evade senescence. In addition to revealing a potential tumor-prone syndrome, the findings emphasize the desirability of carefully minimizing the degree or timing of elevated expression of telomerase used to immortalize cells for therapeutic purposes.
authors.affiliation: Department of Environmental Toxicology, University of California, Davis, California 95616-8588, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Rea
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Qin
authors.initials: Q
authors.lastname: Qin
authors.forename: Yann
authors.initials: Y
authors.lastname: Barrandon
authors.forename: Karen W
authors.initials: KW
authors.lastname: Easley
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Gungner
authors.forename: Marjorie A
authors.initials: MA
authors.lastname: Phillips
authors.forename: William S
authors.initials: WS
authors.lastname: Holland
authors.forename: Paul H
authors.initials: PH
authors.lastname: Gumerlock
authors.forename: David M
authors.initials: DM
authors.lastname: Rocke
authors.forename: Robert H
authors.initials: RH
authors.lastname: Rice
mesh_terms: D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics*; D002869:Chromosome Aberrations; D002877:Chromosomes, Human / Q000235:genetics; D000078404:Epidermal Cells; D004817:Epidermis / Q000201:enzymology*; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015603:Keratinocytes / Q000201:enzymology*; D020411:Oligonucleotide Array Sequence Analysis; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D019098:Telomerase