title: Telomerase suppression by chromosome 6 in a human papillomavirus type 16-immortalized keratinocyte cell line and in a cervical cancer cell line.
abstract: BACKGROUND
  High-risk human papillomavirus (HPV) types play a major role in the development of cervical cancer in vivo and can induce immortalization of primary human keratinocytes in vitro. Activation of the telomere-lengthening enzyme telomerase constitutes a key event in both processes. Because losses of alleles from chromosome 6 and increased telomerase activity have been observed in high-grade premalignant cervical lesions, we analyzed whether human chromosome 6 harbors a putative telomerase repressor locus that may be involved in HPV-mediated immortalization.
  
  
  METHODS
  Microcell-mediated chromosome transfer was used to introduce chromosomes 6 and 11 to the in vitro generated HPV type 16 (HPV16)-immortalized keratinocyte cell line FK16A and to the in vivo derived HPV16-containing cervical cancer cell line SIHA: Hybrid clones were analyzed for growth characteristics, telomerase activity, human telomerase reverse transcriptase (hTERT) and HPV16 E6 expression, and telomere length. FK16A hybrid clones were also transduced with an hTERT-containing retrovirus to examine the effect of ectopic hTERT expression on growth. Statistical tests were two-sided.
  
  
  RESULTS
  Introduction of human chromosome 6 but not of chromosome 11 to both cell lines yielded hybrid cells that demonstrated crisis-like features (i.e., enlarged and flattened morphology, vacuolation, and multinucleation) and underwent growth arrest after a marked lag period. In the chromosome 6 hybrid clones analyzed, telomerase activity and hTERT messenger RNA (mRNA) expression were statistically significantly reduced compared with those in the chromosome 11 hybrid clones (for telomerase activity, P =.004 for the FK16A hybrids and P =.039 for the SiHa hybrids; for hTERT mRNA expression, P =.003 for the FK16A hybrids). The observed growth arrest was associated with telomeric shortening. Ectopic expression of hTERT in FK16A cells could prevent the telomeric shortening-based growth arrest induced by chromosome 6.
  
  
  CONCLUSIONS
  Chromosome 6 may harbor a repressor of hTERT transcription, the loss of which may be involved in HPV-mediated immortalization.
authors.affiliation: Department of Pathology, Unit of Molecular Pathology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: R D
authors.initials: RD
authors.lastname: Steenbergen
authors.forename: D
authors.initials: D
authors.lastname: Kramer
authors.forename: C J
authors.initials: CJ
authors.lastname: Meijer
authors.forename: J M
authors.initials: JM
authors.lastname: Walboomers
authors.forename: D A
authors.initials: DA
authors.lastname: Trott
authors.forename: A P
authors.initials: AP
authors.lastname: Cuthbert
authors.forename: R F
authors.initials: RF
authors.lastname: Newbold
authors.forename: W J
authors.initials: WJ
authors.lastname: Overkamp
authors.forename: M Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: P J
authors.initials: PJ
authors.lastname: Snijders
mesh_terms: D002455:Cell Division; D002461:Cell Line, Transformed; D002880:Chromosomes, Human, Pair 11; D002896:Chromosomes, Human, Pair 6; D004268:DNA-Binding Proteins; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D006822:Hybrid Cells; D015603:Keratinocytes; D018895:Microsatellite Repeats; D027383:Papillomaviridae / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012313:RNA; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000648:ultrastructure; D014162:Transfection; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase; D001616:beta-Galactosidase