Telomerase suppression by chromosome 6 in a human papillomavirus type 16-immortalized keratinocyte cell line and in a cervical cancer cell line

J Natl Cancer Inst. 2001 Jun 6;93(11):865-72. doi: 10.1093/jnci/93.11.865.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Division
  • Cell Line, Transformed
  • Chromosomes, Human, Pair 11
  • Chromosomes, Human, Pair 6*
  • DNA-Binding Proteins
  • Female
  • Genes, Reporter
  • Humans
  • Hybrid Cells
  • Keratinocytes
  • Microsatellite Repeats
  • Papillomaviridae / genetics*
  • Polymerase Chain Reaction
  • RNA*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Telomerase / antagonists & inhibitors
  • Telomerase / metabolism*
  • Telomere / genetics
  • Telomere / ultrastructure
  • Transfection
  • Tumor Cells, Cultured
  • Uterine Cervical Neoplasms / genetics*
  • beta-Galactosidase / genetics

Substances

  • DNA-Binding Proteins
  • telomerase RNA
  • RNA
  • Telomerase
  • beta-Galactosidase