title: Characterisation of telomerase immortalised normal human oesophageal squamous cells.
abstract: OBJECTIVE
  Oesophageal cell lines derived from malignancies have numerous genetic abnormalities and therefore are of limited value for studying the early events in carcinogenesis. Reported attempts to establish normal human oesophageal cell lines either have failed to achieve immortalisation or have achieved it by disrupting important cell functions. We have used telomerase technology to establish normal human oesophageal cell lines.
  
  
  METHODS
  Endoscopic biopsy specimens of normal oesophageal squamous epithelium were trypsinised, dispersed into single cell suspensions, and cocultivated with ATCC Swiss 3T3 cells. Oesophageal cells were infected with the catalytic subunit of human telomerase (hTERT) using a defective retroviral vector. The integrity of cell cycle checkpoints was tested by measuring p53 response to UV irradiation, and p16 response to infection with H-RasGV12. Expression of a differentiation marker was tested by measuring involucrin response to calcium exposure.
  
  
  RESULTS
  Cultures of uninfected oesophageal cells had weak telomerase activity at baseline but exhibited loss of telomerase activity and progressive telomere shortening before undergoing senescence between population doublings (PD) 40-45. In contrast, hTERT infected cells exhibited sustained telomerase activity and stabilisation of telomere length. These cells have reached PD 100 with no diminution in growth rate, while cell cycle checkpoint integrity and involucrin response to calcium exposure have remained intact.
  
  
  CONCLUSIONS
  By introducing telomerase into normal human oesophageal squamous cells cocultivated with feeder layers, we have established a cell line that retains normal cell cycle checkpoints and normal differentiation markers. This cell line may be useful for studying the early events in oesophageal carcinogenesis.
authors.affiliation: Department of Veterans Affairs Medical Center, Dallas, Texas, USA. cpmoral@swbell.net
authors.forename: C P
authors.initials: CP
authors.lastname: Morales
authors.forename: K G
authors.initials: KG
authors.lastname: Gandia
authors.forename: R D
authors.initials: RD
authors.lastname: Ramirez
authors.forename: W E
authors.initials: WE
authors.lastname: Wright
authors.forename: J W
authors.initials: JW
authors.lastname: Shay
authors.forename: S J
authors.initials: SJ
authors.lastname: Spechler
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002453:Cell Cycle; D002460:Cell Line / Q000166:cytology* / Q000201:enzymology; D018920:Coculture Techniques; D004847:Epithelial Cells / Q000166:cytology* / Q000201:enzymology; D004947:Esophagus / Q000166:cytology*; D005822:Genetic Vectors; D006801:Humans; D015603:Keratinocytes / Q000166:cytology; D007633:Keratins / Q000378:metabolism; D051379:Mice; D011498:Protein Precursors / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D014161:Transduction, Genetic
chemical_list: D011498:Protein Precursors; C032253:involucrin; D007633:Keratins; D019098:Telomerase; D002118:Calcium