title: Correlation between radiation-induced telomerase activity and human telomerase reverse transcriptase mRNA expression in HeLa cells.
abstract: OBJECTIVE
  To quantify and correlate human telomerase reverse transcriptase (hTERT) mRNA expression with telomerase activity (TA) after ionizing irradiation of HeLa cells.
  
  
  METHODS
  TA and hTERT mRNA expression were evaluated, at 24-h intervals, in HeLa cells cultured for up to 144 h, before and after treatment with increasing doses of 6 MV photon ionizing radiation (5 - 20 Gy), using the telomeric repeat amplification protocol (TRAP) assay and real-time reverse transcriptase polymerase chain reaction (RT-PCR), respectively. Cell viability was determined using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. A prototype phantom was constructed for accurate irradiation of HeLa cells.
  
  
  RESULTS
  Treated cells showed a decrease in viability with increasing radiation dose, and a correlation was observed with post-treatment period. TA and hTERT mRNA expression of HeLa cells increased for the first 24 h after irradiation. The maximal increases were approximately two times the un-irradiated cell levels at 24 h post-irradiation, followed by a decrease and a return to the control levels 72 h post-irradiation. The time-course of telomerase activation after 24 h, differed among radiation doses. A dose-dependent G2/M arrest was observed 24 h post-irradiation, along with an increase in polyploidy 48 h post-irradiation and afterwards.
  
  
  CONCLUSIONS
  A correlation between TA and hTERT mRNA expression and a radiation induced cell cycle dependent modification of hTERT mRNA expression was established for the first 24 h post-irradiation.
authors.affiliation: Department of Biology, University of Thessaly, Medical School, Larissa, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Satra
authors.forename: Ioannis
authors.initials: I
authors.lastname: Tsougos
authors.forename: Vassilios
authors.initials: V
authors.lastname: Papanikolaou
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Theodorou
authors.forename: Constantine
authors.initials: C
authors.lastname: Kappas
authors.forename: Aspasia
authors.initials: A
authors.lastname: Tsezou
mesh_terms: D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology / Q000528:radiation effects*; D006367:HeLa Cells / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D007118:Immunoassay; D012333:RNA, Messenger / Q000378:metabolism / Q000528:radiation effects*; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D013778:Tetrazolium Salts / Q000032:analysis / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D013778:Tetrazolium Salts; D019098:Telomerase