title: Common telomerase reverse transcriptase promoter mutations in hepatocellular carcinomas from different geographical locations.
abstract: OBJECTIVE
  To determine the mutation status of human telomerase reverse transcriptase gene (TERT) promoter region in hepatocellular carcinoma (HCC) from different geographical regions.
  
  
  METHODS
  We analyzed the genomic DNA sequences of 59 HCC samples comprising 15 cell lines and 44 primary tumors, collected from patients living in Asia, Europe and Africa. We amplified a 474 bp DNA fragment of the promoter region of TERT gene including the 1295228 and 1295250 sequence of chromosome 5 by using PCR. Amplicons were then sequenced by Sanger technique and the sequence data were analyzed with by using DNADynamo software in comparison with wild type TERT gene sequence as a reference.
  
  
  RESULTS
  The TERT mutations were found highly frequent in HCC. Eight of the fifteen tested cell lines displayed C228T mutation, and one had C250T mutation with a mutation frequency up to 60%. All of the mutations were heterozygous and mutually exclusive. Ten out of forty-four tumors displayed C228T mutation, and additional five tumors had C250T mutation providing evidence for mutation frequency of 34% in primary tumors. Considering the geographic origins of HCC tumors tested, TERT promoter mutation frequencies were higher in African (53%), when compared to non-African (24%) tumors (P = 0.056). There was also a weak inverse correlation between TERT promoter mutations and murine double minute 2 single nucleotide polymorphism 309 TG polymorphism (P = 0.058). Mutation frequency was nearly two times higher in established HCC cell lines (60%) compared to the primary tumors (34%).
  
  
  CONCLUSIONS
  TERT promoter is one of most frequent mutational targets in liver cancer, and hepatocellular carcinogenesis is highly associated with the loss of telomere-dependent cellular senescence control.
authors.affiliation: Dilek Cevik, Gokhan Yildiz, Mehmet Ozturk, BilGen Genetics and Biotechnology Center, Department of Molecular Biology and Genetics, Bilkent University, Ankara 06800, Turkey.
authors.forename: Dilek
authors.initials: D
authors.lastname: Cevik
authors.affiliation: Dilek Cevik, Gokhan Yildiz, Mehmet Ozturk, BilGen Genetics and Biotechnology Center, Department of Molecular Biology and Genetics, Bilkent University, Ankara 06800, Turkey.
authors.forename: Gokhan
authors.initials: G
authors.lastname: Yildiz
authors.affiliation: Dilek Cevik, Gokhan Yildiz, Mehmet Ozturk, BilGen Genetics and Biotechnology Center, Department of Molecular Biology and Genetics, Bilkent University, Ankara 06800, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Ozturk
mesh_terms: D000349:Africa / Q000453:epidemiology; D001208:Asia / Q000453:epidemiology; D014408:Biomarkers, Tumor / Q000235:genetics*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000453:epidemiology / Q000235:genetics*; D004252:DNA Mutational Analysis; D005060:Europe / Q000453:epidemiology; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D056945:Hep G2 Cells; D006579:Heterozygote; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000453:epidemiology / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics; D019098:Telomerase / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; C509186:TERT protein, human; D019098:Telomerase
keywords: Cellular immortality; Hepatocellular carcinoma; Liver cancer; Promoter mutation; Telomerase reverse transcriptase; Telomerase reverse transcriptase gene