title: Subtelomeric demethylation deregulated hTERT expression, telomerase activity, and telomere length in four nasopharyngeal carcinoma cell lines.
abstract: Global DNA hypomethylation, in particular that of the gene promoter sequence in gene hypermethylation, is a well-known characteristic of human cancer. Subtelomeres are enriched CpG islands; methylation is believed to be a potential epigenetic regulator. However, regulation on the telomere length remains largely unknown. To demonstrate this correlation, four nasopharyngeal carcinoma cell lines (CNE, CNE1, CNE2, 5-8F) were treated for 72 hours with 0, 1, or 2.5 μM of the demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC). Subtelomeric (D4Z4) level methylation was evaluated with a bisulfite assay, the human telomerase catalytic subunit (hTERT) expression was assayed by reverse transcription-polymerase chain reaction, the telomerase activity was detected using a telomeric repeat amplification protocol assay, and the telomere length was measured by Southern blot terminal restriction fragment analysis. There was significant demethylation following 5-aza-dC treatment, and a strongly repressed hTERT expression decreased the telomerase activity and remarkably shortened telomeres. Thus, partial subtelomeric methylation does not repress hTERT expression; conversely, demethylation may downregulate hTERT expression and shorten telomeres.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Renmin Hospital of Wuhan University , Wuhan, People's Republic of China .
authors.forename: Zi-Xiong
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Ze-Zhang
authors.initials: ZZ
authors.lastname: Tao
authors.forename: Shi-Ming
authors.initials: SM
authors.lastname: Chen
authors.forename: Bo-Kui
authors.initials: BK
authors.lastname: Xiao
authors.forename: Tao
authors.initials: T
authors.lastname: Zhou
mesh_terms: D002277:Carcinoma; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D006801:Humans; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D019098:Telomerase / Q000235:genetics*; D016615:Telomere / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; C509186:TERT protein, human; D019098:Telomerase
keywords: 5-aza-dC; DNA methylation; hTERT; telomerase; telomere length