title: Reversible conversion of immortal human cells from telomerase-positive to telomerase-negative cells.
abstract: Immortal cell lines and tumors maintain their telomeres via the telomerase pathway or via a telomerase-independent pathway, referred to as alternative lengthening of telomeres (ALT). Here, we show the reversible conversion of the human papillomavirus type 16 E6-induced immortal human fibroblasts E6 Cl 6 from telomerase-positive (Tel(+)) to telomerase-negative (Tel(-)) cells. Tel(+) cells converted spontaneously to Tel(-) cells that reverted to Tel(+) cells following treatment with trichostatin A (TSA) and/or 5-aza-2'-deoxycytidine (5-AZC), which induced the reversion from complete to partial methylation of the CpG islands of the human telomerase reverse transcriptase (hTERT) promoter in Tel(-) E6 Cl 6 cells. Tel(-) E6 Cl 6 cells lacked the phenotypes characteristic of ALT cell lines such as very long and heterogenous telomeres and ALT-associated promyelocytic leukemia nuclear bodies (APB) but grew for >240 population doublings (PD) after they became telomerase negative. The ratios of histone H3 (H3) lysine (K) 9 methylation to each of H3-K4 methylation, H3-K9 acetylation, and H3-K14 acetylation of the chromatin containing the hTERT promoter in Tel(-) E6 Cl 6 cells and ALT cell lines were greater than those in Tel(+) cells and decreased following treatment with TSA and/or 5-AZC, inversely corresponding to telomerase activity. Our findings suggest the possibility that human tumors may be able to reversibly interconvert their telomere maintenance phenotypes by chromatin structure-mediated regulation of hTERT expression.
authors.affiliation: Department of Pharmacology, Nippon Dental University, School of Dentistry at Tokyo, Tokyo, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Kumakura
authors.forename: Takeo W
authors.initials: TW
authors.lastname: Tsutsui
authors.forename: Junko
authors.initials: J
authors.lastname: Yagisawa
authors.forename: J Carl
authors.initials: JC
authors.lastname: Barrett
authors.forename: Takeki
authors.initials: T
authors.lastname: Tsutsui
mesh_terms: D000107:Acetylation; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002472:Cell Transformation, Viral / Q000235:genetics / Q000502:physiology*; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D004268:DNA-Binding Proteins; D000077209:Decitabine; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology / Q000821:virology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D009856:Oncogene Proteins, Viral / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics; D019098:Telomerase / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000378:metabolism
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D006877:Hydroxamic Acids; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; C012589:trichostatin A; D000077209:Decitabine; D019098:Telomerase; D001374:Azacitidine