title: Short-term inhibition of TERT induces telomere length-independent cell cycle arrest and apoptotic response in EBV-immortalized and transformed B cells.
abstract: Besides its canonical role in stabilizing telomeres, telomerase reverse transcriptase (TERT) may promote tumorigenesis through extra-telomeric functions. The possible therapeutic effects of BIBR1532 (BIBR), a powerful TERT inhibitor, have been evaluated in different cellular backgrounds, but no data are currently available regarding Epstein-Barr virus (EBV)-driven B-cell malignancies. Our aim was to characterize the biological effects of TERT inhibition by BIBR on EBV-immortalized lymphoblastoid cell lines (LCLs) and fully transformed Burkitt's lymphoma (BL) cell lines. We found that BIBR selectively inhibits telomerase activity in TERT-positive 4134/Late and 4134/TERT+ LCLs and EBV-negative BL41 and EBV-positive BL41/B95.8 BL cell lines. TERT inhibition led to decreased cell proliferation, accumulation of cells in the S-phase and ultimately to increased apoptosis, compared with mock-treated control cells. All these effects occurred within 72 h and were not observed in BIBR-treated TERT-negative 4134/TERT- and U2OS cells. The cell cycle arrest and apoptosis, consequent upon short-term TERT inhibition, were associated with and likely dependent on the activation of the DNA damage response (DDR), highlighted by the increased levels of γH2AX and activation of ATM and ATR pathways. Analyses of the mean and range of telomere lengths and telomere dysfunction-induced foci indicated that DDR after short-term TERT inhibition was not related to telomere dysfunction, thus suggesting that TERT, besides stabilizing telomere, may protect DNA via telomere-independent mechanisms. Notably, TERT-positive LCLs treated with BIBR in combination with fludarabine or cyclophosphamide showed a significant increase in the number of apoptotic cells with respect to those treated with chemotherapeutic agents alone. In conclusion, TERT inhibition impairs cell cycle progression and enhances the pro-apoptotic effects of chemotherapeutic agents in TERT-positive cells. These results support new therapeutic applications of TERT inhibitors in EBV-driven B-cell malignancies.
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Celeghin
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Giunco
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Freguja
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Zangrossi
authors.affiliation: Immunology and Molecular Oncology Unit, Istituto Oncologico Veneto (IOV)-IRCCS, Padova, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Nalio
authors.affiliation: Cancer Bio-Immunotherapy Unit, CRO-IRCCS, National Cancer Institute, Aviano, Italy.|University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Queensland, Australia.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Dolcetti
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.|Immunology and Molecular Oncology Unit, Istituto Oncologico Veneto (IOV)-IRCCS, Padova, Italy.
authors.forename: Anita
authors.identifier: 0000-0001-6435-7509
authors.initials: A
authors.lastname: De Rossi
mesh_terms: D062365:Aminobenzoates; D017209:Apoptosis / Q000187:drug effects*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism* / Q000821:virology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D003520:Cyclophosphamide / Q000494:pharmacology; D004854:Herpesvirus 4, Human / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D009281:Naphthalenes; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016615:Telomere / Q000187:drug effects / Q000378:metabolism*; D059505:Telomere Homeostasis / Q000187:drug effects; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D062365:Aminobenzoates; C458523:BIBR 1532; C468783:H2AX protein, human; D006657:Histones; D009281:Naphthalenes; D003520:Cyclophosphamide; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C509186:TERT protein, human; D019098:Telomerase; D014740:Vidarabine; C024352:fludarabine