Telomere Targeting with a New G4 Ligand Enhances Radiation-Induced Killing of Human Glioblastoma Cells

Patrick Merle,Anne Petitjean,Marie-Paule Teulade-Fichou,Emmanuel Chautard,Jean-Marie Lehn,Andreï Tchirkov,Lionel Guittat,Anne De Cian,Bertrand Evrard,Jean-Louis Mergny,Pierre Verrelle,Phong Lan Thao Tran

doi:10.1158/1535-7163.mct-10-0664

Abstract

The aim of this study was to test in vitro the efficacy of TAC, an original G-quadruplex ligand, as a potential radiosensitizing agent for glioblastoma multiforme (GBM). Two human radioresistant telomerase-positive GBM cell lines (SF763 and SF767) were analyzed, with and without TAC treatment, for telomere length, cell proliferation, apoptosis, cell-cycle distribution, gene expression, cytogenetic aberrations, clonogenic survival assay, 53BP1 immunofluorescence staining, and γH2AX phosphorylation. We found that low concentrations of TAC (0.5 and 1 μmol/L) inhibited the proliferation of GBM cells in a concentration-dependent manner after only 1 week of treatment, with minimal effects on cell cycle and apoptosis. TAC treatment had no visible effect on average telomere length but modified expression levels of telomere-related genes (hTERT, TRF1, and TRF2) and induced concentration-dependent DNA damage response and dicentric chromosomes. Survival curves analysis showed that exposure to nontoxic, subapoptotic concentrations of TAC enhanced radiation-induced killing of GBM cells. Analysis of DNA repair after irradiation revealed delayed repair kinetics in GBM cells treated with TAC. Furthermore, the combined treatment (TAC and radiation) significantly increased the frequency of chromosomal aberrations as compared with radiation alone. These findings provide the first evidence that exposure to a G4 ligand radiosensitizes human glioblastoma cells and suggest the prospect of future therapeutic applications.

Highlights

Glioblastoma multiforme (GBM) is the most common human primary brain tumor with a very poor prognosis
Telomere damage and DNA damage response induced by G4 ligands such as RHPS4, BRACO19, and
Telomestatin [37,38,39] lead to a short-term inhibition of proliferation and rapid apoptosis of tumor cells. In line with these reports, we found that low concentrations of TAC (0.5 and 1 mmol/L) inhibited the proliferation of GBM cells in a concentration-dependent manner after only 1 week of treatment

Summary

Introduction

Glioblastoma multiforme (GBM) is the most common human primary brain tumor with a very poor prognosis. GBM patients are treated by neurosurgery followed by radiotherapy with concomitant administration of temozolomide [1]. This treatment is not curative, and the tumor. Authors' Affiliations: 1Laboratoire d’Immunologie, 2Histologie Embryologie Cytogenetique, and 3EA 3846, Clermont Universite, Universite d’Auvergne; 4Service de Pneumologie, 5Laboratoire d’Immunologie, and 6Service de Cytogenetique Medicale, CHU Clermont-Ferrand; 7Departement de Radiotherapie, Centre Jean Perrin, Clermont-Ferrand; 8ISIS, Universite de Strasbourg, Strasbourg, France; 9Department of Chemistry, Queen's University, Kingston, Ontario, Canada; 10Institut Curie, UMR 176, Centre Universitaire, Orsay; 11INSERM U565, Museum National d’Histoire Naturelle, CNRS UMR 7196, Paris; and 12INSERM U869, Institut Europeen de Chimie Biologie, Universite de Bordeaux, Pessac, France.

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