title: Telomerase inhibition potentiates the effects of genotoxic agents in breast and colorectal cancer cells in a cell cycle-specific manner.
abstract: Previous studies have shown that telomerase facilitates DNA-damage repair and cell survival following stress. It is not clear how telomerase promotes DNA repair, or whether short-term telomerase inhibition, combined with genotoxic stress, can be exploited for cancer therapy. Here, we show that transient inhibition of telomerase activity by the specific inhibitor, GRN163L, increases the cytotoxicity of some, but not all, DNA-damaging agents. Such synergistic inhibition of growth requires the use of DNA-damaging agents that are toxic in the S/G(2) phase of the cell cycle. Notably, inhibition of Ataxia Telangiectasia Mutated (ATM) kinase, together with telomerase inhibition, synergistically increases the cytotoxicity induced by the G(2)-specific topoisomerase II inhibitor etoposide. By varying the timing of telomerase inhibition, relative to the timing of DNA damage, it is apparent that the prosurvival functions of telomerase occur at early stages of DNA damage recognition and repair. Our results suggest that the protective role of telomerase in cell cycle-restricted DNA damage repair could be exploited for combined anticancer chemotherapy.
authors.affiliation: Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Raina A
authors.initials: RA
authors.lastname: Tamakawa
authors.forename: Helen B
authors.initials: HB
authors.lastname: Fleisig
authors.forename: Judy M Y
authors.initials: JM
authors.lastname: Wong
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003114:Colony-Forming Units Assay; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D004249:DNA Damage / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D009841:Oligonucleotides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C505952:GRN163L peptide; D009841:Oligonucleotides; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C509186:TERT protein, human; D019098:Telomerase