title: Telomere shortening sensitizes cancer cells to selected cytotoxic agents: in vitro and in vivo studies and putative mechanisms.
abstract: BACKGROUND
  Telomere/telomerase system has been recently recognized as an attractive target for anticancer therapy. Telomerase inhibition results in tumor regression and increased sensitivity to various cytotoxic drugs. However, it has not been fully established yet whether the mediator of these effects is telomerase inhibition per se or telomere shortening resulting from inhibition of telomerase activity. In addition, the characteristics and mechanisms of sensitization to cytotoxic drugs caused by telomerase inhibition has not been elucidated in a systematic manner.
  
  
  RESULTS
  In this study we characterized the relative importance of telomerase inhibition versus telomere shortening in cancer cells. Sensitization of cancer cells to cytotoxic drugs was achieved by telomere shortening in a length dependent manner and not by telomerase inhibition per se. In our system this sensitization was related to the mechanism of action of the cytotoxic drug. In addition, telomere shortening affected also other cancer cell functions such as migration. Telomere shortening induced DNA damage whose repair was impaired after administration of cisplatinum while doxorubicin or vincristine did not affect the DNA repair. These findings were verified also in in vivo mouse model. The putative explanation underlying the phenotype induced by telomere shortening may be related to changes in expression of various microRNAs triggered by telomere shortening.
  
  
  CONCLUSIONS
  To our best knowledge this is the first study characterizing the relative impact of telomerase inhibition and telomere shortening on several aspects of cancer cell phenotype, especially related to sensitivity to cytotoxic drugs and its putative mechanisms. The microRNA changes in cancer cells upon telomere shortening are novel information. These findings may facilitate the development of telomere based approaches in treatment of cancer.
authors.affiliation: Beilinson Hospital, Rabin Medical Center, Felsenstein Medical Research Center, Petah-Tikva, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
authors.forename: Orit
authors.initials: O
authors.lastname: Uziel
authors.forename: Einat
authors.initials: E
authors.lastname: Beery
authors.forename: Vladimir
authors.initials: V
authors.lastname: Dronichev
authors.forename: Katty
authors.initials: K
authors.lastname: Samocha
authors.forename: Sergei
authors.initials: S
authors.lastname: Gryaznov
authors.forename: Lola
authors.initials: L
authors.lastname: Weiss
authors.forename: Shimon
authors.initials: S
authors.lastname: Slavin
authors.forename: Michal
authors.initials: M
authors.lastname: Kushnir
authors.forename: Yardena
authors.initials: Y
authors.lastname: Nordenberg
authors.forename: Claudette
authors.initials: C
authors.lastname: Rabinowitz
authors.forename: Baruch
authors.initials: B
authors.lastname: Rinkevich
authors.forename: Tania
authors.initials: T
authors.lastname: Zehavi
authors.forename: Meir
authors.initials: M
authors.lastname: Lahav
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D020552:Comet Assay; D004249:DNA Damage; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D020014:K562 Cells; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D009841:Oligonucleotides / Q000494:pharmacology; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C479222:GRN163; D009841:Oligonucleotides; D019098:Telomerase; D002945:Cisplatin