title: Radiosensitization to X-ray radiation by telomerase inhibitor MST-312 in human hepatoma HepG2 cells.
abstract: OBJECTIVE
  Previous studies in malignant cells have shown that irradiation-induced upregulation of telomerase activity, not only protected damaged telomeres, but also contributed to DNA damage repair by chromosomal healing and increased resistance to irradiation. The purpose of the present study was to investigate the radiosensitizing effect of telomerase inhibitor MST-312 and the corresponding mechanism in the human hepatoma cell line HepG2.
  
  
  METHODS
  Cell proliferation, telomerase activity, cell cycle distribution, DNA damage and repair, expression of p53, mitochondrial membrane potential, and cell apoptosis were measured with the MTT assay, real-time fluorescent quantitative PCR, flow cytometry, immunofluorescence, western blots, JC-1 staining, and Hoechst 33258 staining, respectively.
  
  
  RESULTS
  MST-312 effectively inhibited telomerase activity and showed relative weak toxicity to HepG2 cells at 4 μM. Compared with irradiation alone, 4 μM MST-312 pretreatment, followed by X-ray treatment, significantly reduced clonogenic potential. Aggravated DNA damage and increased sub-G1 cell fractions were observed. Further investigation found that homologous recombination (HR) repair protein Rad51 foci nuclear formation was blocked, and expression of p53 was elevated. These led to the collapse of mitochondrial membrane potential, and enhanced the apoptotic rate.
  
  
  CONCLUSIONS
  These data demonstrated that disturbances of telomerase function could enhance the radiosensitivity of HepG2 cells to X-ray irradiation by impairing HR repair processes. In addition, telomerase inhibitor MST-312 may be useful as an adjuvant treatment in combination with irradiation.
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China; School of Pharmacy, Lanzhou University, Lanzhou 730000, People's Republic of China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Sun
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China.
authors.forename: Aihong
authors.initials: A
authors.lastname: Mao
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: College of Life Sciences, Yantai University, Yantai 264005, People's Republic of China.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People'sRepublic of China; Key Laboratory of Heavy Ion Radiation Medicine of Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou 730000, People's Republic of China. Electronic address: zhangh@impcas.ac.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000704:Analysis of Variance; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001549:Benzamides / Q000494:pharmacology*; D001562:Benzimidazoles; D006690:Bisbenzimidazole; D015153:Blotting, Western; D002232:Carbocyanines; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage; D017931:DNA Primers / Q000235:genetics; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D056945:Hep G2 Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000528:radiation effects; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D060888:Real-Time Polymerase Chain Reaction; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013778:Tetrazolium Salts; D013844:Thiazoles; D014965:X-Rays
chemical_list: D001549:Benzamides; D001562:Benzimidazoles; D002232:Carbocyanines; D017931:DNA Primers; C470197:MST 312; D011838:Radiation-Sensitizing Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine; D019098:Telomerase; C022616:thiazolyl blue; D006690:Bisbenzimidazole
keywords: Apoptosis; DNA repair; HepG2 cells; Radiosensitization; Telomerase inhibitor-312