title: Cathepsin L suppression increases the radiosensitivity of human glioma U251 cells via G2/M cell cycle arrest and DNA damage.
abstract: OBJECTIVE
  Cathepsin L is a lysosomal cysteine protease that plays important roles in cancer tumorigenesis, proliferation and chemotherapy resistance. The aim of this study was to determine how cathepsin L regulated the radiosensitivity of human glioma cells in vitro.
  
  
  METHODS
  Human glioma U251 cells (harboring the mutant type p53 gene) and U87 cells (harboring the wide type p53 gene) were irradiated with X-rays. The expression of cathepsin L was analyzed using Western blot and immunofluorescence assays. Cell survival and DNA damage were evaluated using clonogenic and comet assays, respectively. Flow cytometry was used to detect the cell cycle distribution. Apoptotic cells were observed using Hoechst 33258 staining and fluorescence microscopy.
  
  
  RESULTS
  Irradiation significantly increased the cytoplasmic and nuclear levels of cathepsin L in U251 cells but not in U87 cells. Treatment with the specific cathepsin L inhibitor Z-FY-CHO (10 μmol/L) or transfection with cathepsin L shRNA significantly increased the radiosensitivity of U251 cells. Both suppression and knockdown of cathepsin L in U251 cells increased irradiation-induced DNA damage and G2/M phase cell cycle arrest. Both suppression and knockdown of cathepsin L in U251 cells also increased irradiation-induced apoptosis, as shown by the increased levels of Bax and decreased levels of Bcl-2.
  
  
  CONCLUSIONS
  Cathepsin L is involved in modulation of radiosensitivity in human glioma U251 cells (harboring the mutant type p53 gene) in vitro.
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215000, China.
authors.forename: Qing-qing
authors.initials: QQ
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215000, China.
authors.forename: Wen-juan
authors.initials: WJ
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215000, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215000, China.
authors.forename: Neng
authors.initials: N
authors.lastname: Yang
authors.affiliation: Department of Neurosurgery, The First Affiliated Hospital of Soochow University, Suzhou 215000, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.affiliation: Department of Neurosurgery, The First Affiliated Hospital of Soochow University, Suzhou 215000, China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215000, China.
authors.forename: Zhong-qin
authors.initials: ZQ
authors.lastname: Liang
mesh_terms: D017209:Apoptosis / Q000528:radiation effects; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D056668:Cathepsin L / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000528:radiation effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D059565:G2 Phase Cell Cycle Checkpoints / Q000528:radiation effects*; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D056668:Cathepsin L