title: Inhibition of cathepsin L sensitizes human glioma cells to ionizing radiation in vitro through NF-κB signaling pathway.
abstract: OBJECTIVE
  Cathepsin L, a lysosomal cysteine proteinase, is exclusively elevated in a variety of malignancies, including gliomas. In this study we investigated the relationship between cathepsin L and NF-κB, two radiation-responsive elements, in regulating the sensitivity of human glioma cells ionizing radiation (IR) in vitro.
  
  
  METHODS
  Human glioma U251 cells were exposed to IR (10 Gy), and the expression of cathepsin L and NF-κB was measured using Western blotting. The nuclear translocation of NF-κB p65 and p50 was analyzed with immunofluorescence assays. Cell apoptosis was examined with clonogenic assays. NF-κB transcription and NF-κB-dependent cyclin D1 and ATM transactivation were monitored using luciferase reporter and ChIP assays, respectively. DNA damage repair was investigated using the comet assay.
  
  
  RESULTS
  IR significantly increased expression of cathepsin L and NF-κB p65 and p50 in the cells. Furthermore, IR significantly increased the nuclear translocation of NF-κB, and NF-κB-dependent cyclin D1 and ATM transactivation in the cells. Knockdown of p65 did not change the expression of cathepsin L in IR-treated cells. Pretreatment with Z-FY-CHO (a selective cathepsin L inhibitor), or knockdown of cathepsin L significantly attenuated IR-induced nuclear translocation of NF-κB and cyclin D1 and ATM transactivation, and sensitized the cells to IR. Pretreatment with Z-FY-CHO, or knockdown of p65 also decreased IR-induced DNA damage repair and clonogenic cell survival, and sensitized the cells to IR.
  
  
  CONCLUSIONS
  Cathepsin L acts as an upstream regulator of NF-κB activation in human glioma cells and contributes to their sensitivity to IR in vitro. Inhibition of cathepsin L can sensitize the cells to IR.
authors: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China.
authors: Neng
authors: N
authors: Yang
authors: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China.
authors: Pan
authors: P
authors: Wang
authors: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China.
authors: Wen-juan
authors: WJ
authors: Wang
authors: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China.
authors: Yun-zhen
authors: YZ
authors: Song
authors: Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou 215123, China.
authors: Zhong-qin
authors: ZQ
authors: Liang
mesh_terms: D021581:Active Transport, Cell Nucleus; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001932:Brain Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D056668:Cathepsin L / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D005910:Glioma / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology / Q000528:radiation effects*; D034622:RNA Interference; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects* / Q000528:radiation effects*; D013997:Time Factors; D051996:Transcription Factor RelA / Q000378:metabolism; D014162:Transfection
chemical_list: C530104:CCND1 protein, human; D015853:Cysteine Proteinase Inhibitors; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C489548:NFKB1 protein, human; C498143:RELA protein, human; D011838:Radiation-Sensitizing Agents; D051996:Transcription Factor RelA; D019938:Cyclin D1; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C534281:CTSL protein, human; D056668:Cathepsin L