title: L1CAM regulates DNA damage checkpoint response of glioblastoma stem cells through NBS1.
abstract: Glioblastomas (GBMs) are highly lethal brain tumours with current therapies limited to palliation due to therapeutic resistance. We previously demonstrated that GBM stem cells (GSCs) display a preferential activation of DNA damage checkpoint and are relatively resistant to radiation. However, the molecular mechanisms underlying the preferential checkpoint response in GSCs remain undefined. Here, we show that L1CAM (CD171) regulates DNA damage checkpoint responses and radiosensitivity of GSCs through nuclear translocation of L1CAM intracellular domain (L1-ICD). Targeting L1CAM by RNA interference attenuated DNA damage checkpoint activation and repair, and sensitized GSCs to radiation. L1CAM regulates expression of NBS1, a critical component of the MRE11-RAD50-NBS1 (MRN) complex that activates ataxia telangiectasia mutated (ATM) kinase and early checkpoint response. Ectopic expression of NBS1 in GSCs rescued the decreased checkpoint activation and radioresistance caused by L1CAM knockdown, demonstrating that L1CAM signals through NBS1 to regulate DNA damage checkpoint responses. Mechanistically, nuclear translocation of L1-ICD mediates NBS1 upregulation via c-Myc. These data demonstrate that L1CAM augments DNA damage checkpoint activation and radioresistance of GSCs through L1-ICD-mediated NBS1 upregulation and the enhanced MRN-ATM-Chk2 signalling.
authors.affiliation: Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Cheng
authors.forename: Qiulian
authors.initials: Q
authors.lastname: Wu
authors.forename: Zhi
authors.initials: Z
authors.lastname: Huang
authors.forename: Olga A
authors.initials: OA
authors.lastname: Guryanova
authors.forename: Qian
authors.initials: Q
authors.lastname: Huang
authors.forename: Weinian
authors.initials: W
authors.lastname: Shou
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Rich
authors.forename: Shideng
authors.initials: S
authors.lastname: Bao
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D020552:Comet Assay; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D039842:Neural Cell Adhesion Molecule L1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C489427:MYC protein, human; C112156:NBN protein, human; D039842:Neural Cell Adhesion Molecule L1; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases