title: Enhanced radiation-induced cytotoxic effect by 2-ME in glioma cells is mediated by induction of cell cycle arrest and DNA damage via activation of ATM pathways.
abstract: Glioblastoma multiform is the most common malignant primary brain tumor in adults, but there remains no effective therapeutic approach. 2-methoxyestradiol (2-ME), which is a naturally occurring metabolite of 17beta-estradiol, was shown to enhance radiotherapeutic effect in certain tumors; however, whether 2-ME can also enhance the sensitivity of glioma cells to radiotherapy remains unknown. The present study, therefore, was to address this issue using two human glioma cell lines (T98G and U251MG). These cells were irradiated with and without 2-ME and then clonogenic assay, apoptosis assay, DNA damage, and cell cycle change were examined. Results showed that 2-ME significantly enhances radiation-induced cell death in both glioma cells, shown by decreasing cell viability and increasing apoptotic cell death. No such radiosensitizing effect was observed if cells pre-treated with Estrodiol, suggesting the specifically radiosensitizing effect of 2-ME rather than a general effect of estrodials. The enhanced radio-cytotoxic effect in glioma cells by 2-ME was found to be associated with its enhancement of G(2)/M arrest and DNA damage, and phosphorylated ATM protein kinases as well as cell cycle checkpoint protein Chk2. Furthermore, inhibition of ATM by ATM inhibitor abolished 2-ME-activated Chk2 and enhanced radio-cytotoxic effects. These results suggest that 2-ME enhancement of the sensitivity of glioma cell lines to radiotherapy is mediated by induction of G2/M cell cycle arrest and increased DNA damage via activation of ATM kinases.
authors.affiliation: The 1st Affiliated Hospital of Harbin Medical University, No.23 Youzheng Street, Nangang District, Harbin, Heilongjiang Province, China.
authors.forename: Huichao
authors.initials: H
authors.lastname: Zou
authors.forename: Shiguang
authors.initials: S
authors.lastname: Zhao
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Gongwei
authors.initials: G
authors.lastname: Lv
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.forename: Hongwei
authors.initials: H
authors.lastname: Yu
authors.forename: Huibo
authors.initials: H
authors.lastname: Wang
authors.forename: Ligang
authors.initials: L
authors.lastname: Wang
mesh_terms: D000077584:2-Methoxyestradiol; D000704:Analysis of Variance; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004958:Estradiol / Q000031:analogs & derivatives* / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D005910:Glioma / Q000503:physiopathology* / Q000628:therapy; D006657:Histones / Q000378:metabolism; D006801:Humans; D007211:Indoles; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D011878:Radiotherapy / Q000379:methods*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D007211:Indoles; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C007293:DAPI; D004958:Estradiol; D000077584:2-Methoxyestradiol; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases