title: Murine double minute 2 as a therapeutic target for radiation sensitization of lung cancer.
abstract: Murine double minute 2 (MDM2) inhibits p53-mediated functions, which are essential for therapies using DNA-damaging agents. The purpose of this study was to determine whether MDM2 inhibition enhances the radiosensitivity of a lung cancer model. The effects of MDM2 inhibition on tumor vasculature were also studied. Transient transfection of H460 lung cancer cells and human umbilical vascular endothelial cells (HUVEC) with antisense oligonucleotides (ASODN) against MDM2 resulted in a reduced level of MDM2 and increased levels of p21 and p53. Clonogenic assays showed that inhibition of MDM2 greatly decreased cell survival following irradiation. Quantification of apoptotic cells by 7-aminoactinomycin D staining and of senescent cells by X-gal staining showed that both processes were significantly increased in H460 cells treated with MDM2-specific ASODN and radiation. H460 xenografts that were treated with MDM2 ASODN plus radiotherapy also showed significant growth delay (P < 0.001) and increased apoptosis by terminal deoxynucleotidyl transferase-mediated nick end labeling staining. HUVECs transfected with MDM2-specific ASODN showed impaired viability and migration with decreased tube formation. Doppler studies showed that tumor blood flow was compromised when H460 xenografts were treated with MDM2-specific ASODN and radiation. A combination of radiotherapy and inhibition of MDM2 through the antisense approach results in improved tumor control in the H460 lung cancer model. This implies that a similar strategy should be investigated among patients with locally advanced lung cancer, receiving thoracic radiotherapy.
authors.affiliation: Department of Radiation Oncology, Vanderbilt University, 1301 22nd Avenue South, B-902 The Vanderbilt Clinic, Nashville, TN 37232-5671, USA.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Cao
authors.forename: Eric T
authors.initials: ET
authors.lastname: Shinohara
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Niermann
authors.forename: Edwin F
authors.initials: EF
authors.lastname: Donnelly
authors.forename: Xinping
authors.initials: X
authors.lastname: Chen
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Hallahan
authors.forename: Bo
authors.initials: B
authors.lastname: Lu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D018797:Cell Cycle Proteins / Q000378:metabolism; D016922:Cellular Senescence / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004730:Endothelium, Vascular / Q000166:cytology / Q000528:radiation effects; D006801:Humans; D008175:Lung Neoplasms / Q000098:blood supply / Q000235:genetics / Q000532:radiotherapy*; D051379:Mice; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000627:therapeutic use*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D051736:Proto-Oncogene Proteins c-mdm2; D011838:Radiation-Sensitizing Agents; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014470:Umbilical Cord / Q000166:cytology; D015854:Up-Regulation
chemical_list: C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D011838:Radiation-Sensitizing Agents; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2