title: Targeting nucleophosmin 1 represents a rational strategy for radiation sensitization.
abstract: OBJECTIVE
  To test the hypothesis that small molecule targeting of nucleophosmin 1 (NPM1) represents a rational approach for radiosensitization.
  
  
  METHODS
  Wilde-type and NPM1-deficient mouse embryo fibroblasts (MEFs) were used to determine whether radiosensitization produced by the small molecule YTR107 was NPM1 dependent. The stress response to ionizing radiation was assessed by quantifying pNPM1, γH2AX, and Rad51 foci, neutral comet tail moment, and colony formation. NPM1 levels in a human-derived non-small-cell lung cancer (NSCLC) tissue microarray (TMA) were determined by immunohistochemistry. YTR107-mediated radiosensitization was assessed in NSCLC cell lines and xenografts.
  
  
  RESULTS
  Use of NPM1-null MEFs demonstrated that NPM1 is critical for DNA double- strand break (DSB) repair, that loss of NPM1 increases radiation sensitivity, and that YTR107-mediated radiosensitization is NPM1 dependent. YTR107 was shown to inhibit NPM1 oligomerization and impair formation of pNPM1 irradiation-induced foci that colocalized with γH2AX foci. Analysis of the TMA demonstrated that NPM1 is overexpressed in subsets of NSCLC. YTR107 inhibited DNA DSB repair and radiosensitized NSCLC lines and xenografts.
  
  
  CONCLUSIONS
  These data demonstrate that YTR107-mediated targeting of NPM1 impairs DNA DSB repair, an event that increases radiation sensitivity.
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Konjeti R
authors.initials: KR
authors.lastname: Sekhar
authors.affiliation: Department of Radiation Oncology, University of Virginia School of Medicine, Charlottesville, Virginia.
authors.forename: Mouadh
authors.initials: M
authors.lastname: Benamar
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Amudhan
authors.initials: A
authors.lastname: Venkateswaran
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Soumya
authors.initials: S
authors.lastname: Sasi
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
authors.forename: Narsimha R
authors.initials: NR
authors.lastname: Penthala
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Crooks
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Hann
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Ling
authors.initials: L
authors.lastname: Geng
authors.affiliation: Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Balusu
authors.affiliation: Department of Radiation Oncology, University of Virginia School of Medicine, Charlottesville, Virginia.
authors.forename: Tarek
authors.initials: T
authors.lastname: Abbas
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, Tennessee. Electronic address: michael.freeman@vanderbilt.edu.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Freeman
mesh_terms: D000818:Animals; D001463:Barbiturates / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000737:chemistry / Q000532:radiotherapy; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000187:drug effects*; D005347:Fibroblasts / Q000737:chemistry / Q000528:radiation effects; D006657:Histones / Q000032:analysis; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000737:chemistry / Q000532:radiotherapy; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D058990:Molecular Targeted Therapy / Q000379:methods*; D009363:Neoplasm Proteins / Q000032:analysis / Q000172:deficiency / Q000187:drug effects* / Q000502:physiology; D009687:Nuclear Proteins / Q000032:analysis / Q000172:deficiency / Q000187:drug effects* / Q000502:physiology; D000090243:Nucleophosmin; D051135:Rad51 Recombinase / Q000032:analysis; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D046888:Tissue Array Analysis; D014407:Tumor Cells, Cultured
chemical_list: C569647:5-((N-benzyl-1H-indol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)trione; D001463:Barbiturates; D006657:Histones; D007211:Indoles; C000716967:NPM1 protein, human; D009363:Neoplasm Proteins; C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D011838:Radiation-Sensitizing Agents; C475961:gamma-H2AX protein, mouse; D000090243:Nucleophosmin; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse