title: 5-iodo-2-pyrimidinone-2'-deoxyribose-mediated cytotoxicity and radiosensitization in U87 human glioblastoma xenografts.
abstract: OBJECTIVE
  5-iodo-2-pyrimidinone-2'-deoxyribose (IPdR) is a novel orally administered (p.o.) prodrug of 5-iododeoxyuridine. Because p.o. IPdR is being considered for clinical testing as a radiosensitizer in patients with high-grade gliomas, we performed this in vivo study of IPdR-mediated cytotoxicity and radiosensitization in a human glioblastoma xenograft model, U87.
  
  
  METHODS
  Groups of 8 or 9 athymic male nude mice (6-8 weeks old) were implanted with s.c. U87 xenograft tumors (4 x 10(6) cells) and then randomized to 10 treatment groups receiving increasing doses of p.o. IPdR (0, 100, 250, 500, and 1000 mg/kg/d) administered once daily (q.d.) x 14 days with or without radiotherapy (RT) (0 or 2 Gy/d x 4 days) on days 11-14 of IPdR treatment. Systemic toxicity was determined by body weight measurements during and after IPdR treatment. Tumor response was assessed by changes in tumor volumes.
  
  
  RESULTS
  IPdR alone at doses of > or =500 mg/kg/d resulted in moderate inhibition of tumor growth. The combination of IPdR plus RT resulted in a significant IPdR dose-dependent tumor growth delay, with the maximum radiosensitization using > or =500 mg/kg/d. IPdR doses of 500 and 1000 mg/kg/d resulted in transient 5-15% body weight loss during treatment.
  
  
  CONCLUSIONS
  In U87 human glioblastoma s.c. xenografts, p.o. IPdR given q.d. x 14 days and RT given 2 Gy/d x 4 days (days 11-14 of IPdR treatment) results in a significant tumor growth delay in an IPdR dose-dependent pattern. The use of p.o. IPdR plus RT holds promise for Phase I/II testing in patients with high-grade gliomas.
authors.affiliation: Department of Radiation Oncology, University Hospitals Case Medical Center, Cleveland, OH 44106-6068, USA. timothy.kinsella@UHhospitals.org
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kinsella
authors.forename: Michael T
authors.initials: MT
authors.lastname: Kinsella
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seo
authors.forename: Gregory
authors.initials: G
authors.lastname: Berk
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005909:Glioblastoma / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011355:Prodrugs / Q000627:therapeutic use*; D011741:Pyrimidine Nucleosides / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D011897:Random Allocation; D047368:Tumor Burden / Q000187:drug effects / Q000528:radiation effects; D023041:Xenograft Model Antitumor Assays / Q000379:methods
chemical_list: D011355:Prodrugs; D011741:Pyrimidine Nucleosides; D011838:Radiation-Sensitizing Agents; C045889:ropidoxuridine