title: Dependency of repair of radiation-induced damage on p53 status and efficient inhibition of the repair with wortmannin treatment in vivo, with reference to the effect on intratumor quiescent cell population.
abstract: To examine the dependency of p53 status and the effect of wortmannin on the repair of radiation-induced damage, referring to the response of intratumor quiescent (Q) cells. Human head and neck squamous cell carcinoma cells transfected with mutant TP53 (SAS/mp53) or with neo vector (SAS/neo) were injected subcutaneously into left hind legs of nude mice. Tumor-bearing mice received 5-bromo-2'-deoxyuridine (BrdU) continuously to label all intratumor proliferating (P) cells. They received high dose-rate gamma-ray irradiation (HDRI) immediately followed by caffeine or wortmannin administration, or reduced dose-rate gamma-ray irradiation simultaneously with caffeine or wortmannin administration. Nine hours after the start of irradiation, the tumor cells were isolated and incubated with a cytokinesis blocker, and the micronucleus (MN) frequency in cells without BrdU labeling (Q cells) was determined using immunofluorescence staining for BrdU. SAS/neo tumor cells, especially intratumor Q cell populations, showed a marked reduction in sensitivity due to the repair of radiation-induced damage, compared with the total or Q cell populations within SAS/mp53 tumors that showed little repair capacity. In both total and Q cell populations within SAS/neo tumors, wortmannin efficiently suppressed the reduction in sensitivity caused by leaving an interval between HDRI and the assay and decreasing the irradiation dose rate. The repair of radiation-induced damage was thought to be a p53-dependent event. From the viewpoint of tumor control, including intratumor Q-cell control, wortmannin treatment in combination with gamma-ray irradiation is thought to be useful for suppressing the repair of radiation-induced damage.
authors.affiliation: Particle Radiation Oncology Research Center, Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan. smasuna@rri.kyoto-u.ac.jp
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Masunaga
authors.forename: Akihisa
authors.initials: A
authors.lastname: Takahashi
authors.forename: Ken
authors.initials: K
authors.lastname: Ohnishi
authors.forename: Kenji
authors.initials: K
authors.lastname: Nagata
authors.forename: Minoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Genro
authors.initials: G
authors.lastname: Kashino
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kinashi
authors.forename: Takeo
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Koji
authors.initials: K
authors.lastname: Ono
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects*; D042822:Genomic Instability; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D015162:Micronucleus Tests; D009183:Mycotoxins / Q000494:pharmacology; D011878:Radiotherapy; D014183:Transplantation, Heterologous; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D009183:Mycotoxins; D016159:Tumor Suppressor Protein p53; D002110:Caffeine; D000077191:Wortmannin