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.
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.
Masunaga
Shin-ichiro
S
Particle Radiation Oncology Research Center, Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan. smasuna@rri.kyoto-u.ac.jp
Takahashi
Akihisa
A
Ohnishi
Ken
K
Nagata
Kenji
K
Suzuki
Minoru
M
Kashino
Genro
G
Kinashi
Yuko
Y
Ohnishi
Takeo
T
Ono
Koji
K
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
D000730:Androstadienes; D009183:Mycotoxins; D016159:Tumor Suppressor Protein p53; D002110:Caffeine; D000077191:Wortmannin