Induction of radiation resistance by a heat shock protein inhibitor, KNK437, in human glioblastoma cells.
OBJECTIVE
We examined the effects of a heat shock protein (hsp) inhibitor, N-formyl-3, 4-methylenedioxy-gamma-butyrolactam (KNK437), on the radiosensitivity of human glioblastoma cells (A-172).


METHODS
Effects of KNK437 on radiosensitivity and cell cycle regulation were examined using colony formation assays, flow cytometry analysis and Western blot analysis. KNK437 was added to the culture medium 1 h before X-ray irradiation at 50, 100 or 300 microM final concentration.


RESULTS
KNK437 induced the resistance of A-172 cells and human squamous cell carcinoma cells (SAS) to X-rays. Flow cytometry analysis showed that KNK437 alone efficiently induced A-172 cells to enter G2/M phase. Though A-172 cells irradiated with X-rays at 6 Gy showed no clear change in the cell cycle, the irradiated cells were induced to enter G2/M phase when they had been pre-treated with KNK437. By Western blot analysis, p53, 14-3-3sigma and cell division cycle 2 (cdc2) proteins that function in G2 arrest were observed to be persistently accumulated or phosphorylated in KNK437-treated cells, regardless of X-ray irradiation.


CONCLUSIONS
These results show that KNK437 causes cells to be resistant to radiation, and that this might be correlated with maintenance of G2 arrest in the cell cycle regulation.
Ohnishi
Ken
K
Department of Biology, Nara Medical University School of Medicine, Kashihara, Nara, Japan.
Yokota
Shinichi
S
Takahashi
Akihisa
A
Ohnishi
Takeo
T
D001559:Benzhydryl Compounds / Q000008:administration & dosage*; D002453:Cell Cycle / Q000187:drug effects* / Q000528:radiation effects*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D011760:Pyrrolidinones / Q000008:administration & dosage*; D011836:Radiation Tolerance / Q000187:drug effects*
D001559:Benzhydryl Compounds; D006360:Heat-Shock Proteins; C410027:KNK 437; D011760:Pyrrolidinones