DNA double-strand break induction in Ku80-deficient CHO cells following Boron Neutron Capture Reaction

Radiation Oncology

Koji Ono²  Minoru Suzuki²  Shinichiro Masunaga²  Ryuichi Okayasu¹  Genro Kashino³  Sentaro Takahashi²  Yuko Kinashi² 

[1] National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan;Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan;Oita University, Faculty of Medicine, Hazama-cho, Yufu-city, Oita 879-5593, Japan

关键词: 53BP1;    gamma-H2AX;    BNCR;    DNA-DSB;    xrs-5;   

Others  :  1223909
DOI  :  10.1186/1748-717X-6-106

 received in 2011-04-25, accepted in 2011-09-05,  发布年份 2011

【 摘 要 】

Background

Boron neutron capture reaction (BNCR) is based on irradiation of tumors after accumulation of boron compound. ¹⁰B captures neutrons and produces an alpha (⁴He) particle and a recoiled lithium nucleus (⁷Li). These particles have the characteristics of high linear energy transfer (LET) radiation and have marked biological effects. The purpose of this study is to verify that BNCR will increase cell killing and slow disappearance of repair protein-related foci to a greater extent in DNA repair-deficient cells than in wild-type cells.

Methods

Chinese hamster ovary (CHO-K1) cells and a DNA double-strand break (DSB) repair deficient mutant derivative, xrs-5 (Ku80 deficient CHO mutant cells), were irradiated by thermal neutrons. The quantity of DNA-DSBs following BNCR was evaluated by measuring the phosphorylation of histone protein H2AX (gamma-H2AX) and 53BP1 foci using immunofluorescence intensity.

Results

Two hours after neutron irradiation, the number of gamma-H2AX and 53BP1 foci in the CHO-K1 cells was decreased to 36.5-42.8% of the levels seen 30 min after irradiation. In contrast, two hours after irradiation, foci levels in the xrs-5 cells were 58.4-69.5% of those observed 30 min after irradiation. The number of gamma-H2AX foci in xrs-5 cells at 60-120 min after BNCT correlated with the cell killing effect of BNCR. However, in CHO-K1 cells, the RBE (relative biological effectiveness) estimated by the number of foci following BNCR was increased depending on the repair time and was not always correlated with the RBE of cytotoxicity.

Conclusion

Mutant xrs-5 cells show extreme sensitivity to ionizing radiation, because xrs-5 cells lack functional Ku-protein. Our results suggest that the DNA-DSBs induced by BNCR were not well repaired in the Ku80 deficient cells. The RBE following BNCR of radio-sensitive mutant cells was not increased but was lower than that of radio-resistant cells. These results suggest that gamma-ray resistant cells have an advantage over gamma-ray sensitive cells in BNCR.

【 授权许可】

   
2011 Kinashi et al; licensee BioMed Central Ltd.

【 图 表 】

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