AT cells are not radiosensitive for simple chromosomal exchanges at low dose

作者：Hada Megumi; Huff Janice L; Patel Zarana S; Kawata Tetsuya; Pluth Janice M; George Kerry A; Cucinotta Francis A^*

来源：Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis, 2011, 716(1-2): 76-83.

DOI：10.1016/j.mrfmmm.2011.08.006

• AT
• NBS
• Chromosomal aberrations
• Radiation sensitivity
• DSB repair

Cells deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome) show increased yields of both simple and complex chromosomal aberrations after high doses (>0.5 Gy) of ionizing radiation (X-rays or gamma-rays), however less is known on how these cells respond at low dose. Previously we had shown that the increased chromosome aberrations in ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex exchanges. The linear dose-response term for simple exchanges was significantly higher in NBS cells compared to wild type cells, but not for AT cells. However, AT cells have a high background level of exchanges compared to wild type or NBS cells that confounds the understanding of low dose responses. To understand the sensitivity differences for high to low doses, chromosomal aberration analysis was first performed at low dose-rates (0.5 Gy/d), and results provided further evidence for the lack of sensitivity for exchanges in AT cells below doses of 1 Gy. Normal lung fibroblast cells treated with KU-55933, a specific ATM kinase inhibitor, showed increased numbers of exchanges at a dose of 1 Gy and higher, but were similar to wild type cells at 0.5 Gy or below. These results were confirmed using siRNA knockdown of ATM. The present study provides evidence that the increased radiation sensitivity of AT cells for chromosomal exchanges found at high dose does not occur at low dose. Published by Elsevier B.V.

• 出版日期2011-11-1