VE-821, an ATR inhibitor, causes radiosensitization in human tumor cells irradiated with high LET radiation.

Hiroshi Fujisawa,Nakako Izumi Nakajima,Akira Fujimori,Mitsuru Uesaka,Ryuichi Okayasu,Younghyun Lee,Hirokazu Hirakawa,Hirohiko Yajima,Shigeaki Sunada

doi:10.1186/s13014-015-0464-y

Hiroshi Fujisawa, Nakako Izumi Nakajima + Show 7 more

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https://doi.org/10.1186/s13014-015-0464-y

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Abstract

BackgroundHigh linear energy transfer (LET) radiation such as carbon ion particles is successfully used for treatment of solid tumors. The reason why high LET radiation accomplishes greater tumor-killing than X-rays is still not completely understood. One factor would be the clustered or complex-type DNA damages. We previously reported that complex DNA double-strand breaks produced by high LET radiation enhanced DNA end resection, and this could lead to higher kinase activity of ATR protein recruited to RPA-coated single-stranded DNA. Although the effect of ATR inhibition on cells exposed to low LET gamma-rays has recently been reported, little is known regarding the effect of ATR inhibitor on cells treated with high LET radiation. The purpose of this study is to investigate the effects of the ATR inhibitor VE-821 in human tumor and normal cells irradiated with high LET carbon ions.FindingsHeLa, U2OS, and 1BR-hTERT (normal) cells were pre-treated with 1 μM VE-821 for 1 hour and irradiated with either high LET carbon ions or X-rays. Cell survival, cell cycle distribution, cell growth, and micronuclei formation were evaluated. VE-821 caused abrogation of G2/M checkpoint and forced irradiated cells to divide into daughter cells. We also found that carbon ions caused a higher number of multiple micronuclei than X-rays, leading to decreased cell survival in tumor cells when treated with VE-821, while the survival of irradiated normal cells were not significantly affected by this inhibitor.ConclusionsATR inhibitor would be an effective tumor radiosensitizer with carbon ion irradiation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-015-0464-y) contains supplementary material, which is available to authorized users.

Highlights

High linear energy transfer (LET) radiation such as carbon ion particles is successfully used for treatment of solid tumors
The ataxia telangiectasia mutated and Rad3-related (ATR) inhibitor VE-821 radiosensitized human tumor cells irradiated with high LET carbon ions To assess ATR inhibition on radiation sensitivity, cellular survivals were acquired using a colony formation assay
Relative biological effectiveness (RBE) based on D10 values, at a dose resulting in one decade of cell killing, was calculated as X-ray dose leading to 0.1 survival divided by carbon dose leading to 0.1 survival (Table 1)

Summary

Introduction

High linear energy transfer (LET) radiation such as carbon ion particles is successfully used for treatment of solid tumors. The reason why high LET radiation accomplishes greater tumor-killing than X-rays is still not completely understood. One factor would be the clustered or complex-type DNA damages. We previously reported that complex DNA double-strand breaks produced by high LET radiation enhanced DNA end resection, and this could lead to higher kinase activity of ATR protein recruited to RPA-coated single-stranded DNA. The effect of ATR inhibition on cells exposed to low LET gamma-rays has recently been reported, little is known regarding the effect of ATR inhibitor on cells treated with high LET radiation. The purpose of this study is to investigate the effects of the ATR inhibitor VE-821 in human tumor and normal cells irradiated with high LET carbon ions

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