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

Fujisawa H, Nakajima NI, Sunada S, Lee Y, Hirakawa H, Yajima H, Fujimori A, Uesaka M, Okayasu R - Radiat Oncol (2015)

Bottom Line: 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.ATR inhibitor would be an effective tumor radiosensitizer with carbon ion irradiation.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-8656, Japan. fujisawa@nuclear.jp.

ABSTRACT

Background: 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. 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.

Findings: HeLa, 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.

Conclusions: ATR inhibitor would be an effective tumor radiosensitizer with carbon ion irradiation.

No MeSH data available.


Related in: MedlinePlus

VE-821 abrogated carbon ion-induced G2/M cell cycle arrest in tumor cells. HeLa and U2OS cells were pre-treated with 1 μM VE-821 or DMSO for 1 hour before irradiation, and were irradiated with 3 Gy of carbon ions or 6 Gy of X-rays. a Cells were harvested at 12 and 24 hours after irradiation and their cell cycle distributions were analyzed by flow cytometry. b The number of cells was counted immediately after and 1 day after irradiation. The relative cell number was calculated as follows: cell number after 1 day was divided by cell number immediately after irradiation. Error bars represent SEM of at least three independent experiments
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Fig2: VE-821 abrogated carbon ion-induced G2/M cell cycle arrest in tumor cells. HeLa and U2OS cells were pre-treated with 1 μM VE-821 or DMSO for 1 hour before irradiation, and were irradiated with 3 Gy of carbon ions or 6 Gy of X-rays. a Cells were harvested at 12 and 24 hours after irradiation and their cell cycle distributions were analyzed by flow cytometry. b The number of cells was counted immediately after and 1 day after irradiation. The relative cell number was calculated as follows: cell number after 1 day was divided by cell number immediately after irradiation. Error bars represent SEM of at least three independent experiments

Mentions: To investigate the effect of VE-821 on the cell cycle checkpoint after irradiation, we examined the cell cycle distribution by flow cytometer. Following carbon ion irradiation, all three cell lines showed significant G2/M checkpoint arrest at 12 hours after irradiation. However, the combination with VE-821 decreased the percentage of G2/M phase, indicating abrogation of G2/M cell cycle arrest. At 24 hours after irradiation, G2/M arrest continued in cells without the drug treatment, while cells with the combination treatment showed high percentages of G1 cells, the level of which was similar to, or even higher than non-irradiated control (Fig. 2a). Irradiated 1BR-hTERT cells showed a decrease in the percentage of S phase and an abrogation of G2/M cell cycle arrest (Additional file 1: Figure S1). There were no significant differences in VE-821 effect between the results with 3 Gy carbon ions and with 6 Gy X-rays, reflecting an RBE value of about 2 for carbon ions. Cellular growth data seem to indicate that VE-821 forced cells to divide into daughter cells (Fig. 2b).Fig. 2


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

Fujisawa H, Nakajima NI, Sunada S, Lee Y, Hirakawa H, Yajima H, Fujimori A, Uesaka M, Okayasu R - Radiat Oncol (2015)

VE-821 abrogated carbon ion-induced G2/M cell cycle arrest in tumor cells. HeLa and U2OS cells were pre-treated with 1 μM VE-821 or DMSO for 1 hour before irradiation, and were irradiated with 3 Gy of carbon ions or 6 Gy of X-rays. a Cells were harvested at 12 and 24 hours after irradiation and their cell cycle distributions were analyzed by flow cytometry. b The number of cells was counted immediately after and 1 day after irradiation. The relative cell number was calculated as follows: cell number after 1 day was divided by cell number immediately after irradiation. Error bars represent SEM of at least three independent experiments
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4554350&req=5

Fig2: VE-821 abrogated carbon ion-induced G2/M cell cycle arrest in tumor cells. HeLa and U2OS cells were pre-treated with 1 μM VE-821 or DMSO for 1 hour before irradiation, and were irradiated with 3 Gy of carbon ions or 6 Gy of X-rays. a Cells were harvested at 12 and 24 hours after irradiation and their cell cycle distributions were analyzed by flow cytometry. b The number of cells was counted immediately after and 1 day after irradiation. The relative cell number was calculated as follows: cell number after 1 day was divided by cell number immediately after irradiation. Error bars represent SEM of at least three independent experiments
Mentions: To investigate the effect of VE-821 on the cell cycle checkpoint after irradiation, we examined the cell cycle distribution by flow cytometer. Following carbon ion irradiation, all three cell lines showed significant G2/M checkpoint arrest at 12 hours after irradiation. However, the combination with VE-821 decreased the percentage of G2/M phase, indicating abrogation of G2/M cell cycle arrest. At 24 hours after irradiation, G2/M arrest continued in cells without the drug treatment, while cells with the combination treatment showed high percentages of G1 cells, the level of which was similar to, or even higher than non-irradiated control (Fig. 2a). Irradiated 1BR-hTERT cells showed a decrease in the percentage of S phase and an abrogation of G2/M cell cycle arrest (Additional file 1: Figure S1). There were no significant differences in VE-821 effect between the results with 3 Gy carbon ions and with 6 Gy X-rays, reflecting an RBE value of about 2 for carbon ions. Cellular growth data seem to indicate that VE-821 forced cells to divide into daughter cells (Fig. 2b).Fig. 2

Bottom Line: 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.ATR inhibitor would be an effective tumor radiosensitizer with carbon ion irradiation.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-8656, Japan. fujisawa@nuclear.jp.

ABSTRACT

Background: 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. 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.

Findings: HeLa, 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.

Conclusions: ATR inhibitor would be an effective tumor radiosensitizer with carbon ion irradiation.

No MeSH data available.


Related in: MedlinePlus