Study on the radiation quality dependence of the bystander effect in radiation cancer treatment

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K16496
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Radiation science
• Research Institution: National Institutes for Quantum and Radiological Science and Technology
• Principal Investigator: Kobayashi Alisa 国立研究開発法人量子科学技術研究開発機構, 量子生命科学領域, 研究員(任常) (30773931)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 放射線誘発バイスタンダー効果 / ヒドロキシラジカル / がん細胞

Outline of Final Research Achievements

This study aimed to determine whether radiation-induced bystander effect is affected by radiation quality. We exposed A549 cells at low or high LET-like condition using thio-urea (TU) as a ・OH scavenger to mimic different radiation qualities of direct action/indirect action. Cells were exposed to X-rays, with (TU+) or without TU (TU-). After irradiation, cells were co-culture with non-irradiated bystander cells up to 24 hours. As a result, COX-2 expression in TU+ (high LET-like) irradiated cells were significantly suppressed compared to TU-. However, COX-2 was equally expressed in TU+ and TU- bystander cells. These results indicate that COX-2 expression pathway of bystander cells is modulated by radiation quality. Thus, we observed NF-kB phosphorylation which is one of upstream molecule of COX-2. We detected the NF-kB phosphorylation only in the TU+ bystander cells. Therefore, findings of this study indicate that bystander effect and its signaling pathways depend on radiation quality.

Free Research Field

放射線科学

Academic Significance and Societal Importance of the Research Achievements

放射線がん治療では様々な放射線が用いられており、其々の放射線が持つ特性（線質）を生かした治療がなされている。しかし、照射領域外の非照射細胞に対して照射細胞と類似した生物学的効果が現れる"放射線誘発バイスタンダー効果"が線質によって変わるのかは明らかになっていない。そこで本研究はバイスタンダー効果に線質依存性があるか評価した。その結果、バイスタンダー効果の発現機序は線質によって変化することを見出した。これは、用いる線質によって周囲の非照射細胞への影響が異なることを意味し、放射線がん治療における局所制御率等の向上の為には、バイスタンダー効果による影響も加味し、線質を決定する必要がある事を示した。