Presentation High-throughput Screening of Radioprotectors/sensitizers Using Thymocytes

Sakamoto, Yoshimitsu  ,  Sekine, Emiko  ,  Ma, Liqiu  ,  Sato, Katsutoshi  ,  Fujisaki, Shingo  ,  Ken-ichiro, Matsumoto  ,  Nakanishi, Ikuo  ,  Shimokawa, Takashi

2015-05-27
Description
Radiation therapy(RT) using high-energy radiation such as X-ray and charged particles, is one of the common treatments for cancer. During the past few decades, RT has been evolved in response to a change in technologies. However it still has the potential to improve clinical outcomes, including the patient quality of life after RT, by using biological and chemical approaches.We have been interested in combination drugs for RT, especially radioprotectors (RPs) and radiosensitizers (RSs). A RP is defined to protect normal tissues around the treated tumor from irradiation to prevent adverse reactions, such as second primary cancer. However, only Amifostine has been approved by the FDA to protect normal tissues from radiation during RT. RSs are applied to make cancer cells more sensitive to RT. A large number of chemical compounds, which show radioprotective/sensitize effects by chemical analysis, is known, but only a part of them were assessed for their effects on cell lines or animal models. A reason for this gap is that conventional methods have some bottlenecks to achieve high-throughput screening, due to requirement of relatively large amount of compounds, higher cost and complexity of the methods. To accelerate drug development for RPs and RSs, we invented a novel high-throughput method for screening lots of candidates. This method utilizes the radiation-induced shrinkage of thymocytes (TCs), which is well known as a major morphological change connected with apoptosis, to evaluate protective- or sensitize-effect of tested chemicals against radiation. The TCs were pretreated with candidates followed by 2 Gy X-irradiation. After irradiation, these cells were incubated for 4 h and then the cell size of TCs were immediately measured on a flow cytometer. The protective effect of some natural antioxidants against radiation-induced apoptosis in the rat TCs, as well as their toxicities without X-irradiation, was successfully evaluated using this method. In addition, to reduce assay volume and to adjust high-contents analysis, we further developed the method by using fluorescence dyes with the imaging cytometer. This method is able to lower the assay volume and assay time to be less than 1/5 compared with the previous method.Here, I will present our recent results to evaluate candidate compounds by using the two methods.
15th International Congress of Radiation Research (ICRR 2015)

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