Tumor hypoxia correlates radioresistance and poor clinical outcomes after radiotherapy. Radiosensitizers have been studied for a long time especially to overcome the problem of hypoxic tumor cells. Until now, however, radiosensitizers for hypoxic tumors have had only limited success in clinic. High throughput screening is popular method to identify candidate compounds from a large number of compounds for drug discovery, but have not been established method to study new radiosensitizers. The aim of this study was to identify radiosensitizers targeting hypoxic cancer cells by high throughput screening and validate the efficacy of this method. We performed cell-based high throughput screening by using 384 well plates and 1280 compounds. After exposing compounds to HeLa cells, gamma-irradiation was delivered under hypoxic condition and incubated for 4 days. To identify candidate compounds, cell counting was performed by MTS assay. Then, radiosensitizing effect of these compounds was validated by clonogenic survival assay. We performed high throughput screening and identified 22 compounds as candidates. We selected Ro90-7501 and dicyclomine hydrochloride which were not reported as radiosensitizers. Clonogenic survival assay showed their significant radiosensitizing effect in hypoxic condition. In conclusion, we identified novel radiosensitizers by high throughput screening. This method may be useful for identifying radiosensitizers targeting hypoxic cancer cells.

Citation Format: Keisuke Tamari, Yuji Seo, Yutaka Takahashi, Osamu Suzuki, Fumiaki Isohashi, Yasuo Yoshioka, Kazuhiko Ogawa. A novel method to identify radiosensitizers targeting hypoxic cancer cells by high-throughput screening. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1667.