Ro90-7501 Is Identified As a Radiosensitizer By High Throughput Screening

Abstract

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, however, they have had only limited success in clinic. High throughput screening (HTS) is a popular method to identify candidate compounds from a large number of compounds for drug discovery, and have not been fully validated to study new radiosensitizers. The purpose of this study was to evaluate the efficacy of HTS for identifying radiosensitizers targeting hypoxic cancer cells. We performed cell-based HTS by using 384 well plates and 1280 compounds. After exposing compounds to HeLa cells, gamma-irradiation of 8 Gy was delivered in normoxia and hypoxia and incubated for 4 days. To identify candidate compounds, cell counting was performed by MTS assay. Radiosensitizing effects of these compounds were validated by clonogenic survival assay and in vivo tumor regression using female BALB/c nude mice. We performed in vitro experiments under both normoxic and hypoxic conditions. We performed HTS and identified 22 compounds as candidates. Among them, Ro90-7501 is known as an inhibitor of amyloid β42 fibril assembly and have not been reported as a radiosensitizer. Clonogenic survival assay showed significant radiosensitizing effects of Ro90-7501 not only in normoxia but also hypoxia. Tumor regression assay revealed that a significant radiosensitizing effect of Ro90-7501 with no apparent side effects. In conclusion, we identified Ro90-7501 as a novel radiosensitizer by HTS. HTS is a possible method for identifying clinically usable radiosensitizers.