In vivo radiosensitizing effect of combined use of olaparib and PI-103. Bioluminescence imaging of nude mice implanted with MDA-MB-435S cells transfected with pGL4 luciferase reporter vector and treated with indicated drugs alone (upper left) or prior to irradiation (IR) (upper right) and quantitation (lower panels). A marked decrease in tumor volume was induced with combined use of olaparib and PI-103, compared to radiation alone (P < 0.001 by t-test). Means of ROI values were significantly different between groups (P < 0.001). Y-axes show bioluminescence in photons/second. P < 0.001, ***.