Figure 1. Correlation of radiosensitization in short-term syto60 and clonogenic assays.

A) Illustration of pilot set-up using a 24-well format and syto60 staining. IR, ionizing radiation; h, hours. B) Example of short-term radiosensitization using the PARP inhibitor olaparib in Calu-6 lung cancer cells. SRF_2Gy, short-term radiosensitization factor for 2 Gy (for definition, see Fig. S1J). +, treatment with 2 Gy IR or/and 1 µM olaparib; −, no treatment; n, effect of combined IR and olaparib normalized for the effect of olaparib alone. C) Example of radiosensitizing drug effect using clonogenic survival as endpoint. DEF_SF0.1, which is a standard descriptor of radiosensitization (14), represents the ratio of radiation doses required to achieve 0.1 clonogenic survival when given without and with drug. The drug + IR curve is corrected for the effect of drug alone. Statistical comparison by F-test. D) Illustration of the association of SRF_2Gy with DEF_SF0.1 values and previously reported radiosensitization of xenografts for various cell lines and targeted drugs (see text). E) Correlation of SRF_2Gy with DEF_SF0.1 for 25 cancer cell lines treated with up to 8 agents for a total of 63 comparisons. DEF_SF0.1 values were derived from full clonogenic survival curves (Supplementary Table 1A). For sensitivity and specificity calculations, cut-offs of ≥1.01 for SRF_2Gy and ≥1.04 for DEF_SF0.1 were used to define a positive effect. Statistical comparison by Spearman rank correlation. Rs, Spearman rank coefficient. F) Receiver operating characteristic (ROC) curve using the data shown in panel E. AUC, area under the curve.