Figure 1.

Regorafenib radiosensitizes breast cancer cells but not normal cells as assessed by clonogenic cell survival assay. Regorafenib treatment shows a significant reduction in the surviving fraction compared with the DMSO controls in (A). MDA-MB-231 (B). SUM159PT cells while having no effect on (C). MCF 10a normal cells. (D). Dose enhancement factor (DEF) values calculated from the survival curves shown in panel A & B. DEF was calculated by dividing the radiation dose that produced 10 or 50% cell survival in control cells by that of the treated cells. Values shown are the means±SE of three independent experiments. *p ≤ .05.