Contributions of HR and NHEJ DSB repair to cellular survival following TMZ treatment. A,XRCC2+/+ cells (open circles) and XRCC2−/− cells (closed circles). B, Lig4+/+Rad54+/+ cells (open circles), Rad54−/− cells (closed triangles), Lig4−/−Rad54−/− cells (closed squares), Lig4−/− cells (closed circles). Each point represents the mean of at least three independent experiments; bars indicate the SD. C, relative D50 value (% compared to proficient cells).