Fig. 3

Chemical inhibitor of RAD51, RI-1, inhibits RAD51 foci formation. a GSCs viability was measured using an MTS assay after 5 days of RI-1 treatment. IC₅₀ values were 22.3 μM and 19.7 μM respectively for GSC-14 and GSC-1. b Western blot analysis of RAD51 was performed on GSCs treated for 24 h with 10 μM RI-1 before IR. Total protein samples were extracted after 45 min and 24 h following 4Gy and 12Gy IR. β-actin was used as a loading control. Densitometric analysis of specific signals shows relative RAD51 protein expression levels normalized with β-actin and expressed as a percentage of control in GSC-6 and GSC-11 (n = 3) (*p < 0.05) (Image J software). c Cells were treated for 24 h with 10 μM of RI-1 before 12Gy IR and harvested at the indicated times. For each time point, the number of cells with RAD51 foci > 5 was scored and expressed as a percentage of the total number of nucleus scored. (*p < 0.05, **p < 0.01, ### p < 0.001, ns = no significant). d Representative images of GSC-6 and GSC-11 treated with RI-1. RAD51 foci (green) and nucleus (blue) are shown after 24 h following 12Gy exposure. These images were captured with the Axio Imager M2 fluorescent microscope (Carl Zeiss), scale bar: 2 μm