KIT cITD induces ligand-independent resistance against radiation-induced apoptosis and recruitment of γ-H2AX and RAD51 repair factors to nuclear foci after DNA damage. (A) Cells were starved for 2 hours and exposed to 20 Gy γ-irradiation. Cells that were propidium iodide negative were counted as viable cells. Viability was calculated as a percentage of these cells over the total cell population. KL concentration was 100 ng/mL. Unirradiated and KL-starved Ba/F3/kit WT cells were used as control. Error bars indicate standard deviation. (B) After exposure to 20 Gy γ-irradiation and recovery for 2 hours, Ba/F3/kit WT and Ba/F3/kit cITD cells were fixed, permeabilized, and stained with primary antibodies directed against γ-H2AX (green) and RAD51 (red). Subpanels Bi and Bii represent Ba/F3/kit WT and Ba/F3/kit cITD cells, respectively, stained with anti-γ-H2AX, anti-RAD51, and composite before and after γ-irradiation. Micrograph images were visualized with a Leica HCX 40×/0.85 objective lens, digitally acquired through Leica Application Suite software, and processed with Adobe Photoshop 7.0 software (Adobe Systems, San Jose, CA).