*2.4. Colony Formation Assay*

The long-term survival assay was carried out by seeding 250 cells/well to 15.000 cells/well in a 6-well plate and irradiation at 0, 2, 4 and 6 Gy [11,21]. The plates were left to grow for 10 days into single colonies before they were fixed in 3.7% Formaldehyde (in PBS) and 70% Ethanol. Colonies were stained with 0.05% Coomassie Brilliant Blue for 1.5–3 h. Colonies (≥50 cells) were counted at fivefold magnification under the microscope.
