Separation of two sub-groups with different DNA content after treatment of T-47D breast cancer cells with low dose-rate irradiation and intermittent hypoxia

BackgroundPrevious studies have shown that combined treatment with internal ultra-low dose-rate irradiation selectively inactivated hypoxic T–47D breast cancer cells after three to five weeks of treatment. However, 2–3% of the hypoxic cells were found to survive and restart proliferation upon re-oxygenation.PurposeTo investigate the metastatic potential and characteristics of radiosensitivity of these surviving cells, named T – 47DS.Material and MethodsThe T – 47DS cells were grown in ambient air without irradiation. A cloning experiment identified two sub-groups with different DNA content (T-47DSC1 and T-47DSC2). Furthermore, radiosensitivity and presence of hyper-radiosensitivity (HRS) was measured by Co-60 challenge irradiation and relative migration was determined by scratch assays.ResultsThe two subpopulations of T – 47DS had different DNA content; one had abnormally high DNA content (T-47DSC1) and one had DNA content similar to wild-type T–47D cells (T-47DSC2). HRS was surprisingly present in cells ...