Figure 2. Irradiated TC71 Ewing sarcoma cells undergo apoptosis with a maximum sub-G₁ population at 20–25 Gy. TC71 cells were seeded in 60 mm² dishes at least 24 h prior to irradiation at the indicated dose, and the cells were in the log phase of growth at the time of irradiation. Twenty-four hours post-irradiation, the cells were fixed and stained with propidium iodide, and their DNA content was determined by flow cytometry. Cell cycle analysis was performed using ModFit software. (A) A dose-dependent increase in apoptotic cells was observed up to 20–25 Gy. Error bars denote the standard deviation; n = 2. (B) Representative, bright-field images of cells in culture 24 h post-irradiation at the indicated radiation dosage. The data shown are representative of results from 3 experiments.