Figure 1: Survival fraction of human colon cancer cell lines SW-620 (image). HT-29 (image) and SNU-C4 (image) irradiated with 2, 5 or 10 Gy. They were quantified after 10 days in colonies containing at least 50 cells. Data were expressed as the percentage of the survival fractions of cells versus the different treatments and were plotted as the mean + SD of three different experiments. *Significantly different from control (p<0.05).