Figure 1: Survival fraction (SF) of the human colon cell lines SW-620 (image). HT-29 (image) and SNU-C4 (image) treated with gemcitabine (IC50) followed by ionizing radiation (5 Gy). They were quantified after 10 days in colonies containing at least 50 cells. The data were presented as percentage of cells relative to cells treated with irradiation. Data were plotted as the mean ± SD of three different experiments. *Significantly different from cells treated with radiation alone (p<0.05).