Treatment SW-620 HT-29 SNU-C4 G0/G1 S G2/M G0/G1 S G2/M G0/G1 S G2/M Control 67.2 ± 6.5 21.5 ± 3.9 12.9 ± 2.8 83.3 ± 8.9 6.2 ± 1.6 10.5 ± 2.4 60.1 ± 5.2 24.2 ± 2.9 16.3 ± 2.4 Gemcitabine IC50 45.5  ± 2.5 41.0 ± 2.9 10.6 ± 1.7 56.3 ± 4.1 31.4 ± 3.5 13.1 ± 2.3 50.2 ± 4.8 43.0 ± 5.2 7.6 ± 2.9 Radiation 5 Gy 27.7 ± 1.9 33.8 ± 5.0 41.7 ± 2.3 36.2 ± 3.4 28.4 ± 5.3 35.3 ± 6.3 55.4 ± 7.3 28.8 ± 2.3 16.9 ± 3.3 Gemcitabine IC50 + Radiation 5 Gy 43.1 ± 3.6* 44.7 ± 4.9* 12.1 ± 3.6 47.5 ± 1.5 35.7 ± 0.7 12.1 ± 7.1 52.1 ± 7.1 36.3 ± 0.7 10.8 ± 7.4

Table 2: Effect of gemcitabine at IC50, ionizing radiation at 5 Gy and gemcitabine (IC50) and ionizing radiation (5 Gy) combination on cell cycle distribution of SW620, HT-29 and SNU-C4 human colon cancer cells. Data were presented as mean ± standard deviation of percentage of cells of three independent experiments. *Different from irradiated cells (p<0.05).