Figure 1. Cell viability of the three gastric cancer cell lines (MKN74, MKN45, and NUGC4) was assessed following incubation for 96 h with or without irradiation to maintain constant cell culture conditions. The viability of each of the 3 cell lines was significantly lower than that of the control group (*P < 0.05) (A). Apoptosis was determined by flow cytometry and the total apoptosis rate was calculated. The total apoptosis rate induced by irradiation was significantly increased in each of the three gastric cancer cell lines as compared with the control (*P < 0.05) (representative data was shown in [B]). Caspase-3 assay was performed and the activity of caspase-3 was increased significantly in all 3 irradiated gastric cancer cell lines (P < 0.05) (C). Experiments were performed at least 3 times.