ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of X-rays on expression of caspase-3 and p53 protein in EL-4 cells and its implications in induction of apoptosis and polyploid cells.</p><p><b>METHODS</b>Mouse lymphoma cell line (EL-4 cells) was used. Fluorescent staining and flow cytometry analysis were employed for measurement of protein expression, apoptosis, cell cycle, and polyploid cells.</p><p><b>RESULTS</b>The expression of caspase-3 protein increased significantly at 8 h and 12 h, compared with that of sham-irradiated control (P<0.05, respectively) and the expression of p53 protein increased significantly at 2, 4, 8, 12, and 24 h, compared with that of sham-irradiated control (P<0.05-P<0.01) in EL-4 cells after 4.0 Gy X-irradiation. Apoptosis of EL-4 cells was increased significantly at 2, 4, 8, 12, 24, 48, and 72 h after 4.0 Gy exposure, compared with that of sham-irradiated control (P<0.05-P<0.001). G2 phase cells were increased significantly at 4, 8, 12, 24, 48, and 72 h (P<0.05-P<0.001). However, no marked change in the number of 8 C polyploid cells was found from 2 to 48 h after 4.0 Gy exposure.</p><p><b>CONCLUSION</b>The expressions of caspase-3 and p53 protein in EL-4 cells are induced by X-rays, which might play an important role in the induction of apoptosis, and the molecular pathway for polyploid formation might be p53-independent.</p>