Background: To investigate the effects of ASMase mediated endothelial cell apoptosis in multiplehypofractionated irradiations in CT26 tumor bearing mice. Materials and
Methods: Thirty-five CT26 tumorbearing mice were subjected to single ionizing radiation (IR) of 0, 3, 6, 9, 12, 15, 18 Gy. Eight hours after IR,the mice were sacrificed and tumor tissues were used for CD31 immunohistochemistry staining, TUNEL andCD31 double staining, ASMase activity assay. Then 6 and 12 Gy were chosen for multiple hypofractionated IRexperiments according to the above results. Each time after IR, 5 mice were sacrificed and assayed as above.
Results: The ASMase activities were increased significantly after a single IR of 12 Gy or higher which wasaccompanied with remarkable increased endothelial cell apoptosis and decreased MVD. For 6 Gy which was nothigh enough to trigger ASMase activation, after 2 or more times of IR, the ASMase activities were significantlyincreased accompanied with remarkable increased endothelial cell apoptosis and decreased MVD. While for12 Gy, after 2 or more times of IR, the ASMase activities and endothelial cell apoptosis rates were maintainedwithout remarkable increase; however, the MVD was significantly decreased. What’s more, the cancer cellapoptosis rates were significantly increased after multiple IR for both 6 Gy and 12 Gy.
Conclusions: ASMasemediated endothelial cell apoptosis may play an important role in the process of multiple hypofractionated IRfor CT26 colorectal carcinoma.