Abstract
Angiogenesis is essential for solid tumor growth and is comprised of multiple steps including the migration, invasion, and cell proliferation of vascular endothelial cells. Although radiotherapy is an important cancer treatment modality, the effects of ionizing radiation(IR) on tumor angiogenesis remain unclear; different groups of researchers have reported that IR either inhibits or activates angiogenesis. In this study, we found that IR(8Gy) induced a high frequency (-90%) senescence-like phenotype rather than apoptosis in exponentially growing endothelial cells. Thus, we investigated the angiogenic activity of such surviving senescent cells to determine the effects of irradiation on angiogenesis. Our results showed that senescence-like endothelial cells were growth-inhibited, which could be a major cause of angiogenic inhibition. Furthermore, other angiogenic processes -such as invasion- were also significantly inhibited. In conclusion, we have implicated the senescence-like phenotype of endothelial cells as a possible mechanism for IR-induced inhibition of angiogenesis.
