ABSTRACT
Radiotherapy has been focused mainly on killing cancer cells, and little attention has been paid to the process supporting tumor growth and metastasis, including the process of angiogenesis. To investigate the effects of carbon-ion irradiation on angiogenesis in lung cancer cells, we examined the expression of vascular endothelial growth factor and basic fibroblast growth factor in the tumor conditioned medium (TCM) of A549 cells exposed to carbon-ion or X-ray irradiation, as well as endothelial cell growth, invasion, and tube formation induced by TCM. No changes in vascular endothelial growth factor secretion were detected in the TCM of A549 cells exposed to carbon-ion irradiation at 2 or 4 Gy, whereas 1 Gy of irradiation significantly decreased vascular endothelial growth factor and basic fibroblast growth factor levels. Carbon-ion irradiation at 1 Gy inhibited endothelial cell invasion and tube formation. The TCM from A549 cells irradiated with X-ray promoted angiogenesis, whereas the TCM of A549 cells exposed to carbon-ion irradiation at 2 or 4 Gy had no effect. These findings suggest that carbon-ion irradiation at 1 Gy significantly suppressed the process of angiogenesis in vitro by inhibiting endothelial cell invasion and tube formation, which are related to vascular endothelial growth factor and basic fibroblast growth factor production.