Functional analysis of the angiogenic potential of A549 cells after carbon-ion and photon irradiation

Radiation therapy is an integral part of the multi disciplinary therapy of lung cancer. Genetic changes and the hypoxic tumor microenvironment favour therapy resistance of tumor cells. Clinical studies suggest that particle irradiation using carbon ions may improve the therapy response of solid tumors compared to photon radiation [1,2]. Occurrence of therapy resistance is related to the secretion of growth and angiogenic factors that stabilize the vasculature and induce tumor vascularization [3]. Here, we applied the matrigel plug assay to compare the effects of biologically equivalent irradiation doses of carbon ions (11.4 MeV/u) and photons (6 MV-X) on angiogenesis induced by A549 cells. For this purpose, carbon ion-, and photon-irradiated as well as untreated A549 cells were injected as a suspension with matrigel into nude mice, respectively. Ten days later, newly formed blood vessels in the matrigel plugs were analyzed by CD31 staining of endothelial cells. These in vivo experiments were maintained under pathogen-free conditions and handled in accordance with the European Communities recommendations for animal experiment-ation. We observed an increase in the vessel number in matrigel plugs of photon irradiated (6 Gy) cells when compared to the plugs of carbon ion irradiated (2 Gy) or control cells (Figure 1).