Likewise, photon-induced angiogenesis in human lung adenocarcinoma cell line A549 was also reported by Girdhani S. et al. Their study demonstrated the angiogenesis via VEGF secretion and HIF1α expression was promoted by a sublethal dose of photon irradiation, while the same dose of high energy proton irradiation could be suppressed24. Here, HIF1A is linked to lung adenocarcinoma.