FIGURE 1.

Direct and indirect effects of radiotherapy (RT) on cancer cells and on tumor hypoxia and oxygenation. Ionizing radiations can directly hit DNA or participate to water radiolysis generating Reactive Oxygen Species (ROS) that in turn hit DNA. The RT-induced cancer cell death of the most oxygenated cells leads to the reoxygenation of hypoxic cells. Reoxygenation favors ROS production, which in turn stabilizes Hypoxia Inducible Factor-1 (HIF-1). HIF-1 target genes are implicated in several indicated processes.