CAT and neoplasm: Additionally, through endogenous modulation of the tumor hypoxia including normalization of tumor vessels 10, 11, intentional delivery of oxygen (O2) 12, knockdown of hypoxia-inducible factor-1α (HIF-1α) protein and downstream genes to relieve tumor invasion 13, or catalytic decomposition of endogenous H2O2 by catalase (CAT) 14, tumor hypoxia can also be relieved for sensitized tumor RT.