TP53 and neoplasm: On the other hand, NO directly kills tumor cells: (1) NO acts on mitochondrial oxidoreductase, and tumor cells die due to energy metabolism disorders [92]; (2) NO combines with superoxide anion in cells to generate nitrogen/oxygen free radicals, resulting in genotoxicity and DNA damage [93]; (3) NO inhibits cell proliferation by inhibiting protein synthesis [94]; (4) NO activates the expression of p53 and induces apoptosis of tumor cells [94]; and (5) NO inhibits platelet aggregation and tumor metastasis [95].