CASP9 and neoplasm: Although low concentration of NO mediates important physiological processes [48] high levels play crucial role in antimicrobial and antiviral responses [49] and can trigger oxidative stress, chronic inflammation [50], and nitrosylation, in particular S-nitrosylation of mitochondrial caspase-8, caspase-9, and Bcl-2 results in the inhibition of apoptosis of tumor cells [51].