CYCS and neoplasm: Mechanisms by which NO could promote tumor suppression or cell death include increased expression of p53, proteasomal degradation of anti-apoptotic proteins, release of Smac and cytochrome C, inhibition of ribonucleotide reductase, cytotoxic effects on tumor cells, cell-cycle arrest, induction of necrosis, inhibition of angiogenesis, and suppression of metastasis [24].