PTGS2 and colorectal cancer: NO exogenously provided by NO donors participates in cytotoxicity effects against colorectal cancer with the following mechanisms: (i) NO inhibits DNA synthesis; (ii) NO inhibits angiogenesis; (iii) NO inhibits EMT; (iv) NO reduces mutations of p53; (v) NO deactivates Cyclooxygenase-2 (COX-2); (vi) NO activates caspase family proteases; (vii) NO alters the expression of apoptosis-associated proteins, such as the Bcl-2 family; and (viii) NO decreases p21.