NOS2 and neoplasm: Since nitrosation of the protein in vitro as well as in tumor cells indicates that the enzyme is active and capable of carrying out DNA cleavage reactions and forming cleavable complexes with DNA in the presence of CPT, it would appear that the cysteine residue at 733 is not nitrosated/or reacted with chemically (PPNO) or intracellularly generated ·NO from iNOS during cytokine induction of HT-29 cells.