Nitric oxide synthase as a marker in colorectal carcinoma

Elevated inducible nitric oxide synthase (iNOS) activity has been found in 60 per cent of colon adenomas and 20 to 50 per cent of adenocarcinomas, We postulated that high levels of iNOS may increase the invasive and metastati c potential of colon carcinoma and could be indicative of survival potentia l. Data were reviewed for 52 patients with colorectal carcinoma diagnosed i n 1991 and 1992, Specimens were stained for iNOS and catalogued as low-acti vity staining (LAS) or high-activity staining (HAS) on the basis of visual evaluation by three pathologists, Thirty patients were LAS and 22 HAS. Age, sex, preoperative carcinoembryonic antigen, tumor and nodal status, and Am erican Joint Committee on Cancer staging were not different between groups. Forty-six per cent of the HAS group remained alive after 5 years versus 71 per cent in the LAS group. Survival was significantly lower and metastatic status significantly higher in the HAS group. Results indicated that iNOS activity may be a prognostic indicator of long-term survival potential afte r treatment for colon cancer. In addition results suggested that metastasis was greater in colon carcinoma specimens that maintain an activated iNOS a nd that these cells clinically react more aggressively. Conclusions are tem pered by the fact that results were based on a limited sample size.