Expression of inducible nitric oxide synthase in colorectal cancer and itsassociation with prognosis

Background: The expression of inducible nitric oxide synthase (iNOS) has be en reported to be altered in a number of tumours, but its role in tumour bi ology is still unclear, Methods: iNOS was studied in a series of 157 colore ctal carcinoma patients and its relation to tumour grade, stage, cell cycle regulators, cell proliferation as well as survival was assessed. Results: iNOS intensity was moderate or intense in 37% of the tumours. iNOS intensit y and percentage of positive cells were higher in Dukes A and B tumours tha n in Dukes C and D tumours. and low iNOS expression intensity was related t o high histological grade. iNOS expression correlated positively with cell cycle regulators p21 and AP-2. There was also a high iNOS expression intens ity and high fraction of iNOS positive cells in tumours with a high amount of tumour infiltrating lymphocytes (TILs). The cancer related survival was significantly lower among patients with a low signal for iNOS and low iNOS percentage in tumour epithelium. In multivariate analysis iNOS was not an i ndependent prognostic factor. Conclusions: These results suggest that iNOS has a protective role in colorectal carcinogenesis. but further studies are required to establish the clinical significance of iNOS in colorectal canc er.