Inducible nitric oxide synthase (iNOS) produces nitric oxide, which has growth promoting activity in melanoma. A preliminary study of tumors from patients with Stage III melanoma who had received neo-adjuvant therapy revealed an association of tumor iNOS expression with shortened survival. The objective of the present study was to determine whether iNOS expression in tumors of newly diagnosed, untreated Stage III patients is predictive of survival. iNOS expression was examined by immunohistochemistry in tumors from 132 patients. The staining was evaluated for percentage of positive cells (Number score) and the intensity of staining (Intensity score). The association of iNOS expression with overall and disease-specific survival was tested in univariate and multivariate Cox proportional hazards regression models that included other known prognostic factors. Results of the univariate analysis demonstrated that the presence of iNOS in a patient's tumor, whether graded on the basis of Number or Intensity score, was associated with a significant increase in the hazard ratio of death from melanoma. These findings were corroborated by median survival data estimated from Kaplan Meier analysis. In the multivariate model including iNOS number or intensity, gender, age, number of lymph nodes, macroscopic disease and in-transit disease, only iNOS expression predicted survival. We conclude that a significant association exists between tumor iNOS expression and shortened survival in untreated Stage III melanoma patients. The ability of iNOS to predict outcomes for these patients may be independent of other known prognostic factors, providing a new molecular marker with significant potential for clinical utility.
Copyright 2006 Wiley-Liss, Inc.