Endothelial nitric oxide synthase: Correlation with histologic grade, lymph node status and estrogen receptor expression in human breast cancer

Nitric oxide is produced by several isoenzymes which are present in many di fferent tissues, We have recently reported the presence of inducible nitric oxide synthase in a breast cancer cell line. The purpose of this study was to examine the distribution of endothelial nitric oxide synthase (eNOS) in a series of human breast tumours. Immunohistochemical investigations demon strated immunolabelling of tumour cells with the primary antibody, bovine e ndothelial anti-nitric oxide synthase. Although there was no correlation be tween eNOS staining and tumour size, there was a significant (p < 0.005) ne gative correlation (rho = -0.65) between the percentage of tumour cells sta ining positive for eNOS and the histologic grade of the tumour; there was a lso a significant (p < 0.05) negative correlation (rho = -0.40) between the percentage of tumour cells staining positive for eNOS and the number of po sitive lymph nodes. A significant (p < 0.005) positive correlation (rho = 0 .63) between the percentage of tumour cells staining positive for eNOS and estrogen receptor (ER) expression by the tumour was also observed, In concl usion, our results demonstrate that eNOS is expressed by human breast tumou rs and that its presence negatively correlates with histologic grade and ly mph node status and positively correlates with ER expression. Copyright (C) 2000 S. Karger AG, Basel.