title: Expression of endothelial and inducible nitric oxide synthase in benign and malignant lesions of the breast and measurement of nitric oxide using electron paramagnetic resonance spectroscopy.
abstract: BACKGROUND
  Nitric oxide (NO) is present in various human solid tumors and tumor cell lines, and it is believed that NO plays an important role in tumor growth. An increased NO concentration catalyzed by NO synthase (NOS) is cytotoxic and can promote apoptosis. The expression of endothelial NOS (e-NOS) and induced NOS (i-NOS) was examined in various breast tumors.
  
  
  METHODS
  Immunohistochemical staining with a monoclonal antibody (Ab) against e-NOS and a polyclonal Ab against i-NOS was performed on paraffin embedded tissues from 41 benign breast lesions, 9 in situ breast lesions, and 54 invasive breast lesions. Functionality was confirmed by detection of NO using spin-trapping electron paramagnetic resonance (EPR) spectroscopy.
  
  
  RESULTS
  e-NOS expression was found in 2 benign lesions (5%; 1 fibroadenoma and 1 proliferative mastopathy), in 5 in situ lesions (56%), and in 33 invasive lesions (61%). None of the benign lesions was positive for i-NOS, but 6 in situ lesions (67%) and 33 invasive lesions (61%) showed tumor cell staining. In particular, capillaries that were embedded in lymphocytic stroma showed a positive reaction for e-NOS. The functionality of NOS was demonstrated by direct NO formation using the EPR spin-trapping method. Tumors that were positive for e-NOS were observed more often in younger patients (P = 0.05). These tumors more frequently were highly differentiated or moderately differentiated and more often showed invasive ductal subtypes and a lower proliferation rate. Tumors that were positive for both e-NOS and i-NOS were more likely to be lymph node negative tumors. Both i-NOS-expressing lesions and e-NOS-expressing lesions showed strong coexpression (P = 0.00001).
  
  
  CONCLUSIONS
  NOS is detected predominantly in in situ lesions and invasive breast lesions but rarely in benign lesions. NOS is found more frequently in invasive carcinomas with low malignancy. Using the spin-trapping EPR method, this study demonstrates direct NO formation in human breast tumors for the first time.
authors.affiliation: Department of Gynecology and Obstetrics, University of Frankfurt, Frankfurt am Main, Germany. loibl@em.uni-frankfurt.de
authors.forename: Sibylle
authors.initials: S
authors.lastname: Loibl
authors.forename: Gunter
authors.initials: G
authors.lastname: von Minckwitz
authors.forename: Sonja
authors.initials: S
authors.lastname: Weber
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Sinn
authors.forename: Valérie B
authors.initials: VB
authors.lastname: Schini-Kerth
authors.forename: Irina
authors.initials: I
authors.lastname: Lobysheva
authors.forename: Françoise
authors.initials: F
authors.lastname: Nepveu
authors.forename: Georg
authors.initials: G
authors.lastname: Wolf
authors.forename: Klaus
authors.initials: K
authors.lastname: Strebhardt
authors.forename: Manfred
authors.initials: M
authors.lastname: Kaufmann
mesh_terms: D001941:Breast Diseases / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis* / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000032:analysis*; D052247:Nitric Oxide Synthase Type II
chemical_list: D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II