Genetic ablation of inducible nitric oxide synthase decreases mouse lung tumorigenesis

• Published in: Cancer research (Chicago, Ill.) Vol. 62; no. 23; pp. 6850 - 6856
• Main Authors: KISLEY, Lori R, BARRETT, Bradley S, BAUER, Alison K, DWYER-NIELD, Lori D, BARTHEL, Benjamin, MEYER, Amy M, THOMPSON, David C, MALKINSON, Alvin M
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.12.2002
• Subjects: Animals; Biological and medical sciences; Butylated Hydroxytoluene; Carcinogens; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Endothelial Growth Factors - metabolism; Fundamental and applied biological sciences. Psychology; Immunohistochemistry; Intercellular Signaling Peptides and Proteins - metabolism; Lung - enzymology; Lung Neoplasms - chemically induced; Lung Neoplasms - enzymology; Lung Neoplasms - genetics; Lung Neoplasms - prevention & control; Lymphokines - metabolism; Macrophages, Alveolar - drug effects; Macrophages, Alveolar - immunology; Male; Mice; Mice, Knockout; Molecular and cellular biology; Nitric Oxide - metabolism; Nitric Oxide - physiology; Nitric Oxide Synthase - biosynthesis; Nitric Oxide Synthase - deficiency; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Urethane; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors; Lung disease; Respiratory disease; Enzyme; Rodentia; Inflammation; Malignant tumor; Carcinogenesis; Bronchopulmonary; Nitric-oxide synthase; Vertebrata; Mammalia; Mouse; Animal; Nitric oxide; Bronchus disease; Oxidoreductases; Mechanism of action
• ISSN: 0008-5472; 1538-7445

Inducible nitric oxide synthase (iNOS) content is elevated in human lung adenocarcinomas, and lung cancer patients exhale more nitric oxide (NO) than healthy individuals. The mechanism of this association of chronically elevated NO with tumorigenesis has not been defined. We investigated the role of iNOS in murine lung tumorigenesis, a model of human lung adenocarcinoma, using wild-type (+/+) and iNOS (-/-) mice. Genetic disruption of iNOS decreased urethane-induced lung tumor multiplicity by 80% (P < 0.0001). iNOS protein was expressed in lung tumors growing in wild-type mice and bronchiolar Clara cells isolated from normal mouse lungs, but was undetectable in whole lung extracts by immunoblotting. Because NO regulates vascular endothelial growth factor (VEGF) expression in other systems, we examined the effect of iNOS deficiency on VEGF protein concentration in mouse lung tumors. VEGF concentration was 54% lower in lung tumors isolated from iNOS (-/-) mice versus controls, implying that NO modulates angiogenesis in these tumors. Lung tumors also have elevated levels of cyclooxygenase (COX) -1 and COX-2 contents relative to normal lungs, but iNOS deficiency did not change COX expression in the tumors. Chronic inflammation predisposes mice to lung tumorigenesis; accordingly, we examined whether butylated hydroxytoluene-induced chronic lung inflammation was influenced by iNOS deficiency. Butylated hydroxytoluene-induced alveolar macrophage infiltration was unaffected by iNOS (-/-) status, suggesting that although NO is a critical mediator of mouse lung tumorigenesis, it is not essential in this model of lung inflammation. The substantial (80%) reduction in lung tumor multiplicity in iNOS (-/-) mice strongly supports examining iNOS-specific inhibitors as potential lung cancer chemopreventive agents.