Genetic ablation of inducible nitric oxide synthase decreases mouse lung tumorigenesis.
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.
Kisley
Lori R
LR
Department of Pharmaceutical Sciences, University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver 80262, USA.
Barrett
Bradley S
BS
Bauer
Alison K
AK
Dwyer-Nield
Lori D
LD
Barthel
Benjamin
B
Meyer
Amy M
AM
Thompson
David C
DC
Malkinson
Alvin M
AM
D000818:Animals; D002084:Butylated Hydroxytoluene; D002273:Carcinogens; D016228:Endothelial Growth Factors / Q000378:metabolism; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008168:Lung / Q000201:enzymology; D008175:Lung Neoplasms / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000517:prevention & control; D008222:Lymphokines / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D014520:Urethane; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D002273:Carcinogens; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D002084:Butylated Hydroxytoluene; D009569:Nitric Oxide; D014520:Urethane; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse