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Promotion of Lung Carcinogenesis by Chronic Obstructive Pulmonary Disease–Like Airway Inflammation in a K-ras–Induced Mouse Model

Departments of ¹ Pulmonary Medicine, ⁴ Pathology, ⁵ Thoracic and Cardiovascular Surgery, and ⁶ Thoracic/Head and Neck Medical Oncology, the University of Texas M. D. Anderson Cancer Center, Houston, Texas; ² Department of Molecular and Cellular Biology, and ³ Department of Pathology, Baylor College of Medicine, Houston, Texas

Correspondence and requests for reprints should be addressed to Seyed Javad Moghaddam, M.D., Department of Pulmonary Medicine, the University of Texas M. D. Anderson Cancer Center, 2121 W. Holcombe Boulevard, Suite 703F, Houston, TX 77030. E-mail: smoghadd{at}mdanderson.org

Lung cancer is the leading cause of cancer deaths in the United States. In addition to genetic abnormalities induced by cigarette smoke, several epidemiologic studies have found that smokers with chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lungs, have an increased risk of lung cancer (1.3- to 4.9-fold) compared to smokers without COPD. This suggests a link between chronic airway inflammation and lung carcinogenesis, independent of tobacco smoke exposure. We studied this association by assaying the inflammatory impact of products of nontypeable Haemophilus influenzae, which colonizes the airways of patients with COPD, on lung cancer promotion in mice with an activated K-ras mutation in their airway epithelium. Two new mouse models of lung cancer were generated by crossing mice harboring the LSL–K-ras^G12D allele with mice containing Cre recombinase inserted into the Clara cell secretory protein (CCSP) locus, with or without the neomycin cassette excised (CCSP^Cre and CCSP^Cre-Neo, respectively). Lung lesions in CCSP^Cre-Neo/LSL–K-ras^G12D and CCSP^Cre/LSL–K-ras^G12D mice appeared at 4 and 1 month of age, respectively, and were classified as epithelial hyperplasia of the bronchioles, adenoma, and adenocarcinoma. Weekly exposure of CCSP^Cre/LSL–K-ras^G12D mice to aerosolized nontypeable Haemophilus influenzae lysate from age 6–14 weeks resulted in neutrophil/macrophage/CD8 T-cell–associated COPD-like airway inflammation, a 3.2-fold increase in lung surface tumor number (156 ± 9 versus 45 ± 7), and an increase in total lung tumor burden. We conclude that COPD-like airway inflammation promotes lung carcinogenesis in a background of a G12D-activated K-ras allele in airway secretory cells.

Key Words: K-ras • lung cancer • inflammation

CLINICAL RELEVANCE An association between chronic obstructive pulmonary disease (COPD) and lung cancer has been recognized clinically but not mechanistically. Our findings demonstrate a causal role for a COPD-like airway inflammation in lung cancer promotion, and provide a baseline for future clinical research.