Lung cancer is the most common cancer in the world. There are over 1 million cases of lung cancer annually, and the numbers are still increasing. Cigarette smoking causes 90% of lung cancer. In spite of progress in controlling cigarette smoking worldwide, there has been little change in smoking prevalence in the last decade. There are presently 1.1 billion smokers in the world. Ex-smokers are also at high risk for lung cancer. In 2000, there were 44.3 million ex-smokers in the U.S. Chemoprevention is a viable strategy to reduce lung cancer incidence and mortality. Our goal is to develop mixtures of chemopreventive agents which can inhibit lung cancer in smokers and ex-smokers. Based on consistent epidemiologic data that vegetable consumption protects against lung cancer, our overall hypothesis is that there are effective chemopreventive agents in vegetables. Together with our colleagues, we have developed naturally occurring isothiocyanates, their N-acetylcysteine conjugates, and myo-inositol (MI) as chemopreventive agents against lung cancer. Our studies demonstrate that these compounds, individually and in combination, are effective chemopreventive agents in a variety of animal models in which lung tumors are induced by the principal carcinogens in tobacco smoke. The goal of this proposal is to carry out translational research to further develop these agents for chemoprevention of lung cancer in smokers and ex-smokers.
The specific aims are: 1. Develop methods to quantify DNA adducts of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in induced sputum or bronchial biopsies from smokers. Our studies clearly demonstrate that the major mechanism by which 2-phenylethyl isothiocyanate (PEITC) inhibits lung tumor induction by NNK in rats and mice is inhibition of DNA pyridyloxobutylation in the lung. Clinical trials of PEITC or its N-acetylcysteine conjugate (PEITC-NAC) in smokers must address this specific question, but the required methodology is not currently available. 2. Further evaluate the efficacy against lung tumorigenesis of a mixture of PEITC-NAC and MI. These studies will be carried out in A/J mice treated with the tobacco smoke carcinogens benzo[a]pyrene (BaP) plus NNK or exposed to tobacco smoke. 3. Using mass spectrometry-based proteomics methods, identify proteins with differing levels of expression in the lungs of mice treated with BaP plus NNK and chemopreventive agents in Specific Aim 2. These studies are intended to uncover new mechanistic leads and biomarkers relevant to lung carcinogenesis and chemoprevention. The results of this project will provide a solid foundation for clinical trials of isothiocyanates, their N-acetylcysteine conjugates, and MI as chemopreventive agents against lung cancer, by establishing efficacy without toxicity, by further elucidating mechanisms, and by identifying practical biomarkers.
