Tumor suppressor silencing secondary to promoter hypermethylation plays a key role in the bronchial carcinogenesis process. The demethylating agent 5-azacytidine has demonstrated clinical efficacy in the treatment of the preleukemic condition myelodysplasia. Preliminary studies in our laboratory have demonstrated a 75-fold increase in the therapeutic index of 5-azacytidine when the intratracheal route of administration is used against orthotopic human lung cancer models in nude mice. In this application we propose to perform preclinical studies and the first human study of 5-azacytidine by inhalation. Our basic therapeutic strategy consists of exploiting the demethylaring properties of 5-azacytidine while avoiding its cytotoxic effects by using demethylating, non-cytotoxic doses, directly delivered to the target tissue, the bronchial epithelium, by inhalation over long periods of time. Before we initiate the proposed clinical Phase I study of inhaled 5-azacytidine we will determine the minimal effective dose as well as the lung toxicity of inhaled 5-azacytitine in a relevant murine model of lung premalignancy. These preclinical studies will allow us to rationally determine the starting dose that is likely to be both safe and therapeutic in man. We then propose to perform a feasibility and proof of principle Phase I study aimed at determining the optimal biological dose of inhaled 5-azacytidine using tumor suppressor gene reexpression in the target tissue as the pharmacodynamic endpoint. The specific aims are: 1. To determine the optimal dose of inhaled 5- azacytidine in mice exposed to tobacco carcinogens intratracheally (years 1 and 2). Endpoints will be: lung toxicity, efficacy in delaying lung tumor development, and tumor suppressor gene reexpression in the bronchial epithelium. 2. To perform a Phase I feasibility and proof of principle study of inhaled 5-azacytidine in patients with advanced NSCLC after failure of standard therapy (years 3-5). Endpoints will be: tolerability and toxicity with special emphasis on lung toxicity, tumor suppressor gene reexpression in the bronchial epithelium, and changes in methylation patterns in the bronchial epithelium. This proposal represents the first step of a long term program aimed at developing targeted epigenetic strategies for the treatment of advanced bronchial premalignancy and eventually the prevention of lung cancer. If successful, this strategy will provide clinical benefit to the very large population of individuals at risk of developing and dying from the most common cause of cancer-related death.