Tobacco use remains the leading preventable cause of death in the United States, and cigarette smoking is the primary cause of respiratory tract cancers. Exposure to tobacco smoke is widespread, with approximately 45 million current smokers, 46 million former smokers, and millions of environmental (second-hand) tobacco smoke-exposed nonsmokers in the United States (1, 2). Despite the profound causal role of cigarette smoking, it leads to
lung cancer in only 10% to 20% of smokers, and there are few clinical or genomic indicators of which smokers are at the highest risk (3-5). Some smokers develop cancer at an early age after relatively low cumulative smoke exposure, and some heavy smokers live into their 90s with no evidence of cancer. Therefore, the biological effect of cigarette smoke exposure on individuals varies, and an accurate biomarker of this variability in host response to tobacco smoke is needed.. Several studies involving cytologic and molecular techniques have established that ...