Human 8-oxoguanine DNA glycosylase 1 (hOGG1) plays a major role in the repair of 8-hydroxyguanine, one of the major forms of DNA damage generated by reactive oxygen species in tobacco smoke. If left unrepaired by hOGG1, 8-hydroxyguanine can produce G:C-to-T:A transversions. Recent studies have suggested that the hOGG1 Ser326Cys polymorphism is associated with both a decrease in enzyme activity and an increased risk of lung cancer. To define the interaction between tobacco carcinogens, hOGG1-mediated DNA repair and DNA damage, we examined the role of the hOGG1 Ser326Cys polymorphism in mutation of the p53 gene in non small cell lung cancer (NSCLC). Tumor and nonneoplastic DNA were collected from 141 cigarette smokers with NSCLC. Key words: lung cancer; hOGG1 polymorphism; p53 mutation; oxidative damage; epidemiology Tobacco use is the leading cause of preventable death in the United States. 1 One in 5 deaths and over 30% of cancer-related mortality are associated with tobacco use in this country. 1 Lung cancer is the leading cause of death among smokers and the most common cause of cancer-related death among both males and females in the United States and other developed countries. 2 In 2003, an estimated 171,900 new cases of primary lung cancer were diagnosed and an estimated 157,200 people died of this malignancy in the United States. 3 Epidemiologic studies have demonstrated that most cases of lung cancer are directly attributable to cigarette smoking. 2 Only 5-10% of all of the lung cancers occur in patients without a prior history of cigarette smoking. 2,4 Compared with nonsmokers, smokers have a 10-fold greater risk of dying from lung cancer, and in heavy smokers this risk increases to 15-to 25-fold. 5 Despite the strong association between cigarette smoking and lung cancer, only 11% of lifelong smokers will develop lung cancer. 6 Obviously, other factors must play a role in determining individual susceptibility to tobacco carcinogens.Individual susceptibility to exogenous exposures such as tobacco smoke varies with the presence of single nucleotide polymorphisms in a variety of critical genes. 7 Low penetrance susceptibility genes have common variants and often interact with environmental factors leading to sporadic cancer and contributing substantially to the population incidence of cancer. 8 -10 Polymorphisms in some of the genes involved in the metabolic activation [cytochrome P4501A1 (CYP1A1)] and detoxification [glutathione S-transferase M1 (GSTM1)] of tobacco carcinogens as well as in the repair of DNA damage (XRCC1, XPD, p53) have been associated with an increased risk of lung cancer. [11][12][13][14] Tobacco smoke is a complex mixture of over 55 carcinogens. 15 Cigarette smoking and specific tobacco carcinogens are associated with an increase in gene mutations in the lung, including those induced from oxidative damage. 4,16 -19 Repair of these DNA lesions is a complex process with specific types of DNA damage undergoing repair by specific multienzyme pathways. 9 Base excision repair (BER) is impo...