Introduction Nicotine,a major component of cigarette smoke,by binding to nicotinic acetylcholine has been found to induce proliferation and apoptosis of lung cancer.Epidemiological cohort studies have indicated that α5-nAChR is highly associated with lung cancer risk and nicotine dependence.However,mechanisms through which α5- nAChRs may influence lung carcinogenesis are far clear.Here we aimed to study the roles of α5-nAChR on nicotine-induced cell proliferation and expressions of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor(VEGF)expression.