Cigarette smoking is strongly correlated with onset of lung cancer and cardiovascular diseases. About 60% of non-small cell lung carcinomas (NSCLCs) arise as a result of smoking. Nicotine and structurally related tobacco carcinogens like 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) have been found to induce the proliferation of cell lines derived from lung cancers. In addition, these agents could induce angiogenesis in vitro and in vivo and confer resistance to apoptosis. These events are mediated through the activation of the nicotinic acetylcholine receptors (nAChRs), and nAChRs have been detected in a variety of non-neuronal cells. Nicotine by itself is not known to induce oncogenesis;but based on its ability to induce tumor growth and angiogenesis, we propose to study how nicotine affects the growth, progression and metastasis of non-small cell lung carcinomas. Our recent results show that the scaffolding protein ?-arrestin-1 plays a major role in mediating the proliferative signals of nAChRs and was necessary for activation of Src in response to nAChR stimulation. Further, nicotine stimulation of A549 cells led to changes in the expression of genes involved in epithelial-mesenchymal transition (EMT). Recent studies have shown that ?-arrestin-1 plays a significant role in the metastasis of colorectal cancers. Given this background, we will assess the role of ?-arrestin-1 and Src in nicotine-induced cell proliferation, tumor cell invasion, metastasis and angiogenesis. It has been reported that ?-arrestin-1 translocates to the nucleus in response to G-protein coupled receptor signaling and activates multiple promoters;we find a similar nuclear translocation upon nicotine stimulation. Our preliminary results show that nAChR stimulation of non-small cell lung carcinoma cells leads to transcriptional activation of promoters involved in proliferation and EMT;we will assess the contribution of ?-arrestin-1 to this process. Based on our finding that nicotine can promote the growth of non-small cell lung tumors in mice, we will examine whether nicotine promotes tumor progression and metastasis in three different mouse models. Underlying mechanisms facilitating these processes will be elucidated, including the contribution of ?-arrestin-1 and Src in nicotine-induced tumor metastasis. Since a majority of non-small cell lung carcinomas correlate with exposure to tobacco smoke, these studies will throw light on the molecular mechanisms by which nicotine affects the growth and progression of lung cancers.
Exposure to tobacco smoke is highly correlated with onset of lung cancer. Though it is the direct effect of tobacco carcinogens that initiate tumor formation, exposure to nicotine might facilitate the growth and progression of tumors already formed. This is especially relevant since many smokers use nicotine supplements to quit smoking. The studies proposed in this application will elucidate the mechanisms by which nicotine induces cell proliferation, tumor growth and spread, as well as formation of new blood vessels. These studies can be expected to lead to the development of novel agents to combat cancer.
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