Long-term Objective: To establish contribution of nicotinic acetylcholine receptors (nAChRs) expressed in respiratory cells to mediating the oncogenic action of the nicotine-derived nitrosamines and identify antidotes to the tobacco-related carcinogenesis. Rationale: Nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) can specifically bind to nAChRs and alter growth of pulmonary cells. Our preliminary studies indicate that nicotinic antagonists can block binding of NNK and NNN to pulmonary cells and abolish effects of these nitrosamines on cell proliferation, apoptosis and anchorage-independent growth. Working Hypotheses: functional inactivation of nAChRs can: 1) abolish the oncogenic effects of NNK and NNN in in vitro and in vivo models of lung tumorigenesis; and 2) prevent alterations in the cholinergic receptor structure and function in respiratory cells.
Specific Aims : to determine: 1) the roles for lung nAChRs in mediating oncogenic effects of NNK and NNN in cultures of human bronchial epithelial BEP2D cells and A/J mice; and 2) alterations in the gene expression and ligand-binding abilities of cholinergic receptors in the exposed respiratory cells, and tumors in mice. Methodology: To assure accurate """"""""assignment"""""""" of the specific nAChR subtypes to a particular carcinogen, we will use overlapping approaches to abolish the effects of NNK and NNN. We will identify the nAChR- selective drug, small interfering RNA, or antisense oligonucleotides, that can abolish tumor-inducing activities of test nitrosamines. Significance: The results will provide crucial information for identifying the focus of future research toward elucidation of the role of specific nAChR subtypes in tobacco-related carcinogenesis and lung cancer chemoprevention. Description: The proposed research elaborates a novel paradigm of receptor-mediated action of tobacco carcinogens on target cells, and a well-substantiated hypothesis that an increased frequency of lung cancer in former smokers results from nicotine-induced alterations of binding to and signaling within the lung cells of the local hormone acetylcholine. The proposed studies will establish the role for each nAChR subtype involved in the process of malignant transformation of respiratory in response to the tobacco-specific nitrosamines. These findings will open a door for future mechanistic studies of the intracellular signaling pathways mediating the carcinogenic and tumor-promoting actions of tobacco nitrosamines. ? ? ?
