Funding is requested to support our ongoing studies toward identification of molecular mechanisms mediating oncogenic effects of tobacco nitrosamines on respiratory cells and development of novel anti-cancer therapies using nicotinic acetylcholine receptor (nAChR) ligands. Preliminary studies revealed an anti-tumor potential of both canonical and non-canonical ligands of the nAChRs expressed on the cell membrane of respiratory cells. These receptors play a role in the malignant transformation of BEP2D cells caused by pharmacologic doses of the tobacco-derived carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The NNK-transformed and lung cancer cells are highly sensitive to apoptosis induced by the novel cholinergic peptide SLURP-1 (secreted mammalian Ly-6/urokinase plasminogen activator receptor [uPAR]-related protein). Integrating structural and functional information about SLURP-1 vs. NNK actions on respiratory cells will facilitate a better understanding of the physiologic mechanism of tumor surveillance in lungs, and may lead to the development of novel methods of prevention and treatments of tobacco-related lung cancer. We will test the following working hypotheses: 1) SLURP-1 can prevent NNK-dependent transformation of respiratory cells in vitro and in vivo;2) cytoplasmic trapping of SLURP-1 results in altered expression of nAChRs on the plasma membrane of NNK-transformed BEP2D and lung cancer cells;3) SLURP-1 acts as a competitive nAChR antagonist with the 17 nAChR subtype mediating most of SLURP-1 effects;and 4) SLURP-1 interferes with the receptor-mediated signaling downstream of the nAChR subtype(s) ligated by NNK in normal and malignant human respiratory cells.
The Specific Aims will be to determine: 1) the role of SLURP-1 in the physiologic protection of respiratory cells from NNK carcinogenicity;2) the molecular mechanism of increased sensitivity of malignant respiratory cells to the apoptosis induced by SLURP-1;3) the nAChR subtype(s) mediating the pharmacologic activity of SLURP-1 and the mode of its action on the nAChRs expressed by respiratory cells;and 4) the signaling pathways downstream of the nAChRs ligated by SLURP-1 and NNK.
This proposal is focused on urgent problems of prevention and treatment of tobacco related lung cancer. It further develops a novel concept of receptor-mediated action of tobacco carcinogens and tumor promoters placing lung nicotinic acetylcholine receptors in the center of the pathophysiologic loop. The long-term objective is to develop pharmacologic chemoprevention of lung cancer in former smokers, and in people exposed to environmental tobacco smoke. The projected studies will ultimately establish the mechanism of anti-tumor activity of SLURP-1-an efficient, yet previously unknown, autocrine and paracrine ligand of lung nicotinic receptors capable of preventing tobacco nitrosamine-induced malignant transformation of BEP2D cells.
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