title: Nicotine stimulates human lung cancer cell growth by inducing fibronectin expression.
abstract: The mechanisms by which tobacco promotes lung cancer remain incompletely understood. Herein, we report that nicotine, a major component of tobacco, promotes the proliferation of cultured non-small cell lung carcinoma (NSCLC) cells; this effect was most noticeable at 5 days. However, nicotine had no effect on apoptosis of NSCLC cells. In experiments designed to unveil the mechanisms for this effect, we found that nicotine also stimulated mRNA and protein expression of fibronectin. Fibronectin is a matrix glycoprotein that regulates important cellular processes (e.g., adhesion, proliferation, and differentiation) and is highly expressed in tobacco-related lung disorders. Of note, reagents against the integrin alpha5beta1 (antibodies, RGD peptides, alpha5 shRNA) blocked the mitogenic effects of nicotine. Thus, nicotine stimulated NSCLC cell proliferation indirectly via fibronectin induction. We then focused on the mechanisms responsible for nicotine-induced fibronectin expression in NSCLC cells and found that nicotine stimulated the surface expression of alpha7 nicotinic acetylcholine receptor (alpha7 nAChR), and that alpha-bungarotoxin, an inhibitor of alpha7 nAChR, abolished the nicotine-induced fibronectin response. The fibronectin-inducing effects of nicotine were associated with activation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3-K)/mammalian target of rapamycin (mTOR) signaling pathways, and were abrogated by inhibitors of ERK (PD98059), PI3-K (LY294002), and mTOR (rapamycin), but not by inhibitors of protein kinase (PK)C (calphostin C) and PKA (H89). These observations suggest that nicotine stimulates NSCLC proliferation through induction of fibronectin, and that these events are mediated through nAChR-mediated signals that include ERK and PI3-K/mTOR pathways. This work highlights the role of fibronectin and alpha5beta1 integrins as potential targets for anti-lung cancer therapies.
authors.affiliation: Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zheng
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Ritzenthaler
authors.forename: Jesse
authors.initials: J
authors.lastname: Roman
authors.forename: ShouWei
authors.initials: S
authors.lastname: Han
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005353:Fibronectins / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D008954:Models, Biological; D009538:Nicotine / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: D000906:Antibodies; C579167:Chrna7 protein, human; D005353:Fibronectins; D039081:Integrin alpha5beta1; D010455:Peptides; D034741:RNA, Small Interfering; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases