Nicotine induces cell proliferation, invasion and epithelial‐mesenchymal transition in a variety of human cancer cell lines

Abstract

Cigarette smoking is strongly correlated with the onset of nonsmall cell lung cancer (NSCLC). Nicotine, an active component of cigarettes, has been found to induce proliferation of lung cancer cell lines. In addition, nicotine can induce angiogenesis and confer resistance to apoptosis. All these events are mediated through the nicotinic acetylcholine receptors (nAChRs) on lung cancer cells. In this study, we demonstrate that nicotine can promote anchorage-independent growth in NSCLCs. In addition, nicotine also induces morphological changes characteristic of a migratory, invasive phenotype in NSCLCs on collagen gel. These morphological changes were similar to those induced by the promigratory growth factor VEGF. The proinvasive effects of nicotine were mediated by a7-nAChRs on NSCLCs. RT-PCR analysis showed that the a7-nAChRs were also expressed on human breast cancer and pancreatic cancer cell lines. Nicotine was found to promote proliferation and invasion in human breast cancer. The proinvasive effects of nicotine were mediated via a nAChR, Src and calcium-dependent signaling pathway in breast cancer cells. In a similar fashion, nicotine could also induce proliferation and invasion of Aspc1 pancreatic cancer cells. Most importantly, nicotine could induce changes in gene expression consistent with epithelial to mesenchymal transition (EMT), characterized by reduction of epithelial markers like E-cadherin expression, ZO-1 staining and concomitant increase in levels of mesenchymal proteins like vimentin and fibronectin in human breast and lung cancer cells. Therefore, it is probable that the ability of nicotine to induce invasion and EMT may contribute to the progression of breast and lung cancers. ' 2008 Wiley-Liss, Inc.Key words: lung cancer; nicotine; epithelial-mesenchymal transition; tumor progression; metastasis Cigarette smoke is the strongest documented risk factor for the development of lung cancer, accounting for about 157,000 deaths every year in the US. 1 A significant proportion of nonsmall cell lung cancer (NSCLC) cases are detected only in the advanced stage after the onset of metastasis, leading to a remarkably low 5-year survival rate (about 15%) in patients. 1 Tobacco-derived carcinogens like 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N 0 -nitrosonornicotine (NNN) are known to form DNA adducts, mutating vital growth regulatory genes like p53 and Ras, initiating oncogenesis. [2][3][4] In addition, several lines of evidence indicate that cigarette smoking correlates with increased metastasis of lung, pancreatic, breast and bladder cancers. [5][6][7] Although cigarette smoke is a complex mixture of over 4,000 compounds, nicotine has been shown the major addictive component of cigarettes. 8-10 Nicotine, while not carcinogenic by itself, has been shown to induce proliferation and angiogenesis in several experimental models 11-14 ; these effects occurred at concentrations normally found in the blood stream of smokers (10 28 -10 27 M). 12 These levels can vary greatly in smokers, and uri...

Flavonoid components in Scutellaria baicalensis inhibit nicotine-induced proliferation, metastasis and lung cancer-associated inflammation in vitro

“…Exposure of nicotine promotes the invasive and migratory ability of lung cancer cells and transplanted tumor in a mouse model (13,14). In this study, we also found similar effect of nicotine on A549 and H1299 cells; in addition, our results demonstrated that all flavones in Scutellaria inhibited nicotine-induced invasion in both cell lines and migration in A549 cells, and only baicalein suppressed nicotine-induced migration in H1299 cells.…”

“…carcinoma cells and epithelial-mesenchymal transition (EMT) in lung cancer cells (13,19). Thus, though nicotine itself cannot provoke cancer, it contributes to lung cancer progression already initiated through diverse processes.…”

“…Bax is an essential component in the nicotine survival signaling pathway, through activating PI3K/AKT that phosphorylates and inactivates the pro-apoptotic function of Bax (12). In addition, nicotine facilitates invasion and metastasis of lung cancer (13,14). Matrix metalloproteinases (MMPs) have long been linked with cancer cell invasion and metastasis (15).…”

ID1 Facilitates the Growth and Metastasis of Non-Small Cell Lung Cancer in Response to Nicotinic Acetylcholine Receptor and Epidermal Growth Factor Receptor Signaling

“…Several studies have shown that the decrease in E-cadherin and ␤-catenin with a concurrent increase in fibronectin and vimentin levels is one of the hallmarks of epithelial-mesenchymal transition in lung cancer cells (24). Earlier studies from our lab showed that nicotine induces changes consistent with EMT such as upregulation of mesenchymal proteins like vimentin and fibronectin (9). In the present study, we observed strong positive correlations of ID1 with mesenchymal markers vimentin and fibronectin and also with the ␣7 subunit of nAChR in human tumor samples.…”

“…EMT-like changes in an ␣7 receptor-and Src-dependent manner (9). Nicotine can diminish the expression of epithelial markers such as E-cadherin and ␤-catenin and upregulate mesenchymal proteins like fibronectin and vimentin in multiple cell lines, indicative of increased cell motility.…”