Browsing by Subject "Nicotine--Physiological effects."

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Open Access
Investigation of the effects of nicotine and levamisole on SW620 colon adenocarcinoma cells using a customized r-routine for automated microarray analysis
(2010) Üçal, Muammer
Nicotine, the addictive component of tobacco, shows proliferative and antiapoptotic activity in cancer cells. Levamisole, an antihelmintic, on the other hand, has been tested as an additive chemotherapeutic agent and in treatment of nephrotic syndrome. Nicotine and levamisole are both agonists of nicotinic acetylcholine receptors; effects of these two agents have not been studied in colon cancer transcriptome. In this study, nicotine and levamisole exposed SW620 colon cancer cells, at a dose of 1 μM for 7 days, were studied with respect to changes in expression using microarrays. For data analysis, a custom R-routine which makes extensive use of open source R-BioConductor Project and associated packages has been written; and it is composed of three modules: QualCont module performs quality controls supported with several visual
Open Access
Investigation of the effects of nicotine on the expression profile of SW620 colon adenocarcinoma cells using a functional genomics approach
(2009) Kaya, Onur
Colon cancer is the third most common form of cancer with approximately 655,000 deaths worldwide annually and the second principal cause of cancer-related death in the Western world. Studies focusing on genomic instability and cell culture in recent years have shown that there is a statistically significant link between tobacco smoking and colorectal cancer. Although nicotine is one of the most potent chemical in tobacco, it was not studied extensively in colorectal cancers. Nicotine works as an agonist of nicotinic acetylcholine receptors and modulates the intracellular calcium concentrations hence deregulating multiple signal transduction pathways (e.g., PI3K/AKT, MAPK, mTOR). It has been shown that nicotine accelerates cell proliferation while it increases cell migration, metastasis and angiogenesis, and inhibits apoptosis in lung and gastric cancers. The aim of this study was to give more insight into the association between nicotine and colon cancer by investigating the gene expression profiles of SW620 colon adenocarcinoma cells under 48h 1µM nicotine treatment at different serum levels to reflect molecular response to growth factor-induced and –depleted conditions (10% FBS or 0.1% FBS). We used multiple approaches including cell culture techniques, microarray technology, and gene-network analysis to assess the effects of nicotine on cell proliferation and transcriptome profile. Furthermore, the selected genes that are involved in cell cycle and apoptosis were used to confirm and evaluate the transcriptome analysis results with real time qRT-PCR and Western Blot techniques. In this project, our findings indicated that serum starvation of SW620 colon adenocarcinoma cell line resulted in decreased cell proliferation, which could be rescued by 1µM nicotine via deregulation of multiple pathways including cell cycle, apoptosis, Ca2+ signaling, and ribosomal protein expression. This study implicated that nicotine-, thus acetylcholine-mediated signaling may have an important role in tumor development and metastasis.
Open Access
Nicotine-modulated gene expression profiles in MCF7 breast cancer cell line and involvement of estrogen in CHRNA5 expression
(2009) Bıyık, Rümeysa
Breast cancer, highly heterogeneous in nature, has been classified into multiple molecular subtypes based on hormone receptor status and also possess variable genetic and environmental etiologies. Prognosis and therapy of breast cancer depends on the presence or absence of these molecular markers. Nicotine, the major psychoactive addictive component in tobacco smoke, has been associated with multiple cancers because of its ability to increase cell proliferation, migration, and angiogenesis, and to decrease apoptosis. Nicotine binds to cholinergic receptors made up of multiple subunits, one of which, the alpha 5 (CHRNA5) whose polymorphisms have recently been implicated in nicotine addiction and lung cancer as functional. Microarray datasets provide genomic and functional information on the whole transcriptome when exposed to a certain treatment or under different pathological conditions allowing for molecular classification. The association between nicotine use and breast cancer has been controversial and to our knowledge no high-throughput expression profiling of breast cancer cells exposed to nicotine exists in the literature. In the present study, we determined that 1 uM nicotine affects cell proliferation in MCF7 cells measured by MTT assay only under serum starvation (0.1% Serum) condition at days 5 or 7 but not earlier. Similarly, effects on the protein levels of selected molecular markers with roles in proliferation and/or apoptosis, i.e., CyclinE, bcl-xl, and p53 were affected under serum starved conditions in more pronounced ways. Effects of nicotine at the transcriptome level were studied in MCF7 cells when exposed to 1uM Nicotine using Affymetrix Human HGU133 plus 2 arrays under the 10% serum levels. Our findings indicated that nicotine affects multiple pathways including MAPK, focal adhesion, and apoptosis although the magnitude of changes was mild. Preliminary analyses performed under serumstarvation indicated that starvation resulted in drastic changes in MCF7 transcriptome, some of which can be reversed, by 1uM nicotine. CHRNA5 expression was highly modulated by serum levels. Multiple microarray datasets on breast cancer cell lines and primary tumors in GEO were re-analyzed to assess the dependency of CHRNA5 expression on estrogen. Our findings were: 1) CHRNA5 expression increased in the presence of estrogen in a dose- and time-dependent fashion; 2) CHRNA5 was found to be a likely secondary target of estrogen; 3) CHRNA5 expression was higher in ER negative and/or Grade 3 breast cancer patients, implicating CHRNA5 with prognosis; 4) DNA replication and cell cycle genes seemed to be highly correlated with CHRNA5 expression; 5) the coexpressed genes could predict ER and Grade status of primary tumors with high accuracies. In conclusion, cholinergic signaling as modulated by nicotine through acetylcholine receptors might have a role in breast cancer etiology. CHRNA5 represents a novel candidate for breast cancer diagnostic and prognostic studies.
Open Access
Smoking and nicotine alter UGT1A expression
(2011) Ölmezer, Gizem
The expression and activity of enzymes taking role in drug metabolism are important as in the case of phase II glucuronidation enzymes; namely UDPglucuronosyltransferases (UGTs). Previously, it has been identified that smoking upregulates the expression of UGT enzymes in oral mucosa. We asked whether smoking induces UGT1A expression in other tissues and re-analyzed publically available datasets run with samples from smokers and non-smokers. It was observed that UGT1A enzymes were overexpressed in several types of epithelial cells of smokers. 30% of nicotine metabolism is performed by UGT enzymes; however, whether UGT1A expression is modulated by nicotine, the addictive component of tobacco smoke, is not known. For this purpose, the expression levels of UGT1A isoforms were measured using Real-Time PCR in nicotine treated SW620 colorectal cancer cells. Our findings showed that nicotine’s effect on UGT1A expression was isoform specific; and the magnitude of modulation differed among isoforms. Furthermore, the upregulation of UGT1A enzymes could only be observed in serum-deprived SW620 cells. In summary, nicotine metabolism enzymes are regulated by both smoking in vivo and nicotine in vitro. Nevertheless, enhanced xenobiotic metabolism may result in chemoresistance, which is undesirable for cancer patients. Therefore, before drug therapy cancer patients might be analyzed in terms of their smoking status and UGT1A expression patterns.