Abstract 5271: Nicotinic acetylcholine receptors and EGF induce c-Kit ligand/Stem Cell Factor (SCF) in a β-arrestin-1 and E2F1 dependent manner in NSCLC .
Authors: Perumal Deepak , Pillai Smitha , Chellappan Srikumar 
Published: August 2014

Abstract
β-arrestin-1 (ARRB1), a scaffolding protein involved in the termination or desensitization of signals arising from activated G-protein-coupled receptors (GPCRs) has been shown to play a role in invasion and proliferation of many cancers, including nicotine-induced proliferation of human non-small cell lung cancers (NSCLCs). In this study, we carried out microarray analysis of cells lacking β-arrestin-1 which have been rendered quiescent and subsequently stimulated with nicotine or EGF. Nicotine induced and β-arrestin-1 dependent genes from the microarray data were analyzed. We identified 296 genes that were upregulated and 208 that were downregulated by nicotine in a β-arrestin-1 dependent fashion. The functional pathway analysis tool, MetaCoreTM (Genego, MI, USA) was used to obtain curated molecular interactions related to the above selected genes. We selected top 10 genes from both up and down regulated list for prognosis prediction. Prognostic prediction was carried out using a subset of NCI Director's Challenge Set. Kaplan-Meier analyses for 5 year as well as overall survival showed significance for 4 genes namely COL4A4, NFASC, SCF and ZNF137 by log-rank test. We also examined whether the expression of these gens correlated with smoking; it was found that SCF strongly differentiated smokers from non-smokers implying an important role of this gene in lung carcinogenesis induced by smoking.
Stem cell factor (SCF) is the ligand of the c-Kit proto-oncogene product. It is a major human cytokine for the self-renewal, proliferation and differentiation of numerous embryonic, adult hematopoietic and primordial stem cells. Earlier reports show that uncontrolled activity of c-Kit contributes to formation of an array of human tumors. This unregulated activity of c-Kit may be due to overexpression or mutational activation suggesting that SCF-c-Kit signaling can be a potential target for cancer therapy. We elucidate the molecular mechanisms by which nicotine as well as EGF induces the expression of SCF in lung adenocarcinoma cell lines A549 and H1650. ChIP assays and transient transfection experiments showed that transcription factor E2F1 can positively regulate SCF expression at the transcriptional level; depletion of E2F1 or β-arrestin-1 prevented the nicotine-mediated induction of SCF. Given that the binding of SCF to c-Kit leads to activation of multiple downstream signaling pathways including Src, PI3-kinase and MAP/ERK pathways, our data suggest that the SCF/c-Kit pathway plays a central role in lung carcinogenesis, and may be a potential therapeutic target for combating NSCLC.
Citation Format: Deepak Perumal, Smitha Pillai, Srikumar Chellappan. Nicotinic acetylcholine receptors and EGF induce c-Kit ligand/Stem Cell Factor (SCF) in a β-arrestin-1 and E2F1 dependent manner in NSCLC . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5271. doi:10.1158/1538-7445.AM2013-5271