Abstract 5446: Nicotinic acetylcholine receptors activate TBK1 in a β-arrestin-1 dependent manner to promote NSCLC growth

Lung cancer is the leading cause of death in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of total lung cancer cases and demonstrates a strong association with tobacco use. Nicotine, an active component of tobacco smoke has been found to induce proliferation, invasion and epithelial-mesenchymal transition in NSCLC cell lines and promote the metastasis of NSCLC in mouse models. Nicotine induces cell proliferation and EMT utilizing a scaffolding protein, β-arrestin-1, which translocates to nucleus and associates with E2F1 transcription factor in response to nicotine stimulation. TBK1, a non-canonical IκB kinase has been shown to couple pathogen surveillance to induction of host defense mechanisms and contribute to inflammation as well as oncogenesis. These findings raise the possibility that TBK1 contributes to the onset as well as progression of NSCLCs through cell autonomous pathways in cancer cells, and indirectly through activating the inflammatory pathways in the tumor microenvironment. Since nicotinic acetylcholine receptor (nAChR) signaling is thought to augment Ras mediated cell proliferative pathways and confers resistance to apoptosis, attempts were made to assess whether TBK1 is induced by nAChR stimulation. Here we report that activation of nicotinic acetylcholine receptors leads to activation of TBK1 and β-arrestin-1 was required for this. Antagonists of alpha 7 subunit of nAChR such as bungarotoxin or inhibitor of α3/β2 and α4/β2 subunit DhβE abrogated nicotine induced TBK1 phosphorylation; further, depletion of β-arrestin-1 using siRNAs prevented the nicotine-mediated activation of TBK1. Inhibition of Src using dasatinib also could inhibit nicotine induced TBK1 phosphorylation. Interestingly, treatment of NSCLC cell lines with TBK1 inhibitor BX-795 resulted in significant inhibition of nicotine induced S phase entry as seen by BrdU incorporation assays. Cotransfection of TBK1 along with E2F1 significantly enhanced E2F1 mediated induction of E2F target promoters in transient transfection assays. Additionally, in an orthotopic lung cancer model in SCID-beige mice, implantation of A549-luciferase stable cells lacking β-arrestin-1 showed a decrease in primary tumor growth and also resulted in significantly lower levels of nicotine-induced metastasis when compared to controls. Mouse lung tissue sections with β-arrestin-1 depleted cells showed low levels of phosphorylated TBK-1 as compared to lung sections where control cells were implanted. Taken together, these data suggest that TBK1 contributes to nicotine induced growth and progression of NSCLC.

Citation Format: Smitha Pillai, Jonathan Nguyen, Eric Haura, Domenico Coppola, Srikumar Chellappan. Nicotinic acetylcholine receptors activate TBK1 in a β-arrestin-1 dependent manner to promote NSCLC growth. [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 5446. doi:10.1158/1538-7445.AM2013-5446

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

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

Abstract 1803: Transcriptional regulation of nicotinic acetylcholine receptors (nAChRs) by E2F family transcription factors in non-small cell lung cancer

Nicotine, the addictive component of cigarette smoke, has been shown to promote cell proliferation, migration, invasion, and angiogenesis in multiple cancer types. Earlier studies from our lab had shown that nicotine can promote the growth and metastasis of non-small cell lung carcinoma (NSCLC) in mouse models. While a broad range of nAChRs have been found to be expressed on NSCLC cell lines, nicotine-mediated proliferation, invasion, and migration are facilitated predominantly through the α7 subunit. Consistent with this, α7 nAChR levels are elevated in NSCLC in mice that were administered nicotine. Stimulation of α7 nAChR with nicotine has been reported to activate Src, resulting in inactivation of the retinoblastoma (Rb) tumor suppressor protein and enhancing E2F-mediated transcription. The Rb-E2F transcriptional regulation pathway is known to induce genes involved in cell cycle progression, angiogenesis, and metastasis implicating it in tumor survival and progression. Given this background, attempts were made to elucidate whether nAChR genes are regulated by the Rb-E2F pathway. Analysis of a 2000bp promoter region of the human α7 gene revealed the presence of multiple E2F binding sites. Transient transfection experiments showed α7 to be responsive to multiple E2Fs. E2F1 was found to associate with the α7 promoter via chromatin immunoprecipitation assays. Depletion of E2F genes via small interfering RNA demonstrated a differential regulation of α7 by E2F family members 1-5. These results raise the possibility that exposure to nicotine stimulates the α7 signaling cascade resulting in elevated E2F1-mediated activation of various proliferative promoters, including that of α7 itself in a positive feedback mechanism. In addition to the α7 nAChR, recent genome wide association studies (GWAS) have identified a susceptibility locus for human lung cancer at 15q25.1 which encodes for nAChR subunits α3 and α5. Promoter analysis has revealed that both α3 and α5 have multiple potential E2F binding sites, as well. Preliminary knock down of E2F family members via small interfering RNA has suggested these subunits may also be differentially regulated by the E2F family of transcription factors. Further studies are under way to elucidate the role of E2F in the regulation of nAChR α3 and α5, and how this impacts nicotine signaling as well as growth and progression of NSCLC.

Citation Format: Courtney M. Schaal, Smitha Pillai, Jackie L. Johnson, Srikumar Chellappan. Transcriptional regulation of nicotinic acetylcholine receptors (nAChRs) by E2F family transcription factors in non-small cell lung cancer. [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 1803. doi:10.1158/1538-7445.AM2013-1803

Abstract P2-04-02: Identification of genes associated with breast cancer micrometastatic disease in bone marrow using a human-in-mouse xenograft system

Disseminated tumor cells (DTCs) found in the bone marrow (BM) of breast cancer patients portend a poor prognosis and are thought to be the intermediaries in the metastatic process. Study of these cells has been limited due to their scarcity. To develop a clinically relevant model to characterize hese cells, we have employed a human in mouse (HIM) xenograft model for propagating, isolating, and molecularly characterizing DTCs. Human breast adenocarcinomas were prospectively collected from 5 patients and implanted into humanized NOD/SCID mouse mammary fat pads. BM was collected from the long bones at varying passages of the tumors and analyzed for human-specific gene expression by qRT-PCR and gene expression microarray. Human-specific gene expression of SNAI1, GSC, FOXC2, KRT19, and STAM2, presumably originating from disseminated tumor cells, was detectable in the BM of all mice that had developed metastatic disease to other solid organs, but was not detectable in xenotransplanted mice that did not develop metastatic disease. Comparative gene expression microarray analysis of the HIM primary tumor, the corresponding BM from mice with metastatic disease, and BM from control mice identified additional patterns of gene expression enriched in BM-associated DTCs which included several genes associated with epithelial-mesenchymal transition, aggressive clinical phenotype, and metastatic disease development in primary human tumors. We have found that BM DTCs can be detected using the HIM xenograft model and have identified unique patterns of gene expression associated with BM DTCs, which may provide further insight into the biology and therapeutic vulnerability of metastatic tumor cell populations in breast cancer patients.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-04-02.

Rhinofacial zygomycosis caused by conidiobolus coronatus

Fungal infections are common in a tropical country like India. Among the Zygomycosis infections, those caused by Mucorales are more prevalent. However, there exists another order of zygomycetes, the Entomophthorales, which rarely cause clinical disease. We report a rare cause of fungal infection of the maxillo-facial region and the oropharynx in a previously healthly male adult caused by Conidiobolus coronata of the order Entomophthorales to highlight the clinical presentation and treatment of this rare, chronic, indolent form of fungal infection.

Regulation of interlocking gene regulatory network subcircuits by a small molecule inhibitor of retinoblastoma protein (RB) phosphorylation: cancer cell expression of HLA-DR

The induction of the major histocompatibility (MHC), antigen-presenting class II molecules by interferon-gamma, in solid tumor cells, requires the retinoblastoma tumor suppressor protein (Rb). In the absence of Rb, a repressosome blocks the access of positive-acting, promoter binding proteins to the MHC class II promoter. However, a complete molecular linkage between Rb expression and the disassembly of the MHC class II repressosome has been lacking. By treating A549 lung carcinoma cells with a novel small molecule that prevents phosphorylation-mediated, Rb inactivation, we demonstrate that Rb represses the synthesis of an MHC class II repressosome component, YY1. The reduction in YY1 synthesis correlates with the advent of MHC class II inducibility; with loss of YY1 binding to the promoter of the HLA-DRA gene, the canonical human MHC class II gene; and with increased Rb binding to the YY1 promoter. These results support the concept that the Rb gene regulatory network (GRN) subcircuit that regulates cell proliferation is linked to a GRN subcircuit regulating a tumor cell immune function.

α7 nicotinic acetylcholine receptor subunit in angiogenesis and epithelial to mesenchymal transition

Cigarette smoking is strongly correlated with many diseases like cancer, cardiovascular disease and macular degeneration. Nicotine, the main active and addictive component of tobacco smoke has recently been shown to enhance angiogenesis in many experimental systems and animal models. The pro-angiogenic activity of nicotine is mediated by nicotinic acetylcholine receptors, particularly the alpha 7 subunit, that are expressed on a variety of non-neuronal cells including those in the vasculature such as endothelial cells and smooth muscle cells. The present review focuses on the role of α7nAChR in mediating the pro-angiogenic effects of nicotine and describes the molecular mechanisms involved in nicotine-induced angiogenesis as well as epithelial to mesenchymal transition. These observations on nicotine function highlight the therapeutic potential of α7nAChR agonists and antagonists for combating angiogenesis related diseases.

On the role of excitonic interactions in carotenoid-phthalocyanine dyads and implications for photosynthetic regulation

In two recent studies, energy transfer was reported in certain phthalocyanine-carotenoid dyads between the optically forbidden first excited state of carotenoids (Car S(1)) and phthalocyanines (Pcs) in the direction Pc → Car S(1) (Kloz et al., J Am Chem Soc 133:7007-7015, 2011) as well as in the direction Car S(1) → Pc (Liao et al., J Phys Chem A 115:4082-4091, 2011). In this article, we show that the extent of this energy transfer in both directions is closely correlated in these dyads. This correlation and the additional observation that Car S(1) is instantaneously populated after Pc excitation provides evidence that in these compounds excitonic interactions can occur. Besides pure energy transfer and electron transfer, this is the third type of tetrapyrrole-carotenoid interaction that has been shown to occur in these model compounds and that has previously been proposed as a photosynthetic regulation mechanism. We discuss the implications of these models for photosynthetic regulation. The findings are also discussed in the context of a model in which both electronic states are disordered and in which the strength of the electronic coupling determines whether energy transfer, excitonic coupling, or electron transfer occurs.

TNF-α-mediated proliferation of vascular smooth muscle cells involves Raf-1-mediated inactivation of Rb and transcription of E2F1-regulated genes

Atherosclerosis is characterized by hyperplastic neointima and an inflammatory response with cytokines such as TNFα. TNFα is a pleiotropic cytokine that mediates inflammatory, proliferative, cytostatic and cytotoxic effects in a variety of cell types, including endothelial cells and vascular smooth muscle cells (VSMCs). Interestingly, TNFα has been shown to play two very opposing roles in these cell types; it inhibits proliferation and induces apoptosis in endothelial cells, while it enhances the proliferation and migration of VSMCs. Here we show that TNFα is capable of stimulating proliferation of rat VSMCs as well as human VSMCs in a Raf-1/MAP K-dependent manner. TNFα could increase the expression of E2F-regulated proliferative cdc6, Thymidylate synthase (TS) and cdc25A genes in Aortic smooth muscle cells (AoSMC), as seen by real time PCR assays. There is an activation of the stress-induced kinase, JNK1, in VSMCs upon TNFα stimulation. TNFα was capable of inducing binding of the Raf-1 kinase to Rb, and treatment with the Rb-Raf-1 inhibitor, RRD-251, could prevent TNFα-induced S-phase entry in AoSMCs. In addition, inhibition of Raf-1 or Src kinases using pharmacologic inhibitors could also prevent S-phase entry, while inhibition of JNK was not as effective. These results suggest that inhibiting the Rb-Raf-1 interaction is a potential avenue to prevent VSMC proliferation associated with atherosclerosis.

P4-06-03: Multiplex Gene Expression of Disseminated Tumor Cells in the Bone Marrow of Breast Cancer Patients Identifies Novel Therapeutic Targets

Background: Disseminated tumor cells (DTCs) are detected in the bone marrow (BM) of up to 40% of breast cancer patients at the time of diagnosis and are an independent prognostic factor for recurrent disease. Present techniques for detection of DTC are often laborious, and insensitive due to the molecular heterogeneity of the DTCs. We have previously optimized and validated a novel, multiplexed gene expression technology platform, Nanostring nCounter™ (NC) which counts single molecules of RNA, for the multi-marker detection of DTCs in BM at a sensitivity of 1 cancer cell per 1 million nucleated BM cells. We now validate a 36 gene panel for the detection and molecular characterization of DTCs in BM.

Methods: Hybridization probes for 36 genes whose expression are associated with breast cancer, metastasis, and/or the cancer stem cell phenotype, and which exhibit no or low expression levels in normal bone marrow by qRT-PCR were developed for the NC assay. Total RNA was isolated from whole BM collected from the right and left iliac crest from breast cancer patients and healthy volunteers. 5 ug of RNA was analyzed, in duplicate with the NC assay. BM was scored positive for expression of an individual gene if expression in duplicate samples was 2 standard deviations above mean expression in a set of 11 independent normal BM samples.

Results: Bilateral BM samples were analyzed prior to any therapy from 20 patients: 8 developed metastatic disease within 2–48 months (mean of 23 months) after diagnosis, and 12 had no evidence of metastatic disease with 3–5 years follow-up. Overall, expression of at least one gene in the 36-gene multi-marker panel was detected in 17 patients (85%). There was excellent correlation between individual gene expression in both the right and left iliac crest samples from the same patient. Six of the 8 patients (75%) who developed metastatic disease had detectable expression of 1–3 genes. Two genes were commonly associated with metastatic disease development. 50% (3 of 6) of the patients who had detectable expression of EBB2 in their BM developed metastatic disease, although this did not correlate with expression in the corresponding primary tumor from the same patient. 80% (4 of5) of the patients who expressed the hedgehog pathway gene, Ptch1, in their BM developed metastatic disease. Conclusions: Our data demonstrate the feasibility of using a 36-plex NC assay to detect gene expression associated with BM DTCs in breast cancer patients. We found expression of 2 targetable genes associated with the development of metastatic disease, ERBB2 and Ptch1. ERBB2 expression in BM did not correlate with expression in the primary tumor. The molecular diversity of gene expression observed underscores the need for a multiplexed gene expression panel. Ongoing studies are evaluating the clinical utility of this assay to detect DTCs relative to existing techniques, for predicting relapse-free survival, molecular classification, and selecting appropriate targeted therapeutics based on BM DTC profiles in breast cancer patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-06-03.

Regulation of matrix metalloproteinase genes by E2F transcription factors: Rb-Raf-1 interaction as a novel target for metastatic disease

The retinoblastoma (Rb)-E2F transcriptional regulatory pathway plays a major role in cell-cycle regulation, but its role in invasion and metastasis is less well understood. We find that many genes involved in the invasion of cancer cells, such as matrix metalloproteinases (MMP), have potential E2F-binding sites in their promoters. E2F-binding sites were predicted on all 23 human MMP gene promoters, many of which harbored multiple E2F-binding sites. Studies presented here show that MMP genes such as MMP9, MMP14, and MMP15 which are overexpressed in non-small cell lung cancer, have multiple E2F-binding sites and are regulated by the Rb-E2F pathway. Chromatin immunoprecipitation assays showed the association of E2F1 with the MMP9, MMP14, and MMP15 promoters, and transient transfection experiments showed that these promoters are E2F responsive. Correspondingly, depletion of E2F family members by RNA interference techniques reduced the expression of these genes with a corresponding reduction in collagen degradation activity. Furthermore, activating Rb by inhibiting the interaction of Raf-1 with Rb by using the Rb-Raf-1 disruptor RRD-251 was sufficient to inhibit MMP transcription. This led to reduced invasion and migration of cancer cells in vitro and metastatic foci development in a tail vein lung metastasis model in mice. These results suggest that E2F transcription factors may play a role in promoting metastasis through regulation of MMP genes and that targeting the Rb-Raf-1 interaction is a promising approach for the treatment of metastatic disease.

Hypokalemic quadriparesis in Sjogren syndrome

We report a 58-year-old woman who presented with acute quadriparesis, bulbar weakness, atrial fibrillation, ventricular ectopics, and distal renal tubular acidosis with severe hypokalemia. She recovered completely on potassium and alkali supplementation. The patient also had hypergammaglobulinemia with probable primary Sjogren syndrome.

Electrostatic and capillary force directed tunable 3D binary micro- and nanoparticle assemblies on surfaces

We report a simple, rapid and cost-effective method based on evaporation induced assembly to grow 3D binary colloidal assemblies on a hydrophobic/hydrophilic substrate by simple drop casting. The evaporation of a mixed colloidal drop results in ring-like or uniform area deposition depending on the concentration of particles, and thus assembly occurs at the periphery of a ring or uniformly all over the drop area. Binary colloidal assemblies of different crystal structure are successfully prepared over a wide range of size ratios (γ = small/large) from 0.06 to 0.30 by tuning the γ of the micro- and nanoparticles used during assembly. The growth mechanism of 3D binary colloidal assemblies is investigated and it is found that electrostatic forces facilitate assembly formation until the end of the evaporation process, with capillary forces also playing a role. In addition, the effects of solvent type, humidity, and salt concentration on crystal formation and ordering behaviour are also examined. Furthermore, long range, highly ordered binary colloidal assemblies can be fabricated by the choice of a low conducting solvent combined with evaporation induced assembly.

Abstract 268: Differential regulation of MMP promoters by E2F transcription factors: Potential role of c-MYC and Id1

The retinoblastoma tumor suppressor, Rb, is the major negative regulator of E2F-1 transcription factor, and the Rb-E2F pathway is altered in most cancers. Further, many oncogenic mutations initiate tumors by targeting the Rb-E2F pathway. E2Fs regulate genes involved in a variety of biological processes, including angiogenesis, apoptosis, and differentiation, but it is unclear whether these molecules contribute to cancer cell invasion and metastasis. To investigate the role of E2F in metastasis, we analyzed the promoters of matrix metalloproteinase genes (MMPs), which are major contributors to the invasion and migration programs. We find that many MMP genes had potential E2F binding sites; we focused on MMP2, MMP9, MMP14, and MMP15 promoter, which have multiple E2F binding sites. Chip assays showed Rb, and E2Fs 1-5 could bind to the each MMP promoter. Transient transfection experiments with MMP promoter-luciferase constructs showed thatMMP9, MMP14, and MMP15-luc promoters were induced by E2Fs, whereas the MMP2 promoter was repressed by E2F1-5 in A549, and H1650 NSCLC cell lines. QRT-PCR showed that MMP2 was upregulated in A549 cells transfected with an siRNA targeting E2F1 and E2F3, whereas other MMPs were downregulated. To determine if MMP2 was repressed in an Rb-dependent manner, A549 cells stably expressing shRNA targeting Rb or a non-targeting control were transiently transfected with MMP2-luc construct and E2F1. In both cases, the MMP2-luc promoter was repressed by E2F1, suggesting that the repression is Rb-independent. Further, cells transfected with MMP2-luc promoter and E2F1 had less luciferase activity than cells transfected with MMP2 alone, independent of BRG-1, YY1, HDAC1, prohibitin-1, mSIN3a, or SUV39h1. Further, depletion of these co-repressors did not enhance MMP2 mRNA levels when compared to cells depleted of E2F1 alone. To determine if this repression is through binding site competition, we examined the effect of depleting transcription factors that have potential binding sites in the MMP2 promoter and were in close proximity to the E2F binding sites. We found that depletion of c-Myc and ID1 significantly enhanced MMP2 luciferase activity, and there was less repression from E2F1 in transient transfection experiments. These data suggest that E2F family members can repress the MMP2 promoter through mechanisms that may involve c-MYC and ID1.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 268. doi:10.1158/1538-7445.AM2011-268

Abstract 4993: Nicotine induced EMT and metastasis of human NSCLC : Role of beta-arrestin-1

Cigarette smoking is a major risk factor in the development of non-small cell lung cancer (NSCLC), which accounts for 80% of all lung cancers. Nicotine, an active component of tobacco smoke has been found to induce proliferation, invasion and epithelial-mesenchymal transition in NSCLC cell lines and promote the metastasis of NSCLC in mice. Nicotine induces cell proliferation utilizing a scaffolding protein, β-arrestin-1, which translocates to nucleus and associates with E2F1 transcription factor in response to nicotine stimulation. Here we demonstrate that mesenchymal markers such as vimentin and fibronectin are E2F1 regulated and β-arrestin-1 is involved in regulating nicotine induced expression of these genes. Vimentin and fibronectin promoters were E2F responsive and E2F1 could be detected on these promoters by chromatin immunoprecipitation (ChIP) assays. Depletion of β-arrestin-1 resulted in down-regulation of vimentin and fibronectin expression as well as inhibition of nicotine induced invasion of cells. Quantitative RT-PCR conducted on patient samples revealed a significant correlation between the levels of β-arrestin-1 and the expression of these genes. A microarray analysis conducted on nicotine stimulated parental A549 cells and those lacking β-arrestin-1 showed that about 290 genes were upregulated in the absence of β-arrestin-1, while 787 genes were downregulated. These included genes for transcription factors, growth factor receptors and signaling molecules. We further analyzed the global association of β-arrestin-1 in the genomic region upon nicotine stimulation by ChIP-sequencing and found that β-arrestin-1 is recruited on the promoters of many genes that regulate EMT such as ZEB2 (Zinc Finger E-box Binding Homeobox-2) as well as other regulatory pathways. ChIP assays conducted on NSCLC cell lines revealed the association of β-arrestin-1 on ZEB1 (Zinc Finger E-box Binding Homeobox-1) and ZEB2 promoters. Depletion of β-arrestin-1 in A549 cells resulted in the downregulation of ZEB1 and ZEB2. Additionally, in an orthotopic lung cancer model in SCID-beige mice, implantation of A549-luciferase stable cells lacking β-arrestin-1 showed a decrease in primary tumor growth and also resulted in significantly lower levels of nicotine-induced metastasis when compared to controls. Taken together, these data suggest that β-arrestin-1 contributes to nicotine induced progression and metastasis of NSCLC, especially in patients exposed to tobacco smoke. Further, β-arrestin-1 and its associated molecules might be targeted for the development of novel agents to combat NSCLC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4993. doi:10.1158/1538-7445.AM2011-4993