Abstract 5063: Beta-arrestin-1 function in CAFs is necessary for enhancement of self-renewal of NSCLC stem-like cells
Authors: Raj Mohan Kumar Durai , Bora-Singhal Namrata , Chellappan Srikumar 
Published: August 2018

Cigarette smoking is a major risk factor in the genesis of non-small cell lung cancer (NSCLC), which accounts for 85% of all lung cancer. Nicotine, the addictive component of tobacco smoke, has been shown to induce proliferation, invasion and epithelial-mesenchymal transition (EMT) in NSCLC cells in vitro and promote growth and metastasis of NSCLCs in vivo. These nicotine-induced pro-tumorigenic functions are facilitated through activation of nicotinic acetylcholine receptors (nAChRs). The scaffolding protein β-arrestin-1 (ARRB1), which is involved in the desensitization of signals from activated G-protein-coupled receptors (GPCRs), plays a vital role in mediating the proliferative effects of nicotine through nAChR signaling. Nicotine induces the nuclear translocation of ARRB1 and increases the expression of E2F-regulated proliferative and survival genes to promote the growth and progression of NSCLCs. β-arrestin-1 is also necessary for nicotine-mediated induction of EMT; nicotine could induce a variety of mesenchymal genes including fibronectin, vimentin, ZEB1 and ZEB2 in a β-arrestin-1 dependent manner. Further, nicotine promotes stemness of NSCLCs by inducing SCF (Stem cell factor) in a β-arrestin-1 dependent manner. While all these studies from NSCLC derived cell lines and tumor tissues highlight the significance of β-arrestin-1 in cell-autonomous pro-tumorigenic functions, the role of β-arrestin-1 in NSCLC microenvironment is largely unknown. Cancer associated fibroblasts (CAFs) are shown to promote the self-renewal and proliferation of cancer stem cells in vitro and in vivo. In the present study we address whether β-arrestin-1 is necessary for CAFs to promote self-renewal of stem like cells from NSCLCs.

We generated a GFP expressing KRAS mutant NSCLC cell line A549 (A549-GFP). The side population (SP) cells from A549-GFP was isolated and used in 3D co-culture with lung CAFs in a stem cell selective medium. Our results show that CAFs can promote the self-renewal of SP cells, as measured by a sphere formation assay. Interestingly, depletion of β-arrestin-1 in CAFs significantly impaired the ability of CAFs to promote self-renewal and enhance sphere formation. Experiments are under way to assess the downstream mediators of β-arrestin-1 in CAFs that bring about the impairment in self renewal, which includes signaling molecules like TBK1 and a variety of cytokines. These studies are expected to shed new light on the mechanisms by which CAFs promote self-renewal and tumor growth, enabling identification of actionable pathways downstream of β-arrestin-1 that can potentially be targeted for NSCLC therapy.

Citation Format: Mohan Kumar Durai Raj, Namrata Bora-Singhal, Srikumar Chellappan. Beta-arrestin-1 function in CAFs is necessary for enhancement of self-renewal of NSCLC stem-like cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5063.