IBS05.02 Functional Genomic Approaches to Identify Novel Therapeutic Targets in Lung Cancer

Abstract

Despite the discovery and availability of targeted therapies and immunotherapies, lung cancer remains the leading cause of cancer death worldwide. Importantly, most lung cancer patients are not eligible for targeted therapies because their tumors lack an actionable genomic alteration. Moreover, immunotherapy-based regimens fail to induce treatment responses in a substantial proportion of lung cancer patients (1-3). Therefore, the identification of novel therapeutic modalities remains critical to improving outcomes in lung cancer care. Lung cancer cells may harbor specific genomic or functional alterations that render them vulnerable to particular genetic perturbations (4,5). Discovery of these synthetic lethal interactions may provide opportunities to develop novel classes of therapeutics for this disease. Through systematic analysis of genome-scale loss-of-function datasets (6,7), we identify adenosine deaminase acting on RNA (ADAR or ADAR1) as an essential gene for the survival of a subset of lung cancer cell lines (8). ADAR1-dependent cell lines display increased expression of interferon-stimulated genes. Moreover, activation of type I interferon signaling in the context of ADAR1 deficiency can induce cell lethality in non-ADAR1-dependent cell lines. ADAR deletion causes activation of the cytoplasmic double-stranded RNA sensor, protein kinase R (PKR). Disruption of PKR signaling, through inactivation of PKR or overexpression of either a wild-type or catalytically inactive mutant version of ADAR1, partially rescues cell lethality after ADAR1 loss, suggesting that both catalytic and non-enzymatic functions of ADAR1 may contribute to preventing PKR-mediated cell lethality. Taken together, these data nominate ADAR1 as a potential therapeutic target in lung cancers displaying elevated interferon-stimulated gene expression and underscore the ability of functional genomic approaches to uncover novel genetic vulnerabilities in lung cancer. 1. Gandhi L, Rodriguez-Abreu D, Gadgeel S, Esteban E, Felip E, De Angelis F, et al. Pembrolizumab plus Chemotherapy in Metastatic Non-Small-Cell Lung Cancer. N Engl J Med 2018;378:2078-92 2. Paz-Ares L, Luft A, Vicente D, Tafreshi A, Gumus M, Mazieres J, et al. Pembrolizumab plus Chemotherapy for Squamous Non-Small-Cell Lung Cancer. N Engl J Med 2018;379:2040-51 3. Reck M, Rodriguez-Abreu D, Robinson AG, Hui R, Csoszi T, Fulop A, et al. Pembrolizumab versus Chemotherapy for PD-L1-Positive Non-Small-Cell Lung Cancer. N Engl J Med 2016;375:1823-33 4. Oike T, Ogiwara H, Tominaga Y, Ito K, Ando O, Tsuta K, et al. A synthetic lethality-based strategy to treat cancers harboring a genetic deficiency in the chromatin remodeling factor BRG1. Cancer Res 2013;73:5508-18 5. Zhou Z, Patel M, Ng N, Hsieh MH, Orth AP, Walker JR, et al. Identification of synthetic lethality of PRKDC in MYC-dependent human cancers by pooled shRNA screening. BMC Cancer 2014;14:944 6. Tsherniak A, Vazquez F, Montgomery PG, Weir BA, Kryukov G, Cowley GS, et al. Defining a Cancer Dependency Map. Cell 2017;170:564-76 e16 7. Aguirre AJ, Meyers RM, Weir BA, Vazquez F, Zhang CZ, Ben-David U, et al. Genomic Copy Number Dictates a Gene-Independent Cell Response to CRISPR/Cas9 Targeting. Cancer Discov 2016;6:914-29 8. Gannon HS, Zou T, Kiessling MK, Gao GF, Cai D, Choi PS, et al. Identification of ADAR1 adenosine deaminase dependency in a subset of cancer cells. Nat Commun 2018;9:5450 Functional genomics, Target discovery, Innate immune signaling