Therapeutics, Targets, and Chemical Biology Inhibiting DX2-p14/ARF Interaction Exerts Antitumor Effects in Lung Cancer and Delays Tumor Progression Ah-Young Oh 1 , Youn Sang Jung 1 , Jiseon Kim 2 , Jee-Hyun Lee 2 , Jung-Hyun Cho 1 , Ho-Young Chun 1 , Soyoung Park 1 , Hyunchul Park 3 , Sikeun Lim 3 , Nam-Chul Ha 4 , Jong Sook Park 5 , Choon-Sik Park 5 , Gyu-Yong Song 2 , and Bum-Joon Park 1 Abstract The aminoacyl tRNA synthetase complex-interacting multi- functional protein 2 (AIMP2) splice variant designated DX2 is induced by cigarette smoke carcinogens and is often detected in human lung cancer specimens. However, the function of DX2 in lung carcinogenesis is obscure. In this study, we found that DX2 expression was induced by oncogenes in human lung cancer tissues and cells. DX2 prevented oncogene-induced apoptosis and senescence and promoted drug resistance by directly bind- ing to and inhibiting p14/ARF. Through chemical screening, we identified SLCB050, a novel compound that blocks the interac- tion between DX2 and p14/ARF in vitro and in vivo. SLCB050 reduced the viability of human lung cancer cells, especially small cell lung cancer cells, in a p14/ARF-dependent manner. More- over, in a mouse model of K-Ras–driven lung tumorigenesis, ectopic expression of DX2 induced small cell and non–small cell lung cancers, both of which could be suppressed by SLCB050 treatment. Taken together, our findings show how DX2 pro- motes lung cancer progression and how its activity may be thwarted as a strategy to treat patients with lung cancers exhibit- ing elevated DX2 levels. Cancer Res; 76(16); 4791–804. Ó2016 AACR. Introduction Lung cancer is one of the most common human malignan- cies and is associated with extremely low survival rates (<10%; refs. 1, 2). However, the molecular mechanisms underlying the development of lung cancers remain unclear. Oncogenic muta- tions such as K-Ras or Her2/Neu and activation of AKT signaling by altering positive and negative regulators have been suggested to promote lung cancers (3–7). In fact, amplification of Her2/ Neu or oncogenic mutation in K-Ras is found in about 30% of lung cancer (8, 9), and loss of PTEN is also suggested as one of important genetic alternation (10). Given that oncogene acti- vation induces p53-induced apoptosis or senescence via p14/ ARF (11), there may be additional factors that disrupt the functional interaction between oncogenes and p14/ARF-p53 for cancer progression. Human lung cancers are divided into two groups, small cell lung cancer (SCLC) and non–small cell lung cancer (NSCLC), that are also divided into subgroups, adenocarcinoma, squamous cell lung carcinoma, and large-cell lung cancer. Among them, SCLC occupies 20% of lung cancer, is closely linked to smoking habit, and is very aggressive (12–14). Moreover, until now, we do not develop proper anticancer drug against SCLC. AIMP2 is previously known as p38/JTV-1 and cofactor of aminoacyl-tRNA synthetase complex (15, 16). Differentially from predicted role, housekeeping and scaffolding protein in essential enzyme complex, AIMP2 shows diverse cellular functions such as p53 activator and substrate of Parkin (16, 17). Moreover, AIMP2 knock out mouse is neonatal lethal because of defect in lung epithelial cell differentiation (15). Recently, exon 2 skipped alternative splicing variant of AIMP2, AIMP2-DX2 (DX2) has been reported to be highly expressed in human lung cancer (17, 18) and to be induced by benzo(a)pyrene (18), a major carcinogen associated with smoking (19). Consid- ering previous literatures, DX2 would be important factor of lung cancer initiation or progression, and how DX2 contributes to lung carcinogenesis has not been clearly demonstrated until now. That report inspired us to examine the role of DX2 in human lung cancer, in particular SCLC because of tight relationship with smoking. In this study, we checked the expression of DX2 in several kinds of human lung cancer cell lines and revealed that it was highly expressed in SCLC and stabilized by various oncogenic signaling including K-Ras or Her2/Neu-AKT activation. Moreover, DX2 blocked the oncogene-induced p14/ARF activation. Thus, we hypothesized that inhibition of DX2 would be one of plausible candidate for lung cancer treatment, in particular, SCLC. 1 Department of Molecular Biology, Pusan National University, Busan, Republic of Korea (South). 2 College of Pharmacy, Chungnam National University, Daejeon, Republic of Korea (South). 3 Forensic DNA Divi- sion, National Forensic Service, Wonju, Republic of Korea (South). 4 Program in Food Science and Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea (South). 5 Division of Allergy and Respiratory Medicine, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Gyeonggi Do, Republic of Korea (South). Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). A.-Y. Oh, Y.S. Jung, and J. Kim equally contributed to this article. Corresponding Authors: B.-J. Park, Pusan National University, 30 Jangjeon- dong, Geumjeong-gu, Busan 609-735, Republic of Korea (South). Phone: 82-51- 510-2220; Fax: 82-51-513-9258; E-mail: bjpark1219@pusan.ac.kr; and G.-Y. Song, gysong@cnu.ac.kr doi: 10.1158/0008-5472.CAN-15-1025 Ó2016 American Association for Cancer Research. Cancer Research www.aacrjournals.org 4791 on May 26, 2020. © 2016 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from Published OnlineFirst June 14, 2016; DOI: 10.1158/0008-5472.CAN-15-1025