Human Cancer Biology Alpha-Smooth Muscle Actin (ACTA2) Is Required for Metastatic Potential of Human Lung Adenocarcinoma

Purpose: Metastatic relapse of primary lung cancer leads to therapeutic resistance and unfavorable clinical prognosis; therefore, identification of key molecules associated with metastatic conversion has significant clinical implications. We previously identified a link between early brain metastasis of lung adenocarcinoma and amplification of the a-smooth muscle actin (ACTA2) gene. The aim of present study was to investigate the prognostic and functional significance of ACTA2 expression in cancer cells for the metastatic potential of lung adenocarcinomas. Experimental Design: ACTA2 expression was analyzed in tumor cells from 263 patients with primary lung adenocarcinomas by immunohistochemistry, and was correlated with clinicopathologic parameters. The expression of ACTA2 in human lung adenocarcinoma cells was modulated with short hairpin RNAs (shRNA) and siRNAs specifically targeting ACTA2. Results: The patients with lung adenocarcinomas with high ACTA2 expression in tumor cells showed significantly enhanced distant metastasis and unfavorable prognosis. ACTA2 downregulation remarkably impaired in vitro migration, invasion, clonogenicity, and transendothelial penetration of lung adenocarcinoma cells without affecting proliferation. Consistent with the in vitro results, depletion of ACTA2 in human lung adenocarcinoma PC14PE6 cells significantly reduced their metastatic potential without altering their tumorigenic potential. Expression of c-MET and FAK in lung adenocarcinoma cells was also reduced by ACTA2-targeting siRNAs and shRNAs, and was accompanied by a loss of mesenchymal characteristics. Conclusions: These findings indicate that ACTA2 regulates c-MET and FAK expression in lung adenocarcinoma cells, which positively and selectively influencemetastatic potential. Therefore,ACTA2 could be a promising prognostic biomarker and/or therapeutic target formetastatic lung adenocarcinoma.Clin Cancer Res; 19(21); 5879–89. 2013 AACR. Introduction Lung cancer is the most common cancer worldwide with the highest mortality rate (1). The identification of therapeutic targets in non–small cell lung cancer (NSCLC), such as EGF receptor (EGFR)-activating mutations, has enabled the development of effective targeted therapies for advanced NSCLC (2). However, the 5-year survival rate for NSCLC remains 15% across all stages of the disease. These unfavorable clinical outcomes originate from its high invasive and metastatic potential (3, 4). In particular, lung adenocarcinoma is known to establish distantmacrometastases in various organs, within months of diagnosis (5). Current targeted therapeutics have limited efficacy for the treatment of distant metastases in lung adenocarcinoma. The short latency of metastatic relapse in lung adenocarcinoma implies that the cancer cells in the primary tumor have already acquired numerous multi-organ metastatic competencies, including cell motility, invasiveness, resistance to hypoxia, enhanced angiogenesis, survival after detachment, and evasion of immune surveillance (6, 7). Authors' Affiliations: Cancer Stem Cell Research Center and Department of Neurosurgery, Samsung Medical Center; Graduate School, Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology (SAIHST), Sungkyunkwan University; SamsungBiomedical Research Institute, Department of Anatomy and Cell Biology, Department of Molecular Cell Biology, Center for Genome Research, and Department of Thoracic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). H.W. Lee and Y.M. Park contributed equally to this work. Corresponding Authors: Hyeon Ho Kim, Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology (SAIHST), Sungkyunkwan University, 50 Irwon-Dong, Gangnam-Gu, Seoul 135-710, South Korea. Phone: 82-2-3410-1039; Fax: 8223410-0534; E-mail: [email protected]; and Kyeung Min Joo, Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Graduate School for Heath Sciences & Technology Samsung Advanced Institute forHealthScience& Technology (SAIHST), Sungkyunkwan University, 50 Irwon-Dong, Gangnam-Gu, Seoul 135-710, South Korea. Phone: 82-2-2148-9779; Fax: 82-2148-9829; [email protected] doi: 10.1158/1078-0432.CCR-13-1181 2013 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org 5879 on April 20, 2017. © 2013 American Association for Cancer Research. clincancerres.aacrjournals.org Downloaded from Published OnlineFirst August 30, 2013; DOI: 10.1158/1078-0432.CCR-13-1181