Abstract 2177: Tumor suppressor effects of ETS2 transcriptional factor in human non-small cell lung cancer

Abstract

Abstract Advances in prevention and treatment of non-small cell lung cancer (NSCLC) are dependent in part on the characterization of tumor suppressor genes and oncogenes and the roles they elicit in the pathogenesis of this malignancy. Although v-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) is a canonical transcription factor that regulates various cancer-associated cellular and developmental processes including proliferation and migration, its function in lung carcinogenesis is still unknown. In this study we sought to examine the role of ETS2 in NSCLC pathogenesis. We first examined ETS2 mRNA expression in lung adenocarcinomas (n=80) and normal lung (n=30) which we profiled using microarrays, and in seven matched adenocarcinoma and normal lung pairs analyzed using next-generation sequencing technology. Both array and sequencing datasets revealed that ETS2 mRNA was significantly lower in lung adenocarcinomas relative to normal lung (p<0.001) which was confirmed by quantitative PCR analysis. Moreover and in the microaray dataset, ETS2 mRNA expression was significantly anti-correlated with that of the proliferation marker KI67 (R=−0.59, p<0.001). In addition, in silico analysis of publicly available datasets demonstrated that ETS2 mRNA was lower in NSCLC compared to normal lung (all p<0.001), and interestingly, was also lower in airways of healthy smokers relative to non-smokers (p<0.001). We next assessed ETS2 immunohistochemical protein expression using tissue microarrays comprised of 342 formalin-fixed paraffin-embedded NSCLC (adenocarcinoma, n=226; SCC, n=116) tissue specimens. There were no statistically significant differences in ETS2 expression by histology, stage or age. We then assessed the association of ETS2 protein expression with clinical outcome. Non-treated all stage (n=206) or stage-I (n=157) patients with relatively lower ETS2 protein expression exhibited significantly shortened disease-free survival compared to patients with higher expression (p=0.008 and p=0.004 of the log-rank test, respectively). In addition, patients with relatively lower ETS2 expression exhibited significantly poorer response to adjuvant therapy compared to patients with higher ETS2 expression (p=0.01). We then probed the effect of modulating ETS2 expression in NSCLC cells. Knockdown of ETS2 expression by RNA interference significantly increased anchorage-dependent colony formation (p=0.004) as well as augmented cellular migration (p=0.01) and invasion through matrigel (p=0.02) compared to cells transfected with control siRNA. Our findings provide evidence that ETS2 may function as a tumor suppressor gene in NSCLC that can aid clinically in identification of aggressive tumors and biologically in increasing our understanding of the pathogenesis of this malignancy (Supported by DoD PROSPECT W81XWH-07-1-0306 and Lung Cancer Research Foundation grants). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2177. doi:1538-7445.AM2012-2177