Abstract 4855: Loss of USP18 represses invasion and metastasis of lung cancer
Authors: Zheng Lin , Mustachio Lisa , Chen Yulong , Liu Xi , Roszik Jason , Kurie Jonathan , Dmitrovsky Ethan 
Published: July 2017

Abstract
Metastasis is a major cause of human lung cancer mortality. Uncovering novel targets and mechanisms involved in regulating metastasis is critical for developing effective ways to improve lung cancer survival. It is reported that ubiquitin and ubiquitin-like pathways can regulate invasion and metastasis. We previously found that USP18 (Ubiquitin Specific Peptidase 18) is substantially upregulated in several cancers, including lung cancer. Engineered repression of the deubiquitinase USP18 decreased growth, increased apoptosis and augmented chemotherapeutic agent response of lung cancer cells. Our prior work showed that loss of USP18 can destabilize specific oncogenic proteins and this results in the marked reduction of lung cancer cell growth and in vivo tumorigenicity. This study sought to explore the precise role of USP18 expression in invasion, migration and metastasis of lung cancer. In murine (KC2 and 344SQ) and human (A549 and H1299) lung cancer cells with varying degrees of metastatic potential, knock-down of USP18 by different short hairpin RNAs (shRNAs) decreased cell growth and increased cell death as compared to vector control transfectants. The findings from wound-healing migration and Transwell invasion assays established that USP18 knock-down in all studied lung cancer cell lines conferred substantial reduction of migration and invasion versus vector control transfected cell lines (p &lt; 0.001). In mouse models, USP18 knock-down of lung cancer cell lines displayed a lower number of lung cancer metastasis in vivo. To discern engaged mechanisms, Reverse Phase Protein Arrays (RPPAs) were performed to interrogate over 300 growth-regulatory proteins in murine (344SQ and KC2) and human (A549 and H1299) lung cancer cells following USP18 knock-down. Using RPPAs, potential targets identified were differentially expressed between USP18 knock-down and vector control transfected lung cancer cells. Highlighted species included Myc, eEF2K (Eukaryotic Elongation Factor 2 Kinase), Programmed Cell Death 4 (PDCD4), Hes Family BHLH Transcription Factor 1 (Hes) and Polo Like Kinase 1 (PLK1), among other species. In addition, phosphorylated Acetyl-CoA Carboxylase (ACC), a key component of the 5'-adenosine monophosphate-activated protein kinase (AMPK) pathway, was significantly affected in lung cancer cell lines following USP18 knock-down (p &lt; 0.05). Ingenuity Pathway Analysis and functional validation are now underway to uncover specific pathways directly involved in the observed reduction of lung cancer metastases. Taken together, this study implicates the deubiquitinase USP18 as a molecular target to combat lung cancer metastases.
Citation Format: Lin Zheng, Lisa Mustachio, Yulong Chen, Xi Liu, Jason Roszik, Jonathan Kurie, Ethan Dmitrovsky. Loss of USP18 represses invasion and metastasis of lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4855. doi:10.1158/1538-7445.AM2017-4855