Abstract 170: Loss of the ubiquitin-specific peptidase 18 (USP18) reduces lung cancer metastasis

Abstract

Abstract Metastasis is a major cause of cancer-related mortality. Yet, current antineoplastic strategies do not effectively repress metastasis. Thus, there is a pressing need to explore targets that can reduce metastasis, especially in lung cancer that is the most common cause of cancer mortality. Our prior work reported that expression of the ubiquitin-specific peptidase 18 (USP18) was augmented in diverse cancers (including lung cancers) and USP18 knock-down suppressed in vitro and in vivo growth of murine and human lung cancers. This deubiquitinase stabilizes target proteins by removing interferon-stimulated gene 15 (ISG15) from substrate proteins. We explored here whether engineered loss of USP18 decreased lung cancer metastasis. Stable USP18 knockdown was independently achieved in human (A549 and H1299) and murine (344SQ and KC2) lung cancer cells by use of small hairpin RNAs (shRNAs). Notably, knockdown of USP18 expression reduced lung cancer cellular proliferation, migration and invasion versus control shRNA transfectants (p < 0.001). Lung cancer cells selected for high metastatic potential (344SQ and KC2) were independently injected via tail vein or subcutaneously to establish metastatic mouse models. USP18 knockdown statistically-significantly decreased lung cancer metastases as compared to control shRNA transfectants. To elucidate engaged mechanisms, Reverse Phase Protein Array (RPPA) analysis was performed to interrogate over 300 growth-regulatory proteins in human (A549 and H1299) and murine (344SQ and KC2) lung cancer cells having engineered USP18 knockdown. Results were compared to control shRNA transfectants. Ingenuity pathway analysis highlighted fatty acid synthase (FASN) as a potential USP18 target that regulated lung cancer metastasis. Independent immunoblot analysis confirmed FASN expression was reduced in cancers once USP18 knockdown was achieved. Functional validation of FASN in lung metastasis is underway. These and other findings that will be presented provide a strong rationale for targeting the deubiquitinase USP18 to reduce lung cancer metastasis and combat lung cancers. Citation Format: Zibo Chen, Lin Zheng, Yulong Chen, Masanori Kawakami, Lisa Mustachio, Jason Roszik, Xin Liu, Jonathan Kurie, Xi Liu, Ethan Dmitrovsky. Loss of the ubiquitin-specific peptidase 18 (USP18) reduces lung cancer metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 170.