AUTHOR=Liao Jinrong , Chen Zeng , Yu Zongyang , Huang Tao , Hu Dan , Su Ying , He Zhiyong , Zou Changyan , Zhang Lurong , Lin Xiandong 

TITLE=The Role of ARL4C in Erlotinib Resistance: Activation of the Jak2/Stat 5/β-Catenin Signaling Pathway

JOURNAL=Frontiers in Oncology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.585292

DOI=10.3389/fonc.2020.585292

ISSN=2234-943X

ABSTRACT=<p>Cancer patients who initially benefit from Erlotinib, a drug targeting <italic>EGFR</italic> path, eventually develop resistance to the drug. The underlying mechanism is largely unknown. This study investigated the role of <italic>ARL4C</italic> in Erlotinib resistance development of NSCLC. qRT-PCR and Western blotting were performed to analyze the expression of mRNA and protein of <italic>ARL4C</italic> in two NSCLC cell lines (HCC827 and PC-9). Several assays (MTS, colony formation, transwell migration, luciferase reporter, and chromatin-immunoprecipitation) were used to explore the role of <italic>ARL4C</italic> in biofunctional changes of Erlotinib-resistant cells and their associations with <italic>Jak2/Stat 5/</italic>β<italic>-catenin</italic> signaling. Results demonstrated that (1) long-term use of Erlotinib resulted in downregulation of <italic>ARL4C</italic>; (2) overexpression of ARL4C could regain the sensitivity to Erlotinib in the drug-resistant HCC827/ER cells, while downregulation of <italic>ARL4C</italic> increased HCC827, and PC-9 cells' resistance to the drug; (3) Erlotinib-induced downregulation of <italic>ARL4C</italic> resulted in phosphorylation of <italic>Jak2/Stat5</italic> and upregulation of β<italic>-catenin</italic> and their related molecules <italic>Axin2, CD44, Ccnd1, Lgr-5</italic>, and <italic>MMP7</italic>, which promoted the malignant behaviors of Erlotinib-resistant cells; (4) chromatin immunoprecipitation and luciferase reporter assay revealed that Stat5 could bind to β<italic>-catenin</italic> promoter to upregulate molecules to maintain the malignant behaviors, which might count for how Erlotinib-resistant cell survived while <italic>EGFR</italic> path was blocked; (5) the expression of <italic>ARL4C</italic> was not associated with known EGFR gene mutations in both Erlotinib-resistant cells and NSCLC tissues. Our data suggest that Erlotinib resistance of NSCLCs is associated with downregulation of <italic>ARL4C</italic> via affecting <italic>Jak/Stat/</italic>β<italic>-catenin</italic> signaling. <italic>ARL4C</italic> could serve as a biomarker to predict the effectiveness of TKI targeting therapy and a potential therapeutic target for overcoming Erlotinib resistance in NSCLC.</p>