OncoTargets and Therapy (Dec 2019)
IRF1 Negatively Regulates Oncogenic KPNA2 Expression Under Growth Stimulation and Hypoxia in Lung Cancer Cells
Abstract
Jie-Xin Huang,1 Yi-Cheng Wu,2 Ya-Yun Cheng,1 Chih-Liang Wang,3,4,* Chia-Jung Yu1,4–6,* 1Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; 2Department of Thoracic Surgery, Chang Gung Memorial Hospital, Taoyuan, Taiwan; 3School of Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan; 4Division of Pulmonary Oncology and Interventional Bronchoscopy, Department of Thoracic Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan; 5Department of Cell and Molecular Biology, College of Medicine, Chang Gung University, Taoyuan, Taiwan; 6Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan*These authors contributed equally to this workCorrespondence: Chia-Jung YuDepartment of Cell and Molecular Biology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Guishan District, Taoyuan City, TaiwanTel +886-3-2118800 ext. 3424Fax +886-3-2118042Email [email protected] WangDivision of Pulmonary Oncology and Interventional Bronchoscopy, Department of Thoracic Medicine, Chang Gung Memorial Hospital, Linkou, 5 Fuxing Street, Guishan District, Taoyuan City, TaiwanEmail [email protected]: Karyopherin alpha 2 (KPNA2) has been reported as an oncogenic protein in numerous human cancers and is currently considered a potential therapeutic target. However, the transcriptional regulation and physiological conditions underlying KPNA2 expression remain unclear. The aim of the present study was to investigate the role and regulation of interferon regulatory factor-1 (IRF1) in modulating KPNA2 expression in lung adenocarcinoma (ADC).Materials and methods: Bioinformatics tools and chromatin immunoprecipitation were used to analyze the transcription factor (TF) binding sites in the KPNA2 promoter region. We searched for a potential role of IRF1 in non-small-cell lung cancer (NSCLC) using Oncomine and Kaplan-Meier Plotter datasets. qRT-PCR was applied to examine the role of IRF1 and signaling involved in regulating KPNA2 transcription. Western blotting was used to determine the effects of extracellular stimulation and intracellular signaling on the modulation of KPNA2-related TF expression.Results: IRF1 was identified as a novel TF that suppresses KPNA2 gene expression. We observed that IRF1 expression was lower in cancerous tissues than in normal lung tissues and that its low expression was correlated with poor prognosis in NSCLC. Notably, both ataxia telangiectasia mutated (ATM) and mechanistic target of rapamycin (mTOR) inhibitors reduced KPNA2 expression, which was accompanied by increased expression of IRF1 but decreased expression of E2F1, a TF that promotes KPNA2 expression in lung ADC cells. IRF1 knockdown restored the reduced levels of KPNA2 in ATM inhibitor-treated cells. We further demonstrated that epidermal growth factor (EGF)-activated mTOR and hypoxia-induced ATM suppressed IRF1 expression but promoted E2F1 expression, which in turn upregulated KPNA2 expression in lung ADC cells.Conclusion: IRF1 acts as a potential tumor suppressor in NSCLC. EGF and hypoxia promote KPNA2 expression by simultaneously suppressing IRF1 expression and enhancing E2F1 expression in lung ADC cells. Our study provides new insights into targeted therapy for lung cancer.Keywords: lung adenocarcinoma, KPNA2, IRF1, E2F1, EGF, hypoxia
