Inhibition of TBK1 attenuates radiation-induced epithelial-mesenchymal transition of A549 human lung cancer cells via activation of GSK-3β and repression of ZEB1.
Radiotherapy is an effective treatment method for lung cancer, particularly when the disease is at an advanced stage. However, previous researchers have observed that the majority of patients with conventional radiation therapy develop distant metastases and succumb to the disease. Thus, identifying and understanding novel pathways for the development of new therapeutic targets is a major goal in research on pulmonary neoplasms. Recent studies suggest that epithelial-mesenchymal transition (EMT) is the most important contributor to cancer metastasis. Induction of this complex process requires endogenously produced microRNAs; specifically, downregulation of the miRNA-200c causes an induction of EMT. We recently identified the tank-binding kinase-1 (TBK1) as a downstream effector of the miR-200c-driven pathway, but the biological function of TBK1 in EMT remains unknown. In this study, we tested whether TBK1 has a role in radiation-induced EMT and identified associated potential mechanisms. Human alveolar type II epithelial carcinoma A549 cells were irradiated with (60)Co γ-rays. Western blotting revealed a time- and dose-dependent decrease in E-cadherin with a concomitant increase in vimentin after radiation, suggesting that the epithelial cells acquired a mesenchymal-like morphology. TBK1 siRNA significantly inhibited radiation-induced suppression of the epithelial marker E-cadherin and upregulation of the mesenchymal marker vimentin. The invasion and migratory potential of lung cancer cells upon radiation treatment was also reduced by TBK1 knockdown. Furthermore, radiation-induced EMT attenuated by TBK1 depletion was partially dependent on transcriptional factor ZEB1 expression. Finally, we found glycogen synthase kinase-3β (GSK-3β) is involved in regulation of radiation-induced EMT by TBK1. Thus, our findings reveal that TBK1 signaling regulates radiation-induced EMT by controlling GSK-3β phosphorylation and ZEB1 expression. TBK1 may therefore constitute a useful target for treatment of radiotherapy-induced metastasis diseases.
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Wen
W
Liu
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Yi-Juan
YJ
Huang
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Cong
C
Liu
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Yan-Yong
YY
Yang
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Hu
H
Liu
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Jian-Guo
JG
Cui
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Ying
Y
Cheng
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Fu
F
Gao
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Jian-Ming
JM
Cai
Department of Radiation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, PR China.
Bai-Long
BL
Li
D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition; D005720:Gamma Rays / Q000009:adverse effects; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000209:etiology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011878:Radiotherapy / Q000009:adverse effects*; D051785:Smad Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D000071799:Zinc Finger E-box-Binding Homeobox 1
D018398:Homeodomain Proteins; D016328:NF-kappa B; D051785:Smad Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D038362:Glycogen Synthase Kinase 3