title: Cytoplasmic aryl hydrocarbon receptor regulates glycogen synthase kinase 3 beta, accelerates vimentin degradation, and suppresses epithelial-mesenchymal transition in non-small cell lung cancer cells.
abstract: Aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, has been studied extensively in carcinogenesis through the genomic pathway. In recent years, AHR has also been reported to exert positive or negative effects on epithelial-mesenchymal transition (EMT), the crucial step in tumor malignant progression. However, the detailed mechanism remains controversial. Analysis of AHR-expression levels in non-small cell lung cancer cell lines and lung cancer tissues revealed an inverse correlation between AHR protein levels and tumor cell invasion and metastasis. Overexpression of wild-type AHR in H1299 cells (AHR poorly expressed, potently invasive) not only accelerated mesenchymal vimentin degradation, but also prevented cell invasion in vitro and in vivo. In the absence of AHR agonists, the overexpressed AHR protein was predominantly localized in the cytoplasm, where it interacted with vimentin and functioned as an E3 ubiquitin ligase. A 6-h incubation with the proteasome inhibitor MG-132 fully rescued vimentin from AHR-mediated proteasomal degradation. In AHR-overexpressing H1299 cells, either vimentin degradation or invasive suppression could be reversed when glycogen synthase kinase 3 beta (GSK3β) was inactivated by CHIR-99021 treatment. In contrast, silencing of AHR in A549 cells (AHR highly expressed, weakly invasive) resulted in the downregulation of epithelial biomarkers (E-cadherin and claudin-1), augmentation of mesenchymal vimentin level, and GSK3β Ser-9 hyper-phosphorylation, which led to enhanced invasiveness. This work demonstrates that cytoplasmic, resting AHR protein may act as an EMT suppressor via a non-genomic pathway. Depletion of cytoplasmic AHR content represents a potential switch for EMT, thereby leading to the scattering of tumor cells.
authors.affiliation: Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.|Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Ching-Hao
authors.initials: CH
authors.lastname: Li
authors.affiliation: School of Pharmacy, Taipei Medicine University, 250 Wu-Hsing Street, Taipei, Taiwan.
authors.forename: Chen-Wei
authors.initials: CW
authors.lastname: Liu
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, 1 Jen-Ai Road, Section 1, Taipei 10, Taiwan.
authors.forename: Chi-Hao
authors.initials: CH
authors.lastname: Tsai
authors.affiliation: Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Peng
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, 1 Jen-Ai Road, Section 1, Taipei 10, Taiwan.
authors.forename: Yu-Hsuan
authors.initials: YH
authors.lastname: Yang
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, 1 Jen-Ai Road, Section 1, Taipei 10, Taiwan.
authors.forename: Po-Lin
authors.initials: PL
authors.lastname: Liao
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, China Medicine University, Taichung, Taiwan.
authors.forename: Chen-Chen
authors.initials: CC
authors.lastname: Lee
authors.affiliation: School of Pharmacy, Taipei Medicine University, 250 Wu-Hsing Street, Taipei, Taiwan. ywcheng@tmu.edu.tw.
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Cheng
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, 1 Jen-Ai Road, Section 1, Taipei 10, Taiwan. jjkang@ntu.edu.tw.
authors.forename: Jaw-Jou
authors.initials: JJ
authors.lastname: Kang
mesh_terms: D000368:Aged; D000818:Animals; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D018336:Receptors, Aryl Hydrocarbon; D014746:Vimentin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D046988:Proteasome Endopeptidase Complex
keywords: Aryl hydrocarbon receptor; Epithelial–mesenchymal transition; Glycogen synthase kinase 3 beta; Ubiquitin; Vimentin