title: Thyroid transcription factor-1 inhibits transforming growth factor-beta-mediated epithelial-to-mesenchymal transition in lung adenocarcinoma cells.
abstract: Thyroid transcription factor-1 (TTF-1) is expressed in lung cancer, but its functional roles remain unexplored. TTF-1 gene amplification has been discovered in a part of lung adenocarcinomas, and its action as a lineage-specific oncogene is highlighted. Epithelial-to-mesenchymal transition (EMT) is a crucial event for cancer cells to acquire invasive and metastatic phenotypes and can be elicited by transforming growth factor-beta (TGF-beta). Mesenchymal-to-epithelial transition (MET) is the inverse process of EMT; however, signals that induce MET are largely unknown. Here, we report a novel functional aspect of TTF-1 that inhibits TGF-beta-mediated EMT and restores epithelial phenotype in lung adenocarcinoma cells. This effect was accompanied by down-regulation of TGF-beta target genes, including presumed regulators of EMT, such as Snail and Slug. Moreover, silencing of TTF-1 enhanced TGF-beta-mediated EMT. Thus, TTF-1 can exert a tumor-suppressive effect with abrogation of cellular response to TGF-beta and attenuated invasive capacity. We further revealed that TTF-1 down-regulates TGF-beta2 production in A549 cells and that TGF-beta conversely decreases endogenous TTF-1 expression, suggesting that enhancement of autocrine TGF-beta signaling accelerates the decrease of TTF-1 expression and vice versa. These findings delineate potential links between TTF-1 and TGF-beta signaling in lung cancer progression through regulation of EMT and MET and suggest that modulation of TTF-1 expression can be a novel therapeutic strategy for treatment of lung adenocarcinoma.
authors.affiliation: Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Roy-Akira
authors.initials: RA
authors.lastname: Saito
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Watabe
authors.forename: Kana
authors.initials: K
authors.lastname: Horiguchi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kohyama
authors.forename: Masao
authors.initials: M
authors.lastname: Saitoh
authors.forename: Takahide
authors.initials: T
authors.lastname: Nagase
authors.forename: Kohei
authors.initials: K
authors.lastname: Miyazono
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics; D018827:Carcinoma, Lewis Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D004847:Epithelial Cells / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D008648:Mesoderm / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness; D015398:Signal Transduction; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D015820:Cadherins; D004268:DNA-Binding Proteins; C504003:TTF1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2