title: MicroRNA-33a mediates the regulation of high mobility group AT-hook 2 gene (HMGA2) by thyroid transcription factor 1 (TTF-1/NKX2-1).
abstract: In lung cancers, TTF-1 displays seemingly paradoxical activities. Although TTF-1 is amplified in primary human lung cancers, it inhibits primary lung tumors from metastasizing in a mouse model system. It was reported that the oncogenic proepithelial mesenchymal transition (EMT) high mobility group AT-hook 2 gene (HMGA2) mediates the antimetastatic function of TTF-1. To gain mechanistic insight into the metastasis-critical signaling axis of TTF-1 to HMGA2, we used both reverse and forward strategies and discovered that microRNA-33a (miR-33a) is under direct positive regulation of TTF-1. By chromatin immunoprecipitation, we determined that TTF-1 binds to the promoter of SREBF2, the host gene of miR-33a. The 3'-untranslated region (UTR) of HMGA2 contains three predicted binding sites of miR-33a. We showed that the first two highly conserved sites are conducive to HMGA2 repression by miR-33a, establishing HMGA2 as a genuine target of miR-33a. Functional studies revealed that enforced expression of miR-33a inhibits the motility of lung cancer cells, and this inhibition can be rescued by overexpression of the form of HMGA2 without the 3'-UTR, suggesting that TTF-1 keeps the prometastasis gene HMGA2 in check via up-regulating miR-33a. This study reports the first miRNAs directly regulated by TTF-1 and clarifies how TTF-1 controls HMGA2 expression. Moreover, the documented importance of SREBF2 and miR-33a in regulating cholesterol metabolism suggests that TTF-1 may be a modulator of cholesterol homeostasis in the lung. Future studies will be dedicated to understanding how miRNAs influence the oncogenic activity of TTF-1 and the role of TTF-1 in cholesterol metabolism.
authors.affiliation: Penn State Cancer Institute, Penn State University, Hershey, Pennsylvania 17033.
authors.forename: Shawn J
authors.initials: SJ
authors.lastname: Rice
authors.affiliation: Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23501; Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23501.
authors.forename: Shao-Chiang
authors.initials: SC
authors.lastname: Lai
authors.affiliation: Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23501; Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23501.
authors.forename: Lauren W
authors.initials: LW
authors.lastname: Wood
authors.affiliation: Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23501; Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23501.
authors.forename: Kaitlin R
authors.initials: KR
authors.lastname: Helsley
authors.affiliation: Department of Pathology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: E Aaron
authors.initials: EA
authors.lastname: Runkle
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: Monte M
authors.initials: MM
authors.lastname: Winslow
authors.affiliation: Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23501; Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23501. Electronic address: mud@evms.edu.
authors.forename: David
authors.initials: D
authors.lastname: Mu
mesh_terms: D020413:3' Untranslated Regions / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000235:genetics / Q000378:metabolism; D025743:HMGA2 Protein / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D051379:Mice; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000096:biosynthesis / Q000235:genetics; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D025743:HMGA2 Protein; C550416:MIRN33a microRNA, human; D035683:MicroRNAs; C550417:Mirn33 microRNA, mouse; C000614412:NKX2-1 protein, human; D009363:Neoplasm Proteins; C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D012334:RNA, Neoplasm; C497390:SREBF2 protein, human; C497391:Srebf2 protein, mouse; D051782:Sterol Regulatory Element Binding Protein 2; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D002784:Cholesterol
keywords: Cholesterol Regulation; Gene Regulation; HMGA2; Lung Cancer; Metastasis; MicroRNA; SREBP2; TTF-1; miR-32; miR-33a