title: The sonic hedgehog signaling pathway maintains the cancer stem cell self-renewal of anaplastic thyroid cancer by inducing snail expression.
abstract: BACKGROUND
  Cancer stem cells (CSCs) have been recently identified in thyroid neoplasm. Anaplastic thyroid cancer (ATC) contains a higher percentage of CSCs than well-differentiated thyroid cancer. The signaling pathways and the transcription factors that regulate thyroid CSC self-renewal remain poorly understood.
  
  
  OBJECTIVE
  The objective of this study is to use two ATC cell lines (KAT-18 and SW1736) as a model to study the role of the sonic hedgehog (Shh) pathway in maintaining thyroid CSC self-renewal and to understand its underlying molecular mechanisms.
  
  
  METHODS
  The expression and activity of aldehyde dehydrogenase (ALDH), a marker for thyroid CSCs, was analyzed by Western blot and ALDEFLUOR assay, respectively. The effect of three Shh pathway inhibitors (cyclopamine, HhAntag, GANT61), Shh, Gli1, Snail knockdown, and Gli1 overexpression on thyroid CSC self-renewal was analyzed by ALDEFLUOR assay and thyrosphere formation. The sensitivity of transfected KAT-18 cells to radiation was evaluated by a colony survival assay.
  
  
  RESULTS
  Western blot analysis revealed that ALDH protein levels in five thyroid cancer cell lines (WRO82, a follicular thyroid cancer cell line; BCPAP and TPC1, two papillary thyroid cancer cell lines; KAT-18 and SW1736, two ATC cell lines) correlated with the percentage of the ALDH(High) cells as well as Gli1 and Snail expression. The Shh pathway inhibitors, Shh and Gli1 knockdown, in KAT-18 cells decreased thyroid CSC self-renewal and increased radiation sensitivity. In contrast, Gli1 overexpression led to increased thyrosphere formation, an increased percentage of ALDH(High) cells, and increased radiation resistance in KAT-18 cells. Inhibition of the Shh pathway by three specific inhibitors led to decreased Snail expression and a decreased number of ALDH(High) cells in KAT-18 and SW1736. Snail gene knockdown decreased the number of ALDH(High) cells in KAT-18 and SW1736 cells.
  
  
  CONCLUSIONS
  The Shh pathway promotes the CSC self-renewal in ATC cell lines by Gli1-induced Snail expression.
authors: Departments of General Surgery (K.B.H., X.X.) and Anatomy and Cell Biology (M.E.D., J.Y., Y.W., X.X.), Rush Medical College (A.J.W.), Chicago, Illinois 60612; Division of Endocrinology and Metabolism (D.L., M.X.), Department of Medicine, the Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Surgery (R.A.P.), NorthShore University Health System, Evanston, Illinois 60201.
authors: Katherine B
authors: KB
authors: Heiden
authors: Ashley J
authors: AJ
authors: Williamson
authors: Michelle E
authors: ME
authors: Doscas
authors: Jin
authors: J
authors: Ye
authors: Yimin
authors: Y
authors: Wang
authors: Dingxie
authors: D
authors: Liu
authors: Mingzhao
authors: M
authors: Xing
authors: Richard A
authors: RA
authors: Prinz
authors: Xiulong
authors: X
authors: Xu
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000502:physiology; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000071250:Snail Family Transcription Factors; D065646:Thyroid Carcinoma, Anaplastic / Q000378:metabolism* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D053823:Hedgehog Proteins; C509239:SHH protein, human; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D000444:Aldehyde Dehydrogenase