title: Multiple pluripotent stem cell markers in human anaplastic thyroid cancer: the putative upstream role of SOX2.
abstract: BACKGROUND
  Anaplastic thyroid carcinoma (ATC) is a rare and aggressive endocrine tumor with highly undifferentiated morphology. It has been suggested that cancer stem cells (CSCs) might play a central role in ATC. The objectives of this study were (i) to characterize CSCs from ex vivo ATC specimens by investigating the expression of several pluripotent stem cell markers, and (ii) to evaluate in vitro drug resistance modifications after specific CSC transcription factor switch-off.
  
  
  METHODS
  In ex vivo experiments, eight formalin-fixed, paraffin-embedded ATC specimens were analyzed by reverse-transcription and real-time quantitative PCR and immunohistochemistry. In in vitro experiments using ATC SW1736 cells, the expression levels of OCT-4, NANOG, and ABCG2 and the sensitivity to either cisplatin or doxorubicin were evaluated after silencing.
  
  
  RESULTS
  OCT-4, KLF4, and SOX2 transcription factors and C-KIT and THY-1 stem surface antigens showed variable up-regulation in all ATC cases. The SW1736 cell line was characterized by a high percentage of stem population (10.4±2.1% of cells were aldehyde dehydrogenase positive) and high expression of several CSC markers (SOX2, OCT4, NANOG, C-MYC, and SSEA4). SOX2 silencing down-regulated OCT-4, NANOG, and ABCG2. SOX2 silencing sensitized SW1736 cells, causing a significant cell death increase (1.8-fold) in comparison to control cells with 10 μM cisplatin (93.9±3.4% vs. 52.6±9.4%, p<0.01) and 2.7 fold with 0.5 μM doxorubicin (45.8±9.9% vs. 17.1±3.4% p<0.01). ABCG2 silencing caused increased cell death with both cisplatin (74.9±1.4%) and doxorubicin treatment (74.1±0.1%) vs. no-target-treated cells (respectively, 45.8±1.0% and 48.6±1.0%, p<0.001).
  
  
  CONCLUSIONS
  The characterization of CSCs in ATC through the analysis of multiple pluripotent stem cell markers might be useful in identifying cells with a stem-like phenotype capable of resisting conventional chemotherapy. In addition, our data demonstrate that SOX2 switch-off through ABCG2 transporter down-regulation has a major role in overcoming CSC chemotherapy resistance.
authors.affiliation: Biomedical Department of Internal and Specialized Medicine (DiBiMIS), University of Palermo, Palermo, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Carina
authors.forename: Giovanni
authors.initials: G
authors.lastname: Zito
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pizzolanti
authors.forename: Pierina
authors.initials: P
authors.lastname: Richiusa
authors.forename: Angela
authors.initials: A
authors.lastname: Criscimanna
authors.forename: Vito
authors.initials: V
authors.lastname: Rodolico
authors.forename: Laura
authors.initials: L
authors.lastname: Tomasello
authors.forename: Maria
authors.initials: M
authors.lastname: Pitrone
authors.forename: Walter
authors.initials: W
authors.lastname: Arancio
authors.forename: Carla
authors.initials: C
authors.lastname: Giordano
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D000090062:Kruppel-Like Factor 4; D000071317:Nanog Homeobox Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D014411:Neoplastic Stem Cells / Q000473:pathology; D050814:Octamer Transcription Factor-3 / Q000235:genetics; D039904:Pluripotent Stem Cells; D055748:SOXB1 Transcription Factors / Q000235:genetics*; D065646:Thyroid Carcinoma, Anaplastic; D013964:Thyroid Neoplasms; D015854:Up-Regulation
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D018398:Homeodomain Proteins; C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; C486780:NANOG protein, human; D000071317:Nanog Homeobox Protein; D009363:Neoplasm Proteins; D050814:Octamer Transcription Factor-3; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors; D004317:Doxorubicin; D002945:Cisplatin