title: Thioredoxin interacting protein (TXNIP) is a novel tumor suppressor in thyroid cancer.
abstract: BACKGROUND
  Thyroid cancer is the most common endocrine malignancy, and many patients with metastatic differentiated thyroid cancer (DTC), poorly differentiated thyroid cancer (PDTC), and anaplastic thyroid cancer (ATC) fail to respond to conventional therapies, resulting in morbidity and mortality. Additional therapeutic targets and treatment options are needed for these patients. We recently reported that peroxisome proliferator-activated receptor gamma (PPARγ) is highly expressed in ATC and confers an aggressive phenotype when overexpressed in DTC cells.
  
  
  METHODS
  Microarray analysis was used to identify downstream targets of PPARγ in ATC cells. Western blot analysis and immunohistochemistry (IHC) were used to assess thioredoxin interacting protein (TXNIP) expression in thyroid cancer cell lines and primary tumor specimens. Retroviral transduction was used to generate ATC cell lines that overexpress TXNIP, and assays that assess glucose uptake, viable cell proliferation, and invasion were used to characterize the in vitro properties of these cells. An orthotopic thyroid cancer mouse model was used to assess the effect of TXNIP overexpression in ATC cell lines in vivo.
  
  
  RESULTS
  Using microarray analysis, we show that TXNIP is highly upregulated when PPARγ is depleted from ATC cells. Using Western blot analysis and IHC, we show that DTC and ATC cells exhibit differential TXNIP expression patterns. DTC cell lines and patient tumors have high TXNIP expression in contrast to low or absent expression in ATC cell lines and tumors. Overexpression of TXNIP decreases the growth of HTh74 cells compared to vector controls and inhibits glucose uptake in the ATC cell lines HTh74 and T238. Importantly, TXNIP overexpression in T238 cells results in attenuated tumor growth and decreased metastasis in an orthotopic thyroid cancer mouse model.
  
  
  CONCLUSIONS
  Our findings indicate that TXNIP functions as a tumor suppressor in thyroid cells, and its downregulation is likely important in the transition from differentiated to advanced thyroid cancer. These studies underscore the potential of TXNIP as a novel therapeutic target and prognostic indicator in advanced thyroid cancer.
authors.affiliation: Department of Medicine, Division of Endocrinology, Diabetes, & Metabolism, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA. Jennifer.Morrison@ucdenver.edu.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Morrison
authors.forename: Laura A
authors.initials: LA
authors.lastname: Pike
authors.forename: Sharon B
authors.initials: SB
authors.lastname: Sams
authors.forename: Vibha
authors.initials: V
authors.lastname: Sharma
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhou
authors.forename: Jill J
authors.initials: JJ
authors.lastname: Severson
authors.forename: Aik-Choon
authors.initials: AC
authors.lastname: Tan
authors.forename: William M
authors.initials: WM
authors.lastname: Wood
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Haugen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D064593:Heterografts; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism*; D014161:Transduction, Genetic
chemical_list: D002352:Carrier Proteins; C486715:TXNIP protein, human