title: Thyroid hormone receptor beta (THRB) is a major target gene for microRNAs deregulated in papillary thyroid carcinoma (PTC).
abstract: BACKGROUND
  Loss of the thyroid hormone receptor is common in tumors. In mouse models, a truncated THRB gene leads to thyroid cancer. Previously, we observed up-regulation of the expression of eight microRNAs (miRs) in papillary thyroid carcinoma (PTC) tumors.
  
  
  OBJECTIVE
  Our objective was to determine whether THRB might be inhibited by miRs up-regulated in PTC.
  
  
  METHODS
  The potential binding of miR to the 3'-untranslated region of THRB was analyzed in silico. Direct inhibition by miRs binding to the cloned 3'-untranslated region of THRB was evaluated using luciferase assays. Inhibition of endogenous THRB and its target genes (DIO1 and APP) was examined in cell lines transfected by pre-miRs. The impact on thyroid hormone response element (TRE) was evaluated in promoter assays. Correlations between the expression of THRB and miRs was evaluated in 13 PTC tumor/normal tissue pairs.
  
  
  RESULTS
  THRB contains binding sites for the top seven miRs up-regulated in PTC (P = 0.0000002). Direct interaction with THRB was shown for miR-21 and miR-146a. We observed lower levels of THRB transcripts in cell lines transfected with miR-21, -146a, and -221 (down-regulation of 37-48%; P < 0.0001), but not with miR-181a. THRB protein was suppressed down to 10-28% by each of four miRs. Concomitant expression of DIO1 and APP was affected (down-regulation of 32-66%, P < 0.0034 and up-regulation of 48-57%, P < 0.0002, respectively). All four miRs affected TRE activity in promoter assays. Down-regulation of luciferase occurred after transfection with pTRE-TK-Luc construct and each of four miRs. The analysis of tumor/normal tissue pairs revealed down-regulation of THRB in 11 of 13 pairs (1.3- to 9.1-fold), and up-regulation of miR-21, -146a, -181a, and -221 in almost all pairs.
  
  
  CONCLUSIONS
  MiRs up-regulated in PTC tumors directly inhibit the expression of THRB, an important tumor suppressor gene.
authors.affiliation: Human Cancer Genetics Program, Comprehensive Cancer Center, The Ohio State University, 804 Biomedical Research Tower, 460 West 12th Avenue, Columbus, Ohio 43210, USA. krystian.jazdzewski@osumc.edu
authors.forename: Krystian
authors.initials: K
authors.lastname: Jazdzewski
authors.forename: Joanna
authors.initials: J
authors.lastname: Boguslawska
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Jendrzejewski
authors.forename: Sandya
authors.initials: S
authors.lastname: Liyanarachchi
authors.forename: Janusz
authors.initials: J
authors.lastname: Pachucki
authors.forename: Kazimierz A
authors.initials: KA
authors.lastname: Wardyn
authors.forename: Alicja
authors.initials: A
authors.lastname: Nauman
authors.forename: Albert
authors.initials: A
authors.lastname: de la Chapelle
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D002277:Carcinoma; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D008156:Luciferases / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000473:pathology; D037042:Thyroid Hormone Receptors beta / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000235:genetics / Q000473:pathology; D014158:Transcription, Genetic; D014284:Triiodothyronine / Q000502:physiology
chemical_list: D020413:3' Untranslated Regions; D016564:Amyloid beta-Protein Precursor; D035683:MicroRNAs; D037042:Thyroid Hormone Receptors beta; D014284:Triiodothyronine; D008156:Luciferases