title: MiRNA-146b-5p upregulates migration and invasion of different Papillary Thyroid Carcinoma cells.
abstract: BACKGROUND
  Tumor invasiveness is directly related to the ability of tumor cells to migrate and invade surrounding tissues, usually degrading extracellular matrix. Despite significant progress in the knowledge about migration and invasion, there is much more to elucidate about their regulatory mechanisms, especially in cancer cells. MicroRNAs (miRs) were recently described as important regulators of migration. Differential expression of miRs in cancer is frequently associated with progression, invasion and metastasis. In papillary thyroid carcinoma (PTC), miR-146b-5p is highly expressed and positively correlated to the degree of malignancy.
  
  
  METHODS
  This study aimed to investigate the role of miR-146b-5p on the migratory and invasive behaviors of thyroid cells, using a non tumor rat thyroid follicular cell line (PCCl3) transfected with the miR-146b-5p genomic region, and two PTC cell lines (TPC-1 and BCPAP, bearing distinct oncogenic backgrounds), which express high levels of miR-146b-5p, after miR-146b inhibition by antagomiR and miR-146b overexpression by mimics-miR. Migration and invasion were studied by time-lapse and transwell assays (with and without Matrigel®). Gelatin degradation assays were also employed, as well as F-actin staining.
  
  
  RESULTS
  Migration and invasion of PCCl3 were increased 2-3x after miR-146b-5p overexpression (10X) and large lamellipodia were evident in those cells. After miR-146b-5p inhibition, TPC-1 and BCPAP migration and invasion were significantly reduced, with cells showing several simultaneous processes and low polarity. Gelatin degradation was inhibited in TPC-1 cells after inhibition of miR-146b-5p, but was unaffected in BCPAP cells, which did not degrade gelatin. The inhibition of miR-146b-5p in PCCl3 also inhibited migration and invasion, and additional (exogenous) overexpression of this miR in TPC-1 and BCPAP cells increased migration and invasion, without effects on cell morphology or gelatin degradation. The overexpression of SMAD4 in BCPAP cells, a validated target of miR-146b-5p and key protein in the TGF-β signaling pathway, inhibited migration similarly to the effects observed with the antagomiR 146b-5p.
  
  
  CONCLUSIONS
  miR-146b-5p positively regulates migration and invasion of thyroid normal and tumor follicular cells (independently from their original mutation, either BRAF or RET/PTC), through a mechanism that involves the actin cytoskeleton but not an increased capacity of matrix degradation.
authors.affiliation: Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1524, Prédio I, CEP 05508-000, São Paulo, SP, Brazil. cilima77@usp.br.
authors.forename: Cilene Rebouças
authors.initials: CR
authors.lastname: Lima
authors.affiliation: Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1524, Prédio I, CEP 05508-000, São Paulo, SP, Brazil. mvgeraldo@usp.br.
authors.forename: Murilo Vieira
authors.initials: MV
authors.lastname: Geraldo
authors.affiliation: Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1524, Prédio I, CEP 05508-000, São Paulo, SP, Brazil. cesar.fuziwara@usp.br.
authors.forename: Cesar Seigi
authors.initials: CS
authors.lastname: Fuziwara
authors.affiliation: Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1524, Prédio I, CEP 05508-000, São Paulo, SP, Brazil. etkimura@usp.br.
authors.forename: Edna Teruko
authors.initials: ET
authors.lastname: Kimura
authors.affiliation: Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1524, Prédio I, CEP 05508-000, São Paulo, SP, Brazil. mfsantos@usp.br.
authors.forename: Marinilce Fagundes
authors.initials: MF
authors.lastname: Santos
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism; D002291:Carcinoma, Papillary; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D009361:Neoplasm Invasiveness / Q000235:genetics*; D051381:Rats; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation / Q000235:genetics*
chemical_list: D035683:MicroRNAs