Wnt/β-catenin signaling pathway is a direct enhancer of thyroid transcription factor-1 in human papillary thyroid carcinoma cells

• Published in: PloS one 2011, Vol.6 (7), p.e22280-e22280
• Main Authors: Gilbert-Sirieix, Marie, Makoukji, Joelle, Kimura, Shioko, Talbot, Monique, Caillou, Bernard, Massaad, Charbel, Massaad-Massade, Liliane
• Format: Article
• Language: English
• Subjects: beta Catenin - genetics; beta Catenin - metabolism; Biology; Blotting, Western; Breast cancer; Carcinoma, Papillary - genetics; Carcinoma, Papillary - metabolism; Cell Differentiation; Cell growth; Chromatin Immunoprecipitation; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Enhancer Elements, Genetic - genetics; Experiments; Gene expression; Humans; Immunoenzyme Techniques; Immunofluorescence; Immunoglobulins; Kinases; LEF protein; Ligands; Lithium; Lithium chloride; Lithium Chloride - pharmacology; Localization; Luciferases - metabolism; Medicine; MicroRNAs; Microscopy; Mimicry; Molecular modelling; Papillary thyroid carcinoma; Polymerase chain reaction; Promoter Regions, Genetic - genetics; Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; Signal transduction; Signaling; siRNA; Studies; TCF Transcription Factors - genetics; TCF Transcription Factors - metabolism; Thyroglobulin; Thyroid; Thyroid cancer; Thyroid gland; Thyroid Neoplasms - genetics; Thyroid Neoplasms - metabolism; Thyroid transcription factor 1; Tissues; Transcription Factors; Tumor Cells, Cultured; Tumors; Wnt protein; Wnt Proteins - genetics; Wnt Proteins - metabolism; Wnt Signaling Pathway; Xenopus; β-Catenin
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0022280

The Wnt/β-catenin signaling pathway is involved in the normal development of thyroid gland, but its disregulation provokes the appearance of several types of cancers, including papillary thyroid carcinomas (PTC) which are the most common thyroid tumours. The follow-up of PTC patients is based on the monitoring of serum thyroglobulin levels which is regulated by the thyroid transcription factor 1 (TTF-1): a tissue-specific transcription factor essential for the differentiation of the thyroid. We investigated whether the Wnt/β-catenin pathway might regulate TTF-1 expression in a human PTC model and examined the molecular mechanisms underlying this regulation. Immunofluorescence analysis, real time RT-PCR and Western blot studies revealed that TTF-1 as well as the major Wnt pathway components are co-expressed in TPC-1 cells and human PTC tumours. Knocking-down the Wnt/β-catenin components by siRNAs inhibited both TTF-1 transcript and protein expression, while mimicking the activation of Wnt signaling by lithium chloride induced TTF-1 gene and protein expression. Functional promoter studies and ChIP analysis showed that the Wnt/β-catenin pathway exerts its effect by means of the binding of β-catenin to TCF/LEF transcription factors on the level of an active TCF/LEF response element at [-798, -792 bp] in TTF-1 promoter. In conclusion, we demonstrated that the Wnt/β-catenin pathway is a direct and forward driver of the TTF-1 expression. The localization of TCF-4 and TTF-1 in the same area of PTC tissues might be of clinical relevance, and justifies further examination of these factors in the papillary thyroid cancers follow-up.