Abstract
Mice with thyroid-specific expression of oncogenic BRAF (Tg-Braf) develop papillary thyroid cancers (PTCs) that are locally invasive and have well-defined foci of poorly differentiated thyroid carcinoma (PDTC). To investigate the PTC-PDTC progression, we performed a microarray analysis using RNA from paired samples of PDTC and PTC collected from the same animals by laser capture microdissection. Analysis of eight paired samples revealed a profound deregulation of genes involved in cell adhesion and intracellular junctions, with changes consistent with an epithelial-mesenchymal transition (EMT). This was confirmed by immunohistochemistry, as vimentin expression was increased and E-cadherin lost in PDTC compared with adjacent PTC. Moreover, PDTC stained positively for phospho-Smad2, suggesting a role for transforming growth factor (TGF)Β in mediating this process. Accordingly, TGFΒ-induced EMT in primary cultures of thyroid cells from Tg-Braf mice, whereas wild-type thyroid cells retained their epithelial features. TGFΒ-induced Smad2 phosphorylation, transcriptional activity and induction of EMT required mitogen-activated protein kinase (MAPK) pathway activation in Tg-Braf thyrocytes. Hence, tumor initiation by oncogenic BRAF renders thyroid cells susceptible to TGFΒ-induced EMT, through a MAPK-dependent process.
Original language | English (US) |
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Pages (from-to) | 3153-3162 |
Number of pages | 10 |
Journal | Oncogene |
Volume | 30 |
Issue number | 28 |
DOIs | |
State | Published - Jul 14 2011 |
Keywords
- BRAF
- TGFΒ
- epithelialmesenchymal transition
- thyroid
ASJC Scopus subject areas
- Molecular Biology
- Genetics
- Cancer Research