Department of Medicine and Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, USA.
Oncogene. 2011 Jul 14;30(28):3153-62. doi: 10.1038/onc.2011.44. Epub 2011 Mar 7.
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.
甲状腺特异性表达致癌 BRAF（Tg-Braf）的小鼠会发展出甲状腺乳头状癌（PTC），这些肿瘤具有局部侵袭性，并有明确的甲状腺低分化癌（PDTC）病灶。为了研究 PTC-PDTC 的进展，我们通过激光捕获显微切割从同一动物的 PDTC 和 PTC 配对样本中进行 RNA 微阵列分析。对 8 对配对样本的分析显示，参与细胞黏附和细胞内连接的基因发生了深刻的失调，其变化与上皮间质转化（EMT）一致。免疫组织化学证实了这一点，因为与相邻的 PTC 相比，PDTC 中波形蛋白表达增加，E-钙黏蛋白丢失。此外，PDTC 对磷酸化 Smad2 呈阳性染色，表明转化生长因子（TGF）β在介导这一过程中起作用。因此，TGFβ 诱导 Tg-Braf 小鼠甲状腺细胞原代培养中的 EMT，而野生型甲状腺细胞保留其上皮特征。TGFβ 诱导的 Smad2 磷酸化、转录活性和 EMT 的诱导需要 Tg-Braf 甲状腺细胞中丝裂原激活蛋白激酶（MAPK）途径的激活。因此，致癌 BRAF 的肿瘤起始使甲状腺细胞容易受到 TGFβ 诱导的 EMT，这是一个依赖于 MAPK 的过程。
