Orim Florence, Bychkov Andrey, Shimamura Mika, Nakashima Masahiro, Ito Masahiro, Matsuse Michiko, Kurashige Tomomi, Suzuki Keiji, Saenko Vladimir, Nagayama Yuji, Yamashita Shunichi, Mitsutake Norisato
1 Department of Radiation Medical Sciences, Nagasaki University , Nagasaki, Japan .
Thyroid. 2014 Mar;24(3):502-10. doi: 10.1089/thy.2013.0038. Epub 2014 Jan 15.
The BRAF(V600E) mutation is the most common genetic alteration in papillary thyroid carcinomas (PTCs). Transgenic mice overexpressing BRAF(V600E) in their thyroids under control of the thyroglobulin promoter (Tg-BRAF2 mice) developed invasive PTCs with high penetrance. However, these mice showed elevated thyrotropin (TSH) levels, which also stimulate the proliferation of thyrocytes and tumorigenesis. The purpose of the present study was to investigate how TSH signaling cooperates with BRAF(V600E) in the process of thyroid carcinogenesis.
We crossed Tg-BRAF2 mice with TSH receptor knockout (TshR(-/-)) mice. Four genetically distinct mice groups-Braf(wt)/TshR(+/-) (group 1), Braf(wt)/TshR(-/-) (group 2), Tg-BRAF2/TshR(+/-) (group 3), and Tg-BRAF2/TshR(-/-) (group 4)--were sacrificed at 12 and 24 weeks of age. We performed histopathological analysis. Genomic instability was evaluated by immunofluorescence for p53-binding protein 1 (53BP1) and γH2AX. Invasiveness and genomic instability were also evaluated using thyroid PCCL3 cells expressing BRAF(V600E).
Groups 3 and 4 developed distinct neoplasias comparable to human PTCs. Group 3 developed typically larger, more aggressive, invasive tumors compared to group 4. The frequency of 53BP1 and γH2AX foci-indicators of genomic instability--in group 3 was higher than that in group 4. TSH also enhanced invasiveness and genomic instability in PCCL3 cells with BRAF(V600E) expression.
These data demonstrate that the TSH signaling confers more aggressive features in BRAF(V600E)-induced thyroid tumors in mice. This might be due, in part, to accelerated genomic instability.
BRAF（V600E）突变是甲状腺乳头状癌（PTC）中最常见的基因改变。在甲状腺球蛋白启动子控制下甲状腺中过表达BRAF（V600E）的转基因小鼠（Tg - BRAF2小鼠）会发生具有高侵袭性的PTC，且发生率高。然而，这些小鼠促甲状腺激素（TSH）水平升高，而TSH也会刺激甲状腺细胞增殖和肿瘤发生。本研究的目的是探究TSH信号在甲状腺癌发生过程中如何与BRAF（V600E）协同作用。
我们将Tg - BRAF2小鼠与促甲状腺激素受体敲除（TshR（- / -））小鼠杂交。在12周龄和24周龄时处死四个基因不同的小鼠组——Braf（野生型）/TshR（+ / -）（第1组）、Braf（野生型）/TshR（- / -）（第2组）、Tg - BRAF2/TshR（+ / -）（第3组）和Tg - BRAF2/TshR（- / -）（第4组）。我们进行了组织病理学分析。通过对p53结合蛋白1（53BP1）和γH2AX进行免疫荧光评估基因组不稳定性。还使用表达BRAF（V600E）的甲状腺PCCL3细胞评估侵袭性和基因组不稳定性。
第3组和第4组发生了与人类PTC相当的不同肿瘤。与第4组相比，第3组通常形成更大、更具侵袭性的肿瘤。第3组中53BP1和γH2AX病灶（基因组不稳定性指标）的频率高于第4组。TSH还增强了表达BRAF（V600E）的PCCL3细胞的侵袭性和基因组不稳定性。
这些数据表明，TSH信号在小鼠BRAF（V600E）诱导的甲状腺肿瘤中赋予了更具侵袭性的特征。这可能部分归因于基因组不稳定性加速。
