Song Jianlu, Qiu Wangwang, Deng Xianzhao, Qiu Zhongling, Fan Youben, Yang Zhili
Department of Thyroid Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital Shanghai 200233, China.
Department of Nuclear Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital Shanghai 200233, China.
Am J Cancer Res. 2018 Sep 1;8(9):1847-1855. eCollection 2018.
Mutation profiles of advanced radioactive iodine (RAI)-refractory differentiated thyroid cancer have revealed the pathogenic roles of the established oncogenic mutations of BRAF and PI3KCA, but the involvement of other genes is presently unknown. In the present study, we performed whole-exome sequencing on 10 tissue samples of metastases of RAI-refractory differentiated thyroid cancers and identified a recurrent hot-spot mutation (c.1924G>T) in the gene, which codes for Ras guanine nucleotide-releasing protein 3. This mutation was found to occur at a high frequency (20%) in samples of metastases of RAI-refractory differentiated thyroid cancers compared with other types of thyroid cancer. Overexpression of mutant RasGRP3 significantly promoted cell proliferation, migration, and invasiveness of 8505C and BHT101 cells compared with cells transfected with wild-type or an empty vector. In addition, mutant RasGRP3 decreased the expression of sodium iodide symporter (NIS) and thyroid-stimulating hormone receptor (TSHR), reduced the iodine uptake ability, and increased Akt phosphorylation in thyroid cancer cells. Finally, we showed that LY294002, an inhibitor of PI3K/Akt signaling, attenuated the effects of mutant RasGRP3 on thyroid cancer cells. Thus, our study revealed that the c.1924G>T hot-spot mutation in is a more frequent genetic alteration in metastases of RAI-refractory differentiated thyroid cancer. This mutant RasGRP3 activated the Akt pathway, promoted thyroid cancer cell proliferation and invasion, and reduced NIS expression and the iodine uptake ability.
晚期放射性碘（RAI）难治性分化型甲状腺癌的突变谱揭示了BRAF和PI3KCA等已确定的致癌突变的致病作用，但其他基因的参与情况目前尚不清楚。在本研究中，我们对10例RAI难治性分化型甲状腺癌转移灶的组织样本进行了全外显子测序，并在编码Ras鸟嘌呤核苷酸释放蛋白3的基因中鉴定出一个反复出现的热点突变（c.1924G>T）。与其他类型的甲状腺癌相比，该突变在RAI难治性分化型甲状腺癌转移灶样本中出现的频率较高（20%）。与转染野生型或空载体的细胞相比，突变型RasGRP3的过表达显著促进了8505C和BHT101细胞的增殖、迁移和侵袭能力。此外，突变型RasGRP3降低了甲状腺癌细胞中钠碘同向转运体（NIS）和促甲状腺激素受体（TSHR）的表达，降低了碘摄取能力，并增加了Akt磷酸化。最后，我们发现PI3K/Akt信号通路抑制剂LY294002减弱了突变型RasGRP3对甲状腺癌细胞的影响。因此，我们的研究表明，该基因中的c.1924G>T热点突变在RAI难治性分化型甲状腺癌转移灶中是一种更常见的基因改变。这种突变型RasGRP3激活了Akt通路，促进了甲状腺癌细胞的增殖和侵袭，并降低了NIS表达和碘摄取能力。
