Spectrum of TERT promoter mutations and mechanisms of activation in thyroid cancer
Spectrum of TERT promoter mutations and mechanisms of activation in thyroid cancer
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DOI：
10.1002/cam4.2467
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发表时间：
2019-10-01
期刊：
影响因子：
4
通讯作者：
Nikiforov, Yuri E.
中科院分区：
文献类型：
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作者：
Panebianco, Federica;Nikitski, Alyaksandr, V;Nikiforov, Yuri E.
背景端粒酶逆转录酶(TERT)的重新激活是肿瘤发生中的重要事件。TERT启动子区域的两个热点突变c.-124C>；T(C228T)和c.-146C>；T(C250T)发生在包括甲状腺癌在内的各种癌症类型中。它们产生E-26(ETS)转录因子的从头结合位点，导致TERT转录增加。这项研究的目的是寻找新的TERT启动子突变和TERT在甲状腺癌中激活的其他机制。方法检测198例甲状腺乳头状癌、34例滤泡性甲状腺癌、40例赫氏细胞癌、14例低分化/间变性甲状腺癌和15例髓样甲状腺癌TERT基因-424bp~+碱基的突变情况。荧光素酶报告试验被用来从功能上表征已鉴定的改变。用TaqMan拷贝数分析方法分析TERT区的拷贝数变异(CNV)，并用荧光原位杂交(FISH)验证。结果在7%的PTC、18%的FTC、25%的肝癌和86%的PDTC/ATC中检测到热点c.-124C>；T和c.-146C>；T突变。一例PTC携带c.-124C>；A突变。此外，我们还发现了两个新的突变导致新的ETS结合基序的形成：c.-332C>；T在一个MTC中和c.-104_-83dup在一个PTC中。当使用荧光素酶报告系统进行检测时，这些基因改变以及其他检测到的突变导致TERT启动子活性显著增加。此外，5%的甲状腺肿瘤被发现有3个拷贝的TERT。结论本研究证实TERT基因启动子突变和CNV在晚期甲状腺癌中的发生率增加，并描述了TERT基因启动子的新的功能变化，包括点突变和小重复。这些突变，以及TERT拷贝数的改变，可能代表了甲状腺癌TERT激活的另一种机制。
Background Reactivation of telomerase reverse transcriptase (TERT) is an important event in cancer. Two hotspot mutations in the TERT promoter region, c.-124C > T (C228T) and c.-146C > T (C250T), occur in various cancer types including thyroid cancer. They generate de novo binding sites for E-twenty-six (ETS) transcription factors causing increased TERT transcription. The aim of this study was to search for novel TERT promoter mutations and additional mechanisms of TERT activation in thyroid cancer. Methods We studied 198 papillary thyroid carcinomas (PTCs), 34 follicular thyroid carcinomas (FTCs), 40 Hurthle cell carcinomas (HCCs), 14 poorly differentiated/anaplastic thyroid carcinomas (PDTC/ATC), and 15 medullary thyroid carcinomas (MTCs) for mutations in an -424 bp to +64 bp region of TERT. The luciferase reporter assay was used to functionally characterize the identified alterations. Copy number variations (CNVs) in the TERT region were analyzed using TaqMan copy number assay and validated with fluorescence in situ hybridization (FISH). Results We detected the hotspot c.-124C > T and c.-146C > T mutations in 7% PTC, 18% FTC, 25% HCC, and 86% PDTC/ATC. One PTC carried a c.-124C > A mutation. Furthermore, we identified two novel mutations resulting in the formation of de novo ETS-binding motifs: c.-332C > T in one MTC and c.-104_-83dup in one PTC. These genetic alterations, as well as other detected mutations, led to a significant increase in TERT promoter activity when assayed using luciferase reporter system. In addition, 5% of thyroid tumors were found to have >= 3 copies of TERT. Conclusions This study confirms the increased prevalence of TERT promoter mutations and CNV in advanced thyroid cancers and describes novel functional alterations in the TERT gene promoter, including a point mutation and small duplication. These mutations, as well as TERT copy number alterations, may represent an additional mechanism of TERT activation in thyroid cancer.