Cancer Genetics Laboratory, Kolling Institute, Royal North Shore Hospital, Sydney, Australia.
Northern Clinical School, University of Sydney, Sydney, Australia.
Thyroid. 2019 Nov;29(11):1623-1633. doi: 10.1089/thy.2018.0314. Epub 2019 Oct 29.
Co-occurrence of (telomerase reverse transcriptase) promoter (TERTp) mutations with / mutations is associated with significantly more aggressive thyroid cancer. TERTp mutations are hypothesized to generate binding sites for ETS transcription factors, which are themselves activated by BRAF/RAS-stimulated MEK-ERK activity. To date, a detailed study of this mechanism has been limited to only a few cancer types, and we hypothesized that ETS factors involved in TERTp activation could vary between different cancers. Here we sought to identify ETS factor(s) required for TERTp activation in thyroid cancer, using a combination of analyses of TCGA data, and experimentation using thyroid cell models analyzed by quantitative reverse transcription-PCR, immunoprecipitation (IP), chromatin IP, and gene reporter assays. We found that ETV5 was abundantly expressed in papillary thyroid cancers from the TCGA data set, and in thyroid cancer cell line models. Furthermore, ETV5 was found to preferentially bind to the -124 bp(T) TERTp allele and stimulate transcription in thyroid cancer cells devoid of GA binding protein transcription factor (GABP) activity. We also found that ETV5 functionally cooperates with the transcription factor FOXE1 to further enhance TERTp activity, a mechanism that may at least partially explain why represents a significant genetic determinant of thyroid cancer risk. ETS factors that activate mutant TERTp vary between cancer types, and here we show for the first time that ETV5 demonstrates mutant allele-specific affinity for TERTp in thyroid cancer, a property that has previously only been attributable to GABP.
（端粒酶逆转录酶）启动子（TERTp）突变与 / 突变的共存与侵袭性更强的甲状腺癌相关。TERTp 突变被假设产生 ETS 转录因子的结合位点，而 ETS 转录因子本身又被 BRAF/RAS 刺激的 MEK-ERK 活性激活。迄今为止，对这种机制的详细研究仅限于少数几种癌症类型，我们假设参与 TERTp 激活的 ETS 因子在不同的癌症之间可能有所不同。在这里，我们试图通过 TCGA 数据的综合分析，以及使用定量逆转录-PCR、免疫沉淀（IP）、染色质 IP 和基因报告基因分析的甲状腺细胞模型进行实验，来确定甲状腺癌中 TERTp 激活所需的 ETS 因子。我们发现，在 TCGA 数据集的甲状腺乳头状癌和甲状腺癌细胞系模型中，ETV5 大量表达。此外，发现 ETV5 优先结合-124 bp（T）TERTp 等位基因，并在缺乏 GA 结合蛋白转录因子（GABP）活性的甲状腺癌细胞中刺激 转录。我们还发现，ETV5 与转录因子 FOXE1 功能合作，进一步增强 TERTp 活性，这种机制至少部分解释了为什么 是甲状腺癌风险的重要遗传决定因素。激活突变 TERTp 的 ETS 因子在癌症类型之间存在差异，在这里我们首次表明，ETV5 在甲状腺癌中表现出对 TERTp 突变等位基因的特异性亲和力，而这种特性以前仅归因于 GABP。
