Instituto de Investigaciones Biomédicas "Alberto Sols," Consejo Superior Investigaciones Científicas, and Universidad Autónoma de Madrid (CSIC-UAM), Madrid, Spain.
Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain.
Thyroid. 2021 Jun;31(6):912-921. doi: 10.1089/thy.2020.0297. Epub 2020 Dec 9.
DICER1 plays a central role in microRNA biogenesis and functions as a tumor suppressor in thyroid cancer, which is the most frequent endocrine malignancy with a rapidly increasing incidence. Thyroid cancer progression is associated with loss of cell differentiation and reduced expression of thyroid differentiation genes and response to thyrotropin (TSH). Here we investigated whether a molecular link exists between DICER1 and thyroid differentiation pathways. We used bioinformatic tools to search for transcription factor binding sites in the promoter. DICER1, NKX2-1, PAX8, and CREB expression levels were evaluated by gene and protein expression and by interrogation of The Cancer Genome Atlas (TCGA) thyroid cancer data. Transcription factor binding and activity were assayed by chromatin immunoprecipitation, band-shift analysis, and promoter-reporter gene activity. Gene-silencing and overexpression approaches were used to elucidate the functional link between DICER1 and differentiation. We identified binding sites for NKX2-1 and CREB within the promoter and found that both transcription factors are functional in thyroid cells. TSH induced expression in differentiated thyroid cells, at least in part, through the cAMP/PKA/CREB pathway. TCGA analysis revealed a significant positive correlation between CREB and DICER1 expression in human thyroid tumors. NKX2-1 overexpression increased promoter activity and expression , and this was significantly greater in the presence of CREB and/or PAX8. Gain- and loss-of-function assays revealed that DICER1 regulates NKX2-1 expression in thyroid tumor cells and , thus establishing a positive feedback loop between both proteins. We also found a positive correlation between NKX2-1 and DICER1 expression in human thyroid tumors. DICER1 silencing decreased PAX8 expression and, importantly, the expression and activity of the sodium iodide symporter, which is essential for the diagnostic and therapeutic use of radioiodine in thyroid cancer. The differentiation transcription factors NKX2.1, PAX8, and CREB act in a positive feedback loop with DICER1. As the expression of these transcription factors is markedly diminished in thyroid cancer, our findings suggest that DICER1 downregulation in this cancer is mediated, at least partly, through impairment of its transcription.
DICER1 在 microRNA 生物发生中发挥核心作用，并作为甲状腺癌的肿瘤抑制因子发挥作用，甲状腺癌是最常见的内分泌恶性肿瘤，发病率迅速上升。甲状腺癌的进展与细胞分化丧失和甲状腺分化基因表达减少以及对促甲状腺激素 (TSH) 的反应有关。在这里，我们研究了 DICER1 是否与甲状腺分化途径之间存在分子联系。我们使用生物信息学工具在启动子中搜索转录因子结合位点。通过基因和蛋白质表达以及对癌症基因组图谱 (TCGA) 甲状腺癌数据的查询来评估 DICER1、NKX2-1、PAX8 和 CREB 的表达水平。通过染色质免疫沉淀、带移位分析和启动子报告基因活性来检测转录因子结合和活性。使用基因沉默和过表达方法来阐明 DICER1 与分化之间的功能联系。我们确定了 NKX2-1 和 CREB 在启动子内的结合位点，并且发现这两种转录因子在甲状腺细胞中均具有功能。TSH 通过 cAMP/PKA/CREB 途径诱导分化的甲状腺细胞中的表达。TCGA 分析显示在人类甲状腺肿瘤中，CREB 与 DICER1 的表达呈显著正相关。NKX2-1 过表达增加启动子活性和表达，并且在存在 CREB 和/或 PAX8 时显着增加。增益和失能测定表明，DICER1 调节甲状腺肿瘤细胞中的 NKX2-1 表达，从而在这两种蛋白质之间建立了正反馈回路。我们还发现人类甲状腺肿瘤中 NKX2-1 和 DICER1 的表达呈正相关。DICER1 沉默降低了 PAX8 的表达，重要的是，降低了钠碘转运体的表达和活性，而钠碘转运体对于放射性碘在甲状腺癌中的诊断和治疗至关重要。分化转录因子 NKX2.1、PAX8 和 CREB 与 DICER1 形成正反馈回路。由于这些转录因子在甲状腺癌中的表达明显降低，我们的研究结果表明，至少部分通过其转录的损害，下调 DICER1 在这种癌症中发生。
