Human Cancer Genetics Program, Comprehensive Cancer Center, The Ohio State University, 804 Biomedical Research Tower, 460 West 12th Avenue, Columbus, Ohio 43210, USA.
J Clin Endocrinol Metab. 2011 Mar;96(3):E546-53. doi: 10.1210/jc.2010-1594. Epub 2010 Dec 15.
Loss of the thyroid hormone receptor is common in tumors. In mouse models, a truncated THRB gene leads to thyroid cancer. Previously, we observed up-regulation of the expression of eight microRNAs (miRs) in papillary thyroid carcinoma (PTC) tumors.
Our objective was to determine whether THRB might be inhibited by miRs up-regulated in PTC.
The potential binding of miR to the 3'-untranslated region of THRB was analyzed in silico. Direct inhibition by miRs binding to the cloned 3'-untranslated region of THRB was evaluated using luciferase assays. Inhibition of endogenous THRB and its target genes (DIO1 and APP) was examined in cell lines transfected by pre-miRs. The impact on thyroid hormone response element (TRE) was evaluated in promoter assays. Correlations between the expression of THRB and miRs was evaluated in 13 PTC tumor/normal tissue pairs.
THRB contains binding sites for the top seven miRs up-regulated in PTC (P = 0.0000002). Direct interaction with THRB was shown for miR-21 and miR-146a. We observed lower levels of THRB transcripts in cell lines transfected with miR-21, -146a, and -221 (down-regulation of 37-48%; P < 0.0001), but not with miR-181a. THRB protein was suppressed down to 10-28% by each of four miRs. Concomitant expression of DIO1 and APP was affected (down-regulation of 32-66%, P < 0.0034 and up-regulation of 48-57%, P < 0.0002, respectively). All four miRs affected TRE activity in promoter assays. Down-regulation of luciferase occurred after transfection with pTRE-TK-Luc construct and each of four miRs. The analysis of tumor/normal tissue pairs revealed down-regulation of THRB in 11 of 13 pairs (1.3- to 9.1-fold), and up-regulation of miR-21, -146a, -181a, and -221 in almost all pairs.
MiRs up-regulated in PTC tumors directly inhibit the expression of THRB, an important tumor suppressor gene.
甲状腺激素受体的缺失在肿瘤中很常见。在小鼠模型中，截断的 THRB 基因导致甲状腺癌。先前，我们观察到甲状腺乳头状癌（PTC）肿瘤中八种 microRNAs（miRs）的表达上调。
我们的目的是确定 PTC 中上调的 miRs 是否可能抑制 THRB。
在计算机中分析了 miR 与 THRB 3'-UTR 的潜在结合。通过荧光素酶测定评估 miR 与克隆的 THRB 3'-UTR 直接结合的抑制作用。通过转染 pre-miRs 的细胞系检查内源性 THRB 及其靶基因（DIO1 和 APP）的抑制作用。在启动子测定中评估对甲状腺激素反应元件（TRE）的影响。在 13 对 PTC 肿瘤/正常组织中评估 THRB 与 miRs 之间的表达相关性。
THRB 含有 PTC 中上调的前七种 miR 的结合位点（P = 0.0000002）。直接与 THRB 相互作用的是 miR-21 和 miR-146a。我们观察到转染 miR-21、-146a 和 -221 的细胞系中 THRB 转录本水平降低（下调 37-48%，P < 0.0001），但 miR-181a 没有。四种 miR 中的每一种都将 THRB 蛋白抑制至 10-28%。同时表达 DIO1 和 APP 受到影响（下调 32-66%，P < 0.0034 和上调 48-57%，P < 0.0002，分别）。四种 miR 均在启动子测定中影响 TRE 活性。在用 pTRE-TK-Luc 构建体和四种 miR 中的每一种转染后，荧光素酶活性下降。对肿瘤/正常组织对的分析显示，13 对中的 11 对（1.3-9.1 倍）中 THRB 下调，几乎所有对中 miR-21、-146a、-181a 和 -221 上调。
PTC 肿瘤中上调的 miRs 直接抑制重要的肿瘤抑制基因 THRB 的表达。
