Laboratory for Cellular and Molecular Thyroid Research, Division of Endocrinology and Metabolism, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Biochem Biophys Res Commun. 2010 Mar 12;393(3):555-9. doi: 10.1016/j.bbrc.2010.02.095. Epub 2010 Feb 18.
Mutations in the genes for isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) have been recently identified in glioblastoma. In the present study, we investigated IDH1 and IDH2 mutations in follicular thyroid cancer (FTC) and anaplastic thyroid cancer (ATC), with the latter, like glioblastoma, having a rapidly aggressive and lethal clinical course. By direct genomic DNA sequencing, we analyzed exon 4 of the IDH1 and IDH2 genes that harbored the mutation hot spots codon 132 and 172 of the two genes in glioblastoma, respectively, in 12 thyroid cancer cell lines, 20 FTC, and 18 ATC tumor samples. A novel homozygous G367A IDH1 mutation, resulting in a G123R amino acid change in codon 123, was identified in a case of ATC. A previously described IDH1 V71I mutation was found in a case of FTC and a case of ATC and no mutations were found in the cell lines. The overall prevalence of mutations was thus 1/20 (5%) in FTC and 2/18 (11%) in ATC. We did not find mutation in the IDH2 gene in these thyroid cancer cell lines and tumor samples. Sequence alignment analysis of 16 species revealed that the novel IDH1 G123R mutation was located in a highly conserved region, raising the possibility of a serious functional consequence as could also be predicted by the occurrence of a positively charged amino acid from this mutation. To test this, we created a G123R mutant by site-directed mutagenesis and demonstrated a decreased enzymatic activity of IDH1, similar to the expected reduction in the enzymatic activity of the previously described R132H IDH1 mutant measured as a control. Thus, functionally relevant IDH1 mutations can also occur in thyroid cancer, particularly ATC, suggesting a potential tumorigenic role of the IDH1 system that could represent a new therapeutic target for thyroid cancer.
IDH1 和 IDH2 基因突变最近在胶质母细胞瘤中被发现。在本研究中，我们研究了滤泡状甲状腺癌（FTC）和间变性甲状腺癌（ATC）中的 IDH1 和 IDH2 突变，后者与胶质母细胞瘤一样，具有快速侵袭性和致命的临床病程。通过直接基因组 DNA 测序，我们分析了 IDH1 和 IDH2 基因的exon 4，这些基因分别携带有胶质母细胞瘤中突变热点密码子 132 和 172 的突变，在 12 种甲状腺癌细胞系、20 例 FTC 和 18 例 ATC 肿瘤样本中进行了分析。在一例 ATC 病例中发现了一种新的 IDH1 同源纯合 G367A 突变，导致密码子 123 中的 G123R 氨基酸改变。在一例 FTC 和一例 ATC 病例中发现了先前描述的 IDH1 V71I 突变，而在细胞系中未发现突变。因此，突变在 FTC 中的总发生率为 20 例中的 1 例（5%），在 ATC 中为 18 例中的 2 例（11%）。在这些甲状腺癌细胞系和肿瘤样本中，我们没有发现 IDH2 基因的突变。对 16 个物种的序列比对分析表明，新型 IDH1 G123R 突变位于高度保守区域，这可能会导致严重的功能后果，也可以通过这种突变产生的带正电荷的氨基酸来预测。为了验证这一点，我们通过定点突变创建了 G123R 突变体，并证明了 IDH1 的酶活性降低，与作为对照测量的先前描述的 R132H IDH1 突变体的酶活性预期降低相似。因此，甲状腺癌，特别是 ATC 中也可能发生功能性相关的 IDH1 突变，提示 IDH1 系统可能具有潜在的致癌作用，可为甲状腺癌提供新的治疗靶点。
