Carta Claudio, Moretti Sonia, Passeri Lucia, Barbi Flavia, Avenia Nicola, Cavaliere Antonio, Monacelli Massimo, Macchiarulo Antonio, Santeusanio Fausto, Tartaglia Marco, Puxeddu Efisio
Dipartimento di Biologia Cellulare e Neuroscienze, Istituto Superiore di Sanità, Rome, Italy.
Clin Endocrinol (Oxf). 2006 Jan;64(1):105-9. doi: 10.1111/j.1365-2265.2005.02401.x.
The genes RET and RAS, and more recently BRAF, have been shown to be frequently mutated in human papillary thyroid carcinomas (PTC). The aim of this study was to genotype for these mutations a cohort of thyroid tumours collected at our institutions.
Thyroid tumours removed from 51 subjects were analysed, including 43 PTC and 8 non-PTC tumours [3 follicular adenomas (FA), 4 follicular carcinomas (FTC) and 1 anaplastic carcinoma (AC)].
RET/PTC1 and RET/PTC3 expression was evaluated by reverse transcriptase-polymerase chain reaction, whereas screening of BRAF (exon 15) and RAS (HRAS, KRAS2 and NRAS) mutations were performed, respectively, by single strand conformation polymorphism and denaturing high-pressure liquid chromatography.
RET/PTC expressions was positive in 5/43 (11.6%) PTC and in none of the non-PTC tumour. Similarly, BRAF mutations were positive only in PTC, but with a higher prevalence (24/43 positives, 55.8%). All but one BRAF mutation resulted in the prototypic substitution of valine 600 with a glutamic acid. In one case, a somatic in-frame insertion of three bases at codon 599 resulted in the insertion of an additional valine. RET/PTC expression and BRAF mutations were mutually exclusive. Screening of the RAS gene allowed identification of oncogenic mutations in 1/3 (33.3%) FA and 3/4 (75%) FTC. None of the PTCs was positive for RAS.
These data indicate that BRAF mutations are the most frequent genetic event in PTC and that RAS mutations, besides being a genetic hallmark of follicular tumours, are rare or completely absent in PTC from our area. Together, BRAF mutations and rarer RET rearrangements accounted for a genetic event in two-thirds of PTCs. This study showed a novel and presumably oncogenic mutation of BRAF, which is BRAF(V599Ins).
已证实RET和RAS基因，以及最近发现的BRAF基因，在人甲状腺乳头状癌（PTC）中经常发生突变。本研究的目的是对我们机构收集的一组甲状腺肿瘤进行这些突变的基因分型。
分析了从51名受试者身上切除的甲状腺肿瘤，包括43例PTC和8例非PTC肿瘤[3例滤泡性腺瘤（FA）、4例滤泡性癌（FTC）和1例未分化癌（AC）]。
通过逆转录聚合酶链反应评估RET/PTC1和RET/PTC3的表达，而分别通过单链构象多态性和变性高压液相色谱法对BRAF（第15外显子）和RAS（HRAS、KRAS2和NRAS）突变进行筛查。
RET/PTC表达在5/43（11.6%）的PTC中呈阳性，在非PTC肿瘤中均为阴性。同样，BRAF突变仅在PTC中呈阳性，但发生率更高（24/43阳性，55.8%）。除一例BRAF突变外，其余均导致缬氨酸600被谷氨酸原型替代。在一例中，第599密码子处三个碱基的体细胞框内插入导致额外缬氨酸的插入。RET/PTC表达和BRAF突变相互排斥。对RAS基因的筛查发现1/3（33.3%）的FA和3/4（75%）的FTC存在致癌突变。PTC中无一例RAS呈阳性。
这些数据表明，BRAF突变是PTC中最常见的基因事件，并且RAS突变除了是滤泡性肿瘤的基因标志外，在我们地区的PTC中很少见或完全不存在。BRAF突变和罕见的RET重排共同构成了三分之二PTC中的基因事件。本研究显示了一种新的、可能致癌的BRAF突变，即BRAF（V599Ins）。
