Franzoni Alessandra, Dima Mariavittoria, D'Agostino Maria, Puppin Cinzia, Fabbro Dora, Loreto Carla Di, Pandolfi Maura, Puxeddu Efisio, Moretti Sonia, Celano Marilena, Bruno Rocco, Filetti Sebastiano, Russo Diego, Damante Giuseppe
Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, Udine, Italy.
Thyroid. 2009 Mar;19(3):247-55. doi: 10.1089/thy.2008.0235.
Prohibitin (PHB) is a multifunctional protein that is localized in different intracellular sites. PHB may exert different roles in tumorigenesis, having either a permissive action on tumor growth or an oncosuppressor role, depending on the cellular context. The objective of this study was to evaluate PHB expression in normal thyroid tissues, thyroid follicular adenomas (FAs), and papillary thyroid carcinomas (PTCs).
PHB expression was analyzed by immunohistochemistry, Western blot, and quantitative reverse transcription polymerase chain reaction (RT-PCR). Transfections in the BCPAP and TPC-1 thyroid cancer cell lines were used to evaluate the PHB promoter activity.
In terms of protein and mRNA levels, normal tissues from patients with serum thyrotropin (TSH) values >0.8mU/L had PHB levels that were significantly reduced compared to specimens from patients with serum TSH values <0.5mU/L, suggesting that TSH exerts an inhibitory effect on PHB expression. Consistent with this was the finding that the presence of TSH was associated with low PHB levels in normal FRTL5 thyroid cells. Immunohistochemical analysis showed relatively low and high PHB expression in FAs and PTCs, respectively. PHB mRNA and protein overexpression, as assessed by quantitative RT-PCR and Western blot, was noted only in PTCs bearing the BRAF(V600E) mutation. Notably, cell transfection experiments suggested that presence of the BRAF(V600E) mutation may be associated to increase of the PHB promoter activity.
PHB is overexpressed in PTCs bearing the BRAF(V600E) mutation. We postulate that the presence of the BRAF(V600E) mutation increases PHB promoter activity and therefore potentially mediates effects of this mutation on the behavior of BRAF(V600E) positive PTCs.
prohibitin（PHB）是一种多功能蛋白，定位于不同的细胞内位点。根据细胞环境的不同，PHB在肿瘤发生过程中可能发挥不同的作用，对肿瘤生长具有促进作用或发挥抑癌作用。本研究的目的是评估PHB在正常甲状腺组织、甲状腺滤泡性腺瘤（FAs）和甲状腺乳头状癌（PTCs）中的表达情况。
通过免疫组织化学、蛋白质印迹法和定量逆转录聚合酶链反应（RT-PCR）分析PHB的表达。利用BCPAP和TPC-1甲状腺癌细胞系转染来评估PHB启动子活性。
在蛋白质和mRNA水平方面，血清促甲状腺激素（TSH）值>0.8mU/L患者的正常组织中PHB水平，与血清TSH值<0.5mU/L患者的标本相比显著降低，这表明TSH对PHB表达具有抑制作用。与此一致的是，在正常FRTL5甲状腺细胞中发现TSH的存在与低PHB水平相关。免疫组织化学分析显示，PHB在FAs中表达相对较低，而在PTCs中表达较高。通过定量RT-PCR和蛋白质印迹法评估，仅在携带BRAF（V600E）突变的PTCs中观察到PHB mRNA和蛋白质的过表达。值得注意的是，细胞转染实验表明，BRAF（V600E）突变的存在可能与PHB启动子活性增加有关。
PHB在携带BRAF（V600E）突变的PTCs中过表达。我们推测，BRAF（V600E）突变的存在增加了PHB启动子活性，因此可能介导该突变对BRAF（V600E）阳性PTCs行为的影响。
