MDM2 GENE AMPLIFICATION AND TRANSCRIPT LEVELS IN HUMAN SARCOMAS - RELATIONSHIP TO TP53 GENE STATUS
MDM2 GENE AMPLIFICATION AND TRANSCRIPT LEVELS IN HUMAN SARCOMAS - RELATIONSHIP TO TP53 GENE STATUS
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DOI：
10.1093/jnci/86.17.1297
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发表时间：
1994-09-07
期刊：
影响因子：
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通讯作者：
FODSTAD, O
中科院分区：
文献类型：
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作者：
FLORENES, VA;MAELANDSMO, GM;FODSTAD, O
背景：肿瘤抑制基因TP53的改变似乎与几种类型的人类癌症的发生和进展有关，包括不同组织学亚型的肉瘤。MDM2（小鼠双分钟2）基因编码一种核磷酸化蛋白，该蛋白可与突变型和野生型p53蛋白相互作用，从而以剂量依赖的方式抑制p53介导的转激活。最近有研究表明，mdm2和p53蛋白是一个自调节环的组成部分，其中mdm2基因被p53反激活。目的：我们的目的是检查MDM2在较大的肉瘤中扩增的频率，确定mRNA水平是否可以在肿瘤中升高而不伴有基因扩增，并将MDM2的发现与肿瘤的TP53状态联系起来。方法：从68例手术患者和26例裸鼠异种移植体中获得不同组织学亚型的肉瘤组织。此外，还研究了两种人肉瘤细胞系（OSA和U2OS）。肿瘤组织的基因组DNA。采用Southern-blot方法分离体外细胞系和外周血细胞，检测MDM2基因扩增情况。通过恒变性凝胶电泳分析肿瘤DNA在5、7、8外显子可能发生的TP53基因突变。为了确定MDM2和TP53 mRNA水平，采用Northern-blot分析。结果：10例肿瘤中检测到MDM2基因扩增，占10.3%。MDM2扩增和/或过表达仅在18例骨肉瘤中的2例（U2OS和OSA细胞系），20例恶性纤维组织细胞瘤（MFHs）中的1例，14例平滑肌肉瘤中未发现MDM2扩增和/或过表达，而在2例纤维肉瘤中的2例，6例恶性神经鞘瘤中的3例，19例脂肪肉瘤中的3例和1例血管外皮细胞瘤中均观察到这种改变。所有9例检查病例均发现MDM2过表达，3例未扩增的病例发现MDM2过表达。在12例（5例骨肉瘤、4例MFHs和3例平滑肌肉瘤）中检测到TP53突变，其中没有一例显示扩增，但有一例MDM2 mRNA水平升高。纤维肉瘤、恶性神经鞘瘤和脂肪肉瘤均无TP53突变。在没有基因突变的情况下，TP53 mRNA高表达的6个肉瘤也有MDM2 mRNA水平升高。结论：目前的数据进一步表明，由基因扩增或转录调节改变引起的MDM2表达水平升高参与了一些（但不是全部）肉瘤亚型的肿瘤进展。
Background: Alterations of the TP53 tumor suppressor gene appear to be implicated in the tumorigenesis and progression of several types of human cancer, including different histologic subtypes of sarcomas. The MDM2 (murine double minute-2) gene encodes a nuclear phosphoprotein that may interact with both mutant and wild-type p53 proteins, thereby inhibiting p53-mediated transactivation in a dose-dependent manner. Recently it has been suggested that mdm2 and p53 proteins are components of an autoregulatory loop in which the MDM2 gene is transactivated by p53. Purpose: Our purpose was to examine the frequency of MDM2 amplifications in larger panels of sarcomas, determine if the mRNA level could be elevated in tumors without concomitant gene amplification, and relate MDM2 findings to the TP53 status of the tumors. Methods: Sarcoma tissue of different histologic subtypes was obtained from 68 patients at the time of surgery and from 26 human xenografts in nude mice. In addition, two human sarcoma cell lines (OSA and U2OS) mere studied. Genomic DNA from tumor tissue. in vitro cell lines, and peripheral blood cells were isolated by Southern-blot analysis methods to determine MDM2 gene amplification. Tumor DNA was analyzed for possible TP53 gene mutations in exons 5, 7, and 8 by constant denaturing gel electrophoresis. To determine the MDM2 and TP53 mRNA levels, Northern-blot analysis was performed. Results: Amplification of the MDM2 gene was detected in 10 tumors (10.3%). Whereas MDM2 amplification and/or overexpression were found only in two (U2OS and OSA cell lines) of 18 osteosarcomas, one of 20 malignant fibrous histiocytomas (MFHs), and in none of 14 leiomyosarcomas, such alterations were observed in two of two fibrosarcomas, three of six malignant schwannomas, three of 19 liposarcomas, and in the one hemangiopericytoma examined. MDM2 overexpression was found in all nine examined cases with and in three turners without amplification. TP53 mutations were detected in 12 cases (five osteosarcomas, four MFHs, and three leiomyosarcomas), of which none showed amplification, but one had increased levels of MDM2 mRNA. None of the fibrosarcomas, malignant schwannomas, and liposarcomas examined had mutated TP53. The six sarcomas that showed high TP53 mRNA expression in the absence of gene mutation also had elevated levels of MDM2 mRNA. Conclusions: The present data provide further indications that increased MDM2 expression level, caused by gene amplification or altered regulation of transcription, is involved in tumor progression of some, but not all, sarcoma subtypes.