Bruggers C S, Tai K F, Murdock T, Sivak L, Le K, Perkins S L, Coffin C M, Carroll W L
Department of Pediatrics, Center for Children at the Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City 84112, USA.
J Pediatr Hematol Oncol. 1998 Jan-Feb;20(1):18-25. doi: 10.1097/00043426-199801000-00003.
The purpose of this study was to determine the incidence of c-Myc protein expression in medulloblastoma/primitive neuroectodermal tumor (MB/PNET) and to identify mechanisms in addition to c-myc gene amplification that lead to increased protein expression.
We analyzed c-myc gene copy number, mRNA level and protein expression in a panel of MB/PNET cell lines. C-Myc protein levels were assessed in tumor specimens and cell lines using immunohistochemical staining with a c-Myc-specific monoclonal antibody.
Southern analysis confirmed c-myc gene amplification in the D425 MED cell line and re-arrangement of one allele in D283 MED, which was analyzed further and appeared to represent a small deletion 3' of exon 3. C-myc transcript levels were dramatically elevated in both lines. Using a c-myc probe, fluorescence in situ hybridization (FISH) showed c-myc present in 3 tandem copies at 8q24 in D283 MED and multiple copies as double minutes in D425 MED. Immunohistochemistry showed c-Myc protein expression in 9 of 10 tumors and all cell lines, regardless of gene amplification status or level of mRNA expression.
c-Myc protein expression is common in MB/PNET tumor specimens and cell lines. Elevated protein levels are observed in the absence of amplification, suggesting that multiple mechanisms of c-myc dysregulation may be involved in MB/PNET. These studies support a role for c-Myc in the development of this common childhood tumor.
本研究旨在确定髓母细胞瘤/原始神经外胚层肿瘤（MB/PNET）中c-Myc蛋白表达的发生率，并确定除c-myc基因扩增外导致蛋白表达增加的机制。
我们分析了一组MB/PNET细胞系中的c-myc基因拷贝数、mRNA水平和蛋白表达。使用c-Myc特异性单克隆抗体通过免疫组织化学染色评估肿瘤标本和细胞系中的C-Myc蛋白水平。
Southern分析证实D425 MED细胞系中存在c-myc基因扩增，D283 MED中一个等位基因发生重排，对其进一步分析后发现这似乎代表外显子3 3'端的一个小缺失。两个细胞系中的c-myc转录水平均显著升高。使用c-myc探针，荧光原位杂交（FISH）显示D283 MED中8q24处有3个串联拷贝的c-myc，D425 MED中有多个拷贝呈双微体形式。免疫组织化学显示，在10个肿瘤中的9个以及所有细胞系中均有c-Myc蛋白表达，无论基因扩增状态或mRNA表达水平如何。
c-Myc蛋白表达在MB/PNET肿瘤标本和细胞系中很常见。在无扩增的情况下也观察到蛋白水平升高，这表明c-myc失调的多种机制可能参与了MB/PNET的发生。这些研究支持c-Myc在这种常见儿童肿瘤发生中的作用。
