Jang Taichang, Savarese Todd, Low Hoi Pang, Kim Sunchin, Vogel Hannes, Lapointe David, Duong Timothy, Litofsky N Scott, Weimann James M, Ross Alonzo H, Recht Lawrence
Department of Neurology and Clinical Neurosciences, Stanford University Medical School, Stanford, California 94305-5487, USA.
Am J Pathol. 2006 May;168(5):1676-85. doi: 10.2353/ajpath.2006.050400.
To better study early events in glioma genesis, markers that reliably denote landmarks in glioma development are needed. In the present study, we used microarray analysis to compare the gene expression patterns of magnetic resonance imaging (MRI)-localized N-ethyl-N-nitrosourea (ENU)-induced tumors in rat brains with those of uninvolved contralateral side and normal brains. Our analysis identified osteopontin (OPN) as the most up-regulated gene in glioma. Using immunohistochemistry we then confirmed OPN expression in every tumor examined (n = 17), including those with diameters as small as 300 mum. By contrast, no OPN immunostaining was seen in normal brain or in brains removed from ENU-exposed rats before the development of glioma. Further studies confirmed that OPN was co-localized exclusively in intratumoral glial fibrillary acidic protein-expressing cells and was notably absent from nestin-expressing ones. In conjunction with this, we confirmed that both normal neurosphere cells and ENU-im-mortalized subventricular zone/striatal cells produced negligible amounts of OPN compared to the established rat glioma cell line C6. Furthermore, inducing OPN expression in an immortalized cell line increased cell proliferation. Based on these findings, we conclude that OPN overexpression in ENU-induced gliomas occurs within a specific subset of intratumoral glial fibrillary acidic protein-positive cells and becomes evident at the stage of tumor progression.
为了更好地研究胶质瘤发生的早期事件，需要能够可靠地标记胶质瘤发展过程中关键节点的标志物。在本研究中，我们使用微阵列分析来比较磁共振成像（MRI）定位的N-乙基-N-亚硝基脲（ENU）诱导的大鼠脑肿瘤与未受影响的对侧脑组织及正常脑组织的基因表达模式。我们的分析确定骨桥蛋白（OPN）是胶质瘤中上调最为明显的基因。然后，我们使用免疫组织化学方法证实了在每一个检测的肿瘤（n = 17）中均有OPN表达，包括直径小至300微米的肿瘤。相比之下，在正常脑组织或在胶质瘤发生前从ENU暴露大鼠取出的脑组织中未观察到OPN免疫染色。进一步的研究证实，OPN仅共定位于肿瘤内表达胶质纤维酸性蛋白的细胞中，而表达巢蛋白的细胞中则明显没有。与此同时，我们证实，与已建立的大鼠胶质瘤细胞系C6相比，正常神经球细胞和ENU永生化的脑室下区/纹状体细胞产生的OPN量可忽略不计。此外，在永生化细胞系中诱导OPN表达会增加细胞增殖。基于这些发现，我们得出结论，ENU诱导的胶质瘤中OPN的过表达发生在肿瘤内胶质纤维酸性蛋白阳性细胞的特定亚群中，并在肿瘤进展阶段变得明显。
