Involvement of Wnt signaling pathway in murine medulloblastoma induced by human neurotropic JC virus
Involvement of Wnt signaling pathway in murine medulloblastoma induced by human neurotropic JC virus
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DOI：
10.1038/sj.onc.1204670
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发表时间：
2001-08-09
期刊：
影响因子：
8
通讯作者：
Khalili, K
中科院分区：
文献类型：
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作者：
Gan, DD;Reiss, K;Khalili, K
通过使用人类嗜神经性多瘤病毒 JCV 的早期基因组，我们创造了转基因动物，这些动物能够发育出模拟人类髓母细胞瘤的小脑原始神经外胚层肿瘤。在一些（但不是全部）肿瘤细胞中发现了 T 抗原的表达，对源自肿瘤群体的克隆细胞系的检查表明，与 T 抗原阴性细胞相比，表达 T 抗原的细胞的致瘤性增强。考虑到早期关于 β-连环蛋白与人髓母细胞瘤可能相关的概念，我们研究了这两个细胞群中 Wnt 信号通路的各个组成部分，包括 β-连环蛋白、其伴侣转录因子 LEF-1 及其下游靶基因 c-myc。细胞的免疫组织化学染色显示 T 抗原阳性细胞中 β-连环蛋白的核外观增强。 Western blot 结果显示，与 T 抗原阴性细胞相比，T 抗原阳性细胞中的 β-连环蛋白和 LEF-1 水平较高。 T 抗原阳性细胞核提取物中 LEF-1 表达水平的增强与该蛋白 DNA 结合活性的增加相关。 Northern 和 Western blot 分析结果显示，T 抗原阳性细胞中 RNA 和蛋白质水平的 c-myc 表达水平均有所增强。这些观察结果证实了转染研究的结果，表明 JCV T 抗原具有刺激 c-myc 启动子活性的能力。此外，共转染实验表明，肿瘤细胞中c-myc和T抗原蛋白的量可能决定这些细胞中JCV早期启动子的活性。鉴于最近关于 JCV 与人类髓母细胞瘤关联的发现，这些观察结果很有趣，并且表明 JCV 和 Wnt 通路之间的通讯可能是这些肿瘤发生中的重要事件。
By using the early genome of the human neurotropic polyomavirus, JCV, we have created transgenic animals that develop cerebellar primitive neuroectodermal tumors which model human medulloblastoma. Expression of T-antigen was found in some, but not all, tumor cells, and examination of the clonal cell lines derived from the tumor population showed enhanced tumorigenicity of cells expressing T-antigen in comparison to T-antigen negative cells. Considering the earlier notion on the potential involvement of beta -catenin with human medulloblastoma, we investigated various components of the Wnt signaling pathway including beta -catenin, its partner transcription factor, LEF-1, and their downstream target gene c-myc in these two cell populations. Immunohistochemical staining of the cells revealed enhanced nuclear appearance of beta -catenin in T-antigen positive cells. Results from Western blot showed higher levels of beta -catenin and LEF-1 in T-antigen positive cells in comparison to those in T-antigen negative cells. The enhanced level of LEF-1 expression correlated with the increase in DNA binding activity of this protein in nuclear extracts of T-antigen positive cells. Results from Northern and Western blot analyses revealed that the level of c-myc expression is augmented both at the RNA and protein levels in T-antigen positive cells. These observations corroborated results from transfection studies indicating the ability of JCV T-antigen to stimulate c-myc promoter activity. Further, co-transfection experiments revealed that the amount of c-myc and T-antigen protein in tumor cells may dictate the activity of JCV early promoter in these cells. These observations are interesting in light of recent discoveries on the association of JCV with human medulloblastoma and suggest that communication between JCV and the Wnt pathway may be an important event in the genesis of these tumors.