Expression data from U373 cells expressing EGFP, MAML1-dn and DTX1-myc

Glioblastoma multiforme (GBM) is the most malignant and most common tumor of the central nervous system characterized by rapid growth and extensive tissue infiltration. GBM results in more years of life lost than any other cancer type. Notch signaling has been implicated in GBM pathogenesis through several modes of action. Inhibition of Notch leads to a reduction of cancer-initiating cells in gliomas and reduces proliferation and migration. Deltex1 (DTX1) is part of an alternative Notch signaling pathway distinct from the canonical MAML1/RBP-Jκ-mediated cascade. In this study, we show that DTX1 activates both the RTK/PI3K/PKB as well as the MAPK/ERK pathway. Moreover, we found the anti-apoptotic factor Mcl-1 to be induced by DTX1. In accordance with this, the clonogenic potential and proliferation rates of glioma cell lines correlated with DTX1 levels. DTX1 knock down mitigated the tumorigenic potential in vivo, and overexpression of DTX1 increased cell migration and invasion of tumor cells accompanied by an elevation of the pro-migratory factors PKBβ and Snail1. Microarray gene expression analysis identified a DTX1-specific transcriptional program - including microRNA-21 - which is distinct from the canonical Notch signaling. We propose the alternative Notch pathway via DTX1 as oncogenic factor in malignant glioma and found low DTX1 expression levels to correlate with prolonged survival of GBM and early breast cancer patients in open source databases. We generated human glioma U373 cell lines stably expressing Enhanced Green Fluorescent Protein (EGFP), human Deltex1-Myc Tag (DTX1-myc), or Master Mind Like 1 - dominant negative (MAML1-dn) to compare differences in overall gene expression. We included 3x EGFP control samples, 3x DTX1-myc, and 3 MAML1-dn samples.

多形性胶质母细胞瘤（Glioblastoma multiforme, GBM）是中枢神经系统中恶性程度最高且最为常见的肿瘤，以快速生长与广泛组织浸润为典型特征。相较于其他任何癌种，GBM造成的寿命损失年数最多。Notch信号通路已被证实通过多种作用模式参与GBM的发病过程。抑制Notch信号可减少胶质瘤中的肿瘤起始细胞，并降低细胞增殖与迁移能力。Deltex1（DTX1）是区别于经典MAML1/RBP-Jκ介导级联反应的非典型Notch信号通路的组成组分。本研究证实，DTX1可同时激活RTK/PI3K/PKB通路与MAPK/ERK通路。此外，我们发现抗凋亡因子Mcl-1的表达可被DTX1诱导。与之相一致的是，胶质瘤细胞系的克隆形成潜能与增殖速率均与DTX1的表达水平呈正相关。敲低DTX1可在体内削弱肿瘤的致瘤潜能，而DTX1过表达则可增强肿瘤细胞的迁移与侵袭能力，并伴随促迁移因子PKBβ与Snail1的表达上调。微阵列基因表达分析鉴定出一套DTX1特异性的转录程序——其中包含microRNA-21——该程序与经典Notch信号通路存在显著差异。我们提出，经由DTX1的非典型Notch通路可作为恶性胶质瘤的致癌因素；并且在公开数据库中，我们发现低DTX1表达水平与GBM患者及早期乳腺癌患者的更长生存期相关。我们构建了稳定表达增强型绿色荧光蛋白（Enhanced Green Fluorescent Protein, EGFP）、人源Deltex1-Myc标签（DTX1-myc）或显性负效Master Mind Like 1（MAML1-dn）的人胶质瘤U373细胞系，以比较各组间整体基因表达的差异。本实验共设置3份EGFP对照样本、3份DTX1-myc样本及3份MAML1-dn样本。