Wang Ting-Chung, Luo Sheng-Jie, Lin Chun-Liang, Chang Pey-Jium, Chen Miao-Fen
Division of Neurosurgery, Department of Surgery, Chang Gung Memorial Hospital, Chiayi, Taiwan.
Clin Exp Metastasis. 2015 Jan;32(1):73-81. doi: 10.1007/s10585-014-9692-z. Epub 2014 Dec 20.
p75 neurotrophin receptor (p75NTR) has been reported to play important roles in various cancer types. However, the exact mechanism of tumorigenesis involving p75NTR is unknown. In this study, we investigated the relationship between the expression of p75NTR in malignant glioma and the impact on tumor cell migration and invasion. p75NTR and hypoxia-inducible factor-1α (HIF-1α) expression was down-regulated by short-hairpin RNA and up-regulated with expression vectors. By immunohistochemical staining and Western blot analysis, we found that p75NTR was expressed in both human and rat malignant gliomas. Knockdown of p75NTR increased the expression of vimentin, vascular endothelial growth factor, Matrix metalloproteinase 9, and TWIST, and enhanced the invasion and migration abilities assessed by transwell assay in the C6 tumor cells. Inverse expressions of p75NTR and HIF-1α were detected in glioma cell lines under hypoxic conditions, while increased HIF-1α significantly downregulated the expression of p75NTR, suggesting a HIF-1α-p75NTR-EMT pathway that may regulate glioma cells invasion and migration. Downregulation of p75NTR increased phosphorylation of Src, focal adhesion kinase (FAK) and paxillin. Knockdown of p75NTR also dysregulated β-catenin-mediated cell junctions, and up-regulated the expressions of fibronectin and L1CAM in the cell-cell junctions, thus suggesting that p75NTR knockdown contributed to a more aggressive migration phenotype via FAK signaling pathway. Our studies suggested that modulation of p75NTR under hypoxic condition could enhance C6 cells migration and invasion by induction of EMT, and activation of the FAK pathway. The HIF-1α-p75NTR-EMT axis may play a central role in glioma tumorigenesis.
据报道，p75神经营养因子受体（p75NTR）在多种癌症类型中发挥重要作用。然而，涉及p75NTR的肿瘤发生的确切机制尚不清楚。在本研究中，我们调查了恶性胶质瘤中p75NTR的表达与对肿瘤细胞迁移和侵袭的影响之间的关系。通过短发夹RNA下调p75NTR和缺氧诱导因子-1α（HIF-1α）的表达，并使用表达载体上调其表达。通过免疫组织化学染色和蛋白质印迹分析，我们发现p75NTR在人和大鼠恶性胶质瘤中均有表达。敲低p75NTR会增加波形蛋白、血管内皮生长因子、基质金属蛋白酶9和TWIST的表达，并增强通过Transwell实验评估的C6肿瘤细胞的侵袭和迁移能力。在缺氧条件下，胶质瘤细胞系中检测到p75NTR和HIF-1α的反向表达，而HIF-1α的增加显著下调了p75NTR的表达，提示可能存在一条HIF-1α-p75NTR-上皮-间质转化（EMT）途径调节胶质瘤细胞的侵袭和迁移。p75NTR的下调增加了Src、粘着斑激酶（FAK）和桩蛋白的磷酸化。敲低p75NTR还会失调β-连环蛋白介导的细胞连接，并上调细胞间连接中纤连蛋白和L1细胞粘附分子的表达，因此表明敲低p75NTR通过FAK信号通路导致更具侵袭性的迁移表型。我们的研究表明，在缺氧条件下调节p75NTR可通过诱导EMT和激活FAK途径增强C6细胞的迁移和侵袭。HIF-1α-p75NTR-EMT轴可能在胶质瘤肿瘤发生中起核心作用。
