Neuropathology Unit, Istituto Nazionale Neurologico Carlo Besta, Milan, Italy.
Cancer Biol Ther. 2011 Jan 15;11(2):242-53. doi: 10.4161/cbt.11.2.13951.
Gliomas are very invasive brain tumors with poor prognosis and therefore any attempt to limit tumor cell dissemination in the brain is expected to improve glioma treatment. The recent deorphanization of CXCR7 as additional receptor for CXCL12 and CXCL11 has raised key issues on its interaction with the CXCL12/CXCR4 axis as a mechanism to modulate glioma cell migration. In this work we investigated protein and mRNA expression of the two chemokines CXCL12 and CXCL11, together with their receptors CXCR4 and CXCR7 in human glioma specimens and cell lines by immunohistochemistry, flow cytometry and quantitative real-time PCR. The main purpose of this study was to find out whether and at what extent CXCR4 and CXCR7 are differentially expressed in glioma cells. In human glioma specimens the levels of CXCL11 and CXCR4 mRNA were significantly higher in glioblastomas compared to non-tumor controls or low grade gliomas, whilst no difference was found for CXCL12 and CXCR7 mRNA expression. In cell lines, flow cytometry and immunocytochemical experiments showed CXCR4 was mainly expressed irrespective of its membrane or intracellular localization. In contrast, a predominant intracellular localization together with a negligible membrane expression of CXCR7 was found in all cells examined. In in vitro experiments CXCR4 and CXCR7 antagonists and the silencing of CXCR4 showed complete inhibition of glioma proliferation. Our findings, in agreement with previous data, suggest that in human glioma cells the prevalent intracellular localization of CXCR7 might modulate the functionality of CXCL11/12 either acting as a scavenger for these chemokines or interfering with the signaling pathways activated by the stimulation of CXCR4.
神经胶质瘤是一种侵袭性很强的脑肿瘤,预后较差,因此任何限制肿瘤细胞在大脑中扩散的尝试都有望改善神经胶质瘤的治疗效果。最近,CXCR7 被重新定义为 CXCL12 和 CXCL11 的另一个受体,这引发了一个关键问题,即它与 CXCL12/CXCR4 轴的相互作用作为调节神经胶质瘤细胞迁移的机制。在这项工作中,我们通过免疫组织化学、流式细胞术和实时定量 PCR 研究了人类神经胶质瘤标本和细胞系中两种趋化因子 CXCL12 和 CXCL11 及其受体 CXCR4 和 CXCR7 的蛋白和 mRNA 表达。本研究的主要目的是确定 CXCR4 和 CXCR7 是否在神经胶质瘤细胞中存在差异表达,以及在何种程度上存在差异表达。在人类神经胶质瘤标本中,与非肿瘤对照或低级别神经胶质瘤相比,神经母细胞瘤中 CXCL11 和 CXCR4 mRNA 的水平显著升高,而 CXCL12 和 CXCR7 mRNA 的表达则没有差异。在细胞系中,流式细胞术和免疫细胞化学实验表明,CXCR4 主要表达,而不论其膜或细胞内定位如何。相比之下,在所有检查的细胞中都发现 CXCR7 主要定位于细胞内,而膜表达可以忽略不计。在体外实验中,CXCR4 和 CXCR7 拮抗剂以及 CXCR4 的沉默完全抑制了神经胶质瘤的增殖。我们的研究结果与之前的数据一致,表明在人类神经胶质瘤细胞中,CXCR7 的主要细胞内定位可能通过作为这些趋化因子的清除剂或干扰 CXCR4 刺激激活的信号通路来调节 CXCL11/12 的功能。
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