Bmi-1 通过激活 NF-κB/MMP-9 信号通路促进神经胶质瘤的侵袭性。
Bmi-1 promotes the aggressiveness of glioma via activating the NF-kappaB/MMP-9 signaling pathway.
机构信息
Department of Pathophysiology, Guangzhou Medical University, Guangzhou, Guangdong 510182, China.
出版信息
BMC Cancer. 2012 Sep 11;12:406. doi: 10.1186/1471-2407-12-406.
BACKGROUND
The prognosis of human glioma is poor, and the highly invasive nature of the disease represents a major impediment to current therapeutic modalities. The oncoprotein B-cell-specific Moloney murine leukemia virus integration site 1 protein (Bmi-1) has been linked to the development and progression of glioma; however, the biological role of Bmi-1 in the invasion of glioma remains unclear.
METHODS
A172 and LN229 glioma cells were engineered to overexpress Bmi-1 via stable transfection or to be silenced for Bmi-1 expression using RNA interfering method. Migration and invasiveness of the engineered cells were assessed using wound healing assay, Transwell migration assay, Transwell matrix penetration assay and 3-D spheroid invasion assay. MMP-9 expression and activity were measured using real-time PCR, ELISA and the gelatin zymography methods. Expression of NF-kappaB target genes was quantified using real-time PCR. NF-kappaB transcriptional activity was assessed using an NF-kappaB luciferase reporter system. Expression of Bmi-1 and MMP-9 in clinical specimens was analyzed using immunohistochemical assay.
RESULTS
Ectopic overexpression of Bmi-1 dramatically increased, whereas knockdown of endogenous Bmi-1 reduced, the invasiveness and migration of glioma cells. NF-kappaB transcriptional activity and MMP-9 expression and activity were significantly increased in Bmi-1-overexpressing but reduced in Bmi-1-silenced cells. The reporter luciferase activity driven by MMP-9 promoter in Bmi-1-overexpressing cells was dependent on the presence of a functional NF-kappaB binding site, and blockade of NF-kappaB signaling inhibited the upregulation of MMP-9 in Bmi-1 overexpressing cells. Furthermore, expression of Bmi-1 correlated with NF-kappaB nuclear translocation as well as MMP-9 expression in clinical glioma samples.
CONCLUSIONS
Bmi-1 may play an important role in the development of aggressive phenotype of glioma via activating the NF-kappaB/MMP-9 pathway and therefore might represent a novel therapeutic target for glioma.
背景
人类脑胶质瘤的预后较差，其高度侵袭性是当前治疗方法的主要障碍。癌蛋白 B 细胞特异性莫洛尼鼠白血病病毒整合位点 1 蛋白（Bmi-1）与脑胶质瘤的发生和发展有关；然而，Bmi-1 在脑胶质瘤侵袭中的生物学作用尚不清楚。
方法
通过稳定转染使 A172 和 LN229 脑胶质瘤细胞过表达 Bmi-1，或使用 RNA 干扰方法沉默 Bmi-1 表达，构建工程细胞。通过划痕愈合实验、Transwell 迁移实验、Transwell 基质穿透实验和 3-D 球体侵袭实验评估工程细胞的迁移和侵袭能力。使用实时 PCR、ELISA 和明胶酶谱法测量 MMP-9 的表达和活性。使用实时 PCR 定量测定 NF-κB 靶基因的表达。使用 NF-κB 荧光素酶报告基因系统评估 NF-κB 转录活性。使用免疫组织化学检测分析临床标本中 Bmi-1 和 MMP-9 的表达。
结果
Bmi-1 的异位过表达显著增加，而内源性 Bmi-1 的敲低则降低了脑胶质瘤细胞的侵袭和迁移能力。Bmi-1 过表达的细胞中 NF-κB 转录活性以及 MMP-9 的表达和活性显著增加，而 Bmi-1 沉默的细胞中则降低。Bmi-1 过表达细胞中 MMP-9 启动子驱动的报告基因荧光素酶活性依赖于 NF-κB 结合位点的功能，NF-κB 信号通路的阻断抑制了 Bmi-1 过表达细胞中 MMP-9 的上调。此外，临床脑胶质瘤样本中 Bmi-1 的表达与 NF-κB 核转位以及 MMP-9 的表达相关。
结论
Bmi-1 可能通过激活 NF-κB/MMP-9 通路在脑胶质瘤侵袭表型的发展中发挥重要作用，因此可能成为脑胶质瘤的一个新的治疗靶点。
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