Platelet-derived growth factor receptor-beta is induced during tumor development and upregulated during tumor progression in endothelial cells in human gliomas.

BACKGROUND: Endothelial cells proliferate during brain development, are quiescent in normal adult brain but proliferate again under pathologic conditions such as glioma growth. The vascular phenotype of low grade glioma is comparable to normal brain, however high grade gliomas are focally highly vascularized and there is associated prominent endothelial cell proliferation. The mechanisms of this change in vascular phenotype are unknown but there is evidence that growth factors play an important role in this process as well as in normal angiogenesis and vascular differentiation. EXPERIMENTAL DESIGN: To investigate whether endothelial cells become activated during tumorigenesis and progression of human gliomas by a platelet-derived growth factor (PDGF) dependent pathway, we analyzed platelet-derived growth factor receptor-beta (PDGFR-beta) expression by in situ hybridization and immunocytochemistry in normal human brain, astrocytoma (grade II), anaplastic oligo-astrocytoma (grade III), and glioblastoma multiforme (grade IV). RESULTS: PDGFR-beta mRNA was not detectable in the vessels of normal human brain, but was expressed in the vasculature of low and high grade gliomas, particularly in endothelial cell proliferations in glioblastomas. The expression of the receptor in the tumor microvessels, was confirmed by double immunofluorescence in which the staining appeared to be in the endothelial cells. Primary cultures of endothelial cells derived from glioblastoma multiforme maintained receptor expression for 2 days in vitro, whereas it was not detectable in vitro in endothelial cells derived from normal brain. Tumor cells in all grades of glioma expressed very little PDGFR-beta mRNA in situ. CONCLUSIONS: Our results indicate that the malignant phenotype in human glial tumors is associated with an upregulation of the PDGFR-beta on endothelial cells of vessels which vascularize the tumor. These findings may contribute to our understanding of the mechanisms that regulate vessel growth and differentiation in normal and pathologic states.     

Brain-specific angiogenesis inhibitor 1 (BAI1) is expressed in human cerebral neuronal cells

Brain-specific angiogenesis inhibitor 1 (BAI1) is a p53-target gene specifically expressed in the brain. We examined the distribution of the endogenous BAI1 protein in normal human brain tissue using a polyclonal antibody against the extracellular region of BAI1. Immunohistochemical study demonstrated that BAI1 was expressed in neuronal cells of the cerebral cortex but not in astrocytes. BAI1 protein was localized in the cellular cytoplasm and membrane. It was predominantly localized in the cellular membrane when expressed in cultured cells by means of gene transfection. BAI1 protein may play an important role in neuronal functions such as synapse formation and signal transduction.     

The human Fn14 receptor gene is up-regulated in migrating glioma cells in vitro and overexpressed in advanced glial tumors

Glioblastoma multiforme comprises the majority of human brain tumors. Patients with glioblastoma multiforme have poor survival rates, with an average life expectancy of <1 year. To assess possible mechanisms and to potentially target invasive glioma cells, we previously measured the gene expression profiles of glioma cells under migration-activated or passive states. One of the genes identified was Fn14, which encodes a cell surface receptor for the tumor necrosis factor superfamily member named TWEAK. In this study, we show that Fn14 gene expression is induced in migration-activated glioma cells in vitro and significantly increases according to tumor grade in vivo (P < 0.01), with highest levels in glioblastoma tissue specimens. The in situ expression pattern of Fn14 mRNA and protein was confined to primary glioma cells and the vascular endothelium, with no detection in adjacent normal brain. Conversely, TWEAK mRNA levels are low in glioblastoma samples relative to normal brain tissue. In addition, activation of the Fn14 receptor by addition of recombinant TWEAK resulted in increased glioma cell migration in vitro. These results suggest a positive role for TWEAK and Fn14 in glioma progression and indicate that Fn14 gene expression may serve as a marker for invasive glioma cells.     

Up-regulation of urokinase and urokinase receptor genes in malignant astrocytoma.

To understand the role of urokinase (u-PA) and the urokinase receptor (u-PAR) in malignant astrocytoma cell invasion of normal brain, astrocytic expression of u-PAR and u-PA mRNAs were analyzed by riboprobe in situ hybridization in astrocytoma and non-neoplastic brain biopsies. In eight of eight malignant astrocytomas (glioblastomas), u-PAR and u-PA mRNA expression was demonstrated, whereas in seven non-neoplastic brain biopsies, u-PAR and u-PA mRNAs were not expressed. In one of four low grade and all anaplastic astrocytomas u-PAR mRNA was expressed, although u-PA mRNA was undetectable. Consistent with the mRNA detection, u-PAR and u-PA proteins were expressed by malignant astrocytes in five of five glioblastoma biopsies. To study the tumor margin, U-251MG glioblastoma cells were propagated intracerebrally in a severe combined immunodeficient mouse xenograft (28 days), and u-PA mRNA was found to localize predominantly to the leading tumor edge, whereas u-PAR mRNA was expressed throughout the tumor. Furthermore, adherent human U-251MG glioblastoma cells in vitro expressed u-PAR and u-PA proteins, which localized to sites of integrin alpha nu beta 3 cell-matrix contacts. These data indicate that co-expression of u-PAR and u-PA mRNAs and proteins marks the malignant astrocyte phenotype and that u-PA bound to u-PAR may play a role in glioblastoma cell invasion of normal brain by virtue of its expression at the leading tumor edge.     

脑胶质瘤患者LMO-1和LMO-4基因表达水平的改变及其意义

目的探讨脑胶质瘤患者脑组织中LMO-1和LMO-4基因表达水平的改变及其意义。方法采用实时荧光定量聚合酶链反应（real-time PCR）检测46例脑胶质瘤手术患者脑组织及19例正常脑组织标本中LMO1和LMO4的表达水平,分析LMO1、LMO4与病理分级之间的关系。结果脑胶质瘤患者脑组织中LMO-1表达高于正常对照组（P〈0.05）;LMO1在不同分级的胶质瘤中表达并不相同,在Ⅲ、Ⅳ级中的相对表达量显著高于Ⅰ、Ⅱ级（P〈0.01）;LMO1表达水平与胶质瘤分级正相关,差异具有显著性意义（P〈0.05）。在多形性胶质母细胞瘤患者脑组织中,LMO-4的表达明显高于其它级别胶质瘤和正常对照组（P〈0.05）。结论脑胶质瘤患者肿瘤组织中LMO-1和LMO-4表达增高,可能参与了胶质瘤的发生、发展过程。     

Creutzfeldt astrocytes may be seen in IDH‐wildtype glioblastoma and retain expression of DNA repair and chromatin binding proteins

Astrocytes with multiple micronuclei (“Creutzfeldt cells”) in a brain biopsy are classically associated with demyelinating disease. However, glioblastoma may also have prominent Creutzfeldt astrocytes, along with granular mitoses. Therefore, Creutzfeldt cells may raise the diagnostic dilemma of high‐grade glioma vs tumefactive demyelination. While cases of glioblastoma (GBM) with Creutzfeldt astrocytes have been reported, their clinicopathologic spectrum and genetic features are not understood. Studies have proposed that micronuclei in Creutzfeldt cells are a consequence of DNA damage, or may be susceptible to DNA damage and chromothripsis, but their biology in the context of glioblastoma remains unclear. Based on a challenging index case of GBM with mild hypercellularity, Creutzfeldt astrocytes, and granular mitoses on biopsy, we searched our archives for additional cases with similar histopathologic features. We identified 13 cases, reviewed their clinico‐radiologic and pathologic features, and examined them for recurrent genetic alterations via NGS (9 cases) and for evidence of DNA damage by immunohistochemistry for DNA repair and chromatin remodeling proteins. We found that Creutzfeldt cell‐rich GBMs were IDH‐wildtype with no recurring genetic alterations. To test our hypothesis that micronuclei demonstrate loss of DNA repair or chromatin remodeling proteins, we examined the expression of various proteins (MDM2, p53, MLH1, MSH2, PMS2, MSH6, ATRX, INI1, SATB2, Ki67, pHH3) in Creutzfeldt cell rich‐GBM. There was intact expression of DNA repair and chromatin remodeling proteins, with accumulation of p53 and reduced MDM2 expression within micronuclei. In contrast, granular mitoses showed pHH3 expression, confirming these cells are undergoing mitotic division, with no accumulation of p53 and reduced expression of DNA repair proteins. Our results emphasize that Creutzfeldt cells are part of the morphologic spectrum of IDH‐wildtype glioblastoma. We did not find a role for DNA damage in the generation of Creutzfeldt cells, as both DNA repair and chromatin remodeling protein expression was retained in these cells.     

Localization of CD44 at the Invasive Margin of Glioblastomas by Immunoelectron Microscopy

Glioblastoma multiforme is a highly invasive primary brain tumor, which is known to strongly express the CD44 cell adhesion receptor. A number of experimental studies suggest that the interaction of this receptor with extracellular matrix (ECM) proteins such as hyaluronic acid may in part mediate human glioma cell adhesion and invasion of brain tissue. Although the expression of CD44 and its spliced variants in brain tumors have been extensively studied, there have been no reports localizing its expression to the invasive margin of the tumor. The authors used immunoelectron microscopy to investigate the expression patterns of CD44 in an in vitro organotypic invasion assay. Tumor spheroids initiated from the U373 MG human glioblastoma line were confronted with fetal rat brain aggregates in a spheroid coculture system. The CD44 expression appeared at the interface between glioblastoma tumor spheroids and brain tissue, as well as in the spheroid itself. CD44 immunoreactivity was not detectable in mature 21-day fetal brain aggregates. The findings provide direct evidence that CD44 is expressed at the confrontational invasive border between glioblastomas and brain tissue, further supporting its role in glioma cell-ECM recognition and attachment.     

ClC-3在人胶质瘤中的表达及分布

目的：探讨ClC-3在人脑胶质瘤中的表达及其生物学意义。 方法： 应用免疫组织化学染色技术检测24例人胶质瘤以及4例脑转移癌手术标本中ClC-3蛋白的表达；RT-PCR检测ClC-3蛋白表达阳性的手术标本中其mRNA表达。 结果： 4例正常脑组织ClC-3蛋白的表达为阴性；而蛋白表达阳性的19例胶质瘤及4例脑转移癌中，ClC-3主要位于瘤细胞和微血管内皮细胞的胞浆或胞膜上。蛋白表达阳性的手术标本中16例胶质瘤和4例脑转移癌检测到ClC-3 mRNA的表达。少突胶质细胞瘤Ⅲ级中ClC-3的mRNA和蛋白表达明显高于其Ⅱ级。 结论： ClC-3在人胶质瘤及脑转移癌组织中普遍表达，并且可能与少突胶质细胞瘤病理分级相关。     

ClC-3在人胶质瘤中的表达及分布

目的探讨ClC-3在人脑胶质瘤中的表达及其生物学意义。方法应用免疫组织化学染色技术检测24例人胶质瘤以及4例脑转移癌手术标本中ClC-3蛋白的表达;RT-PCR检测ClC-3蛋白表达阳性的手术标本中其mRNA表达。结果4例正常脑组织ClC-3蛋白的表达为阴性;而蛋白表达阳性的19例胶质瘤及4例脑转移癌中,ClC-3主要位于瘤细胞和微血管内皮细胞的胞浆或胞膜上。蛋白表达阳性的手术标本中16例胶质瘤和4例脑转移癌检测到ClC-3mRNA的表达。少突胶质细胞瘤Ⅲ级中ClC-3的mRNA和蛋白表达明显高于其Ⅱ级。结论ClC-3在人胶质瘤及脑转移癌组织中普遍表达,并且可能与少突胶质细胞瘤病理分级相关。     

CD44 in human glioma correlates with histopathological grade and cell migration

Glioblastomas are associated with high mortality due to their aggressive growth and invasiveness. Interactions and functional cross-talk between tumor cells and their microenvironments are mediated by cell surface receptors that are responsible for cell-cell and cell-extracellular matrix adhesion. Central nervous tissues contain plenty of the glycosaminoglycan hyaluronan, and glioma cells express the major cell surface hyaluronan receptor, CD44. In this study, we analyzed the expression and roles of CD44 in human brain tissues. Normal brain tissues showed no or weak CD44 expression, while reactive astrocytes and astrocytoma cells expressed CD44 at variable levels. Immunohistochemically, a higher percentage and intensity of CD44-positive tumor cells were detected in high-grade astrocytomas compared with low-grade astrocytomas. Glioblastoma cells that express CD44 were localized in perivascular and perinecrotic lesions. The human glioma cell lines A172 and KG-1-C expressed CD44 mRNA and protein. Administration of monoclonal anti-human-CD44 antibody inhibited the migration of A172 cells, which are glioblastoma-derived, but did not affect cell growth. In conclusion, CD44 expression levels correlated with the histopathological grade of gliomas, and monoclonal anti-CD44 antibody inhibited the migration of glioblastoma cells. These findings suggest that CD44 is a potential therapeutic target of glioblastomas.     

High expression and frequently humoral immune response of melanoma-associated antigen D4 in glioma

MAGE-D4 is a novel member of MAGE super-family. It has preliminarily been demonstrated that MAGE-D4 mRNA is not expressed in majority of normal tissues except for brain and ovary in which only trace amount of MAGE-D4 mRNA can be detected, but predominantly expressed in glioma. MAGE-D4 protein expression and its immunogenicity in glioma have not been elucidated well. This study was designed to analyze MAGE-D4 expression both at mRNA and protein level, characteristic of humoral immune response, and their relationships with glioma patients’ clinicopathological parameters. Recombinant MAGE-D4 protein and antiserum were generated. Quantitative RT-PCR analysis revealed that MAGE-D4 mRNA expression was overall up-regulated in 41 glioma specimens compared with that in 14 normal brain tissues. Immunohistochemistry analysis showed that 78% (21/27) glioma tissues expressed MAGE-D4 protein, which was predominantly located in the cytoplasm of tumor cells, but absent in any neuroglia cell of normal brain tissues. ELISA analysis demonstrated that humoral response against MAGE-D4 was detected in 17% (7/41) of glioma patients’ sera but not in 77 healthy donors. No apparent correlation was observed between the expression and immunogenicity of MAGE-D4 with clinicopathological parameters of glioma. In summary, these results indicate that MAGE-D4 is highly expressed in glioma and can develop specifically humoral response in glioma patients, which supports that it may be a promising biomarker for glioma diagnosis and immunotherapy.     

神经胶质瘤中β-抑制蛋白1的表达及意义

目的检测神经胶质瘤中β-抑制蛋白1(ARRB1)的表达水平及临床意义。方法采用RT-PCR和Western blotting检测胶质瘤细胞系中ARRB1的表达水平;通过肿瘤微阵列数据库(Oncomine)及Project Betastasis平台分析ARRB1 mRNA在神经胶质瘤中的表达情况;采用免疫组织化学方法检测神经胶质瘤组织及瘤旁脑组织中ARRB1的表达水平;应用Kaplan Meier分析ARRB1的表达水平与胶质瘤患者预后的关系。结果与正常人脑组织和人胚肾细胞系(HEK293)相比,神经胶质瘤细胞系中ARRB1的mRNA和蛋白水平降低;Oncomine数据库结果显示,多个神经胶质瘤基因芯片中ARRB1 mRNA水平较正常对照组明显降低(P0.001),ARRB1在恶性程度较高的胶质母细胞瘤中下降程度更加明显;免疫组织化学结果显示,与瘤旁脑组织相比神经胶质瘤中ARRB1表达降低,而且Ⅲ-Ⅳ期较Ⅰ-Ⅱ期神经胶质瘤降低更加明显。此外,Kaplan-Meier生存曲线结果显示,ARRB1的表达水平与神经胶质瘤患者的生存时间存在相关性(P0.05)。结论神经胶质瘤ARRB1水平下调,可作为反映神经胶质瘤临床病理学特点的指标;另外,ARRB1可作为判断神经胶质瘤患者预后的生物标志物。     

The Guanine Nucleotide Exchange Factors Trio, Ect2, and Vav3 Mediate the Invasive Behavior of Glioblastoma

Malignant gliomas are characterized by their ability to invade normal brain tissue. We have previously shown that the small GTPase Rac1 plays a role in both migration and invasion in gliomas. Here, we aim to identify Rac-activating guanine nucleotide exchange factors (GEFs) that mediate glioblastoma invasiveness. Using a brain tumor expression database, we identified three GEFs, Trio, Ect2, and Vav3, that are expressed at higher levels in glioblastoma versus low-grade glioma. The expression of these GEFs is also associated with poor patient survival. Quantitative real-time polymerase chain reaction and immunohistochemical analyses on an independent set of tumors confirmed that these GEFs are overexpressed in glioblastoma as compared with either nonneoplastic brain or low-grade gliomas. In addition, depletion of Trio, Ect2, and Vav3 by siRNA oligonucleotides suppresses glioblastoma cell migration and invasion. Depletion of either Ect2 or Trio also reduces the rate of cell proliferation. These results suggest that targeting GEFs may present novel strategies for anti-invasive therapy for malignant gliomas.     

Endosialin (CD248) is a marker of tumor-associated pericytes in high-grade glioma.

Gliomas are the most frequent primary tumors of the central nervous system in adults. The most prevalent and aggressive subclass of these is glioblastoma multiforme, which is characterized by massive neovascularization. Endosialin (CD248) has generated interest as a target for antiangiogenic therapy following reports that its expression is upregulated on angiogenic endothelial cells. We demonstrate here that endosialin is not expressed in normal human adult brain but is strongly upregulated in the angiogenic vasculature of all high-grade glioma specimens examined. However, by taking advantage of a technique which allows for multiple fluorescent labeling of formalin-fixed paraffin-embedded archival sections, we demonstrate unambiguously that endosialin is not expressed by the glioma endothelial cells but on closely associated perivascular cells. With increasing awareness that targeting pericytes is an attractive adjunct in antiangiogenic therapy, this finding has important implications for understanding the molecular mechanisms regulating angiogenesis in these highly vascularized tumors.