Pericytes/vessel-associated mural cells (VAMCs) are the major source of key epithelial-mesenchymal transition (EMT) factors SLUG and TWIST in human glioma.

Epithelial-to-mesenchymal transition (EMT) is supposed to be responsible for increased invasion and metastases in epithelial cancer cells. The activation of EMT genes has further been proposed to be important in the process of malignant transformation of primary CNS tumors. Since the cellular source and clinical impact of EMT factors in primary CNS tumors still remain unclear, we aimed at deciphering their distribution in vivo and clinico-pathological relevance in human gliomas. We investigated 350 glioma patients for the expression of the key EMT factors SLUG and TWIST by immunohistochemistry and immunofluorescence related to morpho-genetic alterations such as EGFR-amplification, IDH-1 (R132H) mutation and 1p/19q LOH. Furthermore, transcriptional cluster and survival analyses were performed. Our data illustrate that SLUG and TWIST are overexpressed in gliomas showing vascular proliferation such as pilocytic astrocytomas and glioblastomas. EMT factors are exclusively expressed by non-neoplastic pericytes/vessel-associated mural cells (VAMCs). They are not associated with patient survival but correlate with pericytic/VAMC genes in glioblastoma cluster analysis. In summary, the upregulation of EMT genes in pilocytic astrocytomas and glioblastomas reflects the level of activation of pericytes/VAMCs in newly formed blood vessels. Our results underscore that the negative prognostic potential of the EMT signature in the group of diffuse gliomas of WHO grade II-IV does most likely not derive from glioma cells but rather reflects the degree of proliferating mural cells thereby constituting a potential target for future alternative treatment approaches.

MIF Receptor CD74 is Restricted to Microglia/Macrophages, Associated with a M1-Polarized Immune Milieu and Prolonged Patient Survival in Gliomas.

The macrophage migration inhibitory factor (MIF) receptor CD74 is overexpressed in various neoplasms, mainly in hematologic tumors, and currently investigated in clinical studies. CD74 is quickly internalized and recycles after antibody binding, therefore it constitutes an attractive target for antibody-based treatment strategies. CD74 has been further described as one of the most up-regulated molecules in human glioblastomas. To assess the potential relevance for anti-CD74 treatment, we determined the cellular source and clinicopathologic relevance of CD74 expression in human gliomas by immunohistochemistry, immunofluorescence, immunoblotting, cell sorting analysis and quantitative polymerase chain reaction (qPCR). Furthermore, we fractionated glioblastoma cells and glioma-associated microglia/macrophages (GAMs) from primary tumors and compared CD74 expression in cellular fractions with whole tumor lysates. Our results show that CD74 is restricted to GAMs in vivo, while being absent in tumor cells, the latter strongly expressing its ligand MIF. Most interestingly, a higher amount of CD74-positive GAMs was associated with beneficial patient survival constituting an independent prognostic parameter and with an anti-tumoral M1 polarization. In summary, CD74 expression in human gliomas is restricted to GAMs and positively associated with patient survival. In conclusion, CD74 represents a positive prognostic marker most probably because of its association with an M1-polarized immune milieu in high-grade gliomas.

Tumour necrosis factor receptor superfamily member 9 (TNFRSF9) is up-regulated in reactive astrocytes in human gliomas.

AIMS: The prognosis of patients with malignant gliomas is still dismal despite maximum treatment. Novel therapeutic alternatives targeting tumorigenic pathways are, therefore, demanded. In murine glioma models, targeting of tumour necrosis factor receptor superfamily (TNFRSF) 9 led to complete tumour eradication. Thus, TNFRSF9 might also constitute a promising target in human diffuse gliomas. As there is a lack of data, we aimed to define the expression pattern and cellular source of TNFRSF9 in human gliomas. METHODS: We investigated TNFRSF9 expression in normal human central nervous system (CNS) tissue and glioma specimens using immunohistochemistry, immunofluorescence and Western blotting techniques. RESULTS: Our results show that TNFRSF9 is considerably up-regulated in human gliomas when compared with normal brain tissue. In addition, our data provides evidence for an immune cell-independent de novo expression pattern of TNFRSF9 in mainly non-neoplastic reactive astrocytes and excludes classic immunological cell types, namely lymphocytes and microglia as the source of TNFRSF9. Moreover, TNFRSF9 is predominantly expressed in a perivascular and peritumoural distribution with significantly higher expression in IDH-1 mutant gliomas. CONCLUSIONS: Our findings provide a novel, TNFRSF9-positive, reactive astrocytic phenotype and challenge the therapeutic suitability of TNFRSF9 as a promising target for human gliomas.

Netrin-1 expression is an independent prognostic factor for poor patient survival in brain metastases.

The multifunctional molecule netrin-1 is upregulated in various malignancies and has recently been presented as a major general player in tumorigenesis leading to tumor progression and maintenance in various animal models. However, there is still a lack of clinico-epidemiological data related to netrin-1 expression. Therefore, the aim of our study was to elucidate the association of netrin-1 expression and patient survival in brain metastases since those constitute one of the most limiting factors for patient prognosis. We investigated 104 brain metastases cases for netrin-1 expression using in-situ hybridization and immunohistochemistry with regard to clinical parameters such as patient survival and MRI data. Our data show that netrin-1 is strongly upregulated in most cancer subtypes. Univariate analyses revealed netrin-1 expression as a significant factor associated with poor patient survival in the total cohort of brain metastasis patients and in sub-entities such as non-small cell lung carcinomas. Interestingly, many cancer samples showed a strong nuclear netrin-1 signal which was recently linked to a truncated netrin-1 variant that enhances tumor growth. Nuclear netrin-1 expression was associated with poor patient survival in univariate as well as in multivariate analyses. Our data indicate both total and nuclear netrin-1 expression as prognostic factors in brain metastases patients in contrast to other prognostic markers in oncology such as patient age, number of brain metastases or Ki67 proliferation index. Therefore, nuclear netrin-1 expression constitutes one of the first reported molecular biomarkers for patient survival in brain metastases. Furthermore, netrin-1 may constitute a promising target for future anti-cancer treatment approaches in brain metastases.

Differential expression of the tumor suppressor A-kinase anchor protein 12 in human diffuse and pilocytic astrocytomas is regulated by promoter methylation.

The scaffold protein A-kinase anchor protein 12 (AKAP12) exerts tumor suppressor activity and is downregulated in several tumor entities. We characterized AKAP12 expression and regulation in astrocytomas, including pilocytic and diffusely infiltrating astrocytomas. We examined 194 human gliomas and 23 normal brain white matter samples by immunohistochemistry or immunoblotting for AKAP12 expression. We further performed quantitative methylation analysis of the AKAP12 promoter by MassARRAY® of normal brain, World Health Organization (WHO) grade I to IV astrocytomas, and glioma cell lines. Our results show that AKAP12 is expressed in a perivascular distribution in normal CNS, strongly upregulated in tumor cells in pilocytic astrocytomas, and weakly expressed in diffuse astrocytomas of WHO grade II to IV. Methylation analyses revealed specific hypermethylation of AKAP12α promoter in WHO grade II to IV astrocytomas. Restoration experiments using 5-aza-2'-deoxycytidine in primary glioblastoma cells decreased AKAP12α promoter methylation and markedly increased AKAP12α mRNA levels. In summary, we demonstrate that AKAP12 is differentially expressed in human astrocytomas showing high expression in pilocytic but low expression in diffuse astrocytomas of all WHO-grades. Our results further indicate that epigenetic mechanisms are involved in silencing AKAP12 in diffuse astrocytomas; however, a tumor suppressive role of AKAP12 in distinct astrocytoma subtypes remains to be determined.

Expression of vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 in primary and recurrent WHO grade III meningiomas.

AIMS: WHO grade III meningiomas are malignant neoplasms for which new and more targeted treatment strategies are urgently needed. Although clinical trials investigating anti-angiogenic vascular endothelial growth factor (VEGF) targeted therapies are currently recruiting, knowledge about the expression of VEGF and VEGF receptors remains to be determined. METHODS: We investigated the expression of VEGF and its receptors VEGFR1 and VEGFR2 in 32 WHO grade III meningioma samples by immunohistochemistry. Furthermore, we performed in-situ hybridisation for VEGF. RESULTS: We found low VEGF expression in tumor and endothelial cells. Highest VEGF expression levels were seen in peri-necrotic tumor cells potentially suffering from hypoxia. VEGFR1 and 2 were virtually absent on tumor cells, although endothelial cells displayed significantly higher levels reaching stronger expression for VEGFR2 than VEGFR1. CONCLUSIONS: Our findings showing constant expression levels of VEGFR2 in endothelial cells serve as a first indication that the use of small tyrosine kinase inhibitors such as Sunitinib directly targeting the VEGF-receptors might be worth testing, also in the clinical context in cases of therapy-refractory meningiomas. Further investigations are needed to study the response to drugs targeting the VEGF pathway in relation to the expression profile of VEGF and its receptors in high grade meningiomas.

Anti-tissue factor (TF9-10H10) treatment reduces tumor cell invasiveness in a novel migratory glioma model.

In vitro and descriptive studies of human tissue samples revealed the pro-coagulant glycoprotein tissue factor (TF) as a potent player in glioma cell infiltration that is activated by hypoxia and has also been shown to be upregulated by mutations of TP53 or PTEN. Here we present the morphological and genetic characterization of a novel glioblastoma in vivo model and provide evidence that treatment with an antibody targeting TF leads to reduced glioma cell invasiveness. Therefore, we established a murine xenograft treatment model by transplanting the angiogenic and diffusely infiltrating human glioma cell line MZ-18 with endogenous TF expression into nude mice brains and treating these mice with an intracranial osmotic pump system continuously infusing a monoclonal antibody against TF (mAb TF9-10H10). The human MZ-18 cell line harbors two TP53 mutations resulting in a strong nuclear accumulation of p53, thereby facilitating the unambiguous identification of tumor cells in the xenograft model. Intracranial application of TF9-10H10 significantly reduced invasion of MZ-18 cells compared to mock-treated control animals. The extent of activated blood vessels was also reduced upon anti-TF treatment. Thus, targeting the TF pathway might be a promising treatment strategy for future glioblastoma therapies, by affecting both invading tumor cells and tumor vasculature.

Adora2b signaling on bone marrow derived cells dampens myocardial ischemia-reperfusion injury.

BACKGROUND: Cardiac ischemia-reperfusion (I-R) injury represents a major cause of cardiac tissue injury. Adenosine signaling dampens inflammation during cardiac I-R. The authors investigated the role of the adenosine A2b-receptor (Adora2b) on inflammatory cells during cardiac I-R. METHODS: To study Adora2b signaling on inflammatory cells, the authors transplanted wild-type (WT) bone marrow (BM) into Adora2b(-/-) mice or Adora2b(-/-) BM into WT mice. To study the role of polymorphonuclear leukocytes (PMNs), neutrophil-depleted WT mice were treated with an Adora2b agonist. After treatments, mice were exposed to 60 min of myocardial ischemia and 120 min of reperfusion. Infarct sizes and troponin I concentrations were determined by triphenyltetrazolium chloride staining and enzyme-linked immunosorbent assay, respectively. RESULTS: Transplantation of WT BM into Adora2b(-/-) mice decreased infarct sizes by 19 ± 4% and troponin I by 87.5 ± 25.3 ng/ml (mean ± SD, n = 6). Transplantation of Adora2b(-/-) BM into WT mice increased infarct sizes by 20 ± 3% and troponin I concentrations by 69.7 ± 17.9 ng/ml (mean ± SD, n = 6). Studies on the reperfused myocardium revealed PMNs as the dominant cell type. PMN depletion or Adora2b agonist treatment reduced infarct sizes by 30 ± 11% or 26 ± 13% (mean ± SD, n = 4); however, the combination of both did not produce additional cardioprotection. Cytokine profiling showed significantly higher cardiac tumor necrosis factor α concentrations in Adora2b(-/-) compared with WT mice (39.3 ± 5.3 vs. 7.5 ± 1.0 pg/mg protein, mean ± SD, n = 4). Pharmacologic studies on human-activated PMNs revealed an Adora2b-dependent tumor necrosis factor α release. CONCLUSION: Adora2b signaling on BM-derived cells such as PMNs represents an endogenous cardioprotective mechanism during cardiac I-R. The authors' findings suggest that Adora2b agonist treatment during cardiac I-R reduces tumor necrosis factor α release of PMNs, thereby dampening tissue injury.

The "go or grow" potential of gliomas is linked to the neuropeptide processing enzyme carboxypeptidase E and mediated by metabolic stress.

Glioblastoma (GBM), the most common malignant brain tumor, is among the most lethal neoplasms, with a median survival of approximately 1 year. Prognosis is poor since GBMs possess a strong migratory and highly invasive potential, making complete surgical resection impossible. Reduced expression of carboxypeptidase E (CPE), a neuropeptide-processing enzyme, in a cell death-resistant glioma cell line and lower CPE expression levels in the cohort of GBM samples of The Cancer Genome Atlas compared to normal brain control specimens prompted us to analyze the function of CPE as a putative tumor suppressor gene. In our samples, CPE was also reduced in GBM compared to normal brain with the strongest loss in cells surrounding hypoxic tumor areas as well as in most glioma cell lines and primary glioma cells. In our cohort of glioma patients, loss of CPE predominantly occurred in glioblastomas and was associated with worse prognosis. In glioma cells, CPE overexpression was significantly reduced, whereas knockdown or inhibition enhanced glioma cell migration and invasion. The decreased migratory potential following CPE overexpression was paralleled by altered cellular morphology, promoting a transition to focal adhesions and associated stress fibers. In contrast to the decreased migration, high CPE levels were associated with higher proliferative rates. As microenvironmental regulation cues, we identified CPE as being downregulated upon hypoxia or glucose deprivation. Our findings indicate an oxygen- and nutrition-dependent anti-migratory, but pro-proliferative role of CPE in gliomas with prognostic impact for patient survival, thereby contributing to the understanding of the "go or grow" hypothesis in gliomas.

Macrophage migration inhibitory factor (MIF) expression in human malignant gliomas contributes to immune escape and tumour progression.

Macrophage migration inhibitory factor (MIF), which inhibits apoptosis and promotes angiogenesis, is expressed in cancers suppressing immune surveillance. Its biological role in human glioblastoma is, however, only poorly understood. We examined in-vivo expression of MIF in 166 gliomas and 23 normal control brains by immunohistochemistry. MIF immunoreactivity was enhanced in neoplastic astrocytes in WHO grade II glioma and increased significantly in higher tumour grades (III-IV). MIF expression was further assessed in 12 glioma cell lines in vitro. Quantitative RT-PCR showed that MIF mRNA expression was elevated up to 800-fold in malignant glioma cells compared with normal brain. This translated into high protein levels as assessed by immunoblotting of total cell lysates and by ELISA-based measurement of secreted MIF. Wild-type p53-retaining glioma cell lines expressed higher levels of MIF, which may be connected with the previously described role of MIF as a negative regulator of wild-type p53 signalling in tumour cells. Stable knockdown of MIF by shRNA in glioma cells significantly increased tumour cell susceptibility towards NK cell-mediated cytotoxicity. Furthermore, supernatant from mock-transfected cells, but not from MIF knockdown cells, induced downregulation of the activating immune receptor NKG2D on NK and CD8+ T cells. We thus propose that human glioma cell-derived MIF contributes to the immune escape of malignant gliomas by counteracting NK and cytotoxic T-cell-mediated tumour immune surveillance. Considering its further cell-intrinsic and extrinsic tumour-promoting effects and the availability of small molecule inhibitors, MIF seems to be a promising candidate for future glioma therapy.

CD133 expression is associated with small round blue cell tumour morphology in human central nervous system neoplasms.

AIMS: CD133 is considered to be a marker for brain tumour-initiating cells. However, most data on CD133 are derived from animal or in-vitro studies. The aim of this study was to characterize CD133 expression, and the distribution and morphological features of CD133(+) cells, in primary and secondary human central nervous system (CNS) neoplasms. METHODS AND RESULTS: Tumours were analysed by real-time reverse transcription polymerase chain reaction, western blot, flow cytometry and immunohistochemistry. Our results show that only small round blue cell tumours (SRBCTs) exhibit strong and consistent CD133 expression. Interestingly, glioblastomas, large-cell carcinomas and sarcomas were negative for CD133. Only glioblastomas with a focal small-cell component exhibited CD133 immunoreactivity in the SRBCT component. In addition, CD133 expression did not correlate with the expression of other markers associated with stem cell differentiation, including CD15 and nestin. CONCLUSIONS: CD133 expression in human CNS neoplasms is independent of the grade of malignancy but strongly correlates with SRBCT morphology. Together with recent findings showing that CD133 is quickly upregulated upon hypoxia and that CD133(-) cells can also exhibit stem cell properties, our data strongly question the suitability of CD133 as a brain tumour stem cell marker in vivo.