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EGFL7 enhances surface expression of integrin ?5?1 to promote angiogenesis in malignant brain tumors.

ABSTRACT: Glioblastoma (GBM) is a typically lethal type of brain tumor with a median survival of 15 months postdiagnosis. This negative prognosis prompted the exploration of alternative treatment options. In particular, the reliance of GBM on angiogenesis triggered the development of anti-VEGF (vascular endothelial growth factor) blocking antibodies such as bevacizumab. Although its application in human GBM only increased progression-free periods but did not improve overall survival, physicians and researchers still utilize this treatment option due to the lack of adequate alternatives. In an attempt to improve the efficacy of anti-VEGF treatment, we explored the role of the egfl7 gene in malignant glioma. We found that the encoded extracellular matrix protein epidermal growth factor-like protein 7 (EGFL7) was secreted by glioma blood vessels but not glioma cells themselves, while no major role could be assigned to the parasitic miRNAs miR-126/126*. EGFL7 expression promoted glioma growth in experimental glioma models in vivo and stimulated tumor vascularization. Mechanistically, this was mediated by an upregulation of integrin ?5?1 on the cellular surface of endothelial cells, which enhanced fibronectin-induced angiogenic sprouting. Glioma blood vessels that formed in vivo were more mature as determined by pericyte and smooth muscle cell coverage. Furthermore, these vessels were less leaky as measured by magnetic resonance imaging of extravasating contrast agent. EGFL7-inhibition using a specific blocking antibody reduced the vascularization of experimental gliomas and increased the life span of treated animals, in particular in combination with anti-VEGF and the chemotherapeutic agent temozolomide. Data allow for the conclusion that this combinatorial regimen may serve as a novel treatment option for GBM.

SUBMITTER: Dudvarski Stankovic N

PROVIDER: S-EPMC6127886 | biostudies-other | 2018 Sep

REPOSITORIES: biostudies-other

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EGFL7 enhances surface expression of integrin α<sub>5</sub>β<sub>1</sub> to promote angiogenesis in malignant brain tumors.

Dudvarski Stanković Nevenka N Bicker Frank F Keller Stefanie S Jones David Tw DT Harter Patrick N PN Kienzle Arne A Gillmann Clarissa C Arnold Philipp P Golebiewska Anna A Keunen Olivier O Giese Alf A von Deimling Andreas A Bäuerle Tobias T Niclou Simone P SP Mittelbronn Michel M Ye Weilan W Pfister Stefan M SM Schmidt Mirko H MHH

EMBO molecular medicine 20180901 9

Glioblastoma (GBM) is a typically lethal type of brain tumor with a median survival of 15 months postdiagnosis. This negative prognosis prompted the exploration of alternative treatment options. In particular, the reliance of GBM on angiogenesis triggered the development of anti-VEGF (vascular endothelial growth factor) blocking antibodies such as bevacizumab. Although its application in human GBM only increased progression-free periods but did not improve overall survival, physicians and resear ...[more]

PMID: 30065025

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Project description:Recently, the overexpression of CD146 and its potential as a therapeutic target in high-grade gliomas, the most lethal type of brain cancer, was uncovered. In this study, we describe the generation of (89)Zr-Df-YY146, a novel (89)Zr-labeled monoclonal antibody (mAb) for the targeting and quantification of CD146 expression in a mouse model of glioblastoma, using noninvasive immunoPET imaging. YY146, a high affinity anti-CD146 mAb, was conjugated to deferoxamine (Df) for labeling with the long-lived positron emitter (89)Zr (t1/2: 78.4 h). In vitro assays, including flow cytometry, immunofluorescence microscopy, and Western blot, were performed with two glioblastoma cell lines, U87MG and U251, to determine their CD146 expression levels. Also, YY146 and Df-YY146's CD146-binding affinities were compared using flow cytometry. In vivo CD146-targeting of (89)Zr-Df-YY146 was evaluated by sequential PET imaging, in athymic nude mice bearing subcutaneously implanted U87MG or U251 tumors. CD146 blocking, ex vivo biodistribution, and histological studies were carried out to confirm (89)Zr-Df-YY146 specificity, as well as the accuracy of PET data. In vitro studies exposed elevated CD146 expression levels in U87MG cells, but negligible levels in U251 cells. Flow cytometry revealed no differences in affinity between YY146 and Df-YY146. (89)Zr labeling of Df-YY146 proceeded with excellent yield (?80%), radiochemical purity (>95%), and specific activity (?44 GBq/?mol). Longitudinal PET revealed prominent and persistent (89)Zr-Df-YY146 uptake in mice bearing U87MG tumors that peaked at 14.00 ± 3.28%ID/g (n = 4), 48 h post injection of the tracer. Conversely, uptake was significantly lower in CD146-negative U251 tumors (5.15 ± 0.99%ID/g, at 48 h p.i.; n = 4; P < 0.05). Uptake in U87MG tumors was effectively blocked in a competitive inhibition experiment, corroborating the CD146 specificity of (89)Zr-Df-YY146. Finally, ex vivo biodistribution validated the accuracy of PET data and histological examination successfully correlated tracer uptake with in situ CD146 expression. Prominent, persistent, and specific uptake of (89)Zr-Df-YY146 was observed in brain tumors, demonstrating the potential of this radiotracer for noninvasive PET imaging of CD146 expression. In a future clinical scenario, (89)Zr-Df-YY146 may serve as a tool to guide intervention and assess response to CD146-targeted therapies.

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Dataset Information

EGFL7 enhances surface expression of integrin ?5?1 to promote angiogenesis in malignant brain tumors.

Publications

EGFL7 enhances surface expression of integrin α<sub>5</sub>β<sub>1</sub> to promote angiogenesis in malignant brain tumors.

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