Jean-Pierre Gagner

Angiogenesis in Gliomas: Biology and Molecular Pathophysiology

Glioblastoma multiforme (GBM) is characterized by exuberant angiogenesis, a key event in tumor growth and progression. The pathologic mechanisms driving this change and the biological behavior of gliomas remain unclear. One mechanism may involve cooption of native blood vessels by glioma cells inducing expression of angio‐poietin‐2 by endothelial cells. Subsequently, vascular apoptosis and involution leads to necrosis and hypoxia. This in turn induces angiogenesis that is associated with expression of hypoxia‐inducible factor (HIF)‐1 a and vascular endothelial growth factor (VEGF) in perinecrotic pseudopalisading glioma cells. Here we review the molecular and cellular mechanisms implicated in HIF‐1 ‐dependent and HIF‐1 ‐independent glioma‐associated angiogenesis. In GBMs, both tumor hypoxia and genetic alterations commonly occur and act together to induce the expression of HIF‐1. The angiogenic response of the tumor to HIF‐1 is mediated by HIF‐1‐regulated target genes leading to the upregulation of several proangiogenic factors such as VEGF and other adaptive response molecules. Understanding the roles of these regulatory processes in tumor neovascularization, tumor growth and progression, and resistance to therapy will ultimately lead to the development of improved antiangiogenic therapies for GBMs.

Geldanamycin inhibits migration of glioma cells in vitro: A potential role for hypoxia-inducible factor (HIF-1α) in glioma cell invasion

Focal adhesion kinase (FAK) and hypoxia‐inducible factor (HIF‐1α) are both up‐regulated in glioblastoma multiforme (GBMs), particularly in invasive zones. Because FAK may play an important role in the invasion of glioma cells into the surrounding brain, we sought an agent that causes down‐regulation of FAK phosphorylation as a potential inhibitor of brain tumor invasion and growth. Geldanamycin (GA), a benzoquinone ansamycin antibiotic, binds to heat shock protein 90 (Hsp90) and interferes with its function. GA inhibits the proliferation of various non‐glial cells and has anti‐tumor activity. Moreover, GA blocks HIF‐regulated transcription of VEGF and inhibits the VEGF‐induced phosphorylation of FAK and migration of endothelial cells. Here, we tested the effect of GA on glioma cell migration in vitro and its potential to down‐regulate HIF‐1α induction. Our results demonstrate that GA (i) decreases U87MG, LN229, and U251MG glioma cell migration; (ii) reduces cell migration independent of p53 and PTEN status; (iii) prevents migration at non‐toxic concentrations; (iv) reduces phosphorylation of FAK; and (v) inhibits cobalt chloride (CoCl2)‐mediated induction of HIF‐1α in glioma cells. To the best of our knowledge, this is the first report showing that GA can inhibit phosphorylation of FAK concomitant with a decrease in cellular migration. One of the most clinically relevant aspects of this study is that GA interferes with the induction of HIF‐1α that has been linked with glioma cell migration and angiogenesis. Given the fact that GA is a small lipophilic molecule capable of penetrating the blood brain barrier together with the data presented here provide a strong rationale for its use or its analogues in the treatment of highly invasive GBMs. J. Cell. Physiol. 196: 394–402, 2003.

Angiogenesis in Gliomas: Imaging and Experimental Therapeutics

Much of the interest in angiogenesis and hypoxia has led to investigating diagnostic imaging methodologies and developing efficacious agents against angiogenesis in gliomas. In many ways, because of the cytostatic effects of these agents on tumor growth and tumor‐associated endothelial cells, the effects of therapy are not immediately evident. Hence finding clinically applicable imaging tools and pathologic surrogate markers is an important step in translating glioma biology to therapeutics. There are a variety of strategies in the approach to experimental therapeutics that target the hypoxia‐inducible factor pathway, the endogenous antiangiogenic and proangiogenic factors and their receptors, adhesion molecules, matrix proteases and cytokines, and the existing vasculature. We discuss the rationale for antiangiogenesis as a treatment strategy, the preclinical and clinical assessment of antiangiogenic interventions and finally focus on the various treatment strategies, including combining antiangiogenic drugs with radiation and chemotherapy.

Probing Glioblastoma Tissue Heterogeneity with Laser Capture Microdissection

Among various methods now available to isolate distinct cell populations or even single cells for DNA/RNA and proteomic analysis, laser capture microdissection (LCM) offers a unique opportunity to study cells in their topological contexts. This chapter focuses on the preparation of LCM membrane slides, tissue staining and laser microdissection of cells of interest from frozen or formalin-fixed, paraffin-embedded glioblastoma tissue.

Abstract A20: A novel CXCR4 antagonist interferes with antivascular endothelial growth factor therapy-induced glioma dissemination

Background: Resistance to antiangiogenic therapy (AT) in patients with glioblastoma (GBM) treated with bevacizumab (BEV) is characterized by local recurrence and distant dissemination of gliomas associated with remodeling of tumor vessels and pronounced hypoxia known to promote glioma cell invasion. Expression of the chemokine receptor CXCR4 and its ligand stromal cell-derived factor-1α (SDF-1α) is enhanced in invading tumor cells (CXCR4) and neurons and blood vessels (SDF-1α) in GBM and associated with tumor hypoxia, proliferation, invasion and angiogenesis. Using Protein Epitope Mimetics (PEM) technology (Robinson JA et al., 2008), Polyphor Ltd. has developed selective, highly potent CXCR4 antagonists (De Marco SJ et al., 2006) (U.S. Patent no. 8,716,242), such as POL5551. To address the problem of resistance to AT, we sought to determine whether combined therapy (CTx) with POL5551 and the murine equivalent of BEV (antibody B20-4.1.1) could inhibit the invasion and associated pathologic characteristics of gliomas in vivo. Methods: Adult C57BL/6 mice implanted orthotopically with syngeneic CT-2A or GL261 glioma cells were randomized on day 14 into 4 groups: 1) control, 2) POL5551 (5 mg/kg s.c.), 3) anti-murine vascular endothelial growth factor (VEGF) monoclonal antibody B20-4.1.1 (5 mg/kg i.p.; Genentech Inc.) (Bagri A et al., 2010) and 4) combined POL5551 and B20-4.1.1 (CTx). On day 28, brain tissues were processed, sections analyzed for tumor volume and invasiveness (Sottoriva A et al., 2010) (HE May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A20.