Inhibition of CD95/CD95L (FAS/FASLG) Signaling with APG101 Prevents Invasion and Enhances Radiation Therapy for Glioblastoma.

CD95 (Fas/APO-1), a death receptor family member, activity has been linked to tumorigenicity in multiple cancers, including glioblastoma multiforme (GBM). A phase II clinical trial on relapsed glioblastoma patients demonstrated that targeted inhibition of CD95 signaling via the CD95 ligand (CD95L) binding and neutralizing Fc-fusion protein APG101 (asunercept) prolonged patient survival. Although CD95 signaling may be relevant for multiple aspects of tumor growth, the mechanism of action of APG101 in glioblastoma is not clear. APG101 action was examined by in vitro proliferation, apoptosis, and invasion assays with human and murine glioma and human microglial cells, as well as in vivo therapy studies with orthotopic gliomas and clinical data. APG101 inhibits CD95L-mediated invasion of glioma cells. APG101 treatment was effective in glioma-bearing mice, independently of the presence or absence of CD4 and CD8 T lymphocytes, which should be sensitive to CD95L. Combined with radiotherapy, APG101 demonstrated a reduction of tumor growth, fewer tumor satellites, reduced activity of matrix metalloproteinases (MMP) as well as prolonged survival of tumor-bearing mice compared with radiotherapy alone. Inhibiting rather than inducing CD95 activity is a break-of-paradigm therapeutic approach for malignant gliomas. Evidence, both in vitro and in vivo, is provided that CD95L-binding fusion protein treatment enhanced the efficacy of radiotherapy and reduced unwanted proinfiltrative effects by reducing metalloproteinase activity by directly affecting the tumor cells.Implications: APG101 (asunercept) successfully used in a controlled phase II glioblastoma trial (NCT01071837) acts anti-invasively by inhibiting matrix metalloproteinase signaling, resulting in additive effects together with radiotherapy and helping to further develop a treatment for this devastating disease. Mol Cancer Res; 16(5); 767-76. ©2018 AACR.

Glioma cell VEGFR-2 confers resistance to chemotherapeutic and antiangiogenic treatments in PTEN-deficient glioblastoma.

Loss of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a prerequisite for tumor cell-specific expression of vascular endothelial growth factor receptor (VEGFR)-2 in glioblastoma defining a subgroup prone to develop evasive resistance towards antiangiogenic treatments. Immunohistochemical analysis of human tumor tissues showed VEGFR-2 expression in glioma cells in 19% of specimens examined, mainly in the infiltration zone. Glioma cell VEGFR-2 positivity was restricted to PTEN-deficient tumor specimens. PTEN overexpression reduced VEGFR-2 expression in vitro, as well as knock-down of raptor or rictor. Genetic interference with VEGFR-2 revealed proproliferative, antiinvasive and chemoprotective functions for VEGFR-2 in glioma cells. VEGFR-2-dependent cellular effects were concomitant with activation of 'kappa-light-chain-enhancer' of activated B-cells, protein kinase B, and N-myc downstream regulated gene 1. Two-photon in vivo microscopy revealed that expression of VEGFR-2 in glioma cells hampers antiangiogenesis. Bevacizumab induces a proinvasive response in VEGFR-2-positive glioma cells. Patients with PTEN-negative glioblastomas had a shorter survival after initiation of bevacizumab therapy compared with PTEN-positive glioblastomas. Conclusively, expression of VEGFR-2 in glioma cells indicates an aggressive glioblastoma subgroup developing early resistance to temozolomide or bevacizumab. Loss of PTEN may serve as a biomarker identifying those tumors upfront by routine neuropathological methods.

KIAA1797/FOCAD encodes a novel focal adhesion protein with tumour suppressor function in gliomas.

In a strategy to identify novel genes involved in glioma pathogenesis by molecular characterization of chromosomal translocation breakpoints, we identified the KIAA1797 gene, encoding a protein with an as yet undefined function, to be disrupted by a 7;9 translocation in a primary glioblastoma culture. Array-based comparative genomic hybridization detected deletions involving KIAA1797 in around half of glioblastoma cell lines and glioblastomas investigated. Quantification of messenger RNA levels in human tissues demonstrated highest KIAA1797 expression in brain, reduced levels in all glioblastoma cell lines and most glioblastomas and similar levels in glial and neuronal cells by analysis of different hippocampal regions from murine brain. Antibodies against KIAA1797 were generated and showed similar protein levels in cortex and subcortical white matter of human brain, while levels were significantly reduced in glioblastomas with KIAA1797 deletion. By immunofluorescence of astrocytoma cells, KIAA1797 co-localized with vinculin in focal adhesions. Physical interaction between KIAA1797 and vinculin was demonstrated via co-immunoprecipitation. Functional in vitro assays demonstrated a significant decrease in colony formation, migration and invasion capacity of LN18 and U87MG glioma cells carrying a homozygous KIAA1797 deletion ectopically expressing KIAA1797 compared with mock-transduced cells. In an in vivo orthotopic xenograft mouse model, U87MG tumour lesions expressing KIAA1797 had a significantly reduced volume compared to tumours not expressing KIAA1797. In summary, the frequently deleted KIAA1797 gene encodes a novel focal adhesion complex protein with tumour suppressor function in gliomas, which we name 'focadhesin'. Since KIAA1797 genetic variation has been implicated in Alzheimer's disease, our data are also relevant for neurodegeneration.

Costimulatory protein 4IgB7H3 drives the malignant phenotype of glioblastoma by mediating immune escape and invasiveness.

PURPOSE: Recent work points out a role of B7H3, a member of the B7-family of costimulatory proteins, in conveying immunosuppression and enforced invasiveness in a variety of tumor entities. Glioblastoma is armed with effective immunosuppressive properties resulting in an impaired recognition and ineffective attack of tumor cells by the immune system. In addition, extensive and diffuse invasion of tumor cells into the surrounding brain tissue limits the efficacy of local therapies. Here, 4IgB7H3 is assessed as diagnostic and therapeutic target for glioblastoma. EXPERIMENTAL DESIGN: To characterize B7H3 in glioblastoma, we conduct analyses not only in glioma cell lines and glioma-initiating cells but also in human glioma tissue specimens. RESULTS: B7H3 expression by tumor and endothelial cells correlates with the grade of malignancy in gliomas and with poor survival. Both soluble 4IgB7H3 in the supernatant of glioma cells and cell-bound 4IgB7H3 are functional and suppress natural killer cell-mediated tumor cell lysis. Gene silencing showed that membrane and soluble 4IgB7H3 convey a proinvasive phenotype in glioma cells and glioma-initiating cells in vitro. These proinvasive and immunosuppressive properties were confirmed in vivo by xenografted 4IgB7H3 gene silenced glioma-initiating cells, which invaded significantly less into the surrounding brain tissue in an orthotopic model and by subcutaneously injected LN-229 cells, which were more susceptible to natural killer cell-mediated cytotoxicity than unsilenced control cells. CONCLUSIONS: Because of its immunosuppressive and proinvasive function, 4IgB7H3 may serve as a therapeutic target in the treatment of glioblastoma.

Gadofluorine M enhanced MRI in experimental glioma: superior and persistent intracellular tumor enhancement compared with conventional MRI.

PURPOSE: To compare conventional magnetic resonance imaging (MRI) techniques (T2-w and Gadolinium-DTPA-enhanced T1-w images) and Gadofluorine-M (GfM), a novel contrast agent in MRI, in murine gliomas. MATERIALS AND METHODS: Growth monitoring of murine gliomas (induced in mice) was performed on a 2.3 Tesla Bruker Biospec MRI unit. First all animals were investigated with conventional MRI techniques. In group I GfM was applied at an early stage of disease, in group II at a later stage. After injection of GfM follow-up MRI was performed without further injection of contrast agent. On MR images tumor size and signal intensities were assessed. Animals were killed for histological evaluation. RESULTS: In both groups GfM delineated tumor extents larger and more precisely than conventional MRI techniques. The difference between GfM and conventional MRI techniques reached level of significance at both tumor stages. Follow-up MRI after singular injection of GfM showed persistence of GfM in tumor tissue. On tissue sections GfM-enhancing areas corresponded closely to vital tumor tissue. GfM showed a mainly intracellular accumulation. CONCLUSION: Application of GfM resulted in superior delineation of experimental glioma compared with conventional MRI techniques. Thus, GfM bears a high potential in clinical application.

Defective p53 antiangiogenic signaling in glioblastoma.

Previous findings suggest an angiogenesis-regulating function of the p53 tumor suppressor protein in various malignancies. With several antiangiogenic agents entering the clinic, we assessed the value of the TP53 status in predicting angiogenesis in glioblastoma in vivo and examined underlying angiogenic-signaling pathways in vitro. We identified 26 TP53 wild-type and 9 TP53 mutated treatment-naïve, primary, isocitrate dehydrogenase 1 (IDH1) wild-type glioblastoma specimens by sequence analysis and quantified vascularization. P53 responsiveness of the angiogenesis-related target genes, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), thrombospondin 1 (TSP-1), brain-specific angiogenesis inhibitor 1 (BAI1), and collagen prolyl-4-hydroxylase alpha 2 (P4HA2), was evaluated by (i) overexpression of wild-type p53 in homozygously TP53-deleted LN-308 cells; (ii) shRNA-mediated p53 knockdown in the TP53 wild-type LNT-229 cells; and (iii) chemical induction of wild-type p53 expression in LNT-229 cells by camptothecin. Irrespective of the TP53 status, vascularization did not differ significantly between the two groups of glioblastoma specimens. Of all target genes, only P4HA2 mRNA was upregulated through wild-type p53. As opposed to several nonglial tumors, in glioblastoma cells, p53-mediated transcriptional induction of P4HA2 mRNA neither resulted in increased levels of P4HA2 protein or antiangiogenic endostatin nor did it influence endothelial cell sprouting, viability, or transmigration in vitro. Moreover, p53-uncoupled stable overexpression of P4HA2 in LN-308 cells did not affect endothelial cell viability. These data challenge the view of p53 as an angiogenesis-regulator in glioblastoma in that relevant signaling pathways are silenced, potentially contributing to the angiogenic switch during malignant progression.