CT322, a VEGFR-2 antagonist, demonstrates anti-glioma efficacy in orthotopic brain tumor model as a single agent or in combination with temozolomide and radiation therapy.

Glioblastomas are among the most aggressive human cancers, and prognosis remains poor despite presently available therapies. Angiogenesis is a hallmark of glioblastoma, and the resultant vascularity is associated with poor prognosis. The proteins that mediate angiogenesis, including vascular endothelial growth factor (VEGF) signaling proteins, have emerged as attractive targets for therapeutic development. Since VEGF receptor-2 (VEGFR-2) is thought to be the primary receptor mediating angiogenesis, direct inhibition of this receptor may produce an ideal therapeutic effect. In this context, we tested the therapeutic effect of CT322, a selective inhibitor of VEGFR-2. Using an intracranial murine xenograft model (U87-EGFRvIII-luciferase), we demonstrate that CT322 inhibited glioblastoma growth in vivo and prolonged survival. Of note, the anti-neoplastic effect of CT322 is augmented by the incorporation of temozolomide or temozolomide with radiation therapy. Immunohistochemical analysis of CT322 treated tumors revealed decreased CD31 staining, suggesting that the tumoricidal effect is mediated by inhibition of angiogenesis. These pre-clinical results provide the foundation to further understand long term response and tumor escape mechanisms to anti-angiogenic treatments on EGFR over-expressing glioblastomas.

Dominant-negative inhibition of Ets 1 suppresses tumor growth, invasion and migration in rat C6 glioma cells and reveals differentially expressed Ets 1 target genes.

We previously reported that the inactivation of the Ets 1 transcription factor by a specific decoy strategy reduces rat C6 glioma cell proliferation and mmp-9 expression. In the present study, we analysed the effects of the dominant-negative form of Ets 1 (Ets-DB) on rat C6 glioma cell proliferation, migration, invasion, in vivo tumor growth on the chicken chorioallantoic membrane (CAM) and mmp-9 expression. In addition, we examined differences in gene expression between Ets-DB expressing and control cells using suppression subtractive hybridization (SSH). We found that retrovirus mediated expression of Ets-DB inhibited cellular proliferation, migration, invasion, mmp-9 expression, cellular growth in soft agar, and in vivo growth in the chicken chorioallantoic membrane assay. SSH analysis revealed expression of different genes in Ets-DB expressing cells involved in basic cellular processes. Each of these genes contained binding sites for different Ets-factors within their promoters. Finally, we found that, in addition to Ets 1, Elk-1, Elf-1, Fli-1 and Etv-1 are further Ets family members expressed in rat C6 glioma cells. Our results indicate that Ets transcription factors play important roles for basic properties of rat C6 glioma cells. Targeting of these factors might therefore become a useful experimental tool for therapeutic strategies against malignant gliomas.

Genetically engineered T cells to target EGFRvIII expressing glioblastoma.

Glioblastoma remains a significant therapeutic challenge, warranting further investigation of novel therapies. We describe an immunotherapeutic strategy to treat glioblastoma based on adoptive transfer of genetically modified T-lymphocytes (T cells) redirected to kill EGFRvIII expressing gliomas. We constructed a chimeric immune receptor (CIR) specific to EGFRvIII, (MR1-zeta). After in vitro selection and expansion, MR1-zeta genetically modified primary human T-cells specifically recognized EGFRvIII-positive tumor cells as demonstrated by IFN-gamma secretion and efficient tumor lysis compared to control CIRs defective in EGFRvIII binding (MRB-zeta) or signaling (MR1-delzeta). MR1-zeta expressing T cells also inhibited EGFRvIII-positive tumor growth in vivo in a xenografted mouse model. Successful targeting of EGFRvIII-positive tumors via adoptive transfer of genetically modified T cells may represent a new immunotherapy strategy with great potential for clinical applications.

Development of third generation anti-EGFRvIII chimeric T cells and EGFRvIII-expressing artificial antigen presenting cells for adoptive cell therapy for glioma.

Glioblastoma multiforme (GBM) is the most aggressive and deadly form of adult brain cancer. Despite of many attempts to identify potential therapies for this disease, including promising cancer immunotherapy approaches, it remains incurable. To address the need of improved persistence, expansion, and optimal antitumor activity of T-cells in the glioma milieu, we have developed an EGFRvIII-specific third generation (G3-EGFRvIII) chimeric antigen receptor (CAR) that expresses both co-stimulatory factors CD28 and OX40 (MR1-CD8TM-CD28-OX40-CD3ζ). To enhance ex vivo target specific activation and optimize T-cell culturing conditions, we generated artificial antigen presenting cell lines (aAPC) expressing the extracellular and transmembrane domain of EGFRvIII (EGFRVIIIΔ654) with costimulatory molecules including CD32, CD80 and 4-1BBL (EGFRVIIIΔ654 aAPC and CD32-80-137L-EGFRVIIIΔ654 aAPC). We demonstrate that the highest cell growth was achieved when G3-EGFRvIII CAR T-cells were cocultured with both co-stimulatory aAPCs and with exposure to EGFRvIII (CD32-80-137L-EGFRVIIIΔ654 aAPCs) in culturing periods of three to six weeks. G3-EGFRvIII CAR T-cells showed an increased level of IFN-γ when cocultured with CD32-80-137L-EGFRVIIIΔ654 aAPCs. Evaluation of G3-EGFRvIII CAR T-cells in an orthotropic human glioma xenograft model demonstrated a prolonged survival of G3-EGFRvIII CAR treated mice compared to control mice. Importantly, we observed survival of G3-EGFRvIII CAR T-cells within the tumor as long as 90 days after implantation in low-dose and single administration, accompanied by a marked tumor stroma demolition. These findings suggest that G3-EGFRvIII CAR cocultured with CD32-80-137L-EGFRVIIIΔ654 aAPCs warrants itself as a potential anti-tumor therapy strategy for glioblastoma.

Inactivation of Ets 1 transcription factor by a specific decoy strategy reduces rat C6 glioma cell proliferation and mmp-9 expression.

Malignant gliomas represent the most aggressive tumours of the central nervous system and are characterised by both extensive proliferation and invasive growth. Matrix degrading proteases called matrix metalloproteinases (MMPs), particularly MMP-9, play a crucial role in glioma infiltration. The activity of these enzymes is regulated at different levels. In this regard, the control of transcriptional activity by specific transcription factors is believed to be very important. In the present study, we examined whether rat C6 glioma cells express the Ets 1 transcription factor and whether inhibition of Ets 1 by a specific decoy strategy affects C6 glioma cell proliferation and mmp-9 expression. We found that C6 glioma cells express Ets 1 and can efficiently be transfected with an Ets 1-specific decoy oligodesoxynucleotide (ODN). This ODN significantly reduces cell proliferation and mmp-9 expression, the latter in a dose-dependent manner. We conclude that inhibition of transcription factors, which play a role for glioma development and progression such as Ets 1 by specific decoy approaches, might represent useful tools for experimental therapeutic strategies against malignant gliomas.

Suppression of human glioma xenografts with second-generation IL13R-specific chimeric antigen receptor-modified T cells.

PURPOSE: Glioblastoma multiforme (GBM) remains highly incurable, with frequent recurrences after standard therapies of maximal surgical resection, radiation, and chemotherapy. To address the need for new treatments, we have undertaken a chimeric antigen receptor (CAR) "designer T cell" (dTc) immunotherapeutic strategy by exploiting interleukin (IL)13 receptor α-2 (IL13Rα2) as a GBM-selective target. EXPERIMENTAL DESIGN: We tested a second-generation IL13 "zetakine" CAR composed of a mutated IL13 extracellular domain linked to intracellular signaling elements of the CD28 costimulatory molecule and CD3ζ. The aim of the mutation (IL13.E13K.R109K) was to enhance selectivity of the CAR for recognition and killing of IL13Rα2(+) GBMs while sparing normal cells bearing the composite IL13Rα1/IL4Rα receptor. RESULTS: Our aim was partially realized with improved recognition of tumor and reduced but persisting activity against normal tissue IL13Rα1(+) cells by the IL13.E13K.R109K CAR. We show that these IL13 dTcs were efficient in killing IL13Rα2(+) glioma cell targets with abundant secretion of cytokines IL2 and IFNγ, and they displayed enhanced tumor-induced expansion versus control unmodified T cells in vitro. In an in vivo test with a human glioma xenograft model, single intracranial injections of IL13 dTc into tumor sites resulted in marked increases in animal survivals. CONCLUSIONS: These data raise the possibility of immune targeting of diffusely invasive GBM cells either via dTc infusion into resection cavities to prevent GBM recurrence or via direct stereotactic injection of dTcs to suppress inoperable or recurrent tumors. Systemic administration of these IL13 dTc could be complicated by reaction against normal tissues expressing IL13Ra1.

Recombinant adeno-associated virus type 2 pseudotypes: comparing safety, specificity, and transduction efficiency in the primate striatum. Laboratory investigation.

OBJECT: Although several clinical trials utilizing the adeno-associated virus (AAV) type 2 serotype 2 (2/2) are now underway, it is unclear whether this particular serotype offers any advantage over others in terms of safety or efficiency when delivered directly to the CNS. METHODS: Recombinant AAV2-green fluorescent protein (GFP) serotypes 2/1, 2/2, 2/5, and 2/8 were generated following standard triple transfection protocols (final yield 5.4 × 10(12) particles/ml). A total of 180 µl of each solution was stereotactically infused, covering the entire rostrocaudal extent of the caudoputamen in 4 rhesus monkeys (Macaca mulatta) (3.0 ± 0.5 kg). After 6 weeks' survival, the brain was formalin fixed, cut at 40 µm, and stained with standard immunohistochemistry for anti-GFP, anticaspase-2, and cell-specific markers (anti-microtubule-associated protein-2 for neurons and anti-glial fibrillary acidic protein for glia). Unbiased stereological counting methods were used to determine cell number and striatal volume. RESULTS: The entire striatum of each animal contained GFP-positive cells with significant labeling extending beyond the borders of the basal ganglia. No ischemic/necrotic, hemorrhagic, or neoplastic change was observed in any brain. Total infusate volumes were similar across the 4 serotypes. However, GFP-labeled cell density was markedly different. Adeno-associated virus 2/1, 2/2, and 2/5 each labeled < 8000 cells/mm(3), whereas serotype 8 labeled > 21,000 cells, a 3- to 4-fold higher transduction efficiency. On the other hand, serotype 8 also labeled neurons and glia with equal affinity compared with neuronal specificities > 89% for the other serotypes. Moderate caspase-2 colabeling was noted in neurons immediately around the AAV2/1 injection tracts, but was not seen above the background anywhere in the brain following injections with serotypes 2, 5, or 8. CONCLUSIONS: Intrastriatal delivery of AAV2 yields the highest cell transduction efficiencies but lowest neuronal specificity for serotype 8 when compared with serotypes 1, 2, and 5. Only AAV2/1 revealed significant caspase-2 activation. Careful consideration of serotype-specific differences in AAV2 neurotropism, transduction efficiency, and potential toxicity may affect future human trials.