Human Glioblastoma Models Research Articles

Photoacoustic imaging of integrin-overexpressing tumors using a novel ICG-based contrast agent in mice

PhotoAcoustic Imaging (PAI) is a biomedical imaging modality currently under evaluation in preclinical and clinical settings. In this work, ICG is coupled to an integrin binding vector (ICG-RGD) to combine the good photoacoustic properties of ICG and the favourable αvβ3-binding capabilities of a small RGD cyclic peptidomimetic. ICG-RGD is characterized in terms of physicochemical properties, biodistribution and imaging performance. Tumor uptake was assessed in subcutaneous xenograft mouse models of human glioblastoma (U-87MG, high αvβ3 expression) and epidermoid carcinoma (A431, low αvβ3 expression). ICG and ICG-RGD showed high PA signal in tumors already after 15 min post-injection. At later time points the signal of ICG rapidly decreased, while ICG-RGD showed sustained uptake in U-87MG but not in A431 tumors, likely due to the integrin-mediated retention of the probe. In conclusion, ICG-RGD is a novel targeted contrast agents for PAI with superior biodistribution, tumor uptake properties and diagnostic value compared to ICG.

PO-411 Combinatorial therapy with immune checkpoint blockade and theranostic tumor-targeted nanoparticles in eradication of tumours

IntroductionTargeted superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as a promising detection tool for the molecular magnetic resonance imaging (MRI). Decoration of the surface with specific moieties that have anti-tumour immunotherapeutic activity could provide a theranostic potential for the nanocomplexes. Combination of functionalized particles with blocking of immune checkpoint inhibitors could further enhance the therapeutic benefit.Material and methodsSynthesised nanoparticles conjugated with granzyme B (GrB-SPIONs) were in vitro assessed (employing confocal and electron microscopies, flow cytometry) for specific targeting of the membrane-bound Hsp70 in cancer cells. Application of GrB-SPIONs as a monotherapy or in combination with single dose (10Gy) radiotherapy (SARRP, X-strahl) was performed in the orthotopic models of human U87 glioblastoma in NMRI nu/nu mice, GL261 glioma in C57/Bl6 mice, C6 glioma in rats. Combinatorial therapy of anti-CTLA-4 and anti-PD-1 anitbodies with GrB-SPIONs and radiotherapy was performed.Results and discussionsInternalised GrB-SPIONs in Hsp70-positive tumour cells induced apoptotic death in dose- and time-dependent manner (as shown by flow cytometry). Monotherapy with GrB-SPIONs in animal models resulted in delayed tumour progression (MRI volumometry) and increased survival. Biodistribution analysis employing highly sensitive non-linear magnetic response measurements (NLR-M2) confirmed the retention of particles in the tumour (that was further proved by histological studies). Addition of radiotherapy further promoted therapeutic benefit of systemically administered nanoparticles. Subsequent therapy with anti-CTLA-4 and anti-PD-1 antibodies synergistically improved the efficacy of GrB-SPIONs nanocomplexes with radiotherapy. Inhibitory immune checkpoint blockade significantly enhanced inflitration of tumour tissue with activated CD8 +and natural killer (NK1.1) cells and decreased suppressive PD-1 +cells.ConclusionThese findings reveal that GrB-SPIONs can specifically target Hsp70-positive cancer cells that could be used simultaneously for nonivasive MRI diagnosis of tumours and therapy. Combinatorial regimen of targeted nanocomplexes and immune checkpoint inhibitors has a high theraputic potency that could be translated into clinial trials.

Reverting the molecular fingerprint of tumor dormancy as a therapeutic strategy for glioblastoma.

Glioblastoma is an aggressive and invasive brain malignancy with high mortality rates despite current treatment modalities. In this study, we show that a 7-gene signature, previously found to govern the switch of glioblastomas from dormancy to aggressive tumor growth, correlates with improved overall survival of patients with glioblastoma. Using glioblastoma dormancy models, we validated the role of 2 genes from the signature, thrombospondin-1 ( TSP-1) and epidermal growth factor receptor ( EGFR), as regulators of glioblastoma dormancy and explored their therapeutic potential. EGFR up-regulation was reversed using EGFR small interfering RNA polyplex, antibody, or small-molecule inhibitor. The diminished function of TSP-1 was augmented via a peptidomimetic. The combination of EGFR inhibition and TSP-1 restoration led to enhanced therapeutic efficacy in vitro, in 3-dimensional patient-derived spheroids, and in a subcutaneous human glioblastoma model in vivo. Systemic administration of the combination therapy to mice bearing intracranial murine glioblastoma resulted in marginal therapeutic outcomes, probably due to brain delivery challenges, p53 mutation status, and the aggressive nature of the selected cell line. Nevertheless, this study provides a proof of concept for exploiting regulators of tumor dormancy for glioblastoma therapy. This therapeutic strategy can be exploited for future investigations using a variety of therapeutic entities that manipulate the expression of dormancy-associated genes in glioblastoma as well as in other cancer types.-Tiram, G., Ferber, S., Ofek, P., Eldar-Boock, A., Ben-Shushan, D., Yeini, E., Krivitsky, A., Blatt, R., Almog, N., Henkin, J., Amsalem, O., Yavin, E., Cohen, G., Lazarovici, P., Lee, J. S., Ruppin, E., Milyavsky, M., Grossman, R., Ram, Z., Calderón, M., Haag, R., Satchi-Fainaro, R. Reverting the molecular fingerprint of tumor dormancy as a therapeutic strategy for glioblastoma.

Moesin Up-regulation Is Associated with Enhanced Tumor Progression Imaged Non-invasively in an Orthotopic Mouse Model of Human Glioblastoma.

Glioblastoma is a recalcitrant and poorly understood disease. The aim of the present study was to investigate the effect of moesin up-regulation on tumor progression in an orthotopic nude-mouse model of human glioblastoma. U87-GFP glioblastoma cells, transfected with either U87-H4645 (moesin up-regulated) or U87-H149 (vector control) were orthotopically implanted into the brains of nude mice. Moesin expression in the tumors was analyzed with RT-PCR and western blotting. Real-time fluorescence imaging was used to longitudinally and non-invasively quantitate tumor growth. The expression of cancer-related genes β-catenin, CD44, MMP-2, ICAM-1, and PCNA in the tumor was analyzed by RT-PCR, western blotting and immunohistochemistry in both sublines. The expression levels of moesin mRNA and protein were significantly increased in the glioblastoma derived from transfected U87-H4645 cells compared to the vector control and untransfected cells. Tumor growth rate and final tumor weight were significantly increased in the animals with the glioblastoma derived from transfected U87-H4645 cells, compared to untransfected and vector control (p<0.01). mRNA expression of β-catenin, CD44, ICAM-1, and MMP-2 in the glioblastoma derived from the transfected U87-H4645 tumors was significantly increased compared with tumors derived from untransfected and vector-control U87 cells (p<0.01). Furthermore, a similar increase in the expression of these proteins was observed by western blotting or immunohistochemistry. Up-regulation of moesin expression in glioblastoma cells resulted in more aggressive orthotopic glioblastoma growth in nude mice. This effect may be mediated by the regulation of several proliferation-, adhesion-, and invasion-related cancer genes, which may serve as future therapeutic targets for this recalcitrant disease.

Comparison and evaluation of two RGD peptides labelled with 68Ga or 18F for PET imaging of angiogenesis in animal models of human glioblastoma or lung carcinoma.

The aim of this study was to evaluate two RGD radiotracers radiolabelled with fluorine-18 or gallium-68, in detecting angiogenesis in grafted human tumours and monitoring their treatment with the anti-angiogenic agent bevacizumab.Sixteen mice bearing an U87MG tumour in one flank and a contralateral A549 tumour were treated with intravenous injections of bevacizumab twice a week for 3 weeks. PET images with 18F-RGD-K5 and 68Ga-RGD were acquired before treatment (baseline), after three bevacizumab injections (t1) and after seven bevacizumab injections (t2).In A549 tumours, the treatment stopped the tumour growth, with a tumour volume measured by calliper remaining between 0.28 and 0.40 cm3. The decrease in tumour uptake of both RGD tracers was non-significant. Therefore it was not possible to predict this efficacy on tumour growth based on RGD PET results, whereas ex vivo measurements showed a significantly lower tumour uptake of both tracers in mice sacrificed at t2 vs. at baseline.In U87MG tumours, the uptake measured on PET decreased during treatment, reflecting the partial therapeutic effect observed on tumour volume, consisting in a decrease in the slope of tumour growth. Using 18F-RGD-K5, this decrease in tumour SUVmax became significant at t1, whereas it was also observed with the 68Ga-RGD tracer, but only at t2. 18F-RGD-K5 appeared more efficient than 68Ga-RGD in the visualisation and follow-up of U87MG tumours.The comparison of those results with those of immunohistochemistry at baseline and at t2 favoured the hypothesis that tumour RGD uptake reflects other cancer properties than just its angiogenic capacity.

NKG2D-Dependent Antitumor Effects of Chemotherapy and Radiotherapy against Glioblastoma.

Purpose: NKG2D is a potent activating immune cell receptor, and glioma cells express the cognate ligands (NKG2DL). These ligands are inducible by cellular stress and temozolomide (TMZ) or irradiation (IR), the standard treatment of glioblastoma, could affect their expression. However, a role of NKG2DL for the efficacy of TMZ and IR has never been addressed.Experimental Design: We assessed the effect of TMZ and IR on NKG2DL in vitro and in vivo in a variety of murine and human glioblastoma models, including glioma-initiating cells, and a cohort of paired glioblastoma samples from patients before and after therapy. Functional effects were studied with immune cell assays. The relevance of the NKG2D system for the efficacy of TMZ and IR was assessed in vivo in syngeneic orthotopic glioblastoma models with blocking antibodies and NKG2D knockout mice.Results: TMZ or IR induced NKG2DL in vitro and in vivo in all glioblastoma models, and glioblastoma patient samples had increased levels of NKG2DL after therapy with TMZ and IR. This enhanced the immunogenicity of glioma cells in a NGK2D-dependent manner, was independent from cytotoxic or growth inhibitory effects, attenuated by O6-methylguanine-DNA-methyltransferase (MGMT), and required the DNA damage response. The survival benefit afforded by TMZ or IR relied on an intact NKG2D system and was decreased upon inhibition of the NKG2D pathway.Conclusions: The immune system may influence the activity of convential cancer treatments with particular importance of the NKG2D pathway in glioblastoma. Our data provide a rationale to combine NKG2D-based immunotherapies with TMZ and IR. Clin Cancer Res; 24(4); 882-95. ©2017 AACR.

Optimization of IL13Rα2-Targeted Chimeric Antigen Receptor T Cells for Improved Anti-tumor Efficacy against Glioblastoma.

T cell immunotherapy is emerging as a powerful strategy to treat cancer and may improve outcomes for patients with glioblastoma (GBM). We have developed a chimeric antigen receptor (CAR) Tcell immunotherapy targeting IL-13 receptor α2 (IL13Rα2) for the treatment of GBM. Here, we describe the optimization of IL13Rα2-targeted CAR Tcells, including the design of a 4-1BB (CD137) co-stimulatory CAR (IL13BBζ) and a manufacturing platform using enriched central memory Tcells. Utilizing orthotopic human GBM models with patient-derived tumor sphere lines in NSG mice, we found that IL13BBζ-CAR Tcells improved anti-tumor activity and Tcell persistence as compared to first-generation IL13ζ-CAR CD8+ Tcells that had shown evidence for bioactivity in patients. Investigating the impact of corticosteroids, given their frequent use in the clinical management of GBM, we demonstrate that low-dose dexamethasone does not diminish CAR Tcell anti-tumor activity invivo. Furthermore, we found that local intracranial delivery of CAR Tcells elicits superior anti-tumor efficacy as compared to intravenous administration, with intraventricular infusions exhibiting possible benefit over intracranial tumor infusions in a multifocal disease model. Overall, these findings help define parameters for the clinical translation of CAR Tcell therapy for the treatment of brain tumors.

SCO-spondin oligopeptide inhibits angiogenesis in glioblastoma.

Angiogenesis plays a critical role in glioblastoma growth and progression. We therefore aimed at evaluating the anti-angiogenic properties of an oligopeptide originating from SCO-spondin (NX) on a model of human glioblastoma. To this end, we studied the impact of NX treatment on human brain endothelial cells (HBMECs) alone or co-cultured with glioblastoma cells (U87-MG) on apoptosis, proliferation, migration and release of angiogenic factors. We further investigated the anti-angiogenic potential of NX on human glioblastoma cells grown on chorio-allantoic membrane (CAM) or in glioblastoma xenografts.The results of our experiments showed that NX treatment impaired the microvascular network and induced a decrease in cell proliferation, vascularization and tumor growth in the CAM model as well as in xenotransplants. Interestingly, our in vitro experiments showed that NX impairs HBMECs migration but also regulates the release of angiogenic factors from U87-MG. These results are confirmed by the profiling of NX-treated U87-MG grown on CAM that highlighted modifications of several genes involved in angiogenesis.In conclusion, NX inhibits tumorigenesis by impairing the ability of glioblastoma cells to induce angiogenesis and by inhibiting endothelial cell migration. This molecule might therefore be an interesting candidate for future cancer therapies.

1662P - Synergistic antitumor effects of OT-101 (trabedersen), a transforming growth factor-beta 2 (TGF-β2) antisense oligonucleotide (ASO) and chemotherapy in preclinical tumor models

Background: Overexpression of TGF-β2 has been implicated in the malignant progression of tumors by inducing immunosuppression, proliferation, angiogenesis and metastasis. OT-101 (Trabedersen) is a phosphorothioate ASO designed to specifically target human TGF-β2 mRNA. Herein, we report the synergizing effect of OT-101 with chemotherapy in multiple human tumor xenograft models for further exploration of clinical combination strategies. Methods: OT-101 was administered as single agent (1-64 mg/kg, qdx3/wk or qdx21) and in combination with Gemcitabine (GEM, 15 mg/kg, qdx2/wk), Dacarbazine (DTIC, 1-10 mg/kg, qdx4/wk) or Paclitaxel (PTX, 10 mg/kg, qdx5) to nude mice (10/subgroup) bearing either (i) orthotopic human L3.6pl pancreatic cancer (PAC), (ii) human metastatic C8161 melanoma, (iii) SC glioblastoma (U87) or (iv) SC ovarian (SKOV-3) tumors. Mice were monitored for adverse effects, body weight loss, tumor size and survival outcome. Lymph node and liver surface and micro-metastases as well as size and weight of the pancreatic tumors were determined. Tumor sections were stained with anti-BrdUrd and CD31 antibodies to determine tumor cell proliferation and vascularization, respectively. Results: OT-101 significantly reduced tumor growth (p = 0.0084), lymph node metastasis (p = 0.023), and tumor angiogenesis (p < 0.0001) versus untreated control in the PAC model. OT-101 demonstrated synergy in tumor growth inhibition and increased survival in human malignant melanoma (C8161, p = 0.038, vs. DTIC alone), glioblastoma (U87, p = 0.001 vs. PTX) and ovarian (SKOV-3, p < 0.05 vs. PTX) cancer models when combined with either DTIC (C8161) or PTX (U87 and SKOV-3). No synergy was observed with GEM (PAC). The combination regimen tested was effective and tolerable. Significant antitumor activity was achieved at HED of 80 mg/m2/day which is well below the optimized clinical dose used for IV infusion of patients at 140 mg/m2/day. Conclusions: The preclinical data laid the groundwork for establishing combination therapies in the clinic. Of interest is the preferential synergy between OT-101 and PTX or DTIC, but not with GEM. Legal entity responsible for the study: Autotelic Inc Funding: None Disclosure: All authors have declared no conflicts of interest.

Tumor response of temozolomide in combination with morphine in a xenograft model of human glioblastoma.

Despite multimodal treatments comprising, radiation therapy (RT) and chemotherapy with temozolomide (TMZ), the prognosis of glioblastoma multiforme (GBM) remains dismal and consolidated therapy yields a median survival of 14.6 months.Blood Brain Barrier (BBB) mediated chemoresistance and high dose related toxicity make necessary the development of new therapeutic approach to sensitize GBM to TMZ.The aim of the present study was to investigate the potential of the treatment morphine plus TMZ metronmic doses (1,77 and 0,9 mg/kg) in GBM therapy.The effect of morphine, on tumor cell growth and P-glycoprothein (P-gp) activity, was investigate in in vitro models.The results demonstrated that GBM cells growth is not influenced by morphine treatment and, for the first time, we show that morphine is an inhibitor of the activity of P-gp efflux transporter who is markedly expressed on BBB.In vivo, response to the treatments TMZ plus morphine was investigated in an orthotopic nude mice model of GBM.Animals treated with TMZ metronomic doses showed a significant tumor growth inhibition compared to untreated mice and association with morphine appears to improve TMZ efficacy.Moreover, the combination of morphine with lower dose of TMZ result in a cytostatic effect on tumor growth over the period of the pharmacological treatments.In conclusion this novel approach could be a successful strategy to overcome chemoresistance and side effects TMZ mediated, reducing drug dosage and improving long term response, in GBM therapy.

Abstract 2800: Transforming growth factor-beta 2 (TGF-β2) antisense oligonucleotide (ASO) OT-101 synergizes with chemotherapy in preclinical tumor models

Abstract Background: Overexpression of TGF-β2 has been implicated in the malignant progression of tumors by inducing immunosuppression, proliferation, angiogenesis and metastasis. Clinical failures of TGF-β inhibitors in targeting the tumor promoting arm of TGF-β signaling is attributed to multiple isoforms and receptor functions. OT-101 (Trabedersen) is a phosphorothioate ASO designed to specifically target human TGF-β2 mRNA with superior clinical activity in patients with TGF-β2-overexpressing tumors. Herein, we report the synergizing effect of OT-101 with chemotherapy in multiple human tumor xenograft models for further exploration of clinical combinations. Methods: The in vivo efficacy studies of intraperitoneal (IP, 16 or 50 mg/kg) or subcutanous (SC, 1-64 mg/kg) repeated administration (qdx3/wk or qdx21) of OT-101 as single agent and in combination with Gemcitabine (15 mg/kg, qdx2/wk, IP), Dacarbazine (1-10 mg/kg, qdx4/wk, IP) or Paclitaxel (10 mg/kg, qdx5, IV) were evaluated in nude mice (10/subgroup) bearing either (i) orthotopic human L3.6pl pancreatic cancer (PAC), (ii) human metastatic C8161 melanoma, (iii) subcutaneous glioblastoma (U87-MG) or (iv) subcutaneous ovarian (SK-OV-3) tumors. Mice were monitored thrice a week for adverse effects, body weight loss, tumor size and survival outcome. The incidence of lymph node and liver surface and micro-metastases as well as size and weight of the pancreatic tumors were determined. Tumor sections were stained with anti-5-bromo-2'-deoxy-uridine antibody to determine tumor cell proliferation and with anti-CD31/PECAM-1 antibody to determine vascularization. Results: OT-101 significantly reduced tumor growth (p = 0.0084), lymph node metastasis (p = 0.023), and tumor angiogenesis (p &amp;lt;0.0001) in the orthotopic PAC model. Mean tumor vessel density was significantly reduced (p &amp;lt;0.0001) in all groups in comparison to untreated control. OT-101 demonstrated synergy in tumor growth inhibition and increased survival in human malignant melanoma (C8161, p = 0.038, vs. Dacarbazine alone), glioblastoma (U87-MG, p = 0.001 vs. Paclitaxel) and ovarian (SKOV-3, p &amp;lt;0.05 vs. Paclitaxel) cancer models when combined with either Dacarbazine (C8161) or Paclitaxel (U87-MG and SK-OV-3). No syngergy was observed with Gemcitabine (PAC). The combination regimen tested was effective and tolerable. Significant antitumor activity was achieved at human dose equivalent of 80 mg/m2/day which is well below the optimized clinical dose used for IV infusion of patients at 140 mg/m2/day. Conclusions: The preclinical data lay the groundwork for further exploration of combination therapy in the clinic as well as demonstrating that TGF-β2 is a druggable target. Of interest is the preferential synergy between OT-101 and Paclitaxel or Dacarbazine, but not with Gemcitabine. Citation Format: Osmond D'Cruz, Cynthia Lee, Vuong Trieu, Larn Hwang. Transforming growth factor-beta 2 (TGF-β2) antisense oligonucleotide (ASO) OT-101 synergizes with chemotherapy in preclinical tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2800. doi:10.1158/1538-7445.AM2017-2800

Combination Treatment with the GSK-3 Inhibitor 9-ING-41 and CCNU Cures Orthotopic Chemoresistant Glioblastoma in Patient-Derived Xenograft Models

Resistance to chemotherapy remains a major challenge in the treatment of human glioblastoma (GBM). Glycogen synthase kinase-3β (GSK-3β), a positive regulator of NF-κB–mediated survival and chemoresistance of cancer cells, has been identified as a potential therapeutic target in human GBM. Our objective was to determine the antitumor effect of GSK-3 inhibitor 9-ING-41 in combination with chemotherapy in patient-derived xenograft (PDX) models of human GBM. We utilized chemoresistant PDX models of GBM, GBM6 and GBM12, to study the effect of 9-ING-41 used alone and in combination with chemotherapy on tumor progression and survival. GBM6 and GBM12 were transfected by reporter constructs to enable bioluminescence imaging, which was used to stage animals prior to treatment and to follow intracranial GBM tumor growth. Immunohistochemical staining, apoptosis assay, and immunoblotting were used to assess the expression of GSK-3β and the effects of treatment in these models. We found that 9-ING-41 significantly enhanced 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) antitumor activity in staged orthotopic GBM12 (no response to CCNU) and GBM6 (partial response to CCNU) PDX models, as indicated by a decrease in tumor bioluminescence in mouse brain and a significant increase in overall survival. Treatment with the combination of CCNU and 9-ING-41 resulted in histologically confirmed cures in these studies. Our results demonstrate that the GSK-3 inhibitor 9-ING-41, a clinical candidate currently in Investigational New Drug (IND)-enabling development, significantly enhances the efficacy of CCNU therapy for human GBM and warrants consideration for clinical evaluation in this difficult-to-treat patient population.

An immunocompetent mouse model of human glioblastoma.

Orthotopic xenotransplantation studies represent the final stage in preclinical cancer research and could facilitate the implementation of precision medicine. To date, these xenografts have been tested in immunodeficient animals, but complete elimination of the adaptive immunity is a significant drawback. We present a method of efficient human glioblastoma (GBM) cell engraftment in adult mice with intact immune systems, mediated by a transient blockade of T-cell co-stimulation. Compared to transplants grown in immunodeficient hosts, the resulting tumors more accurately resemble the clinical pathophysiology of patient GBMs, which are characterized by blood-brain-barrier leakage and strong neo-vascularization. We expect our method to have great utility for studying human tumor cell biology, particularly in the field of cancer immunotherapy and in studies on microenvironmental interactions. Given the straightforward approach, the method may also be applicable to other tumor types and additional model organisms.

Human Neural Stem Cell Biodistribution and Predicted Tumor Coverage by a Diffusible Therapeutic in a Mouse Glioma Model.

Engineered neural stem cells (NSCs) intrinsically migrating to brain tumors offer a promising mechanism for local therapeutic delivery. However, difficulties in quantitative assessments of NSC migration and in estimates of tumor coverage by diffusible therapeutics have impeded development and refinement of NSC‐based therapies. To address this need, we developed techniques by which conventional serial‐sectioned formalin‐fixed paraffin‐embedded (FFPE) brains can be analyzed in their entirety across multiple test animals. We considered a conventional human glioblastoma model: U251 glioma cells orthotopically engrafted in immunodeficient mice receiving intracerebral (i.c.) or intravenous (i.v.) administrations of NSCs expressing a diffusible enzyme to locally catalyze chemotherapeutic formation. NSC migration to tumor sites was dose‐dependent, reaching 50%–60% of total administered NSCs for the i.c route and 1.5% for the i.v. route. Curiously, the most efficient NSC homing was seen with smaller NSC doses, implying existence of rate‐limiting process active during administration and/or migration. Predicted tumor exposure to a diffusing therapeutic (assuming a 50 µm radius of action) could reach greater than 50% of the entire tumor volume for i.c. and 25% for i.v. administration. Within individual sections, coverage of tumor area could be as high as 100% for i.c. and 70% for i.v. routes. Greater estimated therapeutic coverage was observed for larger tumors and for larger tumor regions in individual sections. Overall, we have demonstrated a framework within which investigators may rationally evaluate NSC migration to, and integration into, brain tumors, and therefore enhance understanding of mechanisms that both promote and limit this therapeutic modality. Stem Cells Translational Medicine 2017;6:1522–1532

The transcription factor PPARα is overexpressed and is associated with a favourable prognosis in IDH-wildtype primary glioblastoma.

PPARα agonists are in current clinical use as hypolipidaemic agents and show significant antineoplastic effects in human glioblastoma models. To date however, the expression of PPARα in large-scale glioblastoma datasets has not been examined. We aimed to investigate the expression of the transcription factor PPARα in primary glioblastoma, the relationship between PPARα expression and patients' clinicopathological features and other molecular markers associated with gliomagenesis. With protein immunoblotting techniques and reverse transcription quantitative real-time PCR, PPARα was found to be significantly overexpressed in glioblastoma compared with control brain tissue (P = 0.032 and P = 0.005). PPARA gene expression was found to be enriched in the classical glioblastoma subtype within The Cancer Genome Atlas (TCGA) dataset. Although not associated with overall survival when assessed by immunohistochemistry, cross-validation with the TCGA dataset and multivariate analyses identified PPARA gene expression as an independent prognostic marker for overall survival (P = 0.042). Finally, hierarchical clustering revealed novel, significant associations between high PPARA expression and a putative set of glioblastoma molecular mediators including EMX2, AQP4, and NTRK2. PPARα is overexpressed in primary glioblastoma and high PPARA expression functions as an independent prognostic marker in the glioblastoma TCGA dataset. Further studies are required to explore genetic associations with high PPARA expression and to analyse the predictive role of PPARα expression in glioblastoma models in response to PPARα agonists.

Preclinical development of a humanized neutralizing antibody targeting HGF

Hepatocyte growth factor (HGF) and its receptor, cMET, play critical roles in cell proliferation, angiogenesis and invasion in a wide variety of cancers. We therefore examined the anti-tumor activity of the humanized monoclonal anti-HGF antibody, YYB-101, in nude mice bearing human glioblastoma xenografts as a single agent or in combination with temozolomide. HGF neutralization, The extracellular signal-related kinases 1 and 2 (ERK1/2) phosphorylation, and HGF-induced scattering were assessed in HGF-expressing cell lines treated with YYB-101. To support clinical development, we also evaluated the preclinical pharmacokinetics and toxicokinetics in cynomolgus monkeys, and human and cynomolgus monkey tissue was stained with YYB-101 to test tissue cross-reactivity. We found that YYB-101 inhibited cMET activation in vitro and suppressed tumor growth in the orthotopic mouse model of human glioblastoma. Combination treatment with YYB-101 and temozolomide decreased tumor growth and increased overall survival compared with the effects of either agent alone. Five cancer-related genes (TMEM119, FST, RSPO3, ROS1 and NBL1) were overexpressed in YYB-101-treated mice that showed tumor regrowth. In the tissue cross-reactivity assay, critical cross-reactivity was not observed. The terminal elimination half-life was 21.7 days. Taken together, the in vitro and in vivo data demonstrated the anti-tumor efficacy of YYB-101, which appeared to be mediated by blocking the HGF/cMET interaction. The preclinical pharmacokinetics, toxicokinetics and tissue cross-reactivity data support the clinical development of YYB-101 for advanced cancer.

Glioblastoma Therapy Can Be Augmented by Targeting IDH1-Mediated NADPH Biosynthesis.

NADPH is a critical reductant needed in cancer cells to fuel the biosynthesis of deoxynucleotides and antioxidants and to sustain stress-survival responses after radiation-induced DNA damage. Thus, one rational strategy to attack cancer cells is to target their heavy reliance on NADPH. Here, we report that the isocitrate dehydrogenase IDH1 is the most strongly upregulated NADPH-producing enzyme in glioblastoma (GBM). IDH1 silencing in GBM cells reduced levels of NADPH, deoxynucleotides, and glutathione and increased their sensitivity to radiation-induced senescence. Rescuing these metabolic restrictions was sufficient to reverse IDH1-mediated radiosensitization. In a murine xenograft model of human GBM, we found that IDH1 silencing significantly improved therapeutic responses to fractionated radiotherapy, when compared with either treatment alone. In summary, our work offers a mechanistic rationale for IDH1 inhibition as a metabolic strategy to improve the response of GBM to radiotherapy. Cancer Res; 77(4); 960-70. ©2016 AACR.

The brain-penetrating CXCR4 antagonist, PRX177561, increases the antitumor effects of bevacizumab and sunitinib in preclinical models of human glioblastoma

BackgroundGlioblastoma recurrence after treatment with the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab is characterized by a highly infiltrative and malignant behavior that renders surgical excision and chemotherapy ineffective. It has been demonstrated that anti-VEGF/VEGFR therapies control the invasive phenotype and that relapse occurs through the increased activity of CXCR4. We therefore hypothesized that combining bevacizumab or sunitinib with the novel CXCR4 antagonist, PRX177561, would have superior antitumor activity.MethodsThe effects of bevacizumab, sunitinib, and PRX177561 were tested alone or in combination in subcutaneous xenografts of U87MG, U251, and T98G cells as well as on intracranial xenografts of luciferase tagged U87MG cells injected in CD1-nu/nu mice. Animals were randomized to receive vehicle, bevacizumab (4 mg/kg iv every 4 days), sunitinib (40 mg/kg po qd), or PRX177561 (50 mg/kg po qd).ResultsThe in vivo experiments demonstrated that bevacizumab and sunitinib increase the in vivo expression of CXCR4, SDF-1α, and TGFβ1. In addition, we demonstrate that the co-administration of the novel brain-penetrating CXCR4 antagonist, PRX177561, with bevacizumab or sunitinib inhibited tumor growth and reduced the inflammation. The combination of PRX177561 with bevacizumab resulted in a synergistic reduction of tumor growth with an increase of disease-free survival (DSF) and overall survival (OS), whereas the combination of PRX177561 with sunitinib showed a mild additive effect.ConclusionsThe CXC4 antagonist PRX177561 may be a valid therapeutic complement to anti-angiogenic therapy, particularly when used in combination with VEGF/VEGFR inhibitors. Therefore, this compound deserves to be considered for future clinical evaluation.

Bacterial Carriers for Glioblastoma Therapy

Treatment of aggressive glioblastoma brain tumors is challenging, largely due to diffusion barriers preventing efficient drug dosing to tumors. To overcome these barriers, bacterial carriers that are actively motile and programmed to migrate and localize to tumor zones were designed. These carriers can induce apoptosis via hypoxia-controlled expression of a tumor suppressor protein p53 and a pro-apoptotic drug, Azurin. In a xenograft model of human glioblastoma in rats, bacterial carrier therapy conferred a significant survival benefit with 19% overall long-term survival of >100 days in treated animals relative to a median survival of 26 days in control untreated animals. Histological and proteomic analyses were performed to elucidate the safety and efficacy of these carriers, showing an absence of systemic toxicity and a restored neural environment in treated responders. In the treated non-responders, proteomic analysis revealed competing mechanisms of pro-apoptotic and drug-resistant activity. This bacterial carrier opens a versatile avenue to overcome diffusion barriers in glioblastoma by virtue of its active motility in extracellular space and can lead to tailored therapies via tumor-specific expression of tumoricidal proteins.

Characterization of the distribution, retention, and efficacy of internal radiation of 188Re-lipid nanocapsules in an immunocompromised human glioblastoma model.

Internal radiation strategies hold great promise for glioblastoma (GB) therapy. We previously developed a nanovectorized radiotherapy that consists of lipid nanocapsules loaded with a lipophilic complex of Rhenium-188 (LNC188Re-SSS). This approach resulted in an 83 % cure rate in the 9L rat glioma model, showing great promise. The efficacy of LNC188Re-SSS treatment was optimized through the induction of a T-cell immune response in this model, as it is highly immunogenic. However, this is not representative of the human situation where T-cell suppression is usually encountered in GB patients. Thus, in this study, we investigated the efficacy of LNC188Re-SSS in a human GB model implanted in T-cell deficient nude mice. We also analyzed the distribution and tissue retention of LNC188Re-SSS. We observed that intratumoral infusion of LNCs by CED led to their complete distribution throughout the tumor and peritumoral space without leakage into the contralateral hemisphere except when large volumes were used. Seventy percent of the 188Re-SSS activity was present in the tumor region 24h after LNC188Re-SSS injection and no toxicity was observed in the healthy brain. Double fractionated internal radiotherapy with LNC188Re-SSS triggered survival responses in the immunocompromised human GB model with a cure rate of 50 %, which was not observed with external radiotherapy. In conclusion, LNC188Re-SSS can induce long-term survival in an immunosuppressive environment, highlighting its potential for GB therapy.