Breast cancer (BC) is the second most common source of metastatic lesions to the CNS, yet the mechanisms by which metastatic BC cells (BMET) survive in the brain remain poorly understood. Given their ...ability to regulate the expression of multiple mRNA targets, microRNAs (miRNA) may play a critical role. miRNA dysregulation has been observed in both primary and metastatic tumors, and can be actively exchanged between cancer cells and the surrounding stroma via extracellular vesicles (EVs). Our overall hypothesis is that microRNAs released by BMETs are important mediators of communication between tumor and stromal astrocytes (SAs), resulting in measurable changes to the miRNA and target gene expression profile of both donor and recipient cells. Identified miRNA signatures could serve as important biomarkers of metastatic potential and provide new targets for novel therapeutic interventions. Here, we use an in vitro co-culture model to characterize the miRNA signature of BMETs, SAs, and the EVs exchanged between them. We show that the mature miRNA expression profiles could reliably distinguish between BMETs cultured in isolation or co-cultured with astrocytes. Isolated EVs showed enrichment for a specific set of miRNAs, which were differentially expressed between BMETs and SAs. A subset of these miRNAs, not normally expressed in BMETs, was particularly abundant in EVs. They were not transcriptionally induced, implicating EV-mediated transport from SAs to BC cells. Bio-informatic analysis revealed multiple miRNA targets in the pro-apoptotic pathway, which were validated by qPCR and WB. Functional analysis revealed that over-expression protected cells from apoptosis, while miRNA-knockdown induced it. Thus, infiltrating BMETs can harness anti-apoptotic miRNAs from reactive astrocytes, thereby promoting survival and growth. This work identifies novel targets for therapeutic intervention, which could prevent micrometastases from progressing to clinically relevant lesions in the brain. These findings are currently being tested in vivo using a mouse xenograft model.
Abstract
Monotherapy with intratumoral Ad-RTS-hIL-12 (Ad), a novel gene therapeutic conditionally expressing IL-12 under the transcriptional control of oral veledimex (V, 20 mg) acting via the ...proprietary RheoSwitch Therapeutic System® (RTS®), was shown in a phase 1 Main study (NCT02026271) to elicit a sustained intra-tumoral activated cytotoxic T-cell response with co-expression of PD-1. Additionally, the Main study showed improved median overall survival (mOS), compared to historical controls, in subjects with recurrent glioblastoma (rGBM) receiving Ad + V. Herein, we report updated findings from on an ongoing open label, dose-escalation Phase 1 substudy (NCT03636477) evaluating safety and tolerability of local, controlled IL-12 plus nivolumab in adult subjects with rGBM. Ad was administered by single intratumoral injection (2 x 1011 viral particles) on Day 0 plus V (10 and 20 mg) PO QD x 15 with nivolumab (1 and 3mg/kg) IV on Days -7, 15, then Q2W. Subjects have been accrued into three cohorts and follow-up is ongoing. Data from all three cohorts regarding dose escalation of V and nivolumab will be presented. The initial safety profile during V dosing period was similar to Ad+V monotherapy with adverse reactions being dose-related and rapidly reversible upon discontinuation of V. And those adverse reactions during the follow on nivolumab dosing were tolerable and manageable and consistent with nivolumab labeling, with no synergistic toxicities, and drug-related deaths. In the first two cohorts (where data is available), combination therapy improved the biomarker “cytoindex” (ratio of circulating CD8+ T cells to FoxP3+ regulatory T cells). (In the Main study, cytoindex correlated with overall survival). Controlled IL-12 production using Ad+V with nivolumab is a rational combination with initial data consistent with immune-mediated anti-tumor effects with a favorable safety profile. Further phase 2 investigation of Ad+V plus a checkpoint inhibitor in rGBM is planned.
Abstract
BACKGROUND
We previously demonstrated that extracellular vesicles (EV) from CNS tumors reflect the molecular subtype of the original tumor and mediate an exchange of pro-oncogenic signals. ...EVs are commonly characterized by nanoparticle analysis (NTA), electron microscopy and tetraspanin markers, including CD9, CD81 and CD63. It is unclear, however, to what extent circulating tumor EVs are utilizable for diagnostic purposes and how their marker profile overlaps with EVs derived from other cell types. Aiming to define markers that allow distinction and enrichment of glioma EVs from patient blood, we utilized Imaging Flow Cytometry (IFC) to discriminate single EVs via multiple surface markers.
METHODS
EVs were isolated from blood of patients suffering from glioblastoma (n=24), anaplastic astrocytoma (n=8), brain metastasis (n=7), meningioma (n=12), pituitary gland tumor (n=11), epilepsy (n=11) and from healthy controls (n=18) and were analyzed by IFC, immunoblotting, electron microscopy and NTA. In addition, circulating EVs from PALM-GFP-GL261 and PALM-GFP-CT2A tumor-bearing mice (n=5) as well as from glioblastoma stem-like (GSC) cultures (n=4), neural stem cells (NSC), cerebral endothelial cells (cEC) and T-cells (n=4) were characterized.
RESULTS
CNS tumor patients have significantly elevated levels of circulating EVs (P < 0.001), as measured by NTA and IFC. In particular, the proportion of double positive CD9+/CD81+, CD9+/CD63+and CD63+/CD81+EVs is increased in glioblastoma patients (p=0.018) compared with healthy controlsL1. In accordance, cultured GSCs secrete increased levels of CD9+/CD81+EVs in vitro. In the two syngeneic murine PALM-GFP glioma models, only 0.1-0.01% of circulating plasma EVs were found to be derived from intracranial tumors, underlining the need to identify markers that can enrich tumor-specific EVs for molecular profiling.
CONCLUSION
Glioma patients display increased levels of circulating plasma EVs that can be profiled by IFC, which is a unique and novel technique that facilitates discrimination of different EV subpopulations.
Abstract
RATIONALE
Dexamethasone is frequently used in symptomatic treatment of glioma patients, although it is known to cause immune suppression. Checkpoint inhibitor immunotherapies have not yet ...been successful in glioma treatments. Gene-mediated cytotoxic immunotherapy (GMCI) is an immunotherapeutic approach that uses aglatimagene besadenovec with an anti-herpetic prodrug to induce immunogenic tumor cell death and immune cell attraction to the tumor site with potent CD8 T cell activation. GMCI is currently in clinical trials for solid tumors including glioblastoma, where it showed encouraging survival results in a Phase 2 study that did not limit the use of dexamethasone. However, the effects of dexamethasone on its efficacy have not been explored.
METHODS
We investigated the effects of dexamethasone on GMCI in vitro using cytotoxicity and T-cell-killing assays in glioblastoma cell lines. The impact of dexamethasone in vivo was assessed in an orthotopic syngeneic murine glioblastoma model.
RESULTS
Cyotoxicity assays showed that Dexamethasone has a slight impact on GMCI in vitro. In contrast, we observed a highly significant effect in T-cell-functional assays in which killing was greatly impaired. Immune cell response assays revealed a reduced T-cell proliferation after co-culture with supernatant from dexamethasone or combination treated glioblastoma cells in contrast to GMCI alone. In a murine model, the combination of GMCI and dexamethasone resulted in a significant reduction in median symptom-free survival (29d) in comparison to GMCI alone (39.5d) (P = 0.0184).
CONCLUSION
Our data suggest that high doses of dexamethasone may negatively impact the efficacy of immunotherapy for glioma, which may be a consequence of impaired T cell function. These results support the idea that there is a need in identifying possible alternatives to dexamethasone to maximize the effectiveness of immunostimulatory therapies such as GMCI.
The hypothesis that cytomegalovirus (CMV) modulates cancer is evolving. Originally discovered in glioblastoma in 2002, the number of cancers, where intratumoral CMV antigen is detected, has increased ...in recent years suggesting that CMV actively affects the pathobiology of certain tumors. These findings are controversial as several groups have also reported inability to replicate these results. Regardless, several clinical trials for glioblastoma are underway or have been completed that target intratumoral CMV with anti-viral drugs or immunotherapy. Therefore, a better understanding of the possible pathobiology of CMV in cancer needs to be ascertained. We have developed genetic, syngeneic, and orthotopic malignant glioma mouse models to study the role of CMV in cancer development and progression. These models recapitulate for the most part intratumoral CMV expression as seen in human tumors. Additionally, we discovered that CMV infection in Trp53(-/+) mice promotes pleomorphic rhabdomyosarcomas. These mouse models are not only a vehicle for studying pathobiology of the viral-tumor interaction but also a platform for developing and testing cancer therapeutics.
Abstract
Heterogeneous glioblastoma multiforme (GBM) was categorized based on transcriptional signatures into four subtypes (proneural (PN), neural, classical, and mesenchymal (MES)). In order to ...develop effective targeted therapeutic strategies, understanding the heterogeneous gene expression and molecular features of these subtypes is crucial. De-regulation of microRNA expression and activity has been shown to play an important role in tumor initiation and progression, including gliomagenesis. We have previously reported that expression of microRNA-128 (miR-128) is significantly down regulated in GBM and it diminishes self-renewal of GBM stem-like cells (GSCs) and sensitizes them to irradiation. Proneural-to-mesenchymal transition (PMT) manifested by concomitant up regulation of MES markers and down regulation of PN markers, is associated with increased malignancy, therapy-resistance and worse prognosis, but the underlying causes of PMT have not been convincingly characterized yet. In this study, we have demonstrated that miR-128 can regulate the PMT in GSC subsets. We showed that the expression of miR-128 in PN GSCs was significantly higher compared to MES subtype. As a tumor suppressive microRNA, miR-128 inhibited the MES GSC-specific high expression of Bmi1 and Suz12, two components of Polycomb Repressor Complexes (PRC) 1 and 2, respectively. In both GSC subtypes, miR-128 driven targeting of PRCs suppressed their epigenetic activity measured by ubiquitination of H2AK119 and tri-methylation of H3K27. Stable down regulation of miR-128 in PN GSCs significantly increased the expression of MES-specific gene signature (BCL2A1, CD44, WT-1, LYN, and MET) while its stable up regulation in MES GSCs resulted in the restoration of PN specific gene signature (CD133, SOX2, NES, OLIG2, and NOTCH1). We also showed that stable expression of miR-128 in GSCs could regulate the process of irradiation-induced PMT. Our in vivo studies showed the anti-tumorigenic role of miR-128 in both PN and MES GSC-derived intracranial tumor models. Taken together, we demonstrated that altering levels of miR-128 was sufficient to cause or reverse PMT, most likely by targeting the level/functions of PRCs and their target genes in GBM.
Citation Format: Arun K. Rooj, Marco Mineo, Franz Ricklefs, Agnieszka Bronisz, Ennio Chiocca, Jakub Godlewski. The novel role of microRNA-128 in proneural to mesenchymal subtype transition in glioblastoma stem cells by targeting components of pro-oncogenic Polycomb Repressor Complex. abstract. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1929.
Abstract
Glioblastomas (GBM) are highly invasive brain tumors that resist cytotoxic and antiangiogenic therapies, resulting in a high rate of recurrence. Fibulin-3 is an extracellular matrix protein ...secreted by GBM cells but absent from normal brain. This protein activates Notch signaling to promote tumor invasion and resistance to apoptosis. Conditional knockdown of fibulin-3 reduces GBM growth, invasion and vascularization, thus extending survival. Here we report the initial validation of a function-blocking antibody against this unique GBM target. We first identified the Notch-activating motif of fibulin-3 and developed an immunizing peptide against a key sequence within this motif. A monoclonal antibody generated against this peptide (mAb428.2) showed high affinity for fibulin-3 (Kd 5 nM) and no cross-reactivity against highly homologous fibulin-4 or -5. Antibody mAb428.2 detected fibulin-3 in the stroma and capillaries of human GBM without cross-reactivity against normal brain. The antibody (50-250 μg/ml) blocked the activation of Notch induced by fibulin-3 in GBM cells and caused GBM cell cytotoxicity but had no effects on astrocytes or HEK293 cells. Treatment of mice carrying subcutaneous GBM stem-cell (GSC) derived tumors with mAb428.2 (30 mg/kg IV, q24h x 8 days) resulted in tumor slowdown and extended median survival (47% and 64% in two different GSC models). mAb428.2-treated tumors showed decreased BrdU uptake and increased inflammatory reaction in the tumor stroma (macrophage infiltration and cytokine levels). Mice bearing intracranial tumors did not respond to mAb428.2 when delivered by IV or IP routes, likely due to the inability of the antibody to cross the blood brain barrier. This deficiency was overcome by direct intraparenchymal delivery of the mAb428.2 using chronic infusion (0.3 mg of mAb in 200 μl delivered at 1 μl/h over 7d), which resulted in a 26% increase in median survival. These encouraging results suggest that targeted reagents against fibulin-3 may be of clinical importance for novel combination therapies against GBM.
Citation Format: Mohan Sobhana Nandhu, Prajna Behera, Vivek Bhaskaran, Ennio Antonio Chiocca, Mariano S. Viapiano. Validation of a novel antibody against fibulin-3 for targeted therapy of glioblastoma. abstract. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3797.
Breast cancer (BC) is the second most common source of metastatic lesions to the CNS, yet the mechanisms by which metastatic BC cells (BMET) survive in the brain remain poorly understood. Given their ...ability to regulate the expression of multiple mRNA targets, microRNAs (miRNA) may play a critical role. miRNA dysregulation has been observed in both primary and metastatic tumors, and can be actively exchanged between cancer cells and the surrounding stroma via extracellular vesicles (EVs). Our overall hypothesis is that microRNAs released by BMETs are important mediators of communication between tumor and stromal astrocytes (SAs), resulting in measurable changes to the miRNA and target gene expression profile of both donor and recipient cells. Identified miRNA signatures could serve as important biomarkers of metastatic potential and provide new targets for novel therapeutic interventions. Here, we use an in vitro co-culture model to characterize the miRNA signature of BMETs, SAs, and the EVs exchanged between them. We show that the mature miRNA expression profiles could reliably distinguish between BMETs cultured in isolation or co-cultured with astrocytes. Isolated EVs showed enrichment for a specific set of miRNAs, which were differentially expressed between BMETs and SAs. A subset of these miRNAs, not normally expressed in BMETs, was particularly abundant in EVs. They were not transcriptionally induced, implicating EV-mediated transport from SAs to BC cells. Bio-informatic analysis revealed multiple miRNA targets in the pro-apoptotic pathway, which were validated by qPCR and WB. Functional analysis revealed that over-expression protected cells from apoptosis, while miRNA-knockdown induced it. Thus, infiltrating BMETs can harness anti-apoptotic miRNAs from reactive astrocytes, thereby promoting survival and growth. This work identifies novel targets for therapeutic intervention, which could prevent micrometastases from progressing to clinically relevant lesions in the brain. These findings are currently being tested in vivo using a mouse xenograft model.
Abstract
Ad-RTS-hIL-12 (Ad) is a novel gene therapy, conditionally expressing IL-12 via the RheoSwitch Therapeutic System® (RTS®) gene switch under control of an oral activator ligand, veledimex (V). ...We previously reported results from 51 subjects (NCT02026271 and NCT03679754) describing biological activity of controlled IL-12, safety and survival data. Previously, subjects who received Ad+V (20 mg) managed with low-dose dexamethasone in the Main study achieved a mOS of 17.8 months, which is approximately twice the anticipated survival compared to historical controls. The mechanism of action of Ad+V is based on controlled secretion of recombinant IL-12 (measured in peripheral blood as a surrogate for intra-tumor-production), downstream upregulation of endogenous IFN-g (measured in peripheral blood), and an increase in the “cytoindex” (ratio of circulating CD8+ T cells to FoxP3+ regulatory T cells), an emerging biomarker of overall survival. Herein we provide an update of subject characteristics, survival and biomarker analysis from the ongoing Phase 1 and expansion substudy. assessing safety and tolerability of local, inducible IL-12 by single intratumoral injection of Ad (2 x 1011 viral particles) + V (20 mg PO QD x15 doses Days 0–14) in subjects, including a subset receiving low-dose corticosteroids (≤20 mg cumulative dexamethasone Days 0–14). Drug-related toxicities were predictable, dose-related, and promptly reversible upon discontinuation of V with no drug-related deaths. Biomarker studies related to production of IL-12 and IFN-g, as well as cytoindex remain encouraging. As of 04Jun19, mOS in the Expansion substudy had not yet been reached (patient enrollment occurred from September 2018-February 2019). Most subjects (65%) received low-dose dexamethasone (cumulative ≤20mg Days 0–14); initial impact of this and other subject characteristics on survival will be presented.
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