Genes that Mediate Metastasis across the Blood-Brain Barrier

Brain metastasis is an important cause of mortality in patients with cancer and represents the majority of all intracranial tumors. A key step during the metastatic journey of the cancer cell to the brain is the invasion through the blood-brain barrier (BBB). Nevertheless, the molecular mechanisms that govern this process remain unknown. The BBB has been blamed for limiting the access of therapeutic drugs to the brain, which provides a safe haven for cancer cells in the brain and confers poor prognosis for the patient. Here, we explore the genes that control the transmigration of metastatic cancer cells across the BBB, offering new targets for the development of gene and cell therapies against brain metastases.

Evaluation of patient education materials for stereotactic radiosurgery from high-performing neurosurgery hospitals and professional societies

Background

Little is known about the readability and utility of patient education materials for stereotactic radiosurgery (SRS). Therefore, the goal of this investigation was to evaluate such materials from high-performing neurosurgery hospitals and professional societies through an analysis of readability and educational content.

Methods

In this cross-cross sectional study, 61 websites associated with the top 50 neurosurgery and neurology hospitals according to U.S. News & World Report (USNWR) and 11 predetermined professional medical societies were queried. Identified SRS education materials were analyzed by 6 readability indices. Educational content was assessed by 10 criteria based on surveys of patients' perspectives about SRS.

Results

Fifty-four materials were identified from the target population (45 from USNWR hospital websites and 9 from professional society websites). Mean readability of materials ranged from 11.7 to 15.3 grade level, far more difficult than national recommendations of sixth and eighth grade. Materials were found to have deficiencies in educational content. Compared with high-performing hospitals, materials from websites of professional societies were longer (P = .002), and more likely to discuss risks and benefits specific to SRS (P = .008), alternative treatment options (P = .05) and expected outcomes or postprocedure descriptions (P = .004). Hospital materials were also more likely to favor brand-specific terminology (eg, GammaKnife) over generic terminology (eg, radiosurgery; P = .019).

Conclusion

Publicly available online patient educational materials for SRS are written at reading levels above national recommendations. Furthermore, many lack information identified as important by patients. Reevaluation and improvement of online SRS educational materials on a national scale are warranted.

Abstract B95: PD-L1-mediated nanotherapeutic targeting of glioma-infiltrating myeloid cells synergizes with radiotherapy for glioblastoma

Massive infiltration of tumor-associated myeloid cells (TAMCs), reaching 30-50% of the tumor mass, is a distinctive characteristic of glioblastoma (GBM). These cells are a critical player in generating highly immunosuppressive microenvironment in GBM. Thus, therapeutic targeting of TAMCs might dampen the immunosuppression and improve the outcome of antiglioma therapies. In this work, we developed a novel nano-immunotherapy platform to actively and specifically target glioma-infiltrating TAMCs in vivo. Based on our finding that glioma-infiltrating TAMCs exhibit the highest expression of PD-L1 among all the immune cell infiltrates, we designed a lipid nanoparticle system (LNP) with surface-engineered anti-PD-L1 therapeutic antibody. Decoration of anti-PD-L1 antibody rendered our LNP highly capable of specifically targeting TAMCs and, interestingly, routing PD-L1 to lysosomal degradation. Co-encapsulation of dinaciclib, a cyclin-dependent kinase inhibitor, into LNP caused a dramatic elimination of TAMCs and inhibition of immunosuppression in glioma. Notably, the targeting efficiency of TAMC-targeted LNP was further increased when combined with radiation therapy (RT), a standard care of GBM. The superior therapeutic efficacy in mice treated by RT+LNP combination over the RT or LNP monotherapy was demonstrated in two syngeneic murine glioma models, GL261 and CT2A. We also demonstrated that our LNP successfully targeted TAMCs harvested from human resection specimens, which further validated the translational potential and clinical relevance of our nano-immunotherapy approach. In conclusion, our work established a new nanotechnology-based immunotherapeutic approach with great potential to improve the clinical outcome in patients with GBM.

Citation Format: Peng Zhang, Jason Miska, Catalina Lee-Chang, Aida Rashidi, Wojciech K. Panek, Shejuan An, Markella Zannikou, Aurora Lopez-Rosas, Yu Han, Ting Xiao, Irina V. Balyasnikova, Maciej S. Lesniak. PD-L1-mediated nanotherapeutic targeting of glioma-infiltrating myeloid cells synergizes with radiotherapy for glioblastoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B95.

A Neutrophil-Inspired Supramolecular Nanogel for Magnetocaloric-Enzymatic Tandem Therapy

Neutrophils can responsively release reactive oxygen species (ROS) to actively combat infections by exogenous stimulus and cascade enzyme catalyzed bio-oxidation. A supramolecular nanogel is now used as an artificial neutrophil by enzymatic interfacial self-assembly of peptides (Fmoc-Tyr(H₂ PO₃ )-OH) with magnetic nanoparticles (MNPs) and electrostatic loading of chloroperoxidase (CPO). The MNPs within the nanogel can elevate H₂ O₂ levels in cancer cells under programmed alternating magnetic field (AMF) similar to the neutrophil activator, and the loaded CPO within protective peptides nanolayer converts the H₂ O₂ into singlet oxygen (¹ O₂ ) in a sustained manner for neutrophil-inspired tumor therapy. As a proof of concept study, both the H₂ O₂ and ¹ O₂ in cancer cells increase stepwise under a programmed alternating magnetic field. An active enzyme dynamic therapy by magnetically stimulated oxygen stress and sustained enzyme bio-oxidation is thus shown with studies on both cells and animals.

Remote Control of Mechanical Forces via Mitochondrial-Targeted Magnetic Nanospinners for Efficient Cancer Treatment

In cells, mechanical forces play a key role in impacting cell behaviors, including adhesion, differentiation, migration, and death. Herein, a 20 nm mitochondria-targeted zinc-doped iron oxide nanocube is designed as a nanospinner to exert mechanical forces under a rotating magnetic field (RMF) at 15 Hz and 40 mT to fight against cancer. The nanospinners can efficiently target the mitochondria of cancer cells. By means of the RMF, the nanocubes assemble in alignment with the external field and produce a localized mechanical force to impair the cancer cells. Both in vitro and in vivo studies show that the nanospinners can damage the cancer cells and reduce the brain tumor growth rate after the application of the RMF. This nanoplatform provides an effective magnetomechanical approach to treat deep-seated tumors in a spatiotemporal fashion.

GCN2 is essential for CD8+ T cell survival and function in murine models of malignant glioma

Amino acid deprivation is a strategy that malignancies utilize to blunt anti-tumor T-cell immune responses. It has been proposed that amino acid insufficiency in T-cells is detected by GCN2 kinase, which through phosphorylation of EIF2α, shuts down global protein synthesis leading to T-cell arrest. The role of this amino acid stress sensor in the context of malignant brain tumors has not yet been studied, and may elucidate important insights into the mechanisms of T-cell survival in this harsh environment. Using animal models of glioblastoma and animals with deficiency in GCN2, we explored the importance of this pathway in T-cell function within brain tumors. Our results show that GCN2 deficiency limited CD8+ T-cell activation and expression of cytotoxic markers in two separate murine models of glioblastoma in vivo. Importantly, adoptive transfer of antigen-specific T-cells from GCN2 KO mice did not control tumor burden as well as wild-type CD8+ T-cells. Our in vitro and in vivo data demonstrated that reduction in amino acid availability caused GCN2 deficient CD8+ T-cells to become rapidly necrotic. Mechanistically, reduced CD8+ T-cell activation and necrosis was due to a disruption in TCR signaling, as we observed reductions in PKCθ and phoshpo-PKCθ on CD8+ T-cells from GCN2 KO mice in the absence of tryptophan. Validating these observations, treatment of wild-type CD8+ T-cells with a downstream inhibitor of GCN2 activation also triggered necrosis of CD8+ T-cells in the absence of tryptophan. In conclusion, our data demonstrate the vital importance of intact GCN2 signaling on CD8+ T-cell function and survival in glioblastoma.

ACTR-57. A PHASE 1/2 STUDY TO EVALUATE THE SAFETY AND EFFICACY OF BLOOD-BRAIN BARRIER (BBB) OPENING WITH A NINE-EMITTER IMPLANTABLE ULTRASOUND DEVICE IN RECURRENT GLIOBLASTOMA PATIENTS PRIOR TO CARBOPLATIN

The blood-brain barrier (BBB) limits penetration of systemically administered therapies to brain tumors and peritumoral tissue and may be responsible for the failure of numerous drugs in recent clinical trials for glioblastoma (GBM). Low intensity pulsed ultrasound (LIPU), with concomitant intravenous microbubble injection (DEFINITY®), can temporarily disrupt the BBB for 6–24 hours and allow for enhanced delivery of drugs to the brain. In previous clinical studies, a 1-cm ultrasound (US) device, SonoCloud-1, was implanted in a burr hole of recurrent GBM patients (n=27) and used to disrupt the BBB prior to carboplatin infusion at AUC5. This ongoing pilot phase 1/2 study (NCT03744026) aims to evaluate the safety and efficacy of transient opening of the BBB by LIPU in rGBM with the SonoCloud-9, a larger nine-emitter implantable device, designed to cover the tumor and surrounding infiltrative regions. The ultrasound device is implanted in a 6 cm x 6 cm bone flap window after tumor debulking surgery. Patients receive a 270-second sonication every month with concomitant microbubble injection to disrupt the BBB followed by carboplatin infusion at AUC4-6. Magnetic resonance imaging (MRI) is performed to verify safety and extent of BBB disruption. This study began enrollment in early 2019 and is an international, open-label, single arm, multi-site, dose-escalation and expansion trial to evaluate the safety of escalating sonication volume (“dose”) with concurrent carboplatin. The number of activated emitters in the implant (3, 6, 9) is increased using a 3 + 3 dose escalation design. Safety data of the escalation phase of the study will be presented.

EXTH-68. INTRANASAL DELIVERY OF DRUG-LOADED LIPOSOMES SENSITIZES TUMORS TO IRRADIATION IN SYNGENEIC MODEL OF GLIOMA

Tumor-associated myeloid cells (TAMCs) are appealing therapeutic target in glioblastoma (GBM) due to their immunosuppressive function and robust presence in the tumor tissue. We designed a lipid nanoparticle (LNP) modified with anti-PD-L1 antibody (αPD-L1) for targeted delivery to PD-L1 expressing cells within the tumor. We demonstrate that αPD-L1-LNP are effectively and specifically taken up by TAMCs. The encapsulation of dinaciclib, an inhibitor of a cyclin-dependent kinase, into αPD-L1-LNP, leads to a robust depletion of TAMCs upon local delivery. We next investigated the therapeutic relevance of non-invasive intranasal delivery of αPD-L1-LNP drug nano formulation in a GL261 syngeneic model of glioma. We show that intranasal administration of αPD-L1-LNP/dinaciclib alone did not significantly affect the survival of tumor-bearing mice, whereas a regimen combing with fractionated irradiation led to a significantly improved animal survival of mice bearing GL261 glioma over monotherapies. Histological analysis of tissue demonstrated about a four-fold increase in the uptake of nanoparticles within the tumor bed but not in the normal brain in mice treated with fractionated irradiation over the control mice. These results warrant further development and validation of intranasal delivery of therapeutic nanoformulations targeting TAMCs in preclinical animal models to improve the outcome in GBM patients.

CMET-11. RESPONSE TO STEREOTACTIC RADIOSURGERY FOR MULTIPLE BRAIN METASTASES BASED ON HISTOLOGY-SPECIFIC SUBTYPE STATUS

BACKGROUND

This retrospective study evaluated the relationship between histologic subtype and treatment outcomes following SRS for the treatment of multiple brain metastases (MBM).

METHODS

We analyzed patients with MBM, defined here as >= 3 lesions, treated with SRS at our institution. Primary histologies examined were NSCLC, breast, and melanoma. Patients were categorized according to histology-specific subtypes (NSCLC-EGFR, ALK, KRAS, PD-L1%; breast-HER2, ER, PR; melanoma-BRAF). The primary outcome was local control (defined by RANO-BM) and secondary outcomes included intracranial progression-free survival (iPFS) and overall survival (OS).

RESULTS

141 patients met inclusion criteria (66 NSCLC, 61 breast, and 14 melanoma). HER2+ and BRAF V600E+ lesions had increased rates of local control following SRS (P=0.0048 and P=0.0256, respectively) compared to other breast/melanoma subtypes. EGFR mutation was not associated with increased local control with SRS (71 vs 74%), but increased iPFS (P=0.0031). On multivariable analysis, EGFR+ was independently associated with a decreased time-dependent risk of death (P=0.011). The use of progressively newer generations of EGFR-directed therapies was associated with stepwise decreasing risk of intracranial progression and death. HER2+ disease had improved iPFS and OS (P=0.0058 and P< 0.0001, respectively; it was not an independent risk factor for progression or death; however, the use of HER2-directed antibodies was associated with decreased risk of death (p=0.036). The use of tyrosine kinase inhibitors (i.e. lapatanib) was not associated with improvements, although this was a small subset.

CONCLUSIONS

Some histologic subtypes appear to have better control with SRS, with HER2+ breast cancer and BRAF V600E+ melanoma associated with improved outcomes – this requires further validation; a volumetric analysis is pending. This the protective effect of EGFR mutation appears to be partly related to use of EGFR inhibitors, with the use of newer-generation therapies leading to improved outcomes; although local control with SRS remains excellent regardless of the mutation.

IMMU-42. CD8+ T-CELLS MEDIATE IMMUNOEDITING, AND INFLUENCE GENOTYPE, TUMOR ONCOGENIC PATHWAYS AND MICROENVIRONMENT DURING PROGRESSION OF MURINE GLIOMAS

Cancer immunoediting shapes tumor progression by the immunological selection of tumor cell variants that can evade immune recognition. Given the immune evasive cellular diversity of glioblastoma, we hypothesized that CD8+ T-cells mediate immunoediting in this tumor. We evaluated tumor progression in the absence of CD8+ T-cells by depleting this immune cell population in a transgenic murine glioma model. Tumors generated in the absence of CD8+ T-cells developed poorly in recipients with intact immunity, implying a more immunogenic profile. These tumors demonstrated increased chromosomal instability, gene fusions, MAPK signaling, and macrophage infiltration. These observations were stochastic, suggesting variability in the mode of tumor evolution in the absence of this immune effector. MAPK activation was correlated with macrophage recruitment in two transgenic murine models and the human disease. Our results indicate that CD8+ T-cells mediate a strong immunoediting selection in glioblastoma that protect against the hallmarks of cancer and drive immune evasion.

RDNA-05. RADIOTHERAPY PROMOTES ONCOPROGRESSIVE CROSSTALK BETWEEN GLIOBLASTOMA TUMOR CELLS AND M2 MACROPHAGES VIA THE NLRP3 INFLAMMASOME PATHWAY

PURPOSE

Radiotherapy (RT) is an essential component in the adjuvant treatment of glioblastoma (GBM); however, despite an initial benefit in tumor control, recurrence is nearly universal. The inflammasome is a multimeric cytosolic complex that has been shown to be activated in immune cells following RT. We investigated the relationship of inflammasome activation and disease progression after RT in GBM.

METHODS

We performed survival analysis for patients with recurrent GBM using the TCGA dataset, stratifying according to expression of inflammasome pathway molecules Caspase 1 (CASP1), IL-1β, and NLRP3. IL-1β expression and colocalization with CD11b+ myeloid cells were analyzed at different time points following RT in a murine glioma GL261 model. We detected the secreted IL-1β, CASP1 activity, and NLRP3 expression in both tumor and infiltrating immune cells, and the downstream effects of their interplay, including cellular apoptosis, proliferation, and viability.

RESULTS

High expression of CASP1, IL-1β, and NLRP3 are associated with poor survival in recurrent GBM. In a mouse model, recurrent tumors after treatment with RT display higher levels of the inflammasome effector molecule IL-1β, which colocalizes with infiltrating CD11b+ myeloid cells. Using a co-culture system of tumor cell and M2 macrophages, we found that RT enhances inflammasome activation in both cell types, and this interaction restores the proliferative capacity of surviving tumor cells following treatment. RT induces the inflammasome pathway activation in the setting of an associated immune microenvironment rich in tumor-associated macrophages and myeloid-derived suppressor cells (TAM/MDSCs) and not in tumor cells alone.

CONCLUSIONS

Inhibition of the oncoprogressive crosstalk between GBM tumor cells and M2 macrophages, possibly through disruption of the inflammasome pathway, might be a potential therapeutic strategy with RT.

IMMU-43. POLYAMINE METABOLISM REGULATES MYELOID IMMUNE SUPPRESSION IN GLIOBLASTOMA

Tumor-associated myeloid cells, which consist of tumor associated macrophages and myeloid-derived suppressor cells (MDSCs), make up a majority of cellular infiltrates in glioma. Glioma infiltrating MDSCs highly express arginase-1 (Arg-1), a catabolic enzyme thought to deplete arginine from the tumor microenvironment. Despite being a well-known marker of immunosuppressive cells, the metabolic reasons for this choice are not clear. Examination of MDSC phenotype in murine glioma models using: RNA-seq, bulk metabolomics, and Carbon-13 arginine flux revealed that two separate pathways of arginine catabolism converge on the generation of ornithine. Ornithine is the prerequisite substrate for the de-novo generation of polyamines, a group of nitrogen-rich metabolites with foundational importance to all mammalian, bacterial, and plant biology. Importantly, we found that the rate-limiting step of polyamine generation, ornithine decarboxylase 1 (ODC1), is dramatically upregulated by glioma infiltrating MDSCs, suggesting de-novo polyamine generation is important for MDSC function. Treatment with a specific inhibitor of de-novo polyamine synthesis, difluoromethylornithine (DMFO), inhibited the immunosuppressive function of in-vitro generated glioma associated MDSCs. However, DFMO only exerted effects before differentiation, as DFMO treatment post-generation did not change their suppressive functions. This suggests that the generation of the polyamine pool is critical to immune suppression by MDSCs. Interestingly the expression of the rate limiting step of polyamine degradation (SAT1) is inversely correlated with (ODC1) during MDSC differentiation, suggesting that utilization of this polyamine pool may be required for the suppressive functions of these cells. Inhibition of SAT1 after MDSC generation blunted MDSC mediated T-cell suppression. The results of this study show that the role of arginine metabolism in tumor infiltrating MDSCs is to generate pools of polyamines which maintain MDSC function in glioma. Therapeutic targeting of this pathway may be a novel and powerful tool to combat immunosuppression in glioma.

TMZ regulates GBM stemness via MMP14-DLL4-Notch3 pathway

Glioblastoma (GBM) is one of the most aggressive primary brain tumors with frequent recurrences following the standard methods of treatment-temozolomide (TMZ), ionizing radiation and surgical resection. The objective of our study was to investigate GBM resistance mediated via MMP14 (matrix metalloproteinase 14). We used multiple PDX GBM models and established glioma cell lines to characterize expression and subcellular localization of MMP14 after TMZ treatment. We performed a Kiloplex ELISA-based array to evaluate changes in cellular proteins induced by MMP14 expression and translocation. Lastly, we conducted functional and mechanistic studies to elucidate the role of DLL4 (delta-like canonical notch ligand 4) in regulation of glioma stemness, particularly in the context of its relationship to MMP14. We detected that TMZ treatment promotes nuclear translocation of MMP14 followed by extracellular release of DLL4. DLL4 in turn stimulates cleavage of Notch3, its nuclear translocation and induction of sphering capacity and stemness.

Myeloid-Derived Suppressive Cells Promote B cell-Mediated Immunosuppression via Transfer of PD-L1 in Glioblastoma

The potent immunosuppression induced by glioblastoma (GBM) is one of the primary obstacles to finding effective immunotherapies. One hallmark of the GBM-associated immunosuppressive landscape is the massive infiltration of myeloid-derived suppressor cells (MDSC) and, to a lesser extent, regulatory T cells (Treg) within the tumor microenvironment. Here, we showed that regulatory B cells (Breg) are a prominent feature of the GBM microenvironment in both preclinical models and clinical samples. Forty percent of GBM patients (n = 60) scored positive for B-cell tumor infiltration. Human and mouse GBM-associated Bregs were characterized by immunosuppressive activity toward activated CD8⁺ T cells, the overexpression of inhibitory molecules PD-L1 and CD155, and production of immunosuppressive cytokines TGFβ and IL10. Local delivery of B cell-depleting anti-CD20 immunotherapy improved overall survival of animals (IgG vs. anti-CD20 mean survival: 18.5 vs. 33 days, P = 0.0001), suggesting a potential role of Bregs in GBM progression. We unveiled that GBM-associated MDSCs promoted regulatory B-cell function by delivering microvesicles transporting membrane-bound PD-L1, able to be up-taken by tumoral B cells. The transfer of functional PD-L1 via microvesicles conferred Bregs the potential to suppress CD8⁺ T-cell activation and acquisition of an effector phenotype. This work uncovered the role of B cells in GBM physiopathology and provides a mechanism by which the GBM microenvironment controls B cell-mediated immunosuppression.See related Spotlight on p. 1902.

FABP7 is a key metabolic regulator in HER2+ breast cancer brain metastasis

Overexpression of human epidermal growth factor receptor 2 (HER2) in breast cancer patients is associated with increased incidence of breast cancer brain metastases (BCBM), but the mechanisms underlying this phenomenon remain unclear. Here, to identify brain-predominant genes critical for the establishment of BCBM, we conducted an in silico screening analysis and identified that increased levels of fatty acid-binding protein 7 (FABP7) correlate with a lower survival and higher incidence of brain metastases in breast cancer patients. We validated these findings using HER2+ BCBM cells compared with parental breast cancer cells. Importantly, through knockdown and overexpression assays, we characterized the role of FABP7 in the BCBM process in vitro and in vivo. Our results uncover a key role of FABP7 in metabolic reprogramming of HER2 + breast cancer cells, supporting a glycolytic phenotype and storage of lipid droplets that enable their adaptation and survival in the brain microenvironment. In addition, FABP7 is shown to be required for upregulation of key metastatic genes and pathways, such as integrins-Src and VEGFA, and for the growth of HER2+ breast cancer cells in the brain microenvironment in vivo. Together, our results support FABP7 as a potential target for the treatment of HER2+ BCBM.

Diagnostic Clinical Trials in Breast Cancer Brain Metastases: Barriers and Innovations

Optimal treatment of breast cancer brain metastases (BCBM) is often hampered by limitations in diagnostic abilities. Developing innovative tools for BCBM diagnosis is vital for early detection and effective treatment. In this study we explored the advances in trial for the diagnosis of BCBM, with review of the literature. On May 8, 2019, we searched ClinicalTrials.gov for interventional and diagnostic clinical trials involving BCBM, without limiting for date or location. Information on trial characteristics, experimental interventions, results, and publications were collected and analyzed. In addition, a systematic review of the literature was conducted to explore published studies related to BCBM diagnosis. Only 9 diagnostic trials explored BCBM. Of these, 1 trial was withdrawn because of low accrual numbers. Three trials were completed; however, none had published results. Modalities in trial for BCBM diagnosis entailed magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), PET-CT, nanobodies, and circulating tumor cells (CTCs), along with a collection of novel tracers and imaging biomarkers. MRI continues to be the diagnostic modality of choice, whereas CT is best suited for acute settings. Advances in PET and PET-CT allow the collection of metabolic and functional information related to BCBM. CTC characterization can help reflect on the molecular foundations of BCBM, whereas cell-free DNA offers new genetic material for further exploration in trials. The integration of machine learning in BCBM diagnosis seems inevitable as we continue to aim for rapid and accurate detection and better patient outcomes.

Pharmacologic modulation of nasal epithelium augments neural stem cell targeting of glioblastoma

Glioblastoma (GBM) remains the most lethal and untreatable central nervous system malignancy. The challenges to devise novel and effective anti-tumor therapies include difficulty in locating the precise tumor border for complete surgical resection, and rapid regrowth of residual tumor tissue after standard treatment. Repeatable and non-invasive intranasal application of neural stem cells (NSCs) was recently shown to enable clinically relevant delivery of therapy to tumors. Treatment with chemotactic NSCs demonstrated significant survival benefits when coupled with radiation and oncolytic virotherapy in preclinical models of GBM. In order to further augment the clinical applicability of this novel therapeutic platform, we postulate that the FDA-approved compound, methimazole (MT), can be safely utilized to delay the nasal clearance and improve the ability of NSCs to penetrate the olfactory epithelium for robust in vivo brain tumor targeting and therapeutic actions. METHODS: To examine the role of reversible reduction of the olfactory epithelial barrier in non-invasive intranasal delivery, we explored the unique pharmacologic effect of MT at a single dosage regimen. In our proof-of-concept studies, quantitative magnetic resonance imaging (MRI), immunocytochemistry, and survival analysis were performed on glioma-bearing mice treated with a single dose of MT prior to intranasal anti-GBM therapy using an oncolytic virus (OV)-loaded NSCs. RESULTS: Based on histology and in vivo imaging, we found that disrupting the olfactory epithelium with MT effectively delays clearance and allows NSCs to persist in the nasal cavity for at least 24 h. MT pretreatment amplified the migration of NSCs to the tumor. The therapeutic advantage of this enhancement was quantitatively validated by tissue analysis and MRI tracking of NSCs loaded with superparamagnetic iron oxide nanoparticles (SPIOs) in live animals. Moreover, we observed significant survival benefits in GBM-bearing mice treated with intranasal delivery of oncolytic virus-loaded NSCs following MT injection. Conclusion: Our work identified a novel pharmacologic strategy to accelerate the clinical application of the non-invasive NSCs-based therapeutic platform to tackle aggressive brain tumors.

Current state of clinical trials in breast cancer brain metastases

Background

Breast cancer brain metastases (BCBM) are the final frontier in neuro-oncology for which more efficacious therapies are required. In this work, we explore clinical trials in BCBM, and determine the shortcomings in the development of new BCBM therapies to shed light on potential areas for enhancement.

Methods

On July 9, 2018, we searched ClinicalTrials.gov for all interventional and therapeutic clinical trials involving BCBM, without limiting for date or location. Information on trial characteristics, including phase, status, start and end dates, study design, primary endpoints, selection criteria, sample size, experimental interventions, results, and publications were collected and analyzed.

Results

Fifty-three trials fulfilled the selection criteria. Median trial duration across phases ranged between 3 and 6 years. More than half of the trials were conducted in the United States. Although 94% of the trials were in early phases (I-II), 20% of patients were in phase III trials. Two phase III trials were anteceded by phase II trials that were non-randomized; one reported positive results. Approximately one-third of the trials were completed, whereas 23% of trials were terminated early; mostly due to inadequate enrollment. Only 13% of all trials and 22% of completed trials had published results directly linked to their primary outcomes.

Conclusions

The low number of trials and accrual numbers, the lack of diversity, and the scarcity of published results represent the main troubles in clinical BCBM research. Optimization of BCBM trials is necessary to achieve effective therapies.

Race influences survival in glioblastoma patients with KPS ≥ 80 and associates with genetic markers of retinoic acid metabolism

PURPOSE

To study whether the clinical outcome and molecular biology of gliomas in African-American patients fundamentally differ from those occurring in Whites.

METHODS

The clinical information and molecular profiles (including gene expression array, non-silent somatic mutation, DNA methylation and protein expression) were downloaded from The Cancer genome atlas (TCGA). Electronic medical records were abstracted from Northwestern Medicine Enterprise Data Warehouse (NMEDW) for analysis as well. Grade II-IV Glioma patients were all included.

RESULTS

931 Whites and 64 African-American glioma patients from TCGA were analyzed. African-American with Karnofsky performance score (KPS) ≥ 80 have significantly lower risk of death than similar white Grade IV Glioblastoma (GBM) patients [HR (95% CI) = 0.47 (0.23, 0.98), P = 0.0444, C-index = 0.68]. Therefore, we further compared gene expression profiles between African-American GBM patients and Whites with KPS ≥ 80. Extrapolation of genes significantly associated with increased African-American patient survival revealed a set of 13 genes with a possible role in this association, including elevated expression of genes previously identified as increased in African-American breast and colon cancer patients (e.g. CRYBB2). Furthermore, gene set enrichment analysis revealed retinoic acid (RA) metabolism as a pathway significantly upregulated in African-American GBM patients who survive longer than Whites (Z-score = - 2.10, Adjusted P-value = 0.0449).

CONCLUSIONS

African Americans have prolonged survival with glioma which is influenced only by initial KPS score. Genes previously associated with both racial disparities in cancer and pathways associated with RA metabolism may play an important role in glioma etiology. In the future exploration of these genes and pathways may inform novel therapies for this incurable disease.

Imaging tryptophan uptake with positron emission tomography in glioblastoma patients treated with indoximod

INTRODUCTION

Glioblastoma (GBM) is the most frequent and aggressive primary tumor of the central nervous system, accounting for over 50% of all primary malignant gliomas arising in the adult brain. Even after surgical resection, adjuvant radiotherapy (RT) and temozolomide (TMZ) chemotherapy, as well as tumor-treating fields, the median survival is only 15-20 months. We have identified a pathogenic mechanism that contributes to the tumor-induced immunosuppression in the form of increased indoleamine 2,3 dioxygenase 1 (IDO1) expression; an enzyme that metabolizes the essential amino acid, tryptophan (Trp), into kynurenine (Kyn). However, real-time measurements of IDO1 activity has yet to become mainstream in clinical protocols for assessing IDO1 activity in GBM patients.

METHODS

Pre-treatment and on-treatment α-[11C]-methyl-L-Trp (AMT) positron emission tomography (PET) with co-registered MRI was performed on patients with recurrent GBM treated with the IDO1 pathway inhibitor indoximod (D1-MT) and TMZ.

RESULTS

Regional intratumoral variability of AMT within enhancing and non-enhancing tumor was noted at baseline. On treatment imaging revealed decreased regional uptake suggesting IDO1 pathway modulation with treatment.

CONCLUSIONS

Here, we have validated the ability to use PET of the Trp probe, AMT, for use in visualizing and quantifying intratumoral Trp uptake in GBM patients treated with an IDO1 pathway inhibitor. These data serve as rationale to utilize AMT-PET imaging in the future evaluation of GBM patients treated with IDO1 enzyme inhibitors.

Enhanced Delivery of Oncolytic Adenovirus by Neural Stem Cells for Treatment of Metastatic Ovarian Cancer

Oncolytic virotherapy is a promising approach for treating recurrent and/or drug-resistant ovarian cancer. However, its successful application in the clinic has been hampered by rapid immune-mediated clearance or neutralization of the virus, which reduces viral access to tumor foci. To overcome this barrier, patient-derived mesenchymal stem cells have been used to deliver virus to tumors, but variability associated with autologous cell isolations prevents this approach from being broadly clinically applicable. Here, we demonstrate the ability of an allogeneic, clonal neural stem cell (NSC) line (HB1.F3.CD21) to protect oncolytic viral cargo from neutralizing antibodies within patient ascites fluid and to deliver it to tumors within preclinical peritoneal ovarian metastases models. The viral payload used is a conditionally replication-competent adenovirus driven by the survivin promoter (CRAd-S-pk7). Because the protein survivin is highly expressed in ovarian cancer, but not in normal differentiated cells, viral replication should occur selectively in ovarian tumor cells. We found this viral agent was effective against cisplatin-resistant ovarian tumors and could be used as an adjunct treatment with cisplatin to decrease tumor burden without increasing toxicity. Collectively, our data suggest NSC-delivered CRAd-S-pk7 virotherapy holds promise for improving clinical outcome, reducing toxicities, and improving quality of life for patients with advanced ovarian cancer.

Local Application of Autologous Platelet-Rich Fibrin Patch (PRF-P) Suppresses Regulatory T Cell Recruitment in a Murine Glioma Model

The immunosuppressive microenvironment is one of the major factors promoting the growth of glioblastoma multiforme (GBM). Infiltration of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) into the tumor microenvironment plays a significant role in the suppression of the anti-tumor immunity and portends a dismal prognosis for patients. Glioma-mediated secretion of chemo-attractant C-C motif ligand 2 and 22 (CCL2/22) has previously been shown by our group to promote Treg migration in vitro. In this study, we show that a local implantation of platelet-rich fibrin patch (PRF-P) into the brain of GL261 glioma-bearing mice prolonged the survival of affected animals by 42.85% (p = 0.0011). Analysis performed on brain tumor tissue harvested from PRF-P-treated mice revealed a specific decrease in intra-tumoral lymphocytes with a preferential depletion of immunosuppressive Tregs. Importantly, co-culture of GL261 or chemo-attractants (CCL2/22) with PRF-P abrogated Treg migration. Pharmacological blockade of the CCL2/22 interaction with their receptors potentiated the inhibitory effect of PRF-P on Tregs recruitment in culture. Moreover, our findings revealed the soluble CD40 ligand (sCD40L) as a major Treg inhibitory player produced by activated platelets entrapped within the fibrin matrix of the PRF-P. Blockade of sCD40L restored the migratory capacity of Tregs, emphasizing the role of PRF-P in preventing the Treg migration to glioma tissue. Our findings highlight autologous PRF-P as a personalized, Treg-selective suppression platform that can potentially supplement and enhance the efficacy of glioma therapies.

A Dendritic Cell-Targeted Adenoviral Vector Facilitates Adaptive Immune Response Against Human Glioma Antigen (CMV-IE) and Prolongs Survival in a Human Glioma Tumor Model

Antitumor immunotherapeutic strategies represent an especially promising set of approaches with rapid translational potential considering the dismal clinical context of high-grade gliomas. Dendritic cells (DCs) are the body's most professional antigen-presenting cells, able to recruit and activate T cells to stimulate an adaptive immune response. In this regard, specific loading of tumor-specific antigen onto dendritic cells potentially represents one of the most advanced strategies to achieve effective antitumor immunization. In this study, we developed a DC-specific adenoviral (Ad) vector, named Ad5scFvDEC205FF, targeting the DC surface receptor, DEC205. In vitro analysis shows that 60% of DCs was infected by this vector while the infectivity of other control adenoviral vectors was less than 10%, demonstrating superior infectivity on DCs. Moreover, an average of 14% of DCs were infected by Ad5scFvDEC205FF-GFP, while less than 3% of non-DCs were infected following in vivo administration, demonstrating highly selective in vivo DC infection. Importantly, vaccination with this vehicle expressing human glioma-specific antigen, Ad5scFvDEC205FF-CMV-IE, shows a prolonged survival benefit in GL261CMV-IE-implanted murine glioma models (p < 0.0007). Furthermore, when rechallenged, cancerous cells were completely rejected. In conclusion, our novel, viral-mediated, DC-based immunization approach has the significant therapeutic potential for patients with high-grade gliomas.