Search

Brain tumors remain especially challenging to treat due to the presence of the blood–brain barrier. The unique biophysical properties of nanomaterials enable access to the tumor environment with minimally invasive injection methods such as intranasal and systemic delivery. In this review, we will discuss approaches taken in NP delivery to brain tumors in preclinical neuro-oncology studies and ongoing clinical studies. Despite recent development of many promising nanoparticle systems to modulate immunologic function in the preclinical realm, clinical work with nanoparticles in malignant brain tumors has largely focused on imaging, chemotherapy, thermotherapy and radiation. Review of early preclinical studies and clinical trials provides foundational safety, feasibility and toxicology data that can usher a new wave of nanotherapeutics in application of immunotherapy and translational oncology for patients with brain tumors.

Changes in the transcription factor (TF) expression are critical for brain development, and they may also underlie neurodevelopmental disorders. Indeed, T-box brain1 (Tbr1) is a TF crucial for the formation of neocortical layer VI, and mutations and microdeletions in that gene are associated with malformations in the human cerebral cortex, alterations that accompany autism spectrum disorder (ASD). Interestingly, Tbr1 upregulation has also been related to the occurrence of ASD-like symptoms, although limited studies have addressed the effect of increased Tbr1 levels during neocortical development. Here, we analysed the impact of Tbr1 misexpression in mouse neural progenitor cells (NPCs) at embryonic day 14.5 (E14.5), when they mainly generate neuronal layers II–IV. By E18.5, cells accumulated in the intermediate zone and in the deep cortical layers, whereas they became less abundant in the upper cortical layers. In accordance with this, the proportion of Sox5+ cells in layers V–VI increased, while that of Cux1+ cells in layers II–IV decreased. On postnatal day 7, fewer defects in migration were evident, although a higher proportion of Sox5+ cells were seen in the upper and deep layers. The abnormal neuronal migration could be partially due to the altered multipolar-bipolar neuron morphologies induced by Tbr1 misexpression, which also reduced dendrite growth and branching, and disrupted the corpus callosum. Our results indicate that Tbr1 misexpression in cortical NPCs delays or disrupts neuronal migration, neuronal specification, dendrite development and the formation of the callosal tract. Hence, genetic changes that provoke ectopic Tbr1 upregulation during development could provoke cortical brain malformations.

While promising, immunotherapy has yet to be fully unlocked for the preponderance of cancers where conventional chemoradiation reigns. This remains particularly evident in pediatric sarcomas where standard of care has not appreciably changed in decades. Importantly, pediatric bone sarcomas, like osteosarcoma and Ewing’s sarcoma, possess unique tumor microenvironments driven by distinct molecular features, as do rhabdomyosarcomas and soft tissue sarcomas. A better understanding of each malignancy’s biology, heterogeneity, and tumor microenvironment may lend new insights toward immunotherapeutic targets in novel platform technologies for cancer vaccines and adoptive cellular therapy. These advances may pave the way toward new treatments requisite for pediatric sarcomas and patients in need of new therapies.

Background: Since the preponderance of pediatric gliomas are mutationally 'bland,' immune checkpoint inhibitors are unlikely to mediate therapeutic benefit. Alternately, immunologic response can be induced de novo against pediatric gliomas with mRNA cancer vaccines. Messenger RNA represents a paradigm shift in vaccinology (i.e. COVID-19) given its flexibility, commercialization, and propensity to confer rapid protection with only a single vaccine. Objective: We sought to develop a new mRNA platform with an optimized backbone for insertion of both personalized and/or “off the shelf” (i.e. H3K27M) transcripts for rapid induction of anti-tumor activity against pediatric gliomas. Approach: We synthesized an mRNA backbone with optimized 5' and 3' UTRs for delivery of gene transcripts pertinent to pediatric brain tumors using a lipid-nanoparticle (NP) delivery vehicle. This vaccine utilizes a novel engineering design that layers tumor derived mRNA into a lipid-nanoparticle (NP) “onion-like” or multi-lamellar package. Results: We demonstrate immunogenicity of RNA-NPs delivering either personalized glioma mRNA or H3K27M mRNA. RNA-NPs localize to myeloid cells in murine KR158b brain tumors and activate dendritic cells that supplant regulatory intratumoral myeloid populations inducing antigenrecall response with long-term survivor benefit. Our optimized mRNA backbone yielded significantly improved anti-tumor efficacy compared with commercial backbones. We have shown this approach can be refined for co-delivery of immunomodulatory RNAs (i.e. GM-CSF) and/or delivery of siRNAs targeting immunoregulatory axes (PD-L1) in murine brain tumors (GL261). We have since established safety of RNA-NPs in acute/chronic murine GLP toxicity studies without cross-reactivity to normal-brain, and launched a large-animal canine brain tumor trial which demonstrated RNANPs to be feasible, safe and immunologically active. Conclusion: RNA-NPs reprogram the brain tumor microenvironment while inducing a gliomaspecific immune response. We have since received FDA-IND approval for first-in-human trials.

Purpose/Objective(s) Glioblastoma (GBM) is difficult to treat due to isolation behind the blood brain barrier and a notoriously immune-suppressive tumor microenvironment. RNA vaccines have recently shown great promise as activators of immune responses against viral pathogens but their efficacy in cancer is not well understood. Here, we describe a versatile, personalized mRNA-nanoparticle (RNA-NP) platform that can be customized to produce powerful anti-tumor immune activation, reprogram the brain tumor microenvironment, and enable tracking of particle localization to predict vaccine efficacy just two days after treatment. Materials/Methods Lipid mixtures (i.e., DOTAP, cholesterol) were complexed with mRNA encoding tumor antigens and evaluated for their ability to activate anti-tumor immune responses in vitro and in vivo. Particle localization after intravenous injection was assessed to identify constructs that enabled delivery of nucleic acids to intracranial tumors. Iron oxide nanoparticles (IONPs) were then incorporated into the cores of liposomes to enable particle tracking with MRI. Results Intravenous administration of RNA-NPs composed of DOTAP and RNA induced robust activation of innate immune cells resulting in prolonged survival in murine models of subcutaneous and intracranial melanoma. Inclusion of cholesterol in the lipid backbone enabled delivery of nucleic acids across the blood brain barrier and into tumor-associated myeloid cells in intracranial GL261 and KR158b tumors. These cholesterol-bearing liposomes not only activated innate immune cells in the tumor microenvironment (i.e., increased expression of CD80 and MHCII), but also enabled further manipulation of this compartment. Use of RNA-NPs to deliver siRNA targeting PD-L1 resulted in significant reduction in PD-L1 expression among tumor associated myeloid cells, leading to 37% long term survivorship in combination with systemic checkpoint blockade in an otherwise fatal model of GL261. IONPs were also incorporated into the cores of these particles to enable non-invasive tracking of particle localization with MRI. Preliminary experiments utilizing dendritic cells treated with iron-oxide-loaded RNA-NPs ex vivo demonstrate that a single dose of this therapy produces immunologic rejection of a murine melanoma model in which a dendritic cell vaccine currently in clinical trials yields no benefit. Furthermore, quantification of particle accumulation in lymph nodes with MRI correlates strongly with survival outcome (R =, indicating that tracking particle localization may be used to reliably differentiate responders from non-responders just two days after treatment. Conclusion RNA-NPs are a versatile platform for RNA delivery to immune cells. These particles are currently under investigation in canine trials with human clinical trials of our first-generation therapy beginning this year.

INTRODUCTION Glioblastoma (GBM) contains cell populations with distinct metabolic requirements, with fast-cycling cells harnessing aerobic glycolysis, and treatment-resistant slow-cycling cells (SCCs) preferentially engaging lipid metabolism. How the different tumor cells interact with immune cells and how this metabolic heterogeneity shapes the immune landscape in GBM has yet to be understood. OBJECTIVES The objectives are to unravel the various molecular signals and metabolic link that underlie the interaction of SCCs with the GBM microenvironment, in particular with the suppressive immune compartment, and to effectively target these interactions for better therapeutics. METHODS Multiple murine glioma cell lines were used to establish metabolic heterogeneity and communications, while various genetic and pharmacological approaches were applied to assess the effect of disrupting the metabolic interplay between SCCs and the immune system. RESULTS We determined that SCCs exhibit distinct metabolic dependencies, involving preferential lipid metabolism supported by enhanced fatty acid uptake. We also found that tumor progression is regulated by the interaction of SCCs with the immune system and established that SCCs recruit immune suppressive M2-like macrophages to the tumor microenvironment, which in turn work against tumor immune rejection by inhibiting T cell anti-tumor activity. The immune microenvironment shaped by SCCs is marked by specific metabolic features enhancing lipid exchange capacities that are exploited by SCCs to support their survival and functions. Importantly, disrupting lipid metabolic exchange sensitized tumors to chemotherapy. CONCLUSION Our results reveal that metabolic interactions between SCCs and tumor-associated macrophages within the GBM microenvironment play a critical role in the development of drug and immune resistant tumors. This study delineates these metabolic communications and assesses the potential therapeutic effect of disrupting these interactions to treat GBM. The insights generated from this project uncover fundamental principles of the emerging connections between the tumor microenvironment, cell metabolism, anti-tumor immunity, and associated therapeutic vulnerabilities.

BACKGROUND Brain tumors are notoriously difficult to treat in part due to their isolation behind the blood brain barrier and their power to suppress antitumor immune responses. We have previously reported cationic liposome formulations capable of delivering immune modulatory nucleic acids to immune cells in various peripheral organs, but there is currently no reliable method to deliver nucleic acids into brain tumors without direct injection into the tumor site. OBJECTIVE Here, we report the development of a customized lipid nanoparticle to deliver immune modulatory nucleic acids to immune cells in brain tumors. APPROACH Cationic liposomes composed of varying lipid combinations were evaluated for their ability to deliver functional mRNA and siRNA to innate immune cells in vitro and in intracranial tumor models. Nucleic acids were labelled with Cy3 to monitor particle distribution in vivo. RESULTS Lipids composed of DOTAP and cholesterol selectively delivered mRNA and siRNA to intracranial GL261 and KR158b tumors. Interestingly, these particles selectively delivered these nucleic acids to CD45+ white blood cells with minimal delivery to CD45- tumor cells or normal brain tissue. Encapsulation of siRNA blocking programmed death ligand 1 (PDL1) significantly reduced PDL1 expression on innate immune cells in brain tumors, with the greatest effects on tumor-associated macrophages. Co-administration of systemic checkpoint blockade with intravenous administration of these lipid nanoparticles bearing PDL1 siRNA enabled systemic and intratumoral checkpoint blockade, leading to 37% long term survivorship in an otherwise fatal intracranial tumor model. CONCLUSIONS Our customized lipid nanoparticles enable potent intratumoral immune modulation via delivery of nucleic acids to immune cells in brain tumors.

Translation of nanoparticles (NPs) into human clinical trials for patients with refractory cancers has lagged due to unknown biologic reactivities of novel NP designs. To overcome these limitations, simple well-characterized mRNA lipid-NPs have been developed as cancer immunotherapeutic vaccines. While the preponderance of RNA lipid-NPs encoding for tumor-associated antigens or neoepitopes have been designed to target lymphoid organs, they remain encumbered by the profound intratumoral and systemic immunosuppression that may stymie an activated T cell response. Herein, we show that systemic localization of untargeted tumor RNA (derived from whole transcriptome) encapsulated in lipid-NPs, with excess positive charge, primes the peripheral and intratumoral milieu for response to immunotherapy. In immunologically resistant tumor models, these RNA-NPs activate the preponderance of systemic and intratumoral myeloid cells (characterized by coexpression of PD-L1 and CD86). Addition of immune checkpoint inhibitors (ICIs) (to animals primed with RNA-NPs) augments peripheral/intratumoral PD-1(+)CD8(+) cells and mediates synergistic antitumor efficacy in settings where ICIs alone do not confer therapeutic benefit. These synergistic effects are mediated by type I interferon released from plasmacytoid dendritic cells (pDCs). In translational studies, personalized mRNA-NPs were safe and active in a client-owned canine with a spontaneous malignant glioma. In summary, we demonstrate widespread immune activation from tumor loaded RNA-NPs concomitant with inducible PD-L1 expression that can be therapeutically exploited. While immunotherapy remains effective for only a subset of cancer patients, combination therapy with systemic immunomodulating RNA-NPs may broaden its therapeutic potency.

Phospholipase D2 (PLD2), an enzyme involved in vesicle trafficking and membrane signaling, interacts with α-synuclein, a protein known to contribute in the development of Parkinson disease (PD). We previously reported that PLD2 overexpression in rat substantia nigra pars compacta (SNc) causes a rapid neurodegeneration of dopamine neurons, and that α-synuclein suppresses PLD2-induced nigral degeneration (Gorbatyuk et al., 2010). Here, we report that PLD2 toxicity is due to its lipase activity. Overexpression of a catalytically inactive mutant (K758R) of PLD2 prevents the loss of dopaminergic neurons in the SNc and does not show signs of toxicity after 10 weeks of overexpression. Further, mutant K758R does not affect dopamine levels in the striatum. In contrast, mutants that prevent PLD2 interaction with dynamin or growth factor receptor bound protein 2 (Grb2) but retained lipase activity, continued to show rapid neurodegeneration. These findings suggest that neither the interaction of PLD2 with dynamin, which has a role in vesicle trafficking, nor the PLD2 interaction with Grb2, which has multiple roles in cell cycle control, chemotaxis and activation of tyrosine kinase complexes, are the primary cause of neurodegeneration. Instead, the synthesis of phosphatidic acid (the product of PLD2), which is a second messenger in multiple cellular pathways, appears to be the key to PLD2 induced neurodegeneration. The fact that α-synuclein is a regulator of PLD2 activity suggests that regulation of PLD2 activity could be important in the progression of PD.

Background Since the preponderance of pediatric gliomas are mutationally ‘bland,’ immune checkpoint inhibitors are unlikely to mediate therapeutic benefit. Alternately, immunologic response can be induced de novo against pediatric gliomas with mRNA cancer vaccines. Messenger RNA represents a paradigm shift in vaccinology (i.e. COVID-19) given its flexibility, commercialization, and propensity to confer rapid protection with only a single vaccine. Objective We sought to develop a new mRNA platform with an optimized backbone for insertion of both personalized and/or “off the shelf’ (i.e. H3K27M) transcripts for rapid induction of anti-tumor activity against pediatric gliomas. Approach We synthesized an mRNA backbone with optimized 5’ and 3’ UTRs for delivery of gene transcripts pertinent to pediatric brain tumors using a lipid-nanoparticle (NP) delivery vehicle. This vaccine utilizes a novel engineering design that layers tumor derived mRNA into a lipid-nanoparticle (NP) “onion-like” or multi-lamellar package. Results We demonstrate immunogenicity of RNA-NPs delivering either personalized glioma mRNA or H3K27M mRNA. RNA-NPs localize to myeloid cells in murine KR158b brain tumors and activate dendritic cells that supplant regulatory intratumoral myeloid populations inducing antigen-recall response with long-term survivor benefit. Our optimized mRNA backbone yielded significantly improved anti-tumor efficacy compared with commercial backbones. We have shown this approach can be refined for co-delivery of immunomodulatory RNAs (i.e. GM-CSF) and/or delivery of siRNAs targeting immunoregulatory axes (PD-L1) in murine brain tumors (GL261). We have since established safety of RNA-NPs in acute/chronic murine GLP toxicity studies without cross-reactivity to normal-brain, and launched a large-animal canine brain tumor trial which demonstrated RNA-NPs to be feasible, safe and immunologically active. Conclusion RNA-NPs reprogram the brain tumor microenvironment while inducing a glioma-specific immune response. We have since received FDA-IND approval for first-in-human trials (IND#BB-19304) in pediatric patients with high-grade gliomas (PNOC020 study, NCT04573140).

The major drawback of the Baculovirus/Sf9 system for recombinant adeno-associated viral (rAAV) manufacturing is that most of the Bac-derived rAAV vector serotypes, with few exceptions, demonstrate altered capsid compositions and lower biological potencies. Here, we describe a new insect cell-based production platform utilizing attenuated Kozak sequence and a leaky ribosome scanning to achieve a serotype-specific modulation of AAV capsid proteins stoichiometry. By way of example, rAAV5 and rAAV9 were produced and comprehensively characterized side by side with HEK293-derived vectors. A mass spectrometry analysis documented a 3-fold increase in both viral protein (VP)1 and VP2 capsid protein content compared with human cell-derived vectors. Furthermore, we conducted an extensive analysis of encapsidated single-stranded viral DNA using next-generation sequencing and show a 6-fold reduction in collaterally packaged contaminating DNA for rAAV5 produced in insect cells. Consequently, the re-designed rAAVs demonstrated significantly higher biological potencies, even in a comparison with HEK293-manufactured rAAVs mediating, in the case of rAAV5, 4-fold higher transduction of brain tissues in mice. Thus, the described system yields rAAV vectors of superior infectivity and higher genetic identity providing a scalable platform for good manufacturing practice (GMP)-grade vector production.

Cancer vaccines initiate antitumor responses in a subset of patients, but the lack of clinically meaningful biomarkers to predict treatment response limits their development. Here, we design multifunctional RNA-loaded magnetic liposomes to initiate potent antitumor immunity and function as an early biomarker of treatment response. These particles activate dendritic cells (DCs) more effectively than electroporation, leading to superior inhibition of tumor growth in treatment models. Inclusion of iron oxide enhances DC transfection and enables tracking of DC migration with magnetic resonance imaging (MRI). We show that T2*-weighted MRI intensity in lymph nodes is a strong correlation of DC trafficking and is an early predictor of antitumor response. In preclinical tumor models, MRI-predicted "responders" identified 2 days after vaccination had significantly smaller tumors 2-5 weeks after treatment and lived 73% longer than MRI-predicted "nonresponders". These studies therefore provide a simple, scalable nanoparticle formulation to generate robust antitumor immune responses and predict individual treatment outcome with MRI.

BACKGROUND While dendritic cell (DC) vaccine therapy has shown considerable promise for glioblastoma (GBM) patients (Mitchell et al. Nature, 2015), their advancement into human clinical trials has been fraught with challenges in the development, manufacturing, and marketing of successful cancer immunotherapies. To circumvent the challenges associated with cell therapy, we have developed a new platform technology consisting of tumor derived mRNA complexed into lipid-nanoparticles (RNA-NPs) for systemic delivery to DCs in vivo and induction of antigen specific T cell immunity against GBM. OBJECTIVES/ METHODS We sought to assess if surface and charge modifications to our custom lipid-NP could facilitate its localization to lymphoid organs and the brain tumor microenvironment. RESULTS We demonstrate that intravenous administration of our unmodified custom RNA-NPs mediate systemic activation of DCs; these include activation of CD11c+ cells in the brains of animals with intact blood brain-barriers (BBBs). RNA-NPs mediate antigen specific T cell immunity and anti-tumor efficacy with increased tumor infiltrating lymphocytes against a NF-1/p53 mutant glioma that recapitulates features of human GBM in immunocompetent mice. Modification of surface charge could direct these RNA-NPs to lymphoid organs (e.g. spleen, lymph nodes) while modification of the lipid backbone (with cholesterol) enhances localization to innate immune cells in NF-1/p53 mutant and GL261 gliomas. We therefore assessed if this customizable lipid-NP could be leveraged for delivery of immune checkpoint inhibitors (ICIs) (i.e. PD-L1 siRNA) to the brain tumor microenvironment. Compared with scrambled siRNA-NPs in combination with ICIs, surface modified siRNA-NPs (antagonizing PD-L1) in combination with ICIs mediated significant antitumor efficacy with 37% long term survivors in an otherwise fatal brain tumor model. CONCLUSION We designed multifunctional RNA-NPs with a simple, scalable synthesis method that enables delivery of nucleic acids to innate immune cells in lymphoid organs and brain tumors.

BACKGROUND The lack of appropriate preclinical murine glioblastoma models limits comprehensive toxicity/efficacy evaluation of investigational agents. To overcome this challenge, we evaluated the safety and activity of a new immunotherapeutic technology that we have pioneered (composed of tumor mRNA complexed into a custom lipid-nanoparticle formulation) in client-owned canines (pet dogs) diagnosed with malignant gliomas. OBJECTIVE/ METHODS Canine malignant gliomas were biopsied for generation of personalized tumor mRNA loaded into our custom lipid-nanoparticle (NP) vector. The patients received RNA-NPs intravenously beginning two weeks after their biopsy once weekly (x3) and no other anti-tumor therapeutic interventions. RESULTS Within a few hours after administration, tumor specific RNA-NPs elicited margination of peripheral blood mononuclear cells, which increased in the subsequent days/weeks post-treatment; suggesting that RNA-NPs mediate lymphoid honing of immune cell populations before egress. RNA-NPs also elicited increased: 1) serum interferon-α that spiked at 2 hours; 2) CD80 and MHCII on CD11c+ cells (demonstrating activation of peripheral DCs); and 3) interferon-γ + T-cells (i.e. activated T-cells). After receiving weekly RNA-NPs (×3), the canines had a steady course. Aside from low-grade fevers on the vaccination days, personalized tumor RNA-NPs (1x) were well tolerated with stable blood counts, chemistries, and renal/liver function tests. All patients assessed developed immunologic response with pseudoprogression or stable/smaller tumors by MRI. Although we have treated a small cohort, we have observed improvement in median/overall survival in all canine patients with terminal gliomas receiving RNA-NPs (compared with historical controls). CONCLUSION RNA-NPs were feasible, safe and immunologically active in client-owned canines with terminal gliomas. We have not appreciated significant toxicities in canines that would preclude investigation in humans at 1x dosing. Although these results need to be validated in larger canine data sets, these results suggest safety and activity of tumor specific RNA-NPs in canines with terminal gliomas.

BACKGROUND: Pediatric brain tumors are poorly immunogenic preventing current immunotherapies (i.e. checkpoint blockers) from having significant activity. Unlocking immunotherapy against these malignancies is predicated on reprogramming their immunogenicity. OBJECTIVE/METHODS: We developed a novel treatment platform, which leverages the use of clinically translatable lipid-nanoparticles (NPs) combined with tumor derived mRNA that simultaneously function as both vaccines and immunomodulating agents to reprogram the systemic/local microenvironments of pediatric brain cancers. RESULTS: Systemic tumor mRNA-NPs localize to lymphoid organs (i.e. liver, spleen lymph nodes) and to the intratumoral milieu, activating the immunologic microenvironment therein through release of type I interferon from plasmacytoid dendritic cells. This culminates in a CD4 and CD8 central memory T cell response against H3.1K27M murine gliomas. In immunologically resistant murine tumor models, RNA-NPs induce robust anti-tumor efficacy and mediate synergistic activity in settings where immune checkpoint inhibitors (i.e. anti-PD-L1 therapy) do not confer therapeutic benefit. We demonstrate safety of RNA-NPs in acute/chronic murine toxicity studies and in a client-owned canine (pet dog) diagnosed with a malignant glioma. In our first canine subject, RNA-NPs elicited activation of dendritic cells, release of type I interferon and activation of CD8+ T cells. CONCLUSION: RNA-NPs bypass MHC restriction and can be made readily available for all patients (and not only HLA specific haplotypes); they also provide a renewable antigen resource that can be used to continuously vaccinate patients for months/years after diagnosis. Through partnership with the Pacific Pediatric Neuro-Oncology Consortium (PNOC), we are in the final stages of FDA-IND submission before first-in-human trials.

BACKGROUND: Diffuse Intrinsic Pontine Glioma (DIPG) remains uniformly recalcitrant and thus necessitates development of novel targeted therapies. The histone mutation in H3K27M is conserved in the preponderance of DIPG patients and may be exploited as a neoepitope for cancer immunotherapy. We have developed a novel treatment platform, which leverages the use of clinically translatable nanoparticles (NPs) combined with H3K27M mRNA neoantigens for in vivo activation of dendritic cells and generation of DIPG specific T cells. OBJECTIVE/METHODS: Since neoantigens have been shown to mediate immunologic response through MHC class II, we sought to identify MHCII restricted epitopes spanning the H3.1K27M junction for development of RNA-NP vaccines against DIPG. RESULTS: We identified MHCII restricted H3.1K27M epitopes not present in the wild-type sequence. We constructed a 25-mer sequence (75 amino acids) spanning the range of epitopes, before cloning it into our custom pGEM-4z plasmid containing a poly A tail and 5’ UTR with a T7 promoter for amplification of MHC-II restricted H3.1K27M mRNA. We complexed this RNA with our custom NP formulation and investigated its immunogenicity in C57Bl/6 mice. Unlike MHC-I restricted epitopes (i.e. OVAlbumin’s SINFEKL epitope), MHC-II restricted H3K27M epitopes elicited significant increases in activated CD4 and CD8 central memory T cells. We demonstrate that this central memory phenotype correlates with anti-tumor efficacy and long-term survival outcomes in murine tumor models. CONCLUSION: RNA-NPs can be made readily available for all DIPG patients (and not only HLA specific haplotypes) providing a renewable antigen resource that can be used to continuously vaccinate patients for months/years after diagnosis. Herein, we identify MHCII restricted H3.1K27M epitopes for activation of immunologic central memory necessary for long-lived anti-tumor efficacy.

Activating transcription factor 4 (ATF4) is a member of the PERK signaling pathway, which directly binds endoplasmic reticulum stress target genes and plays a crucial role in both adaptations to stress and activation of apoptosis. Previous publications demonstrated conflicting evidence on the role of ATF4 in the pathogenesis of neurodegenerative disorders. In this study, we used recombinant adeno-associate virus (rAAV)-mediated gene transfer to investigate if the sustained up-regulation of ATF4 launches a pro-survival or pro-death trend in the dopamine (DA) cells of the substantia nigra pars compacta in a rat model of Parkinson-like neurodegeneration induced by human alpha-synuclein (αS) overexpression. We showed that ATF4 does not protect nigral DA neurons against an αS-induced pathology. Moreover, the rAAV-mediated overexpression of ATF4 resulted in severe nigra-striatal degeneration via activation of caspases 3/7.

BACKGROUND Molecular drivers of cancer immunogenicity in brain tumors are still being unraveled. While BATF3 expression, STING, and interferon response factors (IRFs) are necessary for cancer immunogenicity, the presence of type I interferon (IFN-I) is contextual having been reported to elicit both anti-tumoral and pro-tumoral effects. A better understanding of IFN-I signaling mechanisms is necessary to elucidate drivers of brain cancer immunogenicity and resistance. OBJECTIVE We sought to assess the role of IFN-I signaling in brain tumor immunogenicity and response to immune checkpoint inhibitors (ICIs) in ICI sensitive brain tumor models (i.e. GL261). We then sought to develop strategies to reset IFN-I signaling in ICI resistant brain tumor models (i.e. KR158b). METHODS To reset IFN-I signaling in immunologically ‘cold’ tumors unresponsive to ICIs, we developed lipid-nanoparticles (NPs) to deliver mRNA payloads to the brain tumor microenvironment (TME). RESULTS In immune-sensitive GL261 tumors, we showed that early release of IFN-I unlocks cancer immunogenicity and ICI response. Blockade of IFN-I during tumorigenesis (within 24h, but not days later) increases tumorigenicity and abrogates ICI activity in sensitive tumors. In ICI resistant KR158b tumors, we show that systemic administration of tumor-derived RNA-NPs localize to myeloid cells within the TME for simultaneous activation of multiple innate pathways including BATF3 (necessary for effector DCs), IRF5 (necessary for M2 to M1 macrophage reprograming), and IRF7 (necessary for IFN-I production). These RNA-NPs induce near-immediate release of IFN-I (within hours), reprogram the brain TME in an IFNAR1 (IFN-I receptor) dependent manner, and elicit significant anti-KR158b efficacy as a monotherapy. Following IFNAR1 blockade, RNA-NP mediated anti-tumor efficacy was abrogated. We demonstrated safety of tumor-specific RNA-NPs (derived from KR158b) in acute/chronic GLP toxicity studies without normal-brain cross-reactivity, and confirmed feasibility/safety and immunologic activity in large-animal studies. FUTURE DIRECTIONS We have since received FDA-IND approval for first-in-human trials (IND#BB-19304) in glioblastoma patients.

BACKGROUND Glioblastoma (GBM) can be an effective teacher in the war on COVID-19, as an operative vaccine for either must elicit near-immediate protective responses that overcomes disease heterogeneity and immune suppression. Current prophylactic strategies against COVID-19 utilize mRNA vaccines targeting small fragments of the SARS-CoV-2 genome, but these may not induce robust T cell responses or elicit immunity quickly enough. OBJECTIVE We sought to adapt an FDA-IND approved mRNA vaccine in GBM against COVID-19 for: 1) activation of near immediate immune responses, 2) targeting of full-length SARS-CoV-2 structural proteins, and 3) induction of bidirectional (B and T cell) adaptive immunity. METHODS We utilized a novel engineering design that layers mRNA into a lipid-nanoparticle (NP) shell (much like an onion); this allows greater packaging of mRNA per particle to quickly boost innate/adaptive immune responses against full-length glioblastoma antigens or SARS-CoV-2 structural proteins. RESULTS In small and large animal models, RNA-NPs safely mimic viremia activating the quiescent immune system in only a few hours for induction of protective immunity against its mRNA payload. RNA-NPs activate dendritic cells (DCs), upregulate critical innate gene signatures, and induce antigen-specific cellular and humoral immunity. We found that mice receiving SARS-CoV-2 spike RNA-NPs had more effector T cells after vaccination with significant memory recall expansion after in vitro re-stimulation with overlapping SARS-CoV-2 spike peptide mix. We also found increased release of MIP-1-alpha (i.e. CCL3) previously shown by our group (Mitchell et al. Nature 2015) to be responsible for Th1 mediated memory recall to infectious vaccine antigens in GBM patients. CONCLUSION SARS-CoV-2 RNA-NPs elicit memory recall response after vaccination. We have obtained FDA-IND approval (BB-19304, Sayour) in GBM with SARS-CoV-2 specific amendment (BB-20871) underway to support first-in-human trials of RNA-NPs targeting both GBM and COVID-19.

BACKGROUND Chimeric antigen receptor (CAR) modified T cell therapy is a promising treatment strategy for cancer therapy. We developed IL-8 receptor-linked CD70CAR (8R-70CAR), aiming to enhance T-cell intratumoral trafficking and persistence, guided by IL-8-secreting tumors. The preclinical results show that 8R-70CAR T cells induce complete tumor regression and long-lasting antitumor immunity, which necessitate further clinical development of this technology. OBJECTIVE To assess the toxicity of 8R-70CAR T cells, evaluate in vitro tumor recognition and expansion of the 8R-70CAR T cells, and develop clinically compliant SOPs for the CAR T cell manufacture. METHODS The m8R-70CAR (mouse), h8R-70CAR (human), and control CAR were constructed. Toxicology: C57BL/6J mice were intravenously injected with or without 2x106 m8R-70CAR T cells after total body irradiation (5Gy). The body weight, clinical signs, hematology, serum chemistry, serum cytokines, gross pathology, and histopathology of 12 vital organs were evaluated. Tumor recognition: T cells derived from GBM patients were transduced with h8R-70CAR and then co-cultured with CD70+ glioblastoma. INF-g production was measured. Ex vivo expansion: The G-Rex system was utilized for CAR T cell production, and the expansion of h8R-70CAR T cells was assessed by cell count. RESULTS No CAR T cell-related toxicity was observed in mouse study. In addition to a robust antitumor reactivity, the h8R-70CAR T cells present an auto-stimulative property that elicits greater ex vivo expansion compared to other CAR T cells tested. An approximately 1200-fold expansion was achieved during the 2 weeks CAR T cell production without additional stimulation, which allows production of the CAR T cells on a clinical trial scale using < 100mL of whole blood. CONCLUSION The 8R-70CAR T cells are effective, auto-stimulative, and safe. These properties are fundamental for successful clinical applications in cancer treatment. A phase I trial using the 8R-70CAR T cells in newly diagnosed GBM will be initiated soon.

Introduction: Immunotherapy is promising for patients with treatment-refractory head and neck squamous cell carcinoma (HNSCC). However, greater than 80% do not respond to checkpoint inhibitors, suggesting that the highly immunosuppressive immune microenvironment of HNSCC mediates therapeutic resistance. Our group has developed a novel treatment platform utilizing clinically translatable RNA-nanoparticles (NPs) to remodel the systemic and intratumoral HNSCC immune microenvironment to enable potent immunotherapeutic activity. Objective: The purpose of this study is to examine the immunologic effects and antitumor efficacy of tumor-derived RNA-NPs in murine models of oral cavity squamous cell carcinoma (OCSCC). Materials and Methods: Tumor-derived RNA-NPs were prepared by complexing in vitro transcribed mRNA from MOC1 cells (syngeneic murine oral cavity squamous cell carcinoma cell line) with nanoliposomes. These complexes were injected into MOC1 tumor-bearing C57BL/6 mice. Immunogenicity was determined from spleens and tumors by multiparameter flow cytometry and qPCR analysis. Efficacy was assessed based on subcutaneous tumor volume measurements. Results: Personalized tumor RNA-NPs mediated significant increases in systemic and tumor-infiltrating lymphocytes (TILs). Compared to control animals, RNA-NPs increased peripheral CD8+ T cells (p=0.0007) and decreased regulatory immune cells [CD4+CD25+FoxP3+ (Tregs)] (p=0.0043). WIthin the tumor microenvironment, RNA-NPs increased intratumoral CD3+CD8+ T cells (p =0.0278) and CD3+CD4+ T cells (p=0.0307). qPCR on MOC1 tumors revealed elevated expression of the effector cytokine interferon-γ (NP alone vs. RNA-NP; fold change 1.309 vs. 90.13) and reduced gene expression of arginase-1 (NP alone vs. RNA-NP; fold change 1.29 vs. 0.005), suggesting that RNA-NPs can attenuate the immunosuppressive microenvironment. Compared to control animals or mice receiving PD-L1 monotherapy, RNA-NPs mediated significantly greater antitumor efficacy based on subcutaneous tumor volume measurements (p Conclusion: RNA-NPs reprogram the peripheral and intratumoral HNSCC immune microenvironments and unlock antitumor activity in preclinical models. We have successfully generated tumor-derived RNA-NPs as a renewable resource that can be made readily available for HNSCC patients from a small tissue sample. FDA-IND enabling studies are currently under way in preparation for first-in-human trials. Citation Format: Natalie L. Silver, Rekha R. Garg, Hector R. Mendez-Gomez, Kristianna Fredenberg, Spencer Barnes, Frances L. Weidert, Peter Dziegielewski, Sayour J. Elias, Duane A. Mitchell. Personalized RNA nanoparticles remodel the HNSCC immunologic milieu to unlock immunotherapeutic activity [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr A18.

BACKGROUND: In a randomized phase III study for recurrent glioblastoma (GBM), combination therapy with immune checkpoint inhibitors (ICIs) nivolumab and ipilimumab failed to improve overall survival. Since ICIs appear to be dependent on host-myeloid (and not tumor-cell) expression of PD-L1 (Tang et al. JCI, 2018), we sought to assess if tumor-mRNA nanoparticles (NPs) could prime the systemic and intratumoral GBM milieu with activated PD-L1+ host-myeloid cells sensitizing immunologically ‘cold’ tumors to immunotherapy. METHODS: We systemically administered personalized tumor-derived mRNA encapsulated in translatable lipid-NPs with excess positive charge for enhanced delivery and transfection of peripheral/intratumoral antigen presenting cells (APCs) in murine and large animal canine malignant glioma models. RESULTS: RNA-NPs activate systemic immunity within twenty-four hours, inducing significant increases in the percentage of CD11c+ myeloid-cells expressing PD-L1 and CD86. After only a single RNA-NP vaccine, the bulk of APCs within the spleen, liver, lymph nodes, bone marrow and tumor display an activated phenotype. These PD-L1+ APCs (CD11c+MHC-II+CD86+PD-L1+ cells from intracranial tumors) did not suppress immunity, but rather, heightened interferon-(IFN)-γ reactivity. Addition of ICIs (to animals primed with RNA-NPs) augmented peripheral/intratumoral PD-1+CD8+ cells and mediated synergistic anti-tumor efficacy in settings where ICIs alone did not confer therapeutic benefit. These synergistic effects were mediated by type–I-interferon released from PD-L1+ plasmacytoid dendritic-cells. In translational studies, personalized mRNA-NPs (from whole tumor-transcriptome) were safe and active in a client-owned canine with a spontaneous malignant glioma. In this patient, RNA-NPs elicited robust immunologic activity with increased percentages of activated PD-L1+ APCs and IFNγ+CD8+ cells. CONCLUSION: RNA-NPs elicit widespread immune activation concomitant with inducible PD-L1 expression on intratumoral APCs that can be therapeutically exploited. Since RNA-NPs bypass cost/complexity of cellular therapeutics, are amenable to central distribution, and can be made within days of tumor resection, these formulations can be expeditiously translated as biomodulators of GBM immunogenicity.

Cancer vaccines may be harnessed to incite immunity against poorly immunogenic tumors, however they have failed in therapeutic settings. Poor antigenicity coupled with systemic and intratumoral immune suppression have been significant drawbacks. RNA encoding for tumor associated or specific epitopes can serve as a more immunogenic and expeditious trigger of anti-tumor immunity. RNA stimulates innate immunity through toll like receptor stimulation producing type I interferon, and it mediates potent adaptive responses. Since RNA is inherently unstable, delivery systems have been developed to protect and deliver it to intended targets in vivo. In this review, we discuss liposomes as RNA delivery vehicles and their role as cancer vaccines.

While recurrent medulloblastoma (MB) remains almost uniformly fatal, our group has shown a trend (p=0.07) toward improved survival in patients receiving autologous tumor-RNA pulsed dendritic cells (DCs) coupled with ex vivo expanded total RNA activated T-cells. However, the advancement of autologous cellular therapeutics remains encumbered by significant cost, complexity and time to generation. To circumvent these challenges, we developed a novel treatment platform, which leverages the use of commercially available and clinically translatable nanoparticles (NPs) that can be combined with tumor-derived RNA for near-immediate induction of systemic immunity against MB. We identified a clinically translatable NP formulation for the delivery of RNA to antigen presenting cells for induction of anti-tumor T-cell immunity. When administered intravenously, RNA-NPs increased expression of co-stimulatory molecules on CD11c+ cells throughout reticuloendothelial organs and within the tumor microenvironment; this phenotype was dependent on type I interferon. Targeted inhibition of type I interferon signaling (via INFAR1-mAbs) abrogated anti-tumor immunity mediated by RNA-NPs. We enhanced the immunogenicity of this platform by simply combining mRNAs encoding for immunomodulatory molecules (i.e. HCV-PAMPs, GM-CSF) or by combining RNA-NPs with immune checkpoint inhibitors. Addition of checkpoint inhibitors to RNA-NPs mediated synergistic anti-tumor activity in settings where PD-1 or PD-L1 inhibition alone did not confer therapeutic benefit. In a pre-clinical cellular immunotherapy model targeting an anaplastic murine MB, RNA NPs superseded DCs in mediating anti-tumor activity. Based on these findings, we are exploring the preclinical safety, efficacy and immunologic effects of RNA-NPs targeting malignant brain tumors in canines (UF-IACUC#:201609430) before first in-human evaluation.

INTRODUCTION Intratumoral heterogeneity is increasingly recognized as a determinant of therapy resistance and disease recurrence; this is exemplified by glioblastoma (GBM), one of the most lethal malignancies. We recently revealed that GBM contain cell subpopulations with distinct metabolic requirements, with fast-cycling cells (FCCs) harnessing aerobic glycolysis, and treatment-resistant slow-cycling cells (SCCs) preferentially engaging lipid metabolism. How the different tumor cell populations interact with immune cells and how this metabolic heterogeneity shapes the immune landscape in GBM has yet to be understood. OBJECTIVES: The objectives of this study are to understand the mechanisms of communication in the tumor microenvironment, specifically to characterize the metabolic interactions between SCCs (a therapeutically resistant population of cancer cells that drive disease progression and recurrence) and the immune compartment. METHODS The murine glioma cell line KR158 (derived from a Nf1;Trp53 mutant mouse) was used to establish the slow-cycling cell paradigm and metabolic heterogeneity in an immune-competent model of glioma. RESULTS Similar to what we observed in patient-derived specimens, mouse KR158-derived SCCs demonstrate tumorigenicity, treatment resistance and up-regulation of stemness programs and lipid metabolic pathways. We determined that tumor progression is regulated by the interaction of SCCs with the immune system and established that these cells are driving a pro-tumorigenic microenvironment via the recruitment of immune suppressive myeloid cells. Importantly, the immune microenvironment shaped by SCCs is marked by specific metabolic features showing enhanced lipid exchange capacities that we propose are exploited by SCCs to support their survival and functions. CONCLUSION Our study indicates that SCCs play a pivotal role in shifting the GBM milieu toward an immune regulatory phenotype but importantly reveals an unprecedented metabolic cooperation, which represents a novel therapeutic target to antagonize GBM.

SummaryTranscription of expanded microsatellite repeats is associated with multiple human diseases, including myotonic dystrophy, Fuchs’ endothelial corneal dystrophy, andC9orf72-ALS/FTD. Eliminating or reducing production of RNA and proteins arising from these expanded loci holds therapeutic benefit. Here, we tested the hypothesis that a deactivated form of the Cas9 enzyme impedes transcription across expanded microsatellites. We observed a repeat length-, PAM-, and strand-dependent reduction in the abundance of repeat-containing RNAs upon targeting dCas9 directly to repeat sequences. Aberrant splicing patterns were rescued in DM1 cells, and production of RAN peptides characteristic of DM1, DM2, andC9orf72-ALS/FTD cells was drastically decreased. Systemic delivery of dCas9/gRNA by adeno-associated virus led to reductions in pathological RNA foci, rescue of chloride channel 1 protein expression, and decreased myotonia. These observations suggest that transcription of microsatellite repeat-containing RNAs is more sensitive to perturbation than transcription of other RNAs, indicating potentially viable strategies for therapeutic intervention.

The transcription factor Nurr1 is expressed in the mouse olfactory bulb (OB), although it remains unknown whether it influences the generation of dopaminergic neurons (DA) (DA neurons) in cells isolated from this brain region. We found that expressing Nurr1 in proliferating olfactory bulb stem cells (OBSCs) produces a marked inhibition of cell proliferation and the generation of immature neurons immunoreactive for tyrosine hydroxylase (TH) concomitant with marked upregulations of Th, Dat, Gad, and Fgfr2 transcripts. In long-term cultures, these cells develop neurochemical and synaptic markers of mature-like mesencephalic DA neurons, expressing GIRK2, VMAT2, DAT, calretinin, calbindin, synapsin-I, and SV2. Concurring with the increase in both Th and Gad expression, a subpopulation of induced cells was both TH- and GAD-immunoreactive indicating that they are dopaminergic-GABAergic neurons. Indeed, these cells could mature to express VGAT, suggesting they can uptake and store GABA in vesicles. Remarkably, the dopamine D1 receptor agonist SKF-38393 induced c-Fos in TH(+) cells and dopamine release was detected in these cultures under basal and KCl-evoked conditions. By contrast, cotransducing the Neurogenin2 and Nurr1 transcription factors produced a significant decrease in the number of TH-positive neurons. Our results indicate that Nurr1 overexpression in OBSCs induces the formation of two populations of mature dopaminergic neurons with features of the ventral mesencephalon or of the OB, capable of responding to functional dopaminergic stimuli and of releasing dopamine. They also suggest that the accumulation of Fgfr2 by Nurr1 in OBSCs may be involved in the generation of DA neurons.

BACKGROUND: Brain tumors are particularly difficult to treat due to their relative isolation behind the blood brain barrier. Cytotoxic T cells elicited by cancer vaccines are capable of penetrating this barrier, but are limited by innate immune cells in tumor microenvironments that inhibit T cell function. There is therefore an unmet need for a method to reprogram the immune cells in the tumor microenvironment to promote antitumor T cell responses. OBJECTIVE: We previously reported that systemically administered liposomes bearing RNA encoding tumor antigens profoundly activate innate immune cells in reticuloendothelial system (RES) organs. Here, we report a modified liposome formulation capable of redirecting this immunomodulatory nucleic acid cargo to immune cells in brain tumors. APPROACH: Cationic liposomes with varying compositions were loaded with Cy3-labelled RNA or siRNA and injected intravenously into glioma-bearing mice. RNA uptake was assessed with flow cytometry and immunofluorescence microscopy after 18 hours. RESULTS: Inclusion of cholesterol within liposomes increased mRNA uptake in intracranial GL261 and KR158b tumors after systemic injection in a dose-dependent manner. Optimized tumor-homing liposomes delivered mRNA encoding tumor antigens to CD45+ immune cells in both tumors. These liposomes were also used to deliver siRNA against programmed death ligand 1 (PDL1). siRNA-loaded liposomes reduced PDL1 expression on dendritic cells ex vivo and on transfected CD45+ cells in murine brain tumors. CONCLUSIONS: Our optimized liposomes effectively deliver mRNA and siRNA to immune cells in multiple murine brain tumors. Future work will consider the mechanism of this enhanced delivery and the use of tumor-homing liposomes to deliver other immunomodulatory biomolecules.

INTRODUCTION: Conventional therapies most effectively eliminate highly proliferative tumor cells but leave behind residual slow-cycling cancer stem cells (SCCs) that evade treatment and ultimately seed disease recurrence. We reported the existence of SCCs that exhibit enhanced invasiveness, tumorigenicity and resistance to therapy in glioblastoma (GBM). The increased tumorigenicity of these GBM SCC suggests they may have enhanced immunoediting capacity. OBJECTIVES: We speculate that GBM SCCs drive disease progression and recurrence through immune escape. The objective of this study is to characterize the GBM SCC interface with the immune system and identify immunosuppressive mechanisms employed by these cells. METHODS: SCCs were isolated from mouse and human models of malignant glioma and separated by flow cytometry based on their ability to retain CellTrace labeling. RESULTS: Draining lymph nodes from animals bearing SCC-derived malignant gliomas showed decreased CD8(+) and increased CD4(+)/Foxp3(+) cells. Immune gene signature analysis of tumor infiltrates uncovered enhanced recruitment of macrophages to SCC-derived tumors, with ApoE being the most over-expressed. ApoE promotes macrophage polarization toward the immunosuppressive M2 phenotype and inhibits T cell interferon-(IFN)-γ secretion. Using the IFN-γ reporter (GREAT) mice, we found that tumors derived from SCCs repressed IFN-γ secretion/expression by in vivo imaging, ELISA and RNA sequencing. This correlated with the up-regulation of gene networks in SCCs involved in immunosuppression, specifically CSF1 a prominent survival factor for macrophages. CONCLUSION: The immune surveillance hypothesis suggests that oncogenesis, driven by cancer cell immunoediting, shapes the immune system toward a pro-tumorigenic phenotype. Our study indicates that SCCs play a pivotal role in shifting the GBM immune milieu toward a regulatory phenotype characterized by M2 macrophages polarized by ApoE signaling.

NURR1 is an essential transcription factor for the differentiation, maturation, and maintenance of midbrain dopaminergic neurons (DA neurons) as it has been demonstrated using knock-out mice. DA neurons of the substantia nigra pars compacta degenerate in Parkinson’s disease (PD) and mutations in the Nurr1 gene have been associated with this human disease. Thus, the study of NURR1 actions in vivo is fundamental to understand the mechanisms of neuron generation and degeneration in the dopaminergic system. Here, we present and discuss findings indicating that NURR1 is a valuable molecular tool for the in vitro generation of DA neurons which could be used for modeling and studying PD in cell culture and in transplantation approaches. Transduction of Nurr1 alone or in combination with other transcription factors such as Foxa2, Ngn2, Ascl1, and Pitx3, induces the generation of DA neurons, which upon transplantation have the capacity to survive and restore motor behavior in animal models of PD. We show that the survival of transplanted neurons is increased when the Nurr1-transduced olfactory bulb stem cells are treated with GDNF. The use of these and other factors with the induced pluripotent stem cell (iPSC)-based technology or the direct reprogramming of astrocytes or fibroblasts into human DA neurons has produced encouraging results for the study of the cellular and molecular mechanisms of neurodegeneration in PD and for the search of new treatments for this disease.

Crossing the blood–brain and the blood–cerebrospinal fluid barriers (BCSFB) is one of the fundamental challenges in the development of new therapeutic molecules for brain disorders because these barriers prevent entry of most drugs from the blood into the brain. However, some large molecules, like the protein transferrin, cross these barriers using a specific receptor that transports them into the brain. Based on this mechanism, we engineered a receptor/ligand system to overcome the brain barriers by combining the human transferrin receptor with the cohesin domain from Clostridium thermocellum, and we tested the hybrid receptor in the choroid plexus of the mouse brain with a dockerin ligand. By expressing our receptor in choroidal ependymocytes, which are part of the BCSFB, we found that our systemically administrated ligand was able to bind to the receptor and accumulate in ependymocytes, where some of the ligand was transported from the blood side to the brain side.

Biodistribution analysis is a key step in the evaluation of adeno-associated virus (AAV) capsid variants, whether natural isolates or produced by rational design or directed evolution. Indeed, when screening candidate vectors, accurate knowledge about which tissues are infected and how efficiently is essential. We describe the design, validation, and application of a new vector, pTR-UF50-BC, encoding a bioluminescent protein, a fluorescent protein and a DNA barcode, which can be used to visualize localization of transduction at the organism, organ, tissue, or cellular levels. In addition, by linking capsid variants to different barcoded versions of the vector and amplifying the barcode region from various tissue samples using barcoded primers, biodistribution of viral genomes can be analyzed with high accuracy and efficiency.

Crossing the blood-brain and the blood-cerebrospinal fluid barriers are one of the fundamental challenges in the development of new therapeutic molecules for brain disorders because they prevent entry of most drugs from the blood into the brain. However, some large molecules, like the protein transferrin, cross these barriers using a specific receptor that transports them into the brain. Mimicking nature, we engineered a receptor/ligand system to cross the brain barrier by combining the human transferrin receptor with the cohesin domain from Clostridium thermocellum, and we tested it in the choroid plexus of the mouse brain with a dockerin ligand. By expressing our receptor in choroidal ependymocytes, which are part of the blood-cerebrospinal fluid barrier, we found that our systemically administrated ligand was able to bind to the receptor and accumulate in ependymocytes, where some of the ligand was transported from the blood side to the brain side.

10 páginas, 8 figuras -- PAGS nros. 2739-2748, Neural stem cells depend on insulin-like growth factor I (IGF-I) for differentiation. We analysed how activation and inhibition of the PI 3-kinase–Akt signalling affects the number and differentiation of mouse olfactory bulb stem cells (OBSCs). Stimulation of the pathway with insulin and/or IGF-I, led to an increase in Akt phosphorylated on residues Ser473 and Thr308 (P-AktSer473 and P-AktThr308, respectively) in proliferating OBSCs, and in differentiating cells. Conversely, P-AktSer473 levels decreased by 50% in the OB of embryonic day 16.5-18.5 IGF-I knockout mouse embryos. Overexpression of PTEN, a negative regulator of the PI 3-kinase pathway, caused a reduction in the basal levels of P-AktSer473 and P-AktThr308 and a minor reduction in IGF-I-stimulated P-AktSer473. Although PTEN overexpression decreased the proportion of neurons and astrocytes in the absence of insulin/IGF-I, it did not alter the proliferation or survival of OBSCs. Accordingly, overexpression of a catalytically inactive PTEN mutant promoted OBSCs differentiation. Inhibition of PI 3-kinase by LY294002 produced strong and moderate reductions in IGF-I-stimulated P-AktSer473 and P-AktThr308, respectively. Consequently, LY294002 reduced the proliferation of OBSCs and the number of neurons and astrocytes, and also augmented cell death. These findings indicate that OBSC differentiation is more sensitive to lower basal levels of P-Akt than proliferation or death. By regulating P-Akt levels in opposite ways, IGF-I and PTEN contribute to the fine control of neurogenesis in the olfactory bulb, This work was funded by the grants from the MEC (Spain) BFU 2004-2352 to F.d.P., SAF2004-05798 to C.V.-A. and BMC 2003-07751 to E.J.d.l.R., and from the Fundación "la Caixa" NE03/72-02 to C.V.-A. G.O., M.J.Y.-B, E.V.-V. and H.R.M.-G. were supported by doctoral fellowships either from the MEC or the "Comunidad Autónoma de Madrid"

The transcription factor Nurr1 is expressed in the mouse olfactory bulb (OB), although it remains unknown whether it influences the generation of dopaminergic neurons (DA) (DA neurons) in cells isolated from this brain region. We found that expressing Nurr1 in proliferating olfactory bulb stem cells (OBSCs) produces a marked inhibition of cell proliferation and the generation of immature neurons immunoreactive for tyrosine hydroxylase (TH) concomitant with marked upregulations of Th, Dat, Gad, and Fgfr2 transcripts. In long-term cultures, these cells develop neurochemical and synaptic markers of mature-like mesencephalic DA neurons, expressing GIRK2, VMAT2, DAT, calretinin, calbindin, synapsin-I, and SV2. Concurring with the increase in both Th and Gad expression, a subpopulation of induced cells was both TH- and GAD- immunoreactive indicating that they are dopaminergic- GABAergic neurons. Indeed, these cells could mature to express VGAT, suggesting they can uptake and store GABA in vesicles. Remarkably, the dopamine Dl receptor agonist SKF-38393 induced c-Fos in TH(+) cells and dopamine release was detected in these cultures under basal and KCl-evoked conditions. By contrast, cotransducing the Neurogenin2 and Nurr1 transcription factors produced a significant decrease in the number of TH- positive neurons. Our results indicate that Nurr1 overexpression in OBSCs induces the formation of two populations of mature dopaminergic neurons with features of the ventral mesencephalon or of the OB, capable of responding to functional dopaminergic stimuli and of releasing dopamine. They also suggest that the accumulation of Fgfr2 by Nurr1 in OBSCs may be involved in the generation of DA neurons.

22 páginas, 16 figuras.-- et al., [Background]: Nolz1 is a zinc finger transcription factor whose expression is enriched in the lateral ganglionic eminence (LGE), although its function is still unknown. [Results]: Here we analyze the role of Nolz1 during LGE development. We show that Nolz1 expression is high in proliferating neural progenitor cells (NPCs) of the LGE subventricular zone. In addition, low levels of Nolz1 are detected in the mantle zone, as well as in the adult striatum. Similarly, Nolz1 is highly expressed in proliferating LGE-derived NPC cultures, but its levels rapidly decrease upon cell differentiation, pointing to a role of Nolz1 in the control of NPC proliferation and/or differentiation. In agreement with this hypothesis, we find that Nolz1 over-expression promotes cell cycle exit of NPCs in neurosphere cultures and negatively regulates proliferation in telencephalic organotypic cultures. Within LGE primary cultures, Nolz1 over-expression promotes the acquisition of a neuronal phenotype, since it increases the number of β-III tubulin (Tuj1)- and microtubule-associated protein (MAP)2-positive neurons, and inhibits astrocyte generation and/or differentiation. Retinoic acid (RA) is one of the most important morphogens involved in striatal neurogenesis, and regulates Nolz1 expression in different systems. Here we show that Nolz1 also responds to this morphogen in E12.5 LGE-derived cell cultures. However, Nolz1 expression is not regulated by RA in E14.5 LGE-derived cell cultures, nor is it affected during LGE development in mouse models that present decreased RA levels. Interestingly, we find that Gsx2, which is necessary for normal RA signaling during LGE development, is also required for Nolz1 expression, which is lost in Gsx2 knockout mice. These findings suggest that Nolz1 might act downstream of Gsx2 to regulate RA-induced neurogenesis. Keeping with this hypothesis, we show that Nolz1 induces the selective expression of the RA receptor (RAR)β without altering RARα or RARγ. In addition, Nozl1 over-expression increases RA signaling since it stimulates the RA response element. This RA signaling is essential for Nolz1-induced neurogenesis, which is impaired in a RA-free environment or in the presence of a RAR inverse agonist. It has been proposed that Drosophila Gsx2 and Nolz1 homologues could cooperate with the transcriptional co-repressors Groucho-TLE to regulate cell proliferation. In agreement with this view, we show that Nolz1 could act in collaboration with TLE-4, as they are expressed at the same time in NPC cultures and during mouse development. [Conclusions]: Nolz1 promotes RA signaling in the LGE, contributing to the striatal neurogenesis during development., This study was supported by grants from the Ministerio de Ciencia e Innovación (SAF2008-04360, to JA; SAF2009-07774 and PLE2009-0089, to JMC; SAF2004- 05798, to CV-A), Spain; Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación (CIBERNED, to JA and CV-A; and RETICS (RD06/0010/0006; Red de Terapia Celular), to JMC), Spain; the Fundació La Marató de TV3 (to JA), Spain; Generalitat de Catalunya (2009SGR-00326 to JA), Spain; and the National Institutes of Health (EY013969, to GD). The Cell Therapy Program is supported by the Centre of Regenerative Medicine in Barcelona (CMRB; Promt-0901, to JMC; Generalitat de Catalunya), Spain.

The T-box brain 1 (Tbr1) gene encodes a transcription factor necessary for the maintenance and/or differentiation of glutamatergic cells in the olfactory bulb (OB) and cortex, although its precise function in the development of glutamatergic neurons is not known. Furthermore, Tbr1 has not been reported to regulate the formation of glial cells. We show that Tbr1 is expressed during the initial stages in the generation of glutamatergic mitral neurons from dividing progenitors in the E12.5 mouse OB. Retroviral-mediated overexpression of Tbr1 in cultured embryonic and adult OB stem cells (OBSC) produces a marked increase in the number of TuJ1+ neurons (including VGLUT1+ glutamatergic and GABA+ neurons) and O4+ oligodendrocytes. Moreover, transduction of Tbr1 inhibits the production of GFAP+ astrocytes from both cultured OBSC and dividing progenitor cells in vivo. These results show that the expression of Tbr1 in neural stem and progenitor cells prevents them from following an astrocyte fate during OB development. Our findings suggest that the transduction of Tbr1 into neural stem cells could be useful to increase the production of neurons and oligodendrocytes in studies of neuroregeneration. © 2010.

12 pages, 7 figures.-- PMID: 19544461 [PubMed].-- Printed version published Jul 2009., Supporting information (Suppl. figures S1-S9, tables S1-S2) available at: http://www3.interscience.wiley.com/journal/122302104/suppinfo, Cell lineages generated during development and tissue maintenance are derived from self-renewing stem cells by differentiation of their committed progeny. Recent studies suggest that epigenetic mechanisms, and in particular the Polycomb group (PcG) of genes, play important roles in controlling stem cell self-renewal. Here, we address PcG regulation of stem cell self-renewal and differentiation through inactivation of Ring1B, a histone H2A E3 monoubiquitin ligase, in embryonic neural stem cells (NSCs) from the olfactory bulb of a conditional mouse mutant line. We show that neural stem/progenitor cell proliferation in vivo and in neurosphere assays is impaired, lacking Ring1B, and their self-renewal and multipotential abilities, assessed as sphere formation and differentiation from single cells, are severely affected. We also observed unscheduled neuronal, but not glial, differentiation of mutant stem/progenitor cells under proliferating conditions, an alteration enhanced in cells also lacking Ring1A, the Ring1B paralog, some of which turned into morphologically identifiable neurons. mRNA analysis of mutant cells showed upregulation of some neuronal differentiation-related transcription factors and the cell proliferation inhibitor Cdkn1a/p21, as well as downregulation of effectors of the Notch signaling pathway, a known inhibitor of neuronal differentiation of stem/progenitor cells. In addition, differentiation studies of Ring1B-deficient progenitors showed decreased oligodendrocyte formation in vitro and enhanced neurogenesis and reduced gliogenesis in vivo. These data suggest a role for Ring1B in maintenance of the undifferentiated state of embryonic neural stem/progenitor cells. They also suggest that Ring1B may modulate the differentiation potential of NSCs to neurons and glia., M.R-T. and H. M-G. were recipients of FPU and FPI fellowships, from the Ministerio de Educacion y Ciencia and Comunidad de Madrid, respectively. This work was supported by grants SAF2007-65957-C02-01 (M.V.), the Onco-Cycle program from the Comunidad de Madrid (M.V.), SAF2004-05798, and CIBERNED CB06/05/0065 from Instituto de Salud Carlos III (C.V-A.).