Nascari, David

Abstract INTRODUCTION Anti‐amyloid beta (Aβ) monoclonal antibodies are effective at lowering amyloid in Alzheimer's disease (AD). However, whether Fc‐mediated effector function is absolutely required for efficacy is not completely understood. This is important for optimizing therapeutic efficacy and mitigating side effects such as amyloid‐related imaging abnormalities (ARIA). Antibodies lacking Fc effector function, like single‐domain antibodies (nanobodies), offer a unique tool to dissect these mechanisms, as their small size facilitates blood–brain barrier (BBB) penetration and allows Fc‐mediated functions to be studied independently. METHODS We immunized a llama with Aβ aggregates and constructed a phage display library to screen for aggregate‐specific nanobodies. Lead candidates were characterized by epitope mapping and binding affinity to amyloid plaques in both murine and human AD brain tissues. We further assessed their BBB permeability and evaluated their efficacy in clearing pre‐existing plaques in amyloid precursor protein (APP)/presenilin 1 (PS1) mice. RESULTS We identified two lead nanobodies, 3A11 and 2D10, that bind distinct epitopes and specifically bind Aβ plaques in murine and human AD brain tissues. Following systemic administration, the monovalent, unmodified (Fc‐less) 2D10 nanobody, but not 3A11, successfully crossed the BBB and engaged amyloid plaques in APP/PS1 mice. However, despite robust target engagement, the Fc‐less 2D10 failed to recruit microglia or reduce plaque burden. In contrast, an engineered 2D10‐Fc fusion antibody potently cleared amyloid plaques, achieving a reduction in pathology comparable to aducanumab treatment. This efficacy was directly correlated with Fc‐mediated microglial recruitment and activation, demonstrating that the Fc domain is essential for phagocytic plaque removal. DISCUSSION Our findings demonstrate that Fc effector function is indispensable for microglial‐mediated amyloid clearance in vivo. By clarifying this fundamental mechanism, this study provides a framework for the rational design of next‐generation immunotherapies. Furthermore, 2D10‐Fc represents a promising therapeutic candidate, combining the high‐affinity targeting of nanobodies with the effector power necessary for robust plaque clearance.

Abstract INTRODUCTION Neurodegenerative diseases often involve overlapping alpha‐synuclein (asyn), amyloid beta, and tau proteinopathies, yet the mechanisms, impact, and directionality of their interactions remain unclear. METHODS We induced brain‐wide neuronal asyn/tau pathologies via viral expression of wild‐type asyn, mutant asyn E46K , mutant tau A152T , or both asyn E46K /tau A152T in adult amyloidosis knock‐in mice and controls, either post‐plaque deposition (6 months old) or pre‐plaque (3 months old). Open‐field behavior was assessed baseline and 3 and 6 months post‐transduction, followed by neuropathology and neuroinflammation analyses. RESULTS Post‐plaque induction in amyloid mice increased asyn/tau total and phosphorylated levels and exacerbated amyloid‐related hyperlocomotion/anxiety. Pre‐plaque induction produced robust phosphorylated pathologies irrespective of amyloid, while causing similar amyloid‐dependent behavioral synergy. Tau pathology drove LGALS3 + inflammatory glial responses in white‐matter fibers. DISCUSSION Amyloid context gates vulnerability, with certain synergies manifesting across stages. White‐matter gliosis is a novel mechanism of tau A152T risk. Together, our data argue for the development of stage‐aware, multitarget interventions and biomarkers.

Abstract Background Glioblastoma (GBM) is driven, in part, by glioma stem cells (GSCs), which sustain therapeutic resistance and recurrence. OLIG2 is a key regulator of GSC programs but the signaling pathways that cooperate with Oligodendrocyte transcription factor 2 (OLIG2) to maintain GSC states remain incompletely defined. Although Signal transducer and activator of transcription (STAT) signaling has been implicated in GSC biology, work to date has focused primarily on STAT3, and the contribution of STAT5 remains poorly defined. Here, we investigated whether STAT5B functionally cooperates with OLIG2 in sustaining GSC phenotypes. Methods Transcriptomic analyses, proximity ligation assays and biochemical studies were utilized to define OLIG2-STAT5B interactions in patient-derived GSCs. Functional consequences of OLIG2, STAT5B, BIRC5, and NUSAP1 suppression were assessed using small interfering RNA/short hairpin RNA-knockdown, stemness, and migration assays in EGFRvIII-expressing GSCs. In vivo tumor growth studies were performed using orthotopic xenograft models. Results OLIG2 and STAT5B expression were positively correlated in GBM datasets and patient-derived models. OLIG2 physically associated with STAT5B in EGFRvIII-expressing GSCs, and loss of OLIG2 reduced STAT5 activation, supporting a functional link between these factors. OLIG2 or STAT5B suppression induced convergent transcriptional changes, including downregulation of genes associated with GSC maintenance and proliferation, notably stemness regulators BIRC5 and NUSAP1. Silencing BIRC5 or NUSAP1 impaired GSC self-renewal and migration. In orthotopic models, STAT5B knockdown prolonged survival and phenocopied OLIG2 suppression and stemness loss. Conclusions These findings identify STAT5B as a functional partner of OLIG2 in GBM and define anOLIG2-STAT5B transcriptional axis that sustains GSC maintenance and malignant behavior. Targeting this axis may represent a therapeutic strategy to disrupt treatment-refractory glioma cell states.

Abstract Glioblastoma (GBM) and Alzheimer’s disease (AD) are devastating, age associated disorders with no cure. Epidemiologic data has established an inverse comorbidity between AD and cancer, including GBM, with up to a 50% reduction of cancer incidence in AD patients. While the underlying biology remains unclear, myeloid cells, which are central players in both neurodegeneration and tumor immunity, may serve as a mechanistic link. We hypothesize that myeloid cells activated by pre-existing AD pathology suppress tumor growth more effectively than homeostatic microglia. In this study, age-matched APPNL-G-F/MAPT double knock-in (henceforth “AD”) and wildtype (WT) mice received orthotopic xenografts of syngeneic GBM cell lines (GL261, SB28) (n=15/sex/genotype). We observed a significant survival difference, with AD mice living an average of 20% longer than WT mice (p<0.0001). In vivo luciferase imaging revealed impaired engraftment of tumor cells in AD mice compared to WT a week post-engraftment (p<0.05). At the microscopic level, tumors in AD mice were found to have nearly 2-fold the amount of tumor-infiltrating myeloid cells (p<0.01), with the proportion of anti-tumoral “activated” myeloid cells also being greater (p<0.05). Tumors in AD mice were found to have markedly higher immune infiltrate at the tumor rim and margin (p<0.001). We also observed striking astrogliosis (GFAP+) and microgliosis (P2RY12+) in both the tumor rim (p<0.05) and margin (p<0.01) in AD animals. This robust glial response was significantly higher in AD mice bearing tumor compared to both WT mice bearing tumor and sham AD mice. Lastly, we utilized a luciferase stain to visualize tumor cells that invaded beyond the bulk tumor. We found that both the quantity (p<0.01) and invasion distance of tumor cells (p<0.05) was lower in AD mice. We demonstrate that an AD-induced inflammatory microenvironment antagonizes glioma growth, providing a foundation for novel GBM treatment strategies that potentially exploit these immune signals.

Abstract Glioma stem cells (GSCs) are key drivers of glioblastoma (GBM) progression, therapy resistance, and recurrence, making them critical therapeutic targets. While the lineage-defining transcription factor OLIG2 is critical for GSC maintenance, the molecular co-regulators and downstream pathways it engages remain poorly defined. Here, we identify a previously unrecognized, functionally significant interaction between OLIG2 and STAT5B, uncovering a novel regulatory axis in GSCs. Using proximity ligation assay (PLA), we demonstrate that OLIG2 interacts with STAT5 in human and mouse GSC models, particularly in EGFRvIII-mutant cells. We find that OLIG2 preferentially partners with STAT5B and not STAT5A. Knockdown studies in GSCs reveal that OLIG2 and STAT5B co-regulate critical oncogenes BIRC5 and NUSAP1, both of which are required for sphere formation and migration capacity of EGFRvIII positive GSCs. In orthotopic xenograft models, knockdown of either STAT5B or OLIG2 significantly prolongs survival reduces expression of stemness and invasion markers, SOX2, VIMENTIN, and NUSAP1. In contrast, STAT5A knockdown fails to recapitulate these phenotypes, underscoring the role of OLIG2-STAT5B signaling in GSCs. These findings reveal a novel OLIG2-STAT5B transcriptional circuit that plays a role in GSC stemness maintenance, invasion, and tumor growth, particularly in EGFRvIII-driven gliomas. Targeting this axis may offer a new avenue for GBM treatment.

Abstract High-grade gliomas represent the most common type of primary adult malignant brain tumor. IDH1/2 mutations are linked to lower-grade gliomas and better patient outcomes; however, molecular profiling has revealed additional alterations that drive aggression. CDKN2A/B loss in IDH-mutant astrocytoma is recognized as a key marker of grade 4 tumor biology, yet there remain no effective targeted therapies in aggressive gliomas. Here, we analyzed a cohort of patient-derived IDH-mutant astrocytoma with whole-exome and RNA sequencing data and identified several candidate genes and pathways concurrently regulated with CDKN2A/B loss, revealing an enhanced signature related to vascular processes. We sought to elucidate the angiogenic mechanisms and functional outcomes associated with high-grade behavior following CDKN2A/B loss in IDH-mutant astrocytoma to inform future therapeutic strategies. We used grade 4 IDH-mutant astrocytoma patient-derived xenograft (PDX) and established cell lines harboring homozygous CDKN2A/B deletion. We re-expressed the cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed reduced proliferation compared to parental lines. Re-expression of p14, p15, or p16 also resulted in decreased glioma cell migration and invasion. Intriguingly, re-expressing these regulators reduced VEGF secretion. HUVEC cells cultured with conditioned media (CM) from the re-expression glioma lines decreased canonical activation of PI3K/Akt and Stat3 signaling and a diminished capacity to promote endothelial migration, invasion, and tube formation. Furthermore, in vivo Matrigel plug assays using CM from the re-expression lines showed a decreased ability to recruit endothelial cells, pericytes, and form vascular organized structures. We identified the WT1 transcription factor as an upstream regulator of angiogenesis. WT1 expression was inversely correlated with CDKN2A/B expression in patient data, and knockdown of WT1 in astrocytoma cells reduced VEGF secretion and impaired ability to promote endothelial migration. Taken together, our findings reveal a novel role for WT1 in VEGF-driven angiogenesis in IDH-mutant astrocytoma with CDKN2A/B homozygous deletion.

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, with few effective treatments. EGFR alterations, including expression of the truncated variant EGFRvIII, are among the most frequent genomic changes in these tumors. EGFRvIII is known to preferentially signal through STAT5 for oncogenic activation in GBM, yet targeting EGFRvIII has yielded limited clinical success to date. In this study, we employed patient-derived xenograft (PDX) models expressing EGFRvIII to determine the key points of therapeutic vulnerability within the EGFRvIII-STAT5 signaling axis in GBM. Our findings reveal that exogenous expression of paralogs STAT5A and STAT5B augments cell proliferation and that inhibition of STAT5 phosphorylation in vivo improves overall survival in combination with temozolomide (TMZ). STAT5 phosphorylation is independent of JAK1 and JAK2 signaling, instead requiring Src family kinase (SFK) activity. Saracatinib, an SFK inhibitor, attenuates phosphorylation of STAT5 and preferentially sensitizes EGFRvIII+ GBM cells to undergo apoptotic cell death relative to wild-type EGFR. Constitutively active STAT5A or STAT5B mitigates saracatinib sensitivity in EGFRvIII+ cells. In vivo, saracatinib treatment decreased survival in mice bearing EGFR WT tumors compared to the control, yet in EGFRvIII+ tumors, treatment with saracatinib in combination with TMZ preferentially improves survival.

Abstract Glioblastoma (GBM) and Alzheimer’s disease (AD) are two devastating central nervous system diagnoses with no known cure. Both diseases are associated with advanced age. The majority of GBM tumors form in the frontal and temporal lobes, two of the brain regions most impacted by amyloid and tau pathology in AD. Females have a higher risk of AD, while males have a higher risk of GBM. Several large case series have established epidemiological evidence that the two diseases are inversely correlated. Nevertheless, it remains unknown whether presence of subclinical amyloid or tau pathology antagonizes the establishment or progression of GBM. The present study sought to characterize GBM growth, progression, and immune response in the setting of concomitant AD pathology using the syngeneic murine GL261 tumor model. To further understand the tumor cell changes that occur in the presence or absence of AD pathology, we engineered GL261 with a dual-tagged vector consisting of RiboTag (to allow for full-length mRNA profiling) and TurboID (to allow for proteomic profiling). GL261 cells were injected intracranially into APPNL-G-F/NL-G-F - MAPThuman/human, APPNL-G-F/+ - MAPThuman/+, and wildtype C57BL/6J mice. Tumors in both wildtype and AD conditions contained ~50% intratumoral myeloid cells (Iba+, P2RY12-). Differential activation of intratumoral myeloid cells will be assessed with immunohistochemistry. Microgliosis (IBA1, P2RY12) and astrogliosis (GFAP) around the tumor in the setting of Alzheimer’s pathology versus normal conditions will be compared. Invasiveness, proliferation, DNA damage (pH2AX), and apoptosis (cleaved PARP, cleaved Caspase 3) will be compared. Tumor cell-specific changes unique to tumors in the AD microenvironment will be assessed transcriptionally with RiboTag profiling as well as proteomically with TurboID purifications. Our preliminary data suggests that the presence of concomitant AD pathology affects GBM growth and progression as well as the immune response to the tumor, and warrants further investigation. Citation Format: David Nascari, Ryan Eghlimi, Angad Beniwal, Drake Alton, John Fryer, Nhan L. Tran. Altered tumor microenvironment in animal model of concomitant GBM and Alzheimer's pathology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5562.

Abstract Glioblastoma (GBM) is a high grade glioma that accounts for the majority of primary malignant brain tumors. The standard of care for GBM consists of maximal surgical resection, concurrent radiation and temozolomide (TMZ), and adjuvant TMZ. However, this has only led to a modest increase in median patient survival. TROY (TNFRSF19) is an orphan member of the TNF receptor superfamily that is differentially upregulated in GBM with low expression in normal brain tissue. Previously, we have reported that TROY is overexpressed in GBM and signals to mediate cell invasion and therapeutic resistance. Propentofylline (PPF) is a well-studied synthetic methylxanthine derivative that has strong BBB penetrance. We have shown that PPF decreases TROY expression in gliomas, inhibits invasion, and sensitizes GBM to TMZ in vitro. Here we examined the efficacy of PPF in combination with TMZ using in vivo studies of intracranial models of GBM patient-derived xenograft (PDX) models in murine. We tested 3 models of GBM PDX cells with various TROY expression levels (GBM8-high TROY; GBM43-moderate TROY; GBM22-low/no TROY). Our intracranial PDX experiments showed that PPF treatment alone did not increase survival in all PDX cells. The combination of PPF and TMZ treatment did provide a survival benefit (p < 0.039) relative to TMZ alone (only in GBM8-high TROY and GBM43-moderate TROY) that was partially lost when treatment was discontinued. However, continuous PPF administration following a concomitant PPF and TMZ treatment course led to extended survival (p < 0.0015) compared to TMZ alone resulting in increased DNA damage (γH2AX) and apoptotic markers (Cleaved Caspase-3). Immunohistochemical analyses showed that TROY expression was decreased in tumors treated with PPF. In addition, PPF-treated tumors showed a differential myeloid population with well circumscribed tumors as compared to control-treated or TMZ-treated tumors. Thus, our data demonstrates that PPF may provide a pharmacological approach to targeting TROY concomitant with standard-of-care to increase patient survival. Citation Format: Ryan Eghlimi, David Nascari, Angad Beniwal, Drake Alton, Dustin Grief, Joseph Loftus, Melanie Haluska, David Coleman, Nhan Tran. Propentofylline enhances GBM sensitivity to temozolomide via targeting TROY signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5905.

Abstract Glioblastoma remains difficult to treat with immunotherapy due to the immunosuppressive tumor microenvironment and the ability of glioma cells to invade diffusely into normal brain parenchyma. While it is known that glioblastoma-associated myeloid cells (GAMs) comprise a large proportion of the tumor microenvironment and can suppress adaptive and innate immune responses through various mechanisms, detailed mapping of myeloid lineages in glioblastoma is still missing. Further characterization of pro-tumoral myeloid-lineages in glioblastoma is important for identifying myeloid-based drug targets that may synergize with T cell-based therapies and produce a more meaningful anti-tumor immune response. Towards this end, we examined numerous scRNAseq datasets derived from glioblastoma patients and identified expression of TNFRSF12A, the gene encoding the TNF- family receptor, Fn14, in a subset of GAMs enriched for expression of cytokines such as CCL3, CCL5, IL-6, and IL-8. This result is intriguing since TWEAK (TNFSF12), the ligand for Fn14, is abundantly expressed within numerous patient-derived glioblastoma cell lines, namely GBM6, GBM8, GBM22, and GBM39. To validate Fn14 protein expression in GAMs, we isolated murine bone-marrow derived macrophages and treated them with glioma-conditioned media, which induced Fn14 gene expression. We then conducted in vitro experiments utilizing the human microglia line HMC3, the murine microglia line SIM-A9, and primary murine bone-marrow-derived macrophages to assess the effects of Fn14 activation in myeloid cells. We found that treatment of Fn14+ myeloid cells with TWEAK ligand upregulates CCL3, CCL5, IL-6, and IL-8 expression. We tested the conditioned media generated from TWEAK-treated Fn14+ myeloid cell lines and found that it promotes glioblastoma invasion in a CCL5-dependent manner. This aligns with previous reports demonstrating the CCL5-CCR5 signaling in glioma cells promotes invasion through calcium-dependent matrix metalloproteinase 2. To assess the spatial distribution of this myeloid subpopulation, we performed RNAscope hybridization against AIF1, TMEM119, CCR5, CCL5, and Fn14 transcripts on sections of murine gliomas generated using the RCAS/tv-a model of human glioblastoma. We found an abundance of Fn14+ plus AIF1+ as well as Fn14+plus TMEM119+ myeloid cells throughout the tumor core and rim of murine tumors and identified CCL5 expression in pseudo-palisades bordering necrotic regions. Our results to date suggest that Fn14 expression in GAMs can promote the invasion of tumor cells into normal brain parenchyma by release of CCL5. Currently, we are utilizing orthotopic patient-derived xenograft models co-implanted with Fn14+/- myeloid cells to test the hypothesis that TWEAK-Fn14 signaling in GAMs provides strong pro-tumoral signals in the glioblastoma microenvironment. Citation Format: Angad Beniwal, Matthew Dufault, Pranjali Kanvinde, David Nascari, Ryan Eghlimi, Adarsha Malla, Dolores Hambardzumyan, Henrique Borges da Silva, Graeme Woodworth, Jeffrey Winkles, Nhan Tran. TWEAK-Fn14 signaling in glioblastoma-associated myeloid cells promotes tumor invasion via CCL5-CCR5 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6867.