Biology subjects

Harter, P. N.

Publications and source records attributed to Harter, P. N..

9 recordsLinked to original sources

bioRxiv2026

Human cerebral assembloids as a model to study the interaction of glioblastoma with resident glial cells

Glioblastoma (GB) is a highly invasive brain cancer characterized by extensive peritumoral glial reactivity. Although GB infiltration and recurrence remain major therapeutic challenges, the contribution of GB-induced gliosis to tumor progression is poorly understood. To investigate glia-GB interactions, we developed human iPSC-derived cerebral forebrain assembloids containing innate microglia and macroglia and transplanted them with GB cells. The model recapitulates key tumor features observed in patients, including distinct tumor regions, reactive gliosis, and altered tissue stiffness. Single-cell RNA sequencing revealed an unexpected enrichment of extracellular vesicles (EVs) in peritumoral reactive glia, which we validated in patient samples. EV inhibition impaired formation of the peritumoral niche, whereas EVs from GB-containing assembloids induced glial reactivity in GB-free assembloids. Furthermore, the modularity of our system enables incorporation of additional niche components, such as monocytes, allowing investigation of the monocyte-glia-tumor axis and providing a powerful platform to dissect mechanisms regulating the GB microenvironment.

neuroscience↗

bioRxiv2025

Decoding the immune response in leptomeningeal disease through single-cell sequencing of cerebrospinal fluid

AbstractAssessing anti-tumor immune responses and immune microenvironments in central nervous system (CNS) neoplasms, such as brain tumors and leptomeningeal disease (LMD), provides prognostic insights and predictive biomarkers. Liquid biopsy of the cerebrospinal fluid (CSF) represents a promising minimally-invasive approach, but its ability to reflect immune responses against tumors remains unclear. Here, we used single-cell sequencing of CSF cells and spatial transcriptomics of CNS lesions to compare and contrast LMD patients with CNS lymphoma (CNSL), glioblastoma (GB) and brain metastases (BrM), to neuroinflammatory CNS disorders. We identified disease-specific CSF environments, reflecting parenchymal tumor microenvironment features. CNSL showed robust T cell responses, while BrM and GB were dominated by both blood-derived and tissue-resident myeloid cells. Longitudinal CSF sampling unveiled mechanisms of disease progression and therapy resistance, highlighting the potential of CSF liquid biopsies for uncovering disease biology, discovering cellular biomarkers and developing personalized therapies for CNS neoplasms.

immunology↗

bioRxiv2024

Modulation of the ATP-adenosine signaling axis combined with radiotherapy facilitates anti-cancer immunity in brain metastasis

The immunosuppressive microenvironment in the brain poses a major limitation to successful therapy for brain metastases. Here we report that blockade of the ATP-to-adenosine-converting enzymes CD39 and CD73 and the adenosine receptor A2AR in combination with radiotherapy attenuates tumor progression in a breast-to-brain metastasis model by facilitating anti-cancer immunity. Immunophenotyping revealed loss of exhausted T cells and higher abundance of anti-cancer effector T cell populations. This effect was accompanied by a decrease of immunosuppressive lipid-laden macrophages and an expansion of CD14CD33high macrophages associated with antigen presentation. Analyses of human brain metastases samples supports a role of the ATP-adenosine signaling axis in modulating tumor inflammation and identified expression of CD39 and adenosine deaminase as predictive markers for patient survival and/or immune infiltration. Our findings demonstrate that the adenosine axis represents a druggable pathway to achieve local immunomodulation and treatment response, opening a new therapeutic avenue for brain metastases patients.

cancer biology↗

bioRxiv2023

Epigenetic neural glioblastoma enhances synaptic integration and predicts therapeutic vulnerability

Neural-tumor interactions drive glioma growth as evidenced in preclinical models, but clinical validation is nascent. We present an epigenetically defined neural signature of glioblastoma that independently affects patients survival. We use reference signatures of neural cells to deconvolve tumor DNA and classify samples into low- or high-neural tumors. High-neural glioblastomas exhibit hypomethylated CpG sites and upregulation of genes associated with synaptic integration. Single-cell transcriptomic analysis reveals high abundance of stem cell-like malignant cells classified as oligodendrocyte precursor and neural precursor cell-like in high-neural glioblastoma. High-neural glioblastoma cells engender neuron-to-glioma synapse formation in vitro and in vivo and show an unfavorable survival after xenografting. In patients, a high-neural signature associates with decreased survival as well as increased functional connectivity and can be detected via DNA analytes and brain-derived neurotrophic factor in plasma. Our study presents an epigenetically defined malignant neural signature in high-grade gliomas that is prognostically relevant.

neuroscience↗

bioRxiv2023

Clinically relevant concurrent BRAF and MEK inhibition alters differentiation states and sensitizes BRAF V600E-mutated high-grade gliomas to immune checkpoint blockade

Resistance to BRAF plus MEK inhibition (BRAFi+MEKi) in BRAFV600E-mutant gliomas drives rebound, progression, and high mortality, yet it remains poorly understood. This study addresses the urgent need to develop treatments for BRAFi+MEKi-resistant glioma in novel mouse models and patient-derived materials. BRAFi+MEKi reveals glioma plasticity by heightening cell state transitions along glial differentiation trajectories, giving rise to astrocyte- and immunomodulatory oligodendrocyte (OL)-like states. PD-L1 upregulation in OL-like cells links cell state transitions to tumor evasion, possibly orchestrated by Galectin-3. BRAFi+MEKi induces interferon response signatures, tumor infiltration, and suppression of T cells. Combining BRAFi+MEKi with immune checkpoint inhibition enhances survival in a T cell-dependent manner, reinvigorates T cells, and outperforms individual or sequential therapies in mice. Elevated PD-L1 expression in BRAF-mutant versus BRAF-wildtype glioblastoma supports the rationale for PD-1 inhibition in patients. These findings underscore the potential of targeting glioma plasticity and highlight combination strategies to overcome therapy resistance in BRAFV600E-mutant HGG. In briefXing et al. show that combined BRAF and MEK inhibitor (BRAFi+MEKi) treatment induces cell state transitions in BRAFV600E-mutant high-grade glioma cells linked with programmed death-ligand (PD-L1) upregulation and T cell suppression, potentially orchestrated through the secretion of galectin-3. These tumor-intrinsic adaptations may be overcome by concurrent immune checkpoint inhibition (ICI), as demonstrated in murine studies, offering novel therapeutic opportunities. HighlightsO_LIBRAFV600E-mutant HGG exhibits cell plasticity induced by BRAFi+MEKi, which links cell state transitions towards glial differentiation with immune evasion C_LIO_LIBRAFi+MEKi enhances anti-tumor immunity and simultaneously suppresses T cells via PD-L1 upregulation C_LIO_LIBRAF-mutant glioblastoma has elevated PD-L1 expression compared to BRAF-wildtype counterparts, providing a criterion for PD-1 inhibition therapy C_LIO_LIConcurrent BRAFi+MEKi and immune checkpoint inhibition enhance T cell-mediated anti-tumor activity and boost survival more effectively than sequential treatment in mice, guiding clinical translation C_LI

cancer biology↗

bioRxiv2022

AMP-kinase mediates adaptation of glioblastoma cells to conditions of the tumour microenvironment

AMP-activated protein kinase (AMPK) is a central cellular energy sensor that regulates metabolic activity. We hypothesised that in glioblastoma (GB), AMPK plays a pivotal role in balancing metabolism under conditions of the tumour microenvironment, which is characterised by fluctuating and often low nutrient and oxygen availability. Impairment of this network could thus interfere with tumour progression. AMPK activity was modulated genetically by CRISPR/Cas9-based double knockout (DKO) of the catalytic 1 and 2 subunits in human GB cells and effects were confirmed by pharmacological AMPK inhibition using BAY3827 and an inactive control compound in primary GB cell lines. We found that metabolic adaptation of GB cells under energy stress conditions (hypoxia, glucose deprivation) was dependent on AMPK and accordingly that, AMPK DKO cells were more vulnerable to glucose-deprivation or inhibition of glycolysis and sensitised to hypoxia-induced cell death. This effect was rescued by reexpression of the AMPK 2 subunit. Similar results were observed using the selective pharmacological AMPK inhibitor BAY3827. Mitochondrial biogenesis was regulated AMPK-dependently with a reduced mitochondrial mass and mitochondrial membrane potential in AMPK DKO GB cells. In vivo, AMPK DKO GB cells showed impaired tumour growth and tumour formation in CAM assays as well as in an orthotopic glioma mouse model. Our study highlights the importance of AMPK for GB cell adaptation towards energy depletion and emphasises the role of AMPK for tumour formation in vivo. Moreover, we identified mitochondria as central downstream effectors of AMPK signalling. The development of AMPK inhibitors could open opportunities for the treatment of hypoxic tumours.

cancer biology↗

bioRxiv2021

Compensatory CSF2-driven macrophage activation promotes adaptive resistance to CSF1R inhibition in breast-to-brain metastasis

Tumor microenvironment-targeted therapies are emerging as promising treatment options for different cancer types. Tumor-associated macrophages and microglia (TAMs) represent an abundant non-malignant cell type in brain metastases and have been proposed to modulate metastatic colonization and outgrowth. We used an inhibitor of colony stimulating factor 1 receptor (CSF1R) to target TAMs at distinct stages of the metastatic cascade in preclinical breast-to-brain metastasis models and found that CSF1R inhibition leads to anti-tumor responses in prevention and intervention trials. However, in established brain metastases, compensatory CSF2Rb-STAT5-mediated pro-inflammatory TAM activation blunted the ultimate efficacy of CSF1R inhibition by inducing neuro-inflammation gene signatures in association with wound repair responses that fostered tumor recurrence. Consequently, combined blockade of CSF1R and STAT5 signaling led to sustained tumor control, a normalization of microglial activation states and amelioration of neuronal damage.

cancer biology↗

bioRxiv2021

Recurrent fusions in PLAGL1 define a distinct subset of pediatric-type supratentorial ependymoma

Ependymomas encompass a heterogeneous group of central nervous system (CNS) neoplasms that occur along the entire neuroaxis. In recent years, extensive (epi-)genomic profiling efforts have identified several molecular groups of ependymoma that are characterized by distinct molecular alterations and/or patterns. Based on unsupervised visualization of a large cohort of genome-wide DNA methylation data, we identified a highly distinct group of pediatric-type tumors (n = 40) forming a cluster separate from all established CNS tumor types, of which a high proportion were histopathologically diagnosed as ependymoma. RNA sequencing revealed recurrent fusions involving the pleomorphic adenoma gene-like 1 (PLAGL1) gene in 19 of 20 of the samples analyzed, with the most common fusion being EWSR1:PLAGL1 (n = 13). Five tumors showed a PLAGL1:FOXO1 fusion and one a PLAGL1:EP300 fusion. High transcript levels of PLAGL1 were noted in these tumors, with concurrent overexpression of the imprinted genes H19 and IGF2, which are regulated by PLAGL1. Histopathological review of cases with sufficient material (n = 16) demonstrated a broad morphological spectrum of largely ependymoma-like tumors. Immunohistochemically, tumors were GFAP-positive and OLIG2- and SOX10-negative. In 3/16 of the cases, a dot-like positivity for EMA was detected. Consistent with other fusion-positive ependymal groups, all tumors in our series were located in the supratentorial compartment. Median age of the patients at the time of diagnosis was 6.2 years. Analysis of time to progression or recurrence revealed survival times comparable to those of patients with ZFTA:RELA-fused ependymoma. In summary, our findings suggest the existence of a novel group of supratentorial ependymomas that are characterized by recurrent PLAGL1 fusions and enriched for pediatric patients.

cancer biology↗

bioRxiv2020

A subset of pediatric thalamic gliomas share a distinct DNA methylation profile, H3K27me3 loss and frequent alteration of EGFR

BackgroundMalignant astrocytic gliomas in children show a remarkable biological and clinical diversity. Small in-frame insertions or missense mutations in the EGFR gene have recently been identified in a distinct subset of pediatric bithalamic gliomas with a unique DNA methylation pattern. MethodsHere, we investigated an epigenetically homogeneous cohort of malignant gliomas (n=58) distinct from other subtypes and enriched for pediatric cases and thalamic location, in order to elucidate the overlap with this recently identified subtype of pediatric bithalamic gliomas. ResultsEGFR gene amplification was detected in 16/58 (27%) tumors, and missense mutations or small in-frame insertions in EGFR were found in 20/30 tumors with available sequencing data (67%; five of them co-occurring with EGFR amplification). Additionally, eight of the 30 tumors (27%) harbored an H3.1 or H3.3 K27M mutation (six of them with a concomitant EGFR alteration). All tumors tested showed loss of H3K27me3 staining, with evidence of EZHIP overexpression in the H3 wildtype cases. Although some tumors indeed showed a bithalamic growth pattern, a significant proportion of tumors occurred in the unilateral thalamus or in other (predominantly midline) locations. ConclusionsOur findings present a distinct molecular class of pediatric malignant gliomas largely overlapping with the recently reported bithalamic gliomas characterized by EGFR alteration, but additionally showing a broader spectrum of EGFR alterations and tumor localization. Global H3K27me3 loss in this group appears to be mediated by either H3 K27 mutation or EZHIP overexpression. EGFR inhibition may represent a potential therapeutic strategy in these highly aggressive gliomas. Key pointsO_LIThis study confirms a distinct new subset of pediatric diffuse midline glioma with H3K27me3 loss, with or without H3 K27 mutation C_LIO_LIThe poor outcome of these tumors is in line with the broader family of pediatric diffuse midline gliomas with H3 K27 mutation or EZHIP overexpression C_LIO_LIFrequent EGFR alterations in these tumors may represent a therapeutic target in this subset C_LI Importance of the StudyMalignant astrocytic gliomas in children show a remarkable biological and clinical diversity. Here, we highlight a distinct molecular class of pediatric malignant gliomas characterized by EGFR alteration and global H3K27me3 loss that appears to be mediated by either H3 K27 mutation or EZHIP overexpression. EGFR inhibition may represent a potential therapeutic strategy in these highly aggressive gliomas.

cancer biology↗