Biology subjects

Gershon, T. R.

Publications and source records attributed to Gershon, T. R..

9 recordsLinked to original sources

bioRxiv2026

Nanoparticle-delivered resiquimod induces brain tumor regression in medulloblastoma and diffuse midline glioma models by interrupting paracrine growth support and activating myeloid immune signaling and phagocytosis

In pediatric brain tumors medulloblastoma (MB) and diffuse midline glioma (DMG), tumor-associated myeloid cells (TAMs) support malignant progression by secreting paracrine growth factors and suppressing local immune function. We studied the potential for reversing this cancer-supportive phenotype by stimulating TAM pathogen receptors using ResiPOx, a brain-permeant, polyoxazoline nanoparticle formulation of the TLR7/8 agonist resiquimod. ResiPOx showed blood-brain barrier penetration and anti-tumor efficacy, extending progression-free survival (PFS) in mice with MB and DMG. Integrated cellular and molecular analysis including scRNA-seq showed that ResiPOx expanded TAM populations and reprogrammed TAMs toward anti-tumoral states, blocking paracrine IGF1 signaling and inducing local cytokine signaling and phagocytosis of tumor cells. In rhesus macaques, systemic ResiPOx was well tolerated and induced brain transcriptional patterns that resembled ResiPOx responses in DMG and MB mouse models, indicating effects in non-human primates that highlight translational potential. Our data show that ResiPOx reshapes the brain tumor microenvironment to inhibit tumor growth. As a systemically administered, brain penetrant immunomodulator, ResiPOx is able to reach multifocal and unresectable brain tumors, including MB and DMG.

cancer biology↗

bioRxiv2022

PRC2 disruption in cerebellar progenitors produces cerebellar hypoplasia and aberrant myoid differentiation without blocking medulloblastoma growth

We show that the Polycomb Repressive Complex 2 (PRC2) maintains neural identity in Sonic Hedgehog (SHH)-driven cerebellar granule neuron progenitors (CGNPs) and SHH-driven medulloblastoma, a cancer of CGNPs. Proliferating CGNPs and medulloblastoma cells pass the neural fate commitment to their progeny through epigenetic mechanisms. The PRC2 mediates epigenetic regulation through histone methylation, and PRC2 inhibitors have been proposed for medulloblastoma therapy. We investigated PRC2 function in CGNPs and medulloblastoma by conditionally deleting PRC2 components Eed or Ezh2 in CGNPs and analyzing cerebellar growth, cellular gene expression (scRNA-seq), and tumorigenesis in medulloblastoma-prone Smo-mutant mice. Eed-deleted CGNPs showed reduced growth, with decreased proliferation, increased apoptosis and inappropriate myoid differentiation. Ezh2-deleted CGNPs also showed myoid differentiation without reduced growth. Eed-deleted and Ezh2-deleted medulloblastomas similarly demonstrated myoid differentiation, but progressed more rapidly than PRC2-intact controls. The PRC2 thus maintained neural fate in CGNPs and medulloblastoma, but PRC2 disruption did not block SHH medulloblastoma progression.

neuroscience↗

bioRxiv2022

Targeting OLIG2 increases therapeutic responses in SHH medulloblastoma mouse models and patient-derived medulloblastoma organoids

Recurrence after therapy is the primary life-threatening complication of medulloblastoma. In Sonic Hedgehog (SHH)-subgroup medulloblastoma, OLIG2-expressing tumour stem cells are crucial to recurrence. We investigated the potential of the small-molecule OLIG2 inhibitor CT-179 to decrease recurrence in patient-derived organoids, mice genetically-engineered to develop SHH-driven MB, and mice with MB patient-derived xenograft (PDX) tumours. We found that OLIG2 mRNA significantly correlated with poor survival in patients with SHH-MB, but not other subgroups. CT-179 rapidly downregulated OLIG2 protein in vitro and displayed nanomolar IC50 values. CT-179 arrested MB cells at G2/M, with degradation of cyclin B1 and phospho-CDK1 inducing apoptosis. In vivo CT-179 induced similar cell cycle changes in MBs in Smo-mutant mice and significantly increased mouse survival. In both MB organoids and mouse models, CT-179 combined with radiotherapy showed greater efficacy than either treatment alone. These data highlight the potential for OLIG2-targeted therapy to improve MB outcomes by targeting recurrent disease.

cancer biology↗

bioRxiv2021

Chronic AMPK inactivation slows SHH medulloblastoma progression by inhibiting mTORC1 signaling and depleting tumor stem cell populations

We show that inactivating AMPK in vivo in a genetic model of medulloblastoma depletes tumor stem cell populations and slows tumor progression. Medulloblastoma, the most common malignant pediatric brain tumor, grows as heterogenous communities comprising diverse types of tumor and stromal cells. Previously, we showed that different populations in medulloblastomas show different sensitivities to specific targeted therapies. To determine if specific populations depend on AMPK, we analyzed mice with AMPK-inactivated medulloblastomas. We engineered mice with conditional deletion of the AMPK catalytic subunits Prkaa1 and Prkaa2 and conditional expression SmoM2, an oncogenic Smo allele that hyperactivates Sonic Hedgehog (SHH) signaling. We compared these medulloblastomas to SmoM2-driven medulloblastomas in AMPK-intact mice. AMPK-inactivation slowed tumor growth and progression, allowing longer event-free survival (EFS). scRNA-seq showed that AMPK inactivation altered cellular heterogeneity, increasing differentiation, decreasing tumor stem cell populations and reducing glio-neuronal multipotency. Surprisingly, AMPK-inactivated tumors showed decreased mTORC1 activation and Hk2 expression. Genetic Hk2 deletion in SmoM2-medulloblastomas similarly decreased stem cell populations, implicating reduced aerobic glycolysis in the tumor-suppressive effect of AMPK inactivation. Our results show that AMPK inactivation impairs tumor growth through mechanisms that disproportionately affect tumor stem cell populations that have proved refractory to conventional therapies.

cancer biology↗

bioRxiv2021

Nanoparticle-delivered palbociclib enable CDK4/6 inhibitor therapy while combination with mTORC1 inhibitor sapanisertib induces long term benefits in SHH medulloblastoma.

CDK4/6 inhibitors hold promise for brain tumor treatment, but efficacy has been limited by recurrence in both preclinical models and clinical trials. To address recurrence, we tested a nanoparticle formulation of the CDK4/6 inhibitor palbociclib (POx-palbo) in mice genetically-engineered to develop SHH-driven medulloblastoma. We then analyzed medulloblastomas in mice receiving palbociclib treatment, and compared the efficacy of combining palbociclib with specific inhibitors suggested by our analysis. POx-Palbo showed reduced toxicity compared to conventional palbociclib, was tolerable in parenteral administration, improved CNS pharmacokinetics, and extended survival of mice with medulloblastoma. Recurrence, however, remained problematic as fractions of tumor cells proliferated during therapy. ScRNA-seq identified a gene expression pattern unique to proliferating medulloblastoma cells in POx-Palbo-treated mice, marked by up-regulation of the glutamate transporter Slc1a2 and down-regulation of diverse ribosomal genes. Reduced mTORC1 signaling, suggested by ribosomal suppression in POx-Palbo-treated tumors was confirmed by decreased 4EBP1 phosphorylation (p4EBP1). Further reducing mTORC1 activity by combining POx-Palbo with the mTORC1 inhibitor sapanisertib produced mutually enhancing effects, with increased suppression of both pRB and p4EBP1, and prolonged mouse survival compared to either agent alone. In contrast, targeting cell cycle progression by combining POx-Palbo with the SHH-pathway inhibitor vismodegib, or with the replication-targeting agents gemcitabine or etoposide, failed to enhance efficacy. Our data show the potential of nanoparticle formulation and scRNA-seq analysis of resistance to improve brain tumor treatment, and identify POx-palbo plus sapanisertib as effective combinatorial therapy for SHH medulloblastoma. This combination may be appropriate for testing in patients with recurrence, who need new options.

cancer biology↗

bioRxiv2020

Leukodystrophy resembling Vanishing White Matter Disease is recapitulated by brain-specific depletion of apoptosis regulator MCL-1

Neurologic disorders often disproportionately affect specific brain regions, and different apoptotic mechanisms may contribute to white matter pathology in leukodystrophies or gray matter pathology in poliodystrophies. We previously showed that neural progenitors that generate cerebellar gray matter depend on the anti-apoptotic protein BCL-xL. Conditional deletion of Bcl-xL in these progenitors produces spontaneous apoptosis and cerebellar hypoplasia, while similar conditional deletion of Mcl-1 produces no phenotype. Here, we show that, in contrast, postnatal oligodendrocytes depend on MCL-1. We found that brain-wide Mcl-1 deletion caused apoptosis specifically in mature oligodendrocytes while sparing astrocytes and oligodendrocyte precursors, resulting in impaired myelination and progressive white matter degeneration. Disabling apoptosis through co-deletion of Bax or Bak rescued white matter degeneration, implicating the intrinsic apoptotic pathway in Mcl-1-dependence. Bax and Bak co-deletions rescued different aspects of the Mcl-1-deleted phenotype, demonstrating their discrete roles in white matter stability. MCL-1 protein abundance was reduced in eif2b5-mutant mouse model of the leukodystrophy vanishing white matter disease (VWMD), suggesting the potential for MCL-1 deficiency to contribute to clinical neurologic disease. Our data show that oligodendrocytes require MCL-1 to suppress apoptosis, implicate MCL-1 deficiency in white matter pathology, and suggest apoptosis inhibition as a leukodystrophy therapy.

neuroscience↗

bioRxiv2020

Neoplastic and Immune single cell transcriptomics define subgroup-specific intra-tumoral heterogeneity of childhood medulloblastoma.

Medulloblastoma (MB) is a heterogeneous disease in which neoplastic cells and associated immune cells contribute to disease progression. To better understand cellular heterogeneity in MB we use single-cell RNA sequencing, immunohistochemistry and deconvolution of transcriptomic data to profile neoplastic and immune populations in childhood MB samples. Neoplastic cells cluster primarily according to individual sample of origin which is in part due to the effect of chromosomal copy number gains and losses. Harmony alignment reveals novel MB subgroup/subtype-associated subpopulations that recapitulate neurodevelopmental processes and are associated with clinical outcomes, including discrete photoreceptor-like cells in MB subgroups GP3 and GP4 and nodule-associated neuronally-differentiated cells in subgroup SHH. We definitively chart the spectrum of MB immune cell infiltrates, which include subgroup/subtype-associated developmentally-related neuron-pruning and antigen presenting myeloid cells. MB cellular diversity is recapitulated in genetically engineered mouse subgroup-specific models of MB. These findings provide a clearer understanding of both the neoplastic and immune cell heterogeneity in MB.

cancer biology↗

bioRxiv2020

Poly(2-oxazoline) nanoparticle delivery enhances the therapeutic potential of vismodegib for medulloblastoma by improving CNS pharmacokinetics and reducing systemic toxicity

We report a novel, nanoparticle formulation of the SHH pathway inhibitor vismodegib that improves efficacy for medulloblastoma treatment while reducing toxicity. Systemic therapies for brain tumors are complicated by restricted blood-brain barrier (BBB) permeability and dose-limiting extraneural toxicity, therefore improved delivery approached are needed. Here we show how a nanoparticle delivery system addresses these obstacles, bringing new efficacy to previously ineffective therapy. Vismodegib has been a promising agent for patients with SHH- subgroup medulloblastoma and is FDA-approved for basal cell carcinoma. However, vismodegib has limited benefit for patients with SHH-driven medulloblastoma, due to off-target toxicities and the development of resistance during therapy. We encapsulated vismodegib in polyoxazoline block copolymer micelles (POx-vismo). We then evaluated POx-vismo using transgenic mice engineered to develop endogenous medulloblastomas, testing the novel agent in a preclinical model with native vasculature and tumor microenvironment. POx-vismo showed improved CNS pharmacokinetics and reduced systemic and bone toxicity. Mechanistic studies show that POx nanoparticles did not enter the CNS, but rather acted within the vascular compartment to improve drug delivery by decreasing drug binding to serum proteins and reducing the volume of distribution. POx-vismo demonstrated improved efficacy, extending the survival of medulloblastoma-bearing mice. Our results show the potential for a simple, non-targeted nanoparticle formulation to improve systemic brain tumor therapy, and specifically to enhance vismodegib therapy for SHH-driven cancers.

neuroscience↗

bioRxiv2020

Content and performance of the MiniMUGA genotyping array, a new tool to improve rigor and reproducibility in mouse research

The laboratory mouse is the most widely used animal model for biomedical research, due in part to its well annotated genome, wealth of genetic resources and the ability to precisely manipulate its genome. Despite the importance of genetics for mouse research, genetic quality control (QC) is not standardized, in part due to the lack of cost effective, informative and robust platforms. Genotyping arrays are standard tools for mouse research and remain an attractive alternative even in the era of high-throughput whole genome sequencing. Here we describe the content and performance of a new Mouse Universal Genotyping Array (MUGA). MiniMUGA, an array-based genetic QC platform with over 11,000 probes. In addition to robust discrimination between most classical and wild-derived laboratory strains, MiniMUGA was designed to contain features not available in other platforms: 1) chromosomal sex determination, 2) discrimination between substrains from multiple commercial vendors, 3) diagnostic SNPs for popular laboratory strains, 4) detection of constructs used in genetically engineered mice, and 5) an easy to interpret report summarizing these results. In-depth annotation of all probes should facilitate custom analyses by individual researchers. To determine the performance of MiniMUGA we genotyped 6,899 samples from a wide variety of genetic backgrounds. The performance of MiniMUGA compares favorably with three previous iterations of the MUGA family of arrays both in discrimination capabilities and robustness. We have generated publicly available consensus genotypes for 241 inbred strains including classical, wild-derived and recombinant inbred lines. Here we also report the detection of a substantial number of XO and XXY individuals across a variety of sample types, the extension of the utility of reduced complexity crosses to genetic backgrounds other than C57BL/6, and the robust detection of 17 genetic constructs. There is preliminary but striking evidence that the array can be used to identify both partial sex chromosome duplication and mosaicism, and that diagnostic SNPs can be used to determine how long inbred mice have been bred independently from the main stock for a significant action of the genotyped inbred samples. We conclude that MiniMUGA is a valuable platform for genetic QC and important new tool to the increase rigor and reproducibility of mouse research.

genetics↗